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audiodef
Joined: Sep 05, 2011 Posts: 726 Location: LFO1
Audio files: 53
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Posted: Mon May 27, 2013 6:40 pm Post subject:
Fourier analysis & adding harmonics Subject description: Experimentation advice sought |
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I'm doing some experimentation and for that, I want to:
1. Filter out everything above a certain frequency (probably 250 Hz). This is easy enough.
2. Deconstruct the signal as much as possible. I'm thinking Fourier analysis.
3. For each single frequency present, add n number of harmonics at amplitudes yet to be determined.
4. Mix that back into the original signal.
This isn't the experiment - just something I want to do as part of it. I figure you guys might know some way to make these steps happen. _________________ There's an invisible radio gnome playing a gong from a flying teapot - don't miss out! |
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Cynosure
Site Admin
Joined: Dec 11, 2010 Posts: 966 Location: Toronto, Ontario - Canada
Audio files: 82
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Posted: Tue May 28, 2013 3:44 am Post subject:
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You want to remove harmonics, and then add them bqck again? why not just leave them there to begin with?
I think u might be able to do some of this with isotope Iris. You can get a ten day trial on their website. _________________ JacobWatters.com |
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audiodef
Joined: Sep 05, 2011 Posts: 726 Location: LFO1
Audio files: 53
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Posted: Tue May 28, 2013 6:02 am Post subject:
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Oh, no, I don't want to remove harmonics. I want to add additional harmonics, but under very controlled circumstances. And to add a further point, the signal in question is actual music, not just a tone, patch or sound. _________________ There's an invisible radio gnome playing a gong from a flying teapot - don't miss out! |
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robsol
Stream Operator
Joined: Apr 24, 2009 Posts: 2492 Location: Bristol UK
Audio files: 495
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Posted: Tue May 28, 2013 6:09 am Post subject:
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To add harmonics to a signal, just distort it. Maybe you should look into waveshaping. It is hard to work out exactly what you want to do though... _________________ Muied Lumens Sub Forum
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Acoustic Interloper
Joined: Jul 07, 2007 Posts: 2067 Location: Berks County, PA
Audio files: 89
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Posted: Tue May 28, 2013 6:15 am Post subject:
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The low-pass filtering does remove harmonics, along with any high-frequency inharmonic signal components.
ChucK's audio analysis ugens would give you a way to operate in the frequency domain and then convert back. I haven't done that in ChucK, but I am sure folks on the ChucK mailling list have.
I did something along these lines to allow myself to sing in three-part harmony using a Max/MSP patch with an fft and ifft a few years back. Pure Data (PD) appears to have the required ugens, and like ChucK it is free. _________________ When the stream is deep
my wild little dog frolics,
when shallow, she drinks. |
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audiodef
Joined: Sep 05, 2011 Posts: 726 Location: LFO1
Audio files: 53
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Posted: Tue May 28, 2013 6:39 am Post subject:
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Hm... I don't want to distort anything. The low-pass filtering would be just to remove everything above 250 Hz, harmonics and all. That's OK.
I figured I might be using ChucK or Supercollider or something like that.
I've been way too vague, and I'm sorry. I just didn't want to get boring.
What I'm doing is experimenting with ways to make bass richer for people with cochlear implants who listen to music. See, bass is a bit thin. What I've found in some preliminary testing is that a fundamental frequency - a sine at 55 Hz - sounds noticeably fuller when I add two harmonics at 110 and 220 Hz with relative amplitudes of 1/4 and 1/8 (I started with the first harmonic being at a relative amplitude of 1/2, but that just resulted in octave unity). This was the perceived result with my implant.
So now I want to see if I can apply this by breaking down a music signal, filtering out the lowest fundamentals, and adding harmonics in the same way. If this does anything useful for perception, I can send this info to Advanced Bionics, and if they're so inclined, they can translate that into a future software upgrade for their external processors. _________________ There's an invisible radio gnome playing a gong from a flying teapot - don't miss out! |
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[Q]
Joined: Sep 09, 2010 Posts: 413 Location: Continuum
Audio files: 57
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audiodef
Joined: Sep 05, 2011 Posts: 726 Location: LFO1
Audio files: 53
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Posted: Tue May 28, 2013 8:22 am Post subject:
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SPEAR looks very useful, thanks!
I was able to run it on WINE (although I had to upgrade to the latest unstable version to run it). _________________ There's an invisible radio gnome playing a gong from a flying teapot - don't miss out! |
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