| Superposition of two harmonic oscillations with close frequencies
f1 and f2 leads to the so-called beats
because these two oscillations periodically go in-phase and anti-phase.
When they are in-phase, their sum is a strong signal because of a
constructive interference.
When they are anti-phase, they cancel each other and the sound dies
out for a while.
The frequency of the beats is fb = |f1
- f2|.
Move the slider to change f2 while f1
is kept constant. Look where the two oscillations, red and blue, are in-phase and
anti-phase. |