GSM interference cancellation for forensic audio: a report on work in progress

Abstract

A central aspect of forensic phonetic casework concerns the transcription of noisy recordings. An increasing problem in this area of work is the contamination of recordings with interference caused by radio transmissions from GSM mobile phones. Transmitting phones emit short duration radio-frequency pulses at a rate of 217 Hz. The induced interference signal contains the 217 Hz fundamental and a large number of harmonics that overlap the frequency range of speech, and therefore severely degrade speech intelligibility. Listener fatigue is increased due to the harsh sound of theinterference, and overall the transcription of such audio samples is problematic. This paper describes the progressing development of a filter to assist the forensic phonetician in carrying out the transcription of such contaminated recordings