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Author Topic: Of the infinite properties of transducers and other physical phenomena  (Read 6685 times)

Johnny B

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Paul,

I loved the part where you challenged
all those bright people who made the
dire predictions of doom.

Going off topic a little,
I once had a long discussion
with a Buddhist monk, of all people.
He carefully explained that everything
in the universe is vibrating at some level,
even objects that appear solid, and our duty
was to bring ourselves into harmony with
these mysterious universal vibrations.
I guess this may partially explain
why so many musicians such as Tina Turner and
Herbie Hancock practice Buddhism.

And it makes me wonder about a dumb idea
that it might be cool to experiment with
'verters that were speed and filter adjustable
in an attempt to bring it more into the
harmony of the programme material.

Goofy idea probably, but fun to contemplate.
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"As far as the laws of mathematics refer to reality,
they are not certain; as far as they are certain,
they do not refer to reality."
---Albert Einstein---

I'm also uncertain about everything.

Curve Dominant

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Quote:

posted by Paul Frindle:
A fundamental difference between an IIR filter and an FIR is that the FIR only computes it's response over a limited range of time (its time window). Therefore the only reason the impulse response is 'finite' is that once the impulse has been calculated for all the terms contained in the FIR filter - no more calculation is done and no more output results. Can anyone think of any natural system where there is resonance and filtering where this is true - surely not?


The reason I re-posted that, is:
1) in the sincere hope that someone actually READS it, and
2) in the sincere hope that someone actually seeks to UNDERSTAND it.

Three whole pages of bandwidth on GM's forum deserves to be justified by some level of UNDERSTANDING what one is reading.

Zoesch may have infinite time on his hands to compose circular debates which lead nowhere, but some of us do not. Simply debating for the sake of debating is not an excercise which serious engineers waste their time with.

The subject of filters, be they infinite or finite, DOES have some bearing on our craft.

Confusing the issue with a muddy mess of half-baked pseudo-technical babble, does not.

It might help us respect the existence of this thread if there was some real engineering issue which inspired it, some problem which needed to be resolved, or some opportunity which could be addressed. A reason, a why.

Something like, "Of the infinite properties of transducers and other physical phenomena...because I have this mix which isn't quite gelling for some reason..." or,

"Of the infinite properties of transducers and other physical phenomena...because I'm not getting a satisfactory cymble sound..." or,

"Of the infinite properties of transducers and other physical phenomena...because I built this DAC and it sounds kinda crappy - help!"

In other words...

What's the question??

Nika Aldrich

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Eric,

The question had to do with the tremolo thread on this site.  Chuck had stated that we can't ever reconstruct a waveform because it needs infinite time in order to be band-limited (true).  I said that that's what IIR filters do - they give infinite time so that the waveform can be band limited.  I then explained that all transducers do this, including speakers, ear drums, microphones, etc.  Zoesch challenged that I was wrong and that transducers are FIR devices.  I said that, in the spirit of keeping Chuck's thread on topic, perhaps Zoesch and I had better move this subject off to another thread and hash it out without confusing the issues in Chuck's thread.  Thus, a new thread was started to discuss whether or not transducers really are IIRs.  As of yet I think just about everyone in the thread agrees that transducers are IIR filters and that FIR filters can only exist in the world of mathematics except for Zoesch.

I hope that explains the nature of the thread.  The issue is actually somewhat important with regards to foundational knowledge of why Nyquist works, IMHO.  Chuck's thread has been some degree of evidence of that.

Nika.
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Curve Dominant

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Quote:

posted by Nika:
Eric,

....

Zoesch challenged that I was wrong and that transducers are FIR devices.



Ouch.

It took 3 pages to correct THAT??!??

Aye aye aye!

Sorry guys, but I got work to do...

Zoesch

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Nika Aldrich wrote on Wed, 23 June 2004 14:56

As of yet I think just about everyone in the thread agrees that transducers are IIR filters and that FIR filters can only exist in the world of mathematics except for Zoesch.



