EVPs (Electronic Voice Phenomena) are a lot like people. They all different and come in
many shapes and sizes, but in many respects they are all the same. Although all EVPs share many of the same characteristics they do vary in quality.
Below is a chart to explain what the difference is between what is called a Class A EVP versus a Class B or even a Class C.
Class A EVP:
In a Class A EVP the voice is clear and easy to understand. In a Class A EVP no amplification is required. An example of a Class A EVP is below.
Class B EVP:
Class B EVPs are loud and rarely need enhancement, but are not readily understood and tones can be hard to understand. It may have to be heard several times to understand the word or phrase.
Class C EVP:
Class C EVPs are very faint and can only be heard and understood once they have been enhanced. WISPS does this by isolating the EVP in the audio file, and boosting the volume of the EVP. Even with the enhancement headphones may be necessary to hear and understand the EVP.
Class D & G EVPs:
There are two other classifications of EVP that will be covered in this chart. These are Class D, and Class G EVPs. These are EVPs that are of questionable evidentiary quality and won’t be used on the WISPS website. The ‘G’ in Class G specifically refers to garbage, meaning they may not even be EVPs. Class D are likely EVPs, but are so faint, and/or unintelligible to be of little value. Class D EVPs may need enhancement and some audio filtering. Even then they are difficult to understand. They are of questionable value.
Type R EVP:
Some EVPs become intelligible when played backwards. These are Type R EVPs. WISPS has not found this type of EVP to be common. A Type R EVP can fall under any of the other classifications.
With experienced investigators it is relatively easy to eliminate contamination, especially with smaller groups of people. This can be more difficult with investigations open to the public, new investigators, larger groups, naturally noisy venues and even experienced investigators can sometimes forget to mark their contamination on an audio recording. Contamination consists of noises on an audio recording made by people which can be mistaken for EVPs. These can consist of whispers, bodily noises, and other forms of audio contamination.
New investigators should be trained never to whisper at an investigation, and all investigators, should as second nature, call out, and mark any contamination on a recording. This can be easily done, such as telling people not to whisper when it is happening. This allows someone reviewing potential audio evidence to quickly identify and dismiss contamination.
There are some cases, where contamination could potentially be present. If the analyst reviewing evidence is unsure whether they are hearing an EVP or contamination, and if they can’t determine what the audio is it has to be dismissed as inconclusive evidence. When in doubt throw it out. Good evidence can potentially be lost by bad investigative process or investigators failing to mark contamination. WISPS has only had to do this on rare occasions where some investigations have been opened up the public.