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Noise levels

By Mikael Ögren

Noise prediction

Prediction methods for noise levels from road and railway traffic have been used for a long time, and typically the methods in use today do a good job of predicting noise levels where they are high, i.e. at positions directly exposed to noise from busy streets. At positions shielded from direct exposure such as quiet courtyards or streets with no or very little traffic flow, the methods tend to underestimate the noise level. This is in principle due to

Many prediction methods can in principle take a high number of reflections into account, but this is computationally very time consuming since all possible ray paths must be identified. In order to make a more efficient method the QSide project made a large number of reference calculations using advanced numerical methods and used these results to create a simplified method that includes many reflections in only one calculation step.

The simplified method for shielded areas was designed to yield a contribution added on top of a calculation with a traditional method. It could be added to a "normal" noise map at all locations since the levels will be relatively low, and will not affect the level at exposed positions. At shielded positions the levels from the "normal" noise map will be too low, but adding the QSide contribution will correct that. The method is illustrated in the image below.

Example of adding calculations
to an existing noise map

Figure 1. Example of adding calculations on quiet sides to an existing noise map.

There is a short slide show (10 images) that presents an overview of the model which you can access by clicking the image below

Slideshow of noise prediction shielded areas

Figure 2. Slideshow of noise prediction in shielded areas, click to access.


  1. Technical report of QSide calculation model