Low-speed Boom Noise - Escalating Relevance According to CO2- Targets and High Torque Engines 2012-01-1547
The increasing shift of drive operation towards efficient engine operation points at very low engine speeds demands a concerted design and tuning of engine, drive-train, assembly attachment and body to avoid annoying low speed boom noise. An additional challenge in this area of conflict is the increasing torque of modern engines at low engine speeds.
As an example for a standard passenger car, the modes of operation, which may lead to low speed boom noise, are described. Setting levers along the complete chain of effect are characterised - from cylinder pressure up to the radiating surfaces of the interior.
To achieve challenging NVH-targets the application of nonlinear simulation systems is indispensable, in particular in the concept phase of a vehicle. The use of multi-body simulation is presented for a concentrated NVH-optimisation of powertrain and rear axle vibration behaviour to reduce low-speed boom noise.
On entire vehicle level hybrid simulation models are useful. Measured or calculated body transfer functions in combination with multi-body simulation result in boom noise forecasts. Analysis conclusions enable the identification of effective setting levers and course of action, to achieve defined targets.
Without testing support and measurement-based analysis an optimal tuning of all relevant components is impossible. With measurement techniques for mount load identification and running mode shape analysis parameters and physical quantities of the vehicle are measured for a subsequently verification with simulation results.
The alliance of testing methods and CAE process during the hardware phase of the vehicle development process is described using the example of low speed boom noise.