tonistry.

Specs & measurements

Noise floor

Also called background noise, hiss, black background

The noise floor is the faint hiss or hum a system produces with nothing playing. A low noise floor, sometimes praised as a "black background", lets quiet passages and reverb tails emerge from silence instead of from hiss.

403020100−10−20dB SPLsame amp noise: 5 µV−9 dB SPL300 Ω headphone97 dB/V22 dB SPLsensitive IEM128 dB/Vthresholdof hearingaudible hisssilent
The same 5 µV of amplifier noise plays at about −9 dB SPL through a 300 Ω headphone of 97 dB/V sensitivity, below the 0 dB threshold of hearing, but at about 22 dB SPL through a sensitive IEM of 128 dB/V, where it is audible hiss.

Every amplifier and DAC generates some noise. Whether you hear it depends on the headphone: a 300 Ω headphone with modest Sensitivity hides noise that a sensitive IEM makes obvious. The same desktop amplifier can be silent on one and hiss on the other.

Measured in microvolts of output noise or as SNR, the figure is only half the story; what counts is noise relative to how loud you listen. Owners on audiophila. rate noise floor on a scale, which also catches hum from ground loops and interference that a bench measurement might miss.

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