Radio Frequency (FM) Units in the classroom
The FM works in conjunction with the child's hearing aid/cochlear implant to overcome two most important problems in the classroom:

1. Distance from the Speaker

With a hearing aid only, the amplification is optimal around 1 metre, and is reduced beyond this point. With the FM microphone on, the child can hear you anywhere in the room.

2. Background Noise

To a limited extent this is overcome by taking your voice directly to the hearing aid. However ambient noise near the FM microphone and near the child's hearing aids will still be amplified.

Things to be aware of when using an FM unit.

(a) Electrical appliances can interfere with the FM - those in and adjacent to the classroom.

(b) The FM can transmit up to 100 metres. This is important if there's more than one FM (on the same frequency) in the school or if you chat outside the classroom, your FM user may still hear you.

(c) The FM works as a walkie talkie, using radio waves, these can be blocked by furnishings in the classroom, e.g. metal chairs, etc. The room should be checked for blank spots.

(d) Computers could interfere with FM units. Aids on telecoil may pick up large amounts of interference due to the electrical activity within computers and similar equipment. The FM itself may be badly affected by high levels of static like noise. This will not normally occur, even if the child is right next to the computer, provided the transmitter and receiver are reasonably close e.g. 1--3 m. apart. However if the transmitter moves away or is turned off, the resulting interference is quite unacceptable.


When using an FM it is important to ensure that what the child is hearing is relevant to him/her.

  1. The FM is best used in a group situation/whole class setting, eg. Story-time, show and tell, instructions etc.
  2. Ensure that the FM is not in use when the teacher is talking with another student or group of students which does not involve the child with a hearing impairment. This external noise is distracting to the child.
  3. Where appropriate the microphone may passed to other students, eg when they are answering/asking a question in a group situation.
  4. To gain the best from your FM it is important that the microphone is properly positioned.

  5. The microphone should be no more than 10-15cms from the speaker's mouth and facing the speaker.
    Make sure that there is no jewellery, clothing, hair etc rubbing against the microphone.