Simulation and Validation of the Isolation-Effect of Acoustic Encapsulation Concepts Based on a Generic Electric Motor Housing

Along with the increasing importance of battery electric vehicles for the automotive industry, new challenges have emerged in the development process of the acoustic behavior of the electric powertrain. One concern arises from the high-frequency whining noise, either caused by the electric field of the motor or by the gearbox. Noise is transmitted via two different paths, the structure-borne path and the airborne path. The focus here is on the latter one, which describes the radiated sound from the surface of the motor housing and the transmission through the car body to the driver’s ear.
One possibility for reducing the effect of this acoustic radiation is the application of passive acoustic noise control treatments. This is typically done either by attaching secondary treatments on the vehicle-body side or by encapsulating the motor directly. Depending on the applied material concept, the motor-mounted encapsulation approach isolates the motor and/or adds absorption to the engine bay.
To implement a process for the prediction of the acoustic isolation effect of encapsulation in the early design stage, an investigation has been undertaken where different material concepts are applied to a generic motor housing (GMH). The isolation performance of these encapsulation concepts is evaluated by exciting the housing with an electrodynamic shaker and measuring the radiated sound power. First, the investigation is performed experimentally; afterward, corresponding simulations are validated by test results. Various conclusions can be drawn from this study for certain aspects of the process and the simulation model.