[music-dsp] OSC problem on STM32F4Discovery

Tim Goetze tim at quitte.de
Tue Apr 10 06:02:47 EDT 2012


[Julian Schmidt]

> here are some screenshots...
>
> the beating bell shape on 440Hz sinus with 84 harmonics
> http://i.imgur.com/B4s0M.png

I think that beating could well be caused by Nyquist-mirrored 
harmonics.

> a simple sine table 220Hz
> http://i.imgur.com/hPKj1.png

In both plots, there's also a strong signal at 1 kHz (likely being 
accompanied by harmonics at kHz intervals but that is hard to make out 
in the spectrum plots given their emphasis on the low end.)

Cheers, Tim


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