Glossary of Psychoacoustics for Audiologists
Created by josyg
- What is a psychometric function?
- a graph indicating percent correct as a function of stimulus being changed
from this graph you can get % level for threshold that you want
- The property of the ear to sum signal energy over time is ?
- Temporal Integration
- Measuring the limits of temporal sensitivity is done with what type of procedures?
- Gap detection procedures:
compare 2 stim. one with temporal gap &one with no gap.
vary the gap duration to find the smallest detectable gap
- Define masking
- the shift (change) in the threshold of one sound due to the presence of another interfering sound.
-how one or more sounds interfere with the perceptio of the sound you want to listen to
- If the sound you want to hear is made less audible due to the presence of another sound we say .....
- the signal is being masked
- Why do we measure masking?
- It is an effective means for studying frequency analysis
- What is frequency analysis?
- the ability of the ear to resolve the individual sinusoidal components of a complex sound.
- When measuring masking what is the 1st thing we need to know abou the audibility of the signal?
- How well the listener can hear the signal when noise is not present = quiet threshold
- High frequency maskers are effective only over?
- relatively narrow frequency range in the vicinity of the masker frequency
- Low frequency maskers are effective over...
- a wide range of frequencies
- Masking Patterns
Strongest masking occurs in the vicinity of ___ ____.
Masking increases as ____ of masker is raised.
Greatest masking occurs for tones____ than masker freq very little masking _____
- Masker Frequency
Higher (upward spread of masking)
- What frequencies serve as best maskers?
- frequencies near the signal frequency
- The relative difference ratio is called?
- The Weber Fraction
- What are difference limens (DL) or JNDs?
- Term used to describe sensitivity to changes in:
smallest change in one of these parameters that can be detected
- What is "dynamic range"
- The useable range of hearing.
- the difference between the threshold of discomfort and
- threshold of hearing
- Speech intelligibility as a function of SNR in anechoic &reverberant environment, performance is _____ in an AN environment when speech an noise are _____.
Performance improves with ___SNR in the RV environment
- better ...... separated
Signal is significantly > in the anechoic than in reverberent environments
- Signals are generally detected more easily in ___ conditions than ___ or ____
- If we measure threshold for a tone in noise in both ears (same S&N) then remove the signal from one ear what happens?
- the threshold will improve
- This improvement in threshold when the signal is removed is called
- Masking level difference or release from masking
- JNDs tend to (increase/decrease) as SL increases up to about __dB then slight (increase/decrease) up to 80dB?
decrease or flat
- Puretones cannot be localized or lateralized at ___ frequencies based on ITD
can localize/lateralize with high frequency noise
- high frequency
it is believed that listeners obtain informatio from the envelop of the stimulus not the microstructure
- When localization is measured IA time and intensity differences can't be ___ ___. What is a measure that allows us to control these differences?
- separated out
-can control these differences using earphones
- signals are turned on & off
- subject often perceives as a movement of image inside head
- What is echo threshold?
- the delay at which fusion first breaks down & 2 separate sounds are heard
- Precedence requires sounds with ___?
- sharp transients
- The biggest errors in localization judgment are from what azimuth?
- Behind the head
- Interaural intensity differences IIDs result from what 2 aspects of sound?
- Proximity to the sound source (source is closer to 1 ear than the other)
head shadow effect (major contributor)
- Why does the head shadow effect produce big IIDs?
- If the wavelength of the stimulus is equal or < the size of head, get a shadow
the higher the frequency the shorter the wavelenght --> the greater the sound shadow
- Interaural Time differences (ITDs) occur at all frequencies but at high frequencies (> 1500Hz) they...
- do not provide good cues for localizing
at high frequ, time differences are confusing to the ear .. they happen too quickly
- The largest interaural time difference occurs at what azimuth?
- 90 degrees
- The two basic cues for localization are?
- Interaural time differences (ITD)
Interaural Intensity Differences
- What are heterophasic stimuli?
- uncorrelated stimuli presented to the 2 ears
- Monotic or monaural stimuli ?
- stimulus presented to only one ear
- Dichotic stimuli?
- Different stimulus presented to each ear
- Diotic /homophasic stimuli?
