Acoustics-and-Psychoacoustics-B-Crowe, PSIONIC, Brainwave & Psychoakustyka
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Acoustics and Psychoacoustics
Barbara Crowe – Music Therapy
Director
August 2008
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Sound is a word of perception used to
report the aural, psychological sensation of
physical vibration
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Vibration is any form of to-and-fro motion
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To perceive sound you must have:
1. energy in the system, movement
2. vibrating body
3. medium of transmission
4. receiver, someone to perceive
The Physics of Sound and Sound Perception
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Periodic motion
- ability of motion to repeat
- one full repetition is a cycle
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Sine wave
- graph of simple sound
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Wavelength
- distance from one point on the wave to the next
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Properties of vibrating bodies
1. elasticity
2. momentum
Properties of the wave
1. Period = amount of time for one cycle
2. Frequency = number of cycles repeated in one second
-heard as pitch
3. Amplitude = amount of displacement of the vibrating
body
-heard as loudness
4. Simple harmonic motion + restoration force is equal to
force of
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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
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Process of transmission is propagation
- alterations of compressions and rarefactions
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Impediments to propagation
-reflection
-diffusion
- absorption
-refraction
- diffraction
- interference (beating)
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All sound occurring naturally is complex
sound
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Complex patterns of vibration
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Produces the overtone series
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Notes from BC’s copyrighted materials for IHTP
Acoustics and Psychoacoustics
Barbara Crowe – Music Therapy
Director
August 2008
`
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 system
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Resonance frequency of a vibrating body
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Sound decay
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Sound envelop
- initial transit
-steady state
-decay
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Noise
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Factors in room acoustics
1. frequency range of instrument
2. absorption qualities of the room
3. room shape
4. objects that could interfere
5. echoes
6. noise elements
7. sound output to meet room size and configuration
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Factors in the environment that influences
the ability of sound to travel from the
source to the ear
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Reverberation
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Reverberant sound
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Reverberation time - T
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Hard to define
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A number of ways to define music
1. 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. duration
2. beat
3. meter
4. tempo
5. rhythmic pattern
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Notes from BC’s copyrighted materials for IHTP
Acoustics and Psychoacoustics
Barbara Crowe – Music Therapy
Director
August 2008
`
Melody
- movement of tones over time that creates
a shape or contour
- using intervals or the relationship
between notes of a melody
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Harmony
- vertical pitch structure
- tonality or loyalty to a tone
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Timbre
- 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 style
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Dynamics
-
five dynamic ranges possibly musically
pp = very quiet
p = quiet
mp = medium or middle
f = loud
ff = very loud
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Divine gift
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Biology
1.
Fundamental processes of neural activity
2.
Inherent ability programmed in the brain
like speech
3.
Necessary anatomical structures
4.
Music as a complex biological adaptation
5.
Inherent, abstract form of human
expression
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Pleasure/entertainment
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Aesthetic response
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Support to basic humanity as a moral force
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Touching the Divine
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Communication
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Effects on activity
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Support of human culture
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Healing/ritual
Cultural/social phenomena
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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
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Ear is divided into three part
1. the outer ear
- pinna
- ear canal or meatus
- tympanic membrane
- functions to gather and amplify sound waves
focusing them tothe tympanic membrane
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is the process by which sound is
transmitted from the environment to our
brain
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is the perception of sound input – assigning
meaning to aural input
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is a process of modeling the complex
patterns of relationships of sound
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Notes from BC’s copyrighted materials for IHTP
Acoustics and Psychoacoustics
Barbara Crowe – Music Therapy
Director
August 2008
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 ear
3. 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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Neurons
- properties of irritability and conductivity
-anatomy
cell body with nucleus
dendrites
axon
synapse
pre- and post-synaptic terminals
neurotransmitters
myelin sheath
- neural transmission
action potential
sodium pump
chemical neurotransmitters over the synapse
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Function
- coding for pitch and loudness perception
- place theory of pitch perception
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- Mid-brain/limbic system
thalamus
amygdala
hippocampus
hypothalamus
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Auditory nerve bundle
- afferent and efferent pathways
- Upper brain/cerebrum
cerebral cortex
four hemispheres - Corpus Colosum
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Auditory pathways to the brain
- two contralateral
- two ipsilateral
Sympathetic and Parasympathetic nervous systems
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Impact of auditory nerve on the brain
- lower brain/brain stem
reticular activating formation
cerebellum
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Notes from BC’s copyrighted materials for IHTP
Acoustics and Psychoacoustics
Barbara Crowe – Music Therapy
Director
August 2008
- Periodicity Pitch Theory
- Gestalt Theory of Perception
- The Law of Common Fate
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Pitch is our subjective evaluation of the
frequency of simple sound or the
fundamental of complex sound
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Basilar membrane and pitch perception
- the critical band
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Factors and processes in pitch perception
- audible hearing range
- duration of sound
- Place Theory of Pitch Perception
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Pitch Perception
- difference limen
- perfect or absolute pitch
- combination tones
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Subjective evaluation of the strength of
sound
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Decibel scale (dB)
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Factors influencing loudness perception
-hearing mechanism
-
frequency
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Loudness discrimination
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Volume and density
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Parameter of sound that distinguishes one
tone from another even when pitch and
loudness is the same
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Factors 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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All are derived from the Pythagorean scale
of Pythagoras of Greece
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Pythagorean comma
- just intervals
- enharmonic equivalents
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Modifications of Pythagorean Scale –
temperament
- Just intonation
- Meantone intonation
- Equal temperament
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Consonance and dissonance
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Intervals, 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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Notes from BC’s copyrighted materials for IHTP
[ Pobierz całość w formacie PDF ]