Audio Forensic Expert

Voice Identification Standards: Practical and Official

2012-01-06T12:06:00.000-05:00

As an audio forensic expert who conducts voice identification, I receive calls from people around the world asking about voice identification. The American Board of Recorded Evidence provides voice identification standards that help me determine if I can identify a piece of audio evidence.

Some of the requests I receive are a stretch because the audio in question does not have enough words spoken in order for me to create an exemplar. An exemplar is one of the most important tools to a voice identification test. The exemplar must be made as closely to the original recording as possible. The audio forensic expert often does not have as much control over the technology when making the exemplar as they would like. In that case careful attention must be paid to the variable electronic readings in spectrograph measurement allowing or compensating for the variable.

In other words, if a piece of audio evidence was a telephone intercept or voice mail recording, the exemplar must be made using a telephone and recording device as similar as possible to the device that was used to create the original recording in question. This is where the attorney representing our side in the litigation comes in. The attorney must petition the court during discovery to help the audio expert learn what equipment was used to record the original evidence.

This process was especially important back in the analogue days. Today’s digital recordings create much higher quality recordings and have different authentication processes.
Here are the American Board of Recorded Evidence voice identification requirements as accepted in the scientific community:

Standards for Comparisons Determination

The following are the standards accepted nationally by all professional organizations involved with voice identification, including the FBI, the Audio Engineering Society, the International Association for Identification, and the American Board of Recorded Evidence:

IDENTIFICATION: At least 90% of all comparable words must be very similar aurally and spectrally, producing not less than twenty (20) matching words. The voice samples must not be more than six (6) years apart.
PROBABLE IDENTIFICATION: At least 80% of the comparable words must be very similar aurally and spectrally, producing not less than fifteen (15) matching words.
POSSIBLE IDENTIFICATION: At least 80% of comparable words must be very similar aurally and spectrally, producing not less than ten (10) matching words.
INCONCLUSIVE: Falls below either the Possible Identification or Possible Elimination confidence levels and/or the examiner does not believe a meaningful decision is obtainable due to various limiting factors.
POSSIBLE ELIMINATION: At least 80% of comparable words must be very dissimilar aurally and spectrally, producing not less than ten (10) words that do not match.
PROBABLE ELIMINATION: At least 80% of the comparable words must be dissimilar aurally and spectrally, producing not less than fifteen (15) words that do not match.
ELIMINATION: At least 90% of the comparable words must be very dissimilar aurally and spectrally, producing not less than twenty (20) words that do not match.

To learn more about voice identification, call 800.647.4281

Voice Identification Line Up

2011-12-16T11:12:00.000-05:00

Recently, I was asked to listen to 23 phone intercept recordings and determine if any of the voices in these conversations were repetitive. As an audio forensic expert, when I conduct a voice identification test, I have to have an exemplar or voice sample of the accused.

Back to back voice samples are the first step to a task like this. Each telephone conversation included two voices. The first thing I did was separate the voices and create two new audio project files. That way I can critically listen to all voices back to back in order to determine if any of the voices were identical or at least had similar characteristics.

These telephone recordings were created by federal law enforcement and were very clean. No noise reduction was necessary as it was back in the analogue days.

Once I completed this back to back assembly process, I had the recordings transcribed so I could choose phrases and sentences to use when creating the exemplar. An exemplar is a known sample of speech recorded as exact as possible to the original evidence. The exemplar is created under supervision so I know the identity of the person speaking (who is the accused).

When the exemplar recording is complete, those phrases that were recorded are now inserted into the original evidence recordings in the new audio project files for critical listening. In this particular case, I noticed that the exemplar did match some of the telephone conversation evidence that was recorded by the federal authorities.

The next step is to create work notes listing all the similarities as well as differences observed during the critical listening phase of the voice identification testing. These notes help me create my report when the voice identification testing is complete.

I also use spectrum analysis and sonograms to help with the identification process. I often print out the display of these two electronic measurement devices and include these print outs with my report.

One thing I have learned over the 25+ years as a forensic expert is to keep it simple. Judges like an uncomplicated decision from a qualified forensic examiner. They become frustrated when they have to interpret new information they have never heard of or are not familiar with.

Voice identification is both an art and a science. As a voice identification expert, I use my talent skill and ability in every case I am assigned to. The science is acceptable in court and the art is the ability to adapt every case to scientific standards.

