Last week I received a phone call from Guy Gordon, a WDIV TVR NBC affiliate here in Detroit, Michigan. He came to the Primeau Forensics office, bringing with him a recording of an unknown voice making certain remarks. Mr. Gordon asked us to perform a voice identification analysis on the recording. The assignment was to determine if Warren Mayor Jim Fouts was the voice speaking in this recording.
Mr. Gordon also brought some recordings with known samples of Mayor Jim Fouts speaking, which I compared with the unknown recording. I performed two forms of voice identification testing (also known as speaker recognition) with a second audio forensic expert employed with Primeau Forensics. We performed both aural spectral voice ID as well as biometric voice identification testing. After analyzing the results of the testing, we concluded that the voices were a ‘probable match’. The biometric software came back with a high probability of a match between the voices across the majority of the tests. The aural spectral method also showed high consistencies between the voices with very little difference in their pitch. I was asked to interpret the results in percentage of probability and I reported an 80% chance that the unknown voice in the recording was that of Mayor Jim Fouts.
During a voice identification analysis, it is important that I stay unbiased and focus on the science of the investigation. I have no stake in the outcome of the testing and I make sure that anything I report is based on my data and analysis. This ensures that any other expert could perform the same tests and provide the same results.
It’s important to note that the test I performed would be considered a preliminary or ‘Emergency Voice Identification Test.’ The reason I call it an ‘Emergency’ test is because an immediate analysis was required and we therefore had to use any available sample of the suspected person’s voice to perform the comparison. In an ideal voice identification analysis, we would create what is called an exact exemplar. This is a recording of the suspected person reading the same dialogue as spoken in the unknown recording. In this test, we used both an in-person interview with Mayor Jim Fouts, as well as a radio interview found online. For the purposes of this test, we were able to obtain accurate voice information from the found samples. Creating an exact exemplar would lend further credibility to the analysis and results.
In many cases, an Emergency Voice Identification Test is the best option after the event in question occurs. Sometimes the suspected party is not willing to create an exact exemplar, and in some cases the client does not want to alert the suspected party of the testing until some results have been found. Threatening calls are especially difficult to deal with, as alerting the suspected person prior to any conclusive results can be dangerous. Providing these initial results can provide the company or client the support they need to take the proper steps forward.
In this case, the emergency voice identification test was the fastest way to get results so that other city officials could move forward. We performed all the available testing to compare the voice directly with known samples. My conclusions were based on the data and results that were calculated from the voice samples. By basing my conclusions on the data, I avoid as much bias as possible so that the results are objective. High consistencies were observed between the unknown evidence recording in question and the two sample recordings we had available. The pitch comparison, formant comparison, and biometric comparison all showed the same results which led me to my conclusion of Mayor Jim Fouts being a probable match to the voice in question.
In 1991, recordings thought to include the voice of President Donald Trump was thought to have posed as a publicist to brag about himself. Full story can be seen here: https://www.apnews.com/5f3ad25e150b1c20074abfa9160d30a5
According to forensic testing using Biometric Voice Identification testing, the voice recordings thought to be Donald Trump are not the voice of Donald Trump.
A lead story from Washington Post this morning is regarding a recording that was thought to be Donald Trump. Trump denied the recording was his voice. Primeau Forensics was asked by The Washington Post to perform a forensic voice identification test to determine if the unknown voice in the Washington Post story features the voice of Donald Trump.
Voice Identification is the process of comparing ‘known’ voice samples in a recording against a recording of an ‘unknown’ voice to determine if the speakers are consistent. In this case, the ‘unknown’ sample recording is the publicist recording. Audio Forensic Expert makes use of critical listening, frequency and waveform analysis, and employs voice biometric software to ensure that the analysis is accurate.
Our senior expert, Ed Primeau has been practicing audio forensics for over 35 years. He has specific training in Voice Identification Analysis and has extensive experience testifying in court.
