Author Topic: Why do I get -99 dB for all my results?  (Read 1363 times)


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Why do I get -99 dB for all my results?
« on: October 16, 2017, 02:48:31 PM »
Missing results are shown as -99.  This indicates that no noise level has been calculated for that case.  This can happen in many ways, for example:
  • A tile was not calculated
  • The receiver point was outside the angle of view or beyond the cut-off distance
  • The receiver point was inside a building
  • There were no noise sources of the type applicable to the chosen calculation

Your case was the last of these - you wanted to calculate the Leq of rail noise sources, but chose the CRTN calculation method.
Each calculation method is applicable to its own type of source:
  • CRTN for Roads
  • CRN & TNPM for Rail
  • BS5228 for Open sites

Please beware that choosing Leq calculations will NOT calculate noise for all types of source.
Please also beware that the choosing a category combination like Road + Rail does not (and cannot) add together noise from road and rail sources. 

Adding noise from different types of noise source
To do this, you must
  • firstly calculate the road sources using CRTN and the rail sources using CRN or TNPM; and then
  • use the Results Processor to add together the noise from the two types of noise source