MediaSlap blog

Solved by forensic audio detection

March 18, 2009

Some TV crime scene investigation programs tend to be more fiction than reality for the sake of drama. But even if you disregard the drama, today’s audio evidence restoration possibilities are truly amazing.

What is audio restoration? It’s more than someone running your audio program through an equalizer (a glorified tone control with multiple frequencies). The process actually seeks to repair the sound. If you are faced with restoring audio evidence, here are some aspects in regard to the process to familiarize yourself with before speaking with a forensics audio engineer:

Audio Recording

• Decide exactly what sections of the evidence need to be restored.
• Know the time length of the audio to be processed.
• Identify the media format of the recording (example: micro or standard cassette).
• Provide the original recording, if possible (copies introduce more noise).
• Make sure the restoration process is non-destructive to the original recording.
• Get an evaluation sample and listen to what can be done to improve your recording before you commit to having the whole recording processed.
• Have the restored audio supplied in a trial-ready format.

There are many resources in a forensic audio engineer’s restoration toolbox: volume leveling, analogue and digital EQ, compression, expansion, scientific filters and advanced analysis software. Many projects require a combination of these be applied. Even projects that are less demanding or cost-sensitive may still benefit in the intelligibility aspect of the recording.

What can be restored? Conversations made on hand-held recorders, audio from video tape, phone conversations, and surveillance recordings. An experienced forensic audio engineer can repair, improve or eliminate unwanted noise and improve the intelligibility of a recording suffering from issues such as:

Get rid of the NOISE

• AC hum

• HVAC units
• Cameras
• Generators
• Motors
• Noise from mechanical damage to the recording
• Wireless microphone noise
• Distortion caused by overload
• Ambient room noise
• Buzz
• Fixed frequency noise
• Clicks and pops
• Crackle
• Background noises

SoundWorks has over 25 years of experience in forensic audio and has restored hundreds of sound recordings. We also supply expert witness services and have testified in local, county, state and federal cases

Entry Filed under: Forensic Audio, audio production, legal. .