Acoustic Performance of Fence Panels: Comparison Between Single Sheet and Sandwich Panels with Polyurethane Core

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Nóbrega, José Augusto Gomes Neto, Tatiany M. Lucas, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7973535/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract This study analyzed the acoustic performance of two wall systems with a polyurethane core: the single-layer panel system and the sandwich panel system. The research included laboratory measurements to determine the sound reduction index (Rw) of the single-layer system, which obtained a value of Rw(C; Ctr) = 25(-3;-4) dB, and the prediction of acoustic performance for the sandwich panel system, which showed a predicted value of Rw(C; Ctr) = 45(-2;-8) dB. The results showed that the sandwich panel system provided 80% better acoustic performance compared to the single-layer system, offering greater sound insulation capacity. Furthermore, the sandwich panel system better meets the reference indices established by NBR 15575-4, which addresses the requirements for vertical wall systems, both internal and external. This study contributes to the development of more efficient solutions for noise control in commercial buildings based on accurate measurements and predictions of acoustic performance. To support specification and compliance with ABNT NBR 15575-4 under real operating conditions, future work should include in-situ measurements and flanking transmission assessments to validate the predicted airborne sound insulation. Sealing panels Sandwich panels Polyurethane Acoustic performance Sound insulation Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. Introduction Energy efficiency and thermal comfort are central aspects in construction, as they are directly related to cost reduction, well-being and thermal-acoustic adaptation, especially in commercial and industrial buildings, which face high costs due to the energy consumption associated with air conditioning. In this context, choosing suitable sealing materials is crucial in improving thermal and acoustic performance and reducing operating costs (Capão 2018 ). Traditionally, in addition to using ceramic blocks in conventional masonry, precast concrete panels have been widely used due to their durability and high mechanical strength. However, these systems have limitations, particularly in hot climate regions such as northeastern Brazil, where thermal efficiency is essential to reduce energy consumption. (Capão 2018 ) Despite the advantages of the concrete panel system, such as its ability to withstand great stress and its durability, there are also some limitations, especially when it comes to the CO₂ emissions emitted by cement production, given that the cement industry globally accounts for around 7% of all carbon dioxide emitted by humans, contributing significantly to climate change (Oliveira 2019 ). In addition, manufacturing and transporting these panels can result in significant logistical costs, especially in regions far from production centres. Furthermore, the acoustic performance of traditional Brazilian masonry, such as ceramic and concrete blocks, is often insufficient to meet acoustic performance requirements. The Brazilian standard NBR 15575-4 (2021) sets standards for acoustic efficiency requirements, suggesting that these walls should meet specific sound reduction index (R𝑤) limits of a minimum of 33 dB for heavy systems and 35 dB for light systems for blind wall between a housing unit and the common areas of occasional traffic, and a maximum of 48 dB for heavy systems and 50 dB for light systems for walls between autonomous housing units if at least one of the rooms is a bedroom, or for blind walls between the bedroom or living room of a housing unit and common areas where people stay. According to Rezende et al. ( 2014 ), ceramic block walls have a level of 38 dB and concrete blocks of 41 dB, which do not fully meet the required parameters. Therefore, as an alternative, implementing isothermal panels composed of polyurethane (PUR) cores has offered excellent acoustic insulation, agility in installation and cost reduction on the construction site (Moura 2018 ). These construction solutions align with sustainability requirements, contributing to energy savings and minimizing negative environmental impacts.The use of sandwich panels is an alternative, being implemented in buildings to serve for acoustic insulation and sealing; they are formed by a single piece organized in three layers, configuring themselves as strong and rigid materials, and their faces are resistant to bending, wind, corrosion and fire (Glória 2015 ). According to Garcia (2019), sandwich panels have excellent mechanical properties and are suitable for use as a sealing system, with good efficiency in terms of their acoustic characteristics. As for double panels, they basically consist of a composite structure of sheets coated with metallic material with a polyurethane (PUR) core and an empty space between them (Drăghici et al. 2023 ). With this in mind, methods capable of minimizing environmental impacts while proposing efficient and economical solutions are essential for viable execution possibilities. Thus, this study analyses the PUR panel construction system, emphasising the sound reduction index (Rw), considering a spacing of 2.5 cm for the double panel system. The research evaluates its efficiency, acoustic performance, and potential benefits for Brazil's construction sector. 2. Materials and methods 2.1 PUR sandwich panels The isothermal panels under study, shown in Fig. 1 , comprise two primary materials: steel sheets and polyurethane. The sheets, which were pre-painted with anti-corrosion paint, form the external faces of the panel, covering the core to guarantee the durability and resistance of the final product. In addition, the panel's core, which was 50mm thick, was filled with rigid PUR foam, a polymer that performs well as a thermal and acoustic insulator. In addition, the aim was to use a construction system that not only guarantees water tightness and sealing but also allows the slabs to move due to temperature variations. Two types of joints were used: one horizontally and the other vertically, as shown in Fig. 2 . Horizontally, sealing fittings were used, designed to simulate the effect of a drip pan, and fixed with screws to ensure an effective joint. Figure 3 shows a detailed view of the horizontal fitting. On the other hand, an aluminum profile was installed in the vertical direction, with a cover between the panels and embedding the fixings. The details of the vertical splice can be seen in Fig. 4 . The dimensions of the panels can vary according to the layout of each project, but in this case, there is a maximum length of ten meters and a maximum span between supports of between 3300 and 4500 millimetres. It was also found that the panel model studied has a self-weight ranging from 10.21 to 13.70 kg/m². 2.2 Double panels Double polyurethane (PUR) panels are a variation of traditional sandwich panels, incorporating a 2.5 cm thick air cavity between two layers of PUR core panels. This configuration results in a total thickness of 12.5 cm to optimize acoustic performance, as illustrated in Fig. 5 . Figure 5 shows the structural difference between the two types of panels, highlighting the air cavity present in the double panel (Fig. 5 b), which improves acoustic performance compared to the conventional sandwich panel (Fig. 5 a). By adding the air cavity, this construction system significantly improves acoustic insulation since the air layer acts as a barrier to sound propagation, hindering the transmission of acoustic waves through the panel (Bagattini 2023 ). The acoustic efficiency of double PUR panels depends on the interaction between the materials and the geometric configuration of the system. As a porous material, the air cavity plays a key role in reducing the amount of acoustic energy passing through the panel structure (Zhao et al. 2024 ). This system helps to minimize sound propagation, providing superior acoustic insulation compared to conventional sandwich panels. Several factors influence the acoustic performance of double panels, with the thickness of the air cavity being one of the most critical. Very small cavities may not effectively reduce sound, while excessively large cavities can generate natural convection, impairing the effectiveness of the insulation (Proença et al. 2024 ). In this study, a thickness of 2.5 cm was chosen for the air cavity to obtain satisfactory acoustic performance within the project conditions and ensure the system's effectiveness without compromising thermal and structural stability. 