- #1

- 128

- 2

**beats frequency**heard from the interference of two sound waves with frequencies ##f_1## and ##f_2## is $$\nu=|f_1-f_2|$$

Nevertheless

**the frequency of the resulting wave**is not ##\nu## but the mean value of the two frequencies

$$f_{resulting}=\frac{f_1+f_2}{2}$$

As far as I understood ##\nu## is the frequency at which the maxima of intensity are heard, while ##f_{resulting}## is indeed the frequency of the resulting wave.

In particular I can notice that ##f_{resulting} > \nu## always.

The distincion between the two is clear in theory, but in practice I still have doubts.

Suppose to have an instrument that can measure sound waves iff the frequency is, say, bigger than ##f_{min}## and lower than ##f_{max}##.

Now suppose that two waves interefere in a way such that ##f_{resulting} > f_{min}## but ##\nu <f_{min}##, or, in a way such that ##\nu < f_{max}## but ##f_{resulting} > f_{max}##.

What does the instrument measure in these cases?

Which of the two frequencies "determine" the upper of lower limits for the frequency that can be measured by such instrument?