Spherical acoustic holography was utilized to reconstruct the interior sound field of an enclosed space with vibrating boundaries using an open spherical microphone array. The interior sound fields of vibrating shells, including a pulsating shell, a [Formula: see text]-axis oriented oscillating shell, a partially vibrating shell and a point-excited vibrating shell, were reconstructed, and numerical simulations were carried out to examine the impact of reconstruction parameters, the radius of the microphone array, the number of microphones, the distribution of microphones on the array surface, the wave number, the number of basis functions used, and the radius of the reconstruction surface on the accuracy of reconstruction. In order to minimize the error of reconstruction caused by a variety of factors and uncertainties, such as the measurement noise, regularization treatments were introduced into the process of reconstructing, to suppress the divergent trends of the reconstruction error along with the increase of the wave number and the increase of the radius of the reconstruction surface. Results showed that a Tikhonov regularization method with generalized cross validation (GCV) could yield the least error of reconstruction among the investigated regularization methods.
This paper presents the results of numerical study on reconstruction of acoustic pressure field based on near-field acoustic holography (NAH) with spherical array, while standoff distance, diameter of spherical array, number of microphones vary respectively. Two acoustic pressure fields are analytically generated by two monopole sound sources on the opposite sides of spherical array, and on one side of spherical array but apart at small distance. The accuracy of localization and identification of sound sources at different frequencies with different setup of reconstruction parameters was examined by comparison of the reconstructed results to the analytical results. The simulation of reconstruction of acoustic pressure field based on NAH with spherical array may provide guideline for application of NAH with spherical array in engineering.
This paper conducts in‐depth research on the sound source localization technology of the microphone array and designs a sound source localization system based on the cube microphone array. Firstly, the sound source localization model is established using the cube microphone array combined with the spherical near‐field acoustic holography. Secondly, the numerical and sound source localization simulations are carried out using the spherical wave. Finally, the simulation and experiment of sound source location for sound at 100, 1000, and 2000 Hz are carried out using the model. Both simulation and experimental results show that when the sound source frequency is 100 and 1000 Hz, the location of the sound source can be accurately located by using the sound source localization model of a cube microphone array, and the sound field reconstruction error is low. When the sound source frequency is 2000 Hz, the location of the sound source cannot be located, and the sound field reconstruction error is very high, which will cause the misjudgment of the sound source location.
Choosing an effective spherical numerical integration method is one of the key problems in reconstruction of incident sound field by using spherical microphone array based on spherical near-field acoustic holography (SNAH). Many different spherical numerical integration methods are reported, such as I.H.Sloan, Spherical-t design, J.Fliege, etc., each method applies different distributions of discrete positions and integral weights in the design of spherical microphone array. In the paper, the accuracies of sound pressure reconstruction results based on SNAH with different spherical numerical integration methods are examined and compared. It is found that spherical-t integration method can provide more options of discrete points, simple algorithmic due to equal weight of each point, and the same or higher precision of sound pressure reconstruction. Meanwhile, the expansion terms of reconstructed sound pressure has to be truncated at an optimal number in order to minimize the impact of spherical numerical integration error, the approach to choosing the optimal truncated term number with respect of the number of microphones in spherical numerical integration is discussed in details.
This paper presents the results of an experimental study on the methodology of spherical near-field acoustic holography (spherical NAH) to reconstruct interior sound field. The experiment was carried out in a full anechoic chamber, in which the sound filed was generated with different combination of speakers at different positions, a rigid spherical array was used to collect the field acoustic pressures as input to the reconstruction calculation. There are three cases which were investigated. Case 1, a source was set near to the microphone array. Case 2, two sources were eccentrically set opposite to each other around the microphone array. And Case 3, two sources were placed on one side of microphone array on the same orbit, while they were positioned apart at a small angle. The accuracy of the reconstruction of sound field was examined and analyzed compared to the benchmarks and the results of the numerical simulations. The reconstructed results show that the methodology of Spherical NAH is capable to locate sources and reconstruct sound field within certain accuracy.
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