Page 61 - samyn_ebook2

59
3.3 Acoustic study
The design aims to provide optimum acoustic comfort on the platforms and their
surroundings. This includes the reduction of the influence of unwelcome sources
of noise as well as ensuring comfortable speech intelligibility levels. This study
clarifies both these acoustic aspects of the design.
The first part indicates which measures were taken to minimize the inconvenience
of unwelcome sources of noise. A geometric calculation model of the covering and
the station environment was used to investigate how noise levels on the platforms
and their environment can be influenced. A number of typical sound sources are
considered: a line source and a point source located in different places.
The second part investigates how comfortable speech intelligibility levels can
be ensured on the platforms. Aspects such as the requirements that need to be
fulfilled, which public address system provides adequate speech intelligibility
levels, and in which way this equipment is to be incorporated in the architectural
plan are investigated.
Noise control
The covering transforms a large section of the platform area into an enclosed space.
This implies that inside noise levels are higher than those in open space. This section
examines how this amplification can be reduced, and how possible inconveniences
for commuters and neighbours can be avoided. The sound dispersion is simulated
using a geometric model of the station district. The geometric plan includes the
station buildings, the platforms and railroad tracks, and the main elements of the
platform cover and the platform furnishings. Sound sources can be randomly placed
within the model. The sound pressure levels can be calculated for a large number of
positions underneath the cover or its surroundings.
The following analyses can be executed by means of this model:
- The degree of noise level amplification under the cover, compared to an
“ideal” situation of noise dispersion in open air, without cover.
- The influence of basic architectural features on the noise level under the
cover: the height of the cover, the shape of the cover, the level of noise
absorption under the cover, the platform furnishings.
- The effect of the cover on the level of ambient sound dispersion.
These analyses are explained in detail in the next paragraphs.