Real-Time Nearfield Acoustic Holography: Implementation of the Direct and Inverse Impulse Responses in the Time-Wavenumber Domain

TL;DR

This paper compares various methods for implementing real-time nearfield acoustic holography, focusing on forward and inverse impulse responses in the time-wavenumber domain, to determine the most effective approach for accurate acoustic signal reconstruction.

Contribution

The study evaluates and compares different approaches for constructing impulse responses in real-time nearfield acoustic holography, highlighting the most relevant methods for accurate forward and inverse problem solutions.

Findings

Inverse Fourier transform method performs well in simulations

Direct sampling and low-pass filtering offer alternative impulse response constructions

Wiener inverse filtering improves inverse problem reconstruction accuracy

Abstract

The aim of the study is to demonstrate that some methods are more relevant for implementing the Real-Time Nearfield Acoustic Holography than others. First by focusing on the forward propagation problem, different approaches are compared to build the impulse response to be used. One of them in particular is computed by an inverse Fourier transform applied to the theoretical transfer function for propagation in the frequency-wavenumber domain. Others are obtained by directly sampling an analytical impulse response in the time-wavenumber domain or by additional low-pass filtering. To estimate the performance of each impulse response, a simulation test involving several monopoles excited by non stationary signals is presented and some features are proposed to assess the accuracy of the temporal signals resulting from reconstruction processing on a forward plane. Then several inverse impulse responses used to solve the inverse problem, which consists in back propagating the acoustic signals acquired by the microphone array, are built directly from a transfer function or by using Wiener inverse filtering from the direct impulse responses obtained for the direct problem. Another simulation test is performed to compare the signals reconstructed on the source plane. The same indicators as for the propagation study are used to highlight the differences between the methods tested for solving the Holography inverse problem.