CS1371 Introduction to Computing for Engineers

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CS1371Introduction to Computing for Engineers

• Sound -1

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Administrivia

• HW8 still due Thursday
• Lab 2 is out. Due Friday 10/21 midnight.
• No school on Mon Tues (as if you didn't
  know!!!)
• Reading
• Sound Smith, Chapter 18

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Media Player Beethoven's 9th

• Actual signal - one dimensional but not much
  information - (show using Bars and Waves gt
  Scope)
• Show graphic output of frequency in Media Player
• Horiz and Vert axis
• Freq (pitch) band
• Intensity Power Energy

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Analog to Digital to Digital to Analog

• When sound hits your ears digital or analog?
• Or light hits your eyes
• First step is going digital - three questions
• How often?
• What range?
• How precise?
• After digitization, have lots of numbers (44k
  samples per second for CD, 8k for others) of some
  bit length (8, 16, 32, etc)
• Can splice those numbers (Today).
• Can change those numbers (filtering) (Friday).
• Then convert back to voltage and output thorugh
  speakers or on a printter

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Music in matlab

• Load handel
• Y 73k samples, at 8k per second - how many
  seconds
• Plot(y,Hz)
• Sound(y,Hz)

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Sound in Matlab

• Sound(X, Hz) takes a vector of samples (X) that
  were sampled at Hz (Fs) samples per second and
  plays it as a sound.
• Assumes range of -1 to plus 1 (clips)
• Hz defaults to 8192 Hz (hertz)
• Example
• x 110000 yy sin(x)
• sound(yy)
• plot(yy)

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Can play with frequency through Hz

• Sound(yy,4096) - longer but lower
• Sound(yy,16000) shorter but higher
• For vector Nx1 or 1xN doesn't matter
• For stereo Nx2

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Splicing

• If sounds these are just arrays (vectors) of
  numbers, then we already know how to cut and
  pslice pieces of sound

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Removing Dear

• figure
• damn, Hzd wavread('sounds\sp_givdamn2.wav')
• subplot(1, 2, 1)
• plot(damn)
• sound(damn, Hzd)
• pause(length(damn)/Hzd)
• lo 4500
• hi 8700
• sdamn damn(1lo) damn(hiend) .5
• subplot(1, 2, 2)
• plot(sdamn)
• sound(sdamn, Hzd)

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Houston Problem

• houston, Hzh wavread('sounds\sp_a13prob.wav')
  
• subplot(1, 2, 1)
• plot(houston)
• sound(houston, Hzh)
• pause(length(houston)/Hzh)
• clip 110000
• prob houston(clipend)2
• subplot(1, 2, 2)
• plot(prob)
• sound(prob, Hzh)
• pause(length(prob)/Hzh)

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We Don't Care

• speech prob sdamn
• plot(speech)
• sound(speech, Hzt)

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Playing with pitch through time

• If you change the number of samples per second,
  the tone changes. (Remember sine)
• Likewise, we can stretch or shrink the signal
  (keeping the sampling rate the same) to change
  the pitch. (Better)

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Scale.m