Archive for the ‘Audio Enhancement’ Category

Audio Enhancement – When Do It Yourself Won’t Work

Friday, April 29th, 2016

audio engineer 1243600 - Audio Enhancement - When Do It Yourself Won’t Work

Can an audio recording be enhanced? Forensic audio enhancement is a process of removing unwanted sounds and preserving the wanted sound. Unwanted sounds include static, HVAC fans, hums and other distracting background noise. The goal is to reveal or uncover the dialogue, conversation or ‘wanted’ sound in an audio recording.

The question is ‘can a recording be enhanced?’

Perhaps you have tried to use ‘Audacity’ to enhance the recording yourself. This does not always work especially when you consider the training and experience an audio forensic expert has.

Forensic audio enhancement helps reveal conversations as they occurred. There are also times when an audio enhancement is unable to clarify the dialogue. The only way to tell is to test the recording in an audio forensic lab. At Primeau Forensics, we call this a preliminary analysis.

What type of recording do you have: analog and digital?

Analog recordings are those that have been created using some type of tape recorder, like a cassette tape. They may be old and likely have lost some of their audio fidelity. Tape noise and hiss may also be present, which are further examples of unwanted sounds. Analog tape also has a short shelf life, usually 25 years, which quickly degrades the quality of analog recordings.

When audio forensic experts enhance analog recordings, the primary goal is to restore the lost or wanted sounds such as the dialogue. A secondary goal that is accomplished through this process is the transfer of the audio recording to a digital format in a forensically sound manner. This ensures that no further degradation will occur to the file and provide a duplicate of the recording that is acceptable in court.

Digital recordings are audio recordings that have been created on a digital recorder, no cassette type of tape is involved. Digital recorders capture the recordings on an internal chip or removable storage device like an SD card. In this case, the primary goal of the audio forensic expert is to remove any unwanted sounds from the recordings. The audio forensic expert will also preserve an exact duplicate of the evidence recording for their own records and for the court.


After 34 years of practicing as an audio forensic expert, my team and I have successfully enhanced hundreds of poor quality audio recordings to be used in litigation’s. We have been extensively trained in forensic audio enhancement. We have completed and testified in dozens of cases and courts about my forensic enhancement, and know the best tools to use for the forensic audio enhancement process.

Give us a call to learn more about our forensic audio enhancement services. 800.647.4281 or email

Forensic Audio Enhancement: Removing a Single Sound

Monday, August 24th, 2015

sound board 1416985 - Forensic Audio Enhancement: Removing a Single SoundOne of the most common audio issues with audio enhancement is noise. Noise and other extraneous ‘unwanted’ sounds make up the noise floor in a recording. Unwanted sounds interfere with the wanted sounds. Removing the unwanted sounds and raising the intelligibility of the wanted sounds is audio enhancement.

A noise floor is usually consistent throughout the recording and can be removed to varying degrees by a trained audio expert using  software.

Non Continuous Sounds

The most complicated issues are the unwanted sounds that are not continuous. These sounds could include anything from a plane flying overhead to someone whistling while people talk. It is harder to pinpoint these sounds. A spectrogram is used so the audio expert can see and hear the unwanted sound allowing the expert more options for removal.

Use of a Spectrogram

A spectrogram shows both the frequency content of a recording and the level of those frequencies over time. It may be the most helpful tool to an Audio Expert because it presents all sound throughout the recording in one view. The spectrogram allows the expert to identify and address individual unwanted sound in the recording. With the right software, these individual sounds can be selected and removed without affecting any other part of the recording. It is important to remember that there is a right and a wrong way to do this, which is why only a trained Audio Forensic Expert should be hired to complete an enhancement for use in court.

The Role of Artifacts

When processing audio, it can be easy to introduce artifacts to the recording. Artifacts are unwanted noise that is produced from various processing and compression techniques. Considering the goal of an audio enhancement is to eliminate extraneous noise, introducing artifacts is the exact opposite of what you want when working with a recording. Many things can introduce artifacts, but the simplest way to describe the cause is over processing. By over processing, I mean using extreme settings within individual audio tools.

For example, I often work with audio evidence that is extremely quiet. This often requires a gain increase of portions where only voice content exists. If the gain is increased too much, it can cause clipping of the audio output. When this occurs, the edges of the waveform are essentially clipped off, producing a distorted and noisy audio signal. The end result is a less intelligible voice than the original, essentially defeating the purpose of the whole process.

