Physics 121: Physics of Music

Assignment 4
• Read 10.1, 12.1 and Chapter 7 in Hall.
• 1. Hall, page 195, Exercise 2.
• 2. Hall, page 195, Exercise 3.
• 3. Hall, page 252, Exercise 4.
• 4. Hall, page 252, Exercise 5.
• 5. Hall, page 252, Exercise 7.
• 6. For this exercise you may use the Macintosh computers in Small 101, or use those in the Music Library in Ewell Hall. Choose one with speakers on the monitor (you may play this softly out loud or ask the assistant for a set of earphones). Presently the lab is open from 8-5:30. Later on it will be open during the evenings too.
  • a) Pull down the Apple menu (upper left-hand corner) and select Practica Musica. If it's not there, look in aliases on the desktop. The assistant can help you get started.
  • b) Choose any of the four names listed
  • c) Pull down Pitch Reading from the Activities menu.
  • d) Select Level 1 from the Interval Spelling menu. (There is help in this menu if you need instructions about the various intervals.)
  • e) If you need it, you can select Staff Keyboard from the Options menu.
  • f) Once you can do without the staff Keyboard, turn it off by selecting Plain Keyboard from the Options menu.
  • g) Complete Levels 1 and 2.
  • h) Report which levels you have completed. (The bookkeeping feature of the program is not working right now.)
  • i) Extra Credit: Complete Levels 3 and 4.
• 7. Find a telephone with a reasonably long cord. (If you have personally transcended this technology, search for an old-fashioned one---maybe you'll meet someone interesting in the process.) Stretch out the cord a bit by moving the receiver away from the phone. Now move the receiver in your hand back and forth to make transverse waves propagate down the line. Change the rate of your back-and-forth motions until you produce a standing wave. Experiment until you produce standing waves with one, two, three (and possibly 4) antinodes. Now that you have a feeling for this, you can be more quantitative. What happens to the frequency of a particular mode if you stretch the phone cord? Pick a fixed length of the cord and measure the frequencies for the one, two, and three antinode resonances. How are these frequencies related to each other? Is this what you expect? Hint: as with the pendulum, it's easiest to measure the time required to complete 10 periods. Once you know the period you know the frequency. Estimate your errors. Have fun.