[linux-audio-dev] IR FFT smoothing

Andrew Gaydenko a at gaydenko.com
Sun Jul 2 14:57:57 UTC 2006

Being under DSP studying, I have accidentally met Judith C. Brown paper about
constant Q transform. An apparent thought is: constant Q transform is more direct
way for SPL-observing rather FFT+smoothing. Is it so (I don't mean RT-apps)?

======= On Saturday 24 June 2006 19:30, Fons Adriaensen wrote: =======
On Sat, Jun 24, 2006 at 07:15:38PM +0400, Andrew Gaydenko wrote:

> And the question is: what is common way to smooth the result? Some offtopic apps has
> something like "1/24, ..., 1/3 octave smoothing". What does it mean?

Lowpass (linear phase) filtering of the response. Or windowing the
IR which is equivalent.

If you window the IR, you get a constant resolution over the
entire range of the FR. To get a variable rate such as 1/3 oct,
you need frequency dependent windowing - the window gets shorter
as frequency rises. It's not easy to do right (one of the reasons
why aliki still isn't finished).

IIRC DRC can produce such plots if you ask it nicely.


Follie! Follie! Delirio vano e' questo!

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