[sdiy] 440Hz Reference Oscillator.

[Andre Majorel]

On 2006-06-06 19:37 +0100, Seb Francis wrote:
> Tim Parkhurst wrote:
> >
> >I know it wouldn't be the most portable solution, but would it help if
> >someone just posted some WAV or even MP3s of 440Hz sine waves? Someone
> >with a very stable, lab style function generator could do it easily.
> >Maybe even post octaves above and below. It wouldn't be the best
> >solution in the world, but it would be a handy tuning reference. I
> >know I'd appreciate having a known 440Hz tone that I could access.
> 
> I know this is synth-diy and we all love playing around with old and 
> quirky ways of doing things, but doesn't everyone have a computer?  Just 
> open your favourite Sound Forge / Wavelab / etc. audio editor type 
> program and create a sine wave of any frequency you desire (e.g. in 
> Sound Forge: Tools->Synthesis->Simple..).  The accuracy will be 
> dependent only on the sound card used to play it back, but you can be 
> sure this will be *much* better than any analog oscillator.

Yep. If you're willing to depend on the accuracy of a sound card,
there are more expedient ways.

  ausin -f 440 | dd bs=2 count=$((44100 * 60)) | lame -rxmm - - >440hz.mp3

There are people who roll their own test signal CDs that way.

(Interestingly, while oggenc generally performs better than lame
on music, it can't encode a simple 440 Hz sine without producing
*very* noticeable artefacts. Even at -q10.)

-- 
André Majorel <amajorel at teaser.fr>
http://www.teaser.fr/~amajorel/