Hearing Aid Tech Flashcards
When CIC’s are fit with insertion being more deep into the inner bony 1/3 of the external ear canal it reduced what?
Reduces the Occlusion Effect= more venting
The CIC, if placed deep within the 1/3 of the Ear canal, being that the microphone is now deeply placed inside the canal it emphasizes what?
Higher Frequencies typically in the 2k-4K Hz range, therefore allowing for the retention of the ears ability to transmit sound within that range more efficiently.
Occurs when the input plus the gain of the HA does not exceed the SSPL90 of the HA
Headroom
What are some potential advantages of Digital Sound Processing
Lower noise and higher fidelity ( internal noise should be limited only by the quality of the mic and receiver)
Extensive processing capability (very specialized functions are possible)
Capability to load a variety of processing schemes into HA via Software
Any HA that is not a true or fully digital HA is a ___
Analog HA
What is a Hybrid Analog - Digital HA
A HA that contains a digital computer chip to control some aspect of how sound is amplified but remains in analog form
Digital components are used to control the filtering or compression characteristics
What was The Zeta Noise Blocker?
A Hybrid - Digital - Analog HA that had a digital chip implemented with ITE analog hearing aid for noise reduction in the mid 1980’s
It attempted to separate speech from noise in several frequency bands using temporal differences between speech and quasi-steady state noise
It was not a success
What is a digital programmable HA
AKA Digitally controlled Analog (DCA)
Unlike Zeta whose purpose was to perform filtering, the digital components are present for the purpose of programming the parameters of the HA such as Frequency Response, Gain, MPO and compression are set by attaching HA’s to computer instead of trimpots.
What are some potential advantages to a DCA HA
Increased flexibility and more precise fittings of parameters such as gain, MPO and Freq Response
Can be adjusted while pt wears the HA’s
Adjustments are made without having to send back to Manufacturer and can be saved on a memory chip
What are the 4 different types of digital memories used to store the HA parameter settings
RAM (Random Access Memory)
PROM (Programmable Read-Only Memory)
EPROM (Erasable Programmable Read-Only Memory)
EEPROM (Electrically Erasable Programmable Read-Only Memory)
What can a RAM Digital Memory do?
Can have data written to and read from it in any random order but requires a second backup voltage supply to store the programmed parameters. Without it when turned off or battery change all instructions are lost and have to be reprogrammed
What can a PROM Digital Memory do?
Allows the parameters to be stored only once requiring a physical change in the PROM chip to change HA performance.
What can a EPROM Digital Memory do?
Allows the programmed parameters to be changed after subjecting the digital memory to an ultra violet light in order to erase it.
What can an EEPROM Digital Memory do?
Can have data written into it, read from it and may also have new data rewritten and stored using a programming device.
What are the four categories to a successful HA fitting (pertaining to pt)
Otologic Findings
Cosmetic Concerns
Performance Criteria
Financial Considerations
Zeta Noise Blocker was:
An analog filter placed with a DSP Hearing instrument
In digital signal processing a set of mathematical steps involving multiplication,addition, and subtraction is referred to as:
Algorithm
Quantization is related to
Number of bits
The number of bits impact the:
dynamic range of the hearing instrument
Imaging occurs during the
Digital to analog conversion stage
When you cup your hand behind the ear, sound
Increases 5-8dB
A capacitor
Blocks the low frequencies and passes the high frequencies
A resistor
Restricts the flow of electrons
The function of the microphone is to
Convert acoustic energy into electrical energy
Coupling in a hearing instrument refers to connecting
One stage of an amplifier to the next
The T position on a HA switch can be used to
Amplify a telephone conversation
Couple a HA into a loop inductor system
Couple directly into the audio of a radio or TV set with a separate induction coil
Which component can change or modify the frequency response of a HA
Microphone
What is a transducer
Electret microphone
Amplifiers:
Generate distortion
A linear amplifier has a 1:1 relationship, this means that if you rotate the volume control on a linear aid , you change
The gain and the output
Hard peak clipping occurs in a
Class A amplifier
Peak rounding
Causes harmonic distortion above the knee
There are two types of compression- input and output. The difference is:
The placement of the feedback loop
