You can see these ratings behind the title of each EVP.
Class A: These recordings are loud, clear, and easy to understand and sounds like natural speech.
Class B: Recordings rated B are of a lower volume and may be warped and harder to understand than A and/or are quite faint and it may take more than one listen to hear it.
Class C: Class C recordings may be almost impossible to understand except for maybe a word or so and/or may be very faint. They are of a low volume and/or excessively warped.
Class DC (Direct Communication): The voice clearly answered a question or directly responded to something said.
Class PC (Personal Communication): The voice clearly said something meaningful directly to someone that was present (whether to another spirit or one of us).
Class RC (Random Communication): The voice answered no direct question and their comment appeared to be aimed towards no one and was completely random.
Morph: The voice or words of the person recording are different or changed then the words that they actually spoke.
ERV (Event Related Voices): Events such as someone coughing or the passing of a car or the wind seem to trigger the EVP.
CHR (Chorale): Two or more voices are talking at the same time, either saying the same thing or something different.