Use of Schwarz-ox direct-to-reverberant power ratio estimator for distance estimation near diffuse noise point in a complex plane

This study investigated the time- and frequency- dependent direct-to-reverberant power ratio (DRR) estimators from spatial coherence value of omnidirectional microphone array. We use a mathematical 2D geometry interpretation, complex plane, to analysis the deficiency of different DRR estimators bias and construct a better estimator near the diffuse noise point in the same plane. The diffuse noise point is a reflection of a certain distance in practical environment, where the received signals in microphone array are ideal diffuse. This estimator was then applied to distance estimation in a reverberant environment. DRR values are known to exhibit more effective performance in the case of distance estimation than other acoustic indicators in such environment; however, several proposed DRR estimators are not sufficiently robust near diffuse noise points in the complex plane. Therefore, this study proposes a method to accommodate the existing Schwarz DRR estimator to exhibit better performance around the point where the far-distance estimation is made. For validation, our results focused on different directions and inter-microphone distances in two reverberant classrooms. In addition, through an in-depth investigation of the proposed method, we found that it could be expanded into a more freedom-based method, which researchers can manipulate to draw the DRR estimator pattern in the complex plane as required.