Is It Still Elvis Presley̶? Cast Your Vote

2011-12-09T14:51:00.001-05:00

Last Monday I did another radio interview for Elvis Express Radio. Joe from the network called me about 10 am EST and asked how I knew this song had Elvis Presley singing. I explained to him that I did forensic voice identification and compared the vocal to similar types of Elvis songs from around the same time. ‘What Now My Love’ was one of the songs I used as an exemplar, which is the second step when I conduct voice identification. In this case an exact exemplar could not be created for obvious reasons so we went with songs that were recorded around the same time and had similar vocal innovation.

We would like to know what you think about the new song. Do you believe it's Elvis Presley?

Joe from Elvis Express radio told me during my interview that he had been an Elvis fan for 40 years and he believed that “Living to Love You” was not sung by Elvis Presley. I told him that I respected his opinion and we concluded the interview.

I did not think much of it because I have been an audio engineer working with world renowned and local musicians and artists as well as a forensic expert for 27+ years. Of course I could be wrong; there is always a margin of error in any voice identification.

Today I received an email from the lawyer handling the sale of the song. Her update is very interesting. She hired author Tom Grace who is an Elvis expert to listen to the song and review the documents.
Tom has positive feedback regarding my forensic analysis. After he listened to the tape he confirmed that it had to be Elvis for a different reason than my forensic voice analysis determined.

"No one would try to make a tape to sound like Elvis with such a poor arrangement" was his first comment. The instruments were all out of balance including the piano. Tom said he could hear the piano and he believes he knows who the piano player was and who was playing the guitar and base.

He has researched the date and time that everyone was together and came up with February 24, 1965 in Nashville when they were recording the soundtrack for the Elvis movie “Harum Scarum.” There are three recordings documented from 11:00 p.m. to Feb 25 at 1:00 a.m.

He does not know what was recorded other than they worked on one record which was for “Harum Scarum.” The recording was not put on a reel and must have been direct to acetate because there is a popping sound in it. It was not copy written until 1976; a letter to Albert Lee states copy writing does not normally occur until the song is published.

Speculation is that Jimmie Crain heard that Elvis wasn't doing well in 1976, so he checked and found the song had not been previously copy written by RCA . He apparently decided to copy write it before something happened to Elvis.

Tom Grace will be publishing his findings and the lawyer representing the sale of the song, Violet Hinton, has contacted WWMT TV 3 to interview Tom Grace in a follow up story.

If you believe this song is Elvis Presley, hit the like button on the article link on Audio Forensic Expert's Facebook page. You can also email us at Primeau@PrimeauProductions.com.

Clarification for Authentication of Audio Recordings

2011-12-07T13:12:00.000-05:00

The following article was written to help the legal community better understand the audio clarification process. The descriptions it includes will also help a lay person better understand the value of audio clarification.

All digital and analogue recordings have a noise floor. The term “noise floor” originated when manufacturers of analogue audio recorders referred to the extraneous noise that their machines created in addition to the desired recorded audio signals.

Often, a background noise constitutes most of the audio recording and covers a portion of speech that needs to be audible in order to determine a series of events pertinent to the case. Noises like the humming of a fan, air conditioning, heating systems, wind, and other unwanted sounds contribute to the audio recording noise floor. These noises can often be removed by the audio forensic expert (who is also known as the examiner) to help determine facts about the series of recorded events.

The extraneous sounds of background noise and noise floor can consist of a heating or air conditioning fan running, refrigerator motor, window fan, clock, fluorescent lighting, wind, rain, the running engine of a car, and even radio or television. All these sounds contribute to the background noise and noise floor of a recording and aid the forensic examiner in authenticating a recording. However, although these sounds can authenticate the environment of an alleged crime, this background noise can interfere with the forensic examination. It is appropriate and part of the forensic examiners job to remove these background sounds in order to authenticate or clarify an exhibit of audio recorded evidence.

Some of the recordings experts are asked to authenticate are confession recordings created by law enforcement agencies. Defendants exclaim, “That is not what I said, they edited it” or “There is more I said that has been edited out of the recording”. Due process entitles both parties in litigation to examine any evidence presented in their case. However, original recordings are not always available for examination. How do you as a law enforcement official feel about the absence of original recordings?

