Transient Acoustic Analysis of a motor run-up in a vehicle using a modular 4096 channel MEMS Mirophone Array

Regular paper

Wouter Ouwens

Sorama B.V.

Tuesday 2 june, 2015, 09:20 - 09:40

0.8 Rome (118)

An important research area in the automotive industry is transient acoustic analysis of a vehicle, to improve the comfort for the passengers and to improve the reliability of the car. Sorama developed a 4096 channel digital MEMS microphone array, currently the largest microphone available, to help analyse and understand the transient dynamic behaviour of acoustic sources, such as a run-up of a motor in a vehicle, using Planar Near-field Acoustic Holography (PNAH) and Acoustic Beamforming. The 4096 channel microphone array, covering a total area of 1.2 by 1.2 meters, is able to reconstruct sources better, while reducing costly measuring time compared to typical microphone arrays. The basic building block is a low-cost square 8 by 8 digital MEMS microphone array with a spacing of two centimeters. An arbitrary size microphone array can be constructed, based on this building block. Besides a good measurement system, a good measurement paradigm is required. The first step in the process is obtaining a global overview of the acoustic behavior of the vehicle using the far-field technique Beamforming. The properties of the array results in a large Beamforming frequency range (500 Hz up to 6 kHz alias free) and a high reconstruction resolution. Beamforming is able to identify multiple sources during the run-up of a motor and how it is influencing the vehicle. Based on these results, several hot-spots are analyzed in depth using PNAH. PNAH is able to accurately reconstruct the transient behavior of an area of 1.2 by 1.2 meters, roughly the size of a motor, with a resolution of two centimeters and a frequency range of 1 Hz to 20 kHz. This gives the engineer detailed information about the transient dynamic behavior of the whole vehicle in only a single measurement step, greatly reducing measurement time compared to standard measurement systems.

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