Strengths and weaknesses of procedures for separating simultaneous voices

Two signal-processing procedures for separating the continuously-voiced speech of competing talkers are described and evaluated. With competing sentences, each spoken on a monotone, the procedures improved the intelligibility of the target talker both for listeners with normal hearing and for listeners with moderate-to-severe hearing losses of cochlear origin. However, with intoned sentences, benefits were smaller for normal-hearing listeners and were inconsistent for impaired listeners. It is argued that smaller benefits arise with intoned sentences because harmonics of the two voices are blurred together during spectral analysis, limiting the extent to which spectral contrast can be recovered in the processed signal. This is particularly disadvantageous to impaired listeners who have reduced spectro-temporal resolution. This paper discusses other substantial problems to be overcome before the feasibility of the procedures as components of a speech-enhancement system for hearing-impaired listeners could be demonstrated.