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Why do RTA DEQs use pink noise?

Started by Impoliticus April 22, 2005
I'm working on a project for a DSP lab class and as you may have guessed
from the topic, the project involves programming a real time analyzer DEQ.
 Perhaps I should have asked this in the planning/research stage, but why
do RTA equalizers, such as the DEQ2496, flatten the frequency response of
the loudspeakers with respect to pink noise? I understand that pink noise
has equal energy per octave, but why send pink noise through the speakers
and then equalize the response of the speakers so that the mic input is
receiving pink noise (or at least close to it)? Couldn't white noise, or
any noise for that matter, be used to do the same thing? Is it because
upon breaking the frequency spectrum into octaves it's easier to compare
the power spectrum since with pink noise there's equal energy per octave?


		
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Impoliticus wrote:
> I'm working on a project for a DSP lab class and as you may have guessed > from the topic, the project involves programming a real time analyzer DEQ. > Perhaps I should have asked this in the planning/research stage, but why > do RTA equalizers, such as the DEQ2496, flatten the frequency response of > the loudspeakers with respect to pink noise? I understand that pink noise > has equal energy per octave, but why send pink noise through the speakers > and then equalize the response of the speakers so that the mic input is > receiving pink noise (or at least close to it)? Couldn't white noise, or > any noise for that matter, be used to do the same thing? Is it because > upon breaking the frequency spectrum into octaves it's easier to compare > the power spectrum since with pink noise there's equal energy per octave?
It seems to me that achieving a flat frequency response with any wideband signal accomplishes the goal. As you know, pink noise has the same power in every octave (or decade, or whatever). That may have some advantage in a practical physical system. The choice is probably a result of experience. (Think about signal-to-noise ratio.) Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
On Fri, 22 Apr 2005 14:20:44 -0400, Jerry Avins <jya@ieee.org> wrote:
> Impoliticus wrote: >> I'm working on a project for a DSP lab class and as you may have guessed >> from the topic, the project involves programming a real time analyzer DEQ. >> Perhaps I should have asked this in the planning/research stage, but why >> do RTA equalizers, such as the DEQ2496, flatten the frequency response of >> the loudspeakers with respect to pink noise? I understand that pink noise >> has equal energy per octave, but why send pink noise through the speakers >> and then equalize the response of the speakers so that the mic input is >> receiving pink noise (or at least close to it)? Couldn't white noise, or >> any noise for that matter, be used to do the same thing? Is it because >> upon breaking the frequency spectrum into octaves it's easier to compare >> the power spectrum since with pink noise there's equal energy per octave? > > It seems to me that achieving a flat frequency response with any > wideband signal accomplishes the goal. As you know, pink noise has the > same power in every octave (or decade, or whatever). That may have some > advantage in a practical physical system. The choice is probably a > result of experience. (Think about signal-to-noise ratio.) > > Jerry
That's essentially correct, Jerry. There's a thorough practical discussion in the "Sound Reinforcement Handbook" published by Yamaha. Recommended for the OP. You might also try asking on rec.audio.pro. The S/N ratio is sometimes distressingly low, but some people there with extensive knowledge of both theoretical and practical aspects.
Charles Krug wrote:

   ...

> That's essentially correct, Jerry. There's a thorough practical > discussion in the "Sound Reinforcement Handbook" published by Yamaha. > > Recommended for the OP.
Thanks for the corroboration, Charles. It's nice to know when a guess works out. ... Jerry -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;