Re: Spectrum analysis in JAMin is incorrect.

Yes, it's meant to map to octaves, rather than linear frequency. This tends to be what musicians expect, but isn't necessarily appropriate for other uses.

- Steve

On 2011-03-29, at 09:08, Dan wrote:

> The frequency scale isn't linear, it looks like it's at least roughly
> logarithmic, in which case it's quite possible that *is* what white
> noise looks like.
> 
> Best
> Dan
> 
> 2011/3/29 David Nielson <[email protected]>:
>> After changing the update frequency for the FFT analysis in JAMin, I
>> thought I'd see if I could fix another long-standing complaint of mine:
>> the graph never even gets close to the top of the window, so while there
>> might be really interesting things going on at low volume levels, I
>> can't see them.
>> 
>> It seems like the signal is getting some automatic gain control
>> (compression) before the FFT stage, separate from the compression that
>> JAMin is doing itself, to keep the visual of the signal visible. Passing
>> several test tones through to see what they looked like, I discovered
>> this in the 30-band spectrum page:
>> 
>> http://www.naptastic.com/david/jamin-graph-wrong.png
>> 
>> The input being analyzed is white noise. It displays correctly on the
>> HDEQ page, but here, well, that ain't what white noise looks like. (You
>> can ignore the peak indicators being in weird places; that's from the
>> other test tones I ran.)
>> 
>> So, I'm gonna jump back in the code right now, but I thought y'all might
>> want to be aware, there are some gremlins in there that it seems no one
>> has noticed before.
>> 
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> 
> 
> 
> -- 
> http://www.mcld.co.uk
> 
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