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# The Physics of Sound Sound begins with a vibration of an object Vibrating object transfers energy to air medium All complex vibration patterns seen as.

## Presentation on theme: "The Physics of Sound Sound begins with a vibration of an object Vibrating object transfers energy to air medium All complex vibration patterns seen as."— Presentation transcript:

The Physics of Sound Sound begins with a vibration of an object Vibrating object transfers energy to air medium All complex vibration patterns seen as a combination of many simple vibration patterns Simple harmonic motion Elastic restoring force Move object from equilibrium point, force returns it to equilibrium point Force is proportion to distance from equilibrium – Displacement

Simple Harmonic Motion Harmonic oscillations, or sinusoid (sine) curves

Simple Harmonic Motion, con’t Amplitude: Maximum displacement from one extreme to resting position Periodic vibration: Wave repeats itself Frequency (F): Number of cycles per sec (Hz) Period (T): Time (sec) to complete one cycle F = 1 / T Phase: Progression of wave through one cycle (measured in degrees)

Simple Harmonic Motion, con’t Decay of harmonic motion

Additivity and Superposition of Sine Waves

Additivity and Superposition of Sine Waves, con’t

Fourier Decomposition or Fourier Analysis

Fourier Decomposition, con’t Systems for Naming Frequency Components Freq.HarmonicsOvertonesPartials f 0 FundamentalFundamental1 st Partial 2f 0 2 nd Harmonic1 st Overtone2 nd Partial 3f 0 3 nd Harmonic2 st Overtone3 nd Partial 4f 0 4 nd Harmonic3 st Overtone4 nd Partial

Fourier Decomposition, con’t

The Perception of Pitch The physiology of the ear

The Perception of Pitch, con’t The place theory of pitch perception The basilar membrane as a set of independently tuned resonators Tone of single frequency causes corresponding place on basilar membrane to vibrate

The Perception of Pitch, con’t The frequency theory of pitch perception Basilar membrane vibrates to match frequency Because of refractory period, nerve fibers cannot encode high frequency Volley principle: nerve fibers working together can encode high frequencies

The Perception of Pitch, con’t The psychophysics of frequency The Mel Scale: Perceived pitch as a function of frequency Non-linear relation between frequency and pitch

The Perception of Pitch, con’t The Cognitive-Structural approach Octave equivalence Tones in a 2:1 frequency ratio have a special relation Evidence for octave equivalence: The harmonic series The musical pitch set

The Perception of Pitch, con’t The Cognitive-Structural approach Psychological evidence for octave equivalence Deutsch (1973) Standard Intervening SequenceComparison

The Perception of Pitch, con’t The Cognitive-Structural approach Psychological evidence for octave equivalence Octave-scramble nursery rhymes

The Perception of Pitch, con’t A bi-dimensional approach Tone / Pitch Height: A continuous dimension that increases with frequency Tone / Pitch Chroma: Circular component representing tones with 2:1 freq. ratio The pitch helix

The Perception of Pitch, con’t A bi-dimensional approach Shepard / Circular tones Single tones: Continuous glide: Tritone paradox:

The Perception of Loudness The psychophysics of loudness Audibility curves

The Perception of Loudness, con’t The psychological scale of loudness Sones scale

The Perception of Timbre The steady state component approach Components that remain the same over time Problems with the steady state view of timbre

The Perception of Timbre, con’t The importance of transient components Onset rapidity: Rate of onset of the tone Noise bursts: Amount/type of noise in beginning of tone Spectral energy shift: Changes in relative intensity of harmonics over time

The Perception of Timbre, con’t The perceptual similarity of musical timbre John Grey’s studies of musical timbre

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