Primeau Forensics located a C-Span interview from 1991 titled ‘Donald Trump on Economic Recovery’. We chose this recording as the ‘known’ voice of President Donald Trump voice for forensic comparison. Therefor, we chose this older voice sample because it was closer in time to the ‘unknown’ recording.
The biometric software program that we used is a Speech Pro Product titled ‘SIS 2’. We formatted each speech sample and loaded them into the biometric software.
The result was a 97.5% mismatch meaning the ‘unknown’ voice recording that surfaced in the Washington Post today is NOT the voice of Donald Trump. The image above is a screen shot of ‘SIS 2’ with the test results highlighted.
After 34 years as an audio forensic expert testifying in dozens of cases on the local State and Federal court levels, I have gained experience and knowledge about the trial process.
Today, more than ever, many of my cases go to trial. Fewer criminal cases take a plea offer and even fewer civil cases settle outside the court room. I am spending more and more time helping courts understand audio evidence.
I chose to write about my court room experiences because I am often asked about testifying by our clients. Testifying is a very important aspect of my profession.
First off, testifying in court requires extensive attention to detail – both expected and unexpected. Testifying as an audio forensic expert requires an enhanced mental clarity, as the medium of audio may be interpreted subjectively, as well as objectively. My testimony as an audio forensic expert must be clear and precise, as well as simplified. It must include science, as well as opinions. It must also help the trier of fact understand the audio evidence for their decision making process. One excellent trial lawyer I previously worked with put it this way; I tell what is real and what is fake.
Tip #1-‘Preparation-The Key to Successful Testimony’
One of the most important elements of testifying is preparation. I always over prepare and insist our client attorneys schedule time with me before I get on the plane and in person before entering the court room to prep for trial. You can never be too prepared.
My preparation includes reviewing all work products, notes, reports and other expert depositions before going under oath. I also learn the client lawyer’s trial strategy and my role in that strategy. Preparation also includes anticipating cross examination.
Last November, I testified for the Attorney General for the State of New York in a negligent homicide in front of two Grand Juries. I had an agenda for preparation but my client lawyer had an even more intense preparation planned. We prepped my testimony for almost 8 hours over two days. There were 30 defendants and 8 defense lawyers. Since we anticipated cross there were no questions at all from any of the lawyers! Each one stood up and spoke (said) ‘No questions your honor’. Why? Because we did a great job preparing and anticipating cross; we brought out all questions on direct.
Tip #2-‘Look like an expert’
One of the most crucial aspects of testifying is the expert’s appearance. First impressions are extremely important especially when you are going to testify in court in front of a judge, jury and opposing counsel. Your credibility is directly proportionate to the way you look. Unfortunately, in a professional environment such as a courtroom, pre-conceived judgment from the jury is more than likely to happen. You want to make the best, most professional ‘first impression’ possible. Forensic experts need to look conservative. Some lawyers will not retain a forensic expert with visible tattoos, piercings or radical haircuts.
I remember testifying in Boston a few years back. Our trial team had two other experts one of whom I never would have guessed was going to testify. He did not wear a tie, his hair was a mess and his clothing was ill-fitting. I am not picking on this expert, but rather giving you a vision of what NOT to look like when testifying. On one hand, I shouldn’t be so judgmental, on the other hand, this is what a judge and jury do; judge!
Experts are paid well for their expertise; they should look the part.
Tip #3-‘Communicate with Conviction’
High quality communication is another ingredient to the success of your testimony. Not only does your communication matter for trial lawyers, but also your ability to communicate your findings to the jury is just as (if not more) important. When answering questions under oath, I keep my answers short and to the point and resist the temptation to ramble on. I include scientific terms in my answers but make sure to simplify them if a juror’s body language implies confusion. Communicating with conviction also requires great eye contact. When answering questions, I always begin my eye contact with the person who asked the question. Then while continuing to answer, I make eye contact with the rest of the court room including the jury, judge and opposing council. One major mistake I often see experts make is answering questions with tunnel vision, staring only at the person asking the questions. It’s not a deal breaker but will reduce the impact of your words and testimony.
