1. Beats
September 9, 2005

2. Recall what a single frequency tone sounds like
Play on Sound Generator A=440 Hz.
The Graph:

3. 440 Hz. and 450 Hz. Compared
440 Hz.
450 Hz.

4. 440 Hz. and 450 Hz. Together

5. 440 Hz. and 450 Hz. Together for a longer time (0.1 second)

6. 440 Hz. and 450 Hz. Together for an even longer time (0.5 second)
Tbeat
These
are
BEATS
From this graph we see that Tbeat = 0.1 seconds. fbeat = 10 Hz..

7. Why??
In phase out of phase in phase
again

8. The Concept Two sounds start together (in phase).
After Tbeat seconds they get back together again.
One of the waves must have gone through N cycles while the other went through (N+1) complete cycles.
They are therefore together again!

9. The math !
The beat frequency between two simultaneous tones is equal to
The difference between the frequencies of the two tones!

10. LISTEN & Look…….
Isn’t science wonderful??