Binaural hearing

Question 1

are hearing thresholds perfectly symmetrical?

Answer 1

rarely

Question 2

Is research conducted binaurally?

Answer 2

no, monaurally

Question 3

binaural fusion

Answer 3

separate signals from each ear are perceived as one fused auditory image
brain puts info from both ears and hear it as one single image

Question 4

binaural summation

Answer 4

The ability to improve perceptual performance on a psychoacoustic task when both ears receive input
about 3dB
effect is hearing sounds louder

Question 5

Imagine you have a patient with symmetrical hearing loss (same threshold at both ears). They come to your office wearing one hearing aid because the second one is broken. They tell you that the overall volume is comfortable with the one hearing aid in. You fix their other hearing aid and set it so both hearing aids have the same settings. Will the set of hearing aids still be comfortable or will adjustments need to be made?

Answer 5

yes they would because it would be too loud (as summed input from both sides making it sound louder) (summation)

Question 6

If you had a patient with symmetrical hearing thresholds and you fit them with hearing aids providing the exact same amount of amplification, would there be a difference in loudness perception if the patient wore only one or wore both of the hearing aids? Explain your answer.

Answer 6

Yes, it would be almost twice as loud with both of the hearing aids in, due to binaural loudness summation

Question 7

What would happen if you were testing hearing and discovered you had sound going into both headphones? Would this affect hearing thresholds?

Answer 7

yes because their thresholds would show as lower
improves thresholds in both noise and not

Question 8

What plane is being referenced with the term “azimuth”? With the term “elevation”?

Answer 8

Azimuth = horizontal plane
Elevation = vertical plane

Question 9

Describe the 0o azimuth, relative to a person’s head

Answer 9

right in front

Question 10

Describe the 90o azimuth, relative to a person’s head

Answer 10

directly to the right

Question 11

Describe the 180o azimuth, relative to a person’s head

Answer 11

directly behind

Question 12

Describe the 270o azimuth, relative to a person’s head

Answer 12

directly to the left

Question 13

Describe the 0o medial, relative to a person’s head

Answer 13

directly in front

Question 14

Describe the 90o medial, relative to a person’s head

Answer 14

directly above

Question 15

Describe the 180o medial, relative to a person’s head

Answer 15

directly behind

Question 16

How do interaural level differences (ILD) arise? Draw a schematic. Is this a low frequency or a high frequency cue for sound source localization?

Answer 16

ILD’s arise because of the head shadow. Sound is reflected off of the head and casts an acoustic “shadow” on the opposite side. The sound level is greater on the side where the sound originated. This is a high frequency (above 1500 Hz) cue for sound source localization. See separate schematic.

Question 17

How do interaural timing differences (ITD) arise? Draw a schematic. Is this a low frequency or a high frequency cue for sound source localization?

Answer 17

ITD’s arise because a sound arrives to one ear sooner than it arrives to the other. This is a low frequency phenomenon (below 1500 Hz). See separate schematic

Question 18

Where is ILD greatest?

Answer 18

90 azimuth

Question 19

where is ILD smallest?

Answer 19

0 azimuth because it is directly in front and going to both ears the same

Question 20

does the monaural system do much with phase differences?

Answer 20

no, the binaural system

Question 21

what does head related transfer function (HRTF) do?

Answer 21

describes the spectral characteristics of sound as measured at the tympanic membrane when the sound source originates in 3D space

Question 22

Is HRTF a monaural or a binaural sound localization cue?

Answer 22

TF is a monaural sound localization cue in the vertical plane

Question 23

Is this cue (HRTF) effective for narrowband or broadband signals? Why?

Answer 23

effective for broadband signals because
doesn’t work for tones (ex: fire alarm and not knowing which one is going off without seeing it)
pinna reconstruction can take time how to learn how to localize because the sound would bounce off of it

Question 24

What is the cocktail party effect?

Answer 24

Ability to attend to or focus one’s attention on a particular stimulus in the presence of other stimuli (target vs. competition or noise)

Question 25

Define signal to noise ratio (SNR)

Answer 25

the relationship between the desired target (signal) and noise (anything that is not the target)

Question 26

what is SNR equation

Answer 26

SNR = signal dB level - noise dB level

Question 27

signal is 40 dB SPL and noise is 45 dB SPL

Answer 27

-5 dB SPL

Question 28

signal is 40 dB SPL and noise is 40 dB SPL

Answer 28

0 dB SPL

Question 29

signal is 40 dB SPL and noise is 35 dB SPL

Answer 29

5 dB SPL

Question 30

What acoustic advantage exists for a person with two ears? What is the term for this?

Answer 30

The “better ear effect”- physically if the target and the noise are separated, there will be one ear with a better SNR.
Having two ears provides the ability to reduce perceptual and acoustic effects of noise

Question 31

What is binaural squelch?

Answer 31

the auditory systems uses BOTH ears, even the one with the poorer SNR, to provide an advantage in noise.

Question 32

the ear takes advantage of correlation between the ears to enhance perception

Answer 32

the masking level difference (binaural unmasking)

Question 33

a mechanism that suppresses echoes due to reverberation

Answer 33

echo suppression

Question 34

better SNR at ear closer to the signal

Answer 34

better ear advantage

Question 35

Differentiate between diotic and dichotic presentation of a stimulus.

Answer 35

Diotic = same exact stimulus (in terms of amplitude, frequency, and onset time and phase)
Dichotic= differs in at least one dimension or could even be a different word

Question 36

Describe the binaural masking level difference experiment. What acoustic cue does the binaural auditory system take advantage of to improve detection of a signal?

Answer 36

ear (using both ears) can reduce the effects of noise to enhance perception of signal (dichotic condition)
In the BMLD experiment, two conditions are compared. In both conditions, a tone is presented in the presence of white noise. In the diotic condition, the tones are in-phase and have the same frequency and amplitude. In the dichotic condition, the tones are 180 degrees out of phase, but have the same frequency and amplitude. This mimics ITD’s and the spatial separation of a tone and noise. Thresholds are BETTER in the dichotic condition.

Question 37

Describe how the precedence effect and echo suppression account for echoes and reverberations.

Answer 37

The precedence effect says that the sound source localization is based on the first copy of the sound to arrive to the auditory system.

Echo suppression- multiple copies of the sound are suppressed

The auditory system processes one auditory image.

Question 38

If you had a patient who had a sudden hearing loss in one ear, what perceptual changes might they notice?

Answer 38

trouble localizing
more trouble hearing in noise (loose squelch)
different thresholds (higher)
harder to hear someone’s voice
harder time hearing soft sounds - have a cocktail problem
more trouble in an echo room
threshold of echo suppression is less (binaural system is what suppresses them)
less loudness perception