Noise and Buildings
ONE
NE function of a building is to provide some protection against noise intruding from outside. This Digest is concerned with levels of intrusive noise to which buildings are commonly exposed, the desirable levels-in so far as these are known to which this noise should be reduced, and the way in which building planning and design can achieve these levels.
Effects of noise
Intrusive noise is most widespread in cities, and recent surveys have shown that traffic noise is frequently the predominant source; it also has the greatest effect on people, causing more disturbance both indoors and outside than any other noise commonly heard. It enters buildings chiefly via the windows, since even when closed these are normally the weakest points in the defence against external noise. The protection given by various kinds of windows in traditional buildings is reasonably well known, but with modern lightweight structures having large glazed areas the problem is greater and knowledge of the degree of protection is less definite.
Noise, or unwanted sound, has two principal effects: it may cause disturbance or annoyance, or it may interfere positively with some par- ticular activity. The
annoyance
caused. since it is subjective, varies widely from person to person, and depends not only on loudness and duration but on the information car- ried by the noise. Apart from any disturbance to sleep it may cause, noise, at the level normally encoun- tered. has no measurable effect on health. Any figures given in this Digest for the desirable levels to which intrusive noise should be re- duced so as not to cause annoyance are essentially estimates for average people. Interference with activity by noise, on the other hand, particularly with speech communication, can be described more precisely; for in- stance, the noise levels that disrupt direct speech, telephone conversa- tions or listening to reproduced speech from the radio (speech inter- ference levels) have been specified.
Noise which carries no meaning- ful information has the same effect whether originating from external sources or internally, i.e. from other rooms in the same or attached build- ings. 'Internal' noise can generally, given suitable consideration at the design stage of a building, be reduc ed to acceptable levels, using sound insulating and absorbing materials in the correct way.
Sometimes all the desirable measures for noise reduc- tion cannot be undertaken, for economic reasons or because they
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conflict with other functional re- quirements of the building. It would be impracticable to describe in detail all the various steps which could be taken for control of 'internal' noise in all kinds of buildings. However, if existing knowledge of the prin- ciples of sound insulation and ab- sorption were utilised to the full, there would be substantial reductions in the level of internal noise for a great
number of people. Some aspects of this subject have been described in Digests 36, 88 and 89 (first series) and in the B.S. Code of basic data for the design of build. ings, CP.3, Chapter III. 'Sound in- sulation and noise reduction'. This Digest therefore, is more concerned with defence against 'external' noise.
External noise climate
Most of the buildings for which some defence against noise is need-
L-Lorry
B-Bus
C-Car
M/C-Motor cycle d-Car door
slamming
ed, over and above that given by single openable windows, are in towns. Surveys have shown that in urban areas noise from road traffic is predominant, i.e. it is the noise most frequently heard and often pro- duces the highest noise levels. It has also the greatest effect on peo- ple, causing more disturbance to them whether indoors or outdoors than any
other noise commonly heard.
There are some situations of course, in areas of heavy industry or near particularly noisy operations where other sources may predo- minate. It is impossible to estimate levels for these special cases. At other times, temporary sources of noise such as building operations or road works may be introduced into a locality. The noise levels produc- ed by plant used in building con- struction and roadworks, including
20 YDS FROM BUSY MAIN ROAD
NOISE
LEVEL
OBA
90
80
70
-60
A
M/C
C
50
40
QUIET SQUARE, DISTANT TRAFFIC
L
B
d. d. c
C
́NOISE
90
80
LEVEL 70
d BA
60
50
FIG. 1. Relative noise levels of different vehicles.
40
10 20 30 40 50
60
10
20 30 40 50 60
TIME
SECONDS
THE HONG KONG & FAR EAST BUILDER-VOLUME 18. NUMBER 4
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