We use a VENTILATION system for our vocal booths, NOT an a/c unit. Many people have the misconception that the ventilation is air conditioning. The ventilation fans are utilized through a push/pull system. One fan pulls hot air out of the booth, while the other fan pushes cool air from the outside room into the booth. The inside of the vocal booth will only get as cool as the temperature outside the booth. The ventilation fans are completely covered by muffle boxes. This way, you don't hear the fans while you're recording.