RdT [Reflection Decay Time] - NOT RT60

[Chuck Gerlach]

I did a search on RdT in this website but found nothing. This is the better measurement than RT60 for small rooms [according to many and as stated in the RP22 CEDIA document]. I've been told REW will display it but I can't seem to locate how/where.

Thanks in advance.

 

[John Mulcahy]

You could just look at the ETC curve on the Filtered Impulse graph to see how long after the peak it is until the graph is below -60 dB. A difficulty with that is the graph may never get that low, depending on the noise levels and signal-to-noise ratio of the measurement. Longer sweeps can help with that. Probably better using the RT60 Decay graph.

 

[Chuck Gerlach]

John: Thanks for your response but I guess I'm a bit confused. Someone who knows REW really well told me that I could display RdT directly. Is that not the case?

 

[John Mulcahy]

That depends. RT60 is reflection decay time, but it is defined for spaces where the reflections are sufficiently dense to form a diffuse field. That's the case for large spaces, and for smaller spaces above a few hundred Hz, depending on how small. RP22 has seen fit to apply a different label for smaller spaces, presumably to emphasise the diffuse field factor and to have numbers to target where there isn't a diffuse field.