2.3 Measuring the sound reduction index for the sandwich panel The ISO 717-1 standard was adopted as the reference methodology for conducting sound insulation tests to determine the sound reduction index (𝑅𝑤). This test is conducted in a reverberant chamber, where the panel is subjected to different sound frequencies in order to assess its ability to insulate against airborne noise (ISO 717-1, 2019). During the test, the panel's sound insulation is compared to a standard reference curve, which covers insulation values for frequency ranges between 100 Hz and 3150 Hz, divided into one-third octave bands. The procedure consists of adjusting the reference curve along the measured spectrum until the sum of the unfavourable deviations (cases where the measured insulation falls below the reference) does not exceed 32 dB or the average of these deviations is less than 2 dB, as shown in Table 1 . Table 1 Third-octave band reference values for Rw analysis (Adapted from ISO 717-1 2019) Frequency (Hz) Reference values (dB) One-third octave bands 100 33 125 36 160 39 200 42 250 45 315 48 400 51 500 52 630 53 800 54 1000 55 1250 56 1600 56 2000 56 2500 56 3150 56 This adjustment provides a single 𝑅𝑤 value, quantifying the sound reduction capacity of the thermoacoustic panels. In order to complement the acoustic conductivity analysis, the 𝐶 (Pink Noise Correction Factor) correction spectrum was determined, which is used to represent medium and high-frequency noises, such as air traffic sounds, as well as the 𝐶𝑡𝑟 (Traffic Noise Correction Factor) spectrum, aimed at low-frequency noise, such as urban road traffic sounds, both in accordance with the recommendations of ISO 717-1, which defines specific adjustments to the sound reduction index in order to adapt it to different environmental noise conditions. These correction spectra are applied by subtracting the value of the correction spectrum from the measured sound insulation test results for each frequency, thus adjusting the final 𝑅𝑤 value to reflect the material's performance in different noise conditions. The following table shows the correction values used for each frequency range. Table 2 Sound level spectra for calculating adaptation terms (Adapted from ISO 717-1 2019) Frequency (Hz) Sound levels, L_(i,j) (Db) Spectrum No. 1 for calculating C Spectrum #2 for calculating Ctr A third of an octave 100 -29 -20 125 -26 -20 160 -23 -18 200 -21 -16 250 -19 -15 315 -17 -14 400 -15 -13 500 -13 -12 630 -12 -11 800 -11 -9 1000 -10 -8 1250 -9 -9 Based on the information obtained experimentally, it is essential to compare it with the reference parameters established by NBR 15575-4 (ABNT 2021), which determines the acoustic performance criteria for validating thermoacoustic panels. The standard specifies minimum requirements for various applications, such as 45dB for partitions between residential units without bedrooms and 50dB for those with bedrooms. For the panel to be considered valid, the measured Rw must meet or exceed these values, and it is classified into minimum, intermediate or superior performance categories. Table 3 shows the Rw reference values for lightweight systems (systems with a surface density of less than 60 kg/m/²) for different architectural elements. Table 3 Reference values, Rw, for airborne noise insulation of internal vertical seals - Minimum performance level (Adapted from NBR 15575-4 2021) Elements Rw (Lightweight systems) dB The wall between independent living units in situations where there is no sleeping area. ≥ 45 The wall between independent living units if there is at least one bedroom. ≥ 50 Blind walls in dormitories between a dwelling unit and common areas with occasional traffic, such as corridors and staircases on the floors. ≥ 45 Blind wall between a dwelling unit and common areas where traffic may occur, such as corridors and stairwells, in situations where there is no sleeping area. ≥ 35 Blind wall between the bedroom or living room of a housing unit and the common areas for people to stay, leisure activities and sports activities. ≥ 30 2.3 Empirical approach to predicting the sound reduction index for the double panel To estimate the acoustic performance of sealing systems based on double panels, the empirical approach developed by Sharp ( 1978 ) was used, which is widely recognized for dealing with the limitations of acoustic insulation at lower frequencies. This method is particularly effective for modelling resonant behaviour in double-panel walls and allows for approximate transmission loss (TL) prediction. The approach considers three critical frequencies: (i) the lowest-order acoustic resonance, (ii) the lowest-order structural resonance and (iii) a limiting frequency related to the gap between the panels. The lowest-order acoustic resonance is calculated by Eq. 1 : $$\:{f}_{a}=\frac{c}{2L}$$ 1 Where c is the speed of sound in air and L is the largest dimension of the cavity. The lowest-order structural resonance is due to mass-air-mass resonance; the enclosed air acts as a spring, and the panels are the masses. For an air-filled cavity, this frequency can be approximated by Eq. 2 : $$\:{f}_{r}=\frac{1}{2\pi\:}\cdot\:\sqrt{\frac{\rho\:c²}{d{M}_{eff}{\prime\:}}}$$ 2 Where ρ is the air density, d is the distance between the internal surfaces, and M_eff is the effective mass per unit area of the two panels, calculated as M_eff= (M_1 + M_2)〖^(-1)〗 as the panels are the same and have the same mass, M_1 = M_2, representing the mass per unit area of each panel. Finally, the limit frequency fl is related to the width of the gap between the panels as shown in Eq. 3 : $$\:{f}_{l}=\frac{c}{2\pi\:d}$$ 3 Where c is the speed of sound in air and L is the cavity's largest dimension, corresponding to 2.5 cm in this study. The lowest-order structural resonance is due to mass-air-mass resonance; the enclosed air acts as a spring, and the panels are the masses. $$\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:20log\left[\left({M}_{1}+{M}_{2}\right)f\right]-47,\:f\le\:{f}_{r}$$ $$\:Tl\:=\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:T{L}_{1}+T{L}_{2}+20log\left(fd\right)-29,\:{f}_{r}<f<{f}_{l}$$ 4 $$\:\:\:\:\:\:\:\:\:\:T{L}_{1}+T{L}_{2}+6-K,\:f\ge\:{f}_{l}$$ Where TL_1 and TL_2 are the transmission losses for each leaf of the double wall measured or calculated separately, the coefficient K depends on the sound-absorbing material placed in the air cavity between the two leaves. If the cavity is empty, K is calculated as K = 10log(1 + 2/α), where α is the average sound absorption coefficient of the panel surfaces. This coefficient K considers the absorption material's effect in reducing the sound passing through the wall (Crocker and Arenas 2021 ). 3. Results 3.1 Sound reduction index Table 4 shows the results obtained for the sound reduction index of the single-ply panels, measured according to the frequencies standardized by ISO 717-7 2021. The Rw values were recorded for a frequency range of 100 Hz to 5000 Hz, as shown below. Table 4 Rw analysis results according to ISO 717-7 standard frequencies Frequency (Hz) Measured Rw (dB) One-third octave bands 100 14,6 125 17,1 160 16,4 200 17,6 250 20,1 315 21,3 400 23,4 500 24,5 630 25,6 800 25,6 1000 23,4 1250 14,3 1600 24,2 2000 39,3 2500 47 3150 53,5 4000 53,4 5000 47,7 Based on the data in Table 4 , an illustrative graph was drawn up to facilitate the interpretation of the results, as shown in Fig. 6 . The curve generated from the data reflects the distribution of the sound reduction index over the different frequencies. Based on the sound reduction curve shown in Fig. 6 and in accordance with the criteria of the ISO 717-1 standard (2021), the Rw value obtained for the thermoacoustic panels was 25 dB. To complement the analysis, the adaptation coefficients for airborne noise (C = -3) and traffic noise (Ctr = -4) were calculated according to the values shown in Table 2 of topic 2.2, which describe the sound level spectra and the adaptation terms to be applied. Although the results show an average sound reduction of 25 dB, the performance of the single-ply panels did not meet the requirements established by NBR 15575-4 (2021) for some situations. Specifically, for the blind walls between a housing unit's bedroom or living room and the common areas for people to stay, leisure activities and sports activities, the minimum value required for Rw is 30 dB, 20% higher than the value obtained in the laboratory. In addition, for the walls between autonomous housing units in situations where there is no sleeping environment and for the blind walls of dormitories between housing units and common areas of occasional traffic (such as corridors and staircases), the minimum value required for Rw is 45 dB. In contrast, the measured value was lower than that required. These results indicate that the panels analyzed do not meet the acoustic performance requirements demanded by the standard for some situations of acoustic comfort in residential buildings. The difference between the measured values and the required values may imply that adjustments need to be made to the composition or construction system of the panels to ensure compliance with the sound reduction standards for certain types of environments. 