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Posts Tagged ‘Audio Forensic Expert’

Forensic Audio Enhancement -Equalization

Wednesday, July 1st, 2015

Forensic Audio Enhancement -EqualizationEqualizers can be one of the most important tools to any audio engineer, and especially an Audio Forensic Expert. There are many different types of equalizers with different capabilities, but the core functions are always the same. Equalizers allow the user to increase or decrease the level of different frequency ranges or ‘frequency bands.’ Each frequency band is typically marked by its center frequency, while the width of the band will vary between different equalizers. Some equalizers even allow the frequency band and the width to be adjusted.

Having these controls at your disposal when performing an audio enhancement is crucial. Noise and other extraneous frequency content is usually the biggest issue with audio recordings. Equalizers and filters offer the ability to remove narrow ranges of frequencies so that these noises can, for the most part, be removed from the recording while leaving other frequencies untouched.

When using an equalizer, it’s important to be careful boosting and cutting different ranges. Sometimes removing a certain noise may sound helpful at first, but there could also be a lot of important voice content in the same range. Making the proper adjustments with an equalizer requires both experience with the equipment, critical listening skills, and a lot of trial and error. The more time you spend working with audio and equalizers, the more familiar you will become with different frequency ranges and how to best go about improving the quality of different recordings.

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

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)

15: A Step-by-Step Approach to Forensic Audio Enhancement

Monday, January 19th, 2015

15: A Step-by-Step Approach to Forensic Audio EnhancementOne of the most common jobs for an Audio Forensic Expert is enhancing a digital audio recording for intelligibility and clarification.  Audio evidence is often recorded in less than optimal situations with poor quality equipment. This evidence can be vital to a case and when the content of the recording cannot be heard, the evidence can become useless.  This is why the audio enhancement process is one of the most important jobs as an Audio Forensic Expert.

There is no one way to enhance an audio recording because every recording is different and will have its own issues that make the enhancement process necessary. At the same time, it is important for the Forensic Expert to be aware of the processes available so they are prepared to handle any enhancement case that comes their way.

Critical Listening

To begin the enhancement process, the Forensic Expert should use critical listening.  Before adding any processing to the audio, they should listen through the recording multiple times and make notes on the issues they hear with the recording.  Noting different sections of the audio and marking these points can be extremely helpful when fixing different problems in the recording.

Diagnostic Tools

Some audio software includes processors that help fix clipping or clicking issues in the recording.  Using this process first will help clean up the audio as much as possible before delving into more advanced techniques.  Noise reduction is also a very helpful process for removing any background noise such that is consistent throughout the recording.

Dynamics Processing

Many recordings I receive have an overall low level to begin with and simply need an increase in gain. 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.

Equalization

Equalization is another extremely helpful tool for audio enhancement.  This will allow the Forensic Expert to remove unwanted frequencies and frequency ranges by varying amounts, as well as boost desired frequencies. When using an equalizer, the Forensic Expert should experiment using their knowledge of frequencies and what they see in the recording.

Now listen in with Audio and Video Forensic Expert Ed Primeau as he discusses the structured approach to forensic audio enhancements.

 

11: Talking Forensics with Audio & Video Forensic Expert Allen Combs

Thursday, November 20th, 2014

11: Talking Forensics with Audio & Video Forensic Expert Allen CombsAllen Combs is an Audio and Video Forensic Expert with over ten years of experience in multimedia work.  He began working as an audio engineer in recording studios and continued working in music production until making the transition into digital media forensics.  When he began his forensic work, Allen was trained by Thomas Owen and in 2010 started his own company, Combs Forensic Services.  Since then, he has worked for numerous clients, including both law enforcement and private citizens, and has gained experience testifying in many of his cases.  Allen is an active member of the American College of Forensic Examiners, the American Board of Recorded Evidence and the Audio Engineering Society.  In addition to these organizations, he is also putting together an audio forensic training course with Dorothy Stout, owner of Resolution Video.

Allen Combs bases his company on integrity, professional expertise and dedication to their clientele.  If you would like to contact Allen or Combs Forensic Services, they can be reached through combsforensics.com or allen@combsforensics.com.

Now listen in as Ed Primeau and Allen Combs discuss the drastically changing market of Audio Engineering, the importance of continuing education in the digital media forensic field, and the challenges that individuals must face when taking on a career as a forensic expert.

 

 

 

 

 

 

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