I have worked on cases where missing “original evidence” was considered spoliation of evidence. Personally, I believe that the circumstances of each case should be considered by the forensic examiner before any decision has been made by either party.

If there are noticeable questionable characteristics that the forensic examiner observes regarding the audio evidence, then the expert must notify the officials in charge of the findings during the preliminary examination phase of the forensic investigation. Original recordings are required for litigation cases. If they are not produced, a motion to suppress the evidence should be filed.

A Three Part Process for Audio Restoration

2011-07-13T09:03:00.000-04:00

In the following blog post, I will help you understand a basic three part process for audio restoration. In the embedded video, I exhibit an audio file that was lifted from a video which is in need of some audio restoration. The video walks you through the process which varied from video to video in this multi part video training set.

The first step is to either compress the audio increasing the gain during the process or removing any unwanted distortion; whichever you feel is best to lead with. You can try one process first then the second. Worse case you can apply the processes in opposite order if your initial results are not up to your expectation.
Varying the order which filters and noise reduction are applied is how a forensic examiner will proceed when restoring an audio file. Audio restoration takes time, patience and good critical listening skills.

The three filters I will demonstrate in this video are wave hammer, equalization and noise reduction. I use Sony Sound Forge software 9.0 for this example. Other audio software programs can be used and more than likely include similar filters to those found in Sound Forge.

Creating an Exemplar for Voice Identification

2011-05-17T08:37:00.000-04:00

An audio exemplar is an audio recording that is created by the audio forensic expert and will be used as a comparison to the evidence for the purpose of identification. Unlike the original evidence, the exemplar is created in a controlled environment. If the original evidence is a telephone recording then the exemplar must be created on the phone as close to the original evidence as possible. If the phone that was assumed to be used to create the evidence is available, that phone should be used to create the exemplar. The goal is to reconstruct as much of the original recording characteristics as possible when recording the audio exemplar.

A transcript of the evidence recording must be created to help guide the exemplar recording process. The forensic expert does not notify the accused (defendant) of the portions of the transcript that will be recorded until the scheduled recording time. The reason for this is to have the ability to be spontaneous and unrehearsed when creating the exemplar.

The exemplar comparison call is scheduled between the lawyer, audio forensic expert and the defendant. If the defendant is incarcerated the prison is involved in the coordination so the call can be recorded from the prison. In this case, the identity of the person delivering the exemplar is known. If the defendant is not incarcerated, then a neutral party or witness must be present to swear to the identity of the person making the exemplar recording. A representative from the court of law enforcement official would be a good witness.

The call is recorded by the audio forensic expert using an electronic telephone interface device manufactured by Gentner. Other companies manufacture similar devices but we use the Gentner SPH 10 in our forensic lab.
We also use Sony Soundforge software to record the exemplar and conduct the voice identification testing.

The call begins with the forensic expert explaining to the defendant the voice tone necessary when delivering lines from the transcript for recording purposes and continues to guide the exemplar recording process. Its best to have the defendant read each sample three times giving the expert options when conducting the testing.

Double check the recording quality by monitoring the telephone recording both during and after the exemplar creating process is complete especially if the defendant is incarcerated.

Once a reliable exemplar has been created, the audio expert can begin the voice identification process. If multiple telephone conversations are submitted as evidence, an exemplar should be created of each conversation.

Creating a high quality exemplar under supervision is probably the most important part of the voice identification process. If there are other recorded conversations that include the defendant’s voice but are not the exact words used in the evidence recording, they can be used as comparison. Be cautious in the voice identification testing as this is not as desirable of a testing as having an exact exemplar. In this case the voice identification expert must rely on their skills to substantiate the reasoning and their conclusion more so than when an exact exemplar has been created.

