The volume of noise energy, expressed in decibels, above a reference level.
the amplitude level of the undesired background noise
Acoustical decibel level of a source of noise, measured according to the applicable ISO standard.
Usually given in Decibels ( dba ), the noise level gives you an indication of how much audible noise a power supply will generate when running. Typically 20dba is fairly quiet, 40 dba is fairly loud. For PCs that are to be sited in living rooms as media centers it is advisable to obtain a PSU with as low a noise level as possible.
Roughly, the amount of noise power in a signal. The noise level is a limit where simple power measurements start to have trouble measuring the signal.
In telecommunication, noise level is the noise power, usually relative to a reference.