Sound Intensity Article Index for
Sound 		Articles about
Sound Intensity 		Website Links For
Sound 		 

Information About

Sound Intensity
APPAREL
BABY
BEAUTY
BOOKS
CAR TOYS
CELL PHONES
DVD'S
ELECTRONICS
GOURMET FOOD
GROCERIES
HEALTH & PERSONAL
HOME & GARDEN
JEWELRY
MUSIC
MUSIC INSTRUMENTS
OFFICE PRODUCTS
SOFTWARE
SPORTING GOODS
TOOLS & HARDWARE
TOYS
VIDEO GAMES
SHOPPING HOME
MORE SHOPPING...



The sound intensity, '''''I''''', (acoustic intensity) is defined as the Sound Power '''''Pac''''' per unit area ''A''. The usual context is the measurement of sound Intensity in the air at a listener's location. The SI units are W/m2 ( Watt s per Square Metre ).

:
I = rac{1}{T} \int_{0}^{T}p(t) \cdot v(t)\,dt


For a spherical sound source, the intensity as a function of distance r is:
:
I_r = rac{P_{ac}}{A} = rac{P_{ac}}{4 \pi r^2}


The sound intensity ''I'' in W/m2 of a plane progressive wave is:
:
I = p \cdot v = rac{p^2}{Z} = Z \cdot v^2 = \xi^2 \cdot \omega^2 \cdot Z = rac{a^2 \cdot Z}{\omega^2} = E \cdot c = rac{P_{ac}}{A}


where:

The amplitude of sound intensity (not sound pressure!) decreases in the free field (direct field) with 1/r2 of the distance of a point source.

Sound Intensity Level , ''LI'', is the sound intensity, expressed in logarithmic units.
:L_I=10 \log_{10} rac {I}{I_o} (dB-SIL),
where ''Io'' is the reference intensity, 10-12 W/m2