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Because of interesting spectral phenomena, I would like to shift the >20kHz content of my audio recordings to audible frequencies, so that I can listen to it. I tried the Audacity pitch correction feature, but didn't succeed. Any help much appreciated.

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  • $\begingroup$ What do you mean by "didn't succeed"? Did it crash, nothing was audible or too much low-frequency noise? $\endgroup$
    – jojek
    Sep 7 '20 at 8:50
  • $\begingroup$ Long time since I did this by just changing the sample rate of WAV file (HEX editor needed). $\endgroup$
    – Juha P
    Sep 7 '20 at 8:50
  • $\begingroup$ How did you collect these audio recordings? All audio equipment I've touched, even if it samples at 96 kHz, has analog anti-aliasing filters that cut off somewhere below 20 kHz. $\endgroup$ Sep 7 '20 at 8:54
  • $\begingroup$ @MarcusMüller: In my case hydrogenaud.io/index.php?topic=106205.0 $\endgroup$
    – Juha P
    Sep 7 '20 at 9:07
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    $\begingroup$ @W.H.G. I am more of a console guy. You can try to use sox with pitch effect. Something like: sox in.wav -r44.1k out.wav pitch -2400, which will shift the signal down by 24 semi-tones (2 octaves). So 40 kHz becomes 10 kHz, etc. Finally, it will save the output to 44.1k audio file. You might want to do some high-pass (or even band-pass) filtering on the output. $\endgroup$
    – jojek
    Sep 7 '20 at 11:53
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As suggested by @jojek:

SoX:

sox in.wav -r44.1k out.wav
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