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Old 13th July 2004, 02:06 AM   #1
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Default Might be interested in this distortion thread

You folks might be interested in this discussion of distortion on the SS board. I was postulating that we may be looking at the topic of distortion in the wrong way and that may explain why we have trouble correlating measurements to sound quality.

Are we looking at it wrong
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Old 13th July 2004, 04:44 AM   #2
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Yeah, but we don't have to worry about it because we've got the "pleasing distortion" already, long as we keep THD < 5% (easily audible crunchiness) we don't care.

Tim
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Old 13th July 2004, 09:20 AM   #3
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Default Distortion? We luv it!

Some of us do read the "sand" threads as well
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Old 13th July 2004, 11:06 PM   #4
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Hi,

Quote:
I was postulating that we may be looking at the topic of distortion in the wrong way and that may explain why we have trouble correlating measurements to sound quality.
Personally I tend to agree with your idea....
Nothing new either as many people who's work I've been admiring have been saying exactly that for many years already.

Problem is, how do you develop a measuring device that does correlate in a better way with what we're hearing?

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Old 13th July 2004, 11:50 PM   #5
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Default Lots of study.

I think the answer is a lot of experimentation.

It would take a great deal of subjective testing to get a handle on what sonically intrusive distortion looks like. There would probably be many different patterns that fit this catagory. Then the big task would be to correlate measurable parameters to these shapes. Things to investigate would be areas between the input and output curves, angles of deviation, d/dt of the input and output signals etc. At this point I have no idea what the correlations might be but I suspect that it will be a differential equation of some sort that gives us the answers since the ear is "measuring" pressure changes. Maybe dI(t)/dt - dO(t)/dt (where I(t) = input signal and O(t) = output signal would be instructive.

Of course I may be full of hooey and maybe there is no mathimatical representation that correlates to ugly sound at all. I could believe that mathematics might not be able to model everything in creation but my guess is that it is possible to get close if one is clever enough. Alas I am probably not.
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Old 13th July 2004, 11:57 PM   #6
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Hi,

Quote:
I think the answer is a lot of experimentation.
I think you're closer to home with this one than you actually realise....

Cheers,
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Old 14th July 2004, 01:36 AM   #7
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Default Re: Lots of study.

Quote:
Originally posted by mashaffer
Of course I may be full of hooey and maybe there is no mathimatical representation that correlates to ugly sound at all. I could believe that mathematics might not be able to model everything in creation but my guess is that it is possible to get close if one is clever enough. Alas I am probably not.
http://www.gedlee.com/distortion_perception.htm

!!!!!!!!!!

Look at the second presentation on this page!

I've posted this in several of the distortion threads, but no one is commenting on it. Maybe no one is looking at it?

It may not be *the* answer, but there is a mathematical figure of merit given that seems to correlate pretty well with subjective perception.

Go look!
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Old 14th July 2004, 02:28 AM   #8
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I tried looking at the ppt yesterday but I couldn't get it to load. The web page did make it look interesting though.
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Old 14th July 2004, 08:28 AM   #9
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Quote:
Originally posted by mashaffer
I tried looking at the ppt yesterday but I couldn't get it to load. The web page did make it look interesting though.
Try this:

http://members.iinet.net.au/~jmai/di...les/frame.html

I saved the presentation as html and put in my web-space. Maybe you can see it now, though you may need to use IE.
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Old 14th July 2004, 01:08 PM   #10
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Thanks Jeff. That worked.

That is very interesting stuff. I confess that I am not familiar with th V series stuff but the overall idea is interesting. They are of course still working with frequency domain analysis which is different than what I am proposing. The correlation results are impressive though. It would be interesting to see what the distortions looked like in the time domain.
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