Answer
$$5.2 \times 10^{3} \mathrm{\ Hz}$$
Work Step by Step
The speed of sound is $v=343 \mathrm{m} / \mathrm{s}$ , so the frequency is
$$f=v / \lambda=v / 4 d=(343 \mathrm{m} / \mathrm{s}) / 4(0.0165 \mathrm{m})=5.2 \times 10^{3} \mathrm{\ Hz}$$
