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63 Cards in this Set
- Front
- Back
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Conductive HL
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Most are medically or surgically treatable; most with permanent do very well with hearing aids
Ex: cerumen impaction, acute otitis media, chronic otitis media, perforated eardrum |
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Sensorineural HL
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Most losses are sensory, not neural; i.e. problem in the cochlea or frequently problems with the outer hair cells. Degree of loss tends to be related to the amount of hair cell damage (the greater the degree, the more likely there's outer and inner hair cells involved).
Most with this benefit from hearing aids because amplifying the signal overcomes the sensitivity loss due to hair cell damage. |
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Hearing Aids
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Miniature amplifiers. Capture incoming sounds, increase its intensity, and deliver it to the ear.
Amplify the signal to compensate for sensitivity loss. Rely on remaining IHCs to transduce the signal and stimulate auditory nerve. Types: Body-worn, Behind-the-ear, In-the-ear, In-the-canal, Completely-in-the-canal, and bone conduction |
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Pressure
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Force per unit area
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Mechanical hearing aids
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Increase sound intensity by concentrating sound energy from a larger area to a smaller ares.
Ex: ear trumpet |
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How hearing aids work...
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1) Sound is picked up by the microphone, which converts acoustic signal to an electrical signal
2) The electrical signal is then amplified and/or processed in some way 3) The receiver converts the electrical signal back to an acoustic signal |
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3 types of processors or circuits
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1) Analog
2) Digital 3) Hybrid |
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Analog
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-Sound is processed as a continuous electrical signal (generated by the microphone).
-Signal is modified by electronic components -Hearing aid characteristics are adjusted by screw settings |
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Digital
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-Electrical signal from mic is converted into 1's and 0's
-Computer chips carry out the various signal modifications -Characteristics are programmed using specialized software -Can store multiple sets of characteristics -First true one debuted in 1998 |
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Hybrid or "digitally programmable"
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-Sound remains in analog form
-Electronic circuits modify the signal -However, hearing aid settings are controlled using computer software and stored in hearing aid digitally -Can have multiple settings stored -Debuted around 1990 |
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Hearing aid characteristics
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Gain
Frequency Response Input/Output function |
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Hearing aid components
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Microphone
Amplifier Receiver Volume control wheel Battery Telecoil |
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Gain
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The difference in dB between the output and the input. This is how much amplification the hearing is providing.
The more severe the hearing loss is, the more ___ you need. Prescriptive formulas are often used to determine how much a given patient should have at each frequency. |
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Input-Output Function
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Shows how hearing aid output changes as a function of input level.
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Linear Hearing Aids
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Have constant gain for all input levels (to some maximum output)
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Nonlinear Hearing Aids
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Gain varies depending on input level.
Low level sounds are amplified more (they get more gain) than high-level sounds. |
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Omnidirectional Microphone
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Single microphone, picks up sound equally well from all directions
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Directional Microphones
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Designed to give strongest response to sounds in front of the wearer.
The best way to improve speech understanding in noise with a hearing aid. May have a switch or be automatic. |
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Amplifier
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Processor
Can be analog or digital, linear or nonlinear |
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Receiver
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Converts electrical signal back to an acoustic signal for delivery to ear
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Volume Control Wheel
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User can adjust gain as desired
*Nonlinear aids do this automatically-- often called automatic gain control |
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Battery
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Usually the largest part of the hearing aid
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Telecoil
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Picks up magnetic signals
-From an analog telephone -From an induction looop User switches aid from "M" to "T" |
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Hearing Aid Selection
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May occur immediately after evaluation, or as a separate appointment
Consider: Candidacy, Type/Style of hearing aid, Hearing aid features, Monoaural vs. Binaural, Expectations Must get medical clearance, complete loudness growth measures, earmold impressions, and pre-testing for later validation |
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Candidacy
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Whether the patient is handicapped by the HL
Whether the patient will benefit from HAs Whether the patient wants HAs |
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Type/Style of Hearing Aid
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Required gain and desired features (the larger the HA, the greater gain and more feature you can get)
Physical condition of outer ear (size, cerumen production, skin sensitivity) Cosmetic concerns Financial concerns |
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Severe Hearing Loss
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Behind the ear hearing aid
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Mild Hearing Loss
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In the canal hearing aid
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Financial Considerations with HAs
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Average prices:
Digital= $2022 Analog= $935 |
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Multiple Memories
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Can have different internal settings for different listening environments
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Remote control
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For controlling volume, or switching between programs
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Binaural Fitting
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Better sound localization
Improved speech recognition in noise More natural sound quality Avoid auditory deprivation effects |
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Binaural summation
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It's easier to hear with two ears than with one
Helps assign/distinguish sounds |
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Monaural Fitting
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Asymmetrical HL
When one ear isn't a candidate for some reason Mild HL |
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Real-ear Measurements
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Measure sound at eardrum without the hearing aid, then with the hearing aid.