Testifying as an audio forensic expert about forensic audio enhancement can be difficult due to the potentially low court room acoustics and environment typically found in most court rooms. Enhanced audio evidence is perceived when played in the court room. The problem with playing audio in the court room there is no visual representation of what the audio is portraying. It is important that everyone in the court can hear and comprehend your audio evidence. This too is communication. Equally important is that your testimony has to be crystal clear in helping guide the jury to understand your science and opinions.
Forensic Transcripts
I often include a forensic transcript as part of my work product. A forensic transcript is created by me using critical listening skills I have developed over 34 years practicing as an audio forensic expert. It ends with a paragraph like this: ‘Based on the pains and penalties of perjury I testify that the above forensic transcript was prepared by me and is an accurate representation of the events as they occurred at the time of recording so help me.’ Then I sign it and notarize if necessary.
Aside from these three tips, I focus on a healthy mindset. I make sure to get plenty of rest the night before. I drink a lot of water and eat healthy. A healthy mind set will contribute to a successful testimony. Testifying is stressful, but the key to success is preparation, appearance, and communication.
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.
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.
Closed circuit television systems have become a major contributor of evidence to court cases. While the video from these systems is often very important, the audio can often play just as much of a role in the investigation. At Primeau Forensics, we often are hired to enhance not only the video from a CCTV system, but the audio as well. As an audio forensic expert we are qualified to perform forensic audio enhancement.
Clients typically hire us for enhancements because the original CCTV system was not set up properly and was capturing less than ideal quality audio and video. Many times, the audio is more valuable than the video because of what was said during the event. While enhancing the audio is possible, setting the microphone on the system correctly can be extremely beneficial when an incident does occur. Getting a good, clean signal from a microphone relies on two key principles: microphone gain and microphone placement.
Setting a proper gain structure for a microphone will always yield the best result for any kind of recording. Gain is applied to microphones because microphones have inherently low levels. A preamp is used to amplify the signal before it is recorded into a system. When setting the gain, the goal is to get a high enough level that the signal is audible, while also making sure that the level does not clip the system or preamp. Clipping means that the signal has exceeded the capabilities of the system and begins to distort. This distortion hurts the quality of the audio and can make it very difficult to understand what people are saying in a recording.
Gain structure is often set based on the input signal, which makes setting a surveillance system microphone difficult. The input signal of a surveillance system is always changing and cannot be manually reset whenever people enter or leave the area. When setting the gain for a surveillance system microphone, it is usually a good idea to test different levels of sound in the room. Having someone talk or even yell in the room while you set the level can ensure that the recording will not clip when it is recording later on.
We recently recovered some surveillance video evidence that required an audio enhancement. When we received the audio, we found that the gain had been set too high and the entire recording had clipped. We also found that because the room was small and filled entirely with hard surfaces, there was a buildup of reverberant sound. Reverb consists of reflections of sound off of surrounding surfaces. Some reverb is always present, but too much can begin to cover up the direct sound. Direct sound is the original sound coming directly from the source, such as a person speaking. In this case, the gain should have been set much lower on the microphone. This would have produced a much cleaner and more audible recording. Reverb is a more difficult issue to combat and relies much more on the microphone placement.
Different microphones will have different pickup patterns, which means that they will pick up sound in different directional patterns. Typical microphones used for surveillance systems are either cardioid or omni-directional microphones. Cardioid microphones pick up sound from one direction and reject sound from the opposite direction. Omni-directional microphones pick up sound from all directions. Knowing what kind of microphone your system is using is the first step to setting up a microphone. If you are using a directional microphone, it should be aimed at the area where the sound sources will be. Omni-directional microphones are easier to set up because they do not need to be aimed in any direction.
