ISO 12354-3:2017 pdf free

ISO 12354-3:2017 pdf free.Building acoustics一Estimation of acoustic performance of buildings from the performance of elements
“Facade” is understood to mean the whole outer surface of a room. The facade can consist of different elements, e.g. window, door, wall, roof, ventilation equipment; the sound transmission through the facade is due to the sound transmission by each of these elements. It is assumed that the transmission for each element is independent from the transmission of the other elements. The different types of exterior sound fields used in the various measurement situations defined for the determination of the quantities to express the building performance lead to different values. However, it is a reasonably proven assumption that the transmission for a diffuse incident sound field is sufficiently representative for these varying types of exterior sound fields. Therefore, the apparent sound reduction index of the facade for diffuse incident sound is calculated, from which all other quantities are deduced.
NOTE 2 For direct transmission only, Formulae (7) and (8) could be integrated in Formula (1), resulting in the often used expression for the sound reduction index of composed elements.For direct transmission the sound power ratio Te can be determined for each facade element directly from the acoustic data on that element, including the contribution of each composing part; see 4.2.Alternatively this sound power ratio for one or more elements could be estimated from acoustic data on each of the composing parts of that element; see Annex B. The choice depends on regulations and the available acoustic data. Guidelines for the practical use of the model are given in Annex E
NOTE 3 These equations represent the average relation between the quantities. For the single number rating the variation around the average is typically±1 dB. For frequency bands the spread is typically±2 dB for facades composed from various elements. However, in special cases, e.g. where the transmission is completely dominated by single glass panes, the difference between the two quantities at frequencies around and above the coincidence frequency is less systematic and can be much larger.ISO 12354-3 pdf free download.