CPSC1301 Computer Science 1

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CPSC1301Computer Science 1

• Chapter 10
• Making Sounds by Combining Piecespart 1

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Learning Goals

• Processing ranges of Sound values
• Blending pictures
• Changing the sound frequency
• Computing concepts
• Method overloading
• Changing a for loop to increment by a value other
  than 1
• Modifying a method to be more general

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Blend Sounds

• Like blending pictures we can blend two sounds
• Copy the first 20,000 values of sound1
• Copy from both by adding .5 sound1 value and .5
  sound2 value
• Copy the next 20,000 values of sound 2

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Blend Sounds Method

• public static void blendSounds(Sound target)
• Sound sound1
• new Sound(FileChooser.getMediaPath("aah.wav
  "))
• Sound sound2
• new Sound(FileChooser.getMediaPath("bassoon
  -c4.wav"))
• int value 0
• // copy the first 20,000 samples from sound1
  into target
• for (int index0 index lt 20000 index)
• target.setSampleValueAt(index,
• sound1.getSampleValueA
  t(index))

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Blend Sounds - Continued

• // copy the next 20,000 samples from sound1
  and blend that
• // with the first 20,000 samples from sound2
• for (int index 0 index lt 20000 index)
• value (int) ((sound1.getSampleValueAt(inde
  x 20000)
• 0.5)
• (sound2.getSampleValueAt(inde
  x) 0.5))
• target.setSampleValueAt(index
  20000,value)
• // copy the next 20,000 samples from sound2
  into the target
• for (int index20000 index lt 40000 index)
• target.setSampleValueAt(index 20000,
• sound2.getSampleValu
  eAt(index))

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Testing Blend Sounds

• public class SpliceSounds
• public static void main (String args)
• String fileName FileChooser.pickAFile()
  Sound target new Sound(fileName)
• blendSounds(target)
• target.play()
• target.explore()

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Modify Blend Sounds Exercise

• Create another blendSounds method
• That takes the file name of the sounds to blend
• And a value to start the blend at and another to
  stop the blend at
• Modify the original blendSounds method to call
  this one

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Overloading Methods

• You can have several methods with the same name
• As long as the parameter list is different
• In number of parameters
• And/or types of parameters
• blendSounds()
• blendSound(String name1, String name2, int
  startBlend, int endBlend)

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Changing the Sound Frequency

• The frequency of a wave is the number of cycles
  per second (cps), or Hertz (Hz)
• (Complex sounds have more than one frequency in
  them.)
• Our perception of pitch is related
  (logarithmically) to changes in frequency
• Higher frequencies are perceived as higher
  pitches
• We can hear between 5 Hz and 20,000 Hz (20 kHz)
• A above middle C is 440 Hz

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Double the Frequency

• If we take every other sample we double the
  frequency of the sound
• Completes two cycles instead of one in the same
  time
• It will sound higher

100 200 300 400 500
100 300 500 0 0
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Double Frequency Method

• public static void doubleFreq(Sound target)
• // make a copy of the original sound
• Sound s new Sound(target.getFileName())
• / loop and increment target index
• by one but source index by 2,
• and set target value
• to the copy of the original sound
• /

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Double Frequency - Continued

• for (int sourceIndex0, targetIndex 0
• sourceIndex lt target.getLength()
• sourceIndexsourceIndex2,
  targetIndex)
• target.setSampleValueAt(targetIndex,
• s.getSampleValueAt(sou
  rceIndex))
• // clear out the rest of this sound to
  silence (0)
• for (int i target.getLength() / 2
• i lt target.getLength()
• i)
• target.setSampleValueAt(i,0)

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Test Double Frequency

• public class SpliceSounds
• public static void main (String args)
• String fileName FileChooser.pickAFile()
• Sound target new Sound(fileName)
• doubleFrequency(target)
• target.play()
• target.explore()

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Challenge

• Create a method that will take every third sample
  
• Will this sound higher or lower?
• Can you make this method more general?
• By passing in the amount to add to the source
  index each time?

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Halving the Frequency

• We can copy each source value twice to half the
  frequency
• Only get through half a cycle in the same time we
  used to get through a full cycle
• It will sound lower
• This is the same algorithm that we used to scale
  up a picture

100 200 300 400 500
100 100 200 200 300
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Halve Frequency Method

• public void halveFreq(Sound target)
• // make a copy of the original sound
• Sound s new Sound(target.getFileName())
• / loop through the sound and increment
  target index
• by one but source index by 0.5 and set
  target value
• to the copy of the original sound
• /
• for (double sourceIndex0, targetIndex 0
• targetIndex lt target.getLength()
• sourceIndexsourceIndex0.5,
  targetIndex)
• target.setSampleValueAt((int) targetIndex,
• s.getSampleValueAt((int)
  sourceIndex))

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Testing Halve Frequency

• public class SpliceSounds
• public static void main (String args)
• String fileName FileChooser.pickAFile()
• Sound target new Sound(fileName)
• halveFreq (target)
• target.play()
• target.explore()

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Change Frequency Exercise

• Write a method that will copy each sound value 4
  times to the target
• Will the new sound be higher or lower?
• Can you make this more general?
• By passing in the number of times to copy the
  source value
• Try it with 3 times and check the index values to
  make sure that you are doing it right

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Summary

• You can have more than one method with the same
  name method overloading
• As long as the parameter list is different
• Different number of parameters
• Different types of parameters
• You can increment or decrement loop variables by
  numbers other than 1
• You can make methods more general
• By passing in parameters
• Some algorithms are the same for pictures and
  sounds
• Scaling a picture down and doubling the frequency
  of a sound