Back to the Aural Rehabilitation
Class PagePersonal Amplification Systems
Back to the Aural Rehabilitation
Class Page
I. Purpose of Hearing Aids
A. Amplify speech to make it more audible
1. Increase loudness of ___________ frequencies
2. Especially ___________ frequencies for consonants
3. Average intensity of speech at 1 ___________
- 60 to 70dB SPL
- ___________ HL
4. Each 10dB decrease in intensity = ___________ of loudness
For a given speech level of:
___________- normal speech intensity
comparisons of .......
40dB HL 1/2 as loud
30dB HL ___________ as loud
20dB HL 1/8 as loud
10dB HL ___________ as loud
-Compared to person with 10dB HL threshold for speech:
20dB threshold = ___________ as loud
30dB threshold = 1/4 as loud
40dB threshold = ___________ as loud
50dB threshold = 1/16 as loud
B. Who needs hearing aids?
-More loss, ___________ need for amplfication
-Mild loss- ___________ vs. easy communication
-50dB loss - hearing and ___________ hearing speech
-Profound loss - detecting presence of speech speechreading cues/___________ info
C. Limitations - hearing aids don't provide:
-Normal ___________
-Normal ___________
-Normal ___________
-Clear understanding in ___________
-Correction of ___________ problems in inner ear
II. Characteristics of Hearing Aids
A. Basic Components (p. 30, fig. 2.1; p. 75, fig. 2.19)
1. Microphone - acoustic energy to electric
2. Amplifier - increases the ___________ energy
3. Receiver - ___________ energy back to ___________
4. Battery - provides ___________ to amplifier
B. Types of Amplification Devices (p. 34-5, fig. 2.3)
1. Body Aid
-___________ losses and dexterity problems
-External receiver -___________ feedback
-Less than 4% of fittings today
2. Eyeglass aids
-Same fittings as BTE's with even ___________ chance of feedback because of ___________ location
-Approximately 1% of fittings
3. Behind the ear (BTE)
-Mild to ___________ losses
-Profound - need ___________ earmold fit
-Greater the gain (volume) of the HA ___________ the chance for feedback
-15-20% of fittings
BTE Variation (CROS) ___________ Routing of Signal
-No usable hearing on one side & ___________ hearing on the other side.
-1 to 2% of fitting
4. In the Ear- (ITE)
-All components fit into one custom shell
-Mild to ___________ losses.
-___________ feedback - receiver and mic location
-70-80% of fittings
5. In the canal- (ITC)
- Components close together - feedback
-Limited room for ___________ such as telecoil
-___________ to moderately-severe losses
-20% of fittings
6. Completely in the canal-(CIC) (p. 37, fig. 2.4)
-Fits further into the canal than ___________
-Increased gain because of ___________ placement
-Mild to moderate losses
-5% of fittings
7. Other Devices
-___________ stimulation to auditory nerve
-Persons who do not receive benefit from traditional hearing aids
-Requires ___________ procedure to implant electrodes into cochlear
-Speech processor worn ___________ the body
b. Tactile Aid
-Vibrations representing the signal delivered to skin
-May be single or ___________-channel stimulation to sternum, forearm, abdomen
-Also for persons who do not receive benefit from traditional ___________
C. Controls
1. Volume control -
-varies ___________ of hearing aids
-not always numbered
2. On/off (M/O) switch -
-if there's no switch on outside you must open battery door to ___________ battery from contacts to turn aid ___________.
3. Telecoil (T) switch - allows amplification of the ___________ signal from the telephone
(usually M/T/O switch)
-Not all phones emit a ___________ enough
-electromagnetic signal to be used with T-coil
-Public phones-
-blue grommet = T-coil compatible;
-___________ grommet = not compatible;
4. MT switch - Allows mic to be active along with the telecoil (M/MT/O)
5. Tone control switches or ___________
-N- normal frequency response
-H- ___________ frequency emphasis
-L- low frequency emphasis
6. Output controls
-Maximum power output (MPO)
-Max dB SPL output of the hearing aid
-___________ Sound Pressure Level (SSPL)
-Trimpot - done with screwdriver
-Prevents amp. from exceeding ___________
Usual range- 100 - ___________ dBSPL
7. Two types of output limiting
a. Peak clipping
-Input exceeds SSPL after it's amplified
-Peaks of waveform are ___________
-Output = only ___________ portion of signal
-Results in ___________ especially when maximum output is set so low that most of the signals are being clipped
b. Compression - automatic gain control(AGC) (p. 32, fig. 2.2)
-As input signal increases, the HA amp ___________ amount of gain so that the shape of the waveform is preserved
-Therefore ___________ distortion occurs
-Most often used with ___________ hearing loss and ___________ tolerance level for loud sounds
D. Earmolds (EM) (p. 42, fig. 2.6)
1. Types
Snap-ring or Receiver EM
- requires a snap-ring with full EM
- used with ___________
- for severe to ___________ losses
Standard or Regular EM
- flat outer surface, fills concha and sometimes helix
- like above EM but has ___________ instead of snap-ring connection
- used with ___________ and eyeglass aids
- for severe to profound losses
Shell EM
- outer surface carved out so that it is ___________
- fills concha but less mass than standard
- used with BTE and eyeglass aids
- for ___________ to severe losses
Skeleton EM
- has part of ___________ removed so there's just a rim
- used with BTE and eyeglass aids
- for mild to severe hearing losses
Half Shell EM
- like the shell but only fills the lower half of the concha
- used with BTE and eyeglass aids
- for mild to moderate losses
Canal EM
- only fills the canal, may have an extension into the concha to ___________ it in place (ie, canal-lock)
- used with BTE and eyeglass aids
- for mild to ___________ losses
Open or Non-occluding EM
- just a rim to ___________ tubing into ear canal
- ___________ sound enters canal
-used with BTE and eyeglass aids
-for mild losses
2. Materials
-Lucite - ___________ plastic - lasts longest.
