Method for analyzing transient noise based on instantaneous intensity measurements English

Analysis of random and transient noises (i.e. squeak and rattle phenomena or clicks caused by the expansion of electrical heaters) cannot be solved properly with conventional methods based on spectral analysis of acoustical pressure, because the Fourier transform involves time averaging of very short events and the noise level cannot be correctly estimated. For this main reason, the CTTM has developed a noise analysis method in the time domain by measuring the instantaneous acoustic intensity using an antenna of three sound intensity probes (p-p probes). This method uses the Hilbert transform to express the instantaneous complex intensity where real part represents the propagative component (active intensity). The localization of transient noise is obtained by a triangulation method. The magnitude is calculated by taking into account the location of the noise.

This paper presents the theoretical basis of the instantaneous intensity analysis method and shows results of experimental qualifications of instantaneous intensity measurements and localizations of impulse type noises. The test rig described uses miniaturized intensity probes and an analysis and processing system developed by CTTM.


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