Contribution
Determination of bidirectional scattering coefficients from measured scattering patterns
* Presenting author
Abstract:
The absorption and scattering coefficients of surfaces play a critical role in acoustic propagation simulations. However, the scattering coefficient defined by ISO 17497-1 is widely recognized as one of the most uncertain metrics in geometrical acoustics. In outdoor sound propagation simulations, the impulse response is typically sparse rather than diffuse, making the amount of scattered energy more significant for sound immission at the receiver. While standard random-incidence scattering coefficients are often applied, they do not adequately represent sound reflection from building facades. So far, specific reflection patterns have neither been established nor incorporated into simulation algorithms.In this paper, a new metric for bidirectional scattering coefficients is introduced, which includes sound steering and retro-reflection. The coefficients are determined from measured scattering patterns of two reference surfaces and validated with analytical calculations and Boundary Element Method (BEM) simulations.The measured scattering pattern are obtained by two different setups in Sydney, Australia and Aachen, Germany.Finally, an urban scene is auralized with the new scattering coefficients and compared with the results of a purely specular or mixed specular/random-incidence data set.