# Average decibel measurement over time?



## Zeitgeist (Apr 4, 2009)

Is there a way in REW to take an average DB reading over an average of time? ie, a minute or so? 

For example, play pink noise for a minute and get a DB average over that entire minute.

I was reading an article about level matching multiple subs and I was curious.
http://www.audioholics.com/tweaks/g...-setup-calibration-1/multiple-subwoofer-setup

I figured there was some obvious way to do it that I didn't see.

Thanks!


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## JohnM (Apr 11, 2006)

Not at the moment, though enhancements to the SPL meter are on the future features list. A better option for that particular case would be to use band limited periodic noise as the test signal, as that would not have the VLF lumpiness of pink noise and give much more stable readings, but providing those test signals is also on the future features list.


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## JohnM (Apr 11, 2006)

On further thought, you could use the RTA with the averaging set to "Forever", reset the averaging at the start of the period and then stop the RTA and (if desired) save the result at the end. The RTA will show an *unweighted* dB level for the period over which it was running.


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## Zeitgeist (Apr 4, 2009)

I kept meaning to reply and never got a chance.

Thanks for both responses!

I know that I seriously under utilize REW - so I'm surprised when there is something that I want to do - that it can't already do very well.

I need to use RTA some... that's something I've done very little with.


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## MachA57 (Sep 18, 2009)

JohnM said:


> The RTA will show an *unweighted* dB level for the period over which it was running.


Hello and thanks for your answer.
I dont speak very good English.
Could you explain what is an unweighted dB ?


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## JohnM (Apr 11, 2006)

MachA57 said:


> Could you explain what is an unweighted dB ?


No frequency weighting, i.e. not C-weighted, not A-weighted, but flat.


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## MachA57 (Sep 18, 2009)

You mean probably dBZ, aren't you ?


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## JohnM (Apr 11, 2006)

Yes, although strictly speaking Z weighting only defines the minimum span over which the weighting should be flat (within an allowed tolerance).


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## MachA57 (Sep 18, 2009)

I ask you because i want to measure the dbC by octave in the Hometheater room and after measure the same dbC by octave in an other room.
I want to measure the isolation (insulation maybe)


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## Zeitgeist (Apr 4, 2009)

JohnM said:


> On further thought, you could use the RTA with the averaging set to "Forever", reset the averaging at the start of the period and then stop the RTA and (if desired) save the result at the end. The RTA will show an *unweighted* dB level for the period over which it was running.


I'm a little confused and I'm sure that it's because of me not understanding something.

If I have the db meter on REW up and RTA --- should the Input RMS level in RTA be close to the db meter? Just playing pink noise or REW sub pink noise.

Does the db meter show C weighting (like the RS meter itself) -- and that's why it's so different than the unweighted value in RTA? It's sometimes off 10-20db.

I see that C weighting drops off 10+db near 10-20hz.

Thanks in advance.


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## JohnM (Apr 11, 2006)

Both the RTA and SPL meter are unweighted at the moment, but the RTA takes into account the mic/meter and soundcard cal files whereas the SPL meter doesn't. As it happens I now have A/C/Z weighting and cal data working for the SPL meter in my current dev build, so that will go into the next release.


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## Zeitgeist (Apr 4, 2009)

JohnM said:


> Both the RTA and SPL meter are unweighted at the moment, but the RTA takes into account the mic/meter and soundcard cal files whereas the SPL meter doesn't. As it happens I now have A/C/Z weighting and cal data working for the SPL meter in my current dev build, so that will go into the next release.


So, if I'm using the (infinately averaged) RTA "Input RMS level" for level setting - that's the most correct? ... Because it takes into account the CAL files..

Sorry, I feel like I'm really dense!


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## JohnM (Apr 11, 2006)

That's right.


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## Zeitgeist (Apr 4, 2009)

JohnM said:


> That's right.


Thanks a bunch!


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