CS 101 - Introduction to Computing, Fall 2011

Lab 13

In this lab, you will take a single sound file and have it fade in (increase) from silence to full volume and then fade out (decrease) into silence again. Program 71 from the book will be a very helpful method to use in this lab! You can find sample soundtrack files to use for this lab here.

Think about what happens when you are increasing the volume of a sound. Say I have a sound that I divide into 10 sections. Each sections is 1/10th of entire sound. At the end of the sound I want to have full volume, yet at the beginning I want to have silence. I can do this by first finding the number of SoundSamples in each of the 10 sections (i.e. total number of samples divided by 10). That means that I can break my sound into 10 sections, where on each section I increase my volume by an additional 10%. By the time I have reached the end of the song, I will have been at full volume.

I will do the same for when I decrease a sound, only this time it is the reverse.

You may have to use doubles when you step up to the next interval. Because you will increase each sample by a percentage, you will have to use a double. However, you may recast this value to an int when you set the SampleValue in the new sound file.

The result will be a file that increases in "steps", but for the purposes of this exercise this is OK. Hopefully you will not notice it!

This lab will require four methods. The first method will break the sound into a smaller sub-piece of the original sound. The second take in the first half of the sound and increase the volume from silence to 100%. The third method will take in the second half of the sound and decrease the volume from 100% to silence. Finally, a fourth method will put these two parts back together again.

• Method 1: cropSound()
  
  • this method will be given a sound and two integer values as its parameters.
  • check to make sure the first integer parameter is less than or equal to the second integer parameter
  • check to make sure the first integer parameter is >= zero.
  • check to make sure the second integer parameter is <= the length of the given sound
  • create a new sound that is make up of the sound values starting from the index of the first integer parameter and ending just before the index of the second integer parameter
  • return the newly created sound.

• Method 2: increase():
  
  • this method will be given in the first half of the sound as a parameter
    
  • divide the sound into 10 equal length sections
    
  • set the first section to 1/10th of its volume
    
  • set the second section to 2/10ths of its volume
    
  • continue until the ninth section is set to 9/10ths of its volume
    
  • the tenth section is set to 10/10ths of its volume (i.e. left unmodified)
    
  • and return the modified sound.
    

• Method 3: decrease():
  
  • this method will be given in the second half of the sound as a parameter
    
  • divide the sound into 10 equal length sections
    
  • set the first section to 10/10th of its volume (i.e. left unmodified)
    
  • set the second section to 9/10ths of its volume
    
  • continue until the ninth section is set to 2/10ths of its volume
    
  • the tenth section is set to 1/10th of its volume
    
  • and return the modified sound.
    

• Method 4: joinSounds():
  
  • this method will take two sounds as its parameters
  • create a new sound whose length is equal to the length of the two sounds added together
  • join the two sounds so that the first sound is in the beginning of the new sounds and the second sound is at the end of the new sound.
  • return the joined sound

My final result should be the same sound I asked for in the beginning, only now it will fade in from silence to full volume and then back down again.

You should also have code to save the sound on the hard drive.

Lab Assignment 13

Create a Java program that will:

1. Be writen using good programming style which includes:
   • Good variable names
   • In-line commenting
   • Proper indentation of program statements
   • Use of blank lines to separate blocks of code.
   • Header block commenting for the program and each method written
     

     Your header block comment for the program must include the following:

     • Your Name,
     • Net-ID,
     • Course Name,
     • Assignment Name and
     • Day and time of your CS 101 lab section (i.e. Wednesday at 9:00)
     • A short description of the assignment.

     Header block comments for each method must include the following:

     • A description of the purpose of the method
     • A listing of the name, type and purpose of every parameter
     • A description of the return value and its type

2. Contain the main() method that will
   • Prompt the user for a soundtrack file
   • Create a sound object from the file
   • Split this sound into two parts of equal length using the cropSound() method twice (once for each part)
   • Send the first part to the increase() method, and return
   • Send the second part to the decrease() method, and return
   • Send these two parts to the joinSounds() method, and return
   • Play (or explore) the sound.
   • Prompt the user for a name and save it.

3. You are also to submit the Java file electronically via the assignment link for Lab 13 in BLackboard.

Here are some example sound files you can use with this assignment.

• Sample Sound Files