Sound Past the Diffraction Limit

[swiderman63]

Hi,

 

I'm working on this science experiment in school, I don't really wish to go into details, but I would like to use this experiment I found online in this article:

 

http://phys.org/news/2011-07-coke-cans-focus-diffraction-limit.html

 

I have tried to mimic as much as I can from what I found out on the small article but I'm having trouble recording the resonating tone of a can. So far I have used a simple phone microphone but it captures the overlaying tone and the resonating tone is faded in the background. I'm wondering if anyone would have any ideas of how to get a finer recording of the resonating tone. Unfortunately, the article I discovered the experiment in is as far as I been able to go as in finding any more information. It would be a great deal of help if someone had a solution! Thank you!

[Acme]

Have you tried playing a reverse recording as described in the article?

Also, there are links at the end of the article where more info is given.

http://physicsworld.com/cws/article/news/2011/jul/11/how-to-make-a-superlens-from-a-few-cans-of-cola

http://www.nature.com/news/2011/110708/full/news.2011.406.html

The second link has more links given as references.

References
1.Lerosey, G., de Rosny, J., Tourin, A. and Fink, M. Science 315, 1120-1122 (2007). | Article | ISI | ChemPort |
2.Lemoult, F., Lerosey, G., de Rosny, J. and Fink, M. Phys. Rev. Lett. 104, 203901 (2010). | Article | ChemPort |
3.Lemoult, F., Fink, M. and Lerosey, G. Phys. Rev. Lett. (in the press)
4.Sukhovich, A. et al. Phys. Rev. Lett. 102, 154301 (2009). | Article | ChemPort |

You might aslo try contacting the original researches directly. It all sounds pretty kewl. Good luck!

[Enthalpy]

Reverse sound, as well as sub-wavelength focussing, demand very accurate sounds. Microphones use to be accurate, but your may need to first identify the response of your loudspeakers. Of course, you can't move the loudspeakers.

 

Or even, I'd use a loudspeaker as the microphone, then swap the functions but keep all transducers as they are and where they are. Time-reversing the signal would make more sense then, while keeping the whole transmission chain. EVen, I'd keep the (very small, not 4 nor 8 ohm) load impedance while using the loudspeaker as a microphone.

 

I'm very surprised about resonances lasting for 1s. That would demand very low flow loss through the opening, possibly made long and smooth. Even a beer bottle resonates shorter.

 

The picture is unclear about the distance of the microphone - it's probably no that far from the array. "Far" would then refer to the sound source, not to the array.

 

The Physorg paper doesn't tell neither if all cans resonate at the same frequency, or are rather tuned individually.