Beamforming based commercial planar microphone array could only localize and identify the sound source when the distance between source and array is known. This paper presents a beamforming based acoustic tomography (BBAT) method to locate and identify the source in 3D space, say, the BBAT method can not only locate the source in X-Y plane that is parallel to the array, but also the depth Z of the source. In this method, the sound field is reconstructed on the virtual planes at different distances along depth direction (Z direction). The maximum response of sound field on every virtual reconstruction plane is tracked, where the largest value among those maximum responses appears at Z direction is the depth of the source. The location of source at X and Y directions can then be easily identified based on beamforming principle, which is utilized by commercial planar array. The BBAT method is evaluated theoretically by simulation of monopole source, the experimental evaluation is done as well in anechoic chamber. The results from both simulation and experiment indicate that this method is capable to locate and identify sound source in 3D space. However, it cannot recognize the sound source located in front of the planar array or behind because of the genetic limitation of 2D planar array in identification of source depth.

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<div class="section abstract"><div class="htmlview paragraph">In the automotive industry, testing the sound absorption coefficient of acoustic materials through reverberation chambers has been widely used. The advantage of this method is that sound waves are incident on the surface of acoustic materials randomly, which is more in line with actual engineering. At present, most of the reverberation chamber design and construction refers to the international standard ISO 354-2003. However, although the design indicators of the reverberation chamber have already met the requirements of the standard ISO 354-2003, there are still some differences between the test results of different reverberation chambers on the same group of samples to be tested, and sometimes the differences are so big they affect the engineering applications. In this paper, the sound absorption coefficients of the same group of samples in different reverberation chambers are tested, and there are some differences in the sound absorption coefficients. Also, the sound absorption coefficients of a variety of samples of different materials in several different reverberation chambers were tested, confirming that there is a phenomenon of poor repeatability of the sound absorption coefficient of the reverberation chamber test. To optimize the poor repeatability of the sound absorption coefficient of the reverberation chamber test, the diffuser in a reverberation chamber is arranged in many different ways. In each reverberation chamber with a different layout, the sound absorption coefficient of the same piece is tested. The diffuser layout of the reverberation chamber was adjusted to the optimal arrangement according to the test results of the sound absorption coefficient. Next, each factor in the testing process of the sound absorption coefficient that may have an impact on the test results is examined separately, and the influencing factors are analyzed. Finally, the optimal test scheme for testing the sound absorption coefficient in the reverberation chamber is given. More importantly, an acceptable margin of error is given regarding the sound absorption coefficient of the reverberation chamber test material.</div></div>