Hearing Aids Intro Handout de Jonge Page 1 of 19
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Syllabus, Hearing Aids, CD 5703
Instructor: Robert de Jonge, Ph.D.
Office: Martin 58, 660-543-8809,
Required Texts: See reading assignments
Exams: There will be two exams, a mid-term and a final. Each will be multiple choice. The final will not be comprehensive.
Attendance: Class attendance policy is consistent with University policy. In addition, four absences are allowed for whatever reason (approved or not, at your discretion). Beyond this the final grade is reduced by 1/4 of a letter grade for each additional absence. The final grade will be increased by 1/4 for each of the allowed absences that is not used. Perfect attendance improves performance by one full letter grade.
The second half of the class will focus upon hearing aid measurement and selection. The main idea is to get you comfortable with the process of converting an audiogram to an appropriate hearing aid prescription, including venting, special earmolds, etc. To facilitate this we will work with a HyperCard stack, "Hearing Aid Selection," which runs on the Macintosh computer. The final exam will include a practical section where you will use this stack to fit a hypothetical client. It will help you a lot if you become familiar with this stack. There's lots of useful and practical ideas within it. Consider it a "reading assignment." There is also a take-home self assessment assignment targeting your understanding of hearing aid selection and verification. The hearing aid lab will also include a practical assessment..
Topics (a wish list)
1. Introduction/Overview
1.1 Overview of major issues involving amplification
1.2 History of hearing aids
1.3 Federal Regulations & state licensure
1.4 Private practice, dispensing
1.5 Types of hearing aids
-body -ear level or behind-the-ear (BTE) -in-the-ear (ITE)
-canal (ITC), completely in the canal (CIC) -CROS -eyeglass
-programmable ITE, BTE, ITC, CIC
1.6 Components/functions/controls of hearing aids
-microphone -amplifier
-receiver
-gain control
-tone control
-SSPL control
-noise suppression
-telecoil
-battery types
-compression and AGC
-earmold types
-dampers
-feedback
-analog/digital programmables
-multiband, channels
-memories
-remote controls
-programming software
1.7 Troubleshooting/routine maintenance
1.8 Taking an earmold impression
2. Measuring hearing aid performance
2.1 Test equipment
2.2 HA-1 and HA-2 couplers
2.3 Specification of hearing aid characteristics:
(ANSI S3.22-1982, 1987, 1996 or ASA STD 7-1982, 1987, 1996)
-OSPL90
-HF-ave OSPL90
-HF-ave full-on gain
-Full-on gain
-reference test gain
-frequency response
-equivalent input noise level
-harmonic distortion
-battery current
-induction coil
-AGC aids
-chart paper
2.4 Real-ear measures of hearing aid performance (ANSI S3.46-1997):
-REUG, REIG, REAG, RESR, RECD, REDD, etc.
3. Hearing aid coupling/acoustics
3.1 Receiver characteristics
3.2 Earhook
-damping
3.3 Tubing
-length/diameter
-damping
-smoothing the response
3.4 Venting earmolds
-parallel/side branch
-open mold (Jansen)
-length/diameter
-damping
-PVV/SAV
-insertion depth
-vent response
-feedback control (Macrae)
3.5 Stepped diameter earmolds
-effects of diameter
-damper placement
-Libby horn
-belled
-high freq cavity
3.6 Real-ear effects
-KEMAR, probe-mic measurements
-Zwislocki vs. 2-cc coupler gain
-middle ear effects, middle ear pressure
-effects of varying ear canal dimensions
-venting large canals (resonance effects)
-modeling (predicting) hearing aid performance
-sound field-to-eardrum transform (Shaw curve)
-in-situ vs. insertion (etymotic) gain
-microphone placement, body baffle
-Fry's test box (Fonix 6500)
4. Hearing aid selection/evaluation
4.1 Candidacy for a hearing aid
-degree of loss
-speech recognition ability
-tolerance problems
-unilateral losses
-subjective characteristics
4.2 Preselection process
-ear(s) to fit
-type of aid
-specifications (gain,etc.)