Original Digital Media Evidence is Mandatory

2011-04-02T11:58:00.002-04:00

Digital audio is recorded and stored in electronic equipment. If the audio is needed in court, the original device that created the recording must be identified and kept in a chain of custody. The only exception is when both parties involved in the litigation agree that a copy is sufficient. If there is doubt in the authenticity, the audio expert must refer to the original to support the authentication of the audio evidence.
The reason is that the audio copy has been removed from its original environment and is vulnerable to alteration. In addition, if a computer created the original recording, additional information can be examined by the audio expert such as file creation, last accessed and other computer forensic information that can support the audio evidence authenticity.
If the original audio recording was created in a digital pocket recorder (which many law enforcement officials use) then that original pocket recorder must maintain a chain of custody and become the original evidence. Any external copy created by a number of methods and played outside of the digital pocket recorder is a copy. Unless an audio expert can authenticate the copy (which can be done once the original has been examined) it cannot be used in a court proceeding. If the audio copy has been authenticated by an expert, than it will be easier to play and amplify in the court for a judge and jury.
I have testified in criminal cases for the defense when the client swore under oath that the audio recording had been altered and did not represent the facts as they occurred. Now it’s their word against the other side and when the court has to decide, the prosecution most always, will prevail.
If you have had an experience with audio evidence and would like to share your story, please comment on this post and your story will be heard.

Clarification for Authentication of Audio Recordings

2011-03-09T07:52:00.001-05:00

All recordings have a noise floor, digital and analogue. The term originated when manufacturers of analogue audio recorders referred to the extraneous noise that their machine created in addition to the desired recorded audio signal.

Often times a background noise constitutes most of the audio recording and covers a portion of speech that needs to be audible in order to determine a series of events pertinent to the case. These noises can often be removed by the audio forensic expert to help determine facts about the series of recorded events.

Background noise and noise floor extraneous sound can consist of a heating or air conditioning fan running, refrigerator motor, window fan, clock, fluorescent lighting, wind, rain, car running and even radio or television. All these sounds contribute to the background noise and noise floor of a recording and aid the forensic examiner in authenticating a recording. However, this background noise can interfere with the forensic examination. It is appropriate and part of the forensic examiners job to remove these background sounds in order to authenticate or clarify an exhibit of audio recorded evidence.

Some of the recordings experts are asked to authenticate are confession recordings created by law enforcement agencies. Defendants exclaim, “That is not what I said, they edited it” or “There is more I said that has been edited out of the recording”. Due process entitles both parties in litigation to examine any evidence presented in their case. However, original recordings are not always available for examination. How do you as a law enforcement official feel about the absence of original recordings?

I have worked on cases where missing “original evidence” was considered spoliation of evidence. Personally I believe that circumstances of each case should be considered by the forensic examiner before any decision has been made by either party.

If there are noticeable questionable characteristics that the forensic examiner observes, then the expert must notify the officials in charge of their findings during the preliminary examination phase of the forensic investigation. Original recordings are required and if not produced, a motion to suppress the evidence should be filed.

Yep It's Him, Thomas Pynchon

2010-10-04T14:23:00.000-04:00

www.PrimeauProductions.com 800.647.4281

By Steven Kurutz
Last Tuesday, long-suffering fans of the reclusive writer Thomas Pynchon received a double gift. Pynchon’s latest book, “Inherent Vice,” a stoned-out detective story set in early-‘70s L.A., was released by Penguin Press (read the Journal’s review). And to promote it, the publisher put out a cool video trailer featuring a narrator whose slow, lazy cadence sounds suspiciously like that of Pynchon’s, as evidenced by a guest appearance on “The Simpsons” and this clip from what appears to be a German TV spot. Inquiries by GalleyCat and others as to whether Pynchon is the guy channeling the novel’s main character, beach bum private eye Doc Sportello, have been met with “no comment” from Penguin Press and the video’s producers, Meerkat Media. And, of course, the man himself is mum (Would Pynchon fans expect anything else?).

In an effort to solve the mystery, Speakeasy did a little sleuthing and called Ed Primeau, a Michigan-based sound engineer and voice identification expert. Like handwriting analysis, voice identification is an inexact science, often used by law enforcement to rule out a suspect rather than to provide a 100% clear-cut ID. Still, people have unique vocal timbres and deliveries, especially Pynchon, who sounds like actor John Astin (i.e. Gomez Addams from the old TV show), mixed with a Midwest corn farmer, with a dollop of aging stoner.

So is it possible to rule out the man in the “Inherent Vice” trailer as being the same guy in the Simpsons episode and German TV clip? Not at all, according to Primeau. In fact, he says, based on a preliminary analysis the speech pattern and inflection is “virtually identical” in all three clips. “It’s a very unique style of delivery,” Primeau says. “It’s very up-and-down. He’ll hit these accented spots every few words. You know the TV show “Dragnet,” how Joe Friday talked? It’s the opposite of that.”

