Acustic Insulation - NORAC
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Acoustic Insulation

In the marine and offshore industry, the acoustics insulation properties of the interior systems are of high importance. The acoustic insulation standards on board, especially in passenger ships, are continuously rising.  At Norac we are therefore working hard to be able to deliver products that can satisfy the high standards for acoustic insulation.


When we talk about acoustic insulation properties, we normally separate between sound absorption and sound reduction.

Sound absorption, Norac AS

Sound absorption:

Sound absorption is a material property which describes how well sound waves are absorbed in a material, thereby preventing sound from bouncing around the room.


For acoustic insulation requirements, sound absorption is relevant when considering noise levels within the same space as the noise source. The ability of the walls, floor and ceiling of a room to absorb noise will be important in reducing noise reflected back from the surfaces into the room, creating echoes.


A material’s sound absorbing properties are expressed by the sound absorption coefficient, α (alpha), as a function of the frequency. The alpha (α) ranges from 0 to 1.00, where 0 is total reflection and 1.00 is total absorption.

Sound reduction:

When it comes to sound reduction, we talk about the reduction of sound through an element of construction (wall, floor, door, or ceiling). For acoustic insulation requirements, the sound reduction value is relevant when considering noise levels in a space separated form the noise source, for example between cabins.


The sound reduction for any construction will vary with the frequency of the sound source. Although the sound reduction for a construction is measured at various frequencies, an overall single value is used to express the sound reduction property. This value is called the “weighted sound reduction” or “sound transmission loss” value (Rw) and the unit of measure is decibel (dB). The higher sound transmission loss of a construction, the better it functions as a barrier to the passage of unwanted noise.


The method of measurement and analysis of sound absorption and sound transmission loss of Norac products are conducted at certified laboratories in accordance to the following standards:

  • ISO 354:2005
  • ISO 11654:1997
  • ISO 10140-2:2011
  • ISO 717-1:2013
  • ISO 354:2005
Sound reduction, Norac AS