Explaining Forensic Audio (Part 1)

The concept of forensic audio investigation may have become popular in recent years along with the forensic sciences in general but it’s been in practice since World War II. With audio use in full swing for radio transmissions across long distances, scientists were trying to identify the voices of their enemies among the many radio broadcasts that took place on open frequencies. The work done in forensic audio investigation today is based on the pioneer work of those scientists.

Specifically, forensic audio has to do with any type of audio of an evidentiary nature. In modern cases, law enforcement or other legal professionals (e.g., defense attorneys and prosecutors) will turn to a forensic audio examiner to perform any one of a number of services where audio is concerned.

In many cases these specialists are hired on a contract basis.

While the most common Hollywood portrayal is audio enhancement with a few twists of a knob (if only it were so easy) there is a great deal of work that can be done:

  • Audio Enhancement – the most common and offered by just about every forensic audio company you can find.
  • Audio Authentication – geared toward tape and digital formats
  • Forensic Transcription
  • Speaker Identification

There are also a number of other services or procedures that can be classified in their own right as a specialty process or “miscellaneous” in terms of categorization. This article will focus specifically on Audio Enhancement and Authentication.

Audio Enhancement
Audio enhancement is the most common and well known service where forensic audio is concerned.

It’s not likely that one can take a garbled and mangled inaudible conversation and “tweak it” to produce clear speech that is intelligible. While audio enhancement isn’t specifically focused on speech, that is usually the intent behind cleaning up or enhancing audio for legal purposes. It’s a means of reducing or filtering out unwanted noise from a poor recording in order to clear up the speech that’s covered with noise or is a victim of poor recording methods.

A forensic examiner is not a miracle worker however, and while modern software and equipment has provided a variety of tools to improve the quality of speech in a recording, there are still limitations. When it comes to enhancing speech, you can’t fix something that’s just not there. If the recording doesn’t contain the robust elements of someone’s speech, and the equipment only picked up bits of a word or phrase, there is no magic software to fill in the blanks. Enhancement techniques can sometimes have fantastic results with intelligibility, but more often would be a disappointment to the layperson.

In terms of speech enhancement, an examiner can offer critical listening in combination with forensic transcription and speech decoding methods to help identify and discern what is being said. Again, technology can only do so much so an examiner with linguistics and phonetics experience is usually best for the job. However, if the speech waveform isn’t picked up by the recording device or is masked by noises of the same frequency range, he won’t be able to decipher the speech.

Forensic audio enhancement sometimes simply involves increasing the volume of a whisper from a suspect where traditional playback – even at high volume – can’t help an individual understand the utterance. Audio enhancement offers the most benefit in situations where noise can be eliminated or at least reduced so as not to distract the listener from the speech. Enhancement techniques are quite good at getting rid of electronic buzzing or hum and other noises such as tape hiss, the crackles and pops of a phonograph record or the beeping of a backing truck, open car door, low battery warning of a fire detector, etc. Enhancement used in this way is often called improving the listenability of the recording. Unintelligible speech isn’t made intelligible but the recording is easier on the ears.

Audio Authentication
Authenticity is an important part of legal matters where evidence is concerned. This is especially true when it comes to audio that is or will be entered into evidence in a criminal or civil matter. As technology advances, it becomes progressively easier for an individual to tamper with a recording.

Audio authentication – either involving tape authentication or digital file authentication – is a way to ensure that the audio being utilized as evidence has not been tampered with in some way.

Not only will a forensic audio examiner use software to examine the actual recording, but authentication involves examining the physical tape itself and its casing.

This includes:

  • Checking the tape for splices
  • Examining the tape’s plastic shell to check for prying or disassembly
  • A process of examining the tape call magnetic development

Magnetic development involves using a magnetic liquid called ferrofluid in the examination of audio or video tape. The ferrofluid allows the forensic examiner to see the magnetic patterns on a tape. The types of things the audio engineer would look for include magnetic signatures left by stopping, pausing and starting the recording process. It can also be possible to tell if the tape has been recorded over or simply erased and left blank.

Newer software provides an edge when it comes to detecting authenticity in audio as it looks into variances that could lead to falsification of a recording – particular in tape recordings:

  • Equipment noise – hums, pops, varying pitch in inconsistent forms over the whole of the recording
  • Fading – Any gradual or sudden decline in volume that effects the interpretation of noise or dialogue. If the sound cuts out completely that becomes a gap in the recording
  • Gaps – Any segment where there is a change (often unexplained) in the content or context of an audio recording. A perfect example of this is the infamous Watergate recording where there is an 18 and ½ minute gap in the recorded audio that was later discovered to be an overlaid recording of electrical interference.
  • Transients – These are clicks or pops and other “attack” sounds within a recording and may signify that there has been a splice or some other alteration to the recording

There are a number of methods that are used to authenticate a recording, checking it specifically for originality. An obvious and important tool that a forensic audio examiner has is the ear. Critical listening affords a great deal of benefit and it takes training and experience to know what to listen for while playing a track over and over.