When placing the microphone, it is important to be aware of other extraneous noises in the room. We often see CCTV systems placed near the ceiling and in corners so they can obtain the best view point of the area. This is not always the best location for the microphone depending on how the room is designed. If an air vent or another electrical device is near the microphone, they will add a large amount of noise to the recording and can cover up desired sound. If a directional microphone is being used, try aiming the rejection end of the microphone at the unwanted sound source. This means the least amount of the unwanted signal will be picked up.
Reverb can also be an issue in smaller spaces that have no absorptive surfaces. When the direct sound is buried by the reverb, it can make the desired signal muddy and undefined. Acoustic treatment can be added to a room to deaden the amount of reverb, but this is more often an approach for musical spaces. A typical fix for a surveillance system can be placing the microphone closer to the desired sound. Placing the microphone in the center of the ceiling instead of in a corner could cause the microphone to pick up more of the direct sound, resulting in better and clearer audio. Because sound and reverb tends to build up more in corners, placing the microphone away from the corner will also prevent it from picking up those extra reflections.
Audio evidence is a very prominent part of many investigations and court cases. Setting up a microphone properly for a surveillance system can often make a huge impact on whether that audio can be used as evidence or not. As an audio forensic expert, I come across many audio recordings that could have been much more audible if the system had been set up properly. When installing a surveillance system, setting the gain for the microphone and placing the microphone properly will always improve the quality of the recorded audio.
As an Audio Forensic Expert, my day to day activity includes forensic services like audio enhancement and authentication, as well as voice identification. Audio enhancement is probably the most common service I provide, because more often than not, the audio evidence was not recorded in the best way possible. Audio evidence can often be one of the most important pieces of evidence for a case, so it should always be given a great deal of attention.
One of the most common ways people create digital audio evidence is by using digital audio recorders. Law enforcement will often use them for interrogations and confessions, and sometimes even out in the field as a backup for their dash cam or body cam. People outside of law enforcement use them for creating audio evidence as well.
I would like to mention that concealed audio recordings are not always legal. Federal law states that creating an audio recording only requires one person’s consent, but some states follow a ‘two-party consent’ law. This law means that all parties who are on the recording must give permission to the person recording in order for it to be used as evidence in court. I highly suggest looking in to your own state’s laws regarding concealed audio recordings before making one.
When creating a digital audio recording that is going to be used in court, there are many things one should be aware of before making the actual recording. The biggest issue I usually come across is low recording levels. While it is possible to increase the signal level afterwards through forensic audio enhancement, this is unnecessary time and money spent. This will also increase the noise floor of the recording, which can make it more difficult to hear what is happening in the recording. Creating a clean and audible original recording can make the enhancement process much easier and can often make the evidence much more useable in court.
When preparing to make an audio recording, regardless of whether it is a concealed recording or an interrogation recording, the user should always look at the settings of the digital audio recorder.
Two major settings determine the quality of a digital audio recording: sample rate and bit depth. Together, these settings also determine the bit rate of a recording. Changing these settings will affect both the quality of the audio recording and the amount of space used on the digital recorder. When creating digital audio evidence, it is necessary to balance these two in order to get a high quality recording while optimizing the amount of space on the digital recorder. Thankfully, many digital audio recorders will record in lossy compressed formats like MP3 files, which take up much less space and don’t sacrifice a lot of quality.
When recording digital audio in an MP3 file format, the two key settings to pay attention to are the sample rate and the bit rate. The sample rate will ultimately determine the range of frequencies the recorder picks up. At least two samples are needed to record any frequency, which means the sample rate must be twice as high as the highest frequency you need to record.
The range of human hearing is roughly between 20Hz and 20kHz. Typical audio recordings are done at 44.1kHz to capture the full range of human hearing. While this is standard for music and other professional recordings, it is not always necessary for audio evidence.
Most fundamental frequencies of the voice are between 100 and 500Hz with some of the most important harmonic content between 1kHz and 4kHz. This means that a sample rate as low as 8kHz can sometimes be adequate for recording a conversation, which will also save a large amount of space on the digital recorder.
