audition Flashcards
wave of a pure tone can be described as a
sine wave
sound?
vibration in the air that travels by pressure waves
frequency
pitch
Hz
how many full waves in a second
amplitude
loudness
dB
height of wave
phase
timbre?
degrees
How far through the wave are we? timing/position
what is a natural sound?
a collection of simple sine waves added together
addition of 2 waves of same frequency, same amplitude and same phase =
sine wave
same frequency and phase but amplitude doubles
complex wave =
adding 2 waves of different frequencies
decomposing a complex sound into its sine wave components
fourier analysis
in a complex wave what is the component with the lowest frequency that gives that note its characteristic pitch
fundamental
peripheral auditory system
inner ear
middle ear
outer ear
central auditory system
cells in the brainstem and cerebral cortex
where is the organ of corti
along the basilar membrane
pinna
flexible flap on the outside of ear
meatus
external auditory canal, focuses sound waves into the ear
component of middle ear
tympanic membrane (ear drum) ossicles/bones
auditory transduction
meatus focuses sound into the ear
- > tympanic membrane vibrates in response to sound
- > ossicles transmit energy from eardrum through cochlea
- > fluid displacement in cochlea causes vibration in basilar membrane
- > inner hair cells, in organ of corti, stimulate the auditory nerve
- > auditory nerve sends signal to the brain
largest vibration near the stapes and base of the cochlea
high frequency
largest vibration near the apex of cochlea
low frequencies
auditory nerve cells filter….
on the basis of frequency.
e.g., band-pass filter
BASILAR MEMBRANE performs the filtering
place code
‘frequency-to-place’
hair cells have a ‘characteristic frequency’ that they are ‘tuned’ to.
determined by where they are on the basilar membrane
how does our ear cover the full dynamic range of human hearing?
2 groups of auditory fibres with different roles
high spontaneous rate fibres = lower sound intensities
low spontaneous rate fibres = higher intensities
cortical organisation for audition
tonotopic organisation.
primary auditory cortex is organised in terms of sound frequency
role of outer hair cells in the cochlea
amplify and fine tune the repsonses of the inner hair cells
feedback mechanism
motile response
when outer hair cells change their size in response to impulses from higher areas
3 major theories of pitch perception
place theory
pattern theory
timing theory
place theory
frequency to place conversion of the basilar membrane
* place coding best for high freq simple tones
but doesn’t account for missing fundamentals (if its missing it can’t go through a filter)
bandwidth
= RANGE of freqs that are transduced by this filter
wide abndwidth
= broad tuning
predicts poor ability to discriminate between frequencies
narrow bandwidth
sharp tuning
good frequency discrimination
masking
= noise.
need more intense signal to reach detection threshold
timing theory
timing of neural impulses carries frequency info (beats)
if fundamental not present our brain ‘fits it in’
ONLY possible for low-freq sounds
pattern theory
depends on resolved harmonics, finds the BEST FITTING harmonic series.
best with low frequencies
how is loudness measured?
matching and scaling tasks
loudness =
intensity of firing
excitation pattern model
overall loudness is proportional to the neural activity evoked by it in the auditory nerve.
monaural sound localisation
echoes resolve vertical localisation; PINNAE play a role
coming from up or down?
binaural sound localisation
horizontal localisation;
interaural time difference
interaural level difference
interaural time difference
difference in time of arrival depends on AZIMUTH (horizontal plane)
processed in MEDIAL SUPERIOR OLIVE
interaural level difference
difference in intensity level depends on frequency (low freq; diff small, high freq; diff large)
processed in LATERAL SUPERIOR OLIVE
if low freq which binaural sound localisation tool is used?
itd
if high freq which binaural sound localisation tool is used?
ild
cone of confusion
2 possible azimuths (front of behind)
solve; move head to introduce level and time differences
precedence effect
apparent sound source direction is determined by the earliest sound to arrive at the ear
complex waves must have
2 waves of diff frequencies
tectorial membrane
flexible structure lying on top of the basilar membrane
where in the ear does impedence mathching
inner ear
displacement of cochlear hair cells toward the taller stereocillia __________ the cell
despolarizes
tonotopic organisation
high freq largest vibration at stapes and base of cochlea
low freq largest vibration near apex of cochlea
linear filter
does not add components that were not present in the input
impedence matching
matches up the differing acoustic impedences of air and inner-ear fluid
phase locking
firing of hair cells/neural impulses in synchrony with the variation of pressure of the input sound
residue pitch
pitch heard in a complex wave due to BEATS rather then to resolvable harmonics
freq discrimination is best for….
low frequencies
ohm’s law
the auditory system constructs a separate representation for each frequency compoenet of a complex sound
missing fundamental is in a ________
complex tone
beats from unresolved harmonics, same as fundamental
known as…
residue pitch
pattern theory can’t explain…..
residue pitch from unresolved harmonics
place theory best explain
high freq pure tones
timing theory best for
low frequency pure tones
how is loudness matching acheived?
participant matches the intensity of a sound.
if the procedure is used for a range of comparison frequencies (to invesitigate frequency depndence of loudness) an EQUAL-LOUDNESS CONTOUR is produced
loudness scaling
participants are asked to assign numbers to sounds at different intensities
like other sensory modalities, loudness does NOT increase..
linearly with intensity
duplex theory
ITD & ILD
