Title: Investigation of vibration, oscillation and noise in the car test

Authors: H. Helms

Addresses: Car Test, Acoustics and Vibrations, Volkswagen AG, Wolfsburg, West Germany

Abstract: The phenomena of interior noise, load cycle behaviour and idle vibration were treated as examples for investigations into comfort in cars. The interior noise problem analysed concerns excessive second order levels of engine noise. In order to identify the main transfer paths, the engine mounts and exhaust system were disconnected. The noise at the orifice of the exhaust end pipe was eliminated by an absolute muffler. Load cycle behaviour involves the fore-aft and vertical vibrations in the vehicle measured as a transient phenomenon by changing the throttle pedal position. It was discovered that, in a high gear, the associated vibrations were not perceived singly by the occupants. A subjective overall assessment was made from the peak-to-peak values of fore-aft and vertical accelerations and the decay constants. As an example of the problem of idle vibration, the report describes experimental investigations on a car with a transverse-mounted diesel engine and automatic transmission. The drive shaft, engine mounts and exhaust system were disconnected one by one and acceleration was measured at the driver|s seat. Of overwhelming significance is the transfer path in standstill via the drive shaft pretensioned with the selector lever in position D.

Keywords: chassis dynamometer; drive shaft; engine mount; fore-aft vibration; freeway hop; idle vibration; interior noise; load cycle behaviour; resonant frequency; vehicle vibration; vehicle noise; vehicle design; vehicle oscillation.

DOI: 10.1504/IJVD.1989.061553

International Journal of Vehicle Design, 1989 Vol.10 No.6, pp.609 - 624

Published online: 26 May 2014 *

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