Telefoniske båndpasfiltres indflydelse på talergenkendelse: høje frekvenser og dansk /t/

Abstract

This

article is an investigation into how telephonic bandpass filters affect the

speech signal with possible implications for forensic phonetics. The focus is

on three different filters: The filter used in landline connections; the AMR filter, which is used in most cell phone connections, and which delivers a worse signal than landline connections if coverage is poor; and the VoLTE filter, which delivers the most modern signal and is used in newer smartphones. The article shows how variation in the pronunciation of Danish /t/ can be used to identify a specific speaker, e.g. in the context of forensic phonetics. Three different sources of /t/-variation are presented: dialectal variation, variation in the pronunciation of foreign languages, and idiolectal variation among speakers of Standard Danish. For all of these sources of variation, it is shown how telephonic bandpass filters affect the speech signal, and especially how landline- and AMR-connections erase much of the variation as these connections do not transmit particularly high frequencies. The parameters which a forensic phonetician would look at in a high quality recording will often not be available in a recorded telephone conversation. The article thus suggests some other parameters in the speech signal which can be worth looking at if looking for variation in the production of /t/ in a telephone recording.