< Back to previous page

Project

Auralization of Moving Sources: Application to Pass-by and Fly-over Real-Time Sound Synthesis

The impact of traffic noise on the health of individuals living in urban areas is a major concern.
Initiatives aimed at reducing traffic noise are put in place by imposing maximum noise levels on new combustion engine vehicles or minimum noise levels on electrical vehicles.
In addition to respecting sound level limits, an increasing need for satisfying sound quality requirements calls for new measurement and simulation methodologies to assess noise vibration and harshness in the early stages of vehicle design.
Sound synthesis enables the audio experience of virtually generated sounds, and its auralization provides a controlled environment to establish correlations between sounds and their effect on individuals.

This thesis proposes measurement-based methods for the sound synthesis of moving sources in cases such as pass-by and fly-over noise.
This requires the characterization of complex sources and propagation paths.
Experimental methods relying on microphone arrays are proposed, for instance for the decomposition of complex sources in terms of equivalent acoustic monopoles, and for the measurement of discrete time- or angle-dependent transfer paths between a moving source and a static receiver.
Furthermore, an experimental procedure to characterize angle-dependent sound absorption of porous grounds is proposed and a clear improvement over the classical two-microphone method is achieved.
In addition, physics-based filtering elements such as sound reflection and sound transmission loss are incorporated into the sound synthesis methodology.

Three techniques to render moving sources are explored in this work:  namely an analytical model of the sound propagation, a digital filter approach and a spherical harmonics representation.
The analytical model, together with models for sound reflection on porous grounds and sound transmission through panels, enables the sound synthesis of moving sources in arbitrary scenarios.
In the digital filter approach, the transfer paths are modeled as Z-domain transfer functions whose coefficients are experimentally measured, and then interpolated to achieve the moving source effect.
In the spherical harmonics approach, the sound field is decomposed into a spherical harmonics basis function which allows the dynamic rendering of both source and listener and enables an immersive spatial audio experience. 
A central focus of this work is the achievement of real-time audio rendering without generating audible artifacts while preserving accurate source contribution and sound pressure levels.

Examples of application of the proposed sound synthesis techniques are shown in the form of three demonstrators, including ground vehicles and a drone.
Finally, the two measurement-based sound synthesis approaches are compared objectively and subjectively, and it is shown that both techniques are capable of accurately and efficiently synthesizing a moving source.

Date:4 Mar 2020 →  2 May 2023
Keywords:Acoustic characterization, Sound synthesis
Disciplines:Acoustics, noise and vibration engineering
Project type:PhD project