Digital BW, The Print

It is considered conventional wisdom that the ear cannot hear frequencies
above and below a certain point, but that the existence of sound in those
frequencies has an audible effect on what we can. Two examples are called
intermodulation and harmonics.

Modulation can be used by piano tuners, they play two notes simultaneously,
and since the notes are tuned so closely (but not perfectly) they modulate
against each other, and by counting the modulations an experienced tuner can
tell exactly how far to adjust the string.

Two different notes widely separated will produce sum and difference
frequencies, and these can be even order or odd order harmonics.  People who
use old tube amplifiers, particularly electric guitar players, prize the
tube sound because it is primarily even order, which is considered pleasing
to the ear (within reason) as opposed to odd harmonics.

When cds first came out, a mental institution noticed that digital music did
not relax the patients anymore and they had to restore an all analog system.
(this was reported in the Syd-Aud-Con journal which is distributed to audio
and electro-acoustic engineers.)

Does anyone know what optical manifestations of this phenomena are?  there
must be a reason why Leitz lenses cost so much!

tom Robinson

> I liken this debate to the one that went on in the audio world some
> years ago. Studies showed that the human ear is not capable of hearing
> differentials more than 8 bits. They also showed the human ear is not
> capable of hearing frequencies below X and above Y ( forgive me I don't
> remember X and Y and their values aren't important).
> 
> This experiment was repeated many times with the same results. However,
> if you filter music so that no energy from frequencies below X and above
> Y appear and run a test to determine if people can hear the difference,
> they sure can. If you run test todetermine if people can tell the
> difference between complex music sampled at 8 bits vs. 12 bits, they
> sure can. In fact music sampled at 8 bits and limited to frequencies
> above X and below Y sounds pretty "hollow." It gets to the fidelity of
> the reporduction.
> 
> I think the same is probably as true for the eye as is for the ear.
> While humans are not suppose to be able to see beyoun 300 dpi, I would
> expect in a complex image they sure can tell the difference if it were
> printed at 300 or 360 or maybe even 720.
> 
> I always down sample to 720 and print from there.

>It is considered conventional wisdom that the ear cannot hear frequencies
>above and below a certain point, but that the existence of sound in those
>frequencies has an audible effect on what we can. Two examples are called
>intermodulation and harmonics.

Harmonics is a different thing, and has nothing to do with the ability for
signals beyond your hearing range to "effect" the signals within your
hearing range.  Harmonics are merely integral multiples of a given
frequency.  Intermodulation distortion is probably a better way to
characterize it.

>When cds first came out, a mental institution noticed that
> digital music did
>not relax the patients anymore and they had to restore an all
> analog system.
>(this was reported in the Syd-Aud-Con journal which is
> distributed to audio
>and electro-acoustic engineers.)

I don't believe any conclusion can be drawn by that.  When CDs first came
out, they did not use oversampling to smooth out the output signal, and that
is why they sounded "digital", and in fact, sounded annoying to people who
weren't mental patients as well.  This issue has long been attended to by
the use of oversampling and first order filters.  Prior to using
oversampling, third order filters were primarily used, and these induced
phase shift in the output, simply because different frequencies take
different times to travel through the filter.  The result is typically
annoying to human hearing.  Not so with first order filters.

Austin

At 12:09 AM 5/25/03 -0700, you wrote:
>It is considered conventional wisdom that the ear cannot hear frequencies
>above and below a certain point, but that the existence of sound in those
>frequencies has an audible effect on what we can. Two examples are called
>intermodulation and harmonics.
>
>Modulation can be used by piano tuners, they play two notes simultaneously,
>and since the notes are tuned so closely (but not perfectly) they modulate
>against each other, and by counting the modulations an experienced tuner can
>tell exactly how far to adjust the string.
>
>Two different notes widely separated will produce sum and difference
>frequencies, and these can be even order or odd order harmonics.  People who
>use old tube amplifiers, particularly electric guitar players, prize the
>tube sound because it is primarily even order, which is considered pleasing
>to the ear (within reason) as opposed to odd harmonics.
>
>When cds first came out, a mental institution noticed that digital music did
>not relax the patients anymore and they had to restore an all analog system.
>(this was reported in the Syd-Aud-Con journal which is distributed to audio
>and electro-acoustic engineers.)
>
>Does anyone know what optical manifestations of this phenomena are?  there
>must be a reason why Leitz lenses cost so much!
>
>tom Robinson
>
> > I liken this debate to the one that went on in the audio world some
> > years ago. Studies showed that the human ear is not capable of hearing
> > differentials more than 8 bits. They also showed the human ear is not
> > capable of hearing frequencies below X and above Y ( forgive me I don't
> > remember X and Y and their values aren't important).
> >
> > This experiment was repeated many times with the same results. However,
> > if you filter music so that no energy from frequencies below X and above
> > Y appear and run a test to determine if people can hear the difference,
> > they sure can. If you run test todetermine if people can tell the
> > difference between complex music sampled at 8 bits vs. 12 bits, they
> > sure can. In fact music sampled at 8 bits and limited to frequencies
> > above X and below Y sounds pretty "hollow." It gets to the fidelity of
> > the reporduction.
> >
> > I think the same is probably as true for the eye as is for the ear.
> > While humans are not suppose to be able to see beyoun 300 dpi, I would
> > expect in a complex image they sure can tell the difference if it were
> > printed at 300 or 360 or maybe even 720.
> >
> > I always down sample to 720 and print from there.

  When I listen to Kenny G. here at The Home I get very irritated.  Now I 
know why.   I'll probably get slammed on this, but wasn't the "beat 
frequency" thing part of the explanation for metamerism?  Sort of?

AZ


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