Avoiding Artifacts

When adjusting individual ranges of frequencies on the spectrogram, it is very important to be aware of artifacts. Being able to recognize artifacts and know the limitations of what processing can be done is what makes an Audio Forensic Expert necessary. When isolated portions are processed with a trained ear and the right knowledge, noise can be eliminated and voices can be brought out without introducing any artifacts.

I recently worked on an audio recording that had a siren present during a portion of talking. Because it was so loud, it made the underlying dialogue difficult to hear. Luckily, the siren could be isolated in the recording. By selecting only the siren and then decreasing the gain a moderate amount, the voices became more audible while still avoiding any artifacts.

Audio Forensic Experts have a plethora of tools at their disposal, which is making audio enhancements more and more effective. There are some things to be cautious of when enhancing audio. This is determined on a case by case basis. Any technique that is taught in training should be used as long as the technique is accepted in the scientific community.

Call us with your questions on audio enhancement and ask about our preliminary analysis 800.647.4281

Ted Rall and the L.A.P.D – What Really Happened?

Thursday, August 20th, 2015

police motorcycle 1449727 - Ted Rall and the L.A.P.D – What Really Happened?

On May 11th, 2015, Los Angeles Times Freelance Political Cartoonist Ted Rall published an Op-Ed relating to an incident he allegedly faced with the LAPD back in 2001.

Rall claimed while being stopped for jaywalking in Los Angeles, an officer of the Los Angeles Police department assaulted him. Rall included descriptions of the officer throwing his driver’s license into the sewer, being thrown up against a wall, and being handcuffed. Rall went on to describe a crowd of onlookers surrounding him during this event, asking officers about the legitimacy of the arrest.

In response to the post, the Los Angeles Police Department presented a 14-year-old recording of the event. Based on this recorded evidence, Rall was fired from the L.A. Times. Since then, Rall has disputed the LA Times and has produced both an enhanced version of the audio and a transcript of what he believes can be heard in the recording.

The L.A. Times commissioned Primeau Forensics to perform forensic audio enhancement on the audio recording provided by the L.A.P.D. The audio evidence was analyzed with the goal of uncovering the events as they occurred. Primeau Forensics holds no bias toward either party and approached the investigation as such.

You can hear the enhanced audio recording here:

Read the Primeau Forensics’ transcript of the confrontation here.

black - Ted Rall and the L.A.P.D – What Really Happened?

Audio Forensic Synchronization – What Happened When?

Wednesday, June 24th, 2015

Audio Forensic Synchronization  - Audio Forensic Synchronization – What Happened When?Generally speaking, any device that captures video is also capable of simultaneously capturing audio. This audio can be crucial to the Forensic Expert, as it can show the expert more clearly “what happened when,” when it comes to a crime scene.

Picture this: a young man has just assaulted an older woman, and a police officer is in pursuit. As the young man begins to run from the police, another man on the street begins shooting video from his smart phone. The police officer is recording from both the police-car dash-cam, along with a body-worn camera, which he switched on when he began his pursuit.

As the young man continues to run, the officer announces “Taser!” and fires, activating the camera built into the officer’s stun gun. After sprinting around a corner, the young man is found dead. How did this happen? Who was responsible? When did the death occur? This is where audio can come in major handy.

As the appointed Audio Forensic Expert, you are tasked with determining what you believe happened in this situation. The evidence available to you includes the smart phone video from the witness, the police officer’s dash-cam, the on-board camera from the taser, and the body-worn camera.

This is where the video as well as audio is valuable to the investigation. An audio forensic expert can synchronize the audio in chronological order. Forensic audio enhancementcan help hear the events that occurred and remove any unwanted sounds to help synchronize the recordings. Begin with the event that took place the earliest. In this case, it would be the police officer’s dash-cam, as it is always running. Next, find the portion of audio that starts the witness’ footage. Listen for a certain sound or yelled phrase for reference, and when you find that sound source from the officer’s dash-cam video, you’ll know that this is where the witness began recording.

This can also be done by visually inspecting the waveform. Large, quick spikes in the level can make it very easy to quickly sync the audio. Most software will also allow you to zoom in closely on the waveform so you can line the waveform up as closely as possible.

