MediaSlap blog

Hold the noise – give me a double serving of that voice

February 19, 2009

Yesterday, Sound Works had to dig into its forensic audio tool kit to help restore two recordings for two different cases.  Recordings that need enhancement are rarely the same.  Depending on the location, equipment and recording process, each recording pretty much mandates a different restoration solution.

2-way Radio
This enhancement challenge was to remove noise and increase intelligibility of a police officer’s two-way radio recording. Although taken from a digital logger, the noise at the scene had to be analyzed. We applied several restoration processes and were able to “scoop” the conversation away from the noise.  The end result was a more intelligible recording.  Our work was then prepared as a trial exhibit by indexing the critical points on a compact disc for easy access. In sum, all the work produced a professional, presentable product for judge and jury.

Phone Recording
The second job was a recorded phone conversation for a civil case.  The phone conversation was recorded with a common suction cup telephone pickup attached to a digital recorder. Unfortunately, the pickup barely recorded the distant side of the conversation while the local side of the conversation was fine.

We were able to segment the two voices and process the audio of each side of the conversation differently.  The distant voice required the volume to be raised 80db – the equivalent to the volume of a very noisy office.  And just a couple of db improvement can make a big difference….

As you can imagine, increasing the volume to this extent raised the general ambient noise level.  One of our applications has the amazing ability to differentiate the noise from the voice allowing layers of noise to be reduced. Once the distant voice was improved, it was then merged back with the normal voice.  Our work, again, was supplied to the client in a trial-ready presentation form.

Note that each of these projects were recorded with digital devices – THAT fact alone does not insure a good-quality recording. The recorder can only capture only what it “hears”.

If you found this interesting also see “Shhh … I’m listening”, “But it’s a digital recording” and  “It seemed impossible to pick out the voice buried amongst the restaurant bedlam on the recording.”

By Dwight Cook

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Entry Filed under: Forensic Audio, commentary, legal. Tags: 2-way radio, enhancement, forensic, noise, phone recording, police radio.