-coupling
4.3 Selective amplification
-Mirroring the audiogram
-Gain equal to a proportion of hearing loss
-Mirroring the MCL curve
-Bisecting the dynamic range
-Master hearing aid
-Harvard report
-MCL and LDL measurements and speech recognition
-Software (IHAFF, DSL, Fig6, HAS)
4.4 Hearing aid evaluation
-Carhart (1946) method
-Tournament strategies
-Measuring functional gain
-Real-ear measures
4.5 Reliability/validity of selection/evaluation process
-reliability of speech testing
-problems with measuring functional gain
5. Binaural amplification
5.1 Advantages of binaural amplification
-objective benefits
-subjective evaluation
5.2 Reported disadvantages
5.3 Candidacy
5.4 Selection and evaluation
5.5 Dichotic, split band amplification
5.6 Varieties of CROS hearing aids
6. Management
6.1 Counseling
6.2 Follow-up
6.3 Adjustment
6.4 Measures of user satisfaction (eg., APHAB, COSI)
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Assignments
•The hearing aid lab will meet for approximately 2 hours per week. You will be able to document skills you have developed.
Readings
Pluvinage, V., "Rationale and development of the ReSound system," in Understanding Digitally Programmable Hearing Aids, R. Sandlin (ed.), 1994.
de Jonge, R., "Hearing aid evaluation and selection: A perspective," Corti's Organ, Fall newsletter of the American Auditory Society, 1989. (See next card)
"Hearing Aids: Standards, Options, and Limitations," Michael Valente (ed), Thieme, 1996.
oChap 6, Valente, Valente, Potts, and Lybarger, "Options: Earhooks, Tubing, and Earmolds."
"Strategies for Selecting and Verifying Hearing Aid Fittings," Michael Valente (ed), New York, Thieme, 1994.
•Chap 9, de Jonge, "Selecting and verifying hearing aid fittings for symmetrical hearing loss."
•Also, check out the other chapters, there are lots of good ones
Hearing Aids: Standards, Options, and Limitations, M. Valente (Ed.), New York, Thieme, 1996.
•Chap 2, de Jonge, R., "Real-Ear Measures: Individual Variation and Measurement Error"
•Also, look at the other chapters
"Probe Microphone Measurements: Hearing Aid Selection and Assessment," H. Gustav Mueller, David B. Hawkins, Jerry L. Northern, Singular Publishing Group, 1992.
•Chap 3, Mueller, "Terminology and procedures."
•Chap 5, Hawkins, "Prescriptive approaches to selection of gain and frequency response."
•Chap 6, Mueller, "Insertion gain measurements."
•Chap 7, Hawkins, "Selecting SSPL90 using probe-microphone measurements."
•Chap 13, Hawkins & Mueller, "Test protocols for probe-microphone measurements."
"Handbook of Hearing Aid Amplification, Volume I and II," Robert E. Sandlin (ed), College Hill Press, 1988.
Volume I
•Chap 1, Lybarger, "A historical overview."
•Chap 5, Dillon, Compression in hearing aids."
√Chap 7, Libby & Westermann, "Principles of acoustic measurement and ear canal resonances." (Scan for exposure to info)
Volume II
•Chap 1, Reiter, "Psychology of the hearing impaired and hearing aid use: The art of dispensing."
•Chap 3, Pascoe, "Post-fitting and rehabilitative management of the adult hearing aid user."
"Hearing Aid Evaluation," Margaret W. Skinner, Prentice Hall, 1988.
•Chap 2, "Effects of hearing impairment on the identification of speech sounds."
•Chap 10, "Counseling and hearing aid orientation."
"Amplification for the Hearing-Impaired," 3rd Edition, Michael C. Pollack (ed.), 1988.
•Chap 2, Pollack, "Electroacoustic characteristics."
•Chap 11, Glaser & Pollack, "Private practice and hearing aid dispensing."
