Introduction & History of Amp Flashcards
what is the device that we fit
Rx HAs
do we fit direct consumer devices?
no
what are the FDA approved devices
Rx HAs
self fitting OTC
pre set OTC
what are fda not approved devices
PSAPS
Hearables (airpods)
consumer audio devices
what is coupling
earmold or dome
how we couple device to the ear
guts of the HA
signal processing
audiologic rehabilitation in regards to HAs
HAs are one option/solution that is under the full umbrella term
what is input
The intensity of the acoustic signal entering the device
sounds coming into the ear from the environment
May appear as dB values or as loudness descriptor in programming software
input
what is gain
amount of amp added to the input signal
what we are adding to the HA
soft input
50dB
moderate input
65dB
loud input
80db
What is the additional amp I am adding to the input in order to increase signal to the PT to make it more audible
gain
what is output
intensity of signal that is delivered into the ear canal
sounds coming into the ear + (what I add to the ear to the input intensity)
output
Ex: if soft is 50dB and we add 17 at around 3300 Hz, output signal?
output = 67dB
applying different amounts of gain based on
on input level and based on frequency
if the sound in the ear is 60 and we add 10 gain then output arriving to the tm?
70
Hearing level (HL) only used in
audio testing
why do we use HL for testing? why are audios in hl?
Easier to explain to the PT that the closer to 0 their hearing is the better
Took SPL values and made graphic info easier to explain to PT and this is why it s for testing only and nothing else
always a larger number
spl
Audiometric data is converted from ____ to____ before amp is fit
HL to SPL
what is the conversion from hl to spl based on
avg adult ear
are all ears the same? why is this important
no
important to recall when fitting devices
why when fitting HA’s can the avg conversion data cause issues
because not everyone is the same
Based on men and measuring SPL and creating an avg conversion factor for the avg adult male
what is the acoustic horn principle
the intensity of an acoustic signal changes as it travels through a horn
horns amplify sounds when waves are reflected into a narrower area
explain how the horn changes an acoustic signal
increase the SPL that reaches the ear
increase sound directionality
cause sound distortion
all frequencies are equally amplified (cannot control low vs highs that are ampd)
Increased horn length =
SPL increase energy to the ™
The length of a horn’s opening determines
final output intensity and which frequencies are amplified
wider horn opening
collects more sound
what are the acoustic principles of a horn that results in an increased output of an input signal? how does a horn determine the final output intensity?
- wider opening collects more sound so there is more energy input in
- the longer the horn the more amplification you get because you are channeling the signal into smaller spaces for a longer period of time
what are frequency response curves
compares intensity of the input signal to either gain or final output of the device
how does cupping your hand enhance the signal
around 1500 hz has been amplified but it only adds upward of 15dB of additional gain
how does a horn support hL
they change the output and frequency response and make the output loader to support greater hl
what are the acoustic benefits of hand cupping
add 5-10dB of gain to input in mid to high frequencies
increased gain from sounds arriving from the front
attenuates signals arriving from behind
consonant sounds are amplified
how does hand cupping work
soft sounds that do not have a lot of energy are collected by the hand and are going into the narrower space to get louder (10-15 dB)
what do directional microphones do
amplify sounds in front and attenuates the background noise
how does a carbon microphone work
it collects the acoustic signal and converts it into an analog (identical) electric signal
what does the receiver do
converts the analog electrical signal back to an acoustic signal
what is the conductor of electricity
carbon balls
what do electric HA’s do
convert the acoustic signal into an analogous electric signal
what does analog refer to
the same, shape of signal that came out of the microphone is exactly the same as shape of signal that went into the microphone
describe the process of electric hearing iads
Sound hits diaphragm, microphone converted to analog, receiver converts it back
sound wave comes in as an acoustic signal hitting the diaphragm and compressing it
creates carbon balls to push together
compression & decompression of carbon creates a + and - electrical current that matches the acoustic sine wave
now have an electrical imitation of sound that can be used
did the carbon era have amplification yet
NO
What is the purpose of the receiver
to convert the analogous electric signal back to an acoustic signal
is there amplification with the receiver
NO
what was the amplifier
vacuum tube
what does the vacuum tube do
adds gain to increase amplitude of the analogous electrical signal which results in an increased acoustic output
do you get binaural hearing if sound is connected in the middle of your body
sound only goes in one ear
causes listening effort and causes fatigue
if only getting amp in one ear, not getting a binaural signal
describe the process of the vacuum tube
heater element, catho (plate) and by process of the grid opening and closing it could be used to increase/expand the amplitude of the signal
why did early versions of vacuum tube amp require 2 batteries
one to warm the filament
one to amp sound
what replaced vacuum tubesin 1950s
small transistors & resistors
translator
increase current flow of electric signal (amplifier)
takes analog electric signal and increases its amplitude
Electrical component used to increase current flow of electronic signals (increases amplitude)
translator
Electrical component used to add or remove resistance to the flow of electrical current (modifies frequency response or output)
resistor
resistor
manipulates signal in some way
maybe we dont want amplitude in all frequencies, maybe we want to add compression to the signal so we use these to change and manipulate the electrical flow of the signal
devices combine ___ & ___ into a single component
transistors & resistors
combined transistors & resistors into a single component is called
integrated circuits
what are integrated circuits
Electronic circuit formed on small piece of semiconducting material, performing same fxn as larger circuit made from discrete components
rather than individual t and r now we have plastic motherboards that have embedded levels of these all attached to one another
motherboard
integrated circuits w/ ts and rs
describe how an analog ha works
input signal - acoustic vibration produces a sound wave
microphone - converts acoustic vibration to analog electrical signal
amplifier - amp of analog electrical signal is made larger by this by moving through a series of transistors to amplify the signal
receiver (earphone) - amplified analog electrical signal is sent here to be converted back into an acoustic signal
output signal - OS is amplified and exits the device and arrives to the TM causing audibility
is an analog ha a digital HA
NO
analog converts sound waves into electrical signals that are then amplified
digital ha convert sound waves into numerical codes that “attach” to information about the sound’s loudness/pitch
what do transistors do
conduct electrical sine signal
how do transistors conduct electrical sine signal
amplifies amp of signal in the HA’s
takes the analog electric current and produces bigger flow of electric current at the other (output current)
what do resistors do
impede electrical sine signal
how do resistors impede electrical sine signal
used to modify output, frequency or intensity in some way
for example, filter all the low frequ signals and do not let then go through the circuit
what is a potentiometer
small resistor control used to modify output signals in early analog HAs
other terms for potentiometer
Aka trimmer pot or pot screw
what is a potentiometer
small circular knobs that can be adjusted to effect high frequencies and output volume
on potentiometer how do you increase output
turn P clockwise
on potentiometer how do you increase clarity
turn H clockwise
on potentiometer how do you eliminate/reduce feedback
turn h counter clockwise
on potentiometer how do you decrease output
turn p counterclockwise
how we can change output signal for appropriate to the configuration of persons HL
help of t and r
with vacuum tube we can amplify the signal but
we dont have control of how loud the signal got
