The level of acoustic attenuation is indicated by the Class Symbol below as required by Table 1. Where acoustic attenuation symbol A, B or C is combined with thermal insulation symbols the selected insulation thickness shall be the greater of the two requirements.For example, in case of PPA which means insulation type personnel protection and acoustic insulation class A are required, and when required PP thickness is 40mm and acoustic insulation class A thickness is 50mm, only acoustic insulation shall be applied which is thicker one.In case of PGA which means double wire type personnel protection and acoustic insulation class A are required, only acoustic insulation thickness 50mm shall be applied because acoustic insulation (Min.50mm) covers the requirement of personnel protection.When the following acoustic insulation cladding thickness requirements differ from the thermal insulation protection sheeting requirements of the greater of the two thicknesses shall be selected.
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