Abstract:
The ability of listeners to judge the number of concurrent talkers was examined. Ten female and 11 male Japanese talkers each recorded 20 familiar Japanese words consisting of four consonant--vowel syllables each. In each trial, a number of different talkers was chosen randomly from the same-sex group, and presented synchronously to four native Japanese listeners, who were asked to judge how many talkers were present. The range of talker numbers was unknown to the listeners. To eliminate cues associated with level, the over-all sound pressure level was varied randomly in each trial, with RMS levels of the individual words equalized. It was found that judgments were nearly perfect for up to two talkers, but deteriorated abruptly for three or more talkers. In the latter case, the number of talkers was underestimated, although estimates increased slightly as the number of talkers increased. Factors that may promote sound source separation, such as lexicality (e.g., forward versus reverse speech) and spatial separation (e.g., single versus multiple loudspeakers), did not affect performance. Understanding a message in the presence of other voices may be different from the judgment of number of talkers; the former requires only the separation into two entities---one and the others.