i saw the 'proof' of the wave equation for a sound wave in a medium assuming the wave equation for a dissplacement wave.(adsbygoogle = window.adsbygoogle || []).push({});

that is the equtaion [tex] s=s_{0} \sin(kx-wt)[/tex] is supposed to hold for all points for a wave propagating in the x direction.

then using this he found out the excess pressure at any point [tex]x[/tex] a any time [tex] t [/tex].

well what he did was let at time t=0 wave started and at time t say the dislpacement of any point x be s and that of [tex]x+\delta x[/tex] be [tex]s+ \delta s[/tex].then we have

change in volume [tex]\delta V=-A\delta s=-Ak \cos(kx-wt) \delta x[/tex]

hence he said excess pressure on the material at x is [tex]\delta P=\frac{-B \delta V}{V}[/tex]

but my question is the fluid at x is no more at x but rather at x+s so how come the pressure calculated from the bulk modulus equtaion is that at x

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Wave equation for sound waves

Can you offer guidance or do you also need help?

Draft saved
Draft deleted

**Physics Forums | Science Articles, Homework Help, Discussion**