Restoring voices on recordings, deciphering a crucial conversation in a major case or disguising voices to protect the vulnerable and undercover officers is all part of a day's work for Matthew Eardley and Adam Kaplan, who head the audio forensics team based at the West Midland Police's Forensic Services HQ. Like archaeologists who excavate a site to uncover precious artefacts, they peel away background noise, music and interference layer by layer to reveal the voices and evidence on recordings, and they have recently helped secure a nine-year conviction for a rapist after deciphering a recording that proved the offender's guilt.
Kaplan (who is trained in clinical audiology) explains, "The offender had called a taxi and didn't realise the call was being recorded. On the recording you could hear the hold music and voices in the background, but you couldn't hear what was being said. We can be working with really poor quality recordings with terrible audio and we need to make it the best it can be without changing what is being said, and this was a really complicated piece of work. But we were able to remove the music leaving only the speech, and what was said on that recording helped to add evidential weighting to the case. For this, CEDAR Cambridge provides me with the most effective tools for steady state and non-steady state broadband noise removal. It maintains good levels of intelligibility on spoken word across file formats, and holds its effectiveness when working with lossy audio formats. For forensic audio work, CEDAR Cambridge is still the go-to tool of choice."
The team supports officers by uncovering vital pieces of audio evidence in on-going investigations and operations including historic cases, and also delves into the world of counter terrorism, helping officers decipher and improve the clarity of audio recorded during major covert operations. Eardley added, "The West Midlands Police Forensic Audio Lab has used CEDAR Cambridge on some of the most high profile cases in British history and this is testament to the quality and versatility of the product and the algorithms that CEDAR provides. When developing a forensic strategy to reduce noise or increase intelligibility, tools like CEDAR's FNR, Debuzz and NR5 are first on my list."
Kaplan concluded, "We listen to hours and hours of audio and we pride ourselves on being able to find things that officers can't."
West Midlands Police w: Forensic Sciences team
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