Home Theater Forum and Systems banner

1 - 4 of 4 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter #1
I have sort of an 'off label' application for REW that doesn't involve any sort of room testing, equalization, phase evaluation, etc.
I have a box that we want to place an item into, where we measure the SPL and get a snapshot of the spectrum of noise from it. We would collect data from many of these items for comparison. We'd like the SPL number to be an A-weighted average, and the spectrum to be similar to what we see using a handheld meter (in our case, an NTI Audio XL2) displaying a 1/3 octave, or 1/48, or spectrum, etc. A-weighted RTA.
We have a UMIK-1 with it's calibration file. That is working in REW except it seems that I cannot apply A-weighting to the RTA display. Is that correct? The REW RTA curve is significantly different below 1KHz than the handheld meter. The handheld meter's mic and the UMIK-s are placed in exactly the same position for these comparisons.
Can anyone suggest a better way to make these measurements?

Thanks!
Cris
 

·
Premium Member
Joined
·
6,711 Posts
You could apply the A weighting by loading a soundcard cal file that has an inverse A weight response - you would then need to set the SPL meter to Z weighting so that the cal file did the work, otherwise you would get double A weighting. Attached is one I prepared earlier :)

View attachment a-weight-inverse.zip
 

·
Registered
Joined
·
3 Posts
Discussion Starter #3
Good idea, thanks for that.
The UMIK-1 being USB mic, doesn't use a sound card - so would I use this inverse file instead of the UMIK-1 calibration file? And then to apply the UMIK-1 corrections I guess I could edit the inverse file to add/subtract the specific mic calibration numbers, right?
Actually, maybe the UMIK-1 corrections are trivial enough that I wouldn't worry about it.
Thanks-
 

·
Registered
Joined
·
3 Posts
Discussion Starter #4
Oh - I just found where to apply the file to the soundcard. Works perfectly without fiddling with the UMIK-1 calibration at all.
Excellent.
Cheers-
 
1 - 4 of 4 Posts
Top