We should point out Primeau is an unbiased witness, having never read Pynchon (“I don’t know this guy but it looks like he has some history as an author,” he said). Nevertheless, if he hasn’t been taken by the man’s work, Primeau is intrigued by his voice, which he describes as “a tobacco-driven soft rasp.”

Primeau’s conclusion: “Beyond a reasonable degree of professional certainty, I believe these voices were delivered by the same person.” Confronted with Primeau’s findings, Tracy Locke, a publicist at Penguin, came clean and admitted, “It is, in fact, Thomas Pynchon doing the narration.”

What is an Audio Forensic Expert? Audio Authentication Video by Ed Primeau

2010-10-04T14:05:00.000-04:00

Ed Primeau 800-647-4281
If you ever wondered what audio forensic experts do, this video will help you understand the science as well as the art of audio forensics. In this video you will see me discover three anomalies in this under cover audio recording.

Audio Editing 101

2010-03-03T04:41:00.000-05:00

If you use Pro Tools, Audacity or Sound Forge, editing audio is an important process to improve the perceived value of your audio production. Making audio products for sale and pod casts increase the perceived value of your business especially when the audio quality and production value are world class.

Here are a few editing tips for a professional audio production.
1. What ever program you are using, find the undo button. Don’t you wish life had an undo button? Windows has control Z that works with many audio editing software programs.
2. Shorten breaths and pauses. Many times when you are creating an audio recording, you pause to collect your thoughts. Tighten those pauses and remove breaths to increase the production value of your audio production.
3. If you stumble, fumble or flub, develop consonant editing skills. This is where you find a hard consonant pronunciation and edit from one point in the recording to another. Keep one hard sound and remove the other. Experiment until you get good at it. Remember the undo button.
4. Remove superfluous information. People do not want to listen to long recordings but rather get your information in short bite sized segments. If you have a long message, consider editing it down to shorter segments and post them over a period of time. If producing an audio CD, use chapter marks to index your content and make the CD user friendly.
5. Edit with headphones. Headphones help block out distracting sounds and improve critical listening when editing for more precise edits.
6. Don’t be a perfectionist. There is a difference between being a professional and perfectionist. Ask yourself if you doubt the quality of an edit; do I understand what is being said?
7. Don’t try to edit quickly. In our You Tube video:

You may feel the edits are done quickly. That's because of 26 years experience editing professional products. Take your time at first and you will learn to be quicker over time. Quick editing is not necessarily good editing.

All good audio editors have one thing in common, experience. Don’t expect to be an expert after a few editing sessions. Keep on editing and over time, you will learn the tricks of the trade and edit quicker and more efficiently.

Audio Forensics: Accurate and Arguable

2010-01-04T08:12:00.000-05:00

Edward J. Primeau,
Primeau Productions, Inc.
www.VideoProductionPrimeau.com

Tel. 248-853-4091
Email: Ed@PrimeauProductions.com

Audio Forensics: An Accurate, Arguable and
Authentic Approach to Understanding Audio Evidence

Bell Labs was the first to discover that spoken word patterns and sounds could be identified and characteristics examined to identify the individual who made them. This has been a very important advancement in forensic science because the potential to assist law enforcement is well worth the effort it takes to defend the proponents and practitioners. Audio forensics is sometimes referred to by some as a “junk science.” After over 25 years of examining, editing and clarifying audio recordings, I can attest to and scientifically prove that voice identification and audio authentication comprise an exacting science that has huge benefit to the courts, law enforcement agencies and businesses.

In the following article, I will describe what works and does not work for two of the main activities of audio forensic experts: voice identification and audio authentication. I will also review and break down the steps and processes I employ and explain why I believe audio forensics is a valuable tool in litigation.

I have been retained for dozens of court cases, as well as by corporations, to analyze and help explain various aspects of audio evidence in one form or another. Some situations required that I find the truth about the source of a threatening voice, like a bomb threat called into 911 or a sexually harassing voice mail left on a victim’s phone.

Other cases involved defendants trying to validate or disqualify a pre-recorded audio confession. Evidential audio recordings all have one thing in common: they needed an experienced audio forensic expert to review and either qualify (validate) or disqualify the evidence. My job as an audio forensic expert is to determine the recording’s authenticity or to identify the person’s voice.

