When one embarks on an investigation, there are often hours upon hours of collected data that has to be painstakingly sifted through, looking for that response, that one that makes you question, "was this intelligent?"
The task of listening through hours of recorded audio is gruelling, can be boring, but the drive and focus has to remain. You must ensure that you keep your spirits up ('scuse the pun) as well as your energy levels. Keep a readily available stock of food and refreshments available, but be mindful of not eating during your listening session, as the sounds from chewing etc. are amplified in your headset.
Listening for something for an extended period can quite frankly exhaust you, it is important to take regular breaks as opposed to hours of straight analysis.
It's important to use the best quality equipment that you have available and at your disposal. Also look at external factors such as ambient noise, flooring, wind, and the list goes on. Quality equipment makes your analysis at the end of the day just that much easier! Invest in a great pair of over-ear headphones.
Importing your audio into a software such as Adobe Audition or Protools, or even a free solution such as Audacity assists you in scrubbing through, finding points of interest and marking them as such, slowing down, changing pitch etc. as necessary to assist you in understanding a potential EVP. A good rule of thumb however is that if it takes too much manipulation, over and above amplification, then it's considered to be of a low class, and should be discarded. The Class A EVP's should not need any sort of manipulation.
Audio software also provides a form of visual representation (waveform) to assist you to, at a glance, see anomalies in the audio, or sections that may need closer inspection.
Looping is also a useful feature, where you may need to listen to a section over and over again to properly interpret what was being said, for example, "bread" or "dead". Slowing down audio assists you in establishing the first letter of the spoken word, and you'll be able to figure out the rest from there, as is relevant in the above example.
The Digital Age really has improved upon systems and formats that make it that much easier for analysts. A great example of this is hiss reduction, noise reduction, and an array of other filters/equalizers that fit the bill. Equalizers allow you to amplify or soften any range of frequencies, this is great for targeting voices, pitch etc.)
Compressors allow you to "flatten" out the sound, making all of your audio the same amplitude within a determined range of volume. If there is a very soft sound that happens, perhaps a thud in another room, you can enhance it to the point of identification.
There are all kinds of plugins to tackle almost any problem when it comes to audio. Echo or Reverb can be removed, Native Spectrograph or Spectrograph plugins allow you to cut out an obtrusive sound, such as someone speaking over a potential EVP.
As mentioned before though, those EVPs that require the least manipulation are where it's at for the purists.
Collaborator: Theo Meyer