-Silicon- ___________, reliable, for profound losses
-Hypo-allergenic - soft and opaque
3. Procedure
-Impression of ear- ___________ min
- Send impress to lab with specific order (loudness testing, p. 56, table 2.2)
-Earmold returned - ___________
4. Modifications (p. 45, fig. 2.8; p. 43, fig. 2.7)
-Vents - ___________ equalization and more natural sounding voice of the user
-Ear canal length & sound opening ___________ and ___________ the canal greater the high frequency emphasis
-Filters or lambs wool in tubing/rec/mic to ___________ the response and reduce output
5. Problems
-Tubing or soft mold ___________
-Tubing ___________
-Earmold becomes too ___________
(may remake every 3 months for toddlers)
E. Batteries
1. Types
-Mercury - least expensive
-Silver - most ___________
-Zinc air- last ___________ - tab covering air hole(s)
-Nickel cadmium- (rechargeable) most often used in ___________ but also in ITEs
2. Common Sizes-in decreasing order of size
-___________ For Power BTE’s
-___________ For Power BTE’s, also common in ITE’s and some ITC’s
-___________ For ITE’s and ITC’s
-___________ For CIC’s
3. Battery Life-Hours of Operation depend on...
-Type of Battery (most have voltage of 1.3 to 1.5
-Type of Hearing Aid (higher the power, higher the drain)
-___________ of Use
-Special Circuitry Requirements
-___________ Control Setting
F. Options on Aids
-Telecoil-Allows receipt of ___________ signals from phone or assistive device (neckloop)
-Direct Audio Input-Allows direct electrical connection to an external mic or assistive device (FM system)
-Directional Microphone-Allows greater senstivity to sounds from the ___________ than from the ___________
III. Electroacoustic Characteristics
A. Why do we need to test them? (p.50, fig. 2.12)
-Manufacturer specifications
-Appropriate hearing aid settings for a client
B. How do we test the aids? (p. 48, fig. 2.10)
- ___________ hard-walled coupler that approximates ear canal volume
- test box consisting of sound chamber, ___________, and microphone
- ___________ measurement equipment
- printout of electroacoustic measures
C. Measurements (p. 47, fig. 2.9; p.49, fig. 2.11)
___________ specifications for evaluating HA (so that everyone will do it the same way)
-Gain (volume) of the aid
-across frequency range (250-6000 Hz)
-gain = ___________ - input
-Maximum power output
-saturation sound pressure level (SSPL90)
-measured across frequency range when the volume is___________ on and 90 dB input is used
-Harmonic Distortion
-unwanted energy at harmonics of the___________ measured in %
-should be ___________ or less THD
-Input noise
-noise the HA makes with no input
-should be less than ___________ SPL
IV. Hearing Aid Use
A. FDA regulations
-Manufacturer's specifications
-Limitations in restoring normal hearing
-Medical exam within last ___________
-Medical waiver if person is over ___________
-30 day trial period
-Fit by licensed dispenser who is required to:
-pass an exam
-be a ___________ graduate
-maintain continuing education
-have certification of academic & practical training
B. Obtaining a Hearing Aid
SOURCES
-Audiologist
-Physician
-Hearing aid dispenser
-Mail order, but fit by a dealer or audiologist
-Social welfare programs
-MCH - maternal child health- kids under 18
-TRC -_______________________-for persons over 18 that will be employed as a result of amplification
-Sertoma,Lions or Kiwanas service groups
-Insurance companies
-Medicaid (but not ___________)
HEARING AID EVALUATION
Complete ___________ Evaluation
Determine the need/options
Order the aid/earmold
Evaluate the Aid- (p. 53, fig. 2.13)
___________ Measures (p. 61, table 2.3)
___________ Microphone (p. 55, fig. 2.14; p. 62, fig. 2.15)
Speech Recognition
PURCHASING AN AID
Typical Cost-$600-___________
Programmable aids more (p.42, fig. 2.5)
Completely in the Canal aids more
___________ aids more
Cost may include
Hearing Evaluation
Hearing Aid Check
___________
Followup for one year
FOLLOWUP
Minimally include re-eval within 30 day trial
Could include free visits for ___________
Could include returning the aid for ___________ minus the cost of dispensing (usually $100)
Could include remakes, alternate aid, adjustment of controls
Could include rehab sessions involving ___________
C. Adjusting to Amplification
May take ___________ weeks/months
-Involves learning to:
-listen to new sounds
-tolerate ___________ sounds
-tolerate earmold
-tolerate ___________ sounds
-Family's role in process
-be supportive
-don’t ___________ too much
-help out in care of aid & controls
D. Actual Wearing of the aid
-start gradually in ___________ situations
-expand to small groups
-finally ___________ situations such as restaurants
E.Care
-Cleaning
-no alcohol
-dry cloth to clean case
-file (fingernail) or ___________ to clean battery contacts
-earmolds (not ITEs) in soapy water
-Daily use
-___________ pak that removes moisture
-avoid ___________ and oil when wearing aid
-avoid heat, water, ___________
-hide from ___________ and small children
-remove ___________ when not in use
Physical Inspection
Case
___________
Tubing
Listening Check- Use a,i,___________,s,sh,___________
Switches
___________
Feedback
Linearity of gain
Scratchiness
___________
Distortion
Battery Check
Clean
Charge
Size
___________
Insertion
F. Troubleshooting (p. 64, fig. 2.4)
Common Problems
Dead
Weak
Feedback
Distortion
Intermittent
Noisy