Acoustics and PsychoacousticsBarbara Crowe – Music Therapy Director

August 2008

Notes from BC’s copyrighted materials for IHTP

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The Physics of Sound and Sound Perception

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Sound is a word of perception used to report the aural, psychological sensation of physical vibrationVibration is any form of to-and-fro motionTo perceive sound you must have:1. energy in the system, movement2. vibrating body3. medium of transmission4. receiver, someone to perceive

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Sine wave- graph of simple sound

Wavelength- distance from one point on the wave to the next

Properties of vibrating bodies1. elasticity2. momentum

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Periodic motion- ability of motion to repeat- one full repetition is a cycleProperties of the wave1. Period = amount of time for one cycle2. Frequency = number of cycles repeated in one second

- heard as pitch3. Amplitude = amount of displacement of the vibrating body

- heard as loudness4. Simple harmonic motion + restoration force is equal to force of displacement = frequency is independent of amplitude

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Sound must travel through a medium- properties of the medium determines speed and efficiency of

transmission – elasticity and density

Process of transmission is propagation- alterations of compressions and rarefactionsImpediments to propagation- reflection- diffusion- absorption- refraction- diffraction- interference (beating)

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All sound occurring naturally is complex soundComplex patterns of vibrationProduces the overtone series

Acoustics and PsychoacousticsBarbara Crowe – Music Therapy Director

August 2008

Notes from BC’s copyrighted materials for IHTP

7

Whenever a system that can vibrate with a certain frequency is acted on from the outside by a periodic disturbance that has the same frequency, vibrations of large amplitude can be produced in the systemResonance frequency of a vibrating body

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Sound decaySound envelop- initial transit- steady state- decayNoise

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Factors in the environment that influences the ability of sound to travel from the source to the earReverberationReverberant soundReverberation time - T

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Factors in room acoustics1. frequency range of instrument2. absorption qualities of the room3. room shape4. objects that could interfere5. echoes6. noise elements7. sound output to meet room size and configuration

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Hard to defineA number of ways to define music1. What are the elements or events that

make up music?2. What are the origins of music?3. What is the purpose or uses of music?4. What are musical behaviors or the

psychology of music?

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Rhythm- ordered characteristic of tonal succession- aspects of musical timing

1. duration2. beat3. meter4. tempo5. rhythmic pattern

Acoustics and PsychoacousticsBarbara Crowe – Music Therapy Director

August 2008

Notes from BC’s copyrighted materials for IHTP

13

Melody- movement of tones over time that creates a shape or contour- using intervals or the relationship between notes of a melodyHarmony- vertical pitch structure- tonality or loyalty to a toneTimbre- characteristic of sound that

distinguishes one tone from another when pitch and loudness are constant

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Musical form- overall design of composition- musical styleDynamics- five dynamic ranges possibly musically

pp = very quietp = quietmp = medium or middlef = loud

ff = very loud

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Divine giftBiology

1. Fundamental processes of neural activity2. Inherent ability programmed in the brain

like speech3. Necessary anatomical structures4. Music as a complex biological adaptation5. Inherent, abstract form of human

expressionCultural/social phenomena

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Pleasure/entertainmentAesthetic responseSupport to basic humanity as a moral forceTouching the DivineCommunicationEffects on activitySupport of human cultureHealing/ritual

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is the process by which sound is transmitted from the environment to our brainis the perception of sound input – assigning meaning to aural inputis a process of modeling the complex patterns of relationships of sound

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The sensory apparatus of hearing- functions as a receiver of sound and a

mechanism for changing mechanical energy of sound wave into the electro-chemical energy of the brain

Ear is divided into three part1. the outer ear

- pinna- ear canal or meatus- tympanic membrane- functions to gather and amplify sound waves

focusing them tothe tympanic membrane

Acoustics and PsychoacousticsBarbara Crowe – Music Therapy Director

August 2008

Notes from BC’s copyrighted materials for IHTP

19

2. middle ear- ossicles or 3 bones of middle ear

- functions to increase the power and decrease size of the vibration

- Eustachian tube- functions to equalize air pressure

- acoustic reflex- two muscles, tensor tympani and

stapedius- functions to stiffen the ossicles to protect

the ear3. inner ear

- vestibule, a transitional area- 3 semi-circular canals, for vestibular sense- cochlea, the transducer of energy

