Answer
Please see the work below.
Work Step by Step
We know that
$v=\sqrt{\frac{\gamma P}{\rho}}$
We plug in the known values to obtain:
$v=\sqrt{\frac{(1.61)(620000)}{4.5}}$
$v=471\frac{m}{s}$
Now we can find the frequency as
$f=\frac{v}{\lambda}$
We plug in the known values to obtain:
$f=\frac{471}{0.50}=940Hz$
