Katja, that sounds like a nice approach. With sound file playback, I could just delwrite~ the audio 3 seconds so everything would resync. I'm going to have to go back and look at fft, again. I spent a lot of time figuring out how to use [fft~] a few years ago. I'm not quite clear on how to tell what Hz value each bin is indicating. Wait, is it as simple as sample-rate/block-size=Hz?
By the way, if I was starting at the beginning with [fft~] this is the place I would go to start figuring it out: http://www.pd-tutorial.com/english/ch03s08.html Many thanks to Johannes Kreidler for these excellent and thorough guides. It's an excellent place to discover new things, even for experienced users. Sam > > ------------------------------ > > Message: 7 > Date: Mon, 17 Oct 2011 23:43:45 +0200 > From: katja <[email protected]> > Subject: Re: [PD] Analyzing subharmonic frequencies accurately > To: [email protected] > Message-ID: > <CAFY0eaozjc=xMoq3h2mJo6XmAhtKz-V1+XfM44ps4s+ZMb=1...@mail.gmail.com> > Content-Type: text/plain; charset=ISO-8859-1 > > Hi, > > With fft~ you can go up to a framesize of 2^17, that is around 3 > seconds when assuming 44.1KHz SR. The bin resolution is then ~0.37 Hz > which may be just accurate enough for your purpose (spectral leakage > will always make analysis less precise than the bin resolution > suggests). Notice that the latency of your info will also be 3 seconds > then. > > Katja > > > > On Mon, Oct 17, 2011 at 11:24 PM, Samuel Burt > <[email protected]> wrote: >> A friend of mine asked me if I could make some kind of filter that could >> provide information about subharmonic frequencies. I wasn't quite sure what >> he meant, but I thought I'd try a few things to see what I could get. >> >> He mentioned he wanted the following bands 1-3 Hz, 4-6 Hz, 7-9 Hz, 11-14 Hz, >> and 15-18 Hz. >> >> The first thing I tried was a series of [lop~] and [hip~] filters in the >> ranges he was wanting. I stacked multiple [lop~]s and [hip~]s, to make >> really hard limits and then sent the output from each band to vu~ meters. >> This was unreliable. In fact, a 5 Hz sine wave seemed more likely to show up >> in the 10 Hz band. I also tried [bp~], [vcf~], and [svf~] with no luck. >> >> I then took a different approach, using [threshhold~] and [timer] to time >> the distance between zero crossings and output the result. This is very >> reliable for a sine wave, but I fear it wouldn't be that useful for real >> world signals. >> >> Have any of you ever tried to separate out subharmonic frequencies in Pd? >> Any experience with brain wave analysis in software? What's a better >> technique? >> >> Thanks, >> >> Sam in Baltimore >> _______________________________________________ >> [email protected] mailing list >> UNSUBSCRIBE and account-management -> >> http://lists.puredata.info/listinfo/pd-list >> > >
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