[kats]

Originally Posted by norman_nomad

Where are the studies supporting such a claim? There seem to be many more in the 20hz - 20khz camp.

Always open to new ideas through good science however if you can provide it....

Hey fellas, back again. Nope can't prove it. I can't prove that we know everything either. But I'll leave you with an interesting anecdote.

You all have heard the Geoff Emerick/Rupert Neve story?

Here's part of it:

Fletcher: There has been some measure of debate about bandwidth including frequencies above 20kHz, can we hear them, do they make a difference, etc.

Rupert: OK, Fletch, pin your ears back...back in 1977, just after I had sold the company, George Martin called me to say that Air Studios had taken delivery of a Neve Console which did not seem to be giving satisfaction to Geoff Emmerick. In fact, he said that Geoff is unhappy.... engineers from the company, bear in mind that at this point I was not primarily involved, had visited the studio and reported that nothing was wrong. They said that the customer is mad and that the problem will go away if we ignore it long enough.
Well I visited the studio and after careful listening with Geoff, I agreed with him that three panels on this 48 panel console sounded slightly different. We discovered that there was a 3 dB peak at 54kHz Geoff's golden ears had perceived that there was a difference. We found that 3 transformers had been incorrectly wired and it was a matter of minutes to correct this. After which Geoff was happy. And I mean that he relaxed and there was a big smile on his face.
As you can imagine a lot of theories were put forward, but even today I couldn't tell you how an experienced listener can perceive frequencies of the normal range of hearing.

Here's something else to ponder:

Could you hear the difference between a sine wave at 10k (not too high, eh?) and a triangle wave at 10k? I can. Most people can.

Since this is a single wave, no interaction (hetereodyning) is present.

However, theoretically, the one component that makes a sine into a triangle is a 30k harmonic that we "should not be able to hear". If you filter out the harmonics over a 100Hz wave, you would hear just the fundamental (as your ear structure SHOULD filter out things over 20k). - Brian Kehew

But back to Emerick, Eric Bridenbaker over at PSW posted a neat trick a few years ago as a possible answer to the Emerick/Neve dilemma where he was pumping a 56k sine wave through his speakers which produced, well nothing audible. Then he blended a 57k sine wave in and:

the "beat" created between these two ultrasonic tones is equal to 1Khz (57K - 56K), which is a frequency right in the middle of the human hearing range and reproducible on pretty much any speaker...There is a mathematical propensity for harmonics to converge about three and a half octaves above the fundamental

Why do I post all this? Just to point out that this is a pretty complicated issue in the real world and we shouldn't hold onto white papers as gospel. Ultimately, as blue1 says, trust your own ears and go with it (and that's where I agree with him 100%).

Oh and for fun, here's some more interesting stuff Eric provided us:

A similar idea was explored in the late 1800's by a rather controversial figure named John W. Keely. He was a contemporary of Tesla and developed a field of research which he termed "Sympathetic Vibratory Physics". Residing somewhere in between physics and metaphysics, his work has generated much debunking, debating, and general interest since.

He proposed a theory for "beat harmonics", which tried to explain how the higher overtones can combine to create audible resonances at the fundamental frequency. As part of the theory, he indicated that recursive harmonics will converge at the twelfth harmonic, which is about three and a half octaves higher than the fundamental. He made some rather bold claims as to the relative intensities of these overtones, nonetheless the concept seems to have some ballast.

http://www.svpvril.com/Fig_11.html<b...his site well.

I've posted a simple math exercise involving recursive harmonics to show that indeed, there should be a convergence at the twelfth
here.

Link

As a kid I always wondered why turning up the treble made it seem like there was more bass... After some basic audio theory, the Fletcher-Munson curves provided an explanation. Perhaps this proposed harmonic interaction is related to the effect.

Cheers,
Eric

20hz-20khz might not explain the whole picture.