Distance Law of 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.
When measuring the sound created by an object, it is important to measure the distance from the object as well, since the sound pressure decreases with distance from a point source with a 1/r relationship.
The distance law of sound pressure p for a spherical sound wave at a distance r from a punctual sound source states that the sound pressure is inversely proportional to the distance.
(The sound pressure may vary in direction from the source, as well, so measurements at different angles may be necessary, depending on the situation.)
|p2||Sound Pressure at another position r2 (Pa)|
|p1||Initial Sound Pressure at position r1 (Pa)|
|r1||Initial distance (m)|
|r2||Final distance (m)|