Sound source reconstructions using a microphone array

Abstract

A square microphone array with 256 elements has been constructed along with interfacing electronics to study low-frequency (1–5 kHz) sound sources in air using the principles of acoustical holography. The array is used in the nearfield of a radiating object and the sound source structure of that object is reconstructed with an on-line minicomputer. Reconstruction of the source structure of a point source and an unbaffled, free rectangular plate point excited below its coincidence frequency are presented. The latter shows clear evidence of ’’corner’’ and ’’edge’’ modes in which the respective areas of the plate are the dominant radiating sources. A new imaging process which is not limited in resolution by the wavelength of the radiated sound is introduced.

Imaging of acoustic fields using optical feedback interferometry

“…Reconstruction of the propagation of these acoustic fields can be realised using diverse techniques, such as with microphone arrays (which can interfere with the field being measured) [9], shadowgraphy (which can visualise a field but cannot quantify its pressure) [10], and optical measurement techniques [11][12][13] including laser Doppler vibrometry (LDV) [14][15][16]. Previous work has shown the potential of refracto-vibrometry for imaging of sound propagation in two dimensions (2D) [15].…”

Modelo de Identificación de Fuentes Sonoras. Aplicación al Ruido del Motor de un Automóvil

“…Podemos distinguir principalmente tres métodos: "Sound Intensity" (Crocker, 1983), "Acoustic Holography" (NAH) (Williams, 1980) y "Airborne Source Quantification" (ASQ) (Verheij, 1997).…”

Acoustic source localization exploring theory and practice

“…Contrary to the methods used in optical holography, it can localize acoustic sources which are smaller than a wavelength because it uses a forward model which describes the evanescent waves, which have a short wavelength and decay exponentially with the distance to the source. As stated by Williams [97], the method was originally proposed by Graham in 1969. It has been further developed by Williams, Maynard and others, starting in 1980 [97,45].…”

“…As stated by Williams [97], the method was originally proposed by Graham in 1969. It has been further developed by Williams, Maynard and others, starting in 1980 [97,45]. Similar methods have been developed for cylindrical and spherical coordinate systems and this large body of work was summarized by Williams in 1999 in the reference work Fourier Acoustics [94].…”