Forensic Audio Enhancement of Gunshot Recordings

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Forensic Audio Enhancement

Forensic Audio Enhancement may be able to reconstruct crime scenes

Forensic Audio Enhancement of Gunshot Recordings

Gunshot audio recordings are like fingerprints. With special forensic enhancement it can provide essential insights to a crime scene. Forensic Gunshot Acoustics is the field of forensics that deals with forensic audio enhancement and analysis of gunshot recordings. Professional forensic experts may be able to reconstruct crime scenes and decipher critical turning points through Forensic Gunshot Acoustics. They use it to decipher the exact location of a gunshot or identify the gun used in firing. These insights can become critical turning points for any criminal proceeding involving a shooting. In the right circumstances Forensic experts can even point out the person who took the first shot in a gun battle and calculate with high precision the exact circumstances in which the shot was fired.

A simple gunshot is a result of complex procedure and produces many audio signals in the process. Initially a confined combustion of gunpowder is used to propel a bullet from the gun. When the bullet leaves the gun barrel, it produces a supersonic jet of gases from the muzzle which leads to a muzzle blast. This muzzle blast creates an acoustic shock wave leaving a highly directional sound. After this the gun itself may produce other mechanical sounds like completion of trigger and cocking mechanism, expulsion of the fired cartridge and replacement with a new cartridge. The other possible audio signals can be of the moving bullet itself and the bullet hitting the target.

There are a variety of factors that can influence the quality of gunshot recordings. Factors such as quality of microphone, angle and direction of the weapon at the time of shooting, environmental effects such as distance, obstacles and reflecting surfaces between the recording device and gunshot, can negatively affect the quality of recording. Other factors influencing the sound waves of a gunshot include effects of wind, temperature, humidity and surrounding objects. With professional Forensic Audio Enhancement we can improve the quality of gunshot recordings and provide valuable insights to the crime scene.

Forensic Audio Enhancement Techniques

Audio Forensic experts use a number of filters or processes to enhance the quality of forensic audio recordings. Depending on the type of disturbance or noise the appropriate filter is used. Here is a quick list :

  1. Sample Rate Correction is applied to digital audio recordings which are distorted while copying to a CD using incorrect sample rate conversions.
  2. Highpass filter is an analog filter used to reduce noise below a certain frequency, such as engine noise or rubbing of clothes against a microphone.
  3. Lowpass filters are used to reduce high frequency noise such as a hiss or wind noise.
  4. Notch filter is an analog filter used to reduce noise of specific frequencies such as constant humming.
  5. Comb and Multiple Notch filter is an analog filter used to reduce noise at multiple specific frequencies like irregular and multiple hums or tones.
  6. One Channel Adaptive filter is applied to reduce repetitive and predictable noise from machines, varying tones, reverberations and echoes.
  7. Two Channel Adaptive Filter is used to reduce repetitive and predictable noises from reference sources such as music or TV noise.
  8. Specific Inverse Filter reduces repetitive and predictable disturbances such as those from machines, hums and tones.
  9. Adaptive Spectral Inverse Filter is used to reduce noise from machines, tones, reverberations and echoes.
  10. Noise reducer filter is used to reduce difficult to predict noises such as clicks, pops or other random noises.
  11. Graphic Equalizer filter is used to improve speech intelligibility.
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