1The acoustic quality or ambience of a particular room.
2Sound Recording (especially in film production) the ambient or background noise occurring naturally in a particular environment, recorded without foreground noise (such as dialogue) in order to aid the editing process.
Origin
1920s; earliest use found in The New York Times.
Definition of room tone in US English:
room tone
noun
1The acoustic quality or ambience of a particular room.
2Sound Recording (especially in film production) the ambient or background noise occurring naturally in a particular environment, recorded without foreground noise (such as dialogue) in order to aid the editing process.