Laser-assisted See-through Technology for Locating Sound Sources Inside a Structure

A laser-assisted see-through technology is developed to locate sound sources inside a structure and to analyze the interior sound field. Six lasers were utilized to measure the normal velocities on the exterior surface simultaneously, which were used to locate sound sources inside a structure through a passive sonic detection and ranging algorithm. Next, the Helmholtz equation least squares method was applied to reconstruct the interior sound field, and computer tomography utilized to scan space and time simultaneously to observe the changes of the interior sound field over time. If signals are time invariant, we can do all these with two lasers, one being fixed and another measuring the normal surface velocities and establish the transfer functions with respect to the stationary laser sequentially. This laser-assisted see-through technology was validated experimentally and employed to view the aerodynamically-induced sound field generated by a blower inside a projector. The reason that we can break the barrier in sound source localization is that measurements are taken on an impenetrable surface, whose normal velocity is continuous across the thickness of the surface. This discovery is groundbreaking. It embodies a significant advancement in sound source localization, and opens the door to a class of applications presently unattainable.