Acoustic test systems identify faults in vehicles

December 18, 2013 // By Christoph Hammerschmidt
With two new products, automotive test solution provider Göpel electronic GmbH addresses the demand of acoustic analysis of vehicles. Applications include evaluation of vehicle operating noise in development and prototyping and automated production line tests.

The SoundChecker is a cost-effective mobile structure-borne noise analysis system capable to receive signals from up to four sensors. The sampling rate is 51.2 kS/s. The device is connected via USB to a Host PC, on which operating software and evaluation software are installed. A Windows DLL provides all necessary function calls for integrating acoustics analysis into complex functional test environments or user programs. Alternatively, a LabVIEW library with respective Virtual instruments (VIs) is available.

SoundChecker analyses the frequency spectrum, whereby the frequency area to be checked can be partitioned into three individually definable spectral ranges. In each of these ranges, acoustic performance is determined and examined against a parameterizable limit. Another evaluation mode is 'third octave analysis' that analyses recorded sounds according to human listening behaviour. This enables an evaluation regarding to what extent sounds, which may occur in vehicles and vehicle parts, are considered annoying.

The second product is the CARoLINE acoustics analysis system. It provides an extended functional range and higher performance compared to SoundChecker. The system was developed for automated production lines and has a standard SPC connection that can be implemented via a serial interface or by means of a network connection using TCP/IP.

CARoLINE can be equipped with up to four measurement cassettes. In addition to the structure-borne sound sensor's waveform sequence, they can detect UUT-specific characteristic values. For example, sound impulses or displacement signals, which help to exactly relate an occurring frequency spectrum to a certain position of drive components to be tested, or the so-called power ripple to determine the rotational speed of drive motors. A function library is available containing filtering characteristics and mathematic operations, helping with generation of individual evaluation algorithms, e.g. for determining crest factors.

The range of evaluation functions includes order tracking for electronic motor driven assemblies as well as modulation analysis, evaluating amplitude fluctuations of detected frequency components. Furthermore, CARoLINE offers a boundary value analysis of definable