RT measurements - data missing

[Colin]

Hello all,

I'm new to REW and I'm principally interested in measuring reverberation time, although I'll be considering other parameters as time goes on. Currently, I'm accustomed to performing RT measurements with a cabinet loudspeaker (pointed into a corner for diffusion) and interrupted pink noise, measured with a Class 1 sound level meter; this is how I've done it for the last three years.

I'm doing measurements with REW (with sine sweeps) alongside the above method, to determine to what extent the two measurement techniques correlate. So far, I've only had the chance to measure in two rooms. The results from the first room showed what I would consider to be relatively good agreement between the two sets of results. However, when testing another room earlier this week, I was disappointed to find that REW would not record anything in the 1k and 2k octave bands on T20, nor 1k, 2k or 4k on T30. I used three different mic positions, but only one source position.

What, if anything could/should I be doing differently? Is this a common phenomenon?

I'm using the miniDSP UMIK-1, REW 5.19, Windows 7.

Thanks!

 

[John Mulcahy]

Can you post an mdat file with the measurements?

 

[Colin]

Here you go...

 

[John Mulcahy]

The lack of results at 1k and 2k is due to the noise floor, there isn't at least 20 dB of decay in the Schroeder curve before reaching the floor. Try increasing the UMIK input volume setting, at 0.25 it may be applying some attenuation, and if that isn't sufficient try increasing the stimulus.

 

[Colin]

Fab, thanks for a speedy and helpful response!