Separation of track contribution to pass-by noise by near-field array techniques
Elías Zea, Luca Manzari, Giacomo Squicciarini, D. Thompson, Inés López Arteaga · KTH Publication Database DiVA (KTH Royal Institute of Technology) · 2016
A technique to separate the track noise contribution is proposed based on identifying and extracting the track signature from the pass-by noise information measured with a microphone array relatively close to the track. Separation of the contributions of the vehicle and the track in the pass-by noise spectra is a challenging task, which is currently addressed by a combination of direct and indirect measurements and model predictions. Due to the uncertainties in the separation of the track contribution, whether a vehicle will comply with regulations during certification tests is still very much track dependent. Therefore, accurate means to identify the track contribution to the pass-by noise are needed. In this paper we propose to make use of the fact that in a wide frequency range the track is a distributed source that radiates plane waves at a given angle with respect to the track. By measuring the sound field close to the track with a microphone array, the wavenumber spectrum of the radiated sound can be determined. For the track contribution this wavenumber spectrum is tonal and therefore sparse. We make use of this property to design filters that extract the track contribution to the total pass-by noise. This is illustrated with simulations and experiments.