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Posts Tagged ‘audio enhancement’

Audio Enhancement – When Do It Yourself Won’t Work

Friday, April 29th, 2016

What is audio enhancement?

Forensic audio enhancement is the process of removing unwanted sounds and preserving wanted sounds. 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?’ 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.

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.

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. The reason we are asked to perform so many forensic audio enhancements is because we have been extensively trained in forensic audio enhancement, Our experts 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 primeauforensics@Gmail.com.

Using a Compressor for Forensic Audio Enhancement

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 lab. Like with most audio signal processors, it takes training and experience to operate compressors properly and effectively when performing forensic audio enhancement. 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.

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

JFK Assassination: Fully restored Air Force One recordings from November 22, 1963

Tuesday, November 19th, 2013

John F Kennedy At the end of this blog post is a fully restored digital audio file available for listening and downloading of the government conversation that occurred at the time of the assassination of President John F. Kennedy. The Announcer at the beginning of the recording  is the poorest quality of the entire 2:01:59.

This is a combination merged from two copies that were in existence. The first copy was released by the government and referred to as the ‘LBJ tapes’ in the early 1970’s. Another longer copy surfaced in a Philadelphia private auction in 2011. This longer copy was found in the belongings of the late General Clifton. Thanks to Bill Kelly, a veteran JFK researcher, Primeau Forensics has combined the contents of both recordings and fully restored them.

In this enhanced recording, you will hear conversations from Air Force One over the Pacific Ocean as they abort a trip to Japan and turn around, mid-air, to return to the mainland after learning about the assassination of the President of the United States. These recorded conversations between Ground Command, the White House and Air Force One include code names such as ‘Duplex,’ ‘Digest,’ ‘Volunteer,’ ‘Liberty,’ ‘Witness,’ ‘Crown,’ ‘Baker,’ ‘Watchman,’ and ‘Tiger.’

During the call they make arrangements to transport John F. Kennedy’s body, his widow, President Johnson and the other 40 people safely back to Washington DC. The carefully coordinated and strategically executed planning is heard in this recording. Decisions about media coordination on the ground at the White House, the post-mortem autopsy to be performed by law and President Johnson’s conversation with JFK’s mother, Rose Kennedy can also be heard.

It may take a while to get your ears acclimated to this early, mobile technology. Primeau Forensics has carefully removed unnecessary radio static and squeals to accommodate better listening. It is recommended that you use a combination of speakers and headphones to best listen to these recordings.

Listen to the updated Clarified Audio Track HERE:

[audio:http://www.primeauproductions.org/primeauforensics/JFK Airforce One Primeau Forensics .mp3|titles=JFK AIR FORCE 1 CLARIFIED AUDIO UPDATE]

Download Recordings Here!

Download Transcript Here!

Air Force One Audio Restoration/Enhancement Process

Friday, November 15th, 2013

Air Force OneA lot of people have been asking how I restored the Air Force One radio transmissions from November 22 1963, right after JFK was shot. Below I have outlined my process with brief explanations about each.

I used a software program from Adobe CS 6 ‘Audition’ for this entire process.

I identified the points in each version of the tape recordings, the LBJ version and the General Clifton version, for edit points before altering the recordings for enhancement.

I began the restoration process by sampling the tape hiss present on the entire recording and reducing with Adobe noise reduction. Next I went section by section and reduced the radio transmission noise which varied from conversation to conversation.

Then I applied equalization and compression filtering to help bring out the conversations. This was also done section by section since each conversation varied in speaking frequencies.  Adobe CS6 has a great tool, the FFT equalization which is very easy to use.

Audio restoration and enhancement is a process. I refer to it as peeling an onion; one layer at a time. If something does not sound right, I go back a step and try a different process. That’s the beauty of digital audio restoration and enhancement.

I am still working on the restoration as time permits and will update the videos posted here. I am hearing more and more of the conversations using critical listening and additional enhancement. Considering how primitive the technology was back then I am very impressed with the sound quality of these recordings. By the way, the General Clifton version is much better sounding and longer then the LBJ version.

