The Sound intensity reference article from the English Wikipedia on 24-Apr-2004 (provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

Sound intensity

The sound intensity is defined as the sound power per unit area. The usual context is the measurement of sound intensity in the air at a listener's location. The basic units are watts/m².

For a spherical sound source, the intensity as a function of distance r is:

P_ac is the acoustic power.

The sound intensity J in W/m² is:

Sound pressure p in N/m² = Pa
Sound velocity (particle velocity) v in m/s
Acoustic impedance Z in N·s/m³

Sound intensity level is a different measure used in acoustics. Unlike sound intensity, sound intensity level is logarithmic.

Notice: Do not misuse the word "intensity", if you do not mean watts per area.
Use "magnitude" "strength", "amplitude", or "level" instead.

External links

• Conversion: sound intensity to sound intensity level
  
• Ohm's law of the acoustics - calculations

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