CS 101 - Introduction to Computing, Fall 2010

Lab 12

This lab will have you combine two sound files to add a "background" soundtrack to a foreground sound. The following files of the Gettysburg Address and the Preamble of the U.S. Constitution are great foreground sound files.

• Gettysburg Address
• The Preamble
• Gettysburg Address 10 seconds
• The Preamble 10 seconds

The background file should be repeated it if is not as long as the foreground file. We will also want to make the background sound quieter than it originally is, so we wish to make its volume a third of its original value. The example program of Lect1111c.java is a good starting place for this lab. Here are some good files for the background sound:

• BabyElephantWalk60
• CantinaBand3 A 3 second version
• CantinaBand60
• Fanfare60
• ImperialMarch60
• PinkPanther30
• PinkPanther60
• StarWars60
• StarWars3 A 3 second sound

To combine two sound files, you simply just add the sample values together. The only problem occurs if the resulting value goes above 32,767 or below -32,768. A simple solution is to use an if statement to check for this. Two simple if statements can check for this and correct the problem if it occurs. To correct this, just set the value to either 32,767 if the value was greater than 32,767 or set the value to -32768. if the value was less than -32,768.

Lab Assignment 12

Create a Java program that will:

1. Contain a comment indicating
   • your Name,
   • Net-ID,
   • Course Name,
   • Assignment Name and
   • a short description of the assignment

2. Contain the main() method that will
   • Prompt the user for the "Foreground" sound file and make a sound object from this file.
   • Prompt the user for the "Background" sound file and make a sound object from this file.
   • Call a method combineSounds()
   • play (or explore) the resulting sound and prompt the user to save it in a file

3. Contain the method combineSounds() that will
   • Take two sound objects as parameters: the foreground sound and the background sound.
   • Add the background sound to the foreground sound, but the volume of the background sound should be one-third of its original volume. To do this, first divide the background sound sample values by 3 before adding the two values together.
   • check for and correct any "clipping" that may result from the resulting value being greater than 32,767 or less than -32,768.
   • Note: if the background sound file is shorter than the foreground sound file, repeat the background sound as often as needed to give a background sound to the entire foreground sound. Use the 3 second version of the Star Wars Theme in StarWars3 or the 3 second version of CantinaBand3 to test this out.

4. You are also to submit the Java file electronically via the assignment link for Lab 12 in BLackboard.

• Sample Sound Files