Application of lp-norm regularisation techniques in the synthesis of indoor tyre pass-by noise with the inverse method

Abstract

The indoor pass-by noise measurement can nowadays be realised in a laboratory environment with a far field microphone array and a stationary vehicle on a rolling road, according to ISO-362-1:2016. Within this indoor testing procedure, there exists the ability to quantify the contributions from the various noise sources in a car to gain further insight into the total noise disturbance. The tyre noise contribution can be estimated by using an additional set of microphones close to the tyre and performing an inverse method. This work assumes measured near field pressure data close to a rolling tyre at different car speeds. The inverse method is utilised to find the corresponding source strength estimates which are then used to synthesise the far field tyre noise contribution and compare it with the one measured directly at the far field microphone array. A combination of novel l1 regularisation and conventional l2 regularisation methods is finally investigated to further optimise the equivalent source strength estimates and, subsequently, the far field pass-by noise pressure estimates through the frequency range of interest.