Blind identification of Ambisonic reduced room impulse response

TL;DR

This paper introduces a novel blind system identification method for Ambisonic room impulse responses that relaxes previous assumptions and improves the estimation of early-echo parameters using a direct modeling approach.

Contribution

It proposes a new approach to model GTVV impulse responses directly, overcoming limitations of previous methods that required minimum-phase assumptions.

Findings

Effective in estimating early-echo parameters

Outperforms previous methods in real-room measurements

Enhances robustness to array and beamformer limitations

Abstract

Recently proposed Generalized Time-domain Velocity Vector (GTVV) is a generalization of relative room impulse response in spherical harmonic (aka Ambisonic) domain that allows for blind estimation of early-echo parameters: the directions and relative delays of individual reflections. However, the derived closed-form expression of GTVV mandates few assumptions to hold, most important being that the impulse response of the reference signal needs to be a minimum-phase filter. In practice, the reference is obtained by spatial filtering towards the Direction-of-Arrival of the source, and the aforementioned condition is bounded by the performance of the applied beamformer (and thus, by the Ambisonic array order). In the present work, we suggest to circumvent this problem by directly modeling the impulse responses constituting the GTVV time series, which permits not only to relax the initial assumptions, but also to extract the information therein in a more consistent and efficient manner, entering the realm of blind system identification. Experiments using measured room impulse responses confirm the effectiveness of the proposed approach.