Hearing Aids Flashcards
What do hearing aids do?
- They aid hearing
- Make speech audible
- Greater audibility of environmental sounds
- Restores loudness experience
- Improvement in speech clarity in quiet and sometimes noisy environments
What can’t hearing aids do?
- They cannot restore natural organic hearing
- Even though they make speech audible, it doesn’t always make it understandable
What is history of hearing aids?
- Cuffing our ears - oldest form of hearing aids, can add 12db of gain to 1kHz
- Electrical tabletop hearing aids introduced in 1800s
- Body worn hearing aids in 1900s
- BTE emerged in 1960-1970s
What makes up hearing aid electroacoustics?
- Gain
- Output
- Maximum Power Output (MPO)
- Distortion
- Equivalent Noise
Define gain
Gain is the amount of amplification that was added to the input level (dB)
Define output
Output is the total amount of sound that a hearing aid produces for a given signal
- Gain + Input = Output
Define MPO
The maximum possible output of a HA
Define distortion
The number of unwanted signals or noise produced by hearing aid
Define equivalent noise
The amount of noise produced when no input signal is present
What makes up the hearing aid components?
- Microphone
- Amplifier
- Receiver
- Batteries
Define microphone
It’s a device that detects and transfers acoustic energy into an electrical signal
Define omni-directional microphone
It picks up sound from all directions
Define directional microphones
Where many hearing aids have two microphones used to increase directionality
What is a polar plot?
It plots sensitivity of microphone 360 degrees around patients head
What are microphones susceptible to?
- Moisture, Water
- Vibrations
- Wind Noise
- Internal Electrical Noise
What are the traditional methods of amplifying sounds that’s no longer used?
- Conventional Amplifier
2. Programmable Amplifier
Modern hearing aid technology uses?
Digital sound processors
What does a modern hearing aid technology require?
An analog-to-digital converter
Why does modern hearing aid technology require an analog-to-digital converter?
Because a microphone turns acoustic energy into analog electric signal
For modern hearing aid technology, once the signal is digitized, what occurs next?
The digital signal processor (DSP) assigns components of sound to channels
What does modern hearing aid have?
Multiple channels
What can be applied to each channel as needed by the hearing loss?
Gain
The more channels, the ..
Better resolution
What are the hearing aid output?
Peak clipping & Compression
Define peak clipping
It cuts all sound output above certain level
What falls under peak clipping?
- Amplification is linear until sound reaches certain limit
- Often adds distortion and sounds unnatural
Define compression
It creates non-linear gain profile
What falls under compression?
- Allows more sounds to fit into the same dynamic range
- Cutoff level set to patient’s comfort level
- Sounds more natural than peak clipping
What is a receiver?
Takes amplified electrical signal and converts back into an acoustic signal
What is another name for a receiver?
A speaker
What characteristics makes up a receiver?
- Come in varied sizes depending on how much amplification is needed for the patients hearing loss
- Are easily damaged or blocked by cerumen
- The larger the receiver- the larger out capable output level
- Vulnerable to moisture damage
What are the types of hearing aid batteries?
- Disposable
2. Rechargeable
What are modern disposable batteries?
Zinc-Air