Improving the acuity and robustness of localization of multiple sources using ‘‘stencil’’ filters

A biologically inspired localization and speech‐enhancement technique, using two microphones, was recently developed for extracting and characterizing a sound in the presence of multiple interfering sources [Liu et al., The Second Biennial Hearing Aid RD Conference (1997)]. In the previous study, a ‘‘stencil’’ filter was created in the frequency versus intermicrophone phase delay space which significantly enhanced the acuity of sound localization. The stencil followed the multiple curves which represent phase coherence at multiple time differences. However, source artifacts resulted from the curved lines that pose a problem for identifying real versus artifactual sources and for obtaining accurate estimates of sound azimuths. These problems are more severe when the number of sources is large and when some of the sources are less intense than the others. The current study further investigated the role of the curved lines in localization from a weighted stencil filter using different weighting methods. Furthermore, an improvement was made in the localization procedure. By adjusting the weights of the stencil filter, the source artifacts were minimized and the acuity and robustness of localization were increased. The improved algorithm was particularly effective in localizing weak sound sources and in situations having a large number of sources.