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:
“Strike on your drummes, spread out your ancyents!
Sound out your trumpetts, sound out amaine!”
—Unknown. Sir Andrew Barton. . .
English and Scottish Ballads (The Poetry Bookshelf)
“Adolescence is when girls experience social pressure to put aside their authentic selves and to display only a small portion of their gifts.”
—Mary Pipher (20th century)