Norwegian Standard for acoustic classification of buildings now available in English

A revised version of NS 8175 was adopted on July 1, 2019. Now the standard that establishes four sound classes for buildings has been translated into English.

There is an increasing need for better sound insulation in the community. The Norwegian standard NS 8175:2019 provides standardized classes with better acoustic conditions than the minimum requirements. 

The standard establishes limit values for sound classes in the form of:

• airborne sound insulation
• impact sound insulation
• sound level (noise level)
• room acoustic quantities.

Sound insulation in dwellings

One of the most important changes were made on limit values for airborne sound and impact sound insulation for dwellings. An expanded frequency range at low frequencies (at the bass range) is stated to reduce noise annoyance in dwellings. To encourage use of other acoustic classes, the increments between the sound classes for dwellings were also changed from 5 dB to 4 dB. This has also been done for other building types to some extent.

In the revised standard, updates of related documents and guidelines, and unclear wordings were considered. The outdoor noise guidelines in T-1442 for area planning were revised in 2016. Revision of the standard included updates for sound level outside windows of dwellings, outside at least one bedroom, and some other limit values. Also, the provisions concerning limit values for indoor sound levels at night-time and the number of noise events from outdoor sound sources, have been clarified. 

Universal design of restaurants and dining rooms

Requirements for acoustic conditions for universal design were reconsidered after introduction in the edition of 2012. The great annoyance of hearing disabled in restaurants and dining establishments were reconsidered. Recommendations regarding reverberation time in restaurant premises related to room volume and the number of people have therefore been introduced in an annex (assessment of acoustic capacity). Also, noise limit values have been included for indoor sound levels in museums, libraries, media centres, art galleries, etc. from outdoor sound sources. 

A Norwegian study on annoyance in dwellings

The revised limits for dwellings are based on a survey made for the building authorities around the year 2015/2016. The acoustic conditions for dwellings built in accordance with the requirements from 2008 and 2012 were registered. The resident’s evaluation of the acoustic conditions was studied by using an interview survey. The results showed that the acoustic insulation was insufficient at low frequencies, at bass range. This was especially pronounced for impact sound insulation. The annoyance of residents was not comparable with the sound insulation without including the sound insulation at low frequencies. The report is available from DiBK (in Norwegian). 

The Building Codes

Norwegian Building Codes give general requirements for sound insulation and noise conditions in buildings. For the technical requirements, the class C in the Norwegian standard NS 8175:2012 is referred. This standard has been revised, and an improved edition was published in 2019. 

The Norwegian standard establishes four acoustic classes for buildings, A, B, C and D. Class A represents the limit values that provide especially good acoustic conditions, while class D the poorest. The criteria for acoustic conditions are divided into four sound classes (A to D) so that the limit values for buildings or parts of buildings can be selected according to their intended use. The updated Norwegian standard, NS 8175:2019, has several more or less substantial changes. 

The Technical Building Codes (TEK) regulate requirements for acoustic conditions in the form of functional requirements. Changes in Building Codes are decided by the government and authorities. In 2019/2020, the revised provisions of the Norwegian standard and revised limit values are being analysed for consequences on economical and other matters. 

Standards Norway are waiting for results of the analysis and hope that the revised edition of NS 8175 is accepted also for use in accordance with the Building Codes.

Relevant links:

Norwegian Building Acts and Regulations