What is Forensic Audio Enhancement?

When attorneys are looking for audio forensic services in New York, they turn to Al Zlogar Forensics Inc. Forensic audio enhancement is the process of providing the highest quality recording that allows the Trier of Fact to hear the critical acoustic events better.

Al Zlogar Forensics provides forensic audio enhancement services using the tools accepted in the scientific community like iZotope RX. iZotope RX has filters that still amaze us. For example, De-Reverb removes the excess room tone that interferes with the intelligibility of the words spoken. In addition, we also use Adobe Audition, another program often used for forensic audio enhancement services. We provide forensic audio enhancement services in New York and other cities around the country.

Along with forensic audio enhancement, we also provide forensic audio authentication services.

Critical Listening

The audio forensic technicians at Al Zlogar Forensics begin all forensic audio enhancement by listening critically to the audio evidence. The critical listening process allows the technician to identify, analyze, and document the time, frequency, and amplitude content to characterize the types of distortions or noise masking the target signal.

You would say that this recording has a low signal-to-noise ratio. A signal-to-noise ratio is a value between the wanted signal and interferences/distortions that mask the target signal. A poor recording has a quiet target signal and an abundance of noise interfering with that signal. Our goal is to forensically enhance the target audio so that the Trier of Fact can better understand the value of an evidence recording.

The audio enhancement process typically results in a higher signal-to-noise value. Additionally, the enhancement process aims to improve the intelligibility of voice information and reduce the unwanted sounds that interfere with voice information.

Listen to before and after forensic audio enhancement recordings taken from actual cases.

Enhancement Software Tools:

forensic noise reduction
Forensic noise reduction
an alternative to compression for forensic audio enhancement
Adobe Audition’s Multiband Compressor

Suggested read: Three tips for forensic audio enhancement.

Do you have Unwanted Noise and Interference in your recording?

When performing a forensic analysis of voice recordings, identifying the category of noise helps the technician use the correct filters to further improve the intelligibility of the recording. There are four classifications of noise:

Tonal Noise

This category of noise occurs from cell phone tones or vibrations, electrical power hum, and acoustic noise from machines oscillating around a specific set of frequencies.

Before Enhancement

tonal noise spectrogram
A visual representation of tonal noise before forensic audio enhancement processing
Listen to the tonal noise before forensic audio enhancement processing

After Enhancement

forensic audio enhancement services
A visual representation of tonal noise after forensic audio enhancement processing
Listen to the tonal noise after forensic audio enhancement processing

Continuous Broadband Noise

Broadband noise spreads across a broad range of frequencies. Visually, continuous broadband noise will appear as the salt and pepper signatures on a spectrogram. Examples include air conditioning units, ventilation systems, machine noise, and tape hiss.

Before Enhancement

spectrogram display of continuous broadband noise
A visual representation of continuous broadband noise before forensic audio enhancement processing
Listen to the continuous broadband noise before forensic audio enhancement processing

After Enhancement

spectrogram display of continuous broadband noise
A visual representation of continuous broadband noise after forensic audio enhancement processing
Listen to the continuous broadband noise after forensic audio enhancement processing

Variable Broadband Noise

Examples of variable broadband noise include wind, rain, background traffic in cities, television, and additional voices in the background. These interferences occupy a broad range of frequencies with varying pitches.

Before Enhancement

spectrogram display of variable broadband noise
A visual representation of variable broadband noise before forensic audio enhancement processing
Listen to the variable broadband noise before forensic audio enhancement processing

After Enhancement

spectrogram display of variable broadband noise
A visual representation of variable broadband noise after forensic audio enhancement processing
Listen to the variable broadband noise after forensic audio enhancement processing

Convolved Noise

Convolved noise is having too much reverb in a recording. Examples include recordings in large rooms, hallways, and any space with reflective acoustic materials.

Before Enhancement

spectrogram display of convolved noise
A visual representation of convolved noise before forensic audio enhancement processing
Listen to the convolved noise before forensic audio enhancement processing

After Enhancement

spectrogram display of convolved noise
A visual representation of convolved noise before forensic audio enhancement processing
Listen to the convolved noise after forensic audio enhancement processing

Suggested Reading: Forensic Analysis of Analog Audio Tape