Re: [Signal PKG] limited slope

[Robert T. Short]

On 12/15/2017 12:27 AM, Renato S. Yamane wrote:
> 2017-12-14 20:25 GMT+01:00 Robert T. Short <address@hidden>:
> > On 12/13/2017 11:39 PM, Renato S. Yamane wrote:
> > > Regarding the code below, someone have an idea why I have this limit
> > > in low frequencies?
> > >
> > > Please, see the frequency response on image available in:
> > > https://ibb.co/cgwOqG
> > >
> > > Detail: when I use a crest factor of 12dB instead 6dB, I don´t have
> > > this problem.
> > >
> > > ==============
> > > pkg load signal;
> > > pkg load ltfat;
> > >
> > > sampling_rate = 44100;
> > > lenght = 30;
> > > hpf = 400;
> > > lpf = 4000;
> > > crest_factor = 6;
> > >
> > > typenoise = noise((lenght)*sampling_rate, 1, 'pink');
> > > [b,a] = butter(2, [hpf/(sampling_rate/2), lpf/(sampling_rate/2)]);
> > > filtered = filter(b, a, typenoise);
> > > filtered = filtered / (rms(filtered) / 10^(-crest_factor/20));
> > > audiowrite ('signal.wav', filtered, 44100);
> > > ==============
> >
> > I don't get the same spectral plots you show here.  My results are much more
> > like your "expected" slope.
> Wowww!
> Can you tell me how you plot it? Just to be possible I make the same
> check here in my side...
>
> Thanks,
> Renato
>
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Well, I used a Welch's method estimator to get the spectral density.  I 
used a Hamming window, but just about any window should do.  I didn't 
use any overlap.  There is such an estimator as part of octave.  Then I 
just plotted it.  I did a semilogx just like you did and only for 
frequencies > 1Hz.