amplifying technology Flashcards
prescription hearing aids, self fitting OTC Hearing aids, and pre-set OTC hearing aids fall in what category ?
FDA Regulated Devices: intended for individuals w/ hearing loss
personal sound amplyfing devices, hearables and consumer audio devices (HAT, etc) fall in what category ?
Not FDA Regulated Devices: intended for ppl w/ normal hearing
OTC hearing are for what kinds of HL?
people who PERCIEVE a mild to moderate hl
we dont fit but we repair
db input + db gain = ???
db output
what is input ?
The INTENSITY of the acoustic signal entering the device
-Ex. mic or ear
what is gain
The amount of AMPLIFICATION added to the input signal
what is output?
The INTENSITY of the signal that’s delivered into the ear canal
how may input appear in programming software?
May appear as dB values or as a loudness descriptor in programming software
Soft/50 dB; Moderate/65 dB; Loud/80 dB
what db levels are considered as soft db inputs?
40-50 db
what db levels are considered as a moderate input level?
65 db
what db levels are considered as a loud input level?
75-80 db
how does gain appear in software programming ?
Equals the dB added to each frequency range and input level
-in the graph on the side it’s the amount of additional input you are adding
how does output appear in software programming
Equals the intensity arriving to the tympanic membrane (TM)
it’s the intensity coming to the t.m
in this class, when we use db, what does it represent ?
DB SPL
when is db HL used ?
ONLY WHEN TESTING AUDIOGRAMS
when do we use db SPL?
we use it in everything else when were not testing audiograms
when is audiometric data converted from HL to SPL?
it’s converted before we’re going to fit amplification
the audiometric data is conversion is based on what?
This conversion is based on the size of the average adult ear
what is an important factor to remember when we’re going to start to fit devices
are all ears the same size?
in the acoustic ear, what did people use?
-happened from the 13th to 19ht century (the 1st era)
- they didn’t have ELECTRIC amplification so the used physical ways to increase signal intensity
what was the acoustic horn principle ?
-Horns amplify sounds when waves are reflected into a progressively narrower area, thereby increasing the sound pressure level that reaches the ear ***
it focused on amplification
-They increase sound directionality
-caused distortion
-All frequencies are equally amplified
-cant control amplifications between low and high freq
-The intensity of an acoustic signal changes as it travels through a horn
what was the first acoustic horn ?
hand cupping
how many db gain did hand cupping contribute to the signal?
-It added +5 -10 dB of gain to the input signal in mid to high frequencies
-It increased gain of acoustic signals arriving from the front
-It attenuate acoustic signals arriving from the rear
what does the length and size of the horns opening determine?
-The length and size of a horn’s opening determines the final output intensity and which frequencies are amplified
-Increased length of the horn increases the SPL energy transferred to ear
-The wider opening collects more sound
-The combination of increased length & wider openings maximizes gain added to the input signal
-the longer the horn the longer the amp
what does frequency responses compare ?
Frequency response curves compare the intensity of the input signal to either the added gain, or final output of a device
what happens when amplitude output increases ?
Amplified output increased when the speaking tube length increased
what did the carbon era contribute to?
The 1st “electric” hearing aids used a carbon microphone and a receiver; © 1902
what did the carbon era convert ?
-Carbon microphones collected the acoustic signal & converted it into an analog (identical) electric signal
- The receiver then converted the analog electric signal back to an acoustic signal
electric hearing aids convert what to what?
Electric hearing aids convert an acoustic signal into an analogous electric signal
the receiver converts what to what
The receiver converts the analogous electric signal back to an acoustic signal
what don’t carbon hearing aids contribute?
Carbon hearing aids didn’t have amplifiers to add gain to the acoustic input signal
resonance reflector positioned behind the mic adds how much gain to the signal input
-“Resonance-reflectors” positioned behind the microphone added 5-10 dB SPL of gain to the input signal b/w 1k Hz to 3.5k Hz
-Microphones were stacked on top of one another to add more gain
the vacuum tube era contributed to what
The invention of the vacuum tube amplifier added gain to increase the amplitude of the analogous electric signal. Increased gain resulted in increased acoustic output.
The transitior era contributed to what?
-A transistor is an electrical component used to increase current flow of electronic signals (increases amplitude)
-A resistor is an electrical component used to add or remove resistance to the flow of electrical current (modifies frequency response or output)
what do todays device contribute in terms of transistor era ?
Today, devices combine multiple transistors & resistors into a single component referred to as “integrated circuits
what is integrated circuit?
Integrated circuit: an electronic circuit formed on a small piece of semiconducting material, performing the same function as a larger circuit made from discrete components.
what do transistors and resistors allow?
Transistors & resistors allowed modification of gain & output signals!
what do transistors conduct ?
they conduct the electrical signal
what do transistors do in a hearing aid?
-In a hearing aid it amplifies the amplitude of a signal
-i.e., amplifiers, take a tiny electric current at one end (analog electric current) and produces a much bigger flow of electric current at the other (output current)
transistors can act like what in hearing aids?
Connected transistors can act as logic gates carrying out decision making in hearing aids.
Resistors conduct what ?
the electrical sine signal
what are resistors used for ?
-It’s used to modify the output, frequency, or intensity in some way
-i.e., filter all the low frequencies signals and don’t let them pas through the circuit
what is a potentiometer?
-A small resistors control used to modify the output signal in early analog hearing aids.
-Manipulated the output signal, frequency response, the amount of gain added, & the compression ratio
-AKA- “Trimmer pot”, or “pot screw”
