The graph below shows how the intensity $I$ of a stationary sound wave in air changes with distance $x$. The speed of sound in air is $340\,\text{m s}^{-1}$. Find the frequency of the sound wave.
- A$1700\,\text{Hz}$
- B$2270\,\text{Hz}$
- C$3400\,\text{Hz}$
- D$6800\,\text{Hz}$