3.2 Sound reduction index for the double panel Table 5 below shows the estimated Rw values for the double panels, measured as a function of the frequencies standardized by ISO 717-7 2021. The Rw values were recorded for a frequency range of 100 Hz to 3150 Hz. Table 5 Rw prediction results as a function of the frequencies standardized in ISO 717-7 Frequency (Hz) Estimated Rw (dB) One-third octave bands 100 21,77 125 23,71 160 25,85 200 28,51 250 34,33 315 40,35 400 46,58 500 52,39 630 58,41 800 64,64 1000 70,45 1250 76,27 1600 82,70 2000 88,51 2500 76,34 3150 80,35 Based on the data in the Table, a graph was generated to illustrate the sound reduction index (Rw) distribution over the different frequencies, as shown in Fig. 7 . The curve generated reveals an increasing performance of the material as the frequency increases, with significant peaks between 1000 Hz and 2000 Hz. This suggests that the double-type panel is particularly effective at attenuating higher frequencies, typical of urban noise and indoor environments. The estimated Rw value for the double panels was 45 dB, as calculated by the curve shown in Fig. 7 . The system resulted in an 80% increase in the Rw value when compared to the value obtained for the sandwich panels (25 dB), as discussed in section 3.1 . This difference of 20 dB shows that the double panels offer greater sound insulation capacity, especially for medium and high frequencies, which is advantageous for environments where noise control is a priority, such as residential and commercial areas. Comparing the values obtained, it can be seen that the double panel, with an estimated Rw of 45 dB, perfectly meets the minimum requirements of NBR 15575-4 (2021) for walls between autonomous housing units (without a bedroom) and blind walls of bedrooms between a housing unit and common areas of occasional transit (such as corridors and staircases), both of which require Rw ≥ 45 dB. In addition, the performance of the double panel exceeds the requirements for blind walls between a bedroom/living room and common areas for living, leisure or sport, which require an Rw ≥ 30 dB. Therefore, for these applications, it provides a higher acoustic performance than required. On the other hand, for situations in which NBR 15575-4 requires Rw ≥ 50 dB (such as for the walls between autonomous housing units with at least one bedroom), the double panel still does not reach the minimum value, falling short by 5 dB. This suggests that in certain acoustically demanding scenarios, such as quieter residential environments, it may be necessary to use higher-performance systems, such as thicker panels or hybrid systems. In summary, double panels with a 2.5 cm gap between the sandwich panels demonstrate superior acoustic efficiency compared to single-ply panels, meeting or exceeding the requirements of NBR 15575-4 (2021) in several situations, except for the most demanding, where an additional reduction in Rw would be necessary to ensure maximum acoustic comfort. 4. Conclusions This study analyzed the acoustic performance of two different sealing systems: sandwich panels with a polyurethane (PUR) core and a double system consisting of two sandwich panels separated by a 2.5 cm gap. The evaluation was based on the sound reduction index (Rw), according to the criteria established by ISO standard 717-1 (2021), and the results were compared to the requirements of NBR 15575-4 (2021). The results showed that the single-sheet panels had lower acoustic performance than the requirements of NBR 15575-4 (2021) for various acoustic comfort situations, such as walls between housing units and blind walls between bedrooms and common areas. The Rw value obtained for these panels was 25 dB, which does not meet the minimum requirements for environments with high noise levels. On the other hand, the double panels showed superior acoustic performance, with a sound reduction index of 45 dB. This value met the requirements of NBR 15575-4 (2021) for various situations, such as walls between autonomous housing units and blind walls between bedrooms and common areas with occasional traffic. The greatest efficiency was observed at medium and high frequencies. However, for situations with requirements higher than 50 dB, such as walls between residential units with bedrooms, the double panels have not yet reached the necessary values, suggesting that, for these conditions, solutions with greater thickness or hybrid systems may be more suitable. Declarations The authors declare that they have no competing interests. The datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request. Authorship Contribution Statement The authors contributed systematically to the design and preparation of the study, as described below: Vinicius da Silva Vieira Conceptualization, Investigation, Methodology, Writing-original draft, Writing-review & editing. Aline Figueiredo da Nóbrega Supervision, Validation, Project administration & review. José Augusto Gomes Neto : Tatiany Macedo Lucas Data curation, Formal analysis, Writing-original draft, Writing-review & editing. Leonardo Seixas Pessoa da Silva Supervision, Validation, Project administration & review. Potential reviewers Full names and email addresses of at least three potential reviewers: João Ramoa Correia Email: [email protected] Pedro Gil Girão dos Santos Email: [email protected] Luís Manuel Cortesão Godinho Email: [email protected] The suggested reviewers were selected as they are referenced in the work, reflecting their relevance and expertise in the research area addressed in the article. Author Contribution The authors contributed systematically to the design and preparation of the study, as described below:**Vinicius da Silva Vieira:** Conceptualization, Investigation, Methodology, Writing-original draft, Writing-review & editing.**Aline Figueiredo da Nóbrega:** Supervision, Validation, Project administration & review.**José Augusto Gomes Neto:****Tatiany Macedo Lucas:** Data curation, Formal analysis, Writing-original draft, Writing-review & editing.**Leonardo Seixas Pessoa da Silva:** Supervision, Validation, Project administration & review. Data Availability The datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request. References ABNT – ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS (2021) NBR ISO 717-1: Acústica – Classificação de Isolamento Acústico em Edificações e Elementos de Edificações – Parte 1: Isolamento a Ruído Aéreo. ABNT – ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS (2021) NBR 15575-4: Edificações habitacionais — Desempenho Parte 4: Requisitos para os sistemas de vedações verticais internas e externas — SVVIE. 5 ed. Bagattini BA (2023) Perda de transmissão sonora em painel duplo de metamaterial. 97 f. Dissertação (Mestrado) - Curso de Faculdade de Engenharia Mecânica, Universidade Estadual de Campinas. Capão JCS (2018) Desenvolvimento de parede interior modular em painel sandwich com núcleo em XPS. https://core.ac.uk/download/pdf/231952986.pdf. Accessed on 16 December 2024. Crocker MJ, Arenas, JP (2021) Engineering acoustics: noise and vibration control. John Wiley & Sons. Drăghici et al. (2023) Use of PIR/PUR sandwich panels as advanced materials in industrial constructions. https://revista-constructii.univ-ovidius.ro/wp-content/uploads/2024/02/10641-Volume25_Issue_1-07_paper.pdf. Accessed on December 16, 2024. García ADCM (2019) Desenvolvimento de um sistema construtivo com painéis sanduíches para habitações de baixa renda. https://tede.ufam.edu.br/handle/tede/7798. Accessed on 14 December 2024. Glória M (2015) Desenvolvimento e caracterização de painéis sanduíches de concreto com núcleo leve e faces em laminados reforçados com fibras longas de sisal. Dissertation - Universidade Federal do Rio de Janeiro. Moura VS (2018) Fabricação de painéis isotérmicos. Anápolis-GO, Isoeste, http://repositorio.aee.edu.br/bitstream/aee/861/1/20182_TCC_Caio_Mariana.pdf. Accessed on October 24, 2024. Oliveira MGF (2019) Roadmap tecnológico do cimento. Brasília: [s.n.], https://coprocessamento.org.br/wpcontent/uploads/2019/11/Roadmap_Tecnologico_Cimento_Brasil_Book-1.pdf. Accessed on 23 October 2024. Proença M et al. (2024) Acoustic behaviour of GFRP-PUR web-core composite sandwich panels. Construction And Building Materials, [S.L.], v. 438, p. 137-195, Elsevier BV. http://dx.doi.org/10.1016/j.conbuildmat.2024.137195. Rezende et al (2014) O desempenho acústico segundo a norma de desempenho ABNT NBR 15.575 isolamento sonoro contra ruído aéreo de vedações verticais internas medido em campo. Sharp, BH (1978) A study of techniques to increase the sound insulation of building elements. U.S. Dept. of Housing and Urban Development, Washington DC, 1978. NTIS PB222 829/4. Noise Control Engineering Journal, v. 11, n. 2, p. 53-63. Zhao A et al. (2024) Design and verifications of three building acoustic metamaterials for simultaneous noise insulation and ventilation. Construction And Building Materials, [S.L.], v. 456, p. 139316, Elsevier BV. http://dx.doi.org/10.1016/j.conbuildmat.2024.139316. Additional Declarations No competing interests reported. 