Introduction to Hearing Sciences Exam 3 Review

Psychophysics

The study of the relationship between physical stimuli and the resulting perceptions/sensations

Psychoacoustics

The study of the physiological response to acoustical stimulation

Threshold

The smallest increment of parameter at which a person is able to detect presence of or difference in stimulus

Absolute Threshold

Lowest level of stimulation that is detectable some pre-specified portion of the time

Differential Threshold

Smallest magnitude of difference that allows a person to differentiate between two nearly identical stimuli

Thresholds are estimated and typically averaged over _____ repetitions

many

Trial

One repetition, stimulus provided, response obtained

Run/Block

Series of trials over which responses are averaged

Classical Psychophysical Methods

Method of Limits
Method of Constant Stimuli

Other Psychophysical Methods (not classical)

Adaptive/Staircase Method

Method of Limits

Property of stimulus is changed until it is barely detectable to participant
Ascending/Descending

Method of Constant Stimuli

Stimuli are presented at several fixed levels, participants respond with "yes" or "no" after each presentation

In the method of constant stimuli, up to _____ trials at each level are presented in a _____ order

100, random

In the method of constant stimuli, a _____ _____ is plotted and the threshold is estimated

psychometric function

What two values does a psychometric function compare?

Stimulus level and percent correct

Classical methods of psychophysics can lead to _____ _____

participant bias

Adaptive Psychophysical Methods

Forced-choice paradigm

Forced-Choice Paradigm

Each trial contains at least 2 intervals, where only 1 interval contains the correct response, participants choose 1 interval per trial

In a forced-choice paradigm, the threshold is estimated through a _____ _____

psychometric function

A forced-choice paradigm is much _____ than classical methods

quicker

What are the three basic physical properties of sound?

Frequency, amplitude, time

Threshold of Audibility

Smallest level of sound detectable by a person with normal hearing

Does a high threshold of audibility mean higher or lower sensitivity?

lower

Minimal Audibility Curve

Average thresholds in normally-hearing adults plotted as a function of frequency

Humans are sensitive to sounds between ___ and ___ Hz

20, 20,000

Humans are more sensitive to sounds in the _____ frequencies, especially ___-___ kHz

mid, 1, 4

Most speech cues occur between ___ and ___ Hz

500, 4000

Threshold of discomfort

100dB SPL

Threshold of Pain

125-140dB SPL

Dynamic Range of Hearing

Range between absolute threshold of audibility and threshold of discomfort/pain
0 - 140 dB SPL

Minimum Audible Pressure (MAP) Tresholds

Audibility thresholds obtained with headphones and earphones

Minimum Audible Field (MAF) Thresholds

Obtained in free field, one meter from sound source

Sensitivity improves with increased _____

duration

Temporal Integration

Ability of auditory system to detect sounds of differing durations

Weber's Law of Discrimination

A stimulus must be increased by a constant proportion of itself to be perceived as different

Weber's Law Equation

∆S/S = k

S - value of base or standard stimulus
∆S - increment of change needed for just-noticeable differentiation
k - a constant

Does weber's law apply to frequency discrimination?

Yes

Does weber's law apply to intensity discrimination?

Generally. There is a near miss as the intensity level increases.

Auditory system sensitive to ___ - ___ dB change in level across broad range of frequencies and levels

0.5, 1

Threshold for ∆I decreases slightly for pure tones as _____ increases

level

Temporal Discrimination

Interactions between duration of sound and detectability

Temporal discrimination is measured with _____ _____

gap detection

Gap detection shows sensitivity to _____ of sounds

separation

Does weber's law apply to temporal discrimination?

No

Masking

When one sound interferes with the detectability of another sound

In masking, the threshold of one sound is _____ by the presentation of another sound/masker

raised

Threshold Shift

Amount by which threshold is increased by the presence of a masker

The most efficient masker of a tonal signal would be a tone that is _____ to the signal frequency

close

Psychophysical Tuning Curve

Curves plotted to reflect effectiveness of maskers at very different frequencies for one pure tone

A psychophysical tuning curve shows the sound level needed in order for what to happen?

The masker to just barely mask the signal

Maskers with _____ frequencies than signal frequency and more efficient at masking than maskers with frequencies that are _____ than the signal

lower, higher

Bandwidth

Quantified range of frequencies in a sound

Total Power

Sum of amplitudes of all sinusoids in spectrum of noise

Spectrum Level (No)

Average noise power in a band of noise

Signal to noise ratio

Level of noise subtracted from level of signal (dB)

Broadband Noise

Noise containing a large range of frequency components

Narrowband Noise

Limited range of frequency components

Above a certain spectrum level (about 20dB), increase in spectrum level of noise results in an approximately _____ increase in _____

equal, threshold

Critical Band Theory

There is a range of frequencies that affects the detectability of a signal. Outside of this range, frequencies present in the masker do not contribute significantly to masking.

Notched-Noise Method

A way to estimate the shape of critical band.

In the notched noise method, the wider the _____ _____, the lower the _____ of a signal

spectral notch, threshold

Threshold is determined by the total amount of _____ coming through _____

power, filter

Simultaneous Masking

When signal and masker occur at the same time

Forward Masking

When masker comes on and off prior to occurrence of signal

Backward Masking

When masker comes on and off after occurrence of a signal

Forward and backward masking has the greatest effect when the interval between signal and masker is _____

short

Localization

Judgements of the direction and distance of a sound source

What are the three spacial dimensions that localization exists in?

Horizontal plane, vertical plane, distance

What are the major cues for horizontal localization?

Interaural time differences, interaural level differences

Interaural Time Differences

Sound arrives at one ear earlier than the other

What does the amount of interaural time difference depend on?

Distance of the sound source

Speed of sound is _____ across frequencies

constant

Interaural time differences is _____ for all frequencies

same

Interaural Level Differences

Intensity level of sound is greater at one ear than the other

Head sound shadow results in what?

Reduced sound level at ear opposite sound source

Interaural level differences are _____ across frequencies

different

There are larger interaural level differences at _____ frequencies

higher

Localization is more difficult in what range?

mid-frequency, 2000Hz

Is horizontal localization or vertical localization more accurate?

Horizontal

Minimal Audible Angle

Smallest angular separation between two sounds detectable by a listener

Minimal audible angle is very high at _____ frequencies

high

Minimal audible angle is worse with increased _____

distance

Duplex Theory of Localization

We would rely upon interaural time differences at low frequencies because interaural level differences are not available

Sound via _____ can more directly manipulate interaural time differences and interaural level differences independently

headphones

Lateralization

Experiments involving headphones where sound is presented with ITD or ILD imposed.

0° interaural phase difference

Fused sound perceived at midline of head

Up to 180° interaural phase difference

Fused sound located closer to ear that received tone first

More than 180° interaural phase difference

Fused sound located closer to ear receiving tone with lagging phase

360° interaural phase

Fused sound perceived at midline of head

Sound is lateralized toward the ear receiving sound with _____ intensity level

higher

Humans can effectively utilize interaural level difference cues at lower frequencies for _____ than _____

lateralization, localization

Localization

In a free field

Monotic

Stimulus presented to only one ear

Diotic

Identical stimulus presented to both ears

Dichotic

Different stimuli presented to two ears

Sm

Signal presented to one ear

Mm

Masker presented to only one ear

So

Signal differences presented binaurally with no interaural differences

Mo

Masker presented binaurally with no interaural differences

Sπ

Signal presented to both ears, 180° out of phase