RTA Question - Home Theater Forum and Systems - HomeTheaterShack.com

Old 03-09-13, 09:32 AM Thread Starter
Shackster
Chuck

Join Date: Jan 2013
Posts: 67
RTA Question

This may have been asked before, but I can't find the answer....
When looking at the RTA graph, the highest point on the db scale looks like 56.88, yet, the box in the upper right shows 66.1 db.

What's/why the difference?

This was taken with a UMIK-1, and, not in a quiet room (just messing around, trying to figure it all out)

Last edited by ceh383; 03-09-13 at 09:57 AM.
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Old 03-09-13, 10:31 AM
REW Author

John

Join Date: Apr 2006
Location: UK
Posts: 6,303
Re: RTA Question

The figure at the top right shows the combined level across the whole frequency range, the 56.88 is the level at a particular frequency.
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Old 03-09-13, 10:53 AM Thread Starter
Shackster
Chuck

Join Date: Jan 2013
Posts: 67
Re: RTA Question

Ok, that makes sense.

So, another question.

When using RTA to figure out noise floor, do you look at a peak frequency or the total of all frequencies?
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Old 03-09-13, 01:27 PM
Shackster

Join Date: Mar 2013
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Re: RTA Question

....Thnx...
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Old 03-10-13, 05:10 PM
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John

Join Date: Apr 2006
Location: UK
Posts: 6,303
Re: RTA Question

Quote:
ceh383 wrote: View Post
When using RTA to figure out noise floor, do you look at a peak frequency or the total of all frequencies?
Depends what it is you are trying to establish and what use you want to make of the figure. In a quiet room the overall SPL figure tells you the background sound level, the peaks show you the main contributors and the levels elsewhere indicate the noise floor at those frequencies with the RTA FFT length that was used (increasing the length means narrower frequency bins so less level in each bin).
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Old 03-11-13, 09:38 AM
Senior Shackster

Join Date: May 2011
Location: St. Petersburg, Florid
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Re: RTA Question

Quote:
JohnM wrote: View Post
The figure at the top right shows the combined level across the whole frequency range, the 56.88 is the level at a particular frequency.
I'm a little confused? The overall level at 66.1 db is higher than the maximum peak level of 56.88 (as you stated above). Is there a weighting curve applied for the full spectrum or am I missing something?

I just don't get it!
AVoldMan is offline
Old 03-11-13, 03:47 PM
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John

Join Date: Apr 2006
Location: UK
Posts: 6,303
Re: RTA Question

It might make more sense if I express it differently: of the 66.1 dB total sound pressure level in the room, there was a 56.88 dB contribution at 18.09 Hz.

The 66.1 dB is the sum of that 18.09Hz component and the components at all other frequencies, the sum will always be higher than the level at any particular frequency.
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Old 03-12-13, 01:28 PM
Senior Shackster

Join Date: May 2011
Location: St. Petersburg, Florid
Posts: 122
Re: RTA Question

Quote:
JohnM wrote: View Post
... The 66.1 dB is the sum of that 18.09Hz component and the components at all other frequencies, the sum will always be higher than the level at any particular frequency.
Ahhhh! That makes more sense! I think I was looking at the frequency plot and thinking AVERAGE SPL - WRONG. I just forgot the total SPL integrates over all frequencies => any single peak will always be less than the total.

Thanks!
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