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ACOUSTICS
CONFERENCE HALLS ACOUSTICS orthogonal lines also covered in felt (see “Halls felt ceilings”
p. 116 and “The 15 x 15 cm square” p. 128). Regardless of the
Conference halls acoustics aesthetical and constructive aspects mentioned in those two
The treatment for acoustic correction of a hall means to articles, perforated steel provides a better absorption coefficient
than perforated wood with less perforation, therefore with more
carefully “dose out” the acoustic characteristics for each of the rigid panels.
finishing materials and their implementation to optimise the
acoustic reaction of the ensemble. Focalisation
Great conference halls have elliptical shape. This rather
Conference hall acoustic performances are assessed with
respect to the criterion of understanding and talking. Far from unusual shape results from the architectural synthesis properly
extreme values of total human hearing acuteness, that criterion speaking, which produced the lantern and integrates many
essentially considers only the frequency band comprised aspects:
between 250 and 2,000 Hz. – reasonable structural morphology, compact hull and no
concentration of constraints where the great spans are taken
The main performance to be secured is the “reverberation up by floors with radiating ribs, without superfluous exploits;
time” (RT), set between 0.75 seconds for small rooms and – a whole facade, free of facets and angles, symbolising
1.2 seconds for big halls by acoustic common practice. European unity;
– soft integration of curves within a densely straight
At the study stage, a predictive calculation is made starting environment;
from a hall all of whose walls would be entirely reflective. – egalitarian conference tables, without any hierarchy between
The volume determines the RT value (way too high of course). seats;
Next, the acoustic absorption values for the various walls are – optimal visibility of the speakers by interpreters placed all
introduced into the calculation, except for vertical walls. Each around them.
of those walls (furniture included) provides its own contribution,
big or small, to reducing RT in each frequency band. From a strictly acoustic viewpoint, this shape has the
disadvantage of focalisation: sounds starting from one of the
The absorption “balance” is brought about by opaque walls, ellipse’s foyers are reverberated on the side of the other foyer
covered in felt on perforated metallic chambers; the calculation in a concentrated fashion. But that default is corrected by wall
gives a theoretical absorption curve to be respected. acoustic absorption, completed with interpretation booth
window inclination. Sound moving horizontally is thus directed
Acoustic absorption curves are imposed upon the company upwards to the multiple absorbing surfaces. The potential
in charge of the works but the resulting reverberation time focalisation, which would occur at the interpretation booth’s
too is contractual and it will have to justify it by calculations upper level height, would not disturb the occupants.
and onsite tests. This approach is a guarantee that the result
is consistent with the expectations, keeping unavoidable gaps A likely acoustic advantage inherent to elliptic tables exists:
between theoretical calculations and practical implementation that shape precisely provides the shortest distance between the
into account. It also lets variants be taken into consideration, orator and his/her listeners as well as the best visibility between
constructive solutions failing to comply with specifications but individuals, thus enhancing understanding, including through
deemed equivalent by all the parties. non-verbal language.
Thus, the ceiling, which was to be layout perforated wood Still aiming at enhancing understanding and talking,
panels initially following elliptical lines and covered in felt, requirements were imposed for the ventilation system in order
was made with layout perforated steel chambers following to limit background noise in the halls. Wall acoustic absorption
also causes a reduction in the transmission of “parasite” noise
generated by side conversations by assembly attendees.
