Bilateral Amplification Flashcards
What is binaural loudness summation?
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
What is the result of binaural loudness summation?
Since patient’s perceive greater loudness with bilateral devices, less gain is needed to reach a comfortable listening level
What is binaural squelch?
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
Does binaural squelch lead to better intelligibility in noise?
Yes
How much SNR dB improvement does binaural squelch offer?
2-3 dB
What is the unaided ear affect?
About 25-33% of individuals with symmetric hearing loss and one hearing aid will experience reduced WRS scores
Pure tones will not change
What is happening to create the unaided ear affect?
The brain pays more attention to the dominant ear overtime and ignores the ear with the weaker signal
What is binaural interference?
Reduced intelligibility in noise with bilateral amplification
What causes binaural interference?
Age-related atrophy of the corpus callosum
Two halves are not working together and it is hard to retrieve information
What test can be used to assess someone with binaural interference?
Dichotic digit test
What can someone do if they experience binaural interference?
Can be fit bilaterally
Use a remote mic or remove one hearing aid in noise
What are some reasons someone might only want one hearing aid?
Cost
Occlusion effect
Convenience of use
What are some things to think about if they proceed with one hearing aid?
Which ear will supply the greatest speech intelligibility?
Handedness?
Dexterity?
Is the patient routinely in a situation where the speaker is on one side?
What are some things to consider when selecting a style of hearing aid?
Fitting range
Pinna effect
Wind noise
Feedback and occlusion
Size of ear canal
Perspiration, cerumen, and humidity
What is the device fitting range?
The configuration of the hearing loss determines style options
What can impact a devices output?
Distance between the mic and the receiver
Less distance=less output
Smaller device=less output
What are realistic fitting ranges impacted by?
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
What is the pinna effect?
Naturally adds gain and provides valuable spatial awareness cues
How much does the pinna effect boost the intensity of high freq signals?
About 7 dB SPL
Is the pinna effect different for some signals depending on angles of arrival?
Yes
The pinna’s resonant cavities may attenuate lows or amplify highs
Is the pinna effect greater the deeper the mic is placed into the canal?
Yes
Is the output also affected by the proximity of the sound bore to the TM?
Yes
The output arriving to the TM increases by about 6 dB APL when the volume between the sound bore and the TM decreases
How much gain does deep mic placement and deeply fit devices provide?
13 dB SPL
What is an ingress protection rating?
Rates the devices on their protection against solids and liquids
higher=more protective
