Beats
10.2.1 Explain the formation of beats
Beats are generated when two sounds have similar frequency. The effect is that the sound’s amplitude or volume oscillates or beats. The beat phenomenon is caused by constructive and destructive interference. The picture below shows the beat generated by two tuning forks with very close frequencies.
The graph above is amplitude (sound pressure) vs. time. The period of the beat is defined as the time from one peak to the next, or the time between amplitude (volume) maximums.
10.2.2 Derive the beat frequency formula
The simplest way to “derive” the beat frequency formula is by simple observation. By observation it can be found that the beat frequency is:
(1)\begin{equation} f_b = |f_1 - f_2| \end{equation}
This is the formula given in the IB formula handbook.
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