CD 351 Exam 3

For students at the University of Alabama taking Hearing Science

Psychophysics

How we perceive a physical stimulus

Psychoacoustics

How we perceive sound

The McGurk effect

A psychoacoustical phenomenon in which what we see clashes with what we hear

Scaling

The ordering of stimuli along some type of space

Threshold

The lowest sound that we can perceive

T/F: There is no absolute threshold

True

Method of Constant Stimuli

A phsycophysical method in which several stimulus levels are presented and each time the stimulus is heard is recorded.

Pros of Method of Constant Stimuli

• Easy to administer

• Can provide a precise estimate of the threshold if the step sizes are small

Cons of the Method of Constant Stimuli

• You must know the approximate threshold of the listener in advance

• Time may be wasted

Method of Limits

A physcophysical method that starts where the tester thinks the listener will hear. The decibels will lower until the listener can no longer hear, and the process is repeated several times.

Pros of the Method of Limits

• Efficient because we can focus the stimulation around the known threshold

Cons of the Method of Limits

• False representation may cause errors in the estimation threshold

• The listener may miss the true threshold if the step size is too big

Transition Point

The mean between intensities where a patient could and could not hear the stimulus.

Mean threshold value

The mean of all transition points

Modification of Limits

A shorter version of the method of limits that is typically done in a clinic

Method of Adjustment

A psychophysical method in which the listener turns a dial back and forth until they cannot hear the stimulus anymore several times.

Békésy Tracking

When the intensity increases as the subject pushes a button and the intensity decreases as the subject releases the button. The midpoints correspond to the 50% point.

Pros of the Method of Adjustment

• Offers the patient control over the situation

• Easy and simple

Cons of the Method of Adjustment

• The results can be unreliable

• Does not have the highest confidence in accuracy

Response Bias

When the patient will only respond to a stimulus under certain conditions

What are the two reasons a listener may answer incorrectly on the Method of Limits test?

• Anticipation (they’re expecting the stimulation)

• Habituation (they’re used to answering for the stimulus)

Why would a listener answer incorrectly on the Method of Adjustment test?

Perseveration in the response

Catch Trial

When a tester does not play a stimulus and watches to see if the listener responds.

Pros of a Catch Trial

• Simple

• Provides information about bias

• Provides some information about how reliable the threshold is

Cons of a Catch Trial

• Does not provide a way to “adjust” the threshold to correct for any biases

Receiver Operating Characteristic (ROC) Analysis

The assumption that when you are close to a threshold, sometimes “no sound” sounds like something. Used to train military personnel for radars.

Hit

When there is a stimulus present and it is heard

Miss

When there is a stimulus but it is not heard

False Alarm

When there is no stimulus present but something is heard

Correct Rejection

When there is no stimulus but nothing is heard

What are the optimal answers for a ROC trial?

Hit and correct rejection

ROC curve

A response bias test in which the stimulus changes, but the way that a listener responds to it changes

Conservative Listener

“Only indicate you heard something if you are 100% certain.”

Liberal Listener

“Indicate that you heard something when you feel like it’s correct.”

Two-Alternative Forced Choice (2FAC)

A response bias test that involves two intervals: one without sound and one with sound. The listener is asked to pick which trial had sound.

The most common method for studying hearing sensitivity is ___.

A mix of 2FAC and adaptive method

Masking

A change in the threshold for a stimulus caused by the presentation of another stimulus

Quiet Threshold

The absolute threshold for the signal presented alone

Masked Threshold

The absolute threshold for signal when presented with a masker

Amount of Masking

The difference between a quiet threshold and a masked threshold

Simultaneous Masking

When the masker and signal overlap in time

Simultaneous masking is a ___ correspondence ratio

1:1

True Simultaneous Masking

When the signal is presented in the middle of the masker

Forward Fringe Masking

When the signal and the masker are on at the same time, but the signal stops first

Backward Fringe Masking

When the masker comes on first, followed by the signal. They both stop at the same time.

Simultaneous Noise Masking

When the signal is the tone and the masker is the noise

The higher the noise on a broadband graph, the ___ the frequency is affected.

more

The curve on a broadband noise making graph is the ___

Threshold of audibility curve

T/F: Frequency does make a difference on broadband noise making

False

Parameter

The spectrum level of noise

Simultaneous Narrowband Masking

When the signal is higher in frequency, the Amount of Making is generally greater because more frequencies are engaged on the basilar membrane.

As the signal gets closer to the masker in time, the masker becomes more ___.

Effective

The masker is more effective as the threshold goes ___.

Up

There is a decrease in the threshold as a signal gets ___ from the masker in time

farther away

When the masker and the signal are ___ in frequency, the masker is more effective

closer together

Tone-on-tone masking

When the masker is fixed in frequency and sensation level. The signal frequency and level varies

Beats

When the signal and the masker are very close in frequency (usually < 10 Hz)

T/F: At a high level, the high frequency masker will not mask a low level frequency well

True

T/F: At a low level, the low frequency masker will not work better than a high level, high frequency masker.

False

Combination Tones

A phenomenon where two loud tones are sounded together and a third tone is heard that is not actually present in audible sounds.