CS-171

Program Assignment 5

An Audio Collage

Objective

The objectives of this assignment include the following:

• Understanding the linear frame sequences of digital audio filescoordinate systems involved in picture to picture translations
• Effectively using loop structures (in particular, while loops) to control transformations in limited ranges of frames
• To both understand and to translate into Java programming code many common transformations performed on audio files
• To use all of the above to create a clever and/or interesting audio file.

Overview

• You may elect to work on this assignment with a partner.  The two of you will submit one assignment with both of your names on it and you will each receive the same grade.  You must receive an ok from the instructor regarding your partnership. It is also critical that each of you participate equally; the next midterm will ask you to program methods similar to these. 
   

• An award (+5 bonus points) will be given to the best audio collage created by a student(s).  We will post all the collages online and then have a vote.  Be creative, think about your project and have some fun with this assignment.
   

• You will place all of your code as methods in your copy of  Sound.java.  You will need to submit this file in a folder named prog5 in your Assignment Inbox folder.  You will also submit your final wav file and your Java application used to construct your wav file in this same folder.  These should be the only three files you submit. 
   

• You may use any of the wav file in our MediaSources folder.  You are also encouraged to search the internet for other wav files (or audio files).  Be warned that not all wav files found on the Internet are of the correct format to work well with our default Sound constructor.  Our sound files are all at a sampling rate of 22050, contain one channel (i.e. are mono), and use 16 bits (2 bytes) per sound sample.  You will need to "clean" your externally obtained wav files first to convert them into this standard convention by using software that is installed on the instructor machine.
   

• All transformation loops should use the while-loop construct instead of the for-loop.
   

• Try to keep your final wav file around 30 seconds or less.
   

• Remember to document (comment) your code appropriately.

Requirements

All methods described below should keep the original sound intact and return new sounds with the desired effects.

Basic Transformations

• (10pts) cut
  
  public Sound cut (int start, int end )
  
  This method will cut out (or extract) a portion of the calling sound object and return this portion as a new sound object of the appropriate length.  Both start and end are sample numbers.
   

• (10pts) splice

  public Sound splice ( Sound endSound )

  This method will create a new sound of the appropriate length that contains first the calling sound and then the endSound appended to the end.
   

• (10 pts) add

  public Sound add ( int start, Sound overlaySound )

  This method will create a new sound of the appropriate length.  It contains all parts of both sounds.  The calling sound is copied to the new sound.  Then starting at the sample indicated by start the overlaySound will also be played (both at the same time).  If the overlay sound extends beyond the length of the calling sound, then be sure your combined sound is long enough.
   

• (10 pts) reverse

  public Sound reverse ( )

  This method will create a new sound the same length as the calling sound.  It will reverse the calling sound (backwards). 
   

• (10 pts) scaleAmplitude
  
  scaleAmplitude (double factor)
  
  This method will return a new sound that is the same as the calling sound except that the volume(amplitude) has been multiplied by the specified factor.

• (10 pts) scaleFrequency
  
  scaleFrequency (double factor)
  
  This method creates a new sound that is a copy of the old sound except that the length is changed by the indicated factor (shortened for factor < 0 and lengthened for factor > 0).  The new sound should be the same as the old one except compressed or expanded by the indicated factor. 

Other Transformations

• (10pts) taperStart
  
  public Sound taperStart ( int num )
  
  This method returns a new sound that is the same as the calling sound except that the first num samples taper from zero volume to regular volume at a constant rate.
   

• (10pts) taperEnd
  
  public Sound taperEnd ( int num )
  
  This method returns a new sound that is the same as the calling sound except that the last num samples taper off to zero volume at a constant rate.
   

• (15pts) stutter
  
  public Sound stutter ( int start, int end, int numRepeats )
  
  This method creates a new sound that is the same as the calling sound except that the portion of the calling sound between start and end (inclusive) is now repeated numRepeats times.
   

• (10 to 15 pts) echo
  
  public Sound echo ( int start, int end, int numRepeats )
  
  This method will create a new sound that has an echo effect of the contents of the calling sound.  The numRepeats indicates how many times the echo is heard.  For additional credit, add a decayFactor which indicates how much more quiet each subsequent echo is -- this should be a number such as 0.8 which decays the volume of the ith echo by a factor of 0.8 raised to the ith power.  (10 points regular, 15 points with decay).
   

• Others??
  
  Be creative and think of other effects.  Any that are substantively different than those defined here could be used.  Get the instructor's approval ahead of time, so we can arrive at a commensurate point value for the effort.