Speaker verification with GSM coded telephone speech

In this paper we investigate the impact on the performance of Speaker Veriication (SV) systems of the signal and channel coding in GSM cellular telephone networks. In this study only the eeects of the codec are investigated. This is done by transcoding the signals in an existing speech corpus, recorded in the xed network, to GSM. We compared text dependent SV performance of systems trained with A-law speech and tested with A-law and GSM speech, as well as systems trained with GSM speech and tested with GSM speech. All SV systems compared were based on continuous density Gaussian mixtures HMM models, diiering in acoustic resolution. We have compared several parameter representations derived from FFT and LPC based spectral estimates. It is shown that (and why) LPC based estimates are to be preferred. It is also shown that it pays to extend the analysis bandwidth to the full 4 kHz ooered by the digital telephone network. The major conclusion of our research is that the impact of GSM coding on the parameter representations is marginal and can eeectively be ignored.