High-resolution three-dimensional reconstruction of impulse response by high-speed polarization interferometer

Acousto-optic measurement techniques such as high-speed polarization interferometry using parallel phase-shifting interferometry (PPSI) have been proposed as a method that can accurately capture two-dimensional sound fields. PPSI has recently been applied to measure time stretched pulse (TSP) signal emitted from a loudspeaker to visualize two-dimensional line-integrated impulse response. As a result, the behavior of the impulse response in a two-dimensional plane was accurately confirmed, from which the inherent acoustic characteristics of the loudspeaker could also be analyzed. In this study, the three-dimensional impulse response is visualized spatially by reconstructing the sound field based on a physical model, using TSP signals measured on a two-dimensional plane from multiple directions. We also evaluated the validity of the proposed method by comparing it with a conventional microphone method. The proposed method enabled us to confirm the spatial characteristics of the impulse response without reflections and diffractions that occur in microphone measurements. Therefore, this method has the potential to contribute to improving the accuracy of loudspeaker design and tuning.