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Nóbrega","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABC0lEQVRIiWNgGAWjYDACdsYGBgYbBgYDMK/iAJg68ACfFmaQljSYljMHGHhAWhLwagERMC2MbRAtDPi08Dcztz34kHBHzlz68OEXP+fdkbMXO/wQaIudnG4Ddi0ShxnbDWckPDO27EtLs+zd9syYRzrNAKgl2djsAA5rDjO2SfP+OJy44QyPmQHvtsOJPdIJIC0HErfh0CIP0vInAaSF/5vh3zkgLekf8GoxAGlhAGvhYX7M2wDSkoPfFkOgFsmehMPGlj1sZswyxw4b89zOKTiQYIDbL3LH259J/Eg4LGcOtOTjm5rDcuyz0zd/+FBhJ4fT+0iATQLJwYSVgwDzB+LUjYJRMApGwUgDAPLuZSKBWHMBAAAAAElFTkSuQmCC","orcid":"","institution":"Federal University of Campina Grande","correspondingAuthor":true,"prefix":"","firstName":"Aline","middleName":"F.","lastName":"Nóbrega","suffix":""},{"id":539191559,"identity":"bfacc117-e320-4bc2-8971-ccdee9e4d084","order_by":2,"name":"José Augusto Gomes Neto","email":"","orcid":"","institution":"Federal University of Paraíba","correspondingAuthor":false,"prefix":"","firstName":"José","middleName":"Augusto Gomes","lastName":"Neto","suffix":""},{"id":539191560,"identity":"9a9b0099-cdb4-4bc4-9365-d088ddf370b4","order_by":3,"name":"Tatiany M. Lucas","email":"","orcid":"","institution":"Federal University of Campina Grande","correspondingAuthor":false,"prefix":"","firstName":"Tatiany","middleName":"M.","lastName":"Lucas","suffix":""},{"id":539191561,"identity":"67ea0ffd-124a-4c45-b4cd-1f916a7d73fc","order_by":4,"name":"Leonardo S. P. Silva","email":"","orcid":"","institution":"LS Building Partners Corp: Kissimmee","correspondingAuthor":false,"prefix":"","firstName":"Leonardo","middleName":"S. P.","lastName":"Silva","suffix":""}],"badges":[],"createdAt":"2025-10-28 20:08:19","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7973535/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7973535/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":95096406,"identity":"fead8573-3ad0-4961-9ef5-94de0d673431","added_by":"auto","created_at":"2025-11-04 09:25:29","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":275936,"visible":true,"origin":"","legend":"\u003cp\u003eIsothermal panels with pre-painted steel sheets and polyurethane core (Isoeste 2016)\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7973535/v1/fc9dda07fe59280993c22a7a.png"},{"id":95096409,"identity":"e40cbfa8-0187-4925-a2a1-13b326754594","added_by":"auto","created_at":"2025-11-04 09:25:30","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":232385,"visible":true,"origin":"","legend":"\u003cp\u003eVertical and horizontal plate joints (Isoeste 2016)\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7973535/v1/f9691eb805becbbf46fcec49.png"},{"id":95096407,"identity":"3ccc5b0d-e0ce-4a9b-bb24-9ee5e7ac8882","added_by":"auto","created_at":"2025-11-04 09:25:30","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":214526,"visible":true,"origin":"","legend":"\u003cp\u003eDetail of the horizontal fitting of the panels (Isoeste 2016)\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7973535/v1/0cdf0f0cabc12358ee397dba.png"},{"id":95096413,"identity":"1b287497-9f51-4343-bfa3-5bff0928a65a","added_by":"auto","created_at":"2025-11-04 09:25:32","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":152495,"visible":true,"origin":"","legend":"\u003cp\u003eDetail of the vertical fitting of the panels (Isoeste, 2016)\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7973535/v1/77d51bd58f828fbdb45d76a7.png"},{"id":95096405,"identity":"8802746a-c4ff-4d3d-950e-d65ce63e43c8","added_by":"auto","created_at":"2025-11-04 09:25:29","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":43937,"visible":true,"origin":"","legend":"\u003cp\u003eComparison between the PUR sandwich panel (a) and the double PUR panel (b)\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7973535/v1/fbd4a0d424941524238ffb04.png"},{"id":95096408,"identity":"a9cfdd91-fa26-4fa8-9a0f-0121dc8c74d2","added_by":"auto","created_at":"2025-11-04 09:25:30","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":83888,"visible":true,"origin":"","legend":"\u003cp\u003eResults of the sound reduction index analysis for the single-ply panel.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-7973535/v1/a15d036be47da37fe90e07ab.png"},{"id":95096412,"identity":"21185335-05f0-4195-8da4-d8602617713d","added_by":"auto","created_at":"2025-11-04 09:25:32","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":77890,"visible":true,"origin":"","legend":"\u003cp\u003eResults of the sound reduction index analysis for the double panel\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-7973535/v1/c57dec3a137c4e3f28efe63e.png"},{"id":95096424,"identity":"5799fb46-5ab9-46dd-9839-12755f8560e2","added_by":"auto","created_at":"2025-11-04 09:25:38","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1896075,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7973535/v1/ab62d252-e575-4c63-aa10-8f9fe5b053a3.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eAcoustic Performance of Fence Panels: Comparison Between Single Sheet and Sandwich Panels with Polyurethane Core\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eEnergy efficiency and thermal comfort are central aspects in construction, as they are directly related to cost reduction, well-being and thermal-acoustic adaptation, especially in commercial and industrial buildings, which face high costs due to the energy consumption associated with air conditioning. In this context, choosing suitable sealing materials is crucial in improving thermal and acoustic performance and reducing operating costs (Cap\u0026atilde;o \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2018\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eTraditionally, in addition to using ceramic blocks in conventional masonry, precast concrete panels have been widely used due to their durability and high mechanical strength. However, these systems have limitations, particularly in hot climate regions such as northeastern Brazil, where thermal efficiency is essential to reduce energy consumption. (Cap\u0026atilde;o \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) Despite the advantages of the concrete panel system, such as its ability to withstand great stress and its durability, there are also some limitations, especially when it comes to the CO₂ emissions emitted by cement production, given that the cement industry globally accounts for around 7% of all carbon dioxide emitted by humans, contributing significantly to climate change (Oliveira \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). In addition, manufacturing and transporting these panels can result in significant logistical costs, especially in regions far from production centres.\u003c/p\u003e\u003cp\u003eFurthermore, the acoustic performance of traditional Brazilian masonry, such as ceramic and concrete blocks, is often insufficient to meet acoustic performance requirements. The Brazilian standard NBR 15575-4 (2021) sets standards for acoustic efficiency requirements, suggesting that these walls should meet specific sound reduction index (R\u0026#119908;) limits of a minimum of 33 dB for heavy systems and 35 dB for light systems for blind wall between a housing unit and the common areas of occasional traffic, and a maximum of 48 dB for heavy systems and 50 dB for light systems for walls between autonomous housing units if at least one of the rooms is a bedroom, or for blind walls between the bedroom or living room of a housing unit and common areas where people stay. According to Rezende et al. (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2014\u003c/span\u003e), ceramic block walls have a level of 38 dB and concrete blocks of 41 dB, which do not fully meet the required parameters.\u003c/p\u003e\u003cp\u003eTherefore, as an alternative, implementing isothermal panels composed of polyurethane (PUR) cores has offered excellent acoustic insulation, agility in installation and cost reduction on the construction site (Moura \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). These construction solutions align with sustainability requirements, contributing to energy savings and minimizing negative environmental impacts.The use of sandwich panels is an alternative, being implemented in buildings to serve for acoustic insulation and sealing; they are formed by a single piece organized in three layers, configuring themselves as strong and rigid materials, and their faces are resistant to bending, wind, corrosion and fire (Gl\u0026oacute;ria \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). According to Garcia (2019), sandwich panels have excellent mechanical properties and are suitable for use as a sealing system, with good efficiency in terms of their acoustic characteristics. As for double panels, they basically consist of a composite structure of sheets coated with metallic material with a polyurethane (PUR) core and an empty space between them (Drăghici et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eWith this in mind, methods capable of minimizing environmental impacts while proposing efficient and economical solutions are essential for viable execution possibilities. Thus, this study analyses the PUR panel construction system, emphasising the sound reduction index (Rw), considering a spacing of 2.5 cm for the double panel system. The research evaluates its efficiency, acoustic performance, and potential benefits for Brazil's construction sector.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 PUR sandwich panels\u003c/h2\u003e\u003cp\u003eThe isothermal panels under study, shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, comprise two primary materials: steel sheets and polyurethane. The sheets, which were pre-painted with anti-corrosion paint, form the external faces of the panel, covering the core to guarantee the durability and resistance of the final product. In addition, the panel's core, which was 50mm thick, was filled with rigid PUR foam, a polymer that performs well as a thermal and acoustic insulator.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIn addition, the aim was to use a construction system that not only guarantees water tightness and sealing but also allows the slabs to move due to temperature variations. Two types of joints were used: one horizontally and the other vertically, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eHorizontally, sealing fittings were used, designed to simulate the effect of a drip pan, and fixed with screws to ensure an effective joint. