Impact of the GSM Mobile Phone Network on the Speech Signal – Some Preliminary Findings

Abstract

The landline and mobile phone networks are very different in the manner in which they handle and process the speech signal, with consequential differences in their impact on the speech spectrum as well as on the acoustic parameters of interest in the forensic arena. This paper overviews the key features of both networks which give rise to these differences. Some findings are then presented showing the impact of the mobile network on fundamental frequency, F0, as well as on the first three formants in vowel sounds. It is shown that though the impact on F0 is not great, the impact on the formant frequencies, and particularly on the measurements of these determined using automated formant trackers, can be significant. These early findings are considered to be of great importance to forensic practitioners relying on acoustic measurements as part of their investigations.