Effective Rank-Based Estimation of the Coherent-to-Diffuse Power Ratio

Many algorithms for speech dereverberation and noise reduction rely on an estimate of the coherent-to-diffuse power ratio (CDR). Such systems typically operate in very diverse acoustic conditions, and CDR estimators relying on very weak model assumptions about the acoustic sound field of the desired speech and interfering noise are hence desirable. A CDR estimator whose design is based on this premise is devised in this contribution. The proposed non-iterative CDR estimator exploits the effective rank of the spatial covariance matrix of the recorded input signals by assuming it to be lower for a coherent sound field than for a diffuse sound field. In addition to this weak assumption, related methods usually require information about, e.g., the array geometry, direction-of-arrival (DOA) of the desired source or rely on a coherence model for the desired signal or background noise, which is not required for the proposed method. Despite the use of little a priori information about the acoustic sound field, the new estimator achieves a significantly higher estimation accuracy for the CDR in comparison to related state-of-the-art approaches which use explicit coherence models.