Noise Floor
Definition
The level of background noise present in an audio system or recording environment. Determines the lower limit of the dynamic range — any signal below the noise floor is masked by the noise and cannot be heard distinctly.
In Simple Terms
The baseline hiss or hum always present in any audio system. The quieter your noise floor, the more detail you can capture and the cleaner your recordings sound, especially in soft, delicate passages.
In Practice
A microphone preamp with a low noise floor allows quiet acoustic instruments to be recorded at safe levels without audible hiss appearing in the final mix.