Bit rate determines the amount of bits that are processed per second, which determines the fidelity of the audio. Typical MP3 files are recorded between 192kbps (kilobits per second) and 320kbps, but they can be as low as 32kbps. Just like with the sample rate, a higher bit rate means a higher quality of audio but also a larger file size. The issue that arises with low bit rates is that the compression process applied to the file can start creating digital noise in the recording. This digital noise can often cover up parts of the recording and once it is there, it is very difficult to remove.
When determining what settings to use on a digital recorder, it is always a good idea to make multiple test recordings before making an audio recording that will be used as evidence. These test recordings will let you try out the various settings and then listen back to see what sounds best and what fits your needs the most.
Another setting that is sometimes included on digital recorders is the ‘voice activation’ setting. This setting will start and stop the recording based on the amount of signal the microphone is picking up. While it can be a good way to save space on the recorder, it is not recommended that this setting be used when creating any kind of digital audio evidence. If this setting is on, the digital recorder could stop recording at a key moment in the conversation and miss a crucial piece of evidence. If extra space is needed on the digital recorder, adjusting the quality settings is a much better way to go. Recording all of the content at a slightly lower quality is a lot safer than relying on the ‘voice activation’ setting and missing important content.
Monitoring the battery life on the digital recorder is another very important thing to keep in mind. In some applications, like recording an interrogation, the digital audio recorder can simply be plugged into the wall so it will not run out of power. In other cases where you do not have this option, make sure the battery is fully charged or you have put in new, good quality batteries. Keeping extra batteries with you is also good practice, just in case the recorder does run out of battery and needs a replacement.
When creating the actual recording, try to be as close as possible to the person being recorded. As I mentioned before, one of the biggest issues with audio evidence is a low volume or record signal level. The farther away from the source the microphone is, the lower the signal level and the lower the signal to noise ratio. This means that less of the desired signal and more of the unwanted background noise will be recorded. Background noise can include any extraneous sounds such as furnaces, refrigerators, air conditioners, televisions or even the internal sound created by the digital recorder itself. These sounds can detract from the quality of the recording and often make the desired signals unintelligible.
Placing the digital recorder in a good location is key for making a good digital audio recording. Keep a few things in mind when making your recording. First, the microphone should always be aimed at the subject that you are recording. When placing the recorder in a pocket or a purse, aim the microphone towards the subject. Also make sure that the digital recorder is relatively stable in its location, because any movement of the recorder will be picked up by the microphone and can cover up other parts of the recording. Pay attention to any materials that may be in between the microphone and the sound source; the thicker the material, the more damping there will be on the signal, which will decrease the record level.
Many digital audio recorders have a microphone input which allows you to use an external microphone. The external microphone is always the best option to use if the recorder is going to be placed inside something. When using this option, it is always a good idea to use a high quality external microphone.
There are many different types of microphones that will work better for different situations. Lavaliere microphones are extremely helpful because they are small and usually omnidirectional. This means that they will pick up sounds from all directions and they can be placed anywhere on your person while the digital recorder stays in your purse or pocket. Other microphones, such as directional microphones, may work better during police interrogations because the subject will not be moving during the recording.
As I mentioned before, always create a test recording before making the recording that will be used as evidence. Testing different microphones, microphone placements and locations will help you learn how your digital recorder works and responds to different environments. If possible, try conducting the test recording in the same place that you will create the real audio evidence so you can prepare for any extraneous background noises and other obstacles. After making the test recordings, listen back so that you can make sure the desired sounds can be heard and the sound quality is high enough.
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.
Back at the end of October, I was contacted by Nicole Bogart from the Global News in Toronto who asked that I conduct a voice identification between known samples of Mayor Rob Ford and a male caller to a radio show named Ian. They believed that the caller who was defending the mayor was not a person named Ian but rather Rob Ford himself.
In the video below, I explain my process and play samples of the audio’s that were used to compare and arrive at my conclusion.
A 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 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.
Below, you can watch the story on “The Lead” with Jake Tapper on CNN:.
