University of Edinburgh

Learning Support Assistants working with Deaf young people in Schools and Colleges

Presented on Wednesday 9 December 2009

The Hearing Aid and Radio Aid

Joe O'Donnell, Educational Audiologist, Donaldsons College

The Hearing Aid Complex

the hearing aid complex

How it works

how it works

Microphone - sound energy to electrical energy
Amplifier - signal shaped and processed
Receiver - electrical energy to sound energy

Digital Hearing Aid

Hearing aid users need good Acoustics

  • Reverberation time: 0.4 secs across all speech frequencies
  • Background noise (unoccupied classroom): 30 dB(A)
  • Signal-to-noise levels: +15-20 dB

All hearing aid users should have access to a low reverberant, low noise environment when using spoken communication


  • Distance - Ideal distance is 1m from hearing aid. As move further away speech signal loses intensity. The weaker the signal the less effective the hearing device will be.
  • Background noise - Classrooms are noisy places. When noise as strong or stronger than speaker's voice, it is much more difficult to understand what is being said. Microphone picks up all sounds in the environment and passes them onto the student.
  • Reverberation - All sounds reverberate (bounce off) surfaces within a room. Sound from the speaker bounces off walls and ceilings and reaches listener at different times causing an echo effect.

The Radio Hearing Aid: is used to address the problems of hearing speech through a hearing aid due to Distance Background Noise and Reverberation.

Main Parts

  • Microphone
  • Transmitter
  • Receiver
  • Connection to the hearing aid: either by wires and 'shoes' or loop

How it all works

  • Microphone - Sound energy changed to electrical energy. Short microphone distance gives priority to teacher's voice.
  • Transmitter - Electrical signal placed onto radio signal and sent out by the transmitter
  • Receiver - Receives the radio signal and electrical signal
  • Connections - Carry electrical signal to the hearing aid
  • Hearing aid - Signal processed and shaped by hearing aid. Processed signal changed into sound energy and passed to the ear of the student

Advantages of FM System

  • Short microphone distance - priority given to teacher's voice over background noise
  • Student gets more of the signal than the noise: +15-20 dB
  • Direct link with the student while signal is transmitted
  • Teacher able to move freely round the class
  • Student can choose to have only FM mic live

Disadvantages of FM System

  • No student to student FM link
  • Transmitter must be turned off when information not relevant to the student is being given
  • Signal student receives gives no information on direction or distance of speaker

Points to Remember

  • FM microphone must be close to speaker's mouth (6 8 ins)
  • Minimise noise in the environment
  • Switch transmitter on when talking to deaf student individually or in a group
  • Switch transmitter off when speech not relevant to deaf student
  • System must be checked before use

The radio aid is not magic. It only works effectively for the student when it is managed appropriately.


Hearing Aid, Earmould and Radio Aid Checks

Hearing Aid Checking Kit

This should include:

  • A stetoclip (with earmould connector and an attenuator)
  • Spare batteries
  • A puffer
  • Sterile wipes

The BTE Hearing Aid

bte hearing aid

BTE Checking Procedure

  • Detach the earmould from the hearing aid
  • Switch hearing aid off and turn volume down
  • Attach the stetoclip to the tone hook
  • Place stetoclip on ears
  • Switch hearing aid on and turn up to user volume
  • Hold hearing aid in front with microphone facing you
  • Clearly and without exaggeration say the 5 Ling sounds oo ah ee sh ss
  • While talking, gently press the casing, move volume controls and switches.
  • Visually inspect casing for cracks or damage

Listening Through the Earmould

If aid is working properly, re-attach the earmould and connect the earmould to the stetoclip. You will need a special bell shaped attachment on the stetoclip to carry out this check. Now follow listening check procedure from 3-7. This is an important check as any problems identified will be directly related to to the earmould or its tubing. Remember to wipe the earmould and earmould attachment with a sterile swab before and after use to prevent any spread of infection.

Checks When Hearing Aid is Worn

  • Is the microphone position appropriate?
  • Is there feedback from the hearing aid?
  • Is earmould correctly inserted in ear?

Position of Hearing Aid Microphone: At top of ear, facing front

What to Do If There Is a Problem

  • Change the battery and retest
  • Check hearing aid without tone hook
  • If hearing aid working, puff out tone hook and retest
  • If hearing aid still not working seek a replacement

Earmould and Tubing Checks

tubing checks

Visually inspect tubing and use puffer to remove any moisture

Inspect earmould for damage/cracks.

tubing checks

Inspect earmould tip (part that goes deepest into ear) for wax blockage. If wax in tip then wash out with hot soapy water and puff out tubing to dry

blocked earmould

  • If any damage then a new earmould should be requested
  • If tubing is discoloured or hard then new tubing should be obtained

Radio Aid Checks (Ear level system)

  • Check that the BTE to be used with the FM system is working
  • Attach shoe to hearing aid and attach receiver to shoe
  • Switch receiver to two green dots.
  • Switch hearing aid on and attach to stetoclip Radio Aid Checks (Ear level system)
  • While listening, have other teacher, wearing transmitter appropriately, turn it on and speak
  • Move around class listening to quality of sound coming from transmitter