Imagine this: a sound system “speaker” that instead of blasting out soundwaves in the audible range sends out a highly-focused direction beam of ultrasound, completely inaudible to the human ear. But when your head is placed inside the beam, your skull transforms these waves into something that only you can hear. Headphone-less headphones. That’s exactly what Elwood Norris has built and is demonstrating to industry. The article points out some of the neat-o uses for such a technology as well as showing how it can be used for evil.