Speaker identification utilizing noncontemporary speech

The noncontemporariness of speech is important to both of the two general approaches to speaker identification. Ear-witness identification is one of them; in that instance, the time at which the identification is made is noncontemporary. A substantial amount of research has been carried out on this relationship and it now is well established that an auditor's memory for a voice decays sharply over time. It is the second approach to speaker identification which is of present interest. In this case, samples of a speaker's utterances are obtained at different points in time. For example, a threat call will be recorded and then sometime later (often very much later), a suspect' s exemplar recording will be obtained. In this instance, it is the speech samples that are noncontemporary and they are the materials that are subjected to some form of speaker identification. Prevailing opinion is that noncontemporary speech itself poses just as difficult a challenge to the identification process as does the listener's memory decay in earwitness identification. Accordingly, series of aural-perceptual speaker identification projects were carried out on noncontemporary speech: first, two with latencies of 4 and 8 weeks followed by 4 and 32 weeks plus two more with the pairs separated by 6 and 20 years. Mean correct noncontemporary identification initially dropped to 75-80% at week 4 and this general level was sustained for up to six years. It was only after 20 years had elapsed that a significant drop (to 33%) was noted. It can be concluded that a listener's competency in identifying noncontemporary speech samples will show only modest decay over rather substantial periods of time and, hence, this factor should have only a minimal negative effect on the speaker identification process.