Room tone: what it is and how to record it

Room tone is a recording of your room with nobody speaking: the same microphone, in the same place, at the same gain, just silence from you. It sounds like nothing, but it isn’t nothing. Every room has a faint sound of its own, a mix of air, distant traffic, the hiss of the microphone and preamp, and the room’s own echo. Your narration is recorded on top of that sound, so every pause in your reading contains it.

Why audiobooks need it

• The start and end of every file. ACX asks for 1 to 5 seconds of room tone at the beginning and end of each chapter file. It gives every chapter a natural start and finish instead of an abrupt cut.
• Filling edits. When you remove a mistake, a cough or a chair creak from a pause, you need something to put back in the gap. Room tone matches the pauses around it. Digital silence doesn’t.
• Noise reduction. Noise reduction works by learning what your room sounds like and turning that sound down. Room tone is the cleanest possible example to learn from.

Why not just use silence?

Because listeners hear it. When the background sound of a pause suddenly drops to complete digital silence, it sounds like a dropout, as if the audio cut out. On headphones it’s obvious. Some publishers’ technical specifications go further and set a lowest acceptable noise floor as well as a highest one, so pauses can’t be dead silent. The goal is quiet pauses that still sound like your room.

How to record room tone

1. Record it at the start of every session, after you’ve set up and before you start reading. Ten seconds or more is plenty.
2. Change nothing. Same microphone, same position, same gain, same headphones plugged in, same fans off. Room tone is only useful if it matches the narration around it.
3. Stay still and quiet. Sit where you’d sit to read, breathe gently away from the microphone, and don’t move your chair or touch the desk.
4. Record new room tone whenever something changes: a new day, a different room, a moved microphone, the heating switching on, or an air conditioner you couldn’t turn off.
5. Listen back on headphones. If you hear a car, a bird, your stomach or the refrigerator kicking in, record it again.

Common mistakes

• Room tone from a different day. The room sounds different from session to session. Use the room tone recorded with the narration you’re editing.
• Room tone at a different gain. If you change the microphone level, your old room tone no longer matches.
• Muting noises instead of replacing them. Muting a click in a pause leaves a hole of dead silence. Replace it with room tone instead.
• Too short a clip, looped obviously. A one-second clip repeated over a long gap can be heard cycling. Record ten seconds or more.
• Forgetting it entirely. If you did, the quietest stretches between your sentences are the next best thing. Software can find and use those.