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What is Forensic Audio Enhancement?

Forensic audio enhancement is the scientific process of clarifying audio recordings using non destructive techniques to preserve speech quality so that the trier of fact can make determinations about the events within the recording. Above all, the goal of forensic audio enhancement is to better hear dialogue by removing unwanted noise. This scientific process of improving the quality of dialogue is also known as speech enhancement or voice enhancement.

Types of Recordings for Enhancement

So you better understand, we perform audio enhancement on a variety of audio recordings. These 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

Enhancement Process

Step #1

Identify the unwanted sounds.

Step #2

Reduce the unwanted sounds.

Step #3

Report observations and opinions.

Forensic Audio Enhancement Method

We apply enhancement techniques to remove sounds like static, furnace and air conditioning fans, hums and other distracting sounds. Therefore, these distracting noises are also known as “unwanted sounds”. Then, once we remove the  unwanted sounds, we can apply audio enhancement processes. These enhancement processes will increase the “wanted sound” like speech. 

Our forensic audio experts apply enhancement services using industry standard equipment that is also used by law enforcement. Above all, this is necessary to improve speech with forensic accuracy. Once the recording is enhanced, it can then be admitted as a clarified exhibit to assist the Trier of Fact. 

Similarly, the same is true for for the audio quality of a video clip. We also perform audio enhancement with video recordings like police dash cameras, body cameras, doorbell surveillance devices (CCTV). That is why we have additional information for your review here how to enhance audio in a video file.

below are some of the processes we use to enhance audio recordings:

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Critical Listening

First, we listen to the recording critically. Critical listening is a skill that is developed over time through training of the ears. It is key for identifying sections of the recording that require audio enhancement.

The critical listening criteria are characteristics in the audio recording which include recording levels, frequency ranges, or signal to noise ratios. We perform critical listening with professional grade equipment. 

This includes monitors (speakers) as well as noise cancelling headphones to ensure the most accurate listening experience. These speakers and headphones MUST be calibrated to the environment the listener is in. 

Equalization - Forensic Audio Enhancement, Voice Enhancement

Equalization (EQ)

After that, EQ can be applied. EQ is a filtering process that can reduce unwanted frequencies or increase wanted frequencies. The EQ process will filter distracting noises first to ensure the highest success of the enhancement.

The EQ process is most commonly done first to ensure that these irrelevant frequencies to not interfere with other processes. Specifically, equalizers are used to filter out hums, buzzes, a/c compressor noise or other unwanted tones that are banded noise.

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dynamics processing

Compression will usually be applied next to raise and balance the volume levels of a given section. Gates and further compression can also help remove unwanted sound or boost desired sound. If there is excessive background noise, a gate can be helpful before most of the other processors, especially compression.

Noise Reduction - Forensic Audio Enhancement, Voice Enhancement

Noise Reduction & De-Reverb

Third, we must remove all types of noises or unwanted sounds. Noise Reduction improves the signal to noise ratio by reducing distracting sounds from a recording. These distracting sounds hinder the speech recognition ability of the listener. Noise removal is the most effective processing technique for voice enhancement.

The noise reduction process uses a noise profile to systematically reduce unwanted frequencies without affecting the dialogue or human voice signals. We also have tools that reduce reverb or echo cancellation.

Enhanced Audio Courtroom Use

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Often times when a lay person processes an audio recording, these changes can effect in a negative effect. For instance, the authenticity of the events change and inaccurate representation of the events makes the recording not admissible in court. This is often times based on changes a non qualified technician makes that alters the sounds in the recording. 

A qualified forensic expert must follow the best practices established by the scientific community. This includes performing the audio enhancement services accurately, documenting the procedures used and presenting the findings to the Trier of Fact. In conclusion, in order to identify dialogue with accuracy, a successful audio enhancement or speech enhancement investigation is essential. 

Our experts are experiencing first hand how the improved speech can assist the Trier of Fact in making difficult decisions. Whether it be a smaller criminal case or a multi-billion dollar civil case. When audio recordings that are difficult to hear are enhanced forensically, they only help the litigation process.