- same stimuli to both ears
- ITDs are determined by
- the difference in the distance to each ear from the source
- What does the Cocktail Party effect refer to ?
- our ability to follow what one person is saying when one or more people are talking at the same time.
we are able to use binaural cues... binaural unmasking
- Can we localize with only one ear?
- Pinna cues or monaural spectral cues at high frequencies introduced by the pinna are important for the perception of elevation, front to back distinctions and monaural localization
Low freq cues associated with vertical localization
- What is MAA
- Minimum audible angle = smallest angular separation (in degrees) between 2 loudspeakers that a listener can just detect
- What is the Precedent Effect?
- The law of the 1st wavefront
- information about the sound source location is contained in the 1st sound wave reaching the ears, even though in all reverberant environments there is more than one sound wave reaching the ears
- Sounds are louder when we listen with 2 ears why?
- binaural summation
- What is scaling?
- A direct method where the listener is asked directly about the stimulus.
- listener establishes a relationship between a standard & comparison stimulus
-listener specifies a perceptual continum corresponding to a physical continuum.
- 4 different measurement scales?
- What is ratio estimation?
- Subject gives their subjective magnitude of a comparison stimulus as a ratio of the standard ex.
1/2 as loud or 2 times as loud
- What is ratio production?
- Subject adjusts comparison to sound like a particular fraction of the standard
- What is Magnitude Estimation?
- subject assigns numbers to a stimulus to describe the magnitude ex.
on a scale of 1-100 judge loudness of different sounds
- What is magnitude production?
- subject given numbers and adjusts the stimulus to have a particular loudness ex.
50% , 80%
- What is cross modality matching
- express the perceived magnitude estimation and production in terms of a different sensory modality like a line
- What is psychoacoustics?
- a branch of psychophysics concerned with the perception of sound in relation to the physical stimulus
- 2 general approaches to studying the relationship between psychological & physical aspects of a stimulus are?
- Discrimination-same or different, indirect means of determining what a subject can respond to
Scaling procedures - Ask the subject directly about the stimuli (louder or softer)
- Two general classes of methodology?
- Classical method
signal detection theory procedures
- Three classical methods ?
- Method of limits-affected by response bias, habituation
method of adjustment- listener may change criteria for response
method of constant stimuli- takes a long time
- What is
Signal Detection Theory
- The theory provides a tool to use to separate out the effects of bias and sensitivity in psychophysical measurement.
- 2 parts of signal detection theory
- Decision theory- rules that are used in making the decision of signal present or not
Distribution Theory - ROC analysis
- Assumptions of Signal Det Theory?
- There is always some noise present- internal/external
all stimulation is measurable along a continuum, is the SN or N
Decisions are based on both sensitivity & response bias
- 4 possible outcomes of signal detection are
- hit, miss, correct rejection, false alarm
- The effect of frequency on the human ear has a ____ basis
- logarithmic basis
- the 12 tone musical scale is an example which evolved due to the way tones are ?
Going 12 notes higher (an octave) is the same as doubling the frequency
- Raw frequency resolution of the ear is best judged in terms of ____ or in ____ which is ____ of a ______
1/100 of a semitone
- Research has shown that infants can discriminate among vowel in their native language by what age?
Consonants by what age?
- 6 mos
- What is temporal integration
- the ability of the ear to sum energy over time
the ear is not a constant energy detector for sounds
- The ear integrates energy over time up to about
- 500 msec
further increases in duration ar not associated with decrease in threshold
- typical temporal cues occur how?
-in the presence of reverberation
-between signals of different intensity & frequency
- When the frequency of the lead & trail are the same GDD is
- comparable across age groups
- When the frequency of the lead & trail differ the GDD
- varies with age
-young group GDD increases a little larger freq difference especially when trail is below lead
For middle age
- GDD increases in the same way but more
-The older group shows the largest effect of lead/trail freq difference on GDD and greater variability overall
- There is a critical band of frequencies around a signal that we need in order to ?
- mask a signal most efficiently
- Once the critical band is reached if we make the masker wider ...
- it will not provide any additional masking
- The filter in the ear referred to as critical band implies
- that the filter in the ear only allows certain frequencies to pass through
- Masking patterns are sometimes called
- Masking audiograms
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