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows a detailed view of the horizontal fitting.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eOn the other hand, an aluminum profile was installed in the vertical direction, with a cover between the panels and embedding the fixings. The details of the vertical splice can be seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe dimensions of the panels can vary according to the layout of each project, but in this case, there is a maximum length of ten meters and a maximum span between supports of between 3300 and 4500 millimetres.\u003c/p\u003e\u003cp\u003eIt was also found that the panel model studied has a self-weight ranging from 10.21 to 13.70 kg/m\u0026sup2;.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Double panels\u003c/h2\u003e\u003cp\u003eDouble polyurethane (PUR) panels are a variation of traditional sandwich panels, incorporating a 2.5 cm thick air cavity between two layers of PUR core panels. This configuration results in a total thickness of 12.5 cm to optimize acoustic performance, as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e shows the structural difference between the two types of panels, highlighting the air cavity present in the double panel (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb), which improves acoustic performance compared to the conventional sandwich panel (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea). By adding the air cavity, this construction system significantly improves acoustic insulation since the air layer acts as a barrier to sound propagation, hindering the transmission of acoustic waves through the panel (Bagattini \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The acoustic efficiency of double PUR panels depends on the interaction between the materials and the geometric configuration of the system. As a porous material, the air cavity plays a key role in reducing the amount of acoustic energy passing through the panel structure (Zhao et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). This system helps to minimize sound propagation, providing superior acoustic insulation compared to conventional sandwich panels.\u003c/p\u003e\u003cp\u003eSeveral factors influence the acoustic performance of double panels, with the thickness of the air cavity being one of the most critical. Very small cavities may not effectively reduce sound, while excessively large cavities can generate natural convection, impairing the effectiveness of the insulation (Proen\u0026ccedil;a et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). In this study, a thickness of 2.5 cm was chosen for the air cavity to obtain satisfactory acoustic performance within the project conditions and ensure the system's effectiveness without compromising thermal and structural stability.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3 Measuring the sound reduction index for the sandwich panel\u003c/h2\u003e\u003cp\u003eThe ISO 717-1 standard was adopted as the reference methodology for conducting sound insulation tests to determine the sound reduction index (\u0026#119877;\u0026#119908;). This test is conducted in a reverberant chamber, where the panel is subjected to different sound frequencies in order to assess its ability to insulate against airborne noise (ISO 717-1, 2019).\u003c/p\u003e\u003cp\u003eDuring the test, the panel's sound insulation is compared to a standard reference curve, which covers insulation values for frequency ranges between 100 Hz and 3150 Hz, divided into one-third octave bands. The procedure consists of adjusting the reference curve along the measured spectrum until the sum of the unfavourable deviations (cases where the measured insulation falls below the reference) does not exceed 32 dB or the average of these deviations is less than 2 dB, as shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eThird-octave band reference values for Rw analysis\u003c/p\u003e \u003cdiv class=\"Credit\"\u003e\u003cp\u003e(Adapted from ISO 717-1 2019)\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eFrequency (Hz)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eReference values (dB)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eOne-third octave bands\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e100\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e33\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e125\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e36\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e160\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e39\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e200\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e42\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e250\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e45\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e315\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e48\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e400\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e51\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e500\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e52\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e630\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e53\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e800\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e54\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1000\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e55\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1250\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e56\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1600\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e56\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2000\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e56\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2500\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e56\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3150\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e56\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThis adjustment provides a single \u0026#119877;\u0026#119908; value, quantifying the sound reduction capacity of the thermoacoustic panels.\u003c/p\u003e\u003cp\u003eIn order to complement the acoustic conductivity analysis, the \u0026#119862; (Pink Noise Correction Factor) correction spectrum was determined, which is used to represent medium and high-frequency noises, such as air traffic sounds, as well as the \u0026#119862;\u0026#119905;\u0026#119903; (Traffic Noise Correction Factor) spectrum, aimed at low-frequency noise, such as urban road traffic sounds, both in accordance with the recommendations of ISO 717-1, which defines specific adjustments to the sound reduction index in order to adapt it to different environmental noise conditions. These correction spectra are applied by subtracting the value of the correction spectrum from the measured sound insulation test results for each frequency, thus adjusting the final \u0026#119877;\u0026#119908; value to reflect the material's performance in different noise conditions. The following table shows the correction values used for each frequency range.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eSound level spectra for calculating adaptation terms\u003c/p\u003e \u003cdiv class=\"Credit\"\u003e\u003cp\u003e(Adapted from ISO 717-1 2019)\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eFrequency (Hz)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003eSound levels, L_(i,j) (Db)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSpectrum No. 1 for calculating C\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eSpectrum #2 for calculating Ctr\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003eA third of an octave\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e100\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-29\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-20\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e125\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-26\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-20\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e160\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-23\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-18\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e200\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-16\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e250\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-15\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e315\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-17\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-14\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e400\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-13\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e500\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-12\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e630\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-11\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e800\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-9\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1000\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-8\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1250\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e-9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-9\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eBased on the information obtained experimentally, it is essential to compare it with the reference parameters established by NBR 15575-4 (ABNT 2021), which determines the acoustic performance criteria for validating thermoacoustic panels. The standard specifies minimum requirements for various applications, such as 45dB for partitions between residential units without bedrooms and 50dB for those with bedrooms. For the panel to be considered valid, the measured Rw must meet or exceed these values, and it is classified into minimum, intermediate or superior performance categories. Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows the Rw reference values for lightweight systems (systems with a surface density of less than 60 kg/m/\u0026sup2;) for different architectural elements.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eReference values, Rw, for airborne noise insulation of internal vertical seals - Minimum performance level\u003c/p\u003e \u003cdiv class=\"Credit\"\u003e\u003cp\u003e(Adapted from NBR 15575-4 2021)\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eElements\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eRw (Lightweight systems) dB\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eThe wall between independent living units in situations where there is no sleeping area.\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026ge;\u0026thinsp;45\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eThe wall between independent living units if there is at least one bedroom.\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026ge;\u0026thinsp;50\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBlind walls in dormitories between a dwelling unit and common areas with occasional traffic, such as corridors and staircases on the floors.\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026ge;\u0026thinsp;45\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBlind wall between a dwelling unit and common areas where traffic may occur, such as corridors and stairwells, in situations where there is no sleeping area.\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026ge;\u0026thinsp;35\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBlind wall between the bedroom or living room of a housing unit and the common areas for people to stay, leisure activities and sports activities.\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u0026ge;\u0026thinsp;30\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.3 Empirical approach to predicting the sound reduction index for the double panel\u003c/h2\u003e\u003cp\u003eTo estimate the acoustic performance of sealing systems based on double panels, the empirical approach developed by Sharp (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e1978\u003c/span\u003e) was used, which is widely recognized for dealing with the limitations of acoustic insulation at lower frequencies. This method is particularly effective for modelling resonant behaviour in double-panel walls and allows for approximate transmission loss (TL) prediction. The approach considers three critical frequencies: (i) the lowest-order acoustic resonance, (ii) the lowest-order structural resonance and (iii) a limiting frequency related to the gap between the panels. The lowest-order acoustic resonance is calculated by Eq.\u0026nbsp;\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e:\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:{f}_{a}=\\frac{c}{2L}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eWhere c is the speed of sound in air and L is the largest dimension of the cavity. The lowest-order structural resonance is due to mass-air-mass resonance; the enclosed air acts as a spring, and the panels are the masses.\u003c/p\u003e\u003cp\u003eFor an air-filled cavity, this frequency can be approximated by Eq.\u0026nbsp;\u003cspan refid=\"Equ2\" class=\"InternalRef\"\u003e2\u003c/span\u003e:\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:{f}_{r}=\\frac{1}{2\\pi\\:}\\cdot\\:\\sqrt{\\frac{\\rho\\:c\u0026sup2;}{d{M}_{eff}{\\prime\\:}}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eWhere ρ is the air density, d is the distance between the internal surfaces, and M_eff is the effective mass per unit area of the two panels, calculated as M_eff= (M_1\u0026thinsp;+\u0026thinsp;M_2)〖^(-1)〗 as the panels are the same and have the same mass, M_1\u0026thinsp;=\u0026thinsp;M_2, representing the mass per unit area of each panel. Finally, the limit frequency fl is related to the width of the gap between the panels as shown in Eq.\u0026nbsp;\u003cspan refid=\"Equ3\" class=\"InternalRef\"\u003e3\u003c/span\u003e:\u003cdiv id=\"Equ3\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ3\" name=\"EquationSource\"\u003e\n$$\\:{f}_{l}=\\frac{c}{2\\pi\\:d}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e3\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eWhere c is the speed of sound in air and L is the cavity's largest dimension, corresponding to 2.5 cm in this study. The lowest-order structural resonance is due to mass-air-mass resonance; the enclosed air acts as a spring, and the panels are the masses.\u003c/p\u003e\u003cp\u003e\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:20log\\left[\\left({M}_{1}+{M}_{2}\\right)f\\right]-47,\\:f\\le\\:{f}_{r}$$\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equ4\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ4\" name=\"EquationSource\"\u003e\n$$\\:Tl\\:=\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:T{L}_{1}+T{L}_{2}+20log\\left(fd\\right)-29,\\:{f}_{r}\u0026lt;f\u0026lt;{f}_{l}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e4\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:T{L}_{1}+T{L}_{2}+6-K,\\:f\\ge\\:{f}_{l}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eWhere TL_1 and TL_2 are the transmission losses for each leaf of the double wall measured or calculated separately, the coefficient K depends on the sound-absorbing material placed in the air cavity between the two leaves. If the cavity is empty, K is calculated as K\u0026thinsp;=\u0026thinsp;10log(1\u0026thinsp;+\u0026thinsp;2/α), where α is the average sound absorption coefficient of the panel surfaces. This coefficient K considers the absorption material's effect in reducing the sound passing through the wall (Crocker and Arenas \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Sound reduction index\u003c/h2\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows the results obtained for the sound reduction index of the single-ply panels, measured according to the frequencies standardized by ISO 717-7 2021. The Rw values were recorded for a frequency range of 100 Hz to 5000 Hz, as shown below.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eRw analysis results according to ISO 717-7 standard frequencies\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eFrequency\u003c/p\u003e\u003cp\u003e(Hz)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMeasured Rw (dB)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eOne-third octave bands\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e100\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e14,6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e125\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e17,1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e160\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e16,4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e200\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e17,6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e250\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e20,1\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e315\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e21,3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e400\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e23,4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e500\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e24,5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e630\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e25,6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e800\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e25,6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1000\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e23,4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1250\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e14,3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1600\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e24,2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2000\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e39,3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2500\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e47\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3150\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e53,5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4000\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e53,4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e5000\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e47,7\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eBased on the data in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, an illustrative graph was drawn up to facilitate the interpretation of the results, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. The curve generated from the data reflects the distribution of the sound reduction index over the different frequencies.