Members grumphh Posted October 3, 2008 Members Share Posted October 3, 2008 Ok - i do know that aliasing is some frequencies being introduced into digital audio because of the math involved in said audio. But what i honestly don't know is how aliasing sounds (or maybe rather what i should listen for) - even though i do have 3 unashamedly digital synths (I guess it is because i mainly do weird sounds on these synths so that any weird frequencies get masked by the general weirdness i program in the first place) So does anyone of you have an audio example of a single sound that does alias? Link to comment Share on other sites More sharing options...
Members urbanscallywag Posted October 3, 2008 Members Share Posted October 3, 2008 If you had a really simple sound, like a single sine oscillator, aliasing would occur if you pushed the oscillator's frequency over 1/2 the sample rate. As you raise the frequency of that sine past the 1/2 sample rate, you've aliased, and as you continue to raise the frequency of the sine it will actually go "down" in frequency. So if I am sampling at 48 ksps (kHz) I can make a sine at 23 kHz (ignoring filters), but if I raise it to 25 kHz it sounds like 23 kHz because it has aliased and now "is" 23 kHz. Similarly 26 kHz will be 22 kHz...etc. Aliased Frequency = Sample Rate - Sine Frequency*Sine Frequency must be large than (Sample Rate)/2 In this example a pure sine is used, and aliasing doesn't sound too bad since there aren't any harmonics. As a signal with harmonics is aliased, the harmonic ratio is not preserved and the aliased overtones become inharmonic and probably don't sound too pleasing. I can try and make some samples today. Link to comment Share on other sites More sharing options...
Members mcpepe Posted October 3, 2008 Members Share Posted October 3, 2008 Link to comment Share on other sites More sharing options...
Members Delicious Lamprey Problem Posted October 3, 2008 Members Share Posted October 3, 2008 This is from Wikipedia: Temporal aliasing is a major concern in the sampling of video and audio signals. Music, for instance, may contain high-frequency components that are inaudible to us. If we sample it with a frequency that is too low and reconstruct the music with a digital to analog converter, we may hear the low-frequency aliases of the undersampled high frequencies. Therefore, it is common practice to remove the high frequencies with a filter before the sampling is done. Link to comment Share on other sites More sharing options...
Members The Real MC Posted October 3, 2008 Members Share Posted October 3, 2008 So does anyone of you have an audio example of a single sound that does alias? Anytime President Bush opens his mouth, that's aliasing. Link to comment Share on other sites More sharing options...
Members ElectricPuppy Posted October 3, 2008 Members Share Posted October 3, 2008 When I have a serious burrito and have to play some unsolicited butt tunes later? That's aliasing. Particularly the freepers. Those can get some nasty low-end alisasing. Never trust a fart. Link to comment Share on other sites More sharing options...
Members DXelectro Posted October 3, 2008 Members Share Posted October 3, 2008 I've got a clip but it seems my old free upload server causes my internet to lock and only reset of the router brings it back. When I find another upload site I'l post my clip. Link to comment Share on other sites More sharing options...
Members Acid Hazard Posted October 3, 2008 Members Share Posted October 3, 2008 It actually kind of reminds me of a bit of ring mod when you play way in the upper keys. You can hear these strange artifacts in the the audio that def aren't supposed to be there. Link to comment Share on other sites More sharing options...
Members P321 Posted October 3, 2008 Members Share Posted October 3, 2008 Might be a noob question, but I bet you'd be surprised at how many around here don't know the answer ..Anyway, here's a quick example of some V-Station Aliasing. An audio clip speaks a thousand words Link to comment Share on other sites More sharing options...
Members Yoozer Posted October 3, 2008 Members Share Posted October 3, 2008 Anytime President Bush opens his mouth, that's aliasing. You mean polarizing Link to comment Share on other sites More sharing options...
Members ClavAnother Posted October 3, 2008 Members Share Posted October 3, 2008 Never trust a fart. ever. Link to comment Share on other sites More sharing options...
Members grumphh Posted October 3, 2008 Author Members Share Posted October 3, 2008 Might be a noob question, but I bet you'd be surprised at how many around here don't know the answer ..Anyway, here's a quick example of some V-Station Aliasing. An audio clip speaks a thousand words Thank you very much - more than a thousand words really - i get it now And thx to all you others, my point was that i have read (and partly understood) the theory behind aliasing but i didn't have a sonic reference. ...and no wonder i have never been able to isolate aliasing before, my sounds sound like that all the way down to the lowest octaves Link to comment Share on other sites More sharing options...
Members DXelectro Posted October 3, 2008 Members Share Posted October 3, 2008 Urbanscallywag has got it right. As a signal with harmonics is aliased, the harmonic ratio is not preserved and the aliased overtones become inharmonic and probably don't sound too pleasing. I would add that sometimes you can use aliasing to your advantage. The reflected frequencies sometimes can sound interesting and pleasing. I played an upward chromatic scale on the DX7 with a simple sound that aliases and it sounds sweet once it begins to alias. Too bad there is something wrong with my broadband. I can't upload anything anywhere using my Vista / XP / Explorer / Firefox (all combinations) machines. Link to comment Share on other sites More sharing options...
Members urbanscallywag Posted October 3, 2008 Members Share Posted October 3, 2008 It actually kind of reminds me of a bit of ring mod when you play way in the upper keys. I was almost going to put that in my original post but I didn't. The reason is as mentioned in the original post that harmonics become inharmonic as they fold over the 1/2 sample rate. Ring modulation and frequency shifters cause inharmonic tones also. Link to comment Share on other sites More sharing options...
Members urbanscallywag Posted October 4, 2008 Members Share Posted October 4, 2008 Might be a noob question, but I bet you'd be surprised at how many around here don't know the answer ..Anyway, here's a quick example of some V-Station Aliasing. An audio clip speaks a thousand words Wow that's bad news. Link to comment Share on other sites More sharing options...
Members P321 Posted October 4, 2008 Members Share Posted October 4, 2008 Wow that's bad news.I should just say that the aliasing in that clip is primarily caused by the V-Stations FX if memory serves, not its actual oscillator code.. So its nowhere near as bad as the clip suggests Link to comment Share on other sites More sharing options...
Members listenman Posted December 9, 2016 Members Share Posted December 9, 2016 I had the same question recently and stumbled upon this. I could not access the previous link posted by P321. Here's a youtube video I found where you can hear aliasing. Link to comment Share on other sites More sharing options...
Members moogerfooger Posted December 14, 2016 Members Share Posted December 14, 2016 watch this [video=youtube;Ic4bVbXfdW4] remember that if you sample at at least twice the frequency range -- no aliasing happens, 44.1K is twice 22.k which is way above most peoples hearing Link to comment Share on other sites More sharing options...
Members Cydonia Posted December 19, 2016 Members Share Posted December 19, 2016 Oh, Hai ! :wave::wave: It looks like this : And it sounds like this : Oh and... I haz a Kronos. And where is everyone ? Link to comment Share on other sites More sharing options...
Members 1001gear Posted December 19, 2016 Members Share Posted December 19, 2016 Play only voice patches till you get it. Link to comment Share on other sites More sharing options...
Members Cydonia Posted December 27, 2016 Members Share Posted December 27, 2016 Link to comment Share on other sites More sharing options...
Members 1001gear Posted January 5, 2017 Members Share Posted January 5, 2017 Dead is the latest thing. Link to comment Share on other sites More sharing options...
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