audition

fundamental frequency

lowest frequency component of a sound (1st harmonic)

lowest frequency component of the harmonic spectrum

ex - 262, 542, 786, 1048 Hz

missing fundamental effect

perception of fundamental frequency when it is not present due to harmonics adding at the fundamental frequencies period

timbre

when sounds with same loudness and pitch sound different

due to harmonics and high frequencies

timbre contrast

enhanced perception of differences when distinct sounds are played together

timbre after effect

perception of full harmonic spectrum is skewed when played after a harmonic with missing elements

attack

part of sound where amplitude increases

onset

decay

part of sound where amplitude decreases

offset

auditory scene

entirely of sounds audible in a given moment

conveys information about evens happening in that moment

auditory stream segregation

perceptual organization of a complex acoustic signal into separate auditory events for which each stream is heard as a separate event

grouping by timbre

uses Gestalt law of similarity

ventriloquist effect

audio-visual illusion where sound is misperceives as coming from a source that is moving appropriately when it is actually coming from an invisible source

visual > auditory for location of a sound

restoration

in spite of interruptions, one can still “hear” sound

based on Gestalt law of good continuation

higher-order sources can help fill in the blanks

Pythagoras

numbers and music intervals

musical range

25 - 4500 Hz

pitch

psychological aspect of sound related mainly to fundamental frequency

octave

interval between two sound frequencies that have a 2:1 ratio

tone height

sound quality corresponding to the level of pitch

monotonically related to frequency

tone chroma

sound quality shared by tones that have the same octave interval

musical helix

visualized pitch

instruments

produce notes < 4000 Hz

chords

2+ notes played simultaneously

constant or dissonant

consonant

chord with simple ratios of note frequencies

ex - 3:2, 4:3

dissonant

chords with complex ratios of note frequencies

ex - 16:15, 45:32

pelog

Javanese scale with fewer notes than western scale

melody

arrangement of notes/chords in succession (chroma and rhythm) forming a gestalt

tempo

perceived speed of presented sounds

fugue

2+ voices build on a theme introduced at the beginning and repeat it in different pitches

classical music composition technique

Bayesian inference

we actively predict that is likely to happen next in music

vocal tract

airway above larynx used for production of speech sounds

respiration

inhaling during speech pushes air out of lungs, through trachea, to the larynx

larynx

two vocal folds air passes through to make speech sounds

larger in men, smaller in children

phonation

occurs at the larynx

air passes between the two vocal folds

articulation

occurs in vocal tract

manipulation of jaws, lips, tongue body, tongue tip, and velum/soft palate

resonance characteristics

created by changing size and shape of vocal tracts to affect sound frequency produced

formants

peaks in speech spectrum

concentrations in energy occur at difference frequencies depending on length of vocal tract

spectrogram

pattern for sound analysis that provides 3D display plotting time, frequency and intensity

vowels

open vocal tract

consonants

obstructed vocal tract

voicing

whether vocal cords are vibrating or not

coarticulation

successive speech units overlap in articulatory patterns

occurs in fast speech production

spectral contrast

we perceive syllables on the basis of the relative change in the spectrum

pressure

vibrations of objects cause surrounding molecules to vibrate which causes ________ change in medium

amplitude

magnitude of displacement of a sound pressure wave

intensity

amount of energy falling on a unit area

decibels

ratio between pressure of some sound and the pressure of the reference sound p0

= 20log(p/p0)

loudness

psychological aspect of sound related to perceived intensity/magnitude

frequency

number of times per second that a pattern of pressure change repeats

human hearing range

20 - 20 000 Hz

sine waves

all sound can be describe as a combination of _____ _______

spectrum

representation of relative energy present at each frequency

Fourier analysis

any signal (sound) can be separated into component sine waves at different frequencies, adding these sine waves produces the original signal

