Human hearing detects pressure changes of a few parts per billion

Evidence

Humans respond to sounds ranging over a sound pressure range of about 1 million to 1. When interpreted as sound intensity (energy flow per unit area) it is an even more impressive 1 trillion to 1. This enormous range extends from sounds that are just audible at middle frequencies to those that generate discomfort or pain at the higher limit. Because such large numbers are impractical to work with, a logarithmic scale of sound pressure level is used to describe measured and audible acoustic events. The units are decibels (dB). — Toole, Floyd E, Sound reproduction- the acoustics and…, 886 (#expands, via linked claim)

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 (#corroborates, via linked claim)

Categorization

• XREF: connects to: Hearing spans a pressure range greater than a million to one — Toole, Floyd E, Sound reproduction- the acoustics and…, 886; Human hearing operates near the theoretical physical limits imposed by thermal noise — David Howard, Jamie Angus, coustics and Psychoacoustics, 635; Human hearing’s 120-dB dynamic range exceeds man-made device capabilities

Broader Connections

• Hearing spans a pressure range greater than a million to one #expands (0.90) — Toole, Floyd E, Sound reproduction- the acoustics and…, 886
• Human hearing operates near the theoretical physical limits imposed by thermal noise #corroborates (0.85) — David Howard, Jamie Angus, coustics and Psychoacoustics, 635
• Human hearing’s 120-dB dynamic range exceeds man-made device capabilities #expands (0.80)