Forensic audio enhancement services are the scientific process of clarifying audio recordings using non-destructive techniques to preserve speech quality. This is crucial for the trier of fact can make determinations about the events within the recorded evidence. Above all, the goal of forensic 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.

Play Video

Enhancement Process

Step #1

Identify the unwanted sounds.

Step #2

Reduce the unwanted sounds.

Step #3

Report observations and opinions.

Types of Recordings for Enhancement

So you better understand, we perform 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
  • Voicemails

Forensic Enhancement Method

Audio Forensics Expert applies 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 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 the audio quality of a video clip. We also perform enhancement to the audio within 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:

forensic audio enhancement

Critical Listening

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 voice enhancement. In most investigations, we are performing critical listening to analyze speech in an evidence recording. 

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. 

Similarly, 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. 

audio enhancement equalization

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.


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.

audio authentication analysis

Noise Reduction & De-Reverb

Lastly, 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

forensic audio enhancement in court

Often times when a layperson processes an audio recording, these changes affect the recorded evidence in a negative way. For instance, the authenticity of the events change and an inaccurate representation of the events makes the recording inadmissible in court. This is often 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 order to identify dialogue with accuracy, a successful enhancement or voice enhancement investigation is essential. Our expert witness testimony communicates these results in an accurate way to the Trier of Fact. 

In conclusion, our client’s experience will experience how improved speech can assist the Trier of Fact in making determinations. 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.