Assignments for mid-term
1. Introduction/Overview
•Pollack, Chap 2, 3 (p. 105-114, impression technique), 11
•Sandlin, Volume I, Chap 1
•Sandlin, Volume II, Chap 1
•Skinner, Chap 2
•Hearing aid selection and evaluation: A perspective.
Assignments for final
2. Measuring hearing aid performance
•User's manual for the Fonix hearing aid test system.
•Sandlin, Volume I, Chap 5, 7
3. Hearing aid coupling/acoustics.
•Valente, et al. Chap 6 (p. 252-326)
4. Hearing aid selection/evaluation.
•Mueller et al., Chap 3, 5, 6, 7, 13
•HyperCard stack: Hearing Aid Selection.
5. Binaural amplification.
•Valente, 1994, Chap 9.
6. Management.
•Skinner, Chap 10.
•Sandlin, Volume II, Chap 3
7. Programmable hearing aids
•Pluvinage
9. Individual variation.
•Valente, 1996, Chap 2.
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You should understand…
•What a hearing aid is; i.e., anatomy of the aid
◊what are the major components
◊what controls are available
◊earmold coupling
•How the hearing aid functions; i.e. physiology of the aid
◊how do the major components function
◊what effect does each of the controls have
-objectively, electroacoustically
-perceptually
◊functions of earmold "plumbing"
•How to measure the characteristics of a hearing aid
◊ANSI specs
◊you will learn how to use the Fonix system
•How to select a hearing aid
◊prescriptive procedures
◊relate ANSI specs to user's needs
◊HyperCard stack, "Hearing Aid Selection"
◊DOS/Windows based selection software:
-IHAFF, DSL[i/o], Fig6, NAL-NL1
◊Manufacturer's software for fitting programmables; e.g.:
-Siemens Connexx (part of Unity)
-Oticon's OtiSet
-Micro-Tech's Meridian
-Phonak's Professional Fitting Guide (PFG)
-ReSound's Resource
-Starkey's ProConnect
-Argosy's Quadrasound
-Danavox's Danafit
•How to evaluate, verify the selection
◊mainly, real-ear probe mic measures
◊the practical part of final exam will assess the selection/verification process…
-begin with an audiogram
-use Hearing Aid Selection stack to…
√select REIG
√convert REIG to 2-cc FOG response
√Select RESR
√convert RESR to SSPL90 curve
√select a matrix
√select a manufacturer's hearing aid
◊use Fonix system to verify the selection
•The dispensing environment
◊legal, ethical issues
◊audiologist & dealer relations
◊state licensure, FDA guidelines
•Historical perspectives
◊acoustical aids
◊electrical aids (carbon mic)
◊electronic aids (vacuum tube, transistor, integrated circuits)
◊programmable aids (ReSound, Phonak)
◊fully digital aids (Widex Senso, Oticon Digifocus)
•Taking the ear impression
◊you will order your own mold
•Troubleshooting hearing aids
◊electroacoustical, mechanical problems associated with the instrument
-evaluate and solve common problems
◊using the dremel tool, bench grinder to modify earmold, ITE casing
•At the end of the class you should have a good beginning understanding of how to:
◊develop prescriptive targets based upon hearing loss
◊select and adjust a hearing aid to meet those targets
◊how to take an ear impression and order the hearing aid
◊how to perform basic shell modification and troubleshooting
◊what issues to discuss with the patient in hearing aid counseling (APHAB, COSI)
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Final Exam Questions
Study Questions for the "Hearing Aid Selection" stack…
Approach the following questions in the same way that you would an "open book" exam, except that the open book is the hearing aid selection program. For example, you don't have to remember what the exact dimensions of a 6R12 earmold are, just how to find the information.
1. Describe how the program treates the relationship between MCL and insertion gain, UCL (or LDL) and SSPL90. Under what conditions will the insertion gain never be less than 0 dB, why?
