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)

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

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