Noise - Environmental - Weather - Total Effect
Predicting the Effect of Meteorological Categories
Note: In the above table a negative vector wind speed denotes wind blowing from the receiver towards the source, i.e. reducing noise levels.As the Met Categories increase, the received noise levels increase (attenuation decreases), and category No.4 is defined as having a zero meteorological influence. In other words categories 1 to 3 reduce noise levels, and categories 5 and 6 lead to higher noise levels. It can be seen that the highest likely noise levels occur either with Beaufort "Light air" winds under "stable" atmospheric conditions [temperature inversion] or with stronger winds (Beaufort "Light Breeze" or more) under normal atmospheric conditions.
Predicting Noise Levels
The main CONCAWE model predicts noise levels at a distance based on the weather conditions and a knowledge of the source spectrum in octave bands; however there is a simplified model simply based on the likely dBA effect as below.
When predictions using this model were compared against actual measurements of
broad band noise, the measured level was within a 14 dBA range centred on the
predicted level [95% confidence limits]. This was only slightly worse than using
the full octave band method. It just shows that predicting the effect of weather is
not very reliable!! You should consult the full report available from
www.concawe.be for full details.
The directory contains details of suppliers of prediction software incorporating the full CONCAWE model and consultants experienced in allowing for the effects of weather conditions.