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Design Note 25: Lighting and Acoustic Criteria for the Visually Handicapped and Hearing Impaired in Schools; DES 1981.

The purpose of Design Note 25 is to dispel some misconceptions and provide lighting and acoustic criteria which should be adopted when designing for the visually handicapped and persons with impaired hearing.

The design note has been written as the visually handicapped and hearing impaired have a wide range of needs and this requires consideration in design.

The design note refers to both disabilities as visual and hearing impairment are similar in design terms. In addition to general guidance and the activities to be considered within spaces, the document includes the following:

Visually handicapped

  • Lighting
  • Acoustics
  • General physical requirements
  • Special optical aids and local lighting.

The hearing impaired

  • Lighting
  • Acoustics
  • General requirements
  • Provision for group aids.

Notes of Caution:

The principals are defined, but design teams are referred to work being done by the Royal National Institute for the Deaf and by the Vision and Lighting Research Group of the University of Loughborough.

Further Commentary:

Visually Handicapped

The effects of most visual handicaps are minimised with a high level of lighting, however, certain handicaps are exacerbated by high levels of lighting. To reconcile the two, lighting which does not markedly differ from standard solutions should be provided. However, excessive glare and contrasts are to be avoided. Individual local lighting may be valuable.

Lighting

A good variety of lighting and colour is important. Specific lighting levels are defined in this section.

Additionally, sun and sky glare can be dealt with in various ways, via blinds, curtains or architectural solutions.  It should be noted that sky glare can occur at all orientations. Overhangs can reduce the visible area of the sky, reducing glare and improve contrast grading. Landscaping can also perform a similar job.

Harsh contrasts and mirror-like reflections must be avoided and lighting with a strong vertical component (a large proportion of bright light shining near horizontally into the face) should be avoided.

Demonstration areas must be well-lit without reflected highlights and with good grading to the surroundings. The conventional demonstration area being located on an end wall with windows to one side is still a good design solution.

Acoustics

Normal building surfaces will usually provide enough reflected sound. Acoustic liveliness is the aim, but not too lively or the reverberation time too long. Other building elements are reviewed in this section.

General Physical Requirements

For safety reasons, the following should be considered:

  • Avoid projections between head and hip level;
  • Handles and push plates should be mounted at a consistent height;
  • Changes in level must be identified by, for example, floor finish, changes in colour and lighting. Colour can have a greater effect when properly lit than any amount of lighting on an ill-defined space; and
  • Good definition is required at moving parts of machines.


Special Optical Aids and Local Lighting

Older children should have the freedom to use and adjust local lighting. Adequate provision of socket outlets is necessary for visual aids.

Hearing Impaired

It is wise to eliminate as far as possible unwanted noise, especially mechanical plant, and reduce the reverberant level to the minimum.

Try to ensure that face-to-face situations can be maintained in craft and other practical lessons, ie avoid, where possible, situations where a person with a hearing impairment will have their back to the teacher. Where this is unavoidable, in emergency situations, warning lights will alert everyone of danger.

Various induction loops are discussed in this section.

Lighting

Good lighting which avoids shadows on the face and neck, together with good daylight distribution will give reasonable conditions. Lighting quality is important for lip reading which requires good view of the neck and face.

It is important to avoid excessive contrasts and glare. Additionally, dim-out rather than black-out facilities are desirable at the windows.

Acoustics

Reverberation times and background noise levels are discussed in this section.

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