Do me one favor and don't misquote me:

1)I have never said that FIR filters exist in the real world, they are only valid mathematically
2)I am challenging not the mathematical approximation of transducers IN A FEEDBACK CONFIGURATION to be IIR filters, I am challenging the blind belief of the "physics impaired" that a)equilibrium does not exist, b)that equilibrium means absolute zero, c)that inferred behavior is the same as observed behavior and e)That the model is equivalent to the simplified model.
3)BTW, so far, I haven't seen you come and describe how a force of 1 mN can move a 20 gram paper cone @ 1 p.a.

Of course, this would've been simplified if we had stuck to the part of the impulse response where you incorrectly assume that the system is still oscillating beyond measurable parameters (Seriously, I want to see that theory supported on say the potential barrier between Boron and Silicon Oxide) and I am stating that the response is constant and unmesurable.

Maybe you have never spent any time behind measurement equipment, I don't know your background and I won't assume either way.

To me, unsurprisingly this all comes from the standpoint of mathematic "correctness" which is a dangerous position to take, specially considering the tag team you seem to be forming here.

As I don't know what you two are about maybe you want to step down from the spin machine soapbox and display a behavior more fit to the forum's intent and forms and the discussion at hand.
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Nika Aldrich

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Zoesch wrote on Wed, 23 June 2004 08:11


Do me one favor and don't misquote me:

1)I have never said that FIR filters exist in the real world, they are only valid mathematically



OK.

Zoesch wrote on Thu, 17 June 2004 00:36

Nika Aldrich wrote on Thu, 17 June 2004 03:25

Transducers are indeed infinite impulse response filters in that the impulse response of them has infinite characteristics, and when convolved with a stimulus the response does ring infinitely.  Indeed the devices listed all have infinite impulse responses and they all are convolved with stimuli.  



To which I say, no they are not... infinite impulse response means that the response to an impulse exhibits infinite oscillations, this is what you would expect from a full-feedback system with no damping.

A transducer won't exhibit that behaviour, if excited with an impulse it will show a finite number of oscillations until it reaches equilibrium (Goes back to zero). If excited with a step function it will experience a finite number of oscillations until it reaches equilibrium.


Nika
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davidstewart

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Or...(as quoted from near the bottom of page 3 of the Tremolo thread....)

Zoesch wrote:

"Actually, there's no feedback loop in acoustic instruments (Or in normal transducers) so their behaviour is completely different from that of an IIR filter..."


Anyone in their right mind would conclude that "completely different from that of an IIR filter..." means that it MUST be an FIR filter. There is no in between choice. (And of course that would be the wrong conclusion.)

It seems (to me anyway) you have confused this issue and, for some reason, are reluctant to simply back away from it. IMHO this "dancing" you are doing is serving to muddy an otherwise pretty clear and easily understood reality. I don't see it as helpful. Perhaps this discussion should die.

Sorry to pile on, but it's gotten beyond ridiculous at this point.
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Paul Frindle

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Zoesch wrote on Wed, 23 June 2004 08:11


As I don't know what you two are about maybe you want to step down from the spin machine soapbox and display a behavior more fit to the forum's intent and forms and the discussion at hand.



Spin machine soapbox!!

Ok - if I am one of the people respectfully refered to as 'you two' I am more than happy to 'step down', got better things to do anyway. I was honestly only trying to help. Sorry if this constitutes a behaviour which is 'unfit to the forum's intent'.

Please understand respectfully that I absolutely NEVER waste my valuable time peddling dishonest 'spin', nor do I go out of my way to gratuitously upset people Sad

Consider me dismissed - err - gone Smile
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Zoesch

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davidstewart wrote on Wed, 23 June 2004 22:59

Anyone in their right mind would conclude that "completely different from that of an IIR filter..." means that it MUST be an FIR filter. There is no in between choice. (And of course that would be the wrong conclusion.)



