Phonoscopy: An acoustical holography technique for plane structures radiating in enclosed spaces

Abstract

The present paper provides a modification of near-field acoustical holography (NAH) enabling reconstruction of sound fields in a room in order to study plane structures radiating in enclosed spaces; the new technique is called phonoscopy. A description of the measurement laboratory is given; a single microphone scanner is used to measure the pressure on the hologram plane. Three examples of measurement are presented: a point source located on a rigid wall, a homogeneous wall, and a window mounted in a wall. Maps of the velocity of the structure and of the acoustic intensity radiated are given. The accuracy of phonoscopy is demonstrated by comparison with the accelerometer methods (for measuring vibration velocities) and the two-microphone technique (for measuring acoustic intensities). Some K-space spectra are also presented and analyzed, giving more information about the physics of the vibrator.

Predicting the Acoustical Radiation of Finite Size Multi-Layered Structures by Applying Spatial Windowing on Infinite Structures

“…sin , ) can then be obtained from this normal particle velocity in exactly the same way as the power (k N , ) radiated by the windowed structure was obtained in section 2.2 from the #exural velocity of the structure; equations (5) and (6) can be used and DGLGRC \ GLA (k ? sin , ) can be expressed as (16) and equation (14) becomes…”

Use of a reciprocity technique to measure the radiation efficiency of a vibrating structure

“…However, in terms of characterising sound sources and measuring sound power from operating machinery, international standards are focussed on direct techniques such as the free field method [1], the reverberation room method [2] and the sound intensity method [3]. Other important established direct techniques to measure the acoustic intensity vector field, and therefore to quantify acoustic power, are the Nearfield Acoustic Holography (NAH) [19] and its extension to sound radiated in an enclosed environment, named Phonoscopy [20]. These techniques are largely employed in applications aimed at localising noise sources and they can provide a high degree of accuracy.…”

Data extrapolation method for near-field acoustic holography

“…The NAH has been applicable for the study of structural vibration and scattering. [2][3][4][5] A conventional holography suffer from the defect that the spatial resolution of a reconstructed image depends on a wavelength of radiation.…”