AFMG Network Forum

mikelotinga · Member

I have run an AURA calculation and am getting some anomalous results for T20 & T30 calculations at some frequencies: there seem to be 'spots' on the calculation maps where EASE predicts a negative RT.

This is a closed room with no holes, and all faces are correctly orientated.

Please help!

Bruce · Member

I assume this is an AURA Mapping. Look at the Echogram and the Histogram. You likely only have a few particles in many bins, so the Schroeder curve does not have enough data.

mikelotinga · Member

Hi Bruce,

Thanks for your reply.

Yes, it's AURA mapping.

The distribution looks ok (apart from the small number of minus values!). The echogram shows the reverb getting cut off after 840ms, which is due to the settings made during calculation - could this be enough to result in the negative values? If so if I increase the length would you think this would solve the issue, or should I increase particles as well?

Is there anything else you are aware of that could potentially cause this? I'm running a recalculation as we speak...

Thanks again,

Mike

Bruce · Member

Hi Mike,

Make sure you check the Histogram as well to see that there are sufficient particles in the bins. That will tell you if you need more particles in the calculation. As far as the length, use the Schroeder display in the histogram and the sabine absorption to help decide if the time is long enough. Do you have >35 dB of decay in the echogram? If not, then you will get questionable values for T30.

Hope this helps,
Bruce