Digital Audio Enhancement and Authentication/Audio and Sound Restoration

audio restorationDuring the last quarter of 2012 I saw an increasing demand from litigators requesting the audio portion of video recordings, as well as concealed audio recordings, to be enhanced – or, as I prefer to designate it, clarified and authenticated- in order to better hear the series of events that have been recorded digitally.

Since just about every case that I have worked on over the past several years has been recorded on digital media, the process for authentication and clarification using digital forensic software programs is extremely beneficial for litigators.

One of the techniques that I use that I would like to share in this blog post is to create several filters to apply to the audio file which in turn result in several enhanced or clarified ‘revised’ audio files. In other words, I listen to an audio file and create filters to apply to better hear the desired conversation. Each filter applied results in a separate audio file of the recording or version one, two, three and so on.

I go back to the raw ‘original’ file a second, third, fourth … up to ten times, creating different filters each time to apply to the original audio file in order to hear different parts of the conversation that may be masked or covered by different background sounds.

Because I have a ‘trained ear’ and have been working with spoken word recordings for nearly thirty years, as a practicing audio forensic expert I have a critical listening skill. This keen sense of hearing that most people don’t have is very important for understanding poorly recorded conversation.

I use this listening skill and create a forensic transcript. The forensic transcript helps the litigators better understand the conversation or poorly recorded audio. The multiple filters and variations of that audio file allow me to hear the conversation in various sections much better in order to create the forensic transcript.

As an example, if I’m conducting a forensic investigation and trying to determine what is being said in a busy restaurant where there are other voices talking, dishes clanking, and even music playing I will apply filters to the recording and then listen to the recording and write down the words that I can hear from that first filter application.

Then I will go back to the original file and create different filters to help remove different parts of the background noise to allow me to hear additional words that I may not have been able to hear from the first filtering pass. The combination of creating multiple restored files and a forensic transcript has been very successful. I see this forensic application being very successful and necessary in the future.

The need for a forensic expert to enhance, or clarify, audio recordings will increase due to the number of conversations that are being recorded in public places. Forensic processes similar to this will be extremely important as technology changes and more and more clarification becomes necessary.

photo credit: 24/96 via photopin (license)

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