Voice Identification Overview
I have been practicing voice identification for over 25 years. Many of my skills and principles have been learned from employment as an audio engineer. Other skills I have learned through reading and studying to develop skills and completing successful cases successfully. I believe people's voices, just like fingerprints, can be identified through visual inspection of sound waves and spectrum analysis, as well as through critical listening skills. I have conducted voice identification for sexual harassment, workers compensation and employment harassment, as well as various threatening voice mail messages like bomb threats.

In our country today, we are guilty until proven innocent, the opposite of what our United States Constitution promises. It is my job to determine the truth about voice recordings using visual, electronic and auditory inspection of, both the evidence recording and an exemplar (voice sample taken for the purpose of comparison).

A typical case I would review might involve a telephoned bomb threat or harassing call that was recorded on audiotape or digital voice mail. After the police arrested a suspect, I would be retained by either the state (court) or defense to determine the truth about that audio recording.

The first step is to examine the original evidence and learn as much about the recording as possible. How was it created? Who created it? What machinery was involved?

Then, with the help of the court or defense lawyer, I create an exemplar of the accused voice to compare visual, electronic and auditory characteristics.
Almost every legal case I have been engaged in has allowed my report and or testimony into evidential status to aid with “due process.” I believe my success rate is high due to the fact that I employ the three testing platforms outlined above.

Steady advances in computer technology have had a huge impact on audio forensic voice identification. Having experience as an acoustic engineer who has listened to literally hundreds of hours of spoken word recordings, in addition to sophisticated electronic software programs, has contributed to my success with voice identification.

One case I examined involved a bomb threat. Bomb threats make up a fairly large segment of voice identification activity. The call in question was made from a pay phone outside of a convenience store to a 911 operator. This was scientifically evident when police traced the call.

The caller identified herself by name as an employee of XYZ Company. When the police arrived at XYZ Company, they found the employee with the name the caller gave the 911 operator and arrested her. The employee denied making the call.
She was charged with making a bomb threat call, guilty until proven innocent. I was retained by the defense to prove that our client did not make the bomb threat call.

Voice Identification Procedure
When comparing spoken word samples for the purpose of identification, I base my processes on historical information I have learned from the scientific community, state police crime labs, other forensic experts and designers and developers of electronic (especially computer) equipment and testing software programs.

My process requires the visual, electronic, and auditory examination of every aspect of the words spoken, not just the pathological examination. The words themselves, the way the words flow together, the pauses between the words, the way the words are formed by the mouth and larynx can be measured using three processes. The first process is a visual examination of the sound wave, comparing the evidence and an exemplar (a voice sample of the accused).

The second process is an electronic measurement of the evidence, which is then compared to the exemplar.

The third process is perhaps the most important: critical listening skills that compare the evidence and the exemplar of how the words are spoken and pronounced. Noise floor and electronic measurement of speech and other audible sounds in the recording must also be considered and measured.

Forensic procedure requires careful examination of all audio evidence characteristics, following procedures as outlined by the scientific community.

These scientific procedures begin with the analysis of the quality of the audio recording. It is important to establish that the quality of the recording in question is acceptable and workable. Sometimes, it may be necessary for an audio forensic expert to apply some light equalization or other non-destructive audio processing to reduce or remove background noise that may interfere with the forensic examination.

Voice identification requires the forensic examiner to discover similarities, as well as differences, in all three areas of investigation.
Here are the step-by-step processes I use when conducting voice identification:
1. Visual examination of the original recording, analogue or digital. This includes examination of the physical characteristics of the tape itself (if analogue) or analogue or digital recorder. It is important to examine the cassette tape (standard, mini or micro) or other analogue or digital source to determine if there are visual signs of tampering or alteration.
2. Once the physical evidence has been examined, the next step is to load the recording in question into a forensic computer. Visual examination of the sound wave, sonogram and spectrograph reveal speech characteristics and patterns of verbal delivery as well as electronic characteristics. At this point, the recording has been digitized so forensic software can analyze and conduct various tests.
3. If possible, for authentication or voice identification, an exemplar or comparison recording should be made of the original recording to compare the original recording characteristics. This same forensic examination process that is applied to the evidence is also applied to the exemplar to determine that the characteristics are the same and the recording is from the same audio recorder.
4. When conducting voice identification, it is important to create an exemplar of the accused for audio comparison using as exact conditions and equipment as close as possible to the measurements taken from the evidence as outlined above. The speech must be the same as the speech on the evidence in order for the testing to be accurate. As an audio forensic expert, I often have to coach the accused into the same energetic voice tone and inflection as the evidence recording. However, it is still possible to compare speech if the exemplar is not as close to the evidence as I would like.
5. Critical listening skills are used to examine the speech pattern, pronunciation, voice tone and inflection, accent, dialect and specific speech characteristics (like a lisp or significant “s” delivery). There is a rhythm in how an individual speaks, and even if s/he is trying to disguise his/her speech (in an attempt to fool the forensic examiner), the rhythm and speech patterns as described above still show through. The expert must pay careful attention to the rhythm of spoken word formations. I listen to single words as well as phrases and sentences.

