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:
|Noise Source||Possible Solutions|
|Scraping chair and table legs||
|Clattering pens and pencils||
|Computers and printers||
|Aquarium pumps, gerbil wheels etc|
|Workshop machinery: lathes,
sewing machines, foodblenders etc
|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||
|Radiation from computer monitors||
|Mobile phone masts? [controversial]||
|Cochlear implant processor link to radio aid||
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.
County Co-ordinator, Surrey Physical & Sensory Support Service
BATOD Magazine, January 2001