Next, you’ll want to find the point where the body-cam began recording. Again, this will require critical listening and visual analysis to align the sounds from the body-cam evidence and the witness video to get an idea of when the officer began recording.

From there comes the last piece of evidence: the taser camera. Remember when the police officer announced “Taser”? Well, the second the trigger on that stun gun is pulled, the in-board camera kicks on. The body-camera audio will give you an idea as to when the officer announced his taser use, along with when the video clip begins.

This will give you the most accurate occurrence of events. The actions of the taser camera are the most recent recording of the event, and in it you notice a loud sound that couldn’t be heard in the other recordings. That sound was the sound of a pistol, which another officer around the corner pulled out to shoot in an attempt to detain the criminal. This is what the body-camera, witness video and dash-cam, did not see. However, due to the alignment of the audio, the expert is able to see, in chronological order, the events as they occurred.

Synchronization does not always go so smoothly. Sometimes different frame rates are used in different videos, which can alter the speed of how the different videos play back. Most modern digital recording technology is self resolving and does not have this issue, but there are still devices that do not. These can cause the video and audio to be in sync at one point, but slowly drift apart throughout the video. It’s important to be aware of this so scientific adjustments can be made to make sure that all the events are synchronized as accurately as possible.

The audio makes it much easier to synchronize all of the pieces of evidence together. Some of the time the audio must be forensically enhanced in order to better hear the events as they occurred. The audio can provide both auditory and visual cues, through viewing the waveform, to use as reference points so an accurate sync can be completed. With only video, the different perspectives and qualities would make it extremely difficult to find exact reference points to line up.

Not all cases will give the expert this much to work with, but when working with multiple clips of the same occurrence, having a critical ear can be invaluable to understanding the timeline of the situation. Video can be powerful, but its direct counterpart, audio, can be essential to finding the cause of confusing and misleading investigations.

The Structured Approach to Objective Audio Enhancement

Wednesday, July 9th, 2014

973270 21740966 300x194 - The Structured Approach to Objective Audio EnhancementThe audio enhancement processes that I have learned are some of the accomplishments of which I am most proud as a forensic expert. Audio enhancement is both an art and a science; and as an audio forensic expert with 30 years of experience, I can tell you with confidence that no two assignments are the same. This knowledge has helped me develop a structured approach to objective audio enhancement.

In the following post I would like to help you better understand proper audio enhancement techniques through an objective and structured approach. On average, I enhance between 200 and 300 audio recordings per year. For each assignment, I use the knowledge and skills I have gained from past experiences to effectively enhance the recording. I believe I have developed a strong understanding and talent for audio enhancement.

When I first receive an audio recording from a client, I begin my enhancement process by listening through the recording several times. Critical listening is key for identifying different sections of the recording. When I refer to sections, I mean portions of the audio that have different characteristics such as levels, frequency ranges, or signal to noise ratios. For example, the first section may have two people talking quietly with a lot of street and car noise in the background. The next section may have a more audible conversation with a train passing far off in the distance. The third section may have no background noise at all but the lower frequencies of the people talking are suddenly louder. Each section of the audio recording has different characteristics and will need different processes to correctly enhance them.

Most audio editing software allows you to add a marker to the timeline based on your cursor’s current location. During playback, using a hotkey relative to the software, I can add markers while listening through the recording in order to identify the in and out of each section. This can ensure that I do not use a processor that may hinder other portions of the audio. Once the sections have been established, I can apply different plugins to each section as needed. 

Understanding the different tools used in both analogue and digital audio editing laid a strong foundation for my career as an audio forensic expert. For example, what audio enhancement tool should I begin with? What order should I apply the processors to acquire the best results?  Should I start with noise reduction or equalization? Is compression or normalization more applicable to this audio recording? These are important questions to consider when beginning the enhancement process. The plugins I use are based on the critical issues I hear in each section. The order of the processors can be key in producing a clean and balanced product. 

