Re: [Audacity-nyquist] Statistical analysis (and hello)

[George J. <geo...@gm...>]

Thanks to you both for replying.

Alex I've seen your silence plugin and it does look like a good place to
start.  We tend to work with 1/8second samples for a sound level, all
averaged over 15 minutes, so what I think I'll do is this:

read 1/8 second sample;
average the 1/8 second (thanks Mikael, will look at your solution) - that
way I don't have to worry about memory by analysing for 15 minutes;
store the level in an array (I presume this is just a list in lisp);
repeat for next 1/8 seconds until I get to 15 minutes;
sort the array from lowest to highest;
find the percentiles I'm interested in;
average them all for an overall 15minute average;
output the results, preferable to a text file.

I'll probably have multiple files to do - 15 minute samples over at least a
day, so I'd have to load the samples, analyse, write the stats, dump the
sample etc.

So tomorrow I learn lisp (or the next day).  Thanks again
George

On 1/13/07, Mikael <mr....@gm...> wrote:
>
> Hi George!
>
> I have fiddled a bit with acoustics in audacity with some success and can
> help out with the equivalent level. You can use the nyquist function snd-avg
> to get it like this:
>
> (setq sl (snd-length s 999999999999))
> (setq calibration 97)
> (+ calibration (* 0.5 (linear-to-db (snd-maxsamp (snd-avg (mult s s) sl sl
> OP-AVERAGE) ))))
>
> Paste this into the Effect -> Nyquist prompt, and you'll get the
> equivalent level in dB of what ever mono audio you selected. Of course it is
> uncalibrated, that's why I have the calibration variable if you would like
> to set it. Using 97 like I do seems to give 94 dB for a 1000 Hz tone with
> amplitude 1.0.
>
> Note that it is the equivalent level without A-weighting, to get that you
> need to filter with an A-filter first (se the post by Edgar you mention).
> Watch out for clipping when filtering, I believe audacity clips any sample
> above 1.0...
>
> I would guess that L10 and L90 are more diffcult, I think you need to
> calculate the histogram to get it. Please mail any success to this list.
>
> Mikael Ogren
>
> PS I use snd-maxsamp to extract the single sample from the previous step,
> I guess there is a more elegant way but I couldn't find it. DS
>
> >
> >
> > On 1/12/07, Alex S. Brown, PMP <ale...@al...> wrote:
> > >
> > > I did a silence-detection plug-in which is now included in the regular
> > > Audacity distribution. That required me to look at some very basic
> > > noise
> > > detection issues. I did not have to do the statistical analysis,
> > > because
> > > I just looked at areas of the signal that exceeded or fell below a set
> > > threshold.
> > >
> > > You could look at my plug-in for help. I found one of the hardest
> > > parts
> > > of writing it was being careful not to accumulate all the samples in
> > > memory. If you do, then your memory use quickly skyrockets for
> > > anything
> > > more than a very short sound wave.
> > >
> > > Your first step should be to look at the built-in functions to
> > > manipulate the signal. If you can find a way to reduce the number of
> > > samples you have to read, you will get a result much more quickly.
> > >
> > > If you need specific advice, let us know more about the math of your
> > > calculation and how it is typically done, and we might be able to
> > > guide
> > > you towards some useful built-in functions or programming models.
> > >
> > > --Alex
> > >
> > > George Jenner wrote:
> > > > Hello,
> > > >
> > > > I was just searching the archives to see if I could do some
> > > > statistical analysis of recordings.  I see Edgar recently published
> > > an
> > > > A-weighting filter and I've succesfully runi it as my first plug in.
> > > > (Sorry I've only just joined the list so I only know you by the
> > > > archives).
> > > >
> > > > At work I'm using audacity to measure noise levels, so I wonder if
> > > > this has been done before.  I'd like to determine L10, L90 and Leq
> > > of
> > > > a sample.  For those of you whose jobs are more interesting than
> > > mine,
> > > > L10 is the level which is exceeded by 10% of all samples.
> > > >
> > > > Has this been done by anyone?  Lisp is a foreign language to me so
> > > > I'll need some time to get used to it.
> > > >
> > > > Thanks for any help,
> > > > George
> > >
> > > --
> > > Alex S. Brown, PMP
> > > ale...@al...
> > > http://www.alexsbrown.com - Free PM Articles
> > > http://www.rlprj.com - PM Speaking and Teaching
> > > ahttps://www.xing.com/profile/AlexS_Brown OpenBC/XING Professional
> > > Networking
> > > http://www.linkedin.com/in/alexsbrown LinkedIn Networking
> > >
> > >
> > > -------------------------------------------------------------------------
> > >
> > > Take Surveys. Earn Cash. Influence the Future of IT
> > > Join SourceForge.net's Techsay panel and you'll get the chance to
> > > share your
> > > opinions on IT & business topics through brief surveys - and earn cash
> > >
> > > http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV
> > >
> > > _______________________________________________
> > > Audacity-nyquist mailing list
> > > Aud...@li...
> > > https://lists.sourceforge.net/lists/listinfo/audacity-nyquist
> > >
> >
> >
>
> -------------------------------------------------------------------------
> Take Surveys. Earn Cash. Influence the Future of IT
> Join SourceForge.net's Techsay panel and you'll get the chance to share
> your
> opinions on IT & business topics through brief surveys - and earn cash
> http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV
>
> _______________________________________________
> Audacity-nyquist mailing list
> Aud...@li...
> https://lists.sourceforge.net/lists/listinfo/audacity-nyquist
>
>
>