June_1970 — Page 12

(1)

A

(ii)

(iii)

(i) Little or no noise shielding

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(ii) Roadbed below grade. Considerable improvement over (i) but its effectiveness is limited by the farthest lanes of traffic. Could be improved by adding on earth mound, shown dotted, or by a wall.

(iii) Building as an effective sound barrier.

g) Shrubs and trees can be used to some effect for noise attenuation. Absorbent surfaces such as grass, gar- dens and trees considerably reduce reflection and reverberation of noise.

*2*6**

4 db Loss

Hedges, shrubs & trees can have some value.

h) Interior courtyards are general- ly very noisy due to reverberation. Leaving one end of the court open reduces the noise level appreciably. Breaking up the surfaces and making opposing surfaces non-parallel also helps. Sealed windows on the court side helps stop noise in both directions.

Internal noise considerations

A responsible and experienced draughtsman can prepare drawings, details and specifications from an architect's sketches provided he has the tools for analysis handy in the form of check lists, standard details and manufacturers' brochures. Acous-

tical analysis is no different and is in fact only another item in planning consideration.

Some common sense do's and dont's for internal acoustical planning

are:

a) In initial planning, rate the spaces in your list of accommodation into at least four categories of acous- tical design.

I. Noise sources equipment rooms, lifts, trucking bays, typist pools, kitchen, etc.

II. Dead spaces

archives, etc.

storage rooms,

III. Occupied areas with average noise control requirements.

IV. Occupied areas with above average noise control requirements.

b) Large equipment installations should not be installed under or over occupied office or flat space or under an auditorium. Technology can isolate noise sources adequately, but the space and cost required to handle the problem is much greater than if the noise sources are located adjacent to non-critical occupancy or dead space.

c) Consider carefully the location of conference rooms, VIP suites, class- rooms or any enclosed space requiring special noise control attention, as it is obviously less costly to locate in a quiet zone than to build sophisticated noise protection around them.

Doors

d) When considering the overall transmission of noise through walls, doors are the weak link. The single, most important factor in improving

door performance is air-tightness.

A door is primarily a three-point suspension unit, namely two hinges and a single latch, all loosely fitted. Where above-average noise protection is required it is essential that the doors fit tightly to the jambs and remain there.

Three items should be taken into account: Location, construction and installation.

I. Location. Doors should not be placed opposite each other. They should be staggered, especially across corridors and hallways, to give noise

туру

POOR

ACOUSTICALLY TREAT CORR.

Door location

ملا

BETTER

the longest distance to travel and a better chance to be diffused and ab- sorbed in the floor and ceiling mat- erials. Double doors are always more of a problem than single doors and before planning to locate double doors within areas requiring above-average noise protection the architect should have very good reasons for not using a 3ft. 6in. or 4ft. single door.

II. Construction. Most hollow core wood doors are not stable and will warp and/or twist making edge and floor sealing very difficult. Where above average noise protection is re- quired always employ solid wood core doors or 'acoustical' doors.

12

POOR

[GARACE

GOOD

BETTER

Far East BUILDER, June 1970