From dvice:

Flexpeaker: paper-thin speakers made from, well, paper

We reported on speakers made from paper and tin foil a few weeks ago, and now another company is showing off what they can do with some wood-pulp. Based in Taiwan, the Industrial Technology Research Institute has created their own version of paper-thin speakers, really just tweeters, called Flexpeaker. They'll be sold as 8.5-inch by 11-inch sheets for $20, but they'll be available in much larger sheets, even rolls, so you could wallpaper a theater with the stuff, use it in a car headliner, or as the speakers built into an ultra-thin TV.

The speaker is made by layering thin electrodes and a prepolarized diaphragm between two thin sheets of paper. Their first application, they hope, is to use the Flexpeaker in cars as soon as next year. Then, movie posters, with the soundtrack or movie trailer highlights playing as folks walk by.

Unfortunately, the frequency response is 500Hz to 200kHz, completely unacceptable for serious listening. Thin, indeed. But, for some commercial applications, or with a properly crossed woofer/subwoofer, the technology has promise. I just hope those movie posters waterproof. If not, it could be wet, soggy mess.