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[i]Please Help Me![/i]: Waveform vs Envelope:

Discussion in 'Sound Science' started by TheSonicTruth, Sep 26, 2018.
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  1. SoundAndMotion
    So @TheSonicTruth reminds us of his passion (which most of us already know)... and tells us he thinks he can look at waveforms to see that different versions of a song will sound different. This sounds like a reasonable assumption, even if it's wrong. For him to understand, an explanation of why his assumption is wrong must be clear to him.
    I seem to recall several "tellings", but none stuck; I assume because they were not made clearly enough for @TheSonicTruth .
    @bigshot continues, but discusses "quality", not "difference".
    @TheSonicTruth knows that if the waveforms look different, the waveforms ARE different, but goes on to assume that necessarily means they will sound different. He makes clear he means "different" NOT "Inferiority or superiority".
    I understand the frustration... when some things have been explained and @TheSonicTruth stubbornly contradicts some facts, you (and others) lose interest in further explanations. But you mixed difference with quality, so he answered.

    But, nearly a year later, he asks nicely for the explanation you offered contingent upon his listening. He's willing to listen:
    And this counts as the explanation!?!? Sheesh!

    @TheSonicTruth: It's late here and I'm going to sleep soon. But here is a quick and simple-minded attempt: you know 30kHz is an example of something inaudible, right? So let's use that as an example, a placeholder, for everything inaudible, for now. Imagine I take the signal from the top of your avatar and ADD to it: (a 30kHz signal with the envelope of the bottom of your avatar MINUS a 30kHz signal with the envelope of the top of your avatar). That may look quite strange zoomed in, but all scrunched up, it should look like the bottom of your avatar. ...AND!!! sound identical to the top to human ears.

    I have no doubt there are errors in my example (I'm half asleep!), but do you get what I'm trying to say? The different envelopes may look different, and the waveforms are different, but they sound the same, because the differences are not audible.
    Last edited: Sep 6, 2019
  2. TheSonicTruth

    Please clarify?
  3. sander99
    Last edited: Sep 9, 2019
  4. bigshot
    He didn't ask for an explanation. He asked what he was wrong about. You can't assume that because a waveform looks different, it will sound different. That is the truth and anyone who has worked with waveforms knows it.

    Just look at that clear as mud explanation above. People are just performing, they aren't answering questions. I answer questions clearly.
    Last edited: Sep 7, 2019
  5. sander99
    Probably it was a bad idea, it didn't turn out to be vey clear indeed, but I was just trying to clarify SoundAndMotion's example (thinking maybe TheSonicTruth doesn't understand what adding signals means, if indeed he doesn't it would be impossible for him to understand what SoundAndMotion was saying).

    Which brings me to a question: does anyone know a website with a compact and clear explanation of some of the basics of signal theory, like what it really means that a signal contains certain frequencies, that every signal can be decomposed into a collection of sine waves, and that the frequencies of all those sine waves are actually what is meant with the frequencies that are present in a signal? And what that means for a bandlimited signal, why there can't be square waves or sawtooth waves etc. in there? If someone has at least a basic understanding of these things it is much easier to explain many other things about audio to him/her. Then someone can say "read this first and then I can answer your question"...
  6. TheSonicTruth

    Alright, instead of going through that whole Sturm und Drang you presented a few posts above, how about this:

    1. I load the same exact file into my DAW - twice. Or just copy it within the DAW.

    Good! Two copies of the exact same song file, producing identical wavelopes, sound and look precisely the same.

    2. I add the same 30kHz tone to one of them.

    3. I observe both wavelopes, and notice that one of them now looks different.
    But when I listen, I hear no difference. Why? The tone added to one of them is ULTRASONIC!
    (I probably wouldn't hear 16kHz tone, let alone 30, at my age, lol!)

    4. This time, I add something less stratospheric, say 2kHz or even 400Hz, after undoing the 30kHz addition.

    5. The wavelope I added the 2K to now looks different, and to a greater degree different, than the unaltered one.
    It also SOUNDS different, because the change I made is well within the range of human hearing.

    So in step 3, we see a difference between wavelopes, but cannot hear it.

    In step 5, we both see and hear a difference between them. So bigshot: it depends on both the amount and type of change we are making to one of the files to both see and hear a difference.

    6: To take it a step further, applying, maybe, some EQ, mild dynamic compression, peak limiting, and makeup gain to one of them, typical commercial mastering stuff, to one of the files.

    7. If, in the case of step 6, one sees a difference between the unaltered and the compressed, peak limited, etc. wavelope, but cannot hear a difference...

