1. Sound Waves - Beats Wei-En Hsu Center for Advanced Computation and Telecommunications UMass Lowell

2. Beats What are beats? How are beats generated? –When sound waves are combined, the variation in amplitude is heard as an alternative soft and loud pulsation in the sound.

3. Constructive and Destructive Interference A simple example: –When two sound waves are generated at slightly different frequencies, their amplitudes interfere with each other causing constructive and destructive interference. (Assume the speeds of waves are the same.)

4. Beat Characteristics Basic calculation: –Beat frequency = |f 2 - f 1 | –Beat pitch = ½(f 2 +f 1 ) Destructive Constructive

5. Experiment: Generation of Beats Ex. Two signals are at 1600Hz and 1603Hz. Calculate the beat frequency and pitch. Soln: Beat frequency: |1603 - 1600| = 3Hz Pitch: ½(1600+1603) = 1601.5Hz