Effects of differing phonetic contexts on spectrographic speaker identification

This study investigated how well the file card system of “Voiceprint Identification” reported by Kersta fulfills its purpose of minimizing the effects of contextually caused spectral variation, and how well it serves as either an identification or population reduction tool. Subjects received training believed to be equivalent to that received by the experimenter in the Voiceprint Identification Training Course, and achieved error rates approximating those reported by Kersta for similar training tasks. Experimental tasks required subjects to identify unknown speakers from a population of 50 known speakers by first excluding all known speakers they were certain were not the unknown speaker, and then attempting absolute identification or elimination. Attempts were made under five experimental conditions created by combining two variables, phonetic context and inclusion of the unknown speaker in the known speaker population. The data show that the system tested does not effectively reduce the effects of contextual variation, and cannot be used for either absolute identification or elimination, or population reduction.The data suggest that the value of spectrograms for speaker identification purposes is limited to use as an investigative aid, and then only if speech samples of similar context and adequate duration are compared.