As per DIN 4109 the minimum requirements regarding the sound insulation of ready-for-use doors or elements of doors are only indicated as an approximate value in a sound reduction index RW (evaluated sound reduction index in dB without sound transmission over flanking parts). The manufacturer tests the aptitude of a door element with regard to the sound insulation requirements by making qualifying examinations under laboratory conditions in defined test areas. The aptidude is stated in a test certificate established by an authorised testing laboratory, indicating the laboratory sound reduction index RW,P.
However, as environmental influences are much more eliminated under laboratory conditions and these test results are generally better than test results under normal conditions, the so-called allowance for tolerances has been introduced in order to evaluate these sonic differences. The allowance for tolerances should consider the possible difference between laboratory and normal conditions and is of 5 dB regarding doors. The allowance for tolerances should, however, not compensate deficiencies in planning or construction, which are often the reason for not fulfilling the sound insulation requirements.
This means that the sound reduction index RW,P evaluated in the qualifying test must be at least 5 dB higher than the required index RW for real constructions. Regarding a door with sound insulation in areas with highly differing temperatures, e.g. the door of a flat, the assured features regarding sound insulation can only be garanteed in case that the door elements are adapted to these additional requirements (use of aluminium composite panels for climate category III).