Coherent-to-Diffuse Power Ratio Estimation for Dereverberation

TL;DR

This paper introduces new unbiased methods for estimating the coherent-to-diffuse power ratio (CDR) from microphone signals, improving dereverberation and speech recognition performance.

Contribution

It proposes novel unbiased CDR estimators that require less prior information, enhancing dereverberation effectiveness and robustness.

Findings

Proposed estimators outperform existing methods in bias and robustness.

The DOA-independent estimator enables blind dereverberation.

Significant improvements in speech quality and recognition accuracy.

Abstract

The estimation of the time- and frequency-dependent coherent-to-diffuse power ratio (CDR) from the measured spatial coherence between two omnidirectional microphones is investigated. Known CDR estimators are formulated in a common framework, illustrated using a geometric interpretation in the complex plane, and investigated with respect to bias and robustness towards model errors. Several novel unbiased CDR estimators are proposed, and it is shown that knowledge of either the direction of arrival (DOA) of the target source or the coherence of the noise field is sufficient for unbiased CDR estimation. The validity of the model for the application of CDR estimates to dereverberation is investigated using measured and simulated impulse responses. A CDR-based dereverberation system is presented and evaluated using signal-based quality measures as well as automatic speech recognition accuracy. The results show that the proposed unbiased estimators have a practical advantage over existing estimators, and that the proposed DOA-independent estimator can be used for effective blind dereverberation.