In some cases, an examiner may have to run through a section of audio many dozens of times. They examine bits of a conversation or sections of a recording to fully understand the sounds – including both foreground and background sounds. If something stands out the examiner will further investigate that specific segment using their trained ear to discern if the recorded event is authentic or not.

Beyond listening, the examiner utilizes physical inspection as well as spectrum and waveform analysis to visually inspect the quality and construct of a specific piece of audio. All of these methods come together allowing the examiner to certify the authenticity of a tape recording.

Things become more difficult when a recording is made using a digital recorder that creates audio files such as.wav or.mp3. While many of the above methods may be useful with a recording that originated as a digital file, it is somewhat easy for a knowledgeable person to edit the file without leaving any known sign of doing so.

One promising method of digital authentication is the use of ENF (electric network frequency) data. Whenever someone is recording while plugged into an electrical outlet or using a battery operated device within an ENF magnetic field, their recording will include a 50Hz or 60Hz (depending on country) waveform signature. This signature can be compared to an ENF database to possibly determine where and when the recording was made, whether it’s an original or a copy, or whether it was edited or altered in anyway. Digital audio authenticity examination, and more specifically the use of ENF, is in its infancy and has a way to go before forensic audio examiners reach the level of sophistication that has been achieved with authentication of analog tape recordings.

The use of software to determine authenticity and enhance audio is just the beginning when it comes to forensic audio. Depending on the situation, additional specialty services or skills may need to be applied such as speaker identification and the analysis of gunshot sounds to determine if more than one weapon was used, which type of firearm was used, or the sequence of the shots fired. Forensic audio is a robust trade that encompasses a number of specialists who work together to bring clarity through the study and examination of audio.

A Growing Need for Audio Transfer Services

It may seem like old hat, but many individuals and organizations still have dated audio collections on old analog formats like 8-track, reel, microcassettes, standard cassette tapes and digital tape like DCC or DAT (digital compact cassette and digital audio tape respectively.) With technological advancements, there is a growing need for audio transfer services to get old music and speech moved into modern audio formats.

Damage and Corruption of Tape

Traditional tape recordings can develop problems as they age, especially those that have seen heavy use or weren’t carefully stored to protect them from contaminants and environmental conditions. As these tapes are often mishandled over the years they’re far more likely to suffer a loss of quality or breakdown completely.

Tapes simply don’t age well, and their condition certainly doesn’t improve. As time progresses, problems can arise with magnetic tape such as “Sticky shed syndrome” or “vinegar syndrome.” Technical names aside, the result can lead to a complete loss of the original recording. That’s why it’s a good idea to back up analog recordings with audio transfer services.

Outdated Tape

For every bad tape and lost recording there are tapes in excellent condition. With advancements in technology older formats become obsolete and as they break down people have been left without the equipment to play the tapes. For many formats, only used models are available and can come at steep prices. There will come a time where equipment won’t be available at all.

Otari, Inc. is the only manufacturer still providing reel to reel tape decks. Elcaset, DCC and the better known 8-track players are no longer being manufactured. Parts are no longer in circulation and must be stripped from other machines. Over time, even that will become extremely difficult as the machines disappear from the market. While professional audio transfer services have these units available to move audio for customers, it’s best to change formats as quickly as possible once your old audio has been moved.

Recordings – Music & Speech

While the professional sector has accumulated a lot of analog audio over the years, there are millions of recordings – both music and speech – that have never been converted to a digital format. These analog recordings range from local bands that were never signed to speeches made by friends, family, colleagues, teachers, historians and more. Anyone who would like to listen to those pieces would need some dated technology, or have the audio transfer done to digitize the speeches and music.

Audio transfer services can help individuals and organizations reclaim content and recordings that have been lost to time including oral histories, interviews, sermons, audio journals, speeches and more. Much of the analog content that’s floating around out there is a part of someone’s history, and audio transfer can preserve that.

Audio Transfer and Restoration Service Providers

If something has been recorded, then there is likely some measure of importance to that particular piece. That audio should be transferred into a digital format as soon as possible. While a recording might be fresh, the tape could still be aged which could cause even new audio to degrade. Because of the variety of analog formats, it’s necessary to do a little research into a variety of audio transfer services. Some work with only limited formats while others have access to all the necessary equipment to handle outdated and rare analog formats.

