Nord2000: Nordic noise prediction method
The Nordic noise prediction method, Nord2000, was introduced by the Danish Environmental Protection Agency for strategic mapping of road and railway noise in 2006, and since July 2007 the method has been the prescribed calculation method for road and railway noise.
A joint Nordic prediction method
Nord2000 is a joint Nordic prediction method that was initially developed in 1996-2001 following an initiative from the Nordic Council of Ministers. It was intended to utilise the results of research and development that had taken place since the first joint Nordic methods were published in the 1970’s and early 80's.
The method includes source models for road and rail traffic in third octave bands from 25 Hz to 10 kHz. The propagation model can be applied for a variety of weather conditions, allowing a precise yearly average to be determined.
Complicated terrain is handled by a concise procedure, so the interpretation of terrain shapes by skilled personnel that earlier was necessary is now abandoned, and the method can be applied to automated noise mapping without loss of accuracy.
Use of Nord2000 in Denmark
In Denmark, weather statistics have been published for four weather classes (which are adequate for strategic noise mapping and general surveys). For detailed and precise calculations more specific calculations are necessary, and weather statistics for nine weather classes are published for this purpose.
In city centres, where the sound propagation is not free but influenced by repeated reflections and screening, only one weather class (neutral) is normally used.
Technical description, comparison with Harmonoise
The propagation model is based on geometrical ray theory, and the calculation of screening is based on geometrical theory of diffraction.* Refraction is modelled by using curved sound rays; the curvature depending on the sound speed profile and is determined by a semi-analytical approach.
The team responsible for Nord2000 took part in the European Harmonoise project, where the Nord2000 model formed a basis for the development of the Harmonoise Engineering model. Several of the findings from this project have been subsequently introduced in an update of Nord2000.
The benchmark cases used for validation of the Harmonoise model was also used for validation of Nord2000-road with a good result. It is expected that results obtained by use of Nord2000 are indistinguishable form results obtained by Harmonoise Engineering model. The Nord2000 propagation model has also been validated for high noise sources such as wind turbines.
The mandatory use of Nord2000 for strategic noise mapping is a consequence of the rules in Statutory Order no. 717 from 13 June 2006 . It also specifies most of the parameters to be used for the calculation (including the weather statistics, nine weather classes). Statutory Order no. 647 from 18 June 2007 specifies the corresponding statistics with four weather classes.
The Danish Environmental Protection Agency guidelines 4/2006 "Noise Mapping and Noise Action Plans" (in Danish) describes the use of Nord2000, mainly with a view to noise mapping.
In guidelines 4/2007 "Noise from Roads" (in Danish) Nord2000 is prescribed for general use with road traffic noise.
Simultaneously with this guideline, a supplement to guidelines 1/1997 "Noise and Vibration from Railways" was published, when Nord2000 was introduced for general use with railway noise.
All the technical publications are in English.
Download the manual for Nord2000-road (2006) (PDF, 685KB)
The background reports describe and specify the building blocks of the method;
A set of test cases has been elaborated for Nord2000 road. Corresponding test cases for railway noise focus on short distances, since the propagation corrections are identical.
Download Environmental Project no. 1335 from 2010 , for more information about the revised test cases for updated version of Nord2000-road.
Software implementing Nord2000
A few brands of noise mapping software has implemented Nord2000.
A program for approximate calculation of road traffic noise in a number of test cases can be downloaded for free at SINTEF .
* In order to handle non-flat and non-homogenous ground as well as multiple screens, screens with multiple edges, and propagation in an inhomogeneous atmosphere with vertical sound speed gradients, heuristic semi-analytical modifications have been introduced.