Re: [LAD] Audio Levitation

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To: Fons Adriaensen <fons@...>
Cc: The Linux Audio Developers' Mailing List <linux-audio-dev@...>
Date: Friday, January 3, 2014 - 10:03 pm

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On Fri, Jan 3, 2014 at 10:00 AM, Fons Adriaensen wrote:

> On Fri, Jan 03, 2014 at 11:03:59PM +1100, Patrick Shirkey wrote:

These are nice back-of-the-envelope calculations, but I think there's a
little more explanation needed (not sure, but bear with me).

Why do we see this technique applied with high frequencies? At the node
locations, there is the highest peak spatial derivative of the pressure
while at the same time, the volume velocity of air goes to 0.

Vice-versa at the anti-nodes.

It may not require so much power as the frequency becomes very high
(although the physical scale between nodes also diminishes making it
impractical for "large" objects), if the variable of interest is not the
pressure difference itself, but the magnitude of its spatial derivative.

Other thoughts: the apparent acoustic power only needs to be large in the
region of standing waves. You may not be exposed to dangerous SPL's when
you get far enough away from the focus.

I have been contemplating some designs on acoustic levitation, but I
haven't risen to the task of figuring how much power is involved. This
discussion is helpful to me (and fun!)

Chuck

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On Fri, Jan 3, 2014 at 10:00 AM, Fons Adriaensen =
<fons@linuxaudi=
o.org
> wrote:
On Fri, Jan 03, 2014 at 11=
:03:59PM +1100, Patrick Shirkey wrote:

> Theoretically, how big can this scale?

layer_embedded&v=3DodJxJRAxdFU

Not so much before it becomes really dangerous and unpractical.

What supports those objects is the pressure differences generated
by the standing waves. Now 120 dB SPL is 20 Pa, or 2 kg / m^2, or
2 milligrams per square millimeter. Which suggests they are already
using more than 120 dB SPL.These are nice back-of-the-envelope calculations, but I think there=
's a little more explanation needed (not sure, but bear with me).
Why do we see this technique applied w=
ith high frequencies?=A0 At the node locations, there is the highest peak s=
patial derivative of the pressure while at the same time, the volume veloci=
ty of air goes to 0.
Vice-versa at the anti-nodes.It may not req=
uire so much power as the frequency becomes very high (although the physica=
l scale between nodes also diminishes making it impractical for "large=
" objects),=A0=A0=A0 if the variable of interest is not the pressure d=
ifference itself, but the magnitude of its spatial derivative.
Other thoughts:=A0 the apparent acoust=
ic power only needs to be large in the region of standing waves.=A0 You may=
not be exposed to dangerous SPL's when you get far enough away from th=
e focus.
I hav=
e been contemplating some designs on acoustic levitation, but I haven't=
risen to the task of figuring how much power is involved.=A0 This discussi=
on is helpful to me (and fun!)
Chuck

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Messages in current thread:
[LAD] Audio Levitation, Patrick Shirkey, (Fri Jan 3, 12:03 pm)
Re: [LAD] Audio Levitation, Fons Adriaensen, (Fri Jan 3, 4:00 pm)
Re: [LAD] Audio Levitation, Charles Z Henry, (Fri Jan 3, 10:03 pm)
Re: [LAD] Audio Levitation, Charles Z Henry, (Fri Jan 3, 11:01 pm)
Re: [LAD] Audio Levitation, Fons Adriaensen, (Sat Jan 4, 12:19 am)
Re: [LAD] Audio Levitation, Patrick Shirkey, (Sat Jan 4, 10:24 am)
Re: [LAD] Audio Levitation, Fons Adriaensen, (Sat Jan 4, 1:39 pm)
Re: [LAD] Audio Levitation, Dominique Michel, (Sat Jan 4, 4:56 pm)
Re: [LAD] Audio Levitation, Fons Adriaensen, (Sat Jan 4, 8:19 pm)
Re: [LAD] Audio Levitation, Patrick Shirkey, (Sun Jan 5, 2:28 pm)
Re: [LAD] Audio Levitation, R. Mattes, (Sun Jan 5, 3:33 pm)
Re: [LAD] Audio Levitation, Patrick Shirkey, (Sun Jan 5, 5:11 pm)
Re: [LAD] Audio Levitation, Fons Adriaensen, (Sun Jan 5, 5:48 pm)
Re: [LAD] Audio Levitation, Gordon JC Pearce, (Sun Jan 5, 7:52 pm)
Re: [LAD] Audio Levitation, R. Mattes, (Sun Jan 5, 8:44 pm)
Re: [LAD] Audio Levitation, Dominique Michel, (Sat Jan 4, 11:08 pm)
Re: [LAD] Audio Levitation, Ralf Mardorf, (Sun Jan 5, 12:51 pm)
Re: [LAD] Audio Levitation, Dominique Michel, (Sun Jan 5, 7:21 pm)
Re: [LAD] Audio Levitation, Ralf Mardorf, (Sun Jan 5, 10:39 pm)
Re: [LAD] Audio Levitation, Ralf Mardorf, (Sun Jan 5, 10:44 pm)
Re: [LAD] Audio Levitation, Fons Adriaensen, (Sun Jan 5, 10:31 pm)
Re: [LAD] Audio Levitation, Ralf Mardorf, (Sun Jan 5, 11:38 pm)
Re: [LAD] Audio Levitation, Dominique Michel, (Mon Jan 6, 11:11 pm)
Re: [LAD] Audio Levitation, Fons Adriaensen, (Tue Jan 7, 12:22 am)
Re: [LAD] Audio Levitation, Ralf Mardorf, (Tue Jan 7, 4:03 pm)
Re: [LAD] Audio Levitation, Dominique Michel, (Thu Jan 9, 1:05 pm)
Re: [LAD] Audio Levitation, Paul Davis, (Tue Jan 7, 1:11 am)
Re: [LAD] Audio Levitation, Dominique Michel, (Tue Jan 7, 6:22 am)
Re: [LAD] Audio Levitation, Paul Davis, (Tue Jan 7, 4:10 pm)
Re: [LAD] Audio Levitation, Patrick Shirkey, (Tue Jan 7, 4:27 am)
Re: [LAD] Audio Levitation, Arnold Krille, (Sun Jan 5, 6:52 pm)
Re: [LAD] Audio Levitation, Ralf Mardorf, (Sun Jan 5, 10:15 pm)
Re: [LAD] Audio Levitation, John Rigg, (Mon Jan 6, 8:39 am)
Re: [LAD] Audio Levitation, Dominique Michel, (Sat Jan 4, 3:37 pm)
Re: [LAD] Audio Levitation, Patrick Shirkey, (Sat Jan 4, 3:49 pm)
Re: [LAD] Audio Levitation, Patrick Shirkey, (Sat Jan 4, 3:23 pm)
Re: [LAD] Audio Levitation, Arnold Krille, (Fri Jan 3, 7:02 pm)
Re: [LAD] Audio Levitation, Fons Adriaensen, (Fri Jan 3, 8:33 pm)
Re: [LAD] Audio Levitation, Ralf Mardorf, (Fri Jan 3, 7:21 pm)
Re: [LAD] Audio Levitation, Ralf Mardorf, (Fri Jan 3, 8:07 pm)