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eBased on the sound reduction curve shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e and in accordance with the criteria of the ISO 717-1 standard (2021), the Rw value obtained for the thermoacoustic panels was 25 dB. To complement the analysis, the adaptation coefficients for airborne noise (C = -3) and traffic noise (Ctr = -4) were calculated according to the values shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e of topic 2.2, which describe the sound level spectra and the adaptation terms to be applied.\u003c/p\u003e\u003cp\u003eAlthough the results show an average sound reduction of 25 dB, the performance of the single-ply panels did not meet the requirements established by NBR 15575-4 (2021) for some situations. Specifically, for the blind walls between a housing unit's bedroom or living room and the common areas for people to stay, leisure activities and sports activities, the minimum value required for Rw is 30 dB, 20% higher than the value obtained in the laboratory. In addition, for the walls between autonomous housing units in situations where there is no sleeping environment and for the blind walls of dormitories between housing units and common areas of occasional traffic (such as corridors and staircases), the minimum value required for Rw is 45 dB. In contrast, the measured value was lower than that required.\u003c/p\u003e\u003cp\u003eThese results indicate that the panels analyzed do not meet the acoustic performance requirements demanded by the standard for some situations of acoustic comfort in residential buildings. The difference between the measured values and the required values may imply that adjustments need to be made to the composition or construction system of the panels to ensure compliance with the sound reduction standards for certain types of environments.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e3.2 Sound reduction index for the double panel\u003c/h2\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e below shows the estimated Rw values for the double panels, measured as a function of the frequencies standardized by ISO 717-7 2021. The Rw values were recorded for a frequency range of 100 Hz to 3150 Hz.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eRw prediction results as a function of the frequencies standardized in ISO 717-7\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eFrequency\u003c/p\u003e\u003cp\u003e(Hz)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eEstimated Rw (dB)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eOne-third octave bands\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e100\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e21,77\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e125\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e23,71\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e160\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e25,85\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e200\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e28,51\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e250\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e34,33\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e315\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e40,35\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e400\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e46,58\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e500\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e52,39\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e630\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e58,41\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e800\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e64,64\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1000\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e70,45\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1250\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e76,27\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1600\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e82,70\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2000\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e88,51\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2500\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e76,34\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3150\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e80,35\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eBased on the data in the Table, a graph was generated to illustrate the sound reduction index (Rw) distribution over the different frequencies, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. The curve generated reveals an increasing performance of the material as the frequency increases, with significant peaks between 1000 Hz and 2000 Hz. This suggests that the double-type panel is particularly effective at attenuating higher frequencies, typical of urban noise and indoor environments.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe estimated Rw value for the double panels was 45 dB, as calculated by the curve shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. The system resulted in an 80% increase in the Rw value when compared to the value obtained for the sandwich panels (25 dB), as discussed in section \u003cspan refid=\"Sec8\" class=\"InternalRef\"\u003e3.1\u003c/span\u003e. This difference of 20 dB shows that the double panels offer greater sound insulation capacity, especially for medium and high frequencies, which is advantageous for environments where noise control is a priority, such as residential and commercial areas.\u003c/p\u003e\u003cp\u003eComparing the values obtained, it can be seen that the double panel, with an estimated Rw of 45 dB, perfectly meets the minimum requirements of NBR 15575-4 (2021) for walls between autonomous housing units (without a bedroom) and blind walls of bedrooms between a housing unit and common areas of occasional transit (such as corridors and staircases), both of which require Rw\u0026thinsp;\u0026ge;\u0026thinsp;45 dB. In addition, the performance of the double panel exceeds the requirements for blind walls between a bedroom/living room and common areas for living, leisure or sport, which require an Rw\u0026thinsp;\u0026ge;\u0026thinsp;30 dB. Therefore, for these applications, it provides a higher acoustic performance than required.\u003c/p\u003e\u003cp\u003eOn the other hand, for situations in which NBR 15575-4 requires Rw\u0026thinsp;\u0026ge;\u0026thinsp;50 dB (such as for the walls between autonomous housing units with at least one bedroom), the double panel still does not reach the minimum value, falling short by 5 dB. This suggests that in certain acoustically demanding scenarios, such as quieter residential environments, it may be necessary to use higher-performance systems, such as thicker panels or hybrid systems. In summary, double panels with a 2.5 cm gap between the sandwich panels demonstrate superior acoustic efficiency compared to single-ply panels, meeting or exceeding the requirements of NBR 15575-4 (2021) in several situations, except for the most demanding, where an additional reduction in Rw would be necessary to ensure maximum acoustic comfort.\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eThis study analyzed the acoustic performance of two different sealing systems: sandwich panels with a polyurethane (PUR) core and a double system consisting of two sandwich panels separated by a 2.5 cm gap. The evaluation was based on the sound reduction index (Rw), according to the criteria established by ISO standard 717-1 (2021), and the results were compared to the requirements of NBR 15575-4 (2021).\u003c/p\u003e\u003cp\u003eThe results showed that the single-sheet panels had lower acoustic performance than the requirements of NBR 15575-4 (2021) for various acoustic comfort situations, such as walls between housing units and blind walls between bedrooms and common areas. The Rw value obtained for these panels was 25 dB, which does not meet the minimum requirements for environments with high noise levels.\u003c/p\u003e\u003cp\u003eOn the other hand, the double panels showed superior acoustic performance, with a sound reduction index of 45 dB. This value met the requirements of NBR 15575-4 (2021) for various situations, such as walls between autonomous housing units and blind walls between bedrooms and common areas with occasional traffic. The greatest efficiency was observed at medium and high frequencies. However, for situations with requirements higher than 50 dB, such as walls between residential units with bedrooms, the double panels have not yet reached the necessary values, suggesting that, for these conditions, solutions with greater thickness or hybrid systems may be more suitable.