One of the benefits of using an audio recorder during an investigation is that it gives you another chance to hear something you might have missed at the time. Have you ever been on an investigation and someone has asked, "Did you hear that sound?" As soon as they mention it, you recall it, but at the time you weren't consciously aware of it. This is due to the Cocktail Party Effect.

The effect describes an ability of the human brain that allows us to focus our auditory attention on one particular stimulus while filtering out a range of other stimuli. This is most obvious at a party when you are able to hold a conversation with a single person while other partygoers chatter all around you.

It's for this reason that you might be listening to someone call out on a vigil and perhaps even waiting for responses through a spirit...