Another off-topic -- what I've just heard on the radio

Hi all.

Though this has completely nothing to do with tunings, I was simply amazed
when I heard the news. How can someone make an audible sound out of mixed
ultrasonic frequencies? The only method I can think of right now is by using
difference tones. But if this is the case, anyway, I believe there must be
some limitations as to what can be the lowest frequency this method can
produce with a reasonable loudness. I was not able to find anything more
about this than a single webpage: www.holosonics.com/technology.html

Any suggestions?

Petr

Petr Pa��zek wrote:
> Hi all.
>
> Though this has completely nothing to do with tunings, I was simply amazed
> when I heard the news. How can someone make an audible sound out of mixed
> ultrasonic frequencies? The only method I can think of right now is by using
> difference tones. But if this is the case, anyway, I believe there must be
> some limitations as to what can be the lowest frequency this method can
> produce with a reasonable loudness. I was not able to find anything more
> about this than a single webpage: www.holosonics.com/technology.html
>
> Any suggestions?
>
> Petr
>
>
>
>
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Well ... there are references in the advert ... presumably there are
peer-reviewed articles one can look up on the subject.

> Well ... there are references in the advert ... presumably there are
> peer-reviewed articles one can look up on the subject.

It uses very high dB to make air behave nonlinearly. A modulated
signal is played, and the nonlinear reaction of the air
demodulates it. See:

http://en.wikipedia.org/wiki/Sound_from_ultrasound

-Carl

Nice to see your presence Ed after a period of time......
i must say there is something scary about anything that is
"peer-reviewed". conjures visions of some type of political (un)think
tank?!?!*&^%$
just for fun<<<<<<<<
--- In tuning@yahoogroups.com, "M. Edward (Ed) Borasky" <znmeb@...> wrote:

>
> Well ... there are references in the advert ... presumably there are
> peer-reviewed articles one can look up on the subject.
>

how can sound behave linearly since we are talking about a 3d state.
Lines do not exist, they are imaginary.
It is simple A-b =C and C is in the hearing range and A and b are not.

--- In tuning@yahoogroups.com, "Carl Lumma" <carl@...> wrote:
>
> > Well ... there are references in the advert ... presumably there are
> > peer-reviewed articles one can look up on the subject.
>
> It uses very high dB to make air behave nonlinearly. A modulated
> signal is played, and the nonlinear reaction of the air
> demodulates it. See:
>
> http://en.wikipedia.org/wiki/Sound_from_ultrasound
>
> -Carl
>

Kraig wrote:

> It is simple A-b =C and C is in the hearing range and A and b are not.

If it was that simple, then there would be no need to "pre-compensate" for the harmonic distortion. And it took quite some time till people knew how to do that. The Wikipedia article explains it nicely, I think.

Petr

These aren't difference tones, if that's what you mean. Many
mechanical systems behave nonlinearly if you overdrive them,
and air is no exception.

-Carl

--- In tuning@yahoogroups.com, "banaphshu" <kraiggrady@...> wrote:
> how can sound behave linearly since we are talking about a 3d state.
> Lines do not exist, they are imaginary.
> It is simple A-b =C and C is in the hearing range and A and b
> are not.
>
> --- In tuning@yahoogroups.com, "Carl Lumma" <carl@> wrote:
> >
> > > Well ... there are references in the advert ... presumably
> > > there are peer-reviewed articles one can look up on the
> > > subject.
> >
> > It uses very high dB to make air behave nonlinearly. A modulated
> > signal is played, and the nonlinear reaction of the air
> > demodulates it. See:
> >
> > http://en.wikipedia.org/wiki/Sound_from_ultrasound
> >
> > -Carl
> >
>

banaphshu wrote:
> how can sound behave linearly since we are talking about a 3d state.
> Lines do not exist, they are imaginary.
> It is simple A-b =C and C is in the hearing range and A and b are not.

"Linear" in this sense isn't referring to the direction of motion, but the physical properties of the air when two waves are combined. Non-linear distortion can add new frequencies which aren't in either of the original waves.

how is this controlled?

--- In tuning@yahoogroups.com, Herman Miller <hmiller@...> wrote:
>
> banaphshu wrote:
> > how can sound behave linearly since we are talking about a 3d state.
> > Lines do not exist, they are imaginary.
> > It is simple A-b =C and C is in the hearing range and A and b are
not.
>
> "Linear" in this sense isn't referring to the direction of motion, but
> the physical properties of the air when two waves are combined.
> Non-linear distortion can add new frequencies which aren't in either of
> the original waves.
>

--- In tuning@yahoogroups.com, "banaphshu" <kraiggrady@...> wrote:
>
> how is this controlled?

With a computer. :)

-Carl

How else would you propose that academic articles or studies get
refereed? By random members of the public? By the government? By an
all-powerful editor?

Then again, there are people who think that the whole of science is
scary and sinister.

~~~T~~~

--- In tuning@yahoogroups.com, "banaphshu" <kraiggrady@...> wrote:
>
> Nice to see your presence Ed after a period of time......
> i must say there is something scary about anything that is
> "peer-reviewed". conjures visions of some type of political (un)think
> tank?!?!*&^%$
> just for fun<<<<<<<<
> --- In tuning@yahoogroups.com, "M. Edward (Ed) Borasky" <znmeb@> wrote:
>
> >
> > Well ... there are references in the advert ... presumably there are
> > peer-reviewed articles one can look up on the subject.
> >

Like all Political institutions, It is capable of corruption.
i could quote examples but if you deal with such things you know of
what i speak. It is nothing more than a way for promotions and
positions of power.
without it no one would write them.
Up till now none of the magizine on Microtonality were ever "peered
reviewed".
Those publications that are peered reviewed , when they speak on the
subject are 50 years behind the times.

--- In tuning@yahoogroups.com, "Tom Dent" <stringph@...> wrote:
>
>
> How else would you propose that academic articles or studies get
> refereed? By random members of the public? By the government? By an
> all-powerful editor?
>
> Then again, there are people who think that the whole of science is
> scary and sinister.
>

I sent this earlier t oMetatuning , but a quote in part from Einstien
on economics i am sure he would apply even more rigorously to music.

"Let us first consider the question from the point of view of
scientific knowledge. It might appear that there are no essential
methodological differences between astronomy and economics: scientists
in both fields attempt to discover laws of general acceptability for a
circumscribed group of phenomena in order to make the interconnection
of these phenomena as clearly understandable as possible. But in
reality such methodological differences do exist. The discovery of
general laws in the field of economics is made difficult by the
circumstance that observed economic phenomena are often affected by
many factors which are very hard to evaluate separately.

--- In tuning@yahoogroups.com, "Tom Dent"
>
> Then again, there are people who think that the whole of science is
> scary and sinister.