A three-dimensional sound intensity measurement system for sound source identification and sound power determination by ln models

Abstract

This paper describes a full vector intensity probe which advances the field of sound intensity and sound source direction estimation using six matched rotating and variable directional microphones. The probe has three pairs of microphones at an equal spacing of 30 mm that are set up in each of the x, y, and z directions and share the same observation point. The calibration method using the rotating microphone system is effective to correct position errors in the y- and z-axes microphone pairs. Sound intensity measurements using the variable directional microphone method can locate with accuracy a sound source, i.e., the structure parts radiating most acoustic energy. The system can find the maximum sound intensity level and beamwidth of the major lobe, and the peak sound intensity levels of the minor lobes. Therefore, a procedure for sound power determination based on minimum measurement data is theoretically and experimentally discussed. Consequently, it is possible to reconstruct only parts of the system emitting the most noise and measure efficiently the sound power level.

Volumetric acoustic vector intensity imager

“…More sophisticated probes are appearing such as the three-axis intensity probe that provides the intensity vector at a point. 3 Spherical arrays of microphones/hydrophones, that are the footing of this paper, have long been used in acoustics. Spherical harmonic decompositions of the measured field almost always form the basis behind the theory in these array systems and two early implementations were significant in acoustics.…”

Numerical evaluation of three-dimensional sound intensity measurement accuracies and a proposal for an error correction method

“…In the same manner, the SI spectra in the y-and z-directions, are given as those in Eq. (12). Considering the method of derivation of Eq.…”

“…Three pairs of p-p probes with six microphones proposed in Refs. [8] and [12] are arranged along the x-, y-, and z-axes, respectively. This arrangement is ideal in the sense that each of the orthogonal components is directly obtained from each pair of microphones, and the measurement positions of the three pairs can be set at the common origin of the coordinate system.…”

“…As stated before, for the analysis of a transient sound in the 3-D space, a 3-D intensity probe with at least four microphones is necessary [8][9][10][11][12][13]. Three pairs of p-p probes with six microphones proposed in Refs.…”

“…By use of the p-p probe, average sound pressure and particle velocity, and then timeaveraged and/or envelope intensities at the center of the pair microphones are obtained. The three-dimensional (3-D) SI probe enables the simultaneous measurement of 3-D SI components, which is a must for SI measurements of transient sounds [8][9][10][11][12][13].…”