threshold of pain
Human hearing is determined by the sound pressure, the loudness perception of which is reflected in the hearing characteristic. The hearing characteristic is limited by the hearing threshold and the pain threshold.
The pain threshold is the sound pressure at which the volume causes pain. It is frequency dependent and falls at higher frequencies, and it also depends on musical taste. Generally, the pain threshold is considered to be 130 Decibel Sound Pressure Level( dBSPL), which drops to 120 dBSPL at higher frequencies. The sound intensity level at 120 dB is 1 W/m2.
As a rating for excessive sound levels that could reach the pain threshold, there is the dB(C) rating curve, which gives a loudness rating at 90 phon.