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Posts Tagged ‘Audio Forensic Expert’

Forensic Audio Enhancement -Equalization

Wednesday, July 1st, 2015

Forensic Audio Enhancement -EqualizationForensic audio enhancement is a scientific process. Remove the unwanted sound and increase the wanted sound. In many cases, based on our 34 years of experience, the wanted sound is most always dialogue.

The Use of Equalizers for Forensic Audio Enhancement

An equalizer is one of the most important filters or tools for audio enhancement. This is true for an audio engineer as well as an Audio Forensic Expert. There are many different types of equalizers with different capabilities. The core functions are always the same. Users may increase or decrease sound levels and frequencies. Frequencies that should be considered when performing forensic enhancement are 20 Hz to 20 kHz. All frequencies that fall into that range  are called ‘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.

These tools are crucial when performing a forensic audio enhancement. Noise and other unwanted extraneous frequency content is usually the biggest issue with audio recordings. Equalizers and filters offer the ability to remove narrow ranges of unwanted frequencies so that these unwanted noises can, for the most part, be removed from the recording. This focused process leaves all wanted frequencies like dialogue untouched.

Adobe Audition

One of the software programs we use at Primeau Forensics is Adobe Audition. It comes with the Adobe Creative Cloud Suite. Our favorite filter in Audition is the Multi-band Compressor. A compressor is another type of filter that helps enhance an audio recording to expose wanted sounds and remove unwanted sound. Another company, iZotope, has added some of their filters to Adobe Audition. Their noise reduction filter is also an excellent tool for removing unwanted sound.

Critical Listening Skills

Critical listening skills develop over time and are also referred to as ear training. Each of us has a different perception of sound. In other words, our hearing is unique to each individual. What we hear from a set of speakers or headphones is unique to us as individuals. In order to develop your critical listening muscle, you must experiment and observe. Remember, science is observation.

When using an equalizer, it’s important to be careful to boost or increase frequencies and amplitude (volume) gradually. It is also important to reduce or cut different frequency ranges selectively. This is because some of the time, removing a certain noise that appears to be at a certain frequency may seem to help. However, there could also be a lot of important wanted or voice content in that same frequency range. Making the proper adjustments with an equalizer requires both experience with the equipment, critical listening skills, and a lot of trial and error.

When we process an audio recording for forensic enhancement, we note the types of filtering and associated outcomes in our work notes. Work notes include the various filters applied to a recording, the differences in sound quality and intelligibility. The settings are then noted. Experience, the more time spent and the more audio enhancements that are successfully completed. We are extremely familiar with frequency ranges and improving the quality of audio 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 for audio enhancement 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 require audio enhancement. This is because they are made in poor conditions and have 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 EvidenceDigital Audio 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)

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 work as an audio & video forensic expert, 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 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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18:35 12 Dec 18
I received credentials from two technicians, then a third person ended up doing all the work and kept in touch with me by e-mail. I never saw any proof that the work was done and they told me they found nothing. They could not tell me what was making the noise or the lights. A waste of $750.00.read more
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15:18 27 Aug 18
Ed and his team are great! I took in footage of my boyfriends dog being stolen and they were so willing to take every step possible to enhance the video to retrieve the information we needed. The resolution on our camera/video wasn't great (our fault, not theirs) and they were unable to get the information we needed BUT they guided me in the next steps to take. Thank you guys!!read more
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