You are already assuming that Nyquist can be violated despite a brick wall filter, a thesis that has to be proven in the first place.
Hans
I did mention a while ago a guitar string pluck. If a lead guitarist pulls a string taut, then let's go, does the pickup filter the start? The string goes from full amplitude zero velocity to full velocity center of travel at the string frequency. A 1khz note, that represents full amplitude in 1/4 cycle.
Any percussion instrument, I would look at as well.
Ed: the example I posed, exponentially modulated sine, has identical zero crossings throughout.
Mountain bob...now that I select all/copy, the iPad never times out. I am sure the one time I forget, I'll lose the entire post. Again, thanks.
Jn
No, I do not believe he assumed that at all.
The discussion is about musical content that is removed because it would violate nyquist if it were not filtered out first.
Jn
Which of course is taken care of by the aliasing filter in the A/D so no violation will actually occur. If a good implementation.
Discussing PCM while omitting that rules around the A/D process is not meaningful as I see it. It's just theoretical farting 🙂
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My excel convolution was to find a signal that was a modulation of a fourth harmonic by the fundamental in a periodic waveform. I setup a simple subtraction analysis, removing each frequency one at a time. What was left was a modulation.
I had been hoping to use convolution to show the fundamental was indeed modulating the fourth, but the results were not good.
I also tried it on an exponentially decaying sine, again no joy.
The discussion at hand, otoh, is about musical content that will violate nyquist if not filtered.
Great post. The recording craft isnt learnt over night. I say a live gig is like a play a record is like a movie. Great sound is the object but life gets in the way. Drunk musicians, overbearing producers, the loudness wars, earbuds etc, etc.
As far as live gigs, musicians like there own mix, usually more me except the drummer who has too much drums, so stage monitors or lately in ear monitors.
....OK + but mosts above my head...
Ehhh, why is this in need of discussion? Fart analysis :-DD
But, than I have the answer: Anything entered above Fs/2 will violate Nyquist. QED. I.e. any part of a signal that exhibits a steeper slope than a 22,05kHz sinus at zero-crossing will violate.
Isn't it as simple as that?
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Almost. Look back at the sin(20)cos(4) stuff.. Nothing in that waveform has a zero crossing slope that exceeds the 22.05, yet frequency content is certainly above.
I gave an example (the guitar string) where the start absolutely violates Fs. The question of the day is, are humans sensitive to the leading edge content of that guitar note? If we remove some of the leading edge content because it starts too abruptly, is that loss audible?
Jn
Well, this is where JC indicated a wider BW and thus a faster Tr was audible and was a difference between LP and CD that he and others is sensitive to.
Which then lead into microphone BW. And further back, that 40KHz BW would have made a better CD standard etal
So..... everything is starting to fall into place...
Back in the Day ... Pre CD, we learned that a BW of -3dB at 40KHz was the minimum BW to cause no detectable change. If when CD was developed, that known criteria was used, we might not be having this discussion.
THx-RNMarsh
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I am mainly bothered by additive processes mixed in with modulation. The damped sine wave is formed by multiplication I don't see an easy analog to the trig identity.
Yes, leading edge ( and trailing) transients are quite important to accurate sounding playback.
I know people here think it’s bs, but it’s what makes the ‘prat’ correct.....call it what you want but the whole time smearing or removal/lack of content, it messes with the believability in playback.
Just glad the iPad trick worked for ya......anything to stop the whining! 😀
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Glad you see it my way Hans! 😛
It is really just as simple as doing it.....technology is all in place.
It’s heading there naturally anyhow, just like cassettes gave way to the cd......cd will give way to hi-res.
It is really just as simple as doing it.....technology is all in place.
It’s heading there naturally anyhow, just like cassettes gave way to the cd......cd will give way to hi-res.
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Isn't it more likely due to a reduced phase shift through the audio band being audible?
Well, if the leading edge has frequency components that is beyond our ability to hear - then they are .... not audible and there is no loss losing them in an anti-aliasing filter ;-D
There are a lot of audio events around us daily that has content that we don't hear. So also a guitar - but we don't mind, as we don't know.
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