Improving vehicle sound power estimation for road traffic noise models

Abstract

This study investigates the influence of acoustic metric selection on vehicle sound power level estimation and the resulting noise emission curves derived from Controlled Pass-By (CPB) tests. Measurements were performed on seven light-duty vehicles with diesel, gasoline, hybrid-electric, and LPG powertrains over 30–90 km/h. Sound power levels were estimated using the maximum A-weighted sound pressure level (LAFmax) and sound exposure level (SEL) related metrics through backward sound propagation. An average sound power level approach, based on instantaneous sound power within a 15 m reference space, was also proposed. Vehicle Noise Specific Power (VNSP) regression derived noise emission curves. Curves obtained from LAFmax and the proposed approach agreed within 1 dB(A), whereas SEL-based metrics showed greater sensitivity to background noise at low speeds and integration window effects at higher speeds. The proposed approach provides a robust characterization of vehicle noise emissions and supports extending CPB-based methodologies to non-steady operating conditions.