Audio Enhancement and Audio Restoration Services

WHAT IS AUDIO ENHANCEMENT?

Audio enhancement or audio restoration is the process of clarifying audio recordings to increase intelligibility. In order to remove unwanted noises like static, HVAC fans, hums and other distracting sounds, processing techniques must be applied to them first. These distracting noises are also known as “unwanted sounds”. Once these sounds have been reduced or removed, then processing techniques can be applied to accurately increase the “desired sounds”.

A forensic approach to audio enhancement or audio restoration preserves the evidence integrity as well as admissibility into court. Often times when a lay person makes adjustments to a recording in an attempt to increase the ineligibility of the recording, they may make changes to the recording which makes it an inaccurate representation of the events and inadmissible to a trier of fact.

A qualified forensic expert must perform the  audio enhancement or audio restoration investigation, document the procedures used, and present their work product in order for a trier of fact to admit it as evidence. Edward Primeau has been practicing audio and video forensics for over 30 years as an audio expert witness.

TYPES OF RECORDINGS

We examine a variety of audio evidence recordings including but not limited to; recordings made on smart phones, deposition video, digital handheld recorder, digital pocket recorder, cassette tape, micro & mini cassette tape, law enforcement dash cam, 911 dispatch, courtroom recording, confidential informant, wire tap, voice mails and many more.

CRITICAL LISTENING

Critical listening is key for identifying different sections and dialogue of the recording for audio enhancement. When I refer to sections, I mean portions of the audio that have different characteristics such as levels, frequency ranges, or signal to noise ratios.

For example, the first section may have two people talking quietly with a lot of street and car noise in the background. The next section may have a more audible conversation with a train passing far off in the distance.

The third section may have no background noise at all but the lower frequencies of the people talking are suddenly louder. Each section of the audio recording has different characteristics and will need different processes to correctly enhance them.

AUDIO ENHANCEMENT SCIENCE

Understanding the different tools used in both analogue and digital audio editing laid a strong foundation for my career as an expert. For example, what tool should I begin with? What order should I apply the processors to acquire the best results?  Should I start with noise reduction or equalization? Is compression or normalization more applicable to this audio recording? These are important questions to consider when beginning the enhancement process. The plugins I use are based on the critical issues I hear in each section. The order of the processors can be key in producing a clean and balanced work product.

Typically noise reduction will be the first step in the structured approach. This prevents the noise from becoming an issue in further processing. Compression will usually be applied next to raise and balance the level of the section or overall recording. 

Equalization can now be applied to the less noisy, balanced signal. Gates and further compression can also help remove unwanted sound or boost desired sound. While this is a good structure to follow, it may not be right for every situation. If there is excessive background noise, a gate can be helpful before most of the other processors, especially compression. Occasionally equalization is also better as the first executed process.

By drastically cutting a small range of frequencies, unwanted overtones in the human voice can be removed from further processing. Each recording can require any number of processors to reach the desired results; in some cases I may add as many as ten different processing stages before I am satisfied with the results when i am performing audio enhancement.  

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COURTROOM USE

Admissibility of enhanced audio recordings through forensic audio enhancement is often times challenged in courts. The problem is that often times, the integrity of the recording can be challenged if the person performing the enhancements doesn’t maintain the events as they digitally occurred.

Enhancement processes must be applied carefully so that the authenticity of the events is not altered or misrepresented. The amount of frequency reduction throughout a recording must be carefully identified in order to preserve the intelligibility of speech. Our experts understand the dangers to enhancing a recording past it’s authentic limits.

We document all processes and can provide them in report form so that your enhanced exhibits aren’t challenged or misrepresented. This is essentially establishing an authentic chain of custody for derivative work products created.

Not only do we enhance audio and establish a chain of custody, we can also create a forensic transcript when necessary that is signed and certified by an audio forensic expert. This forensic transcript is then used with the enhanced audio evidence to create a packaged piece of evidence that is more powerful than the enhanced audio alone.

If you have an audio recording that you question or need help understanding, please give me a call for a pro bono conversation. I apply my forensic expertise to cases in the United States and many countries around the globe. Any and all formats of audio and video accepted. Retainer agreement available on request; travel expenses will be quoted in advance excluding meal expenses and flat rate time for travel instead of hourly.

Click HERE to email your questions or

Call 800-647-4281 in the USA or +01-248-853-4091 Internationally.

Ed Primeau’s Curriculum Vitae has several references which include cases he has testified in as well as clients he has worked for in these cases.




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