Typically noise reduction will be the first step in the structured approach. This prevents the noise from becoming an issue in further processing. Compression will usually be applied next to raise and balance the level of the section or overall recording.  Equalization can now be applied to the less noisy, balanced signal. Gates and further compression can also help remove unwanted sound or boost desired sound. While this is a good structure to follow, it may not be right for every situation. If there is an exceptional amount of background noise, a gate can be helpful before most of the other processors, especially compression. Occasionally equalization is also better as the first executed process. By drastically cutting a small range of frequencies, unwanted overtones in the human voice can be removed from further processing. Each recording can require any number of processors to reach the desired results; in some cases I may add as many as ten different plugins before I am satisfied with the results.  

Many of our clients at Primeau Forensics will say that they attempted to enhance their audio recording on their own and were unsuccessful. I explain that the audio enhancement process requires experience as well as a structured, scientific approach in order to produce effective results. Audio editing software is only a tool used in the enhancement process and owning a program does not give you the experience and skills necessary to enhance audio recordings like a professional.  

The structured approach to objective audio enhancement comes from experience. It is based on years of ‘hands on’ work with audio enhancement as well as observing sound recordings and the critical issues that interfere with the desired sounds. Please contact Primeau Forensics for your free consultation.  


An Affordable Approach to Audio Enhancement

Tuesday, June 10th, 2014

An Accurate and Affordable Approach to Audio Enhancement

The audio enhancement process is the number one forensic activity at Primeau Forensics. Audio enhancement, or sound enhancement, questions and assignments come into our offices daily from around the world. Audio enhancement helps people better understand words that were recorded but not clearly heard.

Last November I was asked by Jeff Morley to combine two versions of the Air Force One recordings from the day John F Kennedy was assassinated. Once my team and I had the recordings combined, the next step was to work on the enhancement process. 

As an audio forensic expert, audio enhancement is one of my favorite forensic activities. This is likely because when I started my career as an audio engineer, one of my first assignments was with the FBI. The experience was extremely rewarding because the two Detroit agents that came in to our recording studio, Ambience Recordings, were very appreciative and complimentary. I took an audio recording and used tools to reduce the unwanted background noise and enhanced the speaking portion of the recording. 

Audio enhancement is both an art and a science. It is an art because as forensic experts, we have tools like noise reduction, equalizers and compressors we use to create with similar to an artist who has paint, brushes and a canvas. We use these tools and artistically repair sound from sounding poor to enhanced and clear to better understand the speaking portion of the recording. 

Audio enhancement is a science because the tools have to be scientifically calculated and applied in specific orders depending on the experimentation with the order of application and the results from each application. I find myself using ‘control Z’ quite often during sound enhancement processes. 

Clients from around the world, including police departments and private individuals,  use digital pocket recorders to document and preserve a confession or other event in order to refer back to that event at a later date. The problem is that some of the time their recording does not go as planned. Background noise interferes more than planned because recorders pick up unwanted sound. Digital audio recorders do not record in the same manner that our ears perceive sound. When the digital pocket recorder is taken back to have the recording downloaded to a computer, the unwanted background sound is much more obvious then when the recording was created.

This is where our services as an audio forensic expert are sought out. After 30 years, we have become quite good and pretty quick at enhancing audio. Our speed and accuracy saves our clients money because many forensic experts take long periods of time applying various tools by trial and error. We, on the other hand, have the ability to recognize a noise situation and determine the order of processing necessary for audio restoration in a short period of time. 

In fact, we have started a service that accommodates our clients financially. Clients often have much higher than normal audio enhancement expectations. They hope the impossible can be made possible. Even the best forensic experts at Primeau Forensics cannot restore all sound to our client’s expectations.

This is why we have implemented a preliminary investigation process. This process allows us to send a sample of the restored recording to our clients to show them what is and is not possible. That way we can learn for a lesser rate if we can meet their expectations for audio enhancement. I am proud to say that in many cases we meet and even exceed their expectations. 

Audio Enhancement – A Forensic Approach

Friday, April 25th, 2014

363947977 c785e57def o 300x169 - Audio Enhancement - A Forensic ApproachAudio Enhancement – A Forensic Approach

Most people searching for audio enhancement are looking for a solution to better hear a poorly recorded audio conversation. There are two ways to look at audio enhancement, from a recreation standpoint and a business/legal standpoint. The audio recording may or may not be a very important piece of audio evidence.

