Sound travels in air at a speed of $v = 340$ m/s and has a wavelength of $\lambda = 0.68$ m. Find the period of oscillation.
The link between speed, wavelength and period: $v = \lambda/T$, hence
$$T = \frac{\lambda}{v} = \frac{0.68}{340} = 0.002 \text{ s} = 2 \text{ ms}$$
$T = 0.002$ s (2 ms)