# Math Help - Sound propagating

1. ## Sound propagating

Sound propagating through air at 30oC passes through a vertical cold front into air that is 4.0oC. If the sound has a frequency of 2400 Hz, by what percentage does its wavelength change in crossing the boundary?

2. Originally Posted by babygirl
Sound propagating through air at 30oC passes through a vertical cold front into air that is 4.0oC. If the sound has a frequency of 2400 Hz, by what percentage does its wavelength change in crossing the boundary?
The speed of sound changes from 349.4 m/s to 333.8 m/s. The frequencies
on both sides of the front are equal, so as:

$
\lambda=c/f
$

the wavelengths are:

$
\lambda_1=349.4/2400=0.146,\ \ \lambda_2=333.8/2400=0.139 \mbox{ m}
$

So the percentage change in wavelength is:

$\frac{\lambda_2-\lambda_1}{\lambda_1}\times 100\approx 4.8 \%$

RonL