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003eThe datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthorship Contribution Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors contributed systematically to the design and preparation of the study, as described below:\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eVinicius da Silva Vieira\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConceptualization, Investigation, Methodology, Writing-original draft, Writing-review \u0026amp; editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAline Figueiredo da N\u0026oacute;brega\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSupervision, Validation, Project administration \u0026amp; review.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eJos\u0026eacute; Augusto Gomes Neto\u003c/strong\u003e:\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTatiany Macedo Lucas\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData curation, Formal analysis, Writing-original draft, Writing-review \u0026amp; editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLeonardo Seixas Pessoa da Silva\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSupervision, Validation, Project administration \u0026amp; review.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePotential reviewers\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFull names and email addresses of at least three potential reviewers:\u003c/p\u003e\n\u003col start=\"1\" type=\"1\"\u003e\n \u003cli\u003e\u003cstrong\u003eJo\u0026atilde;o Ramoa Correia\u003cbr\u003e\u003c/strong\u003eEmail: [email protected]\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003ePedro Gil Gir\u0026atilde;o dos Santos\u003cbr\u003e\u003c/strong\u003eEmail: [email protected]\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eLu\u0026iacute;s Manuel Cortes\u0026atilde;o Godinho\u003cbr\u003e\u003c/strong\u003eEmail: [email protected]\u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eThe suggested reviewers were selected as they are referenced in the work, reflecting their relevance and expertise in the research area addressed in the article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors contributed systematically to the design and preparation of the study, as described below:**Vinicius da Silva Vieira:** Conceptualization, Investigation, Methodology, Writing-original draft, Writing-review \u0026amp; editing.**Aline Figueiredo da N\u0026oacute;brega:** Supervision, Validation, Project administration \u0026amp; review.**Jos\u0026eacute; Augusto Gomes Neto:****Tatiany Macedo Lucas:** Data curation, Formal analysis, Writing-original draft, Writing-review \u0026amp; editing.**Leonardo Seixas Pessoa da Silva:** Supervision, Validation, Project administration \u0026amp; review.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003e\u003cstrong\u003eABNT \u0026ndash; ASSOCIA\u0026Ccedil;\u0026Atilde;O BRASILEIRA DE NORMAS T\u0026Eacute;CNICAS (2021)\u003c/strong\u003e NBR ISO 717-1: Ac\u0026uacute;stica \u0026ndash; Classifica\u0026ccedil;\u0026atilde;o de Isolamento Ac\u0026uacute;stico em Edifica\u0026ccedil;\u0026otilde;es e Elementos de Edifica\u0026ccedil;\u0026otilde;es \u0026ndash; Parte 1: Isolamento a Ru\u0026iacute;do A\u0026eacute;reo.\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eABNT \u0026ndash; ASSOCIA\u0026Ccedil;\u0026Atilde;O BRASILEIRA DE NORMAS T\u0026Eacute;CNICAS (2021) \u003c/strong\u003eNBR 15575-4: Edifica\u0026ccedil;\u0026otilde;es habitacionais \u0026mdash; Desempenho Parte 4: Requisitos para os sistemas de veda\u0026ccedil;\u0026otilde;es verticais internas e externas \u0026mdash; SVVIE. 5 ed. \u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eBagattini BA (2023)\u003c/strong\u003e Perda de transmiss\u0026atilde;o sonora em painel duplo de metamaterial. 97 f. Disserta\u0026ccedil;\u0026atilde;o (Mestrado) - Curso de Faculdade de Engenharia Mec\u0026acirc;nica, Universidade Estadual de Campinas.\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eCap\u0026atilde;o JCS (2018)\u003c/strong\u003e Desenvolvimento de parede interior modular em painel sandwich com n\u0026uacute;cleo em XPS. https://core.ac.uk/download/pdf/231952986.pdf. Accessed on 16 December 2024. \u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eCrocker MJ, Arenas, JP (2021)\u003c/strong\u003e Engineering acoustics: noise and vibration control. John Wiley \u0026amp; Sons.\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eDrăghici et al. (2023)\u003c/strong\u003e Use of PIR/PUR sandwich panels as advanced materials in industrial constructions. https://revista-constructii.univ-ovidius.ro/wp-content/uploads/2024/02/10641-Volume25_Issue_1-07_paper.pdf. Accessed on December 16, 2024.\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eGarc\u0026iacute;a ADCM (2019) \u003c/strong\u003eDesenvolvimento de um sistema construtivo com pain\u0026eacute;is sandu\u0026iacute;ches para habita\u0026ccedil;\u0026otilde;es de baixa renda. https://tede.ufam.edu.br/handle/tede/7798. Accessed on 14 December 2024.\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eGl\u0026oacute;ria M (2015)\u003c/strong\u003e Desenvolvimento e caracteriza\u0026ccedil;\u0026atilde;o de pain\u0026eacute;is sandu\u0026iacute;ches de concreto com n\u0026uacute;cleo leve e faces em laminados refor\u0026ccedil;ados com fibras longas de sisal. Dissertation - Universidade Federal do Rio de Janeiro. \u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eMoura VS (2018)\u003c/strong\u003e Fabrica\u0026ccedil;\u0026atilde;o de pain\u0026eacute;is isot\u0026eacute;rmicos. An\u0026aacute;polis-GO, Isoeste, http://repositorio.aee.edu.br/bitstream/aee/861/1/20182_TCC_Caio_Mariana.pdf. Accessed on October 24, 2024.\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eOliveira MGF (2019) \u003c/strong\u003eRoadmap tecnol\u0026oacute;gico do cimento. Bras\u0026iacute;lia: [s.n.], https://coprocessamento.org.br/wpcontent/uploads/2019/11/Roadmap_Tecnologico_Cimento_Brasil_Book-1.pdf. Accessed on 23 October 2024.\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eProen\u0026ccedil;a M et al. (2024) \u003c/strong\u003eAcoustic behaviour of GFRP-PUR web-core composite sandwich panels. Construction And Building Materials, [S.L.], v. 438, p. 137-195, Elsevier BV. http://dx.doi.org/10.1016/j.conbuildmat.2024.137195.\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eRezende et al (2014)\u003c/strong\u003e O desempenho ac\u0026uacute;stico segundo a norma de desempenho ABNT NBR 15.575 isolamento sonoro contra ru\u0026iacute;do a\u0026eacute;reo de veda\u0026ccedil;\u0026otilde;es verticais internas medido em campo. \u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eSharp, BH (1978)\u003c/strong\u003e A study of techniques to increase the sound insulation of building elements. U.S. Dept. of Housing and Urban Development, Washington DC, 1978. NTIS PB222 829/4. Noise Control Engineering Journal, v. 11, n. 2, p. 53-63.\u003c/li\u003e\n\u003cli\u003e\u003cstrong\u003eZhao A et al. (2024)\u003c/strong\u003e Design and verifications of three building acoustic metamaterials for simultaneous noise insulation and ventilation. Construction And Building Materials, [S.L.], v. 456, p. 139316, Elsevier BV. http://dx.doi.org/10.1016/j.conbuildmat.2024.139316.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Sealing panels, Sandwich panels, Polyurethane, Acoustic performance, Sound insulation","lastPublishedDoi":"10.21203/rs.3.rs-7973535/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7973535/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study analyzed the acoustic performance of two wall systems with a polyurethane core: the single-layer panel system and the sandwich panel system. The research included laboratory measurements to determine the sound reduction index (Rw) of the single-layer system, which obtained a value of Rw(C; Ctr)\u0026thinsp;=\u0026thinsp;25(-3;-4) dB, and the prediction of acoustic performance for the sandwich panel system, which showed a predicted value of Rw(C; Ctr)\u0026thinsp;=\u0026thinsp;45(-2;-8) dB. The results showed that the sandwich panel system provided 80% better acoustic performance compared to the single-layer system, offering greater sound insulation capacity. Furthermore, the sandwich panel system better meets the reference indices established by NBR 15575-4, which addresses the requirements for vertical wall systems, both internal and external. This study contributes to the development of more efficient solutions for noise control in commercial buildings based on accurate measurements and predictions of acoustic performance. To support specification and compliance with ABNT NBR 15575-4 under real operating conditions, future work should include in-situ measurements and flanking transmission assessments to validate the predicted airborne sound insulation.\u003c/p\u003e","manuscriptTitle":"Acoustic Performance of Fence Panels: Comparison Between Single Sheet and Sandwich Panels with Polyurethane Core","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-04 09:25:23","doi":"10.21203/rs.3.rs-7973535/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"6d63505c-139f-49f8-a03d-65c37ceb6553","owner":[],"postedDate":"November 4th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-11-04T09:25:23+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-04 09:25:23","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7973535","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7973535","identity":"rs-7973535","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}