The frequency of a wave is related to its velocity and wavelength by:
[tex]f=\frac{v}{\lambda}[/tex]In this case the velocity is 343 m/s and the wavelength is 3.93 mm, then we have:
[tex]\begin{gathered} f=\frac{343}{0.00393} \\ f=87277.35 \end{gathered}[/tex]Therefore, the frequency is 87277.35 Hz
