| 摘要 |
In accordance with the invention an excitation signal is fed to the device under test. The excitation signal is preferably a swept or a stepped sine wave signal. A response signal from the device under test is analysed for transients, which preferably involves band pass filtering in one or more distinct frequency bands, rectification of the band pass filtered signals and low pass filtering of the rectified signals. The signals thus analysed for transients are differentiated. After differentiation the signals represent, in each frequency band, the slope or steepness of the response signal from the device under test, and are a good and reiliable quantitiative measure of the presence of possible rub and buzz in the deivce under test. In quality control of eg speaker transducers each of these steepness signals is compared to a predefined threshold value. Transducers with steepness values entirely below the threshold value or values will pass the quality control test, whereas transducers with stepness values entirely below the threshold value or values will pass the quality control test, whereas transducers with steepness values exceeding the threshold value in one or more frequency bands, have failed in teh quality control test. Devices that have failed in the test may then be discarded or possibly repaired.
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