Noise floor

Noise floor is the level of ambient noise in an audio system – the hiss, hum, and electronic noise present when no music plays.

Measured in dB below full-scale (dBFS)

• -60 dBFS – audible hiss at moderate volume, ok for TV audio
• -90 dBFS – CD quality, only audible in silent room at high volume
• -110 dBFS – hi-fi quality, essentially inaudible
• -120 dBFS – reference-tier, below human hearing threshold

Where noise comes from

• Power supply ripple
• DAC dither/quantization
• Amp gain stages
• Ground loops (60 Hz hum)
• External RF interference

Practical relevance

Any modern hi-fi component achieves noise floor well below hearing threshold at moderate listening. Systems that hiss audibly at normal volume have a specific problem (bad amp, ground loop, poor DAC).