midterm 1 Flashcards
(102 cards)
input
intensity of acoustic signal entering the device
-as dB or loudness descriptor in the software
gain
amount of amplification added to the input signal
-the dB added to each frequency range and the input level
output
intensity of the signal thats delivered to the ear canal
-the signal arriving at the tympanic membrane
equation to describe what is arriving at the tympanic membrane
dB input + dB gain = dB output
dB is always within _______
dB SPL
-remember there are different conversion factors but these are not intended for everyone
acoustic horn principle
as a signal arrives to a large horn and is channeled down to a smaller space, this causes the signal to increase (SPL increases)
-these horns amplify sound when waves are reflected into a narrower area
what are the acoustic benefits with hand cupping
-can add clarity to consonants
-can add 5-10 dB of gain
-can attenuate acoustic signals arriving from the rear
-effective for some with borderline hearing/very mild HL around the 1500 Hz area
explain the carbon microphone process and how it goes from acoustic signal to an electrical signal
the acoustic signal arrives to the microphone and vibrates the diaphragm which gets compressed and when it moves inward, the carbon balls get pushed together (positive voltage flow). the sound waves goes outward and will bring the diaphragm out with the carbon balls (negative signal)
-this back and forth direction results in an electrical wave that matches the input acoustic signal
what is the purpose of the receiver
converting that electrical signal back to an acoustic signal for the ear to hear
-after it becomes an electrical signal it will go through the receiver and will become an acoustic signal again
quick overview of a carbon microphone
sound wave → arrives at microphone → pushes on diaphragm and compresses carbon balls → creates a analog signal as the sound wave continues → creates a analog electric signal → receiver picks up the electric signal and makes it back to an acoustic wave
importance of a vacuum tube amplifier
this was the first HA with an amplifier that added gain to increase the amplitude of the analogous electrical signal
-vacuum tube amplifier was the first one created/used
transistors
electrical component used to increase current flow of the signal
-amplifies the amplitude of a signal
resistors
electrical component used to add or remove resistance to the flow of the current
-modifies the output
-can add more or less of certain frequencies
potentiometer
small resistors that the amount of control used can modify the output signal in the ear analog HA
function of the potentiometer
controls the flow of the signal
-can increase clarity, output and can add in certain frequencies
-can decrease output
-can reduce feedback
3 impression materials
addition cured silicone, condensation cured silicone and methyl-methacrylate
viscosity
how easily it flows before it is cured
-high will provide resistance during flow, will stretch the aperture
-low is runny, no resistance, no stretch to aperture
shore value
if it will remain its shape or will it be altered after its cured
-high or low shore value (will stay or will change)
stress relaxation
the materials ability to return to shape after removal from canal
-high and low stress relaxation (bounces back and does not bounce back)
contraction ratio
looking at the shrinkage over a 7 day period
-will it be the same or does it shrink
addition cured silicone
low viscosity, high shore value, high stress relaxation, will not shrink
condensation cured silicone
high viscosity, high shore value, high stress relaxation, will not shrink
methyl-methacrylate
medium viscosity, low shore value, low stress relaxation, will shrink
what is the ideal depth for an ear mold impression
2 mm beyond the second bend