Coherent-to-Diffuse Power Ratio Estimation for Dereverberation
This work addresses dereverberation in audio processing, which is important for improving speech quality and recognition in reverberant environments, but it is incremental as it builds on known CDR estimators.
The paper tackled the problem of estimating the coherent-to-diffuse power ratio (CDR) for dereverberation by proposing novel unbiased estimators that require knowledge of either direction of arrival or noise field coherence, and showed these estimators offer practical advantages over existing ones and enable effective blind dereverberation.
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.