Amplification Final Flashcards
Current Procedural Technology
codes for diagnostic procedures
healthcare common procedure coding system
describes services or supplies not outlined in CPT
(not covered by medicare)
ICD-10
classifying diagnosis or symptoms
high viscosity
thick
provides aperture stretch
condensation cured silicone
viscoity
how easily material flows
medium visocity
provides some stretch of aperture
addition cured silcone
low viscoity
runny loose
not change anatomy of ear
deep devices
addition cured
addition cured silcone
provides 1:1 parts polyvinyl siloxane
condensation cured silicone
dimethyl silxoane
paste and hardener
methyl methacrylate
powder and liquid
stress relaxation
material ability to return to shape after removal
contraction ration
shrinkage over 7 day period
sillicone shirnks
methyl methacryalate shirnks
shore value
after cure hardness
stability in box
silicone = high shore
methly metha = low shore
open jaw impression
increases size of aperture for snugger fit
condyle of mandible moves forward,pulls anterior canal wall
single impression
place horizontally on side of impression
bi lateral impression
place vertically
35% of speech intellgibilty comes from
2 khz
3khz and higher adds how much speech intellgibilty ?
25%
95% of speech intelggbilty comes from frequencies
5oo to 5khz
complaint of abnormal loudness growth curve
increased sensitivity to sound things are to loud
non linear signal proccesing is also called
automatic gain control AGC
what is frequency resolution
auditory systems ability to detect
discrete frequencies in the cochlea
frequency resolution:
the acoustic signal creates
a sharp peak on the basilar membrane at point equal to input frequency
sharp peak in frequency resolution provides
speech intellgibilty
When frequency resolution is decreased, the primary signal
is no longer enhanced
making it difficult to differentiate the
desired signal (speech) from the undesired signal (noise)
brain cant untangle
temporal resolution
ability of cochlea to detect small time related changes
good auditory temporal resolution
helps with understanding speech in noise
time related cues
gap detection
phonemic duration
temporal ordering
suprasegmentals
Interaural timing differences
low frequency cues <850hz
differences in arrival time because our ears are physically separated
interaural level differences
high frequency signals <3khz
ear to ear head shadow level differences
ILD - reduction in sound level for HF because
head casts a shadow affect for far ear
ILD is best for high frequency sounds bc
lows are not attenuated by head
binaural loudness summation
hear better with two ears over one
+3 db at threshold
+6 at 50 dB
+9 at 90 dB
binaural loudness summation
results?
Practically?
Patient perceive better loudness w/ 2 devices
- not as much gain needed
@ threshold 2-3dB
@supra threshold 6-8
binaural squelch
improved intellgibilty in noise to focus in on signal
binaural hearing offers 2-3dB SNR
binaural interferance
atrophy of corpus callosum redcues speech intellgibitly in noise with bi lateral input
solution of binaural interferance ?
remove one hearing aid when in noise
dichotic test
pinna effect
increase output w/ microphone and decrease wind noise
pinna effect part 2
pinna adds natural gain and spatial awareness
pinna boost boost intensity of HF signals by
7 db in 3k region
the pinnas resonant cavities may
attenuate low frequency signals and boost high
pinna effect: the deeper the microphone in the ear canal
better effect
sound bore proximity to the tympanic membrane
increases device output
when the volume reduces between TM and receiever
output increase by 6dB
deep microphone placement and deeply fit devices
increase by 13 dB
IP66
protection againt solids and liquids
dust light/powerful water jets
venting
release of amplifed low fequency 1.5khz or below
venting
reduces
allows
allows
occlusion effect
unamplified sounds travel to eardrum
aeration of canal or pressure release
vent is a column of air surrounded by tube has acosutic mass inside
HF signals (principles/physics)
HF signals dont have intertia to over come acosutic mass inside vent
Lf have energy to overcome mass
occlusion effect reported when
LF threshold loss is better than 50 dB
hallow like talkign in barel
occlusion effect management methods
reduction of OE
1)vent size
2) stabilize device in bony canal
venting allows LF environemtn signals to
travel directly to the ear drum w/o amplification
direct signal
allows patietns to hear LF signals and environemt sounds naturally when LF thresholds better than 40 dB
Direct sound refers to unamplified
signal arriving to the TM
1)
2)
3)
- If the amplified signal is 20 dB SPL louder
than the natural “direct” signal audibility of
the amplified signal dominates - If the amplified signal is an equal intensity to
the natural “direct signal” the two signals
combine and are perceived as one auditory
signal arriving to the TM - If the intensity of the “direct signal” is
substantially louder than the amplified signal, the direct signal will mask the amplified signal
The final output and frequency response arriving to the TM may
be unexpectedly altered when the direct signal moving inward
is in-phase or out-of-phase with the amplified sound moving
outward
inphase=
outphase =
double or cancel output signal
STANDING WAVES!!!!!
vent styles
parallel vents
angle vents
half/external trench vent
angle vent decreases can also cause
high frequency output
feedback