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Anatomy- tube within a tube- oval window- cochlear duct- Organ of Corti- basilar membrane- tectorial membrane

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Function

- coding for pitch and loudness perception

- place theory of pitch perception

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Neurons- properties of irritability and conductivity - anatomy

cell body with nucleusdendritesaxonsynapsepre- and post-synaptic terminalsneurotransmittersmyelin sheath

- neural transmissionaction potentialsodium pumpchemical neurotransmitters over the synapse

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Auditory nerve bundle- afferent and efferent pathways

Impact of auditory nerve on the brain- lower brain/brain stem

reticular activating formationcerebellum

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- Mid-brain/limbic systemthalamusamygdalahippocampushypothalamus

- Upper brain/cerebrumcerebral cortexfour hemispheres - Corpus Colosum

Auditory pathways to the brain- two contralateral- two ipsilateral

Sympathetic and Parasympathetic nervous systems

Acoustics and PsychoacousticsBarbara Crowe – Music Therapy Director

August 2008

Notes from BC’s copyrighted materials for IHTP

25

Pitch is our subjective evaluation of the frequency of simple sound or the fundamental of complex soundBasilar membrane and pitch perception- the critical band

Factors and processes in pitch perception- audible hearing range- duration of sound- Place Theory of Pitch Perception

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- Periodicity Pitch Theory- Gestalt Theory of Perception

- The Law of Common Fate

Pitch Perception- difference limen- perfect or absolute pitch- combination tones

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Subjective evaluation of the strength of soundDecibel scale (dB)Factors influencing loudness perception- hearing mechanism

- frequency

Loudness discriminationVolume and density

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Parameter of sound that distinguishes one tone from another even when pitch and loudness is the sameFactors in determining timbre- characteristics of the initial transient- variations in the components of the complex tone

- it’s all about overtones- resonance of the instrument – formant regions- vibrato

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Consonance and dissonanceIntervals, scales, tuning and temperament- scale – pattern of audible frequencies arranged in

an ascending or descending order- interval – separation of two tones

- expressed as a ratio relation of the frequencies of the two notes in the interval

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All are derived from the Pythagorean scale of Pythagoras of Greece- Pythagorean comma- just intervals- enharmonic equivalentsModifications of Pythagorean Scale –temperament- Just intonation- Meantone intonation- Equal temperament

Acoustics and PsychoacousticsBarbara Crowe – Music Therapy Director

August 2008

Notes from BC’s copyrighted materials for IHTP

31

Successive combinations of tones placed in a temporal sequence- contour- tonality

Harmony- perception of simultaneously sounding tones

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Rhythm as stimulus in music- beat- meter- tempo- accentRhythm as response – theories- Instinctive Theories- Physiological Theories- Perceptual Motor Response Theories- Learning Theories

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Tactile on the skinBody resonanceHapticKinesthesisProprioceptionSynesthesia

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Criteria for a skilled motor behavior- fine motor skill- serial skill- movement in a hierarchical organization- spatial organization- temporal organization- involves sensory integration- involves feedback or knowledge of resultsPhysiological Componenets

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Plucked string instrument

Stretched string is capable of producing a full range of overtones◦ Dependent on where string is plucked

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Physiological Response- Thalamic response- Galvanic Skin Response (GSR)- Brain waves

- delta (0-4Hz)- theta (4-8Hz)- alpha (8-13 Hz)- beta (13-30 Hz)- gamma (over 30 Hz)

- changes in muscle tension- universal movement patterns and emotional states- biochemical responses

Acoustics and PsychoacousticsBarbara Crowe – Music Therapy Director

August 2008

Notes from BC’s copyrighted materials for IHTP

37

Affective response to music- emotions- feelings- mood- temperament

Aesthetic response

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Human Bio-Energy fieldsDense energy- Electromagnetic energy - piezoelectric property- Bodily acoustic energySubtle energy- non-physical yet active field

Non-Hertzian Energy- quantum field

- consciousness and thought