Term
| A microphone is a ___ which changes one form of energy to another |
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Definition
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Term
-The microphone should change the acoustic waveform on the input to an exact replica in ___ form
-Sensitivity of the microphone is the ratio of the size of the output ___ compared to the input ___ |
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Definition
| electrical; voltage; pressure |
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Term
| What kind of mic is in a hearing aid? |
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Definition
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Term
Electret Mics:
-___: sound waves go in here
-____: very flexible plate with metallized surface. It moves up and down with pressure variations
-____ ___: separates diaphragm from backplate
-____: thin, teflon coating on the backplate with permanent charge
-___: rigid metal plate |
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Definition
| Inlet; Diaphragm; Air path; Electret; Backplate |
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Term
| Determines the frequencies of the energy that are transduced |
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Definition
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Term
-Frequency response is most often ___
-Can include: ___ cut. Acoustic resonance of __ dB somewhere between 4 to 10 k Hz (the shorter the inlet port, the higher is the resonant peak) |
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Definition
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Term
Mic imperfections:
-Random ___ noise
-____
-Internal ___
-___ noise |
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Definition
| electrical; Vibrations; feedback; Wind |
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Term
| These kind of mics suppress noise coming from the back |
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Definition
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Term
| These kind of mics pick up sounds from all 360 degrees |
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Definition
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Term
| These kind of mics switch between fixed points based on the location of the signal, usually speech, and the noise |
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Definition
| Adaptive directional microphones |
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Term
| Make the small electrical signal into a larger one |
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Definition
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Term
The 3 things amplifiers do:
-They can make the voltage larger without affecting the ___
-They can make the current larger without affecting the ___
-They can make the current ___ voltage larger |
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Definition
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Term
| Amplifiers take the power from the ___ and moves it to the amplifier output based on the ___ signal |
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Definition
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Term
| allow the analog amplifier to control a current by a smaller current or voltage |
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Definition
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Term
| Amplifiers are made up of several transistors and resistors soldered together on a circuit board into an ___ ___ |
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Definition
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Term
The IC also has:
-____: allows the current to flow one way, but not the other and sense the size of signals
-____: are used to make filters and they can be very small and fit into the IC, but if they can’t they exist on their own |
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Definition
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Term
| ____ ___ have electrical connections printed on them and can be made of fiberglass or plastic |
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Definition
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Term
| Circuit boards provide ___ between discrete components and assist in the ___ of hearing aids |
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Definition
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Term
-In a perfect world, amplifiers would not generate ___ ___ or ___ the signal when it gets too large to handle
-When amplifiers are near maximum output and the input signal or gain is increased, then the signal will distort through a process called ___ ___ which is the tops of signals being cut off making it no longer a sine wave |
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Definition
internal noise; distort; peak clipping
[image] |
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Term
-When peak clipping occurs, it creates ____ ___ which are frequency components at the output of the signal that were not there at the input
-The entire process is called ___ ___ which degrades the quality of speech and other signals and decreases speech intelligibility |
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Definition
| distortion products; harmonic distortion |
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Term
-Analog hearing aids typically had several amplifiers in a ___ with the last amplifier in the sequence using most of the ___ current
-Digital hearing aids use a _____ prior to the analog-to-digital computer with an output amplifier later in the process for the greatest power following the digital-to-analog ___ |
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Definition
| chain; battery; pre-amplifier; converter |
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Term
-Compression amplifiers change the amplification when the ___ level changes
-A compressor is nothing more than an amplifier that turns down its own ___ as the input to (or the output from) the amplifier increase |
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Definition
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Term
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Definition
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Term
Receivers-Operation Magnetic forces
-Current passes through a ___ that surrounds a piece of metal (armature)
-The electrical current ___ back in forth in direction
-The armature is alternately ___ and ___ by two permanent magnets
-The free end of the armature is attached to the ___
-The diaphragm also vibrates back and forth and that produces the ___ |
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Definition
| coil; alternates; repelled; attracted; diaphragm; sound |
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Term
Receivers and Frequency Response:
-Varies based on ___ of hearing aid
-BTE with 3 inches of tubing
*High acoustic ___ at the port compared to air in the tube
*Tube ____ at one end and ___ at the other
*Tube has resonances at ___, ___, and ___ k Hz
-ITE, ITC, or RITE
*Resonances at ____-____ and ___ k Hz |
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Definition
type; output; open; closed; 1, 3, and 5; 2.2-3 and 5
[image] |
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Term
| It is a small coil of wire that produces a voltage when an alternating magnetic field flows through it |
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Definition
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Term
Telecoil:
-___ and other devices have a magnetic field (actually a byproduct) surrounding them that has the same waveform as the signal
-Not all hearing aids have telecoils, but most high powered ____ do
-Old: ___ switch
-New: ___ program |
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Definition
| Telephones; BTEs; M-T-O; Telephone |
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Term
Label this picture:
[image] |
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Definition
| 1. Microphone. 2. Compressor. 3. High pass or low cut filter. 4. Variable gain amplifier. 5. Peak clipper. 6. Band pass filter. 7. Low pass or high cut filter. 8. Attenuator |
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Term
Label the components of this microphone from top left to bottom right:
[image] |
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Definition
| inlet port, diaphram, air path, backplate, and electret[image] |
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