ISEN-ASTC-L is a service of the Association of Science-Technology Centers
Incorporated, a worldwide network of science museums and related institutions.
*****************************************************************************

In watching the demos on youtube, I realized that there are two  
different things that you are showing that shouldn't be confused.   
When you are using a pure sine tone, you are showing standing waves  
and the resulting different pressure in different areas, not unlike  
the classic explo exhibition done with styrofoam bits in a tube.  When  
you are showing a full band playing rock or any music into the tubes,  
you are still seeing different pressure at different points of the  
tube, bt I guess that the areas of greater pressure indicate  
frequencies in the recording that have greater amplitude at any given  
moment.  It is much easier to use the pure sine tones for teaching the  
physics of waves, but arguably more fun to use the tube as kind of  
flame "light organ," if you remember those.


Eric Siegel
esiegel at nyscience dot org



On Mar 12, 2009, at 9:37 AM, Willam Katzman wrote:

> ISEN-ASTC-L is a service of the Association of Science-Technology  
> Centers
> Incorporated, a worldwide network of science museums and related  
> institutions.
> *****************************************************************************
>
> Holly,
>
> This may not answer your question completely, but...
>
> 1) Definitely use metal for the tube.  Realize it will get hot.
> 2) If you really want to find out about creating standing wave  
> patterns,
> then http://www.instructables.com/id/S9QLGKXF5R8MTGP/ is a nice  
> place to
> start, but it's not 100% correct.  The fact that you are feeding a  
> gas into
> the tube and the gas itself is moving changes the equations a bit.   
> Rather
> than adding flow gauges, etc. to do exact equations I would just  
> start with
> these equations and modify the frequency until you get a standing  
> wave.
> 3) Anything can be your sound source - as long as you use a speaker  
> to get
> the sound source into the tube.  Some versions don't us e a speaker  
> at all,
> but rely on someone yelling into a latex diaphragm to create the sound
> ripples - I've heard that works, but it's not convenient, you can't  
> control
> the sound source and the latex diaphragms are problematic.  With  
> that being
> said, it is cool that you don't need electronics to accomplish this!
> 4) I recommend make it relatively easy to change out the speaker.   
> You'll
> probably have to do this at some point.  Most of us don't make it  
> easy to
> change it out because that takes more time and better engineering,  
> but it
> helps long-term.
> 5) For safety, I've always thought that we should build a Rubens  
> tube with a
> thermocouple that would shut off the gas supply if enough heat wasn't
> present (like some gas fireplaces and heaters), but I don't know  
> anybody who
> has actually done it.
> 6) Amplitude matters!  If you have a sound source that changes  
> amplitude
> dramatically you can blow out the flame jets you are using (this is
> particularly true if you are using a limited gas supply with low  
> pressure).
> 7) All the obvious rules apply - don't get things near the tube,  
> have fire
> extinguishers on hand, make friends with the fire dept. so they  
> don't want
> to close you down, don't use materials that are very temperature  
> sensitive.
> 8) Unless you have some way of cooling down the Rubens tube be  
> carfeull
> about running if for a long time because it will heat up and that  
> can cause
> all sorts of problems (from slowly burning the stand it's on to  
> causing
> problems with your speaker system (unless you've really designed the  
> whole
> apparatus to operate in a high heat environment).
> 9) Now think about why you are doing this...make sure the demo  
> fulfills your
> need.  Next experiment with songs and sounds so that the sounds help  
> your
> demo fulfill its purpose.
> 10) Ten is here because we tend to live in a base 10 oriented  
> society so I
> felt like I needed to round this out with a 10th point...  ;)
>
> -William
>
> William Katzman
> Director of Exhibits
> Catawba Science Center
> (828) 322-8169 x307
> "The Magic of Learning, the Science of Fun"
>
> Now Renting Out
> Dinosaurs! (3,000 sq. ft. only $25k)
> Body Carnival (2250 sq. ft. only $15k)
> Maze Mania (3,000 sq. ft. only $7.5k)
> http://www.catawbascience.org/
>
> ***********************************************************************
> For information about the Association of Science-Technology Centers  
> and the Informal Science Education Network please visit www.astc.org.
>
> Check out the latest case studies and reviews on ExhibitFiles at www.exhibitfiles.org 
> .
>
> The ISEN-ASTC-L email list is powered by LISTSERVR software from L- 
> Soft. To learn more, visit
> http://www.lsoft.com/LISTSERV-powered.html.
>
> To remove your e-mail address from the ISEN-ASTC-L list, send the
> message  SIGNOFF ISEN-ASTC-L in the BODY of a message to
> [log in to unmask]

***********************************************************************
For information about the Association of Science-Technology Centers and the Informal Science Education Network please visit www.astc.org.

Check out the latest case studies and reviews on ExhibitFiles at www.exhibitfiles.org.

The ISEN-ASTC-L email list is powered by LISTSERVR software from L-Soft. To learn more, visit
http://www.lsoft.com/LISTSERV-powered.html.

To remove your e-mail address from the ISEN-ASTC-L list, send the
message  SIGNOFF ISEN-ASTC-L in the BODY of a message to
[log in to unmask]