Audio Forensic Enhancement

Analogue Audio Recordings

If you have an analogue recording, we utilise the best available professional digitisers to capture and digitise the audio into a high quality uncompressed digital data stream. This will become our working copy. Ideally the original recording equipment should be used in this replay and capture process if possible.

Due to the age of magnetic tape reels, special handling and processing may be required to minimise the loss of recorded signal due to the flaking off of the magnetic coating from the base material. The degradation of magnetic tapes is sped up by the storage of the media in uncontrolled temperature and humidity environment. Do not attempt to play or respool/retention the tape if you suspect it is in poor condition.

We can perform the digitisation of the recording at your premises with our mobile unit if necessary so that your original recording does not have to leave your secure environment.

Digital Audio Recordings

We strongly recommend that you create a duplicate copy of your digital audio file and generate a SHA-1 and MD-5 Hash Key on both the original file and the copy to verify a true and error free copy of your file was made. You can then forward both the working copy and the Hash Keys to us via a variety of means. Media Forensics can then verify that the file was received error free by confirming the Hash Key on receipt. Do not open the file in an editing application for cropping and/or renaming and resave it. This will modify your metadata and apply additional compression to the recording. If this occurs the file will probably be considered to not be authentic as it is no longer a true duplicate copy of the original.

Digitally recorded data is less forgiving and limiting as to what can be achieved in cases where the original recording had inappropriate settings applied such as too low a sampling rate, low number of bits per sample, amplitude set too low or too high. Steps can be taken to mitigate some of these shortcomings. However, the level of success will vary on a case to case basis.

All work done will be non-destructive, fully documented  and be reproducible on a step by step basis. This level of detail is typically required for the work to be accepted as evidence in a court of law. For private work that will not be admitted to court, the documentation can be bypassed to provide a lower cost point. However, this work must not be later submitted as evidence under any circumstances.

The use of data compression algorithms (as used in most recordings) and the choice of encoder type can affect our ability to enhance the data to some degree. If you are making the recording, always select the best possible quality settings to ensure the best possible results.

Audio Enhancement

Forensic audio enhancement processes include but are not limited to:

  • Vocal component matching.
  • Filter out interfering noise, crackles pops etc.
  • Enhance and isolate desired voice or background activity.
  • Produce transcripts and associated flags in the audio recording.
  • Read, convert and write from and to almost any audio codec and media format.
  • Separate, align and/or merge multiple tracks.
  • Playback speed and pitch adjustments.
  • Cell phone noise filtering.
  • Adaptive noise threshold filtering.
  • Channel blending.
  • Artifact suppression.
  • Mono to Stereo with tailored channel balancing, Stereo to Mono conversions.
  • 30 band graphic equalisation.
  • Hiss, hum, echo and reverb reduction.
  • Speech volume leveler, audio normalisation and de-clipping.
  • DC offset adjustment.