Hearing Aids Flashcards
(64 cards)
What is the goal of a hearing aid?
amplify sounds thereby increasing the signal to the wearer: provide audibility
What a hearing aid not?
A cure for hearing loss
What is the hearing aid made up of?
mic+amplifier and complex signal processors
How many people in the UK are affected by hearing loss?
1 in 6
How many people in the UK would benefit from hearing aids?
1 in 10
What are the 2 types of HA?
Behind the ear (post-aural)
In the ear
Describe the BTE
• Worn behind pinna
• Coupled to concha via plastic tube and earmold
• Delivers sound to external auditory meatus (ear canal)
Describe the ITE
• More restricted acoustics • Aesthetics
What ate the types of ITE?
Full concha
Half concha
In the canal
Completely in the canal
How do bone conduction hearing aids work?
• Sound transmitted through mechanical vibration of cranial bones, to cochlea rather than through outer/middle ear (air conduction)
• Bypasses the outer/middle ear: for conductive losses
What are the issues of BC HA?
- Cosmesis of headband
• Headband discomfort (headaches, pressure) - Low gain, poor sound quality
What is the difference between Bone anchored and bone conduction?
Bone anchored the bone vibrator implanted directly into patient
How is a bone anchor fitted?
• Titanium screw inserted into skull
• Aidattachedtoscrew
• For patients with chronic conductive hearing loss/outer/ middle ear pathology
What are the components of hearing aids?
air conduction receiver (speaker)
Microphones- two or more to reduce background noise
Mechanical potentiometer for volume controls
Mechanical switch for program switching
Battery
Telecoil- converts electromagnetic fields to electrical energy (phones)
What is the change in a microphone
Converts sound into electrical
What is the change in a receiver?
Converts electrical back into sound
What is the process in a digital amplifier?
Sound- Voltage- Digital signal- digital processing- digital signal- Voltage- Sound
What is gain in terms of amplification?
measure of amplification applied to signal (at particular frequencies): difference between input level and output level
What is amplification set according to?
Hearing loss
What are the two types of amplification?
Linear
Non-linear
Describe Linear amplification
• Gain constant for all levels of input
• 1:1 ip/op slope
• 70 dB sound amplified same level as 40 dB sound
Describe non-linear amplification
Gain varies according to input level • <1:1 ip/op slop
When in non linear amplification commonly used?
Modern hearing aids
What does non linear amplification do?
Makes sound comfortable
Allows us to avoid overamplifying louder sounds