I recorded the following two sound files of me plucking a guitar string once at the center of the string and the other near the bridge of the guitar. Listen to them--you should be able to tell which is which just from the tones.

Sound 1

Sound 2

First we will examine the time waveforms of the two tones:

 

1. What is the period of the repeated pattern in each case?
2. What is the frequency of the fundamental in each case?
3. To what note(s) do these fundamental frequencies correspond?

Now let's examine the spectra of the waveforms.

 

1. From the graphs find the frequencies of the fundamentals. Do they agree with what you calculated from the time-domain waveforms?
2. Which spectrum is richer in high harmonics? Does this jive with your intuition?

Note that for the center plucked string the odd harmonics (1,3,5) are prominent whereas the even harmonics (2,4) are weak. We'll understand why this is so when we examine the subject of standing waves on a string.

You've now completed all the on-line material on Fourier transforms and spectral analysis. The next module is a short couple of pages on calculating the reverb time of rooms and auditoria (auditoriums??). After you finish that material there is an on-line quiz.