To identify gear orders in a multiple motor component environment a specific method for the generation of order spectrograms has been implemented into S_TOOLS-STx. The method applies smoothing on the rpm-signal and uses re-sampling as well as the Discrete Fourier Transform (DFT) in combination with the anti aliasing filter to create order analysis spectrograms at reasonable computational cost.
The graph below the Order Spectrogram displays the revolutions per minute (rpm) of a car engine accelerating and reducing the driving speed. The graph at the left margin shows the time averaged amplitude of all orders displayed in the Order Spectrogram. The insert on the top to the right of the order Spectrogram shows the sound signal amplitude (in dB) belonging to selected orders over time. Red circles indicate the appearance of perceptual relevant orders in dependence of rpm. The order analysis in combination with the psychoacoustic masking model improves the process of "Sound Quality Design" considerably.
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