The Physics of Sound
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Transcript of The Physics of Sound
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The Physics of SoundSound begins with a vibration of an objectVibrating object transfers energy to air mediumAll complex vibration patterns seen as a combination of many simple vibration patterns
Simple harmonic motionElastic restoring forceMove object from equilibrium point, force returns it to equilibrium pointForce is proportion to distance from equilibrium Displacement
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Simple Harmonic MotionHarmonic oscillations, or sinusoid (sine) curves
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Simple Harmonic Motion, contAmplitude: Maximum displacement from one extreme to resting positionPeriodic vibration: Wave repeats itselfFrequency (F): Number of cycles per sec (Hz)Period (T): Time (sec) to complete one cycleF = 1 / TPhase: Progression of wave through one cycle (measured in degrees)
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Simple Harmonic Motion, contDecay of harmonic motion
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Additivity and Superposition of Sine Waves
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Additivity and Superposition of Sine Waves, cont
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Fourier Decomposition or Fourier Analysis
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Fourier Decomposition, contSystems for Naming Frequency ComponentsFreq.HarmonicsOvertonesPartials
f0FundamentalFundamental1st Partial2f0 2nd Harmonic1st Overtone2nd Partial3f0 3nd Harmonic2st Overtone3nd Partial4f0 4nd Harmonic3st Overtone4nd Partial
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Fourier Decomposition, cont
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The Perception of PitchThe physiology of the ear
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The Perception of Pitch, contThe place theory of pitch perception
The basilar membrane as a set of independently tuned resonatorsTone of single frequency causes corresponding place on basilar membrane to vibrate
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The Perception of Pitch, contThe frequency theory of pitch perception
Basilar membrane vibrates to match frequencyBecause of refractory period, nerve fibers cannot encode high frequencyVolley principle: nerve fibers working together can encode high frequencies
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The Perception of Pitch, contThe psychophysics of frequency
The Mel Scale: Perceived pitch as a function of frequencyNon-linear relation between frequency and pitch
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The Perception of Pitch, contThe Cognitive-Structural approach
Octave equivalenceTones in a 2:1 frequency ratio have a special relationEvidence for octave equivalence:The harmonic seriesThe musical pitch set
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The Perception of Pitch, contThe Cognitive-Structural approach
Psychological evidence for octave equivalenceDeutsch (1973) Standard Intervening SequenceComparison
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The Perception of Pitch, contThe Cognitive-Structural approach
Psychological evidence for octave equivalenceOctave-scramble nursery rhymes
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The Perception of Pitch, contA bi-dimensional approach
Tone / Pitch Height: A continuous dimension that increases with frequencyTone / Pitch Chroma: Circular component representing tones with 2:1 freq. ratioThe pitch helix
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The Perception of Pitch, contA bi-dimensional approach
Shepard / Circular tones
Single tones:
Continuous glide:
Tritone paradox:
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The Perception of LoudnessThe psychophysics of loudness
Audibility curves
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The Perception of Loudness, contThe psychological scale of loudness
Sones scale
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The Perception of TimbreThe steady state component approach
Components that remain the same over timeProblems with the steady state view of timbre
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The Perception of Timbre, contThe importance of transient components
Onset rapidity: Rate of onset of the toneNoise bursts: Amount/type of noise in beginning of toneSpectral energy shift: Changes in relative intensity of harmonics over time
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The Perception of Timbre, contThe perceptual similarity of musical timbreJohn Greys studies of musical timbre