A crash course in

Beats

Picture from textbook P. 253

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

Equations

Picture from textbook P. 251

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

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

Answer

The beat frequency heard is:

425 Hz – 397 Hz = 28 Hz

Pictures from computer clip art