MAINTENANCE OF AMPLFICATION
Adapted from:
Hammond, L. (1991). FM Auditory
Trainers: A Winning Choice for Students, Teachers, and Parents.
Minneapolis: Gopher State Litho Corp.I. RATIONALE
Gaeth and Lounsbury (1966) found 69% of HA in schools were _________ unstable.
1970s- studies found high numbers of malfunctioning HAs unless did _________ study (here the HAs were kept up with because knew they were being studied).
Diefendorf (1974) found # of malfunctioning HAs was reduced from 50% to 30% when a daily listening check program was instituted.
Bess, Sinclair, and Riggs (1984) studied 89 FM receivers and 28 teacher mics.
Found ambient noise average was ______ (should be 30dBA).
They did a physical inspection where 53% of receiver and 50% of mics malfunctioning- biggest problem was broken antennae.
Electroacoustic measurements showed 86% of volume controls set on half-on or more and 66% were 2/3-on or more.
They correlated degree of loss w/ use gain; correlation was ____.
Recommendations:
1. better communication between manufacturer and school
2. inservice needs
3. each child tested individuallyII. Equipment
Battery Tester
Wax Removal Tool
Listening Tube
Screwdriver
Forced Air Blower
Tubing
Tubing Threader
Tubing Cement
Tubing Spreader
Nail File
Contact Cleaner
Pipe CleanerSpare Parts:
Batteries
Button Receivers
Earhooks
Cords
BTE Receivers Boots
Oscillators
Neckloops
Transmitter MicrophonesSteps to Follow
1) No sound from receiver
Turn power switch on
Set receiver to function on ENV microphone
Turn up volume for ENV microphone
Recharge or replace batteries
Replace cords or button earphone2) No FM reception
Turn power switch on
Set transmitter to mic or mic/audio
Plug microphone into mic jack, not audio in
Set receiver to FM only
Insert oscillator of same color/code as receiver
Turn up FM volume control
Recharge or replace batteries in transmitter or receiver
Replace cords or button earphone
Try another receiver or transmitter3) Weak or Distorted Sound
Recharge or replace batteries
Replace cords, earphones, or hearing aid
Turn up volume controls
Clean wax from earmolds4) Static, Intermittent Sound or Feedback
Replace cords or microphone.
Clean battery contacts
Clean wax from earmolds
Check for excess ear wax
Check for properly fitting earmolds
Turn down volume controls5) Charger-No Lights, won’t charge
Plug charger into live wall socket
Change wall sockets
Place receiver and transmitter in charger properly
Clean charge contacts
Try different charge pocket if necessary.III. HOW TO MAINTAIN
1. Daily inspection - Visual and Auditory checks on a daily basis, however, _______ on daily basis not justified because very few aids were found to have problems during ________ testing that were not identified during visual/auditory testing.
2. Parent education- Diefendorf and Arthur (1981) found parent education _______ the number of malfunctioning aids significantly. Include anatomy, definition of hearing loss, audiogram, purpose and function of HA, range of acceptable HA performance, causes for fluctuation and remedies, and checking of batteries.
3. Inservice of teachers- Van Dyke (1982) gives outline but, lets make our own! Oh Boy! Amplification Inservice Outline
4. Child self monitoring-Elfenbein, Bentler, Davis, and Nieburh (1988) studied teachers of normal and HI kids in regular and summer programs. Set goal of catching malfunction when giving child HA w/dead battery or volume turned low. If child catches malfunction 10 times then reinforce.
INTERFERENCE Can use scanners to determine which channels have interference. Then switch to another channel.
SUMMARY
IDEAL FM CHARACTERISTICS AND
OPTIMAL HEARING AIDS1) The ideal transmitter would have variable transmitting channels, audio-input with talkover option, boom microphone, and low battery and no FM lights.
2) The ideal receiver would have dual-channel oscillators, audio-input and audio-output jacks, three signal options (FM, FM+ENV, ENV), and electroacoustic controls (SSPL90, tone, FM ratio).
3) The ideal battery would be user-selected, either nicad or alkaline so that electrical sources are not always necessary for charging
4) Most hearing aids with direct-input/telecoil capability have limited signal options when used with FM systems......usually FM only or FM + ENV but not both.
5) Most FM compatible hearing aids do not have directional microphones or two-year warranties, but about half have compression and offer direct-input as a standard feature.
6) Signal options are not readily determined from specification sheets and may require actual trial.
7) Special ordering certain signal options may alter other operation characteristics.
SELECTION PROCEDURES
1) A personal FM system is preferable is family and educational support are available to conduct regular listening checks. A basic FM system may be fit as the primary amplification.
2) There is less signal alteration with direct-input coupling than with neckloop.
3) Direct-input hearing aids with equivalent gain may produce different amounts of gain when used with an FM receiver set to a constant volume setting.
4) There is less generally less alteration of frequency response and less increase in equivalent input noise when using direct-input vs. neckloop coupling.
5) Use of neckloop coupling usually results in a reduction in low frequency gain and differences in signal strength depending on the head orientation.
6) The boom microphone is preferable because of the significant improvement in speech recognition and the stability of the signal despite head turns by the speaker.
7) The goal in fitting the FM system is to make speech audible without exceeding the child’s UCL. Both Telex and Phonic Ear have published fitting guides.
EVALUATION PROCEDURES
1) To perform auditory/visual checks, work with single units first and then add on components.
2) Electroacoustically evaluate components of FM systems including receivers, microphones, and neckloops.
3) Real-ear or electroacoustic measurements may be used to match the output of the hearing aid and the FM system at the eardrum.
4) It is difficult to evaluate behavioral thresholds with an FM system. Functional gain for the FM system will be lower than for the hearing aid because of difference in input levels to the respective microphones. Best to conduct behavioral tests with supra-threshold stimuli.
MAINTENANCE ISSUES
1) To conduct a thorough auditory/visual evaluation, check each component separately, ie. FM receiver as a body aid, FM receiver set to FM only, then personal FM system.
2) Perform baseline measures on each individual FM system according to your own documented procedures when it arrives from the factory. Conduct annual evaluations for comparison.
3) When monitoring a group of FM systems, select a control unit and evaluate the components by keeping all equipment constant except for the component of interest.
ie. to evaluate FM microphones, set up for testing the FM system in FM only mode and repeat the testing for each FM microphone while keeping the transmitter, receiver, cord, and button earphone constant.
4) Complete troubleshooting reports when there are problems so that efforts towards resolving the problem may be documented and conveyed to the manufacturer when sent in for repair.
5) When interference is noted, complete an interference report and request a scanner from the manufacturer to identify interfering channels.
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