In the lexicon of psychoacoustics, the sone is a deceptively simple creature. Unlike the decibel—a relative measure of pressure—the sone is linear. One sone is defined as the loudness of a quiet, 1 kHz tone at 40 dB SPL. Two sones sound twice as loud. Forty sones sound forty times as loud.
But what happens at ?
Do not go there without protection. And if you do? Do not expect to hear silence again. sone - 187