Sound Pressure

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:

    I thought when I was a young man that I would conquer the world with truth. I thought I would lead an army greater than Alexander ever dreamed of. Not to conquer nations, but to liberate mankind. With truth. With the golden sound of the Word. But only a few of them heard. Only a few of you understood. The rest of you put on black and sat in chapel.
    Philip Dunne (1908–1992)

    Amid the pressure of great events, a general principle gives no help.
    Georg Wilhelm Friedrich Hegel (1770–1831)