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. In air, sound pressure can be measured using a microphone, and in water with a hydrophone. The SI unit of sound pressure is the pascal (Pa).<ref name=“engineering toolbox">"Sound Pressure is the force of sound on a surface area perpendicular to the direction of the sound". Retrieved 22 April 2015. </ref>

Mathematical definition

A sound wave in a transmission medium causes a deviation (sound pressure, a dynamic pressure) in the local ambient pressure, a static pressure.
Sound pressure, denoted p, is defined by

where

Sound measurements

Sound intensity

In a sound wave, the complementary variable to sound pressure is the particle velocity. Together they determine the sound intensity of the wave.
Sound intensity, denoted I and measured in W·m⁻² in SI units, is defined by

where