The existing noise in a transmission media. In telephone lines, this is usually heard as the background "hiss" & is due to electrical signals traveling down the line. Also called "background" or "white" noise.
The lowest background noise level in a space, which is a composite of sound from sources both near and far, but none of which are identifiable as being from a specific source, such as a nearby ringing phone.
The total of all noise in a system or situation, independent of the presence of the specific sound to be measured. In acoustical measurements, strictly speaking, ambient noise means electrical noise in the measurement system. However, in popular usage, ambient noise is also used to mean "background noise" or "residual noise."