You can use a laser to transmit audio to a LDR or a light sensitive transistor/diode, which can then be used to run a speaker (with a battery attached). Essenti

You can use a laser to transmit audio to a LDR or a light sensitive transistor/diode, which can then be used to run a speaker (with a battery attached). Essentially fibre optics through the air. I did it once, the quality was rather lacking, since it used amplitude modulation instead of frequency modulation. Here's an instructable on it: http://www.instructables.com/id/How-to-Send-Sound-using-a-Laser/ http://www.instructables.com/id/How-to-Send-Sound-using-a-La... It's not quite what you're asking, but it's probably the closest you can feasibly get. I'm fairly sure that's also the way that laser microphones work as well.