I like to compare original evidence sections of spoken word recordings as well as individual words. This is best accomplished by editing exemplars and original recordings back to back. It is extremely helpful to then make these sub files of words and sentences within the section back to back with exemplars. I repeat the assembly over and over to accommodate critical listening skills with the auditory identification process. That way, your ear can experience the sounds, vowel formations and consonants without interruption.

There are many character traits that can be experienced in a spoken word recording. It is important for the audio forensic expert to become familiar with the evidence speech patterns and visual and electronic characteristics. These characteristics are evident in a person’s voice even if he or she attempts to disguise it and they are compared to the exemplar.

Audio Authentication
Using many of the same tools as described above, audio authentication can help determine the validity of audio evidence that is being considered as evidence in litigation.
When authenticating an audio recording, it is important that the audio forensic expert pay careful attention to tone consistency of the audio recorded signal (speech) as well as the recording’s noise floor.
The consistent audio-recorded signal is important because audio recordings that are not authentic are most always edited or fabricated assemblies of two or more audio recordings for the purpose to deceive the person(s) listening to the recording. Using the tools described above, the audio forensic expert can measure the tone consistency to determine authenticity.

Those same tools can also measure the noise floor looking for inconsistencies in the room tone or background noise of the recording. These breaks or changes in either audio recorded signal or background noise are signs that the audio recording being considered may be counterfeit or fake.

Critical Listening Skills
I have been working with professional speakers and analyzing other spoken word recordings since 1980 and have developed my critical listening skills to a degree that far exceeds the average person’s sound perception. When I first hear audio evidence and add exemplar recordings so I can listen to both back to back, then I apply my critical listening skills to determine the speech similarities as well differences between the two.

In my early days as an audio engineer, I learned to edit ¼” reel to reel tape with razor blades to make a recording sound as if it were recorded start to finish without a single mistake. Some of my edits were pretty tricky. I got so good I could split words in two and even three edits to fix a problem or shorten a script. After a while, I became very familiar with speech characteristics and patterns as well as vocal tone and pronunciation.

The best way to become skilled in voice identification is to listen to hundreds of hours of forensic evidence to become familiar with the various speech pathological characteristics and develop critical listening skills.

There can sometimes be differences in speech patterns that can help identify clues. Listen for several similarities as well as differences, such as nasal resonance differences and voice tone with regard to inflection.

Voice Identification Conclusions
When conducting the examination, the audio forensic expert must look for similarities as well as differences in all three testing platforms to help arrive at a conclusion.

After the investigation and testing procedures are complete, the forensic experts report must arrive at one of the following conclusions: positive identification, probable identification, positive elimination, possible elimination or inconclusive.

The key to successful voice identification is to develop a methodology and standard procedure that you strictly follow every time you conduct an identification and comparison.

Audio Authentication Conclusion
Every tone change in either the audio recorded signal or background noise must be documented and analyzed as a whole before considering the recording genuine or authentic. All forensic concerns must be documented and listed in the forensic report to prove the audio forensics findings.

The Audio Forensic Report
It is my belief that the audio forensic report should include:
1. The introduction: What the expert was asked to do and how the expert arrived at their conclusion, including all scientific fact.
2. The testing processes you employed to examine the audio evidence.
3. The expert’s conclusion of the tests, including the expert’s opinion as to the relevant facts and concerns.
4. The expert’s curriculum vita (resume) to establish credibility as an audio forensic expert, and to accommodate the Federal Court’s protocol for submitting an expert report.
5. A published article authored by the expert concerning the kind of testing relevant to the current case.

For more information contact Ed Primeau at 800-647-4281 or by email Ed@PrimeauProductions.com.