Read about how this all started, and you can watch the story on “The Lead” with Jake Tapper on CNN below.

Primeau Forensics Restored Air Force One Recordings from John F. Kennedy Assassination

Tuesday, October 8th, 2013




Passing the Torch-An International Symposium on the 50th Anniversary of the Assassination of President John F. Kennedy will be happening October 17-19 2013 in Pittsburgh. http://www.duq.edu/events/jfk

A while back, Bill Kelly contacted Primeau Forensics and asked Audio Forensic Expert Ed Primeau to assemble and restore the original Air Force One radio transmissions that were recorded the day JFK was assassinated 50 years ago.

According to Primeau, ‘the quality of technology back then was very poor which weighs heavy on understanding the dialogue of the radio transmissions even after restoration’. Then Primeau had an idea, to have Partner Company Primeau Productions create a video which displays the wording on the bottom of the screen displaying the dialogue from the radio transmissions as they occurred.

Primeau sought some authentic footage from a private jet cockpit via a pilot who is a friend of Primeau Productions so the background footage adds an interesting background to the closed caption type text.

For more information on the conference contact:

Deborah G. Jozwiak

320 Fisher Hall
600 Forbes Avenue
Pittsburgh, PA 15282
Email: wechtinstitute@duq.edu
Phone: 412-396-1330
Fax: 412-396-1331

Eavesdropping: Is It Worth The Risk?

Thursday, August 15th, 2013

eavesdroppingYou’re having problems at home.  Your spouse has been acting very suspicious recently. You can’t help but think that your significant other is having an affair, but lack of communication with that person makes it impossible to find out the truth.  In a desperate attempt to find out what’s really going on when you’re not around, you decide to set up audio recorders all throughout your house to use for possible audio evidence against your spouse.

This is a practice we see every so often at Primeau Forensics. We’ve received a handful of cases in which a third party requests an analysis of audio taken from digital surveillance of a private conversation. What these people don’t realize is that these actions are against Michigan’s eavesdropping/surveillance laws (laws vary from state to state). The consequences of eavesdropping on a private conversation are dire, and can lead to not only a considerable fine, but also possible jail-time.  Before we dig deeper into this subject, we must ask the question: What exactly constitutes “eavesdropping?”

The surveillance and eavesdropping statutes are determined at a state level. Some states enforce what’s known as “one party consent.” Basically, as long as one side of the private discourse agrees to surveillance of the conversation, the action is legal.  Here is a guide of which states enforce one party consent and which states enforce two party consent.

According to Michigan State Law, eavesdropping is defined as “to overhear, record, amplify, or transmit any part of a private discourse of others without the permission of all people involved in the discourse.” In other words, the person doing the eavesdropping must have consent from both parties to record the private conversation.  This is what’s known as “two party consent.”

You might be thinking, “But this is my home! I have the right to dictate privacy in my own home!” This is also not true.  Michigan State law defines a “private place” as “a place where one may reasonably expect to be safe from casual or hostile intrusion or surveillance but does not include a place to which the public or substantial group of the public has access.”  This includes an empty home. As long as the location is not somewhere the public can easily get to, it’s considered a private place.  So yes, it is even illegal to eavesdrop in your own home.

In the state of Michigan, eavesdropping is considered a felony.  The potential  consequences of these actions include imprisonment in a state penitentiary for up to 2 years, a fine of up to $2,000, or any combination of both.  Obviously, this does not include the potential fines you’d face if the violated parties request a civil case.

In case the purpose of the blogpost hasn’t become clear by now, the point is that eavesdropping is very illegal, and the consequences are very serious.  Even if you do find some juicy inside secrets, Michigan law also states that “using or divulging any information which you know or reasonably should know was obtained in violation of the wiretapping laws” is strictly prohibited.  So if you suspect something is going on at home, the risks involved with eavesdropping just aren’t worth it.  Healthy communication with your spouse is a much safer option when issues at home arise.

photo credit: Eavesdropping ( Hello Hello anyone there ) via photopin (license)

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.

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)

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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