Description of the acoustic characteristics of ETFE roof structures
Invited paper
Level Acoustics & Vibration
Tuesday 2 june, 2015, 16:40 - 17:00
Auditorium 2 (592)
Abstract:
Among architects, there is a preference for lightweight and transparent
envelopes, also as a facade/roof for buildings with noise-sensitive areas, such
as working spaces. ETFE cushions have the qualities that satisfy these wishes
and are therefore in high demand with architects. The realization of sufficient
sound insulation for these kind of envelopes, however, is a huge challenge.
Describing the expected acoustical behavior of roof buildups with ETFE cushions
is just as challenging.
Because of our involvement in the design of a university building with working
spaces under an ETFE roof we developed roof solutions aiming at sufficient sound
insulation for outdoor noise and rain noise. This has resulted in a double roof
structure with different types of ETFE elements (single and multi-layered
cushions). In order to get a grip on the acoustical behavior of (double) ETFE
structures we performed measurements on various buildups in our laboratory.
Based on the results and previous research the acoustical behavior, e.g.
excitation mechanisms and sound transmission, of double ETFE structures has been
described, both for traffic noise and rain noise. The descriptions were applied
during the development of roof solutions for the university building mentioned.
Calculation results have been compared with results from measurements on a
mock-up of the roof, performed in our lab. The overall acoustical behavior of
the roof has been studied, such as sound insulation and sound intensity level
due to rain. Besides, several parameters, like loss factor and radiation
efficiency, and the modal behavior have been looked at in detail. The modal
behavior has been studied with FEM. The acoustical behavior has also been
visualized by sound imaging measurements. Rain was produced by a rain generator
with specs according to EN-ISO 140-18. The results correspond well.