lecture2 - CSE 471 Media Processing and Multimedia Sound...

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1 CSE 471 Media Processing and Multimedia Sound, Sinusoids, and Spectrum Striking a Tine Strings Tubes Analog vs. Digital

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2 CSE 471 Media Processing and Multimedia What is sound? Sound is a wave of vibrating pressure variations created in a medium Alternatively compressing and decompressing air
3 CSE 471 Media Processing and Multimedia A Tine x x is a function of time t: x(t) A metal rod that is flexible and springy

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4 CSE 471 Media Processing and Multimedia Forces on a Tine This is pushing back with force F x We’ll say F = -kx K is the “springiness factor” As an equation: F(t) = -kx(t)
5 CSE 471 Media Processing and Multimedia Newton’s Law This is pushing back with force F F = ma F = -kx Hence: ma=-kx Newton’s Law

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6 CSE 471 Media Processing and Multimedia What is x? x m k a kx ma ) / ( - = - = Any suggestions as to a function for x? What is acceleration? Solving for a
7 CSE 471 Media Processing and Multimedia Sine waves (Sinusoids) ) sin( ) sin( ) sin( ) cos( ) cos( ) sin( ) sin( ) ( 2 2 t t dt d t t dt d t t dt d t t x ϖ αϖ α - = - = = =

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8 CSE 471 Media Processing and Multimedia Solution m k and t t x Let t t dt d x m k a / ) sin( ) ( ) sin( ) sin( ) / ( 2 2 = = - = - = ϖ α
9 CSE 471 Media Processing and Multimedia Tines Vibrate as a Sinusoid Pattern of vibration is α sin( ϖ t), where α is the amplitude and ϖ is the frequency .

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10 CSE 471 Media Processing and Multimedia Important properties of sinusoids Frequency Number of radians per second ϖ Number of cycles per second (Hz) f= ϖ /2 π Frequency ranges: Infrasonic: 0 – 20Hz Audiosonic: 20Hz – 20KHz (what we hear) Ultrasonic: 20KHz on up. ..
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This note was uploaded on 07/25/2008 for the course CSE 471 taught by Professor Owen during the Fall '07 term at Michigan State University.

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lecture2 - CSE 471 Media Processing and Multimedia Sound...

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