Gain

Question 1

What is lybargers half gain rule?

Answer 1

This is calculated at each frequency.
1/2 the ac threshold (+ 1/2 abg) + 10dB reserve.

Question 2

What is linear amplification?

Answer 2

Any increase in output is equal to any increase in input until the amplifier reaches saturation. Once saturation occurs it is not possible for aid to amplify any more.

Question 3

Limitations of half gain rule

Answer 3

Soft sounds too quiet
Moderate sounds good
Loud sounds too loud

Question 4

Circumstances where less than half gain is needed?

Answer 4

-Canal aids - closer to TM the 1/3 gain can be applied
- binaural fittings - summation of energy so gain can be reduced by 3-6dB
- open fittings : natural canal resonance
- asymmetrical losses: gain required by worse ear may be less than predicted by prescription
- previous user info : NHS aids use prescription that is louder so our aids will seem quieter to them

Question 5

Other prescription methods

Answer 5

• NAL
  -NAL2
  -POGO
  -BERGER
  -VAC

Question 6

Explain balanced hearing

Answer 6

Two ears will collect and deliver the signal - if one ear is doing this there will be less signal therefore less information.
Also, hearing with two ears is less effort and less cognitive effort

Question 7

Explained combined localisation

Answer 7

Binaural aids can pinpoint the sound of interest and locate direction and distance of moving source and allows us to quickly identify a speaker

Question 8

explain speech intelligibility

Answer 8

Improved speech in noise. Signal to noise ratio is increase by 2-3dB with binaural fittings. Binaural squelch is the ability to focus on signal and ignore the noise.

Question 9

ExplainLoudness summation

Answer 9

Quiet sounds heard by one ear will still be perceived, gain can be reduced by 3-6dB. There is less risk of feedback, distortion and exceeding ULLS.

Question 10

Explain preservation of hearing

Answer 10

Brain gradually loses some of its ability to process info and continued lack of stimulation occurs when the ear goes unaided. The earlier you wear binaural aids the more it minimises the risk.

Question 11

When May fitting two aids not work?

Answer 11

-Asymmetrical losses
-Retro cochlea losses (processing prob)
-Physical reasons: dexterity/abnormalities
- negative attitude: self image
- Diplacusis: pitch perceived differently between 2 ears can be enhanced by binaural fittings

Question 12

Binaural loss with monaural fitting - which ear to fit?

Answer 12

Rule of thumb: ear with threshold closest to 50dB at 1kHz
Medical probs: fit other ear
Dexterity probs: fit other ear
Audiometry: best residual hearing
Tinnitus: fit ear with greatest relief