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Archive for the ‘Audio Enhancement’ Category

Audio Enhancement – When Do It Yourself Won’t Work

Friday, April 29th, 2016

Forensic audio enhancement is the process of removing unwanted sounds like static, HVAC fans, hums and other distracting background noise from a recording. The goal is to reveal or uncover the dialogue, conversation or ‘wanted’ sound in the audio recording.

There are two types of audio recordings that can be enhanced: analog and digital.

Analog recordings are those that have been created using some type of tape recorder. 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 noise. 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 in this format, the primary goal is to restore the lost or wanted sounds such as the dialogue and other pertinent events. 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 tape is involved. Digital recorders store 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 like the issues mentioned above. The audio forensic expert will also preserve an exact duplicate of the evidence recording for their own records and for the court.

The big question that is always asked is ‘can my recording be enhanced?’ There are many situations where forensic audio enhancement helps reveal the events or 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 or investigation.

After 32 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 litigations. The reason I am asked to perform so many forensic audio enhancements is because I have been extensively trained in forensic audio enhancement, I have completed and testified in dozens of cases and courts about my forensic enhancement, and I 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 primeauforensics@Gmail.com.

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Audio Enhancement: Removing a Single Sound

Monday, August 24th, 2015

Noise ReductionOne of the most common audio issues that I address during an enhancement is noise and other extraneous sounds. The noise floor is usually consistent throughout the recording and can be removed to varying degrees by using noise reduction software. The most complicated issues are the extraneous sounds that are not continuous. These sounds could include anything from a plane flying overhead to someone whistling while people talk. These sounds are difficult to pinpoint with standard tools like noise reduction and equalization, but they can be identified using 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 Forensic Expert because it visually presents everything that is happening throughout the audio in one window. Using this, the expert can both identify and address individual harmful noises 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.

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.

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, but any technique that helps should be used as long as the science is sound.

 

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Using a Compressor for Audio Enhancements

Wednesday, April 8th, 2015

As an Audio Forensic Expert, knowing what tools are available to me and how they work is extremely important. One type of signal processor that I frequently use is a compressor. While this is often thought of as a tool for music production, it serves 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. This experience also helps me determine whether or not the compressor is needed for enhancement.

A compressor is a device that automatically attenuates the gain of an audio signal. This means that when the audio reaches a certain level, the compressor will lower the gain of the audio signal. When the audio drops below this certain level, the compressor will stop attenuating. It is similar to a person manually adjusting the volume on a stereo as a song is playing. A benefit of a compressor is that it also has a ‘make up gain’ control. This allows the operator to raise the overall level of the audio after it has been attenuated. Through this process, the recording can be made louder without clipping or distorting the signal.

I will typically use a compressor when certain sounds in a recording are much louder than the rest of the audio and I need to balance the overall volume. An example would be a dog barking occasionally throughout a recording that is peaking much louder than the people talking. Using a compressor, I can attenuate the level of the barking without affecting the level of the people talking. Once the louder signal has been attenuated, I can use make up gain to increase the overall level of the recording. This becomes extremely helpful when the sound source that needs to be heard is quieter than other sounds. I will often receive recordings where the conversation that needs to be heard is buried or behind another sound source, like a television or even other people in the room. By adding a compressor, I can decrease the difference in level between the two signals.

Compression is not always the best approach for an audio enhancement and in some cases, I avoid using it completely. One of the biggest issues in recordings is a loud noise floor. The noise floor is the sum of all of the extraneous and unwanted noises in the recording. As I mentioned before, sometimes this noise floor is louder than the desired sound and therefore compression helps make the desired signal louder with respect to the noise. In some audio, the noise is already quieter than the desired signal. In these cases, using too much compression can actually increase the level of the noise relative to the desired signal. This can actually make the desired signal more difficult to hear and hurt the overall enhancement.

This is why it takes training and experience to properly use a compressor. With the knowledge that I have gained from my 30 plus years as an Audio Forensic Expert, I know when to use and when not to use a compressor on audio. I also know how to properly use it so that I improve the quality of the audio instead of making it more difficult to hear.

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The Structured Approach to Objective Audio Enhancement

Wednesday, July 9th, 2014

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.  

1-800-647-4281

primeauforensics@gmail.com

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An Accurate and Affordable Approach to Audio Enhancement

Tuesday, June 10th, 2014

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. 

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Audio Enhancement – A Forensic Approach

Friday, April 25th, 2014

audio enhancementThere are two ways to look at audio enhancement, from a recreation standpoint and a business/legal standpoint. Most people searching for audio enhancement are looking for a solution to better hear a poorly recorded audio conversation. 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. 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. 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 reverberant 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.

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Generation Loss in Analog and Digital Recordings and Audio Forensics

Thursday, January 2nd, 2014

3101873296_eaf94446fb_oIt 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)

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Audio Enhancement from CCTV

Friday, April 26th, 2013

CCTV CameraRecently I have been asked on several of my forensic investigations to enhance the audio recorded on CCTV video surveillance. 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.

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Audio Enhancement vs Clarification; The Audio Filtering Process

Wednesday, February 6th, 2013

FilterOftentimes 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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Audio Enhancer Tips for Concealed Recordings

Tuesday, September 25th, 2012

concealed recordingsAs an audio forensic expert, I receive audio recordings that were created in noisy public environments. One of the activities that I am often asked to do is to enhance these audio recordings so the conversation can be clearer and can be used in litigation. One of the tips that I would like to offer in this post is this: an ounce of prevention is often the best remedy. In other words, instead of putting the audio recorder in your pants pocket, purse, briefcase or other type of bag, consider wearing a garment that has a lapel pocket where the digital audio recorder can be easily be placed. Placing the digital audio recorder in the lapel pocket of a shirt or sport coat allows the microphone to be closer to the sound source or conversation than if it were placed in a bag or briefcase under the table or on the floor.

A second tip is to consider the recording location. Oftentimes when litigators create concealed recordings, they meet the opposing party in a public location. Public locations tend to be noisy, so the recorder picks up the noisy background disturbances in addition to the conversation that’s important to the litigation. When you choose the public location to record your conversation, pick the quietest spot at the location. Arrive early so you—the person creating the recording,—can choose the quietest spot at the location. Listen carefully when you walk into the location and find the quietest spot or table to sit at when creating your recording.

The third tip is to make sure that your recorder is functioning properly. Many conversations are lost because of a low battery, a microphone pointing in the wrong direction, or not enough space on the memory of the recorder. So before you make your concealed audio recording, make sure you have fresh batteries in your recorder and make sure the folder you are recording your conversation into has plenty of space for the duration of your conversation. (You can check this by looking at the manual for your recorder and determining how you can assign your folders for the most optimum use of your storage space.) You also want to make sure that you have enough storage space left on your digital audio recorder. Delete any recordings that are not needed—or, if the conversation is valuable, purchase a new digital audio recorder. Olympus is one of the most reliable manufacturers of digital pocket recorders.

These audio enhancer tips for concealed recordings will help you to successfully create a recording of your conversation for use in litigation. And remember: do NOT delete the original recording from your recorder in case there is ever a question of the integrity of your concealed recording.

For more information call 1-800-647-4281.

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