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Posts Tagged ‘Audio Recordings’

21: Audio Enhancement – Compression

Thursday, May 28th, 2015

21: Audio Enhancement - CompressionAs an Audio Forensic Expert, knowing what tools are available to me and how they work is extremely important. While compressors are often thought of as tools for music production, they serve many functions in the Audio Forensic world. Like with most audio signal processors, it takes training and experience to operate compressors properly and effectively when enhancing audio.

When an audio enhancement is required, the recorded signal is often very low, or the desired source is unbalanced, with other signals in the recording. Compressors can increase the gain of a recording while also balancing the levels of the sound sources. While different compressors will vary, most have the same basic controls. These include the threshold, attack, release, ratio and makeup gain.

It is easy to focus on raising the level of the desired signal with a compressor and produce a loud, but unintelligible work product. Sometimes a smaller amount of compression may have a more positive effect on the audio. An experienced Audio Forensic Expert will know how to effectively clarify the recording based on his or her knowledge of audio and signal processing.

Now listen in with Audio and Video Forensic Expert Ed Primeau as he discusses the use of compressors in forensic audio enhancements.

Audio Enhancement – Noise Reduction

Friday, April 3rd, 2015

Audio Enhancement - Noise ReductionMost recordings that I come across as an Audio Forensic Expert are made in poor condition and their biggest problem is an abundance of noise. Though there are many ways to reduce the noise floor in a recording, there is no guaranteed method. The noise floor can be defined as a sum of all of the unwanted signals in a sound source. This will include any background noise in an environment such as cars driving by, televisions or radios, or even other people besides the desired person speaking.

When reducing the noise is the best option, there are two common ways to do so in most audio editing software: noise reduction processing and filtering or equalization. Both processes have benefits and side effects when used to remove noise from a recording.

The most important thing to remember when removing noise from a recording is that the goal is to enhance or clarify the desired signal. Every audio recording is different, and as an Audio Forensic Expert it is my job to analyze and process each recording as needed. It takes training and experience to recognize what a recording needs in order to enhance or clarify it effectively.

Now listen in with Audio and Video Forensic Expert Ed Primeau as he discusses the use of noise reduction in forensic audio enhancements.

photo credit: Neve Compressors via photopin (license)

17: How to Make Digital Audio Evidence

Thursday, February 12th, 2015

17: How to Make Digital Audio EvidenceAudio evidence can often be one of the most important pieces of evidence for a case, so it should always be given a great deal of attention. I’m going to cover some tips on how to create the best audio recording possible, whether it’s a police interview, a concealed recording or anything in between.

One of the most common ways people create digital audio evidence is by using digital audio recorders. Law enforcement will often use them for interrogations and confessions, and sometimes even out in the field as a backup for their dash cam or body cam audio. People outside of law enforcement use them for creating audio evidence as well.

Tips on Creating Digital Audio Recordings

  1. Choose settings on the digital recorder that optimize the quality of the audio and optimize the amount of space on the recorder.
  2. Listen and note any extraneous noise present in the area before making the recording. If at all possible, remove this sound or find a way to work around it.
  3. Get as close to the desired sound source as possible when creating the audio recording. The closer the microphone is to the sound source, the better the level of the desired signal will be.
  4. Make sure the digital audio recorder is in an optimal location. Make sure that the microphone is facing the subject and that the recorder is relatively stable to avoid extra noise. If possible, use an external microphone to get better quality audio.
  5. Always create a test recording before the actual recording. Listen back carefully and adjust the settings of the recording and the location of the recorder to make sure it is capturing the highest possible level in the best quality.

Now listen in with Audio and Video Forensic Expert Ed Primeau as he discusses the best practices for creating digital audio evidence.

photo credit: Ready to record! via photopin (license)

 

 

 

 

 

 

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