PASCO Xplorer GLX, User Manual

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X p l o r e r G L X U s e r s ’ G u i d e 135
A c t i v i ty 9 : C o n s t r u c ti v e a n d D e s t r u c t i v e
I n t e r f e r e n c e
Background
When two sound waves with identical frequencies and amplitudes combine, they
may interfere constructively or destructively. When constructive interference
occurs, the resulting tone is louder than either of the individual tones. When
interference is destructive, the combined tone is less loud than the individual
tones. For two waves of equal frequency, the type of interference depends on the
phase relationship between the waves.
In this activity, you will use the GLX to generate two tones at 440 Hz while vary-
ing the phase of one.
Before You Begin
Start a new experiment on the GLX.
1. Press to go to the Home Screen.
2. Use the arrow keys to highlight the Data Files icon and press to open
the Data Files screen.
3. Press to open the Files menu and press to select New File.
4. When the GLX asks if you would like to save the previous file, press
to save or not to save.
Procedure
1. Press to return to the Home Screen.
2. Use the arrow keys to highlight the Output icon and press .
3. If the Speaker Configuration is not already set to Mono, use the arrow keys
to highlight Speaker Configuration and press
to set it to Mono.
4. Use the arrow keys to highlight the Phase of the Right Output Channel (as
pictured to the right).
5. Press to turn on the Right Output Channel.
6. Press and to vary the phase of the Right Output wave. As you vary
the phase of the wave between -360° and +360°, how does the sound
change?
7. Set the phase of the Right Output wave back to 0°.
F4 1
pqrs
F1
F2
F3
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