The term “audio enhancement” can be used for a couple of different situations. First, with regard to ‘enhancing’ the quality of the listening experience – let’s call this ‘passive’ audio enhancement, since the goal is simply to enjoy a recording in the best possible environment. To better hear a poorly recorded audio recording. I am an audiophile; I love great sound when I listen to music. In that regard, audio enhancement is the activity of choosing the right equipment, careful placement of the speakers, careful placement of the furniture and taking your time gently balancing the equalization and stereo imaging.

Audio enhancement also helps a sound projection situation in sounding the best it possibly can. These situations can include a church service, professional speaker seminar, live concert, symphony or even a drive in theater. Yes, I believe drive in theaters will make a comeback.

In this situation, audio enhancement involves choosing the right speakers, then identifying the perfect placement for them with regard to sound source and audio ratio to audience. Live sound audio enhancement also involves activity as outlined in the previous example, like balancing the equalization and stereo imagery.

Audio enhancement for forensic applications, also known as forensic audio enhancement, also has similar activity as outlined in the previous samples – we’ll call this ‘active’ audio enhancement, since we are actively manipulating the quality of the recording itself in order to clarify what is being said. This activity requires a much more sanitary environment. An audio forensic lab is acoustically tuned and well stocked with the finest hardware and mind boggling software. This software is used in a specific order that is defined by each individual enhancement situation or court case.  With regard to audio enhancement for forensic applications, it is the skill of the audio forensic expert that makes or breaks audio enhancement success.

After 30 years of enhancing audio forensically, we are often asked by clients why our success rate is so high. I tell them that we began their enhancement process by analyzing the various reasons why their audio recording was so poor. Was it because background noise was louder than the desired conversation? In this case our goal is to clarify a recorded conversation. The audio forensic expert then determines whether to remove background noise first or boost the overall volume. With some cases the audio expert may apply other filters first like equalization, compression or re-sampling in order to better hear the words spoken.

There are free software programs available that do a pretty good job enhancing recorded conversations to better hear a poorly recorded audio recording. Primeau Forensics recommends an audio software program called ‘Audacity.’  Audacity has equalization, format conversion and some similar processes and filters that other professional software programs have that we use at Primeau Forensics, like Adobe Audition. This is one approach if funds are low.

The problem then becomes maintaining a chain of custody. If your recordings are to be used in court, establishing a chain of custody is extremely important. It does not look good to the other side when you use a software program yourself. This is why most people in need of audio enhancement seek assistance with a company like Primeau Forensics.  Not only do we enhance audio and establish a chain of custody, we also create a forensic transcript when necessary that is signed and certified by an audio forensic expert. This forensic transcript is then used with the enhanced audio evidence to create a packaged piece of evidence that is more powerful than the enhanced audio alone.

We have experienced situations where the playback systems in court, as well as the reverberate acoustics, make it difficult to hear the enhanced audio recording. When the enhanced audio recorded evidence is accompanied with a certified forensic transcript, the judge and jury can read along with the transcript. It allows the court to better hear the enhanced recording.

Generation Loss in Analog and Digital Recordings and Audio Forensics

Thursday, January 2nd, 2014

3101873296 eaf94446fb o 300x225 - Generation Loss in Analog and Digital Recordings and Audio ForensicsIt has become very easy to download and share music with friends. As an audio forensic expert, I am often asked why music loses quality when transferred from one person to another. In the following post I will share some explanations about generation loss, file format conversion and the relevance to audio forensics enhancement and authentication.

Back when I used to make 8-track and cassette copies of my record albums to listen to in my car or share with friends, the 8-track and cassette copies were considered first generation copies and sounded pretty good. When a copy was made from the first generation copy to create a second generation copy, it did not sound as good. This is because of ‘generation loss’. Although this is true for analogue recordings, it also is true for digital recordings.

Format conversion is a contributing factor to generation loss in 8-track to cassette analogue copies as well as CD to CD transferring. When a digital copy of a compact disc is created, the operator must pay careful attention to the copying process. It is very easy to change the format of the digital audio file without knowledge which will cause generation loss.

If the original CD which is a .WAV file is copied using any number of CD to CD copy software programs, it is very easy to change the format on the copy without noticing. Most people are pleased when they are successful that the copy plays rather than checking to make sure all the original characteristic in the original recordings are consistent in the copy.

For example, when copying a CD it is very easy to convert a .WAV file to an MP3 without knowing. Since most CD players and computers today will accommodate both file formats (.WAV and MP3), the average person can easily overlook this format conversion losing quality and causing generation loss.

