Question

Why should the difference between the frequencies be less than 10, to produce beats?

Answer 1

Answer:

So if the relative frequency of two sounds ie (f1~f2 ) is more than 10Hz then the time period between the beats would be more than 0.1 seconds .

We as humans can't have the ability to differentiate two sounds or beats whose time intervel is less than 0.1 seconds so we won't be able to hear them but we will hear the resultent of those beats as a single beat.