A team of researchers at MIT has developed a loudspeaker as thin as paper. The ultra-thin film can turn any surface into a loudspeaker, requiring little power to produce a high-quality sound. The researchers suggest many applications for the material, including wallpaper and smart devices with limited battery life.
https://www.notebookcheck.net/Paper-thin-loudspeaker-developed-at-MIT-could-be-used-as-wallpaper.616913.0.html
Very cool concept, but that sounds very tinny. There's, unsurprisingly, no bass, and not much mids. Just sounds very flat and empty.