# Question involving beats and sound waves

1. Sep 12, 2005

### insertnamehere

Hi, I have a question involving beats and sound waves.
When two sound waves (one with a MUCH LARGER Frequency than the other) combine, what would happen? Would there still be a beat pattern? Me, I think that if there still is a beat pattern, it would have the same frequency as that of the highest frequency of one of the combining waves. Am I right, or horribly wrong? I'm really puzzled by this. Thank you very much for your time.

2. Sep 12, 2005

### Tom Mattson

Staff Emeritus
Check your book and find the formula for the beat frequency. It is not the higher of the two combining frequencies.

3. Sep 12, 2005

### Staff: Mentor

If wave #1 has a much larger frequency than wave #2, then what you get is (approximately) a wave of frequency #1 whose amplitude varies according to frequency #2. This is the principle used in AM (amplitude modulation) radio signals.

4. Sep 12, 2005

### quasar987

IMO, the answer can be seen clearly by looking at the "unmanipulated" equation of "beats", i.e. the simple addition of the two waves:

$$y(t) = Acos(\omega_1t) + Acos(\omega_2t)$$

what does the addition of these two graph looks like if $\omega_1 << \omega_2$?