Human hearing operates near the theoretical physical limits imposed by thermal noise

Evidence

At 4 kHz, which is about the frequency of the sensitivity peak, the pres­ sure amplitude variations caused by the Brownian motion of air molecules, at room temperature and over a critical bandwidth, correspond to a sound pressure level of about 23 dB. Thus the human hearing system is close to the theoretical physical limits of sensitivity. In other words there would be little point in being much more sensitive to sound, as all we would hear would be a “hiss” due to the thermal agitation of the air! Many studio and concert hall designers now try to design the building such that environmen­ tal noise levels are lower than the threshold of hearing, and so are inaudible. — David Howard, Jamie Angus, coustics and Psychoacoustics, 635

Categorization

• CANDY: Great conversation fact: we can’t hear more sensitively because the air itself would hiss from thermal motion.
• XREF: Connects to the idea of absolute silence from the noise/silence books — the floor of audible silence is thermodynamic, not acoustic. — connects to: Human hearing detects pressure changes of a few parts per billion
• corroborated: 2 independent passages support this claim — David Howard, Jamie Angus, coustics and Psychoacoustics, 635