Abstract
While the technique of auralization has been in use for quite some time in architectural acoustics, the application to environmental noise has been discovered only recently. With road traffic noise being the dominant noise source in most countries, particular interest lies in the synthesis of realistic pass-by sounds. This article describes an auralizator for pass-bys of accelerating passenger cars. The key element is a synthesizer that simulates the acoustical emission of different vehicles, driving on different surfaces, under different operating conditions. Audio signals for the emitted tire noise, as well as the propulsion noise are generated using spectral modeling synthesis, which gives complete control of the signal characteristics. The sound of propulsion is synthesized as a function of instantaneous engine speed, engine load and emission angle, whereas the sound of tires is created in dependence of vehicle speed and emission angle. The sound propagation is simulated by applying a series of time-variant digital filters. To obtain the corresponding steering parameters of the synthesizer, controlled experiments were carried out. The tire noise parameters were determined from coast-by measurements of passenger cars with idling engines. To obtain the propulsion noise parameters, measurements at different engine speeds, engine loads and emission angles were performed using a chassis dynamometer. The article shows how, from the measured data, the synthesizer parameters are calculated using audio signal processing.
Highlights
Noise caused by traffic is a relevant health factor in urban environments, along major transport routes and in the vicinity of airports
In [5], a granular synthesis using an enhanced pitch-synchronous overlap-and-add (PSOLA) method is presented for engine noise
In the proposed auralization model, emission sounds of accelerating passenger cars are artificially generated based on spectral modeling synthesis
Summary
Noise caused by traffic is a relevant health factor in urban environments, along major transport routes and in the vicinity of airports. In [5], a granular synthesis using an enhanced pitch-synchronous overlap-and-add (PSOLA) method is presented for engine noise This method features low computational costs and is well suited for real-time applications. It is limited in terms of flexibility, as it does not allow for inter- and extrapolations between measured signals. The second module needed in the auralization process is a filter that simulates the sound propagation effects of the wave traveling from the source to the receiver. These effects involve geometrical spreading, propagation delay and atmospheric absorption.
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