BATOD
The British Association of Teachers of the Deaf
Promoting Excellence in Deaf Education

SOUND TREATMENT FOR CLASSROOMS

There are 4 main aspects to making a comfortable and effective listening environment in any room:
  • reducing reverberation
  • reducing internal noise
  • reducing external noise
  • ensuring speakers are heard by all.

Reducing reverberation

Hard surfaces tend to reflect rather than absorb sound, causing reverberation. Excessive reverberation reduces the clarity of speech, particularly for hearing aid users. An optimum reverberation rate for hearing aid users is 0.4 of a second.

Objective assessment of reverberation rates can be difficult, but it can be done subjectively by hearing aid users themselves. A theoretical reverberation rate can be calculated [may need an acoustic engineer!] by taking into account room size and the acoustic properties and dimensions of the internal surfaces, eg walls, ceiling, floors, windows.

The most effective single adaptation to reduce the reverberation rate is to fit totally sound-absorbent cladding to a [low] ceiling. In this way, rooms such as science labs and technical workshops can be brought within optimum rates without fitting carpets or curtains, which would be unsafe or impractical.

Where carpets and curtains or soft blinds can be fitted, they assist sound absorption and have other benefits such as internal noise reduction [carpets] or reducing glare [curtains or blinds].

Wall cladding is not always cost-effective, if walls are used for display purposes: putting sheets of paper on soft wall boards or tiles counteracts the sound absorption.

Reducing internal noise Excessive noise [ie unwanted sounds] affects all people’s [but especially hearing aid users’] ability to pick out the ‘signal of interest’. The principal source of internal noise in classrooms is the children! Avoid the temptation to raise your voice level above the noise. Noise management should be part of any school’s Behaviour Policy and everyone’s practice. ‘Open plan’ environments pose enormous challenges.

Non-human noise comes from an increasing variety of sources. Wherever possible, place hearing-impaired pupils at a distance from unavoidable sources of noise. It is particularly important that pupils with unilateral hearing loss don’t sit with their hearing ear towards a source of noise.

Reducing external noise

Sources of noise include:

  • classes and grass mowers on playing fields
  • traffic: road and air; trains
  • classes in neighbouring rooms [especially assemblies and PE lessons!]
  • machinery in adjacent rooms.
Reducing external noise may be through:
  • reducing the noise at source where possible
  • preventing the noise entering the room with double/secondary or even triple glazing, cladding, heavy duty doors and frames, or sometimes simply closing windows and doors!
  • timetabling lessons for hearing aid users to avoid vulnerable rooms or peak times for noise.
Noise Source Possible Solutions
Scraping chair and table legs
  • Carpets
  • Rubber tips on chair and table legs
  • Pupils lift rather than drag chairs and tables!
Clattering pens and pencils
  • Pupils manage the noise
  • Soft pencil cases
  • Table-top pencil holders lined inside and on the bottom with felt
Computers and printers
  • Pupils manage the noise
  • Soft pencil cases
  • Table-top pencil holders lined inside and on the bottom with felt
Heaters
  • Service and maintain to keep noise to minimal levels
  • Fit new, silent heaters
Aquarium pumps, gerbil wheels etc
  • Buy a new pump
  • Feed Ritalin to the gerbil
Workshop machinery: lathes,
sewing machines, foodblenders etc
  • Clad or screen where possible
  • Service and maintain to keep noise to minimal levels
  • Switch off at every opportunity
  • Hold plenary/group sessions in a separate area if possible
There are also electrical sources of noise that are undetectable or unnoticed by non-hearing aid users, but can cause interference in hearing aids, radio aids or cochlear implants

Interference Source Possible Solutions
Old strip lighting
  • Replace with high frequency/noise-suppressing strip lights
Radiation from computer monitors
  • Fit anti-static screens
  • Buy new ‘low radiation’ monitors
Mobile phones
  • Confiscate
Mobile phone masts? [controversial]
  • Don’t site near school
Cochlear implant processor link to radio aid
  • Consult CI team re updating the processor

Ensuring speakers are heard by all

Projecting voices so that they carry throughout a classroom of usual size inevitably means raising them if even hearing pupils are all going to hear. Using a soundfield FM system will ensure that all pupils hear the teacher’s voice and the teacher can use conversational levels. However, in class discussions and question and answer sessions, unless the microphone is passed around, others’ contributions will need to be relayed by the mic wearer. The same principle, of course, applies to using radio aid receivers and transmitters.

All pupils ‘hear better’ if they can see the speaker’s face clearly. As well as helpful positioning of speakers and listeners/ watchers, make sure that overhead lighting is adequate to preclude strong shadows and that glare is avoided.

Where curtains or blinds can’t be fitted, glare from bright sunshine can be reduced by using sun-filtering film on windows.

Finally

How can things like this be funded? If you are in a mainstream school, try applying for funding through the Schools' Access Initiative. This scheme is designed 'to improve access in mainstream schools for pupils with disabilities [including physical and sensory disabilities] … not only to the building but also the curriculum and to participate in the social life of the school.' Contact your LEA Planning & Development section [or similar] for further information.

Pauline Hughes
County Co-ordinator, Surrey Physical & Sensory Support Service
BATOD Magazine, January 2001