Crash course in beats of physics.

1. A crash course in
Beats
Picture from textbook P. 253

2. What is a beat?
• When we hear 2 sound waves with different frequencies,
we hear beats
• This is due to the changing wave amplitude because of
destructive and constructive interference
Picture from textbook P. 249

3. Equations
Picture from textbook P. 251

4. Tuning a Piano
• Tuning a piano actually uses physics!
• Piano tuners compare the sound of a piano key with the
sound of a tuning fork
• If they don’t have the same frequency, the piano wire
has to be adjusted until the beating sounds stop
Picture from computer clip art

5. Question
• At a concert, one guitar has a tone of 397 Hz and another
has a tone of 425 Hz
• What beat frequency does a fan hear?
Picture from textbook P. 238

6. Answer
The beat frequency heard is:
425 Hz – 397 Hz = 28 Hz
Pictures from computer clip art

7. Answer
The beat frequency heard is:
425 Hz – 397 Hz = 28 Hz
Pictures from computer clip art