#### Answer

We can see a sketch of the graph of this function over the interval $[0.15, 1.15]$
We can see that there are 4 beats in one second.

#### Work Step by Step

Consider the frequencies $220~Hz$ and $216~Hz$
$P_1 = 0.005~sin~440~\pi~t$
$P_2 = 0.005~sin~432~\pi~t$
$P= P_1+P_2 = 0.005~sin~440~\pi~t+ 0.005~sin~432~\pi~t$
We can see a sketch of the graph of this function over the interval $[0.15, 1.15]$
We can see that there are 4 beats in one second.