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Natural Science Forum / Physics / Acoustics / August 2008Third octave band and CADNA-A
Hi :+) . Has anyone got an advice. I am doing a project to assess impact of proposed entertainment noise upon residents. Will be monitoring third octaves bands on site and want to then build a CADNA-A model of post development with entertainment noise, car park movements, beeping horns in etc. However the modelled output at the receiver (monitoring point) is not third octave? Therefore , I won't be able to compare to the monitored third band octave results. Anyone have any suggestions???? > Hi :+) . Has anyone got an advice. I am doing a project to assess > impact of [quoted text clipped - 7 lines] > > Anyone have any suggestions???? The third octave bands can be converted to octave bands by logaritmically adding the three bands centered on the octave band frequencies. Or you could split the octave band output to third by doing the reverse. Why don't you just set the meter on octave bands instead of third octave bands. > > Hi :+) . Has anyone got an advice. I am doing a project to assess > > impact of [quoted text clipped - 15 lines] > Why don't you just set the meter on octave bands instead of third > octave bands. Just to note that you can only go from Third to single octave and get meaniful results. If you split the single octave to third then this will not represent valid third octave numbers. Lp 1/1 (for 1000Hz) = 10xLog(10^(Lp 800Hz) + 10^(Lp 1000Hz)+ 10^(Lp 1250Hz) ) Other frequencies follow this. Although you could log average backward to thirds the results would not be valid. Also the above equation makes assumptions that the three third octaves add together constructively and this may not be totally true so even the above equation does not give rigidly valid results. The best way to get octave values is as Mark wrote, just set the meter to measure in single octaves, if the meter can measure in thirds it is most likely that it can be set to measure in single octaves. Regards Tom > > > Hi :+) . Has anyone got an advice. I am doing a project to assess > > > impact of [quoted text clipped - 37 lines] > > - Show quoted text - Thanks for your help :+) > > Hi :+) . Has anyone got an advice. I am doing a project to assess > > impact of [quoted text clipped - 15 lines] > Why don't you just set the meter on octave bands instead of third > octave bands. Thanks for the advie much appreciated :=) |
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