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Troubles with playing back 96khz sample at 44.1khz

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I'm working with some recordings in 96khz and 192khz. The recordings has a lot of content over 20khz that sounds nice when pitched down.

I'm running Kyma in 44.1khz and when I play back a sample file (that is in 96khz) the content above ~22khz gets "mirrored" down into the audible range creating artefacts.

If I open the file in the Kyma Wave editor and change the sample rate to 44.1khz (and say yes to interpolation) the problem disappears.

If I run Kyma in 96khz the problem disappears as the ultrasonic content is now played back correctly.

Is there a way to play back a sample file recorded at a higher sample rate without this "mirroring"?

(Maybe I am missing something obvious..?)



asked Jan 9, 2019 in Using Kyma by andreas-frostholm (Practitioner) (390 points)

1 Answer

+1 vote
Best answer

Frequency content above half the sample rate cannot be represented in a sampled system (so any frequencies above SR/2 appears to be a lower frequency sine wave that goes through those same points; the result sounds like frequencies that are higher than SR/2 "reflect" about SR/2 down to a frequency that can be represented).

If you use the Wave editor to resample the waveform for a lower sample rate, it does perfect interpolation (effectively equivalent to an ideal lowpass filter) to remove any content above half the sample rate.

answered Jan 9, 2019 by ssc (Savant) (125,720 points)
selected Jan 10, 2019 by andreas-frostholm
Thanks! This was my understanding as well. I like that Kyma is not doing any "behind the scenes" sample rate conversion.