GRODMIC Performance Improvement based on Group Delay Ripple Reduction

GRODMIC (GROup Delay between MICrophones) is a method proposed as a high spatial resolution source direction estimation for two microphones. Since a spatial aliasing is not required to consider for its applying, spatial resolution can be improved by extending the microphone width. In this method, the propagation delay characteristics between microphones are estimated by an approximation model, and the TDOA (Time-Difference-Of-Arrival) is estimated from the group delay characteristics. Therefore, the accuracy of group delay characteristics is important. However, multiple ripples tend to occur in the estimated group delay characteristics due to the high order model together with increasing of the wide width microphone pair. Due to this degradation of estimation accuracy, the advantage of high spatial resolution is lost. As a result, high direction estimation performance is limited to a situation to be able to apply a low order model. In this study, a reduction method of model order is proposed based on the approximation model characteristics.