The sound of aliasing?

[ObsoleteAcc99]

[DELETED]

[Davias]

If a synth got aliasing, you can still oversample it with an oversampler plugin or by increasing your project samplerate, then u got 2 different sounding synths for the price of one ! and almost twice the number of presets. So when u buy an aliased synth, you double its value instantly !









(little joke of course :p )

[frejahel]

I just want to say thank you all for the interesting comments in this thread. I will make sure to demo ANA.

[TyFord]

Here's a piano track from a recording of a real grand piano with a pair of C414 mics. It's obviously distressed.

Is there a processor that can remove the artifacts?

https://soundcloud.com/tyford/piano-with-aliasing

[Tj Shredder]

I doubt that this is aliasing. A straight recording does not produce aliasing unless you sampled it with a higher sample rate and didn’t filter it before downsampling... In that case get back to the original and do it properly, or better keep it at the high rate...

[gentleclockdivider]

If a softsynth aliases when doing osc sync at 44 khz s.r , it just means bad coding .
No excuse for that in this day and age

[zerocrossing]

What aliasing sounds like depends on the material being played, because it's derived directly from that material.

For example, with high plucked notes such as an acoustic guitar, it might sound like birds chirping. With a low percussive sound such as a kick drum, it might just make the initial hit sound like a cardboard box. With a steady-state tone it might sound like fast frequency modulation. Aliasing is weirdest on bent notes like an electric guitar or synth lead, because the note might be bending upward while the aliasing shifts downward.

One of the most obvious manifestations of aliasing is spoken word encoded at low bitrates. Listen closely to the voiceover in the video linked by IrionDaRonin above, which ironically has noticeable aliasing. It's most noticeable on "S"s and "T"s.

In all cases, aliasing sounds bad. Our ears are especially sensitive to it because the aliased frequencies are not harmonically related to the source tones, making them stand out. It's like intermodulation distortion in that respect - even a little bit is offensive to the ear.

I think words like “bad” aren’t necessarily useful. Lots of acoustic instruments have enharmonic aspects to some part of the sound. Often in the attack of any thing that’s struck. There’s all sorts of noise, and aliasing can be used in creative ways, just like any kind of distortion.

Check out Mr. Alias Pro. It’s an awesome synth for getting nasty digital sounds.

[foosnark]

Here's a piano track from a recording of a real grand piano with a pair of C414 mics. It's obviously distressed.

Is there a processor that can remove the artifacts?

Sampling at low rates can have two effects:

- aliasing, which is reflection of the incoming signal below the Nyquist frequency. To avoid this you either need band-limiting or a lowpass filter to stop any incoming content from being above the Nyquist frequency DURING the sampling. After is too late.

- high frequency artifacts in playback above the Nyquist frequency of the recorded sample rate (not reflected!). To avoid this, you need to lowpass filter everything above the original Nyquist frequency at the time of playback (this is called a reconstruction filter).

For example, a 100Hz sine sampled at 5Khz, with no filters, gives you this:



5Khz is plenty to capture a pure 100Hz sine without aliasing, but you still need a reconstruction filter. So, try experimenting with a lowpass filter.

That said, I think the resolution (bit depth) of this recording is probably too low and you've got broadband signal-dependent noise (also not aliasing). And without some fancy adaptive FFT stuff that has other consequences, there's no fixing it really. A lowpass filter might make it sound more pleasant, but not clean.