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Chapter 11

Chapter 11 - study notes

Course Code
Matthias Niemeier

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Explain the temporal code of sound frequency. What is coded? How is it coded, whats the
proper scientific term for it? What are the limits of temporal coding? How could this
limitation be overcome?
-shearing directly related to sound pressure level. So spatial code of frequency has to do
with which hair cell is beign stimulated and which part of organ of corti. Temporal code
tells us about frequency by looking at oneee hair cell. Does so at certain point, limited
1000Hz cuz hair cell cant fire much faster than that. This has to do with action potentials
that has activated but then has to build up itz resting potentials, a minimal of time /b/ 2
action potentials, A.P limited. This diff from photoreceptors that can be faster. You can still
go beyond that cuz u have more than 1 hair cell but then u still have to join all thediff
neurons together and when joining neurons it cant be that accurate, another limitation. So
only works up to 4000-5000Hz.
Spoken words and music are complex sounds w/meaning, convey emotion
Pythagoras convinced musical intervals they found most pleasing should provide greatest
insights to universe. Music tell story, affect ppls moods, emotions, when ppl hear pleasant-
sounding chords preceding a word, they are faster to respond that a word such as charm is
positive and they are slower to respond tat a word such as evil is negative.
Music therapy sing, dance, play to music. Music show deep physiological effects. Prozac
increases serotonins so does music that are disagreeable. When ppl listen to high
pleasurable music, they experience changes in hear rate, muscle electrical activity, and
respiration, blood flow increases in brain regions that are thought to be involved in reward
and motivation
Important characteristic of any acoustic signal is frequency. Brain structures for processing
sounds are tonotopically organized to correspond to frequency. Psychological quality of
perceived frequency is pitch
Musical pitch musical notes melodies. Octave = interval /b/ 2 sound frequencies having
a ratio of 2:1. So hte nearer any 2 sounds were in frequency, the nearer they were in pitch.
When one of two periodic sounds is double the frequency of the other, those 2 sounds are
one octave apart. For ex C4 = 261.6Hz and C3 = 130.8Hz. this is called just intonation, so
frequencies of sounds in simple ratios w/one another. Equal temperament is common in
western music

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Musical pitch described in 2 dimensions: 1) tone height = sound quality corresponding to
level of pitch. It is monotonically related to frequency 2) tone chroma = sound quality
shared by tones that have same octave interval
If pitch is a helix, tone and frequency increases on height with helix. The circular laps
around helix correspond to changes in tone chroma. At same pt along each lap around helix,
a sound lies on a vertical line and al sounds along that line share same tone chroma and
separated by octaves
Both a place code and temporal ode can be used in perception of pitch. Neurons in auditory
nerve signal frequency both by their location in cochlea and by timing of their firing. For
frequencies greater than 5 kilohertz (kHz). For frequencies greater than 5kHz, temporal
coding does not contribute to perception of pitch, pitch discrimination becomes appreciably
worst cuz only place coding can be used. Most instruments only produce notes below 4 kHz.
Frequencies greater than 5kHz does not convey melody well, listeners have great difficulty
perceiving octave relationships /b/ tones when one or both tones have a frequency greater
than 5kHz
Cord = combo of 3 or more musical notes w/diff pitches played same time. If itz 2 notes
played same time = dyad. Major distinction /b/ chords is whether they are consonant or
dissonant. Perceived be most pleasing, consonant cords are combo of notes in which ratios
/b/ note frequencies are simple. Ex of consonant cord is octave 2:1 ratio. Also 3:2 the perfect
fifth, perfect fourth 4:3. Dissonant intervals are defined by less elegant ratios = minor
second 16:15, augmented forth 45:32 not sound very pleasing
Musical scales and intervals vary widely across cultures. While relationships /b/ notes such
as octaves are relatively universal, diff musical traditions use diff # of notes and spaces /b/
notes within an octave.
Diff ppl hear musical notes in diff way. Cultures estimate intervals /b/ notes according to
how well these notes correspond to their culture. Infants seem equipped to learn w.e scale is
used in their environment, kids can detect deviation from many culture scale but adults
only detect their own.
Melody = formed by notes or cords, it is defined by itz contour pattern of rises and
declines in pitch, rather than by an exact sequence of sound frequencies. It is not a sequence
of specific sounds, ex if u shift every note of a melody by one octave and the resulting
melody is the same. Can sing melody in diff pitch. Tempo = perceived speed of presentation
of sounds, itz duration

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Music varies in rhythm, everything in life is rhythm, we perceive it in rhythm even if it not.
We are predisposed to group sounds into rhythmic patterns. Sound tat are longer, louder,
higher in pitch all are more likely to be heard as leading their group. Timing relationship
/b/ one sound and the others in a sequence also helps determine accent.
Ex of musical rhythmic grouping is syncopation or syncopated auditory polyrhythms. It is
when 2 rhythms ware played together and one rhythm dominates, listeners tend to perceive
timing of beats in nondominate rhythm adjusted to conform/dominant rhythm, the
nondominate rhythm will travel back and forward to meet up with dominate
Learning of melodies begin quite early in life, even if it is not simple melodies
Strong relation /b/ speech production and speech perception. 5000 languages, 850 diff
speech sounds, our flexibility is due to unique structure of human vocal tract = airway
above larynx used for production of speech. It includes oral tract and nasal tract. Human
larynx is positioned quite low in throat unlike other animals, so we are more susceptible to
choking than any other animal. Also we cant swallow and breathe at same time but this
low position allow us to communicate
Production of speech has 3 components: respiration (lungs), phonation (vocal cords) and
articulation (vocal tract)
To initiate a speech sound, diaphragm pushes air out of lungs through trachea and up to
larynx. At larynx, air must pass through 2 vocal folds, which are made up of muscle tissue
that can be adjusted to vary how freely air passes through opening /b/ them. Adjustments =
types of phonation. Rate at which vocal folds vibrate deepens on their stiffness and mass.
Kids like thin guitar strings, have small vocal folds thus have high pitched voice. Men
generally have lower pitched voices than women cuz of testosterone that lead to increase the
mass of vocal folds
If we measure sound right after larynx, we would see that vibration of vocal folds creates a
harmonic spectrum, if we were to just listen to that part of speech it would sound like a
buzz. The first harmonic corresponds to actual rate of physical vibration of vocal folds, the
fundamental frequency. Main part of producing speech sounds occurs above larynx and
vocal folds
Area above larynx is oral tract and nasal tract is called vocal tract. We have many ability to
change shape of vocal tract ie move lips, jaw, tongue etc, these manipulations referred to as
articulation = act or manner of producing a speech sound using vocal tract. Rmb changing
size and shape of space through which sound passes increases and decreases energy at diff
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