    ...then they're probably DEAF. Sorry bigshot!

    Again, the audible difference between files that present different looking wavelopes depends on exactly what kind of change was made to one of them.
    Last edited: Sep 7, 2019
  7. sander99
    Yes, nobody was saying the contrary. I was just trying to explain SoundAndMotion's example that shows that there exist cases in which the difference is not audible. I don't have much more then that to add to this discussion. I did not follow the entire discussion and I don't know what kind of changes they do in remastering that significantly change the waveform and envelope without much audible difference. So I will stop "improvising" (which I think is what I was doing rather than "performing").
  8. gregorio
    Ah but you're not aware of various other threads that occurred prior to this one, where we went through in this exact same process more than once and that this thread is effectively part of that same loop. IE. A rant based on a bunch of misinformation, that was refuted, which led to some heated exchanges and eventually the assertion that "He's willing to listen" at which point it was explained in a variety of ways: Simply, in considerable detail, basic terms, complex terms, supporting evidence, visual evidence, etc. And in fact he wasn't "willing to listen" to any of it, in any explanation style by various different people in any of the different threads here or apparently on a number of other audio forums either.

    So to answer your question; you're right, that doesn't count as the explanation .... but as there apparently isn't anything that would count as the explanation as far as thesonictruth is concerned, there's no point in just repeating one of the explanations that he's not willing to listen to anyway. So might as well just provide a simple one line truth and save the time/effort!

    It's worth mentioning what castleofargh has already pointed out: There's a couple or so people here in this sub-forum who refute crazy audiophile beliefs/notions (though maybe not as often as bigshot or me) and post rational, correct/accurate information that's relevant and in agreement with the facts/science in a variety of different "audio" areas .... Except in one specific area they seem to have a particular passion for. And in that one area, they become the very thing they argue against in other areas; their posts are dominated by false conclusions/assertions and incorrect information, they become completely irrational, refusing to accept any explanation, fact or evidence which questions their belief.

  9. TheSonicTruth

    The changes to a song file - both audibly and to its representative wavelope - resulting from remastering can vary widely - from simply removing background noise(s) and/or left-right channel balance, to the more commercial style of remastering(ostensibly represented in my profile avatar) involving sometimes heavy doses of EQ, DR compression, and varying degrees of final peak limiting and make-up gain. The goal being to get the loudness of IE: a 1980s pop CD release to compete somewhat with the loudness of something more recent.

    If it is mostly loudness processing, and at that mostly limiting, then yes, you might have an original and remastered wavelope that sound - for the most part - the same, except that the remastered version will playback much louder than did the original, given the same volume setting or monitor level.
    Last edited: Sep 7, 2019
  10. bigshot
    You can perform all kinds of modifications to the audio file and the waveform will look different. But until the change crosses the JDD (just detectable difference) line, it’s going to sound the same. You can’t assume that a different looking waveform sounds different because that is all a matter of degree, and it’s governed by the abilities of our human ears. We can measure far beyond our ability to hear. This really isn’t complicated or difficult to explain.
  11. TheSonicTruth
    Here you go again bigshot, telling me what you think I should or should not be hearing. Do you work for the guvamint?

    Well I can use my own ears, and my ears tell me what sounds different or sounds the same to me, thank you very much.

    Even if the only difference is that one is louder than the other, but otherwise timbre-wise the same.
    Last edited: Sep 7, 2019
  12. bfreedma
    Quoted without further commentary.
    Last edited: Sep 7, 2019
  13. TheSonicTruth

    You'd be in the same boat if you had to deal with bigshot. I did listen, and read his explanation with an open mind. And then he comes up with his "JDD" just-detectable-difference nonsense, claiming that I should not hear a difference between versions of the same file with different waveforms, no matter what the change was.

    With two copies of the same song file loaded in the DAW, one with heavy EQ and or DR compression applied to it, the other not, you'd have to be JDD - Just Damn DEAF to not hear the difference between them!
  14. bfreedma

    That’s not what he posted. If you weren’t so busy determined to be right/posting insults, you might be more ready to listen.

    Of course with heavy EQ, there might be audible differences. I haven’t seen anyone suggest otherwise. The question was whether visibly different waveforms were always audibly distinguishable, not that they always sounded identical.
  15. TheSonicTruth
    With heavy EQ, or aggressive compression, there will be audible differences, compared to something done well above the threshold for human hearing.

    But I started this thread initially to determine if there is a strict delineation between a 'waveform' and an 'envelope', since this distinction in terminology seems to matter so much to 'geoff' and the other guys in Usenet rec.audio.pro.
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