Question

What is the period of a 220 hz sound wave?

Answer 1

T=1/f 
T being period. f being frequency. 
1/220=0.0045 ms 
1/6.5=0.1538 mHz 
(example)
hope it helps

Answer 2

We have to calculate the period when we know the frequency of a sound wave. Period and frequency are related quantities. They are reciprocal of each other.
T = 1/f, where T is the period ( in seconds ) and f is the frequency ( in Hz ).
T = 1/220 Hz;
Answer: T = 0.0045 s.