Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average, or equilibrium) atmospheric pressure caused by a sound wave. Sound pressure in air can be measured using a microphone, and in water using a hydrophone. The SI unit for sound pressure p is the pascal (symbol: Pa).
Sound pressure level (SPL) or sound level is a logarithmic measure of the effective sound pressure of a sound relative to a reference value. It is measured in decibels (dB) above a standard reference level. The commonly used "zero" reference sound pressure in air or other gases is 20 µPa RMS, which is usually considered the threshold of human hearing (at 1 kHz).
Read more about Sound Pressure: Instantaneous Sound Pressure, Sound Pressure Level
Famous quotes containing the words sound and/or pressure:
“This teaching is not practical in the sense in which the New Testament is. It is not always sound sense in practice. The Brahman never proposes courageously to assault evil, but patiently to starve it out. His active faculties are paralyzed by the idea of caste, of impassable limits of destiny and the tyranny of time.”
—Henry David Thoreau (1817–1862)
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—David Elkind (20th century)