Using a speaker to create a vibration table?

February 3, 2012 11:29 AM

How do I create a vibration table using a speaker?

I asked a question about how to recreate an experiment a while back. You can find it here:

http://ask.metafilter.com/202760/How-to-reconstruct-this-cool-looking-experiment

To recreate however, I would need a vibration table, and a laboratory quality vibration table is no cheap thing. Someone suggested that I used a speaker to vibrate a surface. I found this idea to be intriguing, but I'm wondering how to pull it off. I'm not much of a sound guy or an electrician, so assume that I have close to zero knowledge.

First off, do lab vibration tables and speakers produce the same kinds of vibrations? What would I do to increase the frequency or intensity of the vibrations? What would be the best way to set it up to vibrate a container of fluid evenly just below the point at which waves begin to appear on the surface.

Any answers would be greatly appreciated! Thanks!

posted by Peregrin5 to Science & Nature (7 answers total)

Get a tom tom and remove the bottom head.

Get the biggest subwoofer that will fit in the drum.

To vary the frequency, you can connect the speaker to an amp that's receiving a signal from your computer. You can run this sine wave generator program and play around with the frequencies. I believe audiomulch also has an easy sine wave generator.
posted by spikeleemajortomdickandharryconnickjrmints at 11:44 AM on February 3, 2012

Oh snap, there's an app for that.
posted by spikeleemajortomdickandharryconnickjrmints at 11:46 AM on February 3, 2012

I'm not sure this is exactly what you want but Make Magazine ran this article a few months back: http://makeprojects.com/Project/Chladni-Plate/790/1
posted by bondcliff at 11:47 AM on February 3, 2012

There's a thing to turn any solid thing into a speaker. These things have been around since 1960 afaik, basically a transducer without a speaker cone. Attach it to your table and from there you can pump a sine wave "sound" into it to turn your table into a vibrating table at any frequency.

Here is one example, first one I found quickly, I am not recommending this, it is only an example, there are others.

http://www.freedomdriver.net/
posted by caclwmr4 at 12:06 PM on February 3, 2012

Best answer: The main difference between those vibration tables and a speaker is that the tables are capable of producing a much larger amplitude (distance traveled per oscillation). Peak-to-peak displacement on the order of cm or even tens of cm. So the question is what kind of amplitude do you need? Boudaoud and coworkers report their amplitude in terms of a forcing acceleration amplitude gamma_m, and they note that there's a critical acceleration amplitude below which droplets coalesce. This critical acceleration amplitude is g, gravitational acceleration, 9.8 m/s^2.

The acceleration amplitude is basically the largest acceleration the system undergoes during a vibration cycle. I believe the correct formula for it is gamma_m = displacement * (2*pi*frequency)^2. It looks like the work has been done at around 100 - 300 Hz; let's pick a middling frequency of 200 Hz to find that displacement = 9.8 m/s^2 /(2*pi*200 s^-1)^2 = ~ 6 micrometers. I think you can get this out of a speaker!

Someone check my work, please.

Do you have a strobe light?
posted by mr_roboto at 12:33 PM on February 3, 2012

(actually, your problem might be too much acceleration; can you run this below the Faraday threshold without the vibrations being completely damped by your liquid trough?)
posted by mr_roboto at 12:37 PM on February 3, 2012

Response by poster: Thanks for the suggestions guys! I'll let you know if I'm able to come up with something!
posted by Peregrin5 at 11:44 AM on February 5, 2012