The effect of LPC (Linear Predictive Coding) processing on the recognition of unfamiliar speakers

The effect of narrowband digital processing, using a linear predictive coding (LPC) algorithm at 2400 bits/s, on the recognition of previously unfamiliar speakers was investigated. Three sets of five speakers each (two sets of males differing in rated voice distinctiveness and one set of females) were tested for speaker recognition in two separate experiments using a familiarization-test procedure. In the first experiment three groups of listeners each heard a single set of speakers in both voice processing conditions, and in the second two groups of listeners each heard all three sets of speakers in a single voice processing condition. There were significant differences among speaker sets both with and without LPC processing, with the low distinctive males generally more poorly recognized than the other groups. There was also an interaction of speaker set and voice processing condition; the low distinctive males were no less recognizable over LPC than they were unprocessed, and one speaker in particular was actually better recognized over LPC. Although it seems that on the whole LPC processing reduces speaker recognition, the reverse may be the case for some speakers in some contexts. This suggests that one should be cautious about comparing speaker recognition for different voi ce systems of the basis of a single set of speakers. It also presents a serious obstacle to the development of a reliable standardized test of speaker recognizability.