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38 Cards in this Set

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psychophysics vs psychoacoustics

psychophysics: how we perceive physical stimulus


psychoacoustics: how we perceive sound

threshold

stimulus that produces an arbitrary, but defined, level of performance



Method of constant stimuli

randomly present different intensity levels of stimuli, listener responds to stimuli, record answers


not sequential; random


Pros: easy to administer, provide precise estimate of threshold


cons: need to know threshold in advance, lots of trials, time consuming

method of limits

adaptive, start with level listener can hear, present levels lower and lower until cannot hear


sometimes start where easily heard, sometimes where can't hear, sequential


Pros: efficient because can 'focus' stimuli near threshold, giving threshold fewer trials, don't need threshold to start


cons: 'false' responses cause errors in estimating threshold


bias: anticipation and habituation

method of adjustment

subject controls stimulus instead of investigator, increase dial until hear sound, then decrease until don't hear, sequential


more intensity for high frequency


pros: easy, intuitive appeal


cons: results can be unreliable


bias: hard to tell if you heard sound at threshold

uses sequential ascending and descending presentations of stimuli

method of limits and method of adjustment

3 methods of threshold

method of adjustment, method of limits, method of constant stimuli

Response Bias

listerer's tendency to say 'yes I heard that'


anticipation: anticipating sound, hitting button early


habituation: stopped hearing sound, don't realize, keep pushing button


hard to tell if you heard sound at threshold

catch trials

present trial with no sound, does person say they hear it


pros: simple, provides info about bias, provides info regarding how reliable the threshold is


cons: doesn't provide way to adjust threshold to correct for bias

receiver operating character analysis

assumes when you are close to the threshold, sometimes no sound sound like something


assumes that the person's threshold is influenced by both sensitivity and bias


pros: complete and bias-free measure of sensitivity


cons: time consuming

ROC Curve


Conservative vs. liberal

conservative: only hit button if you are 100% positive= low hit rate, low false alarm


liberal: respond even if you think you heard something = high hit rate, high false alarm

hit


correct rejection


miss


false alarm

hit: signal, response


correct rejection: no signal, no response


miss: signal, no response


false alarm: no signal, response

2 alternative forced choice (2 AFC)

play 2 test intervals, one with sound one with no sound


listener picks interval where sound was present, bias applies equally to both intervals and cancels out


pros: bias-free, combines with other methods


cons: technical details

masking

interference in perception of one stimulus due to the presentation of another stimulus. any noise that interferes with your ability to hear a signal.



signal or probe

stimulus you are trying to hear



masker

sound that is doing the masking


the other sound

quiet threshold

absolute threshold for signal, probe presented alone

masked threshold

threshold for signal, probe when presented with masker

amount of masking

difference between quiet threshold and masked threshold


masking always increases threshold`

true simultaneous

signal presented midway through masker

forward fringe

signal and masker start at same time , masker continues

backward fringe

masker starts first, ends at the same time

forward masking

period between masker then signal


signal increase, masker will be less, not 1:1


level of auditory nerve: peripheral process


dichotic doesn't work



backward masking

signal break then masker


causes not well understood


more effective than forward


monotic: same ear


dichotic: different ears


level of brainstem: central process


Relative Effectiveness of different types of masking

signal and masker far apart, not much change in threshold


signal and masker get closer, threshold goes up (hear more)


you want higher threshold


1. forward fringe


2. backward fringe


3. true sim.

tone on tone simultaneous masking

more difficult when masker is closer in frequency


lower frequency, not much masking


signal higher in frequency than masker, more intensity

pure tone maskers and narrow band noises

may have narrow spectrums and will produce narrow regions of masking


similiar to tone-on-tone


higher frequencies masker to higher extent

broadband noise

lots of frequencies across spectrum, masking for broad range of frequencies

amount of masking depends on

timing of masker


intensity


frequency


bandwidth



Temporal Resolution

ability to follow rapid changes in a sound


signal longer, easier to hear, not as intense



auditory nerve response to rapid change

fibers do not fire at instant sound begins/ ends


fibers do not fire on every cycle of sound


spontaneous activity occurs when no sound is present


auditory nerve response does not follow change with perfect precision (exactly what signal is doing)



sensitivity-resolution tradeoff

extend integration time to improve sensitivity (ability to hear), you lose resolution (following rapid changes)

spectral splatter

over time, want longer period of time


one frequency

measure temporal resolution

duration discrimination: duration between 2 signals, very acute, threshold: shortest duration difference


gap detection: increase frequency, gap narrower, threshold: narrowest gap


amplitude modulation detection: how much do you have to modulate amplitude for listener to tell its been modified

modulation depth

lowest modulation depth that we can detect a change

AM detection as a function of modulation rate

temporal modulation transfer funtion (TMTF)


higher frequencies, big changes in depth


good at AM detection up to 50-60 Hz mod. rate


50-60 Hz= 17-20 ms/cycle of modulation



multiple integrators

good temporal resolution because neural fibers have different integration times


AN fibers receiving info from inner HC and going to brain


200 ms: good for detecting sound


500 ms: good for detecting gap

multiple looks

good temporal resolution because we use memory to integrate sound energy