Wait, so aliasing occurs when the signal is sampled? <br>So if i have this patch :<br><br>[adc~]<br>|<br>|<br>| <br>[dac~] <br><br>and if the signal already contains frequencies above the Nyquist, i will get aliasing? I generally use my electric guitar as the main audio source, and i&#39;m assuming that it has lots of harmonics beyond the Nyquist frequency (especially when the strings are new), yet i never noticed any distortion of any sort. I might have a bad ear... Or is it just that the energy of the upper harmonics is too low for me to notice when they cause aliasing? <br>
<br><br>Pierre<br><br><div class="gmail_quote">2010/4/1 Matteo Sisti Sette <span dir="ltr">&lt;<a href="mailto:matteosistisette@gmail.com">matteosistisette@gmail.com</a>&gt;</span><br><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<div class="im">&gt; Correct, nothing played back at original sampling rate will alias.<br>
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It _won&#39;t_ alias; it may already _have_ aliased when sampled in the first place.<br>
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Aliasing occurs when sampling.<br>
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When you digitalize (ADC), you are sampling. When generating a waveform mathematically, you are sampling the mathematical function at the very moment you compute its value at discrete points.<br>
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When you play back a signal at a different speed than the original, you are _resampling_ it, that is, theorically, interpolating it and then sampling it again, and it is the sampling stage, not the interpolating one, that produces the aliasing.<br>

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The interpolation, since it cannot be an ideal interpolation, may introduce other noises or artifacts, not aliasing as far as I can see.<br><font color="#888888">
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Matteo Sisti Sette<br>
<a href="mailto:matteosistisette@gmail.com" target="_blank">matteosistisette@gmail.com</a><br>
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