2. The AI is 50%. What would you expect the intelligibility to be for monosyllabic words, sentences? What is the AI weight for the 1/3 octave band surrounding 1000 Hz? Is speech presented at a 40 dB SL more intelligible than speech presented at a 30 dB SL. Why?
3. At 4000 Hz the real-ear gain (REIG) is 10 dB. What coupler gain would produce this REIG for an ITE aid, a BTE aid? Why is there a difference between the ITE and BTE aid?
4. You have an audiogram threshold of 40 dB HL. This would correspond to what SPL in a) a 6 cm3 coupler b) an average ear canal c) the sound field?
5. At 2000 Hz the REAG gain is 40 dB, the insertion gain (REIG) is 28 dB. What is the REUG?
6. Threshold is 50 dB HL at 2000 Hz. How much insertion gain would Berger prescribe? Byrne and Dillon if the PTA was 55 dB?
7. What happens when you increase diameter and/or reduce the length of the vent? What happens to the REIG when the canal/vent system resonates?
8. For a closed earmold, enter a mild gradually falling hearing loss. Use NAL to calculate an REIG. Using the "trace curve" effect, demonstrate the effects upon the REIG of a) using a 1.5 x .3 cm vent b) adding an undamped 8CR earmold c) changing the shape of the canal resonance curve (REUG). Should you use ITE or BTE corrections with the 8CR mold?
9. What is the Zc of a 3 mm ID tube? What are the dimensions of a 6C10 earmold. If you want a high frequency emphasis would you choose a 6C10 or 6B10 mold? What kinds of problems occur with dampers?
10. Describe the earmold that compensates for the loss of the canal resonance. What does it mean to have a reverse slope hearing loss? Which earmold would be appropriate for a reverse slope hearing loss? Compared to the standard closed mold configuration, how much extra gain does a 3 mm horn supply at 4000 Hz?
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Real-ear and 2 cm3 Coupler Measurements
1. Can you perform all the ANSI measurements using the Frye 6500 test box? Doing the testing is a lot easier than understanding what the information means. After you get these measurements, can you explain what they mean? You should be able to, both for BTE and ITE aids.
2. Can you use the Quick Probe II to measure REUG, REAG, REIG, RESR, RECD and REOG? Can you enter an audiogram and calculate a target gain curve? Can you enter your own, customized target gain curve? Can you determine whether the hearing aid matches the target? Can you make adjustments in the trim pot settings of the hearing aid to more closely match the target? Can you explain what you are doing in such a way that your patient can understand it?
3. Can you use the Quick Probe II option to measure the spectrum of noise generated by a hearing aid while it is in the ear canal of a listener?
4. How would you use the Quick Probe II to measure the occlusion effect, produced by wearing an ear mold, at a frequency of, say, 500 Hz? By venting the hearing aid, would this occlusion effect be eliminated? If so, by how much, and how would you measure it?
5. How would you use the Quick Probe II to measure the real-ear attenuation of a hearing protector device, such as an EAR plug?
6. Based upon a particular volume control wheel (VCW) setting for a hearing aid, the use gain setting, could you predict the hours of battery life for a particular size battery?
7. People will cup their hand behind their ear when trying to listen. Does this really help? If so, by how much? How would you answer this question?
8. Can you use the Frye box to demonstrate 1/4 wavelength resonances (say, for a "der der" tube)?
9. The impedance of a tube increases with frequency. Demonstrate this using 1 inch of #13 tubing attached to the HA-2 coupler.
10. Does the inherent noise of a hearing aid increase, or decrease as the VCW setting is increased? Can you use the Quick Probe II to measure this for a particular listener.
11. If you are performing ANSI measurements for a hearing aid, how do you "let the equipment know" that you are measuring a linear vs. ITE aid?
12. During 2 cm3 coupler measurements you can display the input-output function for an AGC aid. How would you do this? Normally, the display is dB SPL out vs. dB SPL in. Instead, can you get a display of gain vs. input?
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Topics for Hearing Aid Lab
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