What is room tone and why does each file need it? (ACX)

What is room tone and why does each file need it? (ACX)

The following article is a slightly edited version of a post originally shared on the ACX site.

Room tone is the background noise in a room. It is sometimes referred to as the noise floor. For audiobook purposes, room tone is the sound in your studio when no one is speaking (or breathing). It should not be absolutely silent, because that is not something that occurs in the real world. In fact absolute silence is almost as jarring/distracting as a noise floor that is too loud. Generally speaking, we want the room tone to be quiet enough to not be discernible to the listener.

ACX requires that each file must have 0.5 to 1 second of room tone at its beginning ("head") and 1 to 5 seconds of room tone at its end ("tail"). I've standardized this for myself to be 0.6 seconds at the head and 4 seconds at the tail.

This space is required to ensure titles are successfully encoded in the many formats made available to customers. It also gives listeners an audio cue that they have reached the beginning or end of a section.