Japanese formant frequencies in mobile phone transmission: Implications for Forensic Voice Comparison

Mobile phones are now widely preferred over fixed-line telephones for global communications, and this includes their use to conduct criminal activities. This paper describes an experiment investigating the impact of mobile phones transmission on vowel formant frequencies (F1-F3) in Japanese. This is assessed in terms of the direction and size of frequency shifts associated with spectral distortionand discusses some of the implications this has for Forensic Voice Comparison (FVC). Results show F2 and low F3, typically well preserved over fixed-line transmission, frequently exhibit substantial and highly variable discrepancies between microphone and mobile recordings. Although F1 is found to be comparatively well preserved, these findings are of major concern to FVC given the usefulness of F2 and F3 as acoustic parameters in speaker discrimination.