2nd ICAI 2022

International Conference on Automotive Industry 2022

Mladá Boleslav, Czech Republic

Figure 10: Level of the acoustic pressure for the whole range of rpm

Source: own elaboration (2021) Figure 11 shows in the spectrogram the course of each harmonic gear mesh frequencies for both gear pairs in the speed range of the transmission at a given load.The approximate situation with tonality for the required speeds can be read from the spectrogram. The key requirement for tonality is that the protrusions of gear mesh frequencies are as small as possible. That applies also for their harmonic and non-harmonic values in FFT and CPB spectra. In this spectrogram, the tooth frequencies of the bevel gears and the second harmonic frequencies of the helical gears are very close, which is unsuitable in terms of tonality. It is better if these waveforms are more apart to fill the empty space without sources of noise. Furthermore, it can be seen from the spectrogram that the resonant regions are distributed over multiple harmonic frequencies of the gears, so that this case is better for tonality.

Figure 11: Spectrogram for the excitation from gear mesh

Source: own elaboration (2021) After the gearbox optimization to reduce the acoustic emission and the actual production of the gearbox prototype, we made verification measurements of the sound pressure level of the gearbox on the test equipment. The measurement was performed using a Pulse device from Brüel & Kjær.

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