quick question on frequency response smoothing

[PaulRain]

Let's say that a good FR is +/-5dB, my question is...shall the graph be smoothed or not? I mean is the 10dB difference from lower to higher peaks checked using the often mentioned 1/3 octave smoothing?
I know the FR is not the only thing to look at, this is just a question on that

[Hannes_F]

I personally mostly look at ridge line in the waterfall, and that is unsmoothed. Alternatively I use 1/24 octave smoothing.

If you need to impress somebody else then apply smoothing to taste. 1/3 octave smoothing can look very impressive. "Official" documents mostly use that.

[DanDan]

It depends on what you want to see. Third octave is very good for viewing the overall slope of the spectrum. IMHO this view best describes the tonality of the room. A nice downward slope towards HF translates very well. See Understanding RTA at studiotips.com or the B and K research which shows an almost identical curve.
The LF lowest extent will indicate the 'size' of the sound.

When wish to look for and examine particular issues, e.g. LF SBIR, HF combing, the lesser amounts of smoothing come into play. If find them all useful.

DD

[Ethan Winer]

Originally Posted by PaulRain

shall the graph be smoothed or not?

You already got the right answers, but I'll add this: I generally use no smoothing for a graph showing 20-300 Hz, and 1/3 (or 1/6) octave smoothing for full range or just mid/high frequency graphs.

--Ethan

________________
The Acoustic Treatment Experts

[PaulRain]

I'm sorry but maybe my question was not clear....
I don't use any smoothing when I do the tests in my room.....
what I was wondering is: when people say a room response should stay between +/-5dB...do they refer to a smoothed response or not?

[DanDan]

P, the smoothing has no effect on the tests. It's only a viewing thing, just like zoom in a way. Plus or minus 4-5dB would be extraordinarily good. That suggests 1/3 octave smoothing, or perhaps wishful thinking!
DD

[PaulRain]

Thanks a lot

[Ethan Winer]

Originally Posted by PaulRain

when people say a room response should stay between +/-5dB...do they refer to a smoothed response or not?

Ah, gotcha. People mean it both ways. It depends on the person and how knowledgeable they are.

To someone who is informed about acoustics, a dB span means without smoothing. Note that the resolution of a graph depends on both smoothing (or not) and also the gate time that's applied. Using a short gate time is similar to applying smoothing. I generally use a gate time of at least 200 milliseconds for hi-res LF response and waterfall graphs. In REW you can see the graph resolution change as you adjust the gate time.

--Ethan

[Jens Eklund]

http://www.gearslutz.com/board/6121622-post20.html

[PaulRain]

thanks jens, very interesting thread....