Meeting Report February 2014: Visit to Vic Police Forensic Audio Studio

On Mon Feb 10th 15 AES members squeezed into one of several forensic audio studios at Victoria Police’s McLeod Forensic Science Centre.

Forensic Officer Jason Ferridge welcomed the group & introduced his colleague Dean Catoggio.

He explained that the studios had been in place for almost 20 years, and then went on to describe the room’s acoustic design.

Jason and Dean then described the type of work handled by the Forensic Audio/Video section, explaining that it was exclusively speech with the goal to ultimately make the speech easily intelligible, for transcription by others, and playback in a courtroom environment. 

Jason discussed some “historical” surveillance recording devices, like the Nagra SN, and Dean explained that they were not at liberty to discuss the specifics of the equipment currently in use.

Jason explained that common requirements were enhancing the speech within the noise floor, and the suppression of extraneous audio – like a foreground TV or radio signal – the result of the talker inevitably being at some distance from the “bugging device”.

He also explained that they provide advice to transcribers about how they can optimize their listening equipment to assist intelligibility, commenting that using a pair of high- quality headphones instead  of a set of poor quality computer speakers often improves the intelligibility of the speech as much as anything else they can do.

Jason then described and demonstrated the equipment and software they use to process the audio, with particular emphasis on the Cedar software package.

They both then described the specifics of some techniques used to remove the noise by both cancellation methods and filtering.

Jason and Dean then recounted their experiences from several high profile cases where they had worked on surveillance material – from the Silk-Miller police murders to the Purana Task Force (“Underbelly”) investigations.

The evening rounded out with range of questions from the audience.