AGMA 12FTM09

The sound quality of technical products is an increasinglyimportant quality criterion and has a significant influence on theproduct acceptance. But sound quality does not only depend on thephysical attributes of the sound signal. It is defined to a largeextent by human sound and noise perception. This perception isbased on a physiological and psychological signal processing. Theseaspects depend on complex properties of the physical signal likethe spectral distribution and a relative comparison. However, todaythe sound design of gearboxes is mainly based on the physicalreduction of the noise level that is detected by absolute andobjectivized parameters. The noise oriented gear design is based onphysical key parameters like the reduction of transmission error incompliance with achievablemanufacturing tolerances. Nevertheless,these design rules may lead to a minimal sound pressure level butcannot solely be applied for an optimal sound quality in everycase. Under economic and technical aspects there is no excitationfree gear set. Furthermore, modern tendencies such as lightweightdesign and masking noise reduction (engine downsizing andelectrification) lead more and more to scenarios where the sound ofa gear set, which is only designated to have low transmissionerror, can be perceived as annoying. This requires designguidelines which take also the human related aspects of gear noiseinto account. Nowadays the gear design does not yet consider humannoise perception sufficiently.

Thus, a research project at the WZL has been established thatinvestigates the correlation between gear mesh excitation and theevaluation of gear noise. The objective of this project is todeduce a method for the consideration of perception-based noiseevaluation already in the stage of gear design. Therefore,psychoacoustics metrics are used to analyze the gear noise ofdifferent gear sets in the dimensions of air-borne noise,structural vibration and the excitation due tomeshing. The aim ofthis paper is to discuss the correlation between the signalproperties of the excitation and the radiated noise in order toinvestigate the possibilities to transfer the perception relatedevaluation from sound pressure to the gear mesh excitation. Thepaper firstly shows central psychoacoustic parameters that are mostrelevant for the properties of gear noise. Furthermore, a new testfixture will be introduced that allows a dynamic measurement ofgear mesh excitation directly adjacent to the meshing. Regardingthese aspects two different gear sets are discussed concerning thecalculated transmission error and the experimentally determinedexcitation, surface vibration and noise radiation. These aspectsare accordingly examined with respect to human noise perception,which is described by psychoacoustics. It is shown that operatingconditions, order distributions as well as the gear geometry arethe main influences on the signal evaluation. The influence ofdynamic aspects and especially the influence of resonance effectson the noise characteristics are additionally considered.

Edition:

12

Published:

10/01/2012

Number of Pages:

22

File Size:

1 file , 1.5 MB