HomeMy WebLinkAboutDecibel Calculations (2) Estimating Sound Levels With the Inverse
Square La`v
In the real world, the inverse square law is always an idealization because it assumes exactly
equal sound propagation in all directions. If there are reflective surfaces in the sound field,
then reflected sounds will add to the directed sound and you will get more sound at a field
location than the inverse square law predicts. If there are barriers between the source and the
point of measurement,you may get less than the inverse square law predicts.Nevertheless,
the inverse square law is the logical first estimate of the sound you would get at a distant
point in a reasonably open area.
If you measure a sound level I1 95 dB
at distance
d1 =0 m= 6.561679 ft
I � '
1 then at distance
11 d2 d2= 365.76 m= 12U0 ft
the inverse square law predicts a sound level
12 = 49.75667! dB
I I ,
d, ----- -
http://hyperphysics.phy-astr.gsu.edu/hbase/acoustic/isprob2.html