Acoustic test systems identify faults in vehicles
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 envelope curves according to their positions. The evaluation results of recorded acoustic spectra can be classified in a values range between 1 and 20. In the end-of-line test of mechatronic assemblies a pass/fail result is derived from the classification result.
In the automotive industry, acoustics analyses provide meaningful results with regard to functional safety and manufacturing quality of electro-mechanic drives and mechatronic assemblies. Obvious background noises, such as squeaking or rattling are detected and evaluated. These noises may lead to customer complaints and OEM image loss. In the end-of-line test, faulty vehicle components can also be detected by vibrations imperceptible to the human ear.
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