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9 Dec 2012

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Musical instruments have multiple resonant qualities
produce complex tones that contain a fundamental frequency
produce a set of harmonics that are exact multiples of the fundamental
despite this, instruments produce a single pitch sensation (musical pitch)
equivalent to the pitch associated with the fundamental frequency
it is believed that the spatial arrangement of wave patterns on the basliar membrane
produced by the harmonics is responsible for their coherence into a single pitch
2:1 frequency ratio
represents the fundamental interval of musical pitch
effective range of musical pitch spans seven octaves
beyond this range, the harmonics are no longer suitable as musical sounds
an octave can be further divided into intervals, called notes
positions of notes in an octave – chroma
equally tempered scale – established by Bach
Western musical culture
broken into 12 equal divisions known as semitones
musical notes are represented by staff notation
allows musicians to play music without knowing pitch composition
musicians have a well-developed sense of relative pitch as a result of listening to and
playing tonal sequences
perfect pitch – ability to identify an isolated tone by name, is much more difficult
timbre – a difference in tone quality
arises from difference intensity distributions of the harmonics
each instrument has its own characteristic intensity distribution for each harmonic of a note
causes subtle differences in the neural activation at the respective points in the basilar
three major categories of musical instruments:
music relies on two distinct qualities:
tonal superpositions (simultaneous appearance of musical tones)
tonal sequences (sequential appearances of musical tones)
auditory system is able to distangle the individual components of a musical note in a
superposition, such as a chord, and associate them with an individual note
constant superpositions occur when they sound pleasant
dissonance arises from harsh and clashing combinations
arise when two or more tones produce interference among their activational patterns
on the basilar membrane
tonal sequences are responsible for the melodic quality of music, whih in turn creates
rhythm and tempo
the sequential sound pattern of music resonates with some internal rhythm in the brain
that in turn leads to the activation of higher emotional centres
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three areas of research on speech perception:
speech production
speech comprehension
brain structures responsible for each
speech is the only structured sensory stimulus produced by humans
vocalization process leading to speech involves the subglottal system, larynx, and vocal
vocal folds (glottis) are controlled by muscles during exhalation to produce a buzz-
like sound that is the shaped by different structures of the vocal tract to produce the
audible sounds of speech
speech can be broken down into words
words can be broken into syllables
syllables are broken into phonemes
phonemes are the smallest unit of speech
can be represented symbolically by a single character
speech can be represented by its pressure waveform
this does not contain frequency information
sound spectrograph – provides a visual display of frequency as a function of time
intensity is represented by the darkness of the markings on the graph
specific phonemes appear as bands of resonant frequencies called formants
vowel sounds are composed of low frequencies and appear near the bottom of the
consonants are made up of higher frequencies that appear near the top
all human languages are structured, symbolic, and arbitrary systems
the goal of psycholinguistic research is to understand the mechanisms that underline human
language use
sentences are broken down into four different processing stages:
words, sounds, and non-speech sounds must be isolated and recognized (sensory
words must be identified and their meanings understood (cognitive psychology)
grammatical rules must be applied to derive meaning from a sequence of words
(cognitive psychology)
meaning must then be interpreted within the specific context (cognitive psychology)
the unique human ability of speech expression and comprehension arieses due to the
presence of the specialized brain areas dedicated to language
Wernicke's aphasia
ability to speak
inability to understand language
damage to Wernicke's area – speech recognition/comprehension area (L hemisphere)
Broca's aphasia
slurred and slow speech
maintenance of language understanding
damage to Broca's area – speech production area (L hemisphere)
for many centuries, it was believed that light was made up of particles
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many aspects of light cannot be explained this way
light travels both like a particle and a wave
composed of particles that travel in a wave-like manner
light is an example of electro-magnetic radiation
electro-magnetic radiation – moving energy field consisting of both oscillating electrical
and magnetic fields
wavelength - a full cycle of the electric field
visible light spans the wavelength of 400-700 nm
blue – short wavelengths
green and yellow – middle wavelengths
red – long wavelengths
it is convenient to consider light as emanating form a point source when describing its
interaction with objects
optical infinity – a distance of 20 ft. (6m) from the point source, the divergence of light
rays becomes so negligible that they can be considered parallel
represents the initial condition when examining the interaction of light with objects
light can be absorbed, reflected, or scattered by an object
light can also be transmitted through transparent objects
refraction – phenomenon that arises at the border between two different media
causes the light rays to converge or diverge away from the normal (the plane
perpendicular to the boundary)
the greater the difference in refractive index between the two media, the greater the
refraction at the boundary
the curved surface of a lens are ideally suited for refraction
with a concave lens, light rays are refracted so they emerge from the lens in a divergent
can never create a true image of the point source
with a convex lens, light rays are refracted so they emerge from the lens in a convergent
produces a true image at a certain distance away from the lens
distance depends on the optical power of the lens
optical power of the lens is determined by the curvature of the lens surfaces
and the refractive index of the lens
image distance increases as the object is brought closer to the lens
the eye is made up of many components, notably the cornea, crystalline lens, aqueous and
vitreous humours, and retina
the eye is both an optical instrument and a device that converts the energy in visible light
into neural signals
optical properties arise at the air-cornea surface by way of the crystalline lens
emmetropic eye – one whose optical power is precisely sufficient to converge light rays from
a point source at optical infinity into an image on the retina
the retinal image is inverted and horizontally flipped
objects located closer than optical infinity require the eye to increase its optical power in
order to create a focused image on the retina
accomplished by the process of accommodation
an increase in the surface curvature of the lens surfaces to provide extra optical
a reflex process driven by the blur signal on the retina
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