A physically-motivated parametric model for compact representation of room impulse responses based on orthonormal basis functions

Invited paper

Giacomo Vairetti

KU Leuven

Monday 1 june, 2015, 11:20 - 11:40

0.9 Athens (118)

A Room Impulse Response (RIR) shows a complex time-frequency structure, due to the presence of room resonances at low frequencies and the intricate temporal structure of sound reflections. Many acoustic signal enhancement applications, such as acoustic feedback cancellation, dereverberation and room equalization, require simple and accurate models for representing a RIR. Parametric modeling of room acoustics attempts at approximating the room transfer function (RTF), which corresponds to the Green's function for given positions of the source and the receiver inside a room, by means of rational functions in the z-domain that can be implemented through digital filters. However, conventional parametric models, such as all-zero and pole-zero models, have some limitations. This paper unveils the existence of a direct connection between the Green's function and a particular fixed-pole infinite impulse response (IIR) filter based on Orthonormal Basis Functions (OBF). An accurate selection of the model parameters allows arbitrary allocation of the spectral resolution, so that the room resonances can be described and a compact representation of a target room impulse response can be achieved. The model parameters are estimated by a scalable matching pursuit (MP) algorithm called OBF-MP, which selects the most prominent resonance at each iteration. Results on different collections of measured RIRs show that, compared to other parametric models of similar complexity, the proposed model is capable of producing a longer approximated response, while still being able to represent the early response with good accuracy. In addition, it gives a better spectral resolution of room resonances.

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