Page 65 - samyn_ebook2

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fg 10
roof without sound absorption
cover with a sound-absorbent roof
cumulative distribution of noise on the platforms
sound pressure level in dB (A)
the passing through of a train is increased. For example: without soundproofing,
only 10% of the platforms register a sound pressure level 10 dB (A) lower than the
one measured with a passing train, in the case of a soundproofed roof, up to 50% of
all platforms register values 10 dB (A) lower than with a passing train.
Additional elements (not included in the competition design)
The noise levels occurring during the passing of a train can also be lowered by
applying a feweffectivemeasures, which are not included in the competitiondesign,
but which we consider essential. They are not in conflict with the competition
design in any way.
(1) A soundproofing cover or niche alongside the sides of the platforms. These sides
can easily be soundproofed and are very effective because the sound absorption
occurs directly at the main source of the noise: the contact point between wheel and
rail.
(2) In the same way, a low sound screen could be placed midway between two train
tracks. Their height can be reduced, so that the view of the passengers in the train
is not blocked in any way. Still, an important insulation of the wheel-rail contact
noise would be achieved. The sound screens can be relatively low in cost since their
reduced height does not imply severe structural forces, and consequently no heavy
construction or foundations. These sound screens can be supplied as (standard)
perforated steel panels, matching the roof cover of the competition design.
(3) The competition design also proposes to soundproof the wall that sections off
the freight rail tracks on the side of the station for at least 50%. This soundproofing
can be placed in the width of the wall, as a top coat of porous concrete, similar to the
material used in some sound screens. The final design proposes a wall in perforated
steel which absorbs noise in a similar way.
fg 9.1 The cover without soundproofed roof.
fg 9.2 The cover without soundproofed roof (including the platform
furnishings of the fnal design)
fg 10 Cumulative dispersion of the sound levels on the platforms.
Both graphs indicate the percentage of the foor area (Y-axis)
where a given noise level (X-axis) is not exceeded.
Remark: the absolute values of the sound levels are insignifcant,
but the relative values (differences) are correct.
fg 9.1 fg 9.2