Phys 101 lo #6

BeatsTony Mo

Student #: 14449145Phys 101

Definiton:• Beats – when two waves have similar frequencies, the volume of the

sound increases of decreases as a function of time• The amplitude of a wave indicates the volume of the sound• The frequency of a wave indicates its pitch

• Example:• Press on the buttons to play sound 330Hz 330Hz + 331Hz 330Hz+340Hz

1 beat/s 10beats/s

Carefully listen and hear the differences caused by the beats

Tones with a large difference in frequency

400 hz200hz 300hz 200hz + 400hz 300hz+400hz200hz + 300hz

*Notice that beats are no longer present

Graph of 2 waves with large difference in frequency

Equations:

Resultant wave is fixed at x=xo so that the amplitude is only in terms of time and not position as well

Amplitude Modulation

As a function of time As a function of position

Questions:

• Derek and Sloan decide to play a song together. Derek is playing the guitar while Sloan is playing the drums. If Derek plays at a frequency of 350Hz while Sloan plays at 330Hz, What is the mean angular frequency (assuming the phase constant is 0)? What is the beat frequency? How many beats is heard in 2 seconds?

Solutions:

• For part 1 we are given the frequency,• ) = 2199 rads/s

Bibliography

• Background images from google• Graph and Equations from Physics for Scientists and Engineers - 1e

Hawkes, Iqbal, Mansour, Milner-Bolotin, and Willia • Sound created with Audacity