Adjust the hearing aid to meet prescriptive targets and achieve good sound quality. |
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Functional gain
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Measure aided pure tone THs in the soundfield and compare to unaided-- difference between those two measures
Not recommended as replacement for Real Ear |
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Hearing Aid Orientations
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Instrument features and landmarks, Working knowledge of the components, Usage Patterns, Use and Routine maintenance, Storage, Battery Management, and Telephone use
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Feedback
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The high-pitched whistling sound.
Sound from receiver is picked up by the microphone and re-amplified. Normal when: HA is turned on but not in ear or when a hard objects is placed near the ear when wearing the HA |
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Possible causes of ongoing feedback:
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Volume set too high, poor fit, or cerumen build-up in ear canal
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HA follow up
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Should be done 2-4 weeks after fitting (before the end of the 30 day trial period)
Assess benefit, review "hands on" info Schedule another in 6-12 months |
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Cochlear Implants
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Bypass the usually pathway and stimulate the auditory nerve directly.
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Cochlear Implant Mic
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Picks up acoustic signal, converts it to an electrical signal
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CI Speech Processor
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Extracts key acoustic features of speech
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CI Transmitting coil
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Sends processed signal to internal device
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Internal Components of a CI
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1) Receiver-stimulator
2) Electrode array |
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CI Receiver-stimulator
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Receives processed signal from the transmitter and then sends it to the electrode array
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CI Electrode Array
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8-22 pairs of electrodes plus ground electrode
A magnet holds the external transmitting coil in place |
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How a CI works:
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1) Mic picks up sounds
2) Info is sent from mic to speech processor 3) Speech processor analyzes info, converts to electrical code 4) Coded signal travels to transmitter, which sends through skin to receiver 5) Receiver decodes signal, sends code to electrodes 6) Electrodes stimulate nerve |
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Spectral Peak (Speak)
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Delivers low-frequency information to electrodes near apex, and high-frequency information to electrodes near base
Focus: Spectral characteristics of speech |
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Continuous Interleaved Sampling (CIS)
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Focus: Temporal (time) characteristics of speech
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Advanced Combination Encoder (ACE)
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Combines CIS and Spectral Peak
Optimizes frequency and timing information |
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Post-lingually deaf adults
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Open-set sentences in quiet: approx. 85% with current technology
Speech and music remain difficult to hear |
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History of CIs
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Idea of using electrical stimulation to activate auditory system dates as far back at the 1800s
1972: First implanted in an adult; was one electrode (channel) 1985: Multi-channel approved by FDA for use Criteria then: >100 db HL and no communication benefit from hearing aids In 2002, approx. 23,000 Americans had one |
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Current FDA criteria for CIs
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Adults:
Loss >70-80 dB HL No upper age limit Children: Loss >90 dB HL |
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Candidacy Considerations for CIs
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Medical condition and status of cochlea, Integrity of auditory nerve, Benefit gained from HAs, Presence of a support system, Realistic expectations, Commitment to long-term rehab
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CI team
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Typically a multidisciplinary team: SLPs, Psychs, teachers, social workers, and parents
At minimum: Otolaryngologist: medical decisions and surgery Audiologist: determines candidacy and programs the speech processor |
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Treatment for CIs
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For adults: speechreading and managing communication breakdowns
For children: conditioning for play audiometry After surgery: usually 3-4 weeks of healing before processor is turned on |
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Initial fitting and programming of CI
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Takes 1.5-2 hrs, may schedule over 2 days
Audiologists use special software to program or map the speech processor |
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Neural Response Telemetry (NRT)
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Most current implant systems have this feature
Allows audiologists to record auditory nerve responses following stimulation of the implant electrodes |
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Mapping speech processor for CIs
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Establishing the T (TH) and C (UCL) levels for electrical stimulation-- this sets the map, which keeps all stimulation within this range
Most systems allow multiple maps |
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Follow-up programming ad therapy
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Usually occurs within 2 weeks: re-evaluate dynamic range, adjust maps, and begin screening auditory abilities
Auditory training: amount and duration vary; depends on age, length of deafness, and which clinic you attend |
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Sensation Level
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Amount of intensity above TH
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Recruitment
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Rapid increase (gain) of loudness
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