Bilateral Amplification

Question 1

What is binaural loudness summation?

Answer 1

Action potentials in the brainstem increase loudness when two ears receive auditory input signals
At threshold, the increase is only 2-3 dB
At suprathreshold, the increase is 6-8 dB

Question 2

What is the result of binaural loudness summation?

Answer 2

Since patient’s perceive greater loudness with bilateral devices, less gain is needed to reach a comfortable listening level

Question 3

What is binaural squelch?

Answer 3

The nuclei of the brainstem processes timing, amp, and spectral cue differences between the two ears
Attempts to cancel the noise perceived by one ear using the signal signal received from the other

Question 4

Does binaural squelch lead to better intelligibility in noise?

Answer 4

Yes

Question 5

How much SNR dB improvement does binaural squelch offer?

Answer 5

2-3 dB

Question 6

What is the unaided ear affect?

Answer 6

About 25-33% of individuals with symmetric hearing loss and one hearing aid will experience reduced WRS scores
Pure tones will not change

Question 7

What is happening to create the unaided ear affect?

Answer 7

The brain pays more attention to the dominant ear overtime and ignores the ear with the weaker signal

Question 8

What is binaural interference?

Answer 8

Reduced intelligibility in noise with bilateral amplification

Question 9

What causes binaural interference?

Answer 9

Age-related atrophy of the corpus callosum
Two halves are not working together and it is hard to retrieve information

Question 10

What test can be used to assess someone with binaural interference?

Answer 10

Dichotic digit test

Question 11

What can someone do if they experience binaural interference?

Answer 11

Can be fit bilaterally
Use a remote mic or remove one hearing aid in noise

Question 12

What are some reasons someone might only want one hearing aid?

Answer 12

Cost
Occlusion effect
Convenience of use

Question 13

What are some things to think about if they proceed with one hearing aid?

Answer 13

Which ear will supply the greatest speech intelligibility?
Handedness?
Dexterity?
Is the patient routinely in a situation where the speaker is on one side?

Question 14

What are some things to consider when selecting a style of hearing aid?

Answer 14

Fitting range
Pinna effect
Wind noise
Feedback and occlusion
Size of ear canal
Perspiration, cerumen, and humidity

Question 15

What is the device fitting range?

Answer 15

The configuration of the hearing loss determines style options

Question 16

What can impact a devices output?

Answer 16

Distance between the mic and the receiver
Less distance=less output
Smaller device=less output

Question 17

What are realistic fitting ranges impacted by?

Answer 17

Proximity of mic to receiver
Size of receiver (larger receivers produce greater output)
Physical properties of sound bore (length and diameter)
Vent size
Mic location
Proximity to TM

Question 18

What is the pinna effect?

Answer 18

Naturally adds gain and provides valuable spatial awareness cues

Question 19

How much does the pinna effect boost the intensity of high freq signals?

Answer 19

About 7 dB SPL

Question 20

Is the pinna effect different for some signals depending on angles of arrival?

Answer 20

Yes
The pinna’s resonant cavities may attenuate lows or amplify highs

Question 21

Is the pinna effect greater the deeper the mic is placed into the canal?

Answer 21

Yes

Question 22

Is the output also affected by the proximity of the sound bore to the TM?

Answer 22

Yes
The output arriving to the TM increases by about 6 dB APL when the volume between the sound bore and the TM decreases

Question 23

How much gain does deep mic placement and deeply fit devices provide?

Answer 23

13 dB SPL

Question 24

What is an ingress protection rating?

Answer 24

Rates the devices on their protection against solids and liquids
higher=more protective