How To Divide the Frequency Spectrum Logarithmically?
Jun 18, 2008 at 8:24pm
How To Divide the Frequency Spectrum Logarithmically?Hello, I am trying to build a vocoder and was wondering how I might divide the frequency spectrum up according to its loudness as opposed to frequency? For instance, if I wanted 8 bands in my vocoder, is there an equation I can use to determine the best possible frequency spectrum for each band? 

Jun 19, 2008 at 1:53am
You could research “Bark” of “Mel” coefficients. They help slice the > Hello, I am trying to build a vocoder and was wondering how I might divide the 

Jun 19, 2008 at 2:22am
That’s exactly what I’m looking for. Since human hearing is logarithmic (lower frequencies are much louder and more distinct than higher frequencies), I am looking for a method to divide the frequencies so that each frequency range contains the same amount of energy. Though I’ve decided to just make the frequencies variables, as their manipulation midvocoding could most likely produce some cool effects :D 

Jun 19, 2008 at 3:08am
Well that’s mostly true, but don’t confuse perceptual loudness and frequency resolution. Check out the equal loudness curves http://en.wikipedia.org/wiki/Loudness – sensitivity does vary with frequency (as well as many other things) but the dependence is not simple (or logarithmic). Frequency resolution is logarithmic however. The critical bandwidth of the human cochlea is something like a minor 3rd as far as I remember, and of course the number of Hz that a minor 3rd spans grows exponentially with frequency. G’luck with the vocoding! Aengus. 

Jun 19, 2008 at 3:28pm
Quote: aengus wrote on Wed, 18 June 2008 21:08 I guess that is the question, how do you calculate the position 

Jun 19, 2008 at 4:13pm
On Jun 19, 2008, at 8:28 AM, Anthony Palomba wrote: mtof or mtof~ are probably the most direct way in Max. C Chris Muir 

Jun 19, 2008 at 4:29pm
Kyle Kaplan schrieb: In the end this is a matter of taste, but definitely look into mtof, Stefan – 

Jun 19, 2008 at 5:33pm
thanks for the advice, hadn’t thought of using mtof but now that you mention it, it makes perfect sense. 

Jun 19, 2008 at 8:10pm
I’d also look at the frequency ranges traditionally used for vocoders The Moog MuRF uses: Peter McCulloch 

Jun 20, 2008 at 1:32pm
A tempered minor third is the frequency ratio sqrt(sqrt(2)), ie pow(2, 0.25). A tempered major third is pow(2, 0.333333). Analog vocoders only approximated thirdoctave divisions, and I don’t suppose for a moment that the cutoff frequencies on a Moog were centaccurate. You can either use some hardcoded numbers, or do the math. It’s not hard if you got past logarithms in high school. – P. 

Jun 20, 2008 at 5:09pm
The Moog ratios worked quite well. In the spirit of ‘sharing is fun’ here’s my super simple 8band vocoder for anyone who’s interested. wasn’t really sure on the Q, so I set it to something that sounded OK and attached some flonum boxes for personal adjustment. 
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