Transient Acoustic Analysis of a motor run-up in a vehicle using a modular 4096 channel MEMS Mirophone Array
Regular paper
Sorama B.V.
Tuesday 2 june, 2015, 09:20 - 09:40
0.8 Rome (118)
Abstract:
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.