Alice-Media Computation
Change Sound Frequency Project
Barbara Ericson, ericson@cc.gatech.edu
Georgia Tech
July 2006
Project Summary:
Create three objects of the same class and resize one to be bigger and one to be smaller.
Use media computation to modify a sound to make a higher sound (double the frequency)
and a lower sound (half the frequency). Associate the higher sound with the smaller
object, the lower sound with the bigger object and the original sound with the mediumsized object.
Topics Covered:
The Alice topics covered include creating an object and using the mouse controls to copy
objects, resize objects, and position objects. In media computation we cover using a Java
for loop and writing methods.
Alice Part:
Use Alice to create a world using the water template. Add an island from the
Environments category. Create a frog from the Animals category. You will have to
move it up to see it on the island. Copy the frog 2 times so that you have 3 frogs. Point
out that they have different names (and you can rename them if you wish). Use the resize
feature to make one big, one medium, and one little frog in a row. Use media
computation to take the croak.wav sound in the mediasources directory and make a
version that is higher and a version that is lower (see instructions below). Then import all
3 sounds by clicking on File and then on Import and pick the sound to import. Next, have
each frog play the appropriate sound and then tap its foot using the play sound method
and the foottap method at the same time (using Do together). Then play the movie.
Media Computation Part:
To make a higher sound make a copy of the original sound and then copy every other
value from the copied sound to the original and clear the rest of the original sound to 0.
Or you can create a new sound half as long as the original and copy every other value
from the original to the new sound. You can return the new sound.
To make a lower sound you can make a copy of the original sound and then copy each
value in the copied sound twice back to the original sound until the end of the original
sound. Or, create a new sound that is twice as long as the original and then copy from the
original to the new sound and return the new sound.
You can create a new sound with a specified number of sample values using the
constructor that takes an integer. You can write out the new or modified sound using the
write method of Sound. See the JavaDoc on Sound for more information.
Additional Materials:
There are powerpoint slides on how to change the frequency of a sound in the file SoundChangeFreq.ppt. I have original croak sound, the higher and lower croak sounds, and an
example Alice world in the zip file as well. You will need the classes Sound and
SimpleSound, and the javazoom directory in the bookClasses directory. You can get the
bookClasses zip from http://coweb.cc.gatech.edu/mediaComp-plan/101.
Other Ideas:
Have the students create 5 objects of different sizes and 4 variations on an original sound.
Have students create a more general scaleUp method and a more general scaleDown
method.