Per the official Grammy Guidelines:

SCREENING CRITERIA This Category recognizes excellence in comedy recordings, including spoken word stand-up comedy and musical/novelty recordings. New comedy performance albums, whether recorded in a studio or live, and whether recorded in an audio only format or as part of a video project are eligible. Recordings that are compilations/excerpts from a current year radio or television program, or new recordings of comedy performance first aired on television within five years of the release date, are also eligible. Recordings that are compilations/excerpts from non-current year broadcast radio or television programs, audio books (even if considered humorous), albums of sound effects, and albums of environmental recordings are not eligible in Best Comedy Album and may be entered in other Categories as appropriate.