Unknown BRITISH STANDARD BS EN 12354 6 2003 Building Acoustics — Estimation of acoustic performance of buildings from the performance of elements — Part 6 Sound absorption in enclosed spaces The Europ[.]
BRITISH STANDARD Building Acoustics — Estimation of acoustic performance of buildings from the performance of elements — Part 6: Sound absorption in enclosed spaces The European Standard EN 12354-6:2003 has the status of a British Standard ICS 91.120.20 12&23 80 : equations B.4c These type of predictions can also be applied to multi-layered absorbing elements or absorbing materials backed by an airspace; see the Bibliography [4] 16 EN 12354-6:2003 (E) Annex C (informative) Sound absorption of objects For some common objects and configurations of objects the equivalent absorption area and sound absorption coefficient measured in accordance with EN ISO 354 are given in Tables C.1 and C.2 These values can be considered as typical values Table C.1 — Typical values for the equivalent absorption area for some common objects Equivalent absorption area Aobj Object in octave bands, centre frequency in Hz 125 250 500 000 000 000 single chair, wood 0,02 0,02 0,03 0,04 0,04 0,04 single chair, upholstered 0,10 0,20 0,25 0,30 0,35 0,35 single person in a group, sitting or standing, per m2 area; typical minimum 0,05 0,10 0,20 0,35 0,50 0,65 single person in a group, sitting, per m area; typical maximum 0,12 0,45 0,80 0,90 0,95 1,00 single person in a group, standing, per m area; typical maximum 0,12 0,45 0,80 1,20 1,30 1,40 NOTE These data are based on publications used in Austria, Denmark and the Netherlands Table C.2 — Typical vales for the sound absorption coefficient for some common specified arrays of objects Sound absorption coefficient α s Array of objects in octave bands, centre frequency in Hz 125 250 500 000 000 000 chairs in a row at 0,9m – 1,2m; wood/plastic 0,06 0,08 0,10 0,12 0,14 0,16 chairs in a row at 0,9m – 1,2m; upholstered; typical minimum 0,10 0,20 0,30 0,40 0,50 0,50 chairs in a row at 0,9m – 1,2m; upholstered; typical maximum 0,50 0,70 0,80 0,90 1,0 1,0 persons sitting in a row at 0,9m – 1,2m (audience); typical minimum 0,20 0,40 0,50 0,60 0,70 0,70 persons sitting in a row at 0,9m – 1,2m (audience); typical maximum 0,60 0,70 0,80 0,90 0,90 0,90 children in a hard furnished class room, per m2 area 0,10 0,20 0,25 0,35 0,40 0,40 NOTE These data are based on publications used in Austria, Denmark and the Netherlands 17 EN 12354-6:2003 (E) Annex D (informative) Estimation for irregular spaces and/or absorption distribution D.1 Introduction If the enclosed space has a non-regular distribution of absorption, has irregular shapes or is filled to a large extent with machinery and equipment, the prediction of reverberation time according to the calculation model in clause can either be incorrect or irrelevant This annex indicates possible means of improving predictions in such situations The two main situations considered are (a) rectangular spaces with irregular absorption distribution and (b) irregularly shaped spaces, either as a result of the design or resulting from filling the empty space with a large number of objects (object fraction well in excess of 0,2) D.2 Irregular absorption distribution An essentially rectangular space with irregular absorption distribution is quite common In many offices absorption is only applied to the ceiling, all other surfaces being fairly reflective Though various proposals have been presented in literature to deal with this situation, none of them seems to work adequately in all situations A reasonable solution is to divide the sound field into parts that graze the different surfaces and a part that is non-grazing [5] The different effect of absorbing materials for these different sound fields and the effect of diffusing elements of mixing the sound fields is taken into account by considering the balance of power between the sound fields In this annex a practical estimation is provided, based on that model but making use of absorption data measured in accordance with standard methods Figure D.1 — Definition of dimensions for a rectangular space The room dimensions are defined as in Figure D.1 for the room with volume V = L×B×H m3 For the higher frequencies the total sound field is divided into three fields, grazing the surfaces perpendicular to the axis x, y and z, and a diffuse field For each of these fields the effective absorption and corresponding reverberation time is determined The importance of each of these sound fields is determined by the number of modes in those fields deduced from the room dimensions For the lower frequencies the total sound field is considered with a reduced absorption effect due to the lack of diffusion in the room at those frequencies 18