While it’s entirely possible to transfer your own audio, the quality of the transfer will be limited by the equipment and how the content is handled. For better quality and to ensure the integrity of the audio, it’s best to use professional audio transfer services. Most services use professional grade equipment with external audio interfaces that provide the optimal transfer of quality, far superior to a transfer made using a standard home PC.

Physical damage and issues with tape can cause the most problems, and a professional audio transfer service has the engineering experience to handle a tape properly, repair it if necessary, and transfer the audio. Should the defects of the tape create problems in the audio, the engineer might be able to use restoration software to repair the audio, restoring it to the original quality of the recording.

Aging Digital Formats

While it’s important to backup and transfer analog audio recordings, mini-disc and digital tape formats that are becoming obsolete should be transferred as well. Some formats are already quite obsolete. DCC comes to mind here. The manufacture of Digital Compact Cassette players was halted in October of 1996 and there aren’t very many units out there.

Very few mini-disc players are being produced now and DAT has been discontinued. In fact, Sony stopped manufacturing DAT machines at the end of 2005. It’s important to transfer audio sooner rather than later and over time, even professional audio transfer services will have a difficult time converting tape recordings and mini-discs to a digital file format due to a lack of support for the equipment.

Complete Guide To Evaluating The Best Web Audio Software

Web site audio can really make an impact on your customers when they visit your site. In fact, it can change a simple visitor to a customer. The correct web audio software can do this for you. It’s an easy way to add audio to your web site.

And, I’m not just talking about some boring voice recorded audio. I’m talking about “professional” audio with lead-in music, background music behind the voice recording, and fade-out music at the end.

This is streaming audio that plays automatically when a visitor goes to your web site or when they click the “play” button. It’s your choice as to which happens when visitors come to your site. This is audio that sounds like it was done in a professional recording studio, and no one has to know that you’ve done it on your computer.

I’m thinking about phenomenal audio created and put on your web site with quickness and ease by anyone…even someone who isn’t technical. This is “web audio” at its absolute finest. Would you rather listen to a voice only recording or a voice with pleasing and smooth sounding music lead-in, background, and fade out that creates the emotional response that turns visitors into buyers?

Web audio is booming for Internet radio stations and online music distribution. However, few mainstream web sites include sound. If it’s booming, getting tons of traffic for special audio focused sites, and keeping visitors on the site longer, it only makes sense that it can do the same for your site, doesn’t it?

The “secret” to putting audio on your web site is to find an easy to use software created for this specific purpose. There is a wide variety of software to do this. There are even some services that you subscribe to on a monthly basis to accomplish this. I definitely recommend using your own software instead of paying monthly fees. Why pay every month when you can simply pay one extremely small fee for the software to use over and over again on as many web pages and web sits as you want?

To make it easy for you to evaluate web audio software, simply look for every one of these features. When you find them all in one software, you know you’ll have found the best product for the purpose.

  • All In One Solution. Record audio, add one of many included background music styles, and easily choose the color, shape, and size of the player. No other expensive and cumbersome external software or service needed!
  • Stream Audio Immediately. You choose whether your audio starts as soon as a visitor comes to your site or the visitor clicks the play button for it to start. Either way it starts in seconds and makes its impact.
  • Various Styles of Professional Background Music. The software should include at least 10 music loops. These should reflect different musical types and pace to fit different purposes.
  • Ability to customize audio players. With the right audio software, you can customize your audio player. You can choose from multiple player styles, any color you like, and you can also size your player to fit in any location on your web page.
  • Automatic fadeup and fadeout. Got a killer voice-based marketing message with a perfect introduction, message, and closing? With professional fade up, background, and fade out music added to it, you’ll get your visitor’s attention right away. With this professional touch you’ll help close that sale.
  • Players Galore On A Single Page. There are so many uses for audio on a web page that, of course, you want this capability. You’d be amazed at all the audio software that don’t let you do this. Be certain your software includes this “must-have” feature.
  • “Jump” To A Web Page Automatically. Wouldn’t it be great if right after the audio finishes you could automatically jump to a specific web page? Now you can. Just be sure the software you choose has this option. Use it to capture leads, affiliate marketing, teleseminar playback…and other traffic driving uses.
  • Use your existing audio files. Your audio software, of course, must let you record or brand a new audio file with the program itself. In addition, though, you can make use of any existing MP3 or WAV audio file on your computer.
  • Monthly Fees – Who Needs Them? There are services that charge monthly fees, and add-on fees, to host your audio. You don’t need to pay this month after month. Simply pay a one time investment to purchase the software with all the capabilities listed above…and no continuing payments, ever.

I use the following philosophy in business and now adapt it to Internet marketing: “When you see a great tool to develop an aspect of your web business, get it, use it. If you see a better tool, get it, use it.” This will advance your business more quickly than anything else.

Now that you know all about web audio software, go get the software and use it. You’ll be glad you did.