Sounds in Jython

1
Sounds in Jython

• 16 bit samples -32,768 and 32,767
• Sound object holds all samplesfile
  pickAFile()sound makeSound( file )
• SoundSample objects store a single sample
• Two ways of playing sounds
• play (sound ) spawns process to play sound
• blockingPlay( sound ) no spawning

Slides available atcourses.cs.vt.edu/cs1004/cs4
hs/
2
Sound Samples

• Samples retrieved either as
• collection/array of SoundSample
  objectscollection______________________________
  ______for sample in getSamples( sound)
  setSampleValue( sample, getSampleValue(sample)2)
  array_______________________________________s
  amples getSamples( sound)for s in range(0,
  getNumSamples(sound)) half getSampleValue(
  sampless ) / 2 setSampleValue( sampless,
  half )
• single SoundSample objectssample
  getSampleObjectAt( sound, 100 )

3
Normalize a Sound

• Normalizing sounds involves making them as loud
  as possibledef driver() file pickAFile()
  sound makeSound( file ) blockingPlay( sound
  ) normalize( sound ) blockingPlay( sound
  )def normalize( source )
• large 0
• for snd in getSamples(source)
• large max(large, abs(getSample(snd)) )
• scaler 32767.0 / large
• for snd in getSamples(source)
• loud scalergetSample(snd)
• setSample(snd, loud)

Code available atcourses.cs.vt.edu/cs1004/cs4hs
/
4
Reverse a sound

• In late 1969 a rumor started circulating that
  Paul McCartney of the Beatles had died in 1966
  and had been replaced by a double. To support
  this urban legend many reported that if one
  played the song "Revolution 9" from the white
  album backwards one could hear "Turn me on, dead
  man".
• Reverse the last 15 seconds of the song
  "Revolution 9" from the white album  rev9.wav
• Modify the normalize code by adding a reverse()
  function that swaps all the samples in a sound,
  (first last, second next-to-last, etc.).
• Extra-credit do not modify the original sound.

5
Fade Outs

• Create a new sound from copies of a sound, where
  the copies fade out with a delay between the
  copies

def fadeOut( snd1, delay, num ) s1rate
getSamplingRate(snd1) ends1 getLength( snd1
) snd2 makeEmptySound( ends1 (num 1)
num int(delay s1rate) ) ends2 getLength(
snd2 ) fadeAmplitude 1.0 posn2 0 for
echoCount in range( 0, num 1 ) for posn1
in range( 0, ends1-1 ) values1
getSampleValueAt( snd1, posn1) fadeAmplitude
setSampleValueAt( snd2, posn2, values1 )
posn2 posn2 1 if (echoCount lt num)
for pause in range(0, int(s1rate delay))
setSampleValueAt( snd2, posn2, 0 )
posn2 posn2 1 fadeAmplitude
fadeAmplitude 0.6 each fade is 60 of
previous return snd2
Code available atcourses.cs.vt.edu/cs1004/cs4hs
/
6
Blending Sounds

• Creates a new sound from existing sounds.
• Corresponding samples from the sounds are blended
  together.
• Blending involves adding percentages (50) of
  each sample together.
• Lab/class activity download a reading of the
  Gettysburg address and an instrumental recording
  of God Bless America and create a blending of the
  two, (i.e. sound mix).

7
ALVIN! Lurch?

• Sounds can be speeded up or slowed down by
  under-sampling or over-sampling.
• Here is a famous line from the classic Paul
  Newman movie "Cool Hand Luke" as spoken by the
  inimitable character actor Strother Martin 
  FailureToCommunicate.wav
• Code a function to speed up the sound by creating
  a new sound half as long as the original using
  every other sample from the original.
• Code a function to slow down the sound by
  creating a new sound twice as long as the
  original using every sample from the original
  twice.

8
Interpolation

• Under-sampling or over-sampling are just specific
  instances of linear interpolation (the same as
  nearest neighbor in image scaling).
• Given a length (sampling) factor, e.g., 0.80,
  1.15, return a new sound of the new length and
  sampling using linear interpolation.
• Linear Interpolation

x
For any new sound sample s the corresponding
sample x from the original sound s / (length
of new sound) length of original sound

9
Sound Projects

• Simple Telephony
• Given sound clips for each spoken digit, combine
  them to speak any given number.
• Sound Steganography
• Hide a message inside a sound file
• http//www.cs.uic.edu/i101/projects/proj4.html
• Mozarts Dice Game
• Create a waltz by pasting together pre-composed
  minuet trio clips.
• http//www.cs.cornell.edu/courses/cs1110/2008fa/as
  signments/a6/a6.html