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:

    Comrades, leave me here a little, while as yet ‘tis early morn:
    Leave me here, and when you want me, sound upon the bugle-horn.
    Alfred Tennyson (1809–1892)

    This is a catastrophic universe, always; and subject to sudden reversals, upheavals, changes, cataclysms, with joy never anything but the song of substance under pressure forced into new forms and shapes.
    Doris Lessing (b. 1919)