CS 101 - Introduction to Computing, Spring 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 Lect48c.java is a good starting place for this lab. Here are some good files for the background sound:

• BabyElephantWalk60
• CantinaBand60
• Fanfare60
• ImperialMarch60
• PinkPanther30
• PinkPanther60
• StarWars60

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 the method addSoundtrack() that will take two sounds (the foreground sound and the background sound) and return a new sound.
   • play (or explore) the resulting sound and prompt the user to save it in a file

3. Contain the addSoundtrack() method that will:
   • take two sounds as paramters (the foreground sound and the background sound).
   • Create a new sound that is the length of the foreground sound. The samples in the new sound should be the result of adding the background sound to the foreground sound, but the volume of the background sound should be one-third of the sound from its original file. 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.
   • return the newly created sound.

• Sample Sound Files

Submittal of the Lab Assignment

1. Go to the blackboard site for the class
2. Select "Assignments" on the left bar
3. Locate the correct assignment to submit; click on "View/Complete Assignment" at the bottom of that assignment
4. Next to "Attach local file", click "Choose file", choose the file you want to submit; please submit only ONE file, properly named.

   For example for lab2, name it Lab2yournetid.java, for example if your Net ID is sfranz3, the filename would be Lab2sfranz3.java

   Please only submit source code file (the .java file, not the .class). Also, if you have any comment about your program, please write it down in the same file; please do NOT write in the "Comments" field on the submission page (this will go into a different file and will be easily missed).
5. Hit "Submit"
6. Go back once again to View/Complete assignment and make sure that your file was submitted; also, this page will show your grade and comments (if any) after assignments are graded.