Reconstructing transient acoustic radiation from an arbitrary object with a uniform surface velocity distribution

Abstract

This paper presents the general formulations for reconstructing the transient acoustic field generated by an arbitrary object with a uniformly distributed surface velocity in free space. These formulations are derived from the Kirchhoff-Helmholtz integral theory that correlates the transient acoustic pressure at any field point to those on the source surface. For a class of acoustic radiation problems involving an arbitrarily oscillating object with a uniformly distributed surface velocity, for example, a loudspeaker membrane, the normal surface velocity is frequency dependent but is spatially invariant. Accordingly, the surface acoustic pressure is expressible as the product of the surface velocity and the quantity that can be solved explicitly by using the Kirchhoff-Helmholtz integral equation. This surface acoustic pressure can be correlated to the field acoustic pressure using the Kirchhoff-Helmholtz integral formulation. Consequently, it is possible to use nearfield acoustic holography to reconstruct acoustic quantities in entire three-dimensional space based on a single set of acoustic pressure measurements taken in the near field of the target object. Examples of applying these formulations to reconstructing the transient acoustic pressure fields produced by various arbitrary objects are demonstrated.

A new application for reverberation tanks: measurement of underwater impulsive sound characteristics

“…Historically, researchers have been more concerned about steady state sounds than impulsive sounds emanating from underwater vehicles. Until now, the study of impulsive sound has focused mainly on the detection of signals [1,2], noise elimination [3], or the sound fields radiated by impulsive sources [4][5][6], but due to a lack of methods, few studies have undertaken quantitative measurements. In order to better understand the impulsive acoustic characteristics of underwater vehicles, a method for the quantitative measurement of impulsive sound is proposed in this paper.…”

Instantaneous Bayesian regularization applied to real-time near-field acoustic holography

“…Extensions of NAH have been proposed to address such cases. [2][3][4][5][6][7][8] As standard NAH is usually computed for a single frequency and then devoted to stationary sources, "Time domain holography" 2 was proposed for non-stationary sources: it consists of repeating NAH procedure on each spectral line and then applying the inverse Fourier transform to reconstruct a time evolution of sound field by an inverse Fourier transform. The process is well-adapted to short periods of time with limited bandwidth.…”

“…Wu further explored this approach and recently proposed a novel method to characterize transient sources radiated by arbitrary shapes. 7 The inverse propagator is determined in the frequency domain either by the boundary element method or by the Helmholtz equation least squares. With the aid of the residue theorem, the inverse Fourier transform is calculated to obtain the time kernels.…”