The 'Mobile Phone Effect' on vowel formants

Abstract

This study analyses the effect of mobile phone transmission on vowel formant frequencies, based on the study presented by Kuenzel (2001). Six male and six female speakers read a short passage into a mobile phone. Two simultaneous recordings were made, one at the far end of the phone line and the other via a microphone directly in front of the speaker. Measurements of F1, F2 and F3 were taken from between 15 and 25 stressed vowels per speaker in both sets of recordings. Due to the filtering effect of the phone transmission, F1 frequencies for most vowels were found to be higher than their counterparts in the direct recordings. The overall effect of the mobile phone on F1 frequencies was considerably greater than the landline telephone effect found by Kuenzel (2001): on average the F1 values in the mobile condition were 29 per cent higher than in the direct condition. On the whole F2 measures were not significantly affected, in line with Kuenzel’s findings. F3 frequencies were also generally unaffected by the mobile phone transmission. Exceptions were found, however, particularly for individual speakers with relatively high F3s. In these cases the mobile recordings tended to yield significantly lower values. The consequences of measurement errors arising from the different recording conditions are discussed with reference to forensic speaker identification.|