inventor of Hypersonic Sound at TED

Related to our recent discussions on nonlinear response in
acoustics... may be of interest:

http://www.ted.com/index.php/talks/woody_norris_invents_amazing_things.html

-Carl

So that's how that works....

I wish I had more detail on the physics - the distortion in air is an
interesting effect.

Thanks for sharing.

On Fri, Feb 6, 2009 at 10:28 PM, Carl Lumma <carl@...> wrote:

> Related to our recent discussions on nonlinear response in
> acoustics... may be of interest:
>
> http://www.ted.com/index.php/talks/woody_norris_invents_amazing_things.html
>
> -Carl
>
>
>

Very interesting.
I once had an idea for a microphone based on a similar principle.
Make an ultrasonic sound of a fixed pitch and a small distance from this
(like a millimeter or something) place a specific microphone that only picks
up around this ultrasonic frequency (so does not pick up audio range).
Make it very small and the distance between the ultrasonic sine wave and the
ultrasonic microphone is open air.
When you make a sound the soundwaves will travel between the ultrasonic sine
wave (or clicks at regular ultrasonic intervals) emiter and ultrasonic
microphone, causing the ultrasonic sine wave to vary in pitch according to
the pressure of audio sound wave.
The advantage of this could be there's no inertia you get with a normal
microphone diagram and it can be very small and some other advantages.
Never worked it out though and have no idea if it could give better audio
quality.

Marcel

On Sat, Feb 7, 2009 at 5:18 AM, Chris Vaisvil <chrisvaisvil@gmail.com>wrote:

> So that's how that works....
>
> I wish I had more detail on the physics - the distortion in air is an
> interesting effect.
>
> Thanks for sharing.
>
>
> On Fri, Feb 6, 2009 at 10:28 PM, Carl Lumma <carl@lumma.org> wrote:
>
>> Related to our recent discussions on nonlinear response in
>> acoustics... may be of interest:
>>
>>
>> http://www.ted.com/index.php/talks/woody_norris_invents_amazing_things.html
>>
>> -Carl
>>
>>
>
>

Ok, I finally think I get it.
   You know how a 500hz and 600hz tone played together beats at 100hz?
    Well...so do a 300500 and 300600 hz tone...only your ear can't pick up any tone EXCEPT the beating itself.
    This sounds great for headphone-type applications where you need to focus sound in a particular location (as higher sound, of course, is more directional and ultra-sound is "perfectly directional").

   Ok, cool...but what about the PHYSICAL element of sounds...meaning virtually anything 350hz or under which you can FEEL shake your bones as well as hear?
   My guess is you simply can't feel such sounds in such a system.  Thus, an ideal "sound system" would use ultra-sound for 350hz+ sounds and a real sub-woofer for 350hz-
sounds.

  Physics and signal processing buffs, please correct me if I'm wrong, but I think this invention, while very cool, isn't going to be a substitute for a the good old sub-woofer.

  Another side question, can "beating" itself produce hearing loss (or can you crank a 300500 and 310500hz signal with a massively loud (say 120db) peak and still suffer no hearing loss)?   If you can get away with that...wow, that would be a great thing for those with hearing loss and/or to help prevent hearing loss.

-Michael

--- On Fri, 2/6/09, Carl Lumma <carl@...> wrote:

From: Carl Lumma <carl@...>
Subject: [tuning] inventor of Hypersonic Sound at TED
To: tuning@yahoogroups.com
Date: Friday, February 6, 2009, 7:28 PM

Related to our recent discussions on nonlinear response in

acoustics... may be of interest:

http://www.ted. com/index. php/talks/ woody_norris_ invents_amazing_ things.html

-Carl

Hi Michael,

Ok, I finally think I get it.
> You know how a 500hz and 600hz tone played together beats at 100hz?
> Well...so do a 300500 and 300600 hz tone...only your ear can't pick up
> any tone EXCEPT the beating itself.
>

No this isn't how it works.
He stated it's due to the nonlinearity of the air at high volume.
So it's due to some kind of distortion and there's an actual sound
generated, not in the ear but in the air he sais.
The pressure area of one wave slowing down / speading up another wave.
Sound slows down / speeds up due to air pressure and density. In normal
circumstances these things balance eachother out.
So if a high or low pressure area (meteorological) is in your area sound
doesn't speed up because it's balanced out because of lower/higher density.
But in a sound pressure wave this does not happen in thesame way.
Anyhow my guess is it's based on something like this.

Marcel

I also mentioned it on Jan 8th:
/tuning/topicId_74827.html#74829
and 9th:
/tuning/topicId_79751.html#79831

-Carl

--- In tuning@yahoogroups.com, Chris Vaisvil <chrisvaisvil@...> wrote:
>
> So that's how that works....
>
> I wish I had more detail on the physics - the distortion in
> air is an interesting effect.
>
> Thanks for sharing.
>
> On Fri, Feb 6, 2009 at 10:28 PM, Carl Lumma <carl@...> wrote:
>
> > Related to our recent discussions on nonlinear response in
> > acoustics... may be of interest:
> >
> > http://www.ted.com/index.php/talks
> > /woody_norris_invents_amazing_things.html
> >
> > -Carl
>