This standard specifies the classification of buildings into four sound classes. Class A represents the limit values providing the most superior acoustic conditions, and class D the most inferior. This standard specifies limit values for sound classes in the form of:
- airborne sound insulation;
- impact sound insulation;
- sound level (noise level);
- room acoustic quantities (reverberation time, reverberation time in relation to room height, mean sound absorption factor, speech transmission index etc.).
In this standard, limit values are given for dwellings, buildings open to the public and work buildings, and apply particularly to schools and other buildings used for teaching, kindergartens, day-care facilities for schoolchildren, hospitals and care institutions, overnight accommodation, offices. For each type of building or each area of use, the limit values are divided into four sound classes according to expected use of, and requirements for, the building in relation to normally furnished rooms. All the different criteria for acoustic conditions given for a sound class shall be satisfied for a building or parts of a building to be classified in a class. The guidelines for assessing compliance are presented in annex B (informative).
In order to provide for equitable use for all (universal design), in addition to criteria for room and building acoustics and limit values for sound and noise conditions, requirements are laid down for the use of sound transmission systems (audio-frequency induction loops, loudspeaker systems and the like) or other assistive technology where these are needed, cf. the Regulations on technical requirements for building works [18, 19, 20]. In addition to assistive technology, people with vision impairments use sound reflective properties of the rooms or spaces in buildings to orientate themselves.
This standard can be applied to classify buildings or parts of buildings, according to the acoustic conditions in the building or to lay down requirements for acoustic conditions for entire, or parts of, buildings. It allows manufacturers to declare the sound classes for buildings and provides instructions for compliance with the sound requirements pursuant to the Regulations on technical requirements for building works. This standard also represents an opportunity to set standardised, differentiated limit values for acoustic conditions in buildings.
The sound classes in this standard are linked to the measuring methods specified in Norwegian standards as given in clauses 2, 3 and 4. The limit values for the sound classes apply to in-situ measurements. The specified classes for sound levels apply to both indoor sound levels (from service equipment in the building and outdoor sound sources) and the sound levels in outdoor areas/outdoor recreation areas (from service equipment in the building or other outdoor sound sources). For classes A and B for dwellings, limit values for sound levels also apply to the use of other technical equipment (which is not fixed service equipment) in the same unit or space.