MP3 is a lossy format which means that during the copying process some of the data is lost in an attempt to ‘compress’ the file making it smaller for internet use and storage reasons. This loss of data reduces the quality of the original audio recording.

From a forensic perspective, when a file is converted from.WAV to MP3, the meta data is stripped and altered making it very difficult for the audio forensic expert to authenticate the recording for litigation.

If you have an audio recording that requires expert authentication, make sure to send the original recording as it was presented to the expert and make and keep a copy for yourself. If you do not properly make the copy, worst case you will experience some generation loss and meta data alteration. The expert who is experienced in forensic investigation will have the best version of the recording to enhance and authenticate.

photo credit: Overdubbing via photopin (license)

Audio Enhancement from CCTV

Friday, April 26th, 2013

security cameras M11nikAO 199x300 - Audio Enhancement from CCTVRecently I have been asked on several of my forensic investigations to enhance the audio recorded on CCTV surveillance video. Audio can be very useful evidence in addition to CCTV surveillance video in the court room. Audio helps fill in the missing components that help the court review the series of events as they occurred.

Some of the video evidence I review must be viewed in a proprietary video player created by the manufacturer of the CCTV system. Other video evidence like smart phone video and some CCTV recordings do not require a proprietary player. Either way, as an audio video forensic expert, I have the skill and experience to know the best way to extract that audio recording and enhance it so that the triers of fact know more about the circumstances surrounding the criminal activity or litigation.

I have found that what is not captured on video by the CCTV system cameras may be captured on the audio portion of the same recording.

Once the audio track is extracted using a video software program, the digital audio file is imported into one of my audio software programs. One of the first steps is to increase the volume of the recording. The next step is to remove any unwanted background noise that distracts the listener’s sound perception. This process is often repeated until a desired outcome is achieved.
I also use other tools to help further enhance the audio recording like equalization, compression and notch filtering.
If you have any questions about audio enhancement or sound restoration from video surveillance call us at (800) 647-4281.

Audio Enhancement vs Clarification; The Audio Filtering Process

Wednesday, February 6th, 2013

4493462158 6f538e0e79 o - Audio Enhancement vs Clarification; The Audio Filtering ProcessOftentimes I’m given digital audio recordings by litigators to “enhance”. The request is for enhancement – they want to hear the voices in the recording better than what they currently hear. By the way, in litigation it should be termed ‘audio clarification’ – ‘enhancement’ has a negative connotation, implying that the audio has been in some way altered. Clarification is a better word – courts like it better and you don’t open yourself up to having your investigation questioned, or an accusation that your ‘enhancement’ somehow ‘altered’ the recording.

Some of the time, when I receive the files the first thing I discover is that the file is not an original recording and there are filters that have been previously applied to the file.

The other day I received a file from a litigator from another country and I agreed to do a pro bono listen, as I often do when I’m learning what their expectations are versus what reality will allow. (Television shows like “CSI” have given a false perception of what is and is not possible when it comes to audio enhancement).

The file I received from the International pro bono job had a very heavy noise reduction filter applied to it. I can tell just because I can recognize the sound of noise reduction on an audio recording. It would have been a complete waste of time to try to work with that file so I asked if they had an original version of the file, or a copy of the file that had not had any processing on it. The next morning there it was in my in basket – a link to the complete file without the noise reduction.

My message here is you can try things on your own but always save the original unprocessed audio file before filtering. Then, apply one filter at a time to the maximum capability of the filter to help your clarification.

As an audio forensic expert I sometimes apply several filters through the course of an investigation for a clarification project. However, amateurs tend to select a lot of different filters and not use them to their optimum potential before applying another filter.

This is why it’s important to seek the advice and retain an audio forensic expert to handle your evidence, have a chain of custody that can be reported at the end of the investigation, and properly apply audio engineering best practices and techniques, forensically. Following protocol that is accepted in the scientific community, allowing you to maintain integrity on your audio evidence will bring you the best results for your clarification process.

If your budget doesn’t allow for an audio forensic expert keep in mind a secondary message in this blog post: apply one filter at a time to its maximum potential when restoring the low quality in an audio recording.

photo credit: JPS NRF-7 NF Filter via photopin (license)

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