Room Tone – The Spaces In-Between
Room tone. The sound the room makes? Surely that should be a big fat nothing, right? Well, in a well-isolated professional recording suite the sound will be very low, but even the movement of the air makes a sound.
On top of that, there is the sound generated by the equipment. All microphones have “self-noise” – electrical noise generated by the electronics inside the mic – and of course the preamp/interface it’s connected to will have self-noise of its own.
The Spaces Between Phrases Aren’t Really Silence
Take a look at this lovely piece of spoken-word audio:
The bit between the two phrases looks like silence, yes? But see what happens when we look closer by increasing the vertical zoom:
Zoomed in, we can see that’s not silence at all. It’s noise.
That noise is made up of microphone/preamp self-noise, narrator breathing (very quietly in this case) and the inherent noise of the room itself. The ambiance. This is called room tone. It’s the ‘air’ around the voice.
Must you do anything about it?
The obvious answer would seem to be to leave it alone if it’s not intrusive, or cut it out if it is. But you can’t just literally cut it, like this:
…because this replaces the room tone with actual silence – digital zero. Doing this creates an audible difference in tone, sometimes described as feeling like the floor has fallen away from under you. Even if Audible were to accept a file like this (and it’s unlikely), it is extremely bad practice and should never be done.
So leave it alone, yes? Maybe. One of Audible’s technical requirements is that room tone should be no higher than -60dBFS. So if you’ve got sections where the room tone is above -60dBFS, measured by the meters in your DAW, you need to deal with it.
How you deal with it in a way that sounds right and is acceptable to Audible will be discussed in the editing section articles.
One More Thing
General air movement and the ‘shush’ sound of the electronics is easily ignored by the human ear. But a particular pitched sound like a buzz or a hum may be distracting (and thus not acceptable in your audiobook) even if the actual level reads below -60dBFS.
Why you need to care
Room tone is the sound you hear when the narrator isn’t speaking. It has to be consistent, it has to be below -60dBFS on the finished master audio, and it can’t contain anything the ear can focus on, such as a buzz. Loud or intrusive room tone will either get your audiobook rejected, or if it passes, poor reviews.
<<back to digital full-scale and headroom
on to file formats and bit depths>>
*I do try to resist my natural tendency to get over-technical and indulge my love of facts and figures. If there’s something you think I should go into more deeply, drop me a line or write a comment.
Justin Hill has been in the recording business for more years than he likes to talk about but has traded as The Other operation since 2013. In early 2020, just as the COVID lockdowns started, he decided to build a dedicated spoken word studio.
Despite materials and equipment suppliers either being closed or having no stock, and delivery drivers being unwilling to come to the door, Landen Park Studio actually got finished and had its first session in August 2020.
Since then, Landen Park Studio has recorded countless audiobooks and hosted countless voiceover sessions with Justin Hill at the helm. Many of these audiobooks have been self-narrated by authors who’ve never recorded an audiobook before.