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audio enhancement

Audio Enhancement and Clarification


Do you need an audio recording enhanced so that you can hear what is being said and by whom?

We’re happy to examine your recording to give you an idea of the costs and the final quality of the enhanced audio.

  • Send us the audio file and we’ll examine it at no cost.
  • We’ll send you a portion of the audio that we’ve enhanced so you can hear the improvement for yourself.
  • We’ll also provide you with a no-obligations quote to have the entire audio recording enhanced.

What is Audio Enhancement?

Audio enhancement refers to the scientific process of improving the clarity of audio recordings to increase intelligibility, listenability or audibility.

Audio enhancement normally involves isolating, removing or filtering unwanted sounds and noise from the recording, as well as manipulating frequency, amplitude and other characteristics of sound.

What is produced after enhancement is not a newly created recording, but a more litenable and more understandable version of the original recording. Desired sounds or voices would be more easily identifiable and distinct, and spoken words would be more comprehensible and clear.

Audio evidence is often recorded in less than ideal conditions and with poor quality equipment. This evidence may be vital to a case, but when the content of the recording cannot be clearly heard then that evidence might be useless.

Audio Enhancement Techniques

Critical Listening

Critical Listening

The audio enhancement process will begin with critical listening. An audio forensic expert will listen to the recording a number of times, carefully noting areas of interest or concern, issues related to audiblity or legitibility, any anomalies, and other facts of significance to the enhancement process.


Clipping or clicking issues can usually be fixed using signal processing or more accurately, using the processing capability of forensic audio software. Noise reduction processing can often remove background noises or at least render them consistent throughout the recording. A variety of filters can be applied to enhance the recording, bringing out specific aspects or events contained in that recording.
Spectrum Analysis

Spectrum Analysis

Noise and other interference can be analyzed by a spectrum analyzer and the corresponding frequencies reduced so that these noises are less noticeable. Similarly, sound of interest can be isolated and amplified so that it is more easily heard.


Highly precise equalizers can be used to boost or cut specific bands of frequencies. To help make speech more intelligible, the frequency band containing most speech content, 200Hz–5000Hz, can be amplified or isolated.


Faint sounds in the recording can be boosted by compressing or leveling the signal so that the dynamic range of the material is reduced, making soft sounds more apparent. Compressors as well as gain plugins can help raise the overall level of the recording. Compression will also help balance all of the signals in the recording.

To accomplish enhancement, the most common process is to follow these steps:

  • Reliably digitize audio recordings onto a computer system, typically in WAV (lossless) or MP3 (lossy) formats.
  • Filter out hiss, click and pop sounds. This is common with recordings that may have suffered partial data loss with age.
  • Block out or quiet ranges and specific frequencies (such as 60Hz wall power, and its multiples, within the USA and Japan).
  • Isolate unwanted constant tones or patterns and then removing those items from across the entire recording.
  • When the recording is in stereo, reference the channels to each other to perform directional noise cancelling.
  • Normalize voices so that each audible person is heard at equal volumes.
  • Smooth sounds that border nearly inaudible gaps. These gaps include those created during the filtering process.
  • Prepare a transcript of audio and words heard
  • Testify in court about the enhancement done and the audio and words heard

Audio Enhancement Course

An online certificate course that is ideal for private investigators, attorneys, forensic practitioner and anyone who would like to become an audio forensic specialist.

What you'll learn

  1. Introduction to Audio Forensics
    1. Forensic Fundamentals
    2. Audio Forensics Principles
    3. Admissibility of Audio Evidence
  2. Foundations in Audio Engineering
    1. Sound and Acoustics
    2. Audio Recording Flow
    3. Sound Digitization
    4. Digital Signal Processing
  3. Digital Media and Evidence Recovery
    1. FTK
      1. Bit Stream Imaging
      2. File Carving
    2. WinHex
      1. File Repair
  4. Forensic Audio Enhancement
    1. Noise Reduction
      1. Digital Filters
      2. Spectral Subtraction
      3. Adaptive Filters
    2. Stereo Source Separation
      1. Real-Time Processing
      2. DC Live
  5. Practice and Discussion
    1. Evidence Seizure and Acquisition
    2. Enhancement Practice
    3. Notes and Report Writing
    4. Preparation of Enhanced Material

What it costs

Cash Price (once-off)R 1,500.00
Monthly (12 months)R 200.00

Payment options


Looking for new challenges in the field of audio forensics?

Intertel is anything but ordinary, and so is the work that we do. Interesting, challenging and rewarding work is what you can expect.

We’re not just looking for people with the requisite technical skill, qualifications and work experience… we’re looking for innovative and resourceful professionals with excellent communication skills, meticulous recordkeeping habits and flawless attention to detail.

You’ll need to have a logical mindset, yet also be capable of abstract and creative thinking, in order to resolve complex technical issues under pressure.

You must be able to work collaboratively and productively with others yet feel at home and confident handling tasks on your own.

If this describes you, then you’ll fit right in, and we’d love to start a conversation with you about a successful career at Intertel.

Specialized, and relatively expensive, audio processing and analysis software, filters and plugins are essential for forensic audio enhancement and clarification. A private person wanting to enhance an audio recording would be better off paying a forensic company for a once-off service, than spending tens of thousands of Rand on software that might only be used once.

A handful of free, open-source products have emerged in recent years, and are gradually becoming more accepted as useful tools by the audio forensics community. These free products are often capable of enhancing audio recordings, but generally require a greater level of knowledge and skill to use effectively.

Below we list our favorite audio forensic software. Prices are estimates based on the exchange rates at the time of writing. The “buy now” link will take you to that product’s checkout page where the current, correct price will be displayed.

ProductPrice (ZAR)More info Purchase
Diamond Cut Forensics 10R 29,999.00Get more infoBuy now
iZotope RX 5 AdvancedR 29,999.00Get more infoBuy now
Acon Acoustica 6 R 23,999.00Get more infoBuy now
Avid Audio Suite R 19,999.00Get more infoBuy now
DAC QuickEnhance R 13,999.00Get more infoBuy now
Ozone 7 Advanced R 9,999.99Get more infoBuy now
DCVST Automatic Forensics Adaptive FilterR 7,999.00Get more infoBuy now
CEDAR Trinity™ price on requestGet more infoRequest price
Ocean Systems dTective price on requestGet more infoRequest price
Audacity freeHome pageDownload
WaveSurfer freeHome pageDownload