Physics of Music Physics 121

Due Wednesday, 16 November Fall 1994

Assignment 9

Practice with SoundEdit:

  1. Call up SoundEdit from the Apple Menu. You should see a spectrum window and a controls window appear on your screen.
  2. If no controls panel shows up, go to the Windows menu and select Show Controls Panel.
  3. Select Show Selection from the Windows menu.
  4. Select Tone Generator from the Effects menu. Create a 500 Hz triangular wave at 80% amplitude which is 2 seconds long.
  5. Play the sound by clicking Play in the Controls panel
  6. Expand the wave with the slider switch on the bottom of the main window Click the diamond on the sliding scale to get the finest resolution.
  7. Select Ruler Options in the View menu. Click on milliseconds. Note the scale on top of the main window.
  8. Measure the period of the wave using this ruler. Measure peak to peak. Does the number of milliseconds you get agree with the frequency of 500 Hz?
  9. Click on the waveform to get highlighting to disappear. Swipe one period with the mouse and look at the Selection window. The icon |<-->| identifies the length of the highlighted area. Does this number agree with your answer in (8)?
  10. Select Spectrum Options from the View window. Set Display type to 3D, 3D Type to "Old in Back", 3D to "Black fill", frequency range = 0 to 5000. Then click Grid, Power, and Emphasis so there is an X in the box (this turns that feature on).
  11. Select Spectrum from the View menu. What frequencies contribute to the spectrum? Does this make sense? Select Print from the File menu. Turn this page in on the due date.
  12. Select Both from the View menu. Adjust the window with the double box on the lower right and the slide bar on the upper right. You should be able to see both waveform and spectrum nicely together.
  13. Highlight the waveform. Select Bender from the Effects menu. Lift the right-hand side of the horizontal line up to the top of the window. This will raise the pitch continuously by one octave. Play the result. What do you hear?
  14. What do you observe in the spectrum? Because SoundEdit samples over a relatively long time, you don't quite see peaks stepping from 500 to 1000 Hz, from 1500 to 3000 Hz, etc.
  15. Select Spectrum Options from the View menu. Set the Range to 32 steps. What happens? Why are the lines for each harmonic diverging?
  16. Select Save As from the File menu. Give the file the name "your-last-name.tri" and put this into the folder physics121 in the public folder.
  17. Select New from the File menu.
  18. Hit Record in the Controls window. Say something like, "Hello, my name is Allison." into the microphone. Play this. Swipe area before (after) sound you want to keep. Hit Delete to get rid of it. Play this now.
  19. Highlight the waveform. From the Effects menu select the following:
    	Backwards		play this.  What language does it sound like?
    	Undo Backwards in Edit menu
    	Echo 0.25 seconds, 50%		Describe the result.
    	Undo Echo in Edit menu.
    	Filter (all bars to the bottom except 4-6kHz to top) What do you hear? Why?
    	Undo Filter in Edit menu.
    	Reverb	Concert Hall and outer space	Describe what you hear.
    	Shift Pitch	Up one octave
    	Tempo	200%		Describe the sound.
    	Undo Tempo
    	Shift Pitch	down one octave
    	Save As "" in public/physics121
  20. Select Spectrum Options in View and change Spectrum to 16 steps. Increase gain until you see a reasonable spectrum. Print this.
  21. Try the other features of the program so you are familiar with it. Leave the files you create on the computer. I'll check for them and examine the contents.

College of William and Mary, Dept. of Physics