No, but thanks for the reminder. I'm not going to repeat myself so cf. Above.
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Nika Aldrich

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From what I can tell, and based on the fact the fact that Zoesch has said that even electrical, recursive, classic filters of a y(n)=Ax(n)+By(n-1) variety are not actually IIR filters, it seems he is trying to redefine filters and come up with a third variety - not "finite" and not "infinite" but rather "unknown impulse response" filters, such that we just don't know what happens with the impulse once it hits the quantum level.   Then he wants to take all IIR filters (such as transducers, all natural objects with resonance, and electrical filters) and call them this new variety of unknown filters so that he can still be correct that transducers are not IIR filters according to his new definitions.

And according to that, a transducer is indeed "very different" from an IIR filter while at the same time not an FIR filter in that it is actually an IIR filter in its new name.  

From all of the dialogue and all of the discourse this is, I'm afraid, the only conclusion I can draw.  Good try, David, but I believe your post still left just enough wiggle room through which Zoesch can slip out.  

It still seems to me that Zoesch realizes he made a mistake several pages ago and rather than fess up to it and move on and say "thanks for teaching me something - I hadn't looked at it that way.  Wow, there's always time to learn something new!" and gain the respect of the onlookers in the thread for appearing human, he instead continues to dig himself deeper and redirect and wiggle to try to "have been right all along" about this topic.  At any moment now I'm expecting a "yup, I agree, that's exactly what I've been saying" comment.  I'm expecting the same in about a month on the delta-sigma modulator thread elsewhere.

Nika.
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Zoesch

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Ok, Nika... dazzle me, quantum level my ass, show me that the impulse response at all times will generate enough kinetic force to move the speaker or the diaphragm and we'll bury this thread forever, this is not quantum mechanics, this is year 1 physics.

All of a sudden you seem to have rewritten the laws of physics and you seem to imply that the mechanical aspects of the transducer are to be obvied, so please prove it.

BTW y(n)=Ax(n)+Bx(n-1)? I suppose you actually meant y(n)=Ax(n)-Bx(n-1).

I'll deal with the other things in the appropriate places and at the appropriate time.

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Nika Aldrich

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Quote:

y(n)=Ax(n)+Bx(n-1)?


... is a first order low pass FIR filter.

Quote:

 I suppose you actually meant y(n)=Ax(n)-Bx(n-1)


No.  That's a first order high pass FIR filter.

What I meant is what I wrote - y(n)=Ax(n)+By(n-1), which is a first order low pass IIR filter (unless you're renaming it because it isn't actually "infinite" but rather "unknown").

Nika.
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davidc

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Paul Frindle wrote on Wed, 23 June 2004 16:25

Zoesch wrote on Wed, 23 June 2004 08:11


As I don't know what you two are about maybe you want to step down from the spin machine soapbox and display a behavior more fit to the forum's intent and forms and the discussion at hand.



Spin machine soapbox!!

Ok - if I am one of the people respectfully refered to as 'you two' I am more than happy to 'step down', got better things to do anyway. I was honestly only trying to help. Sorry if this constitutes a behaviour which is 'unfit to the forum's intent'.

Please understand respectfully that I absolutely NEVER waste my valuable time peddling dishonest 'spin', nor do I go out of my way to gratuitously upset people Sad

Consider me dismissed - err - gone Smile



Paul,

Please don't go. Some of us really do appreciate your input. It would be a big loss if you were not to contribute to the forum.

Best Regards

David C
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Zoesch

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Nika Aldrich wrote on Thu, 24 June 2004 06:20

Quote:

y(n)=Ax(n)+Bx(n-1)?


... is a first order low pass FIR filter.

Quote:

 I suppose you actually meant y(n)=Ax(n)-Bx(n-1)


No.  That's a first order high pass FIR filter.

What I meant is what I wrote - y(n)=Ax(n)+By(n-1), which is a first order low pass IIR filter (unless you're renaming it because it isn't actually "infinite" but rather "unknown").

Nika.


Fair enough and yes that is correct then.
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George Massenburg

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I'm going to lock this topic until I can decide what to do with it.

George
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