Generating negative harmonics
in [DSP]
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From: Clay on 16 Mar 2010 17:16 On Mar 16, 5:02 pm, Nils <n.pipenbri...(a)cubic.org> wrote: > Vladimir Vassilevsky wrote: > > > That used to be a common approach in the electronic music instruments > > before introduction of DSPs. > > Absolutely. I'd like to add that subharmonics have been the way to bring > color into the sound of the trautonium. If you have seen classic movies > from the 60th and 70th you most probably konw the sound of it. > > Worth checking out: > > http://de.wikipedia.org/wiki/Trautonium > > Also: > > http://en.wikipedia.org/wiki/Oskar_Sala > > (the engish wiki-page is seriously lacking information. That guy was a > genius). > > Cheers, > Nils Nils, thanks for that info. I was not aware of the Trautonium. Clay
From: Eric Jacobsen on 16 Mar 2010 17:26 On 3/16/2010 2:16 PM, Clay wrote: > On Mar 16, 5:02 pm, Nils<n.pipenbri...(a)cubic.org> wrote: >> Vladimir Vassilevsky wrote: >> >>> That used to be a common approach in the electronic music instruments >>> before introduction of DSPs. >> >> Absolutely. I'd like to add that subharmonics have been the way to bring >> color into the sound of the trautonium. If you have seen classic movies >> from the 60th and 70th you most probably konw the sound of it. >> >> Worth checking out: >> >> http://de.wikipedia.org/wiki/Trautonium >> >> Also: >> >> http://en.wikipedia.org/wiki/Oskar_Sala >> >> (the engish wiki-page is seriously lacking information. That guy was a >> genius). >> >> Cheers, >> Nils > > Nils, thanks for that info. I was not aware of the Trautonium. > > Clay Nor was I, and usually have my ear to the ground for strange instruments. This page is pretty decent and has some links to sound samples at the bottom of the page: http://120years.net/machines/trautonium/index.html -- Eric Jacobsen Minister of Algorithms Abineau Communications http://www.abineau.com
From: Jerry Avins on 16 Mar 2010 17:31 Tim Wescott wrote: > jungledmnc wrote: >> Hi there, >> >> using waveshaping we can generate odd harmonics, right? Using some tricks >> like adding square we can have even harmonics. >> Is there a way to get negative harmonics? E.g. Sampling rate 44100, >> someone >> feeds it with 1kHz, I want to get 500Hz, or 250Hz for example. >> I have no idea if it isn't completely useless, but it may be worth >> experimenting with :). >> >> Thanks in advance! > > What you want from the subharmonics makes a lot of difference to how you > may generate them. > > You could phase lock to a carrier, if it's well defined. > > You could use pitch shifting, if you're working with instruments or voice. > > You could use some bizarre parametric amplifier approach if you -- well, > I don't know _why_ you'd want to do that! Electromechanical telephone ringers operate on 20 Hz current. Long ago, (still in use on country lines, military field telephones, and small PBX installations when I was in high school) that was obtained approximately by hand-cranked generators. Bell Labs developed a magnetic generator with no moving parts that developed a strong 20-Hz subharmonic. It relieved the switchboard operator from the need to crank. The circuit was nonlinear, of course. Linear circuits can't generate subharmonics. Jerry -- Discovery consists of seeing what everybody has seen, and thinking what nobody has thought. .. Albert Szent-Gyorgi �����������������������������������������������������������������������
From: Vladimir Vassilevsky on 16 Mar 2010 17:42 Nils wrote: > Vladimir Vassilevsky wrote: > >>That used to be a common approach in the electronic music instruments >>before introduction of DSPs. >> > > > Absolutely. I'd like to add that subharmonics have been the way to bring > color into the sound of the trautonium. If you have seen classic movies > from the 60th and 70th you most probably konw the sound of it. Thank you for the reference. BTW, what if we take the Hilbert transform of the signal, find the frequency, multiply or divide the frequency by an arbitrary value, then integrate to get the phase, and then do the reverse Hilbert transform from that phase? Looks very straightforward. This method should be used under some fancy name... Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
From: glen herrmannsfeldt on 16 Mar 2010 17:50
Tim Wescott <tim(a)seemywebsite.now> wrote: (snip, someone wrote) >> using waveshaping we can generate odd harmonics, right? >> Using some tricks like adding square we can have even harmonics. (snip) > What you want from the subharmonics makes a lot of difference > to how you may generate them. It seems that there are many easy ways to generate higher harmonics, but subharmonics are harder. Any non-linear system will generate higher harmonics. One of my favorite is used for green laser pointers. Start with an IR diode laser, where semiconductor lasers are very efficient, send the beam through a non-linear crystal, such as Potassium Titanyl Phosphate, and get a nice green second harmonic of the input beam. The eye is much more sensitive to green than the usual red laser so that the result looks much brighter. Also, frequency multipliers work over a wide frequency range. > You could phase lock to a carrier, if it's well defined. Much more work, and only works over a narrow range. > You could use pitch shifting, if you're working with > instruments or voice. > You could use some bizarre parametric amplifier approach > if you -- well, I don't know _why_ you'd want to do that! One of my favorites was (maybe they still exist) an incandescent flame lamp with a filament that vibrated to look like a moving flame. There is a magnet inside, but the resonance is nowhere near 60Hz. The filament vibrates at around 2Hz. With the appropriate resonances, you can generate nice subharmonics, though without the wide frequency range of frequency mulitpliers. -- glen |