table.main {} tr.row {} td.cell {} div.block {} div.paragraph {} .font0 { font:3.00pt "Arial", sans-serif; } .font1 { font:5.00pt "Arial", sans-serif; } .font2 { font:7.00pt "Arial", sans-serif; } .font3 { font:8.00pt "Arial", sans-serif; } .font4 { font:10.00pt "Arial", sans-serif; } .font5 { font:11.00pt "Arial", sans-serif; } .font6 { font:12.00pt "Arial", sans-serif; } .font7 { font:13.00pt "Arial", sans-serif; } .font8 { font:14.00pt "Arial", sans-serif; } .font9 { font:16.00pt "Arial", sans-serif; } .font10 { font:25.00pt "Courier New", monospace; } .font11 { font:7.00pt "Palatino Linotype", serif; } The original idea to increase the sound absorption of a ceing rte by using micro perforations cornes (rom China. As a resuit of a joint German-Chmese developmeftt programme lead by the Fraunhofer-hstrtute for Building Physics (Stuttgart), the reflned product is rtow available f rom OWA. The development of OWÀ perfofa contemporary ceiling tiles provides the spécifier with the opportunity to atla-n optimum sound absorption values and yet simul-laneously gwe the impression of a pJaint unperfor ated ceiing surface with a monolrthic type effect. Réverbération with and without holes. The Acoustic principle. The sound passageway through milions of < 0.5 mm diameter holes causes viscous friction at the hole edges and with rt the réduction of soutd energy Optimum sound absorption values can be achieved as the réverbération measurements show in the comparison of two tests tc\ a classroom with an OWAtectaperfora contract ceiling with and without ocopants The measurements were taken in a classroom measuring 10 x 7 x 3 mètres and shows the réverbération tmes recorded. The shaded area shows the parameters of the réverbération bmes laid down for an area of this type and size and corresponds to the conditions of standard lechnology. (see *o 'Buittng and room acousbcs' FasoW.Sonntag.Wmkler). The Test To prove the acoustic principle, a classroom was tint tcstcd with an OWAtecta plain un-perforaled meta! tite ceiling (1) and the reverterahon measured. In each case with and without the présence of students. Then, OWAtecta perfora ceiling Ules were insta/led (2) and tested under identical conditions. The perfora commercial tiles were punched with 40,000 micro holes per square mètre, a total of 2.8 million holes in the complète ceiling surface. Test result 1: The réverbération was represented with two curves, both ctearly laid over the values of an optimal réverbération time. Test resuit 2: Here, both curves lie in the area of the specified réverbération time with its optimal acoustic conditions. In each case independenl ot how many oeopfe were in the area. ■ t * 15- t \ m * * % L0- • c ** „ - - - 03- _1_l_ _1_1— _1—1_ 1 1 _1_1_ 121- :0û 10CC f Hcj 4000