expressed in dB(A), which are likely to be acceptable for a number of typical situations.
There are, of course. many other situations for which desirable noise levels might be quoted; values for most of these can be inferred from comparable situations in Table 3.
Insulation requirements
From the data given in Tables 1-3. a knowledge of the spectra of traffic noise and the insulation curves of different windows, the kind of wind- OWS necessary to achieve any of these desirable levels in differing external noise climates can be deter- mined. The requirements are work- ed out for a number of cases in Table 4.
These requirements are based on noise levels which are exceeded for 10% of time. If in certain cir- cumstances peaks lasting for a longer proportion of time can be tolerated then the requirements are obviously less stringent.
Table 3
SUGGESTED NOISE LEVELS
Situation
1. Large rooms for speech such as lecture theatres.
dB(A)
large conference
rooms
or council chambers
30*
2. Bedrooms in urban areas
35
3. Living room in country
area
10
in suburban
area
45
in busy
area
50
in busy ur-
ban area
50
4. School classroom
45* 5. Private office (executive) 45---50* 6. General office
55--60*
* Values based on speech interference levels
Some design problems
When the external windows of a building are sealed as a protection against noise. ventilation by this means is impossible. This may be acceptable in cases where there are
134
Table 4
WINDOW INSULATION REQUIREMENTS
Type of situation (see Table 3)
AIB
C
Noise climate
D
E
FIG
Light
Type of window
1. Lecture theatres,
etc.
Double
Double
Sealed
Heavy
Sealed Light
2. Bedrooms
Double
Double
Sealed
Sealed
Openable
Heavy
Light
3. Living rooms
Sealed
Sealed
Sealed
Openable
Heavy
Light
Light
Light
Openable Light
4. Classrooom
Double
Sealed
Openable
Openable Open
Light
Light
Light
5. Executive office
Sealed
Sealed
Openable
Openable
Open
Heavy
Light
Light
Light
6. General office
Openable Light
Openable Light
Open
Open
satisfactory
alternatives, but
even
these may be inadequate where there is an apprecible thermal gain in fine weather. In this case either the windows have to be opened in extreme circumstances or some form of artificial ventilation must be pro- vided. In the first case the desired noise protection is not being main- tained. and the method of sealing may become inefficient with repeat- ed opening. On the other hand. ar- tificial ventilation for a complete building adds appreciably to the initial cost, and it may not be prac ticable to install it in an existing building. The problem is further accentuated where full air condition- ing, including cooling in summer, is envisaged. There are methods of ventilating individual rooms using units which draw fresh air from out- side through
noise-attenuating duct equivalent to the insulation of a sealed double window. but the normal axial fans fitted in exterior walls or windows provide no such attenuation and are effectively a small area of open window in the outside wall.
a
There are various ways of plan- ning the layout of new buildings to get maximum noise protection. for example by using perimeter corri- dors, but these solutions may them. selves introduce new problems such as the provision of adequate natural
to
lighting. The final design has balance the relative advantages of these various factors. One conse quence of good external insulation is that internal noise becomes in- creasingly important, and internal partitions having more effective in- sulation are also needed.
In particular cases where the ex- ternal noise climate is not due to traffic but to sources such as indus. try, individual measurements may be needed to assess the insulation requir ed. There are methods of determin- ing the likelihood of complaint about industrial noise from nearby resi- dents, using comparatively simple. measurements. The levels predicted by such methods are, however, like- ly to be higher than the values sug gested in Table 3. since a desirable level is essentially lower than which is just likely to cause com- plaint.
one
The noise climates with traffic as the predominant source are based on measurements in built-up areas. The construction of new trunk roads and motorways is posing similar traffic noise problems but the noise levels different of fast moving traffic at densities may differ significantly from the values obtained in towns.
Prepared at the British Building Research Station, Garston, Herts, Crown copyright.
THE HONG KONG & FAR EAST BUILDER-VOLUME 18, NUMBER 4
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