Audio Forensics – Preserving Audio Authenticity

One of the most overlooked issues in using digital technology for audio recordings is retaining the original recording’s authenticity. This has been a problem for printed media, such as books and historical documents, but audio recordings have become increasingly popular as a way to casually read a book or get news and information from the world around us. How do we keep and know that the audio recording we are listening to is actually what the speaker said and has not been altered in any way?

Like video recordings, it is often difficult to tell whether the original audio file has not been changed. There are free audio editors that allow someone with very little knowledge of audio technology to change the pitch, tone, and even the speed at which someone is talking. Unless you are an expert in the field, you are not likely to be able to determine whether the audio recording you are listening to is original or has been changed for nefarious purposes.

There is some good news on this front, provided by audio experts specializing in audio forensics. I should point out that this is not a solution to creating a means of audio recording authenticity, but ways we can immediately deal with the problem of audio authenticity in a digital world.

The first approach is to establish what is called a “chain of custody.” As criminally oriented as this term may sound, it is quite simple but does require a good amount of effort on your part. The question to ask is, Who was the last person to handle the recording? If it was the original author, you can stop your search. Otherwise it may take some serious investigative work to determine the probability of whether or not the content has been tampered with in any way.

Even if you fail to trace the recording back to the original creator, you can use a simple piece of technology to listen to the recording and find hints that the recording may not be authentic. A free program such as Audacity will allow you to visually see the voice patterns of the speaker. Now you don’t have to be a forensics expert to do this. In fact, all it requires is some of your time and patience. Play the audio file back using the audio software and listen for places where the audio does not seem to sound consistent. Only use your ears to do this. The audio software will help you mark the places where you believe there are irregularities.

You may have to listen to the audio several times to get a more precise sense of how the speaker speaks, his tone, and his style. Do not place too much emphasis on pauses or breaks in the audio, as the author may have paused the recording while they were speaking and did not edit the pauses to ensure a smooth transition during playback. One area you can pay close attention to, though it is not possible on every audio recording, is to listen to the background noises. If there is an abrupt change in the background, you have good reason to believe it is not a copy of the original recording.

These basic tips will not make you an audio forensics expert, and they can require a good bit of your time. But if knowing that the recording you are listening to is 100 percent authentic, the time spent will go a long way to assure you that you are listening to an unedited, untampered with version.