Abstract
Keywords - Gear, Rattle, Noise, Objective, Assessment
Abstract - A method to estimate the gear rattle phenomenon through gearbox vibrations and acoustic emissions measurements is presented and applied to a 5-speed manually-shifted transmission under a realistic transient load condition.
The experimental tests are performed in a semi-anechoic chamber using a Virtual engine simulator test rig. This allows the easily changing of some gear rattle noise influencing parameters, such as input speed fluctuation amplitude and/or frequency, in order to amplify or attenuate the phenomenon.
The most common method used by the researchers for the gear rattle noise level assessment is a subjective evaluation, but this method has some drawbacks such as: the rating is too much dependent from the examiners ability to distinguish the phenomena, moreover, it may change time after time depending on the auditor mood.
The method presented in this study, instead, points the attention to the objective assessment of the phenomenon occurring inside the gearbox. As a first step, we looked at the house vibrations as function of velocity, as a next step, because of the housing vibrations depend on the housing acoustic impedance itself, we have correlated them to the sound pressure level 1 meter far from the gearbox.
This methodology has allowed us to make a comparison between different gearboxes for a benchmark analysis and has helped the designers, during the development of a new quiet gearbox, to test new solutions just looking one meter far from the gearbox itself.