Audio recordings are very helpful in an investigation. There are two (2) types: Disembodied Voice and the Electronic Voice Phenomena (EVP).
This occurs during the investigation and is heard by people in the room Often the sound is not captured on video or a digital voice recorder.
Electronic Voice Phenomena (EVP):
This occurs during the investigation; however, no one hears it. It is only afterward when the investigators are reviewing the evidence that it is heard. It can be captured on video or on digital voice recorders.