Loudspeakers on glass?

April 6, 2005 12:39 AM

Hi all, on Regent St in Central London there are a number of shops that have sound eminating directly (it appears) from the window panes! Upon further investigation, there is a 2-inch black ribbon around the edges which is connected to some wires on the inside -- the ribbon seems to be a kind of 'reverse pressure zone microphone (pzm)... I've tried in vain to find info on such a Cool Thing but haven't been able to find any more information.. there's http://www.remotemedia.co.uk which is a good start... any other information people have would be greatly appreciated!
posted by kiwi.es to Technology (9 answers total)

Best answer: Not the ribbon ones you describe, but these are pretty cheap. (I didn't see a price tag at remotemedia, so posted the link in case you hadn't found a place selling them directly)
posted by -harlequin- at 3:28 AM on April 6, 2005

With flat panel speakers, they use several piezo electric activators and use an algorithm to work out the modes of vibration of the panel.

There's probably a number of piezo bits on the other side of the ribbon.

Have a google for flat panel loudspeakers.
posted by lunkfish at 5:23 AM on April 6, 2005

Are you sure the 2-inch ribbons aren't just part of the security system? The linked page says it's an obsolete form of security (replaced by pressure sensors) and I don't recall noticing the ribbons in store windows so often anymore. If you simply set up a normal speaker somewhere close behind a pane of glass, wouldn't that achieve the same effect?
posted by nobody at 8:48 AM on April 6, 2005

I recall reading that many U.S. government buildings here - and abroad - employ measures like that which you describe - setting a mask of barely audible music across window panes to create audio vibrations to block anyone using a laser microphone who might be eavesdropping from outside a building.

Some limited Googling reveals mention of this security technique:

1. "There were plenty of green trees around, too. They were a precaution against someone trying to eavesdrop using a laser microphone. There was probably music playing all the time, to cause the windows to vibrate just enough to thoroughly screw up anyone listening in, as well."

2. "Given a clear line of sight, one device enables someone to detect and and interpret sound waves vibrating against the glass window panes of an office."

Fact or fiction? I don't know. Maybe some other MeFites have knowledge/experience in this.
posted by ericb at 12:42 PM on April 6, 2005

Best answer: Don't get paranoid! They're simply a relatively new marketing technology developed - as far as I know - by a spin-off from Hull University: Feonic. The trade description is "Whispering Windows": Google it and you'll find distributors in the US and the UK.

Here's a very simplified explanation: How it Works. They look like this.

They also produce a consumer version which turns your desk/window/mirror into a loudspeaker: Soundbug
posted by blag at 3:59 PM on April 6, 2005

blag - my contribution above was, by no means, meant to induce paranoia, but to point out that I had heard that such technology existed.

Thanks for your posts. Fascinating.

BTW - it's nice to know that there is indeed a "consumer version" of a technology which has been employed in professional and government settings.
posted by ericb at 5:36 PM on April 6, 2005

Correction: *Thanks for your links*
posted by ericb at 6:08 PM on April 6, 2005

Sorry ericb, the "paranoia" comment was aimed more at people who were freaked out by a talking shop... It really is slightly disconcerting the first time you experience it. The retailer can even link the system up to video cameras with image recognition technology - imagine browsing a travel agent's window with your kids and hearing: "Hi! I notice that you've got children - have you seen our latest offers on trips to Disneyland?" etc...
posted by blag at 3:31 AM on April 7, 2005

imagine browsing a travel agent's window with your kids and hearing: "Hi! I notice that you've got children - have you seen our latest offers on trips to Disneyland?" etc...

Seems like the first step in bringing us to a world which contains targeted advertising similar to " the interactive billboards that identify passersby through eye-scans and shout personalized messages," as portrayed in the film Minority Report.
posted by ericb at 9:10 AM on April 7, 2005