Messanordnung zur frequenzselektiven Beurteilung der richtungsbezogenen Bedämpfung der durch Verbrennungsmotoren angeregten Körperschallausbreitung mittels Active Noise Control

A combustion engine causes vibrations, which are transmitted as mechanical vibrations via the vehicle’s frame structure into the passenger car cabine. This usually annoying noise is perceived either directly as a vibration or indirectly as an acoustic sound.

The aim of this project is to develop and evaluate a method to selectively attenuate the amplitudes of multiple harmonic components - produced by engine firing - with active noise control (ANC). Especially, the directionality of wave propagation in solid bodies is very important and is taken into account.

The only data that is available to compute the reference signal for the ANC algorithm are the engine (angular) speed and the thereof derived engine order, which is equal to the engine firing frequency. The first harmonic component that has to be attenuated is inside a region of 15 Hz and 90 Hz, depending on the engine rotation speed and the engine load (e.g. acceleration, deceleration).

Because all the signals, that have to be attenuated, are multiples of the motor order, we can use narrow-band ANC algorithms, whose major advantages are fast convergence and excellent tracking behaviour, both caused by the possibility to use short adaptive filters. Finally, the attenuation of the annoying harmonic noise components is expressed as a function of the ANC’s actuator (shaker) position and steering direction. This allows to optimally position the actuator to reduce each directional mode separately.