Exterior noise

Recommendation 71
After deciding about the location of the school, take satisfactory measures towards sound isolation around walls, windows and other façade openings

Chapter (theme)
Architectural spaces (sound / noise and acoustics)

Because of
sensory sensibilities (sound), weak powers of imagination, disturbed perception

In order to
lessen disturbance of the learning situation through noise.

Elaboration
As discussed rather extensively in the theme noise and acoustics, noise comprises one of the, if not the most important sensory challenge, which is particularly present in schools. For further reference also see the introductions to the other recommendations under this theme about interior noise, stairwell noise and reverberation in the classroom.

Noise from outside usually is traffic noise (airplanes, motor vehicles, trains and trams – in that order), although other extraneous noise sources may be relevant as well. Understandably, extraneous noise is one of the decisive considerations in the choice of a suitable school location. (See recommendation 4.)
In The Netherlands – and similarly in other western countries – one is obliged to present a noise analysis report in order to receive a building permission. In the Dutch case this report must prove that the environmental noise levels are in accordance with the conditions of the Noise Pollution Law and the Dutch version of the U.S. Building Code or the British Building Bulletin pertaining to schools. For a broad understanding: interior noise limits have to be below 40dB; since the minimal soundproofing of a new building is presumed to be 20dB, the extraneous level may be 60dB without extra soundproofing measures. (See here for some of the technical background.)
An extensive study of 142 London schools found, however, that these standards are very often exceeded. It showed in 86% of these schools the average extraneous noise level was 57dB. Obviously an average so close to the maximum implies it must be exceeded in a significant number of instances. In order to reach acceptable interior levels much sound insulation remains to be done.

An ameliorating finding of sorts must be mentioned here too. That is that extraneous noise was often drowned by the internal noise of students themselves. The nuisance of external noise only manifested itself when the class was unusually quiet.
Nevertheless extra efforts are necessary to at least approximate a noise impact from external sources in accordance with the regulations. Even more so when schools are built  for autistic or other students who have a heightened sensitivity to noise, since the regulations and the available research are aimed at average students.

Although structural measures and the materials to be employed are the competence of the architect, from the literature, a limited number of suggestions can be drawn:

• Connection of door and frame, sealing of doors
• Double glazing / additional window at 4 inches
• Ventilation grilles with sound attenuation
• For a detached house a cavity of at least 8 inches
• The use of insulating building blocks such as Insulated concrete forms (ICF’s) for exterior walls.

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