Audio compression and speaker’s discrimination : perspectives for forensic phonetics in the Italian setting

In forensic phonetics, speaker’s recognition is considered as a conventional chore. The purpose of this work is to analyse whether and to what extent (1) the expertise of the evaluators and (2) reading and spontaneous speaking styles influence the speakers’ identification. Our analysis is founded on two different perception experiments. The first one is a real case we worked on in which we challenged both speaker with experience in the audio field and lay speakers to compare two voices in short and low-quality audio files, obtaining very weak result. From these findings, we settled a second ‘laboratory’ experiment with made-up files recorded by 1 Italian female speaker in 3 settings both for reading and spontaneous speech: high quality recordings, WhatsApp audio and phone call recordings. These data were used in a perceptive test where respondents were asked to point out the recording modality of each sample and specify whether the speaker was the same. Results of this second test show that self-declared experts in audio analysis or transcriptions behave similarly to lay speakers, and that the comparison is more reliable for spontaneous speech when the audio quality is not the same. This result confirms the need to adequately train professionals combining subjective listening with in-depth acoustic and linguistic analyses, and take speech style into account when recording speech samples for comparative analyses.