harmonic spectrum

frequencies of its components are integer multiples of lowest frequency

pinna

outside of ear that collects sounds and funnels them into the ear canal

tympanic membrane

vibrates in response to sound

at end of ear canal

middle ear

3 ossicles (malleus, incus and stapes) which are the smallest ponds in the body

transmit tympanic membrane vibrations to the oval window

inner ear

translates changes in sound pressure into neural signals

cochlea which contains oval/round window and 3 canals

cochlea

spiral structure of the inner ear containing the organ of Corti

filled with water fluids in 3 parallel canals

vestibular canal and tympanic canal are separated by membranes

organ of Corti

in cochlea, sits on top of basilar membrane, covered by tectorial membrane

made of hair cells, dendrites of auditory nerve fibers, and scaffold

inner hair cells send afferent information

outer hair cells are efferent/feedback system

vibration pathway

ear canal → tympanic membrane → middle ear bones → oval window → vestibular canal

round window

absorbs extremely intense sounds/pressures

intense sound pathway

helicotrema → cochlea → tympanic membrane → round window

tectorial membrane

extends atop organ of Corti

gelatinous structure

place code

different parts of cochlea tuned to different frequencies

information about frequency is coded by place along cochlear partition

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threshold tuning curve

map plotting thresholds of neuron in response to sine wave in varying frequencies at lowest intensity that will give rise to a response

rate saturation

point where nerve fiber is firing as rapidly as possible, incapable of further stimulation

insointensity curves

measures 1 nerve fiber’s firing rate to a wide range of frequencies at the same intensity level

phase locking

firing of a single neuron at one distinct point in the period of a sound wave at a given frequency

temporal code

tuning of different parts of the cochlea to different frequencies

information about sound wave is coded by timing of neural firing

volley principle

multiple neurons can provide temporal code for frequency if each neuron fires at a distinct point in the period but does not fire every period

vestibulocochlear nerve

cranial nerve VIII, one for each ear

synapses in cochlear nucleus

superior olive

early brainstem region that receives inputs from both ears

inferior colliculus

midbrain nucleus in auditory pathway

medial geniculate nucleus

part of the thalamus that relays auditory signals to the temporal cortex and receives input from the auditory cortex

tonotopic organization

neurons responding to different frequencies are organized anatomically in order of frequency

primary auditory cortex (A1)

first area in temporal lobe where brain processes acoustic information

belt area

adjacent to A1, responds to more complex characteristics of sound

parabelt area

lateral and adjacent to belt area, responds to more complex sounds and input from other senses

psychoacoustics

study of psychological correlation to physical dimensions of acoustics

branch of psychophysics

auditory threshold

map of just barely audible tones of varying frequencies

equal loudness curves

sound played at constant level is perceived as louder when played for a greater duration

indicative of temporal integration

otosclerosis

abnormal growth of ossicles (3 small bones in inner ear)

sensorineural hearing loss

common auditory impairment due to defects in the cochlea or auditory nerve when hair cells are injured

common hearing loss

damage to hair cells due to excessive exposure to noise

young range = 20 - 20 000 Hz

old range = 20 - 15 000 Hz

interaural time difference (ITD)

difference in time between a sound arriving at one ear vs the other

azimuth

used to describe locations on imaginary circle that extends around us in a horizontal plane

interaural level difference (ILD)

difference in intensity between a sound arriving at one ear vs the other

largest at +/- 90 degrees & related to angle to source

cone of confusion

regions in space where all sound produce the same time and level differences

head related transfer function (HRTF)

pinnae, ear canal, head and torso change intensity of sounds with difference frequencies that arrive at each ear from different locations in space

varies with elevation and azimuth

inverse square law

intensity of sound decreases with distance

relative intensity cue

spectral composition of sounds

higher frequencies decrease the energy more than lower frequencies as sound waves travel from source to ear

direct/reverberant energy

sound distance cue based on how much direct/indirect sound waves are hitting your ears

more indirect (bouncing off other objects) the further away