AGMA 12FTM09-2012 pdf download.AGMA Technical Paper Systematic Approach for the Psychoacoustic Analysis of Dynamic Gear Noise Excitation By C. Brecher, M. Brumm, and C. Carl, RWTH Aachen University.
Today a gear set is designed with the objective to have a low transmission error as an indicator for low noise excitation, which is mainly distributed in discrete tonal harmonics of the gear mesh frequency. It can be quality controlled by e.g., topographic measurements or rolling tests. At operating conditions interactions between the gear set excitation and eigendynamics of the powertrain lead to a dynamic force excitation that is transmitted by structural vibrations in the shaft-bearing-housing system and radiated from free surfaces as airborne noise. The powertrain noise is evaluated by human perception as a result of a physiologic and psychological signal processing. Today already several calculation parameters are available and also partially standardized that allow considering this signal processing by objectified metrics. These psychoacoustic metrics can be used for an acoustic target design of powertrains [9] [101 [1111121 and also as a detection tool for condition monitoring objectives 1131.
However, today a method is not yet available for an adequate consideration of human noise perception in terms of the acoustically oriented gear design. Thus, the aim of this research activity is to analyze the perception related correlation between gear mesh excitation, structural vibrations and radiated airborne noise. This will allow defining a procedure to integrate the psychoacoustic signal processing into the gear design process in order to develop gear transmissions that have an increased acoustic quality rating. This paper firstly discusses the transfer of psychoacoustic metrics on the signal properties along the augmented source- path- receiver model of two different recently tested gear sets. Thereby. an analysis of the physical vibration signals is followed by a psychoacoustic discussion of these signals in an averaged way and at specific operating conditions. The latter one shows how the excitation order distribution influences the psychoacoustic rating in interaction with dynamic aspects and the transfer path at operating conditions.
Psychoacoustic evaluation parameters
Human perception of noise Is neither objective nor absolute. A lot of the physiologic and psychological reasons are not yet entirely explored. But it can be determined that the perception is not only defined by the physical level. Moreover, classifications of annoyance require a more sophisticated approach of signal analysis. Psychoacoustics metrics have been development in recent past and already partially standardized that allow evaluating an airborne noise signal with respect to different perception aspects. These metrics rate a signal considering the annoyance and even euphony regarding those perception aspects. Figure 2 gives an overview on central psychoacoustic metrics that are described in the following paragraphs.AGMA 12FTM09 pdf download.