Loud, soft, high and low waves

Four sounds have different amplitudes and frequencies. You will make the program find the time period of each, the number of waves each shows in $20\ \text{ms}$, and which sound is both loud and high. Then it draws the four waves.

The idea. The time period is $T = \dfrac{1}{f}$; the number of waves in a time $t$ is $f \times t$. A big amplitude means loud; a big frequency means high.

Your tasks.

1. Inside the loop, work out T_ms, the time period of each sound, in milliseconds.
2. Inside the loop, work out n, the number of waves in $20\ \text{ms}$ ($0.02\ \text{s}$).
3. Set loud_high to the number of the sound (0 to 3) that has amplitude above $0.5$ and frequency above $500\ \text{Hz}$.