SOUND WAVES!

A sound wave emitted by a compact source is a spherical outgoing wave, and the amplitude of the wave falls off like 1/r, so that we can write

Δp(r,t) = (a/r)sin[kr - ωt], or
Δp(r,t) = ([Δpm(r0)r0]/r)sin[kr - ωt],



Therefore the intensity I, in Watts per square meter, goes like the average source power P divided by the area subtended at a distance r from the source, 4πr2

Beats!

Standing Waves in Pipes!

Doppler Shift!

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travelling wave...

Standing Wave...