EVP classifications varies :Class A; A clear and distinct voice or sound recorded on a recording device and not usually heard during the EVP session Because these are easy to understand by all without being told or prompted to what was said or the noise being made usually heard without headphones or any clean up of recording.
Class B; A voice or sound that is distinctive and fairly loud.This EVP is more common and can be heard by most people after been told what to listen for,it is usually audible to the EVP Tech who have been trained in the skill of EVPs .It sometimes can be heard without the use of headphones.
Class C;A whispery faint sound or voice that can be barely heard and is sometimes indecipherable and inteligible to the ears .It may have paranormal characteristics,such as mechanical sound or electronic noises sop may apply objectivity to these a disregard them but would save EVP to archives for references purposes and study.
VIPS also breaks down EVP by Direct responces during Communications Sessions.DRCS
EVP directed to someone by name personal contact DPC.
Also Comment by an action to what someone has done Reaction RAC.
Levels:#1 Loud ,clear and easy to understand includes whispers and fast speech.
Level #2 Lower volume possible warped but still understandable.
Level #3 Very low in volume hard to understand and excessively warped or morphed.
These are the EVP classifications used by VIPS and most recorded EVP are short in length and preceded by a noise click,thud,most in a male or female voice but not excluded to, usually in a frequency different from the normal human voice range frequency.