[sdiy] Harmonic bandwidth

[Scott Gravenhorst]

"Ben Lincoln" <blincoln at eventualdecline.com> wrote:
>On Thu, January 10, 2008 6:08 am, Scott Gravenhorst said:
>
>> However, within the domain of any individual's hearing, according to
>> theory, we should
>> not be able to hear the difference between two signals with the same
>> harmonic
>> components when harmonic phase relationships are constant, but different
>> between two
>> signals.
>
>Scott, have you read the article that Ian posted a link to yet
>(http://www.silcom.com/~aludwig/Phase_audibility.htm)? 

Yes, and it just confused the issue for me.  I have many questions.  I'm not convinced
that this is not a digital artifact.  In a paragraph near the end, the method to
produce the piano notes was described - the signal was sampled, then FFT, phase
randomized and then IFFT to reproduce a phase changed signal.  All of that had to be
done digitally.  Artifacts would affect this process.  I also have a problem with using
such a complex signal as a piano note.  If I'm not mistaken, there are anharmonic
signals present in a vibrating string so I'm not sure how useful this can be with
respect to an experiment that would demonstrate this.  A better experiment (IMO) would
be to use a signal which has true harmonics, not overtones that are anharmonic - but
we've essentially done that with our various digital approaches.  An analog approach
would eliminate any possibility of digital artifacts as long as we listen to the actual
signals and not recordings of them.

I ain't sayin' it is, and I ain't sayin' it ain't.

>Apparently it's
>been known for quite awhile that the older theory is not 100% correct, and
>the article makes an argument for it being even less correct than in the
>papers that are cited.
>
>I was also a little surprised to find that the research which was the
>basis for the "harmonic phases are not distinguishable" statement was from
>the middle of the 19th century. While I don't think that means it should
>be entirely discounted, it seems to me like the equipment in 1843 would
>not be nearly accurate enough to use as a basis for that kind of broad
>statement without duplicating the results using modern equipment.

It appears to me that more and better experiments are necessary.

-- ScottG

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-- Scott Gravenhorst
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