History is replete with rival inventors battling one another to bring breakthrough creations to market: Howe and Singer over the sewing machine, Bell and Gray over the telephone, Edison and Swan over the light bulb. In many cases, the winner went on to become a household name and captain of industry, while the loser was essentially forgotten.

Now, in that same tradition, two inventors are each staking claim to a new audio technology that corporate customers say will have a huge market within the next five years. Known as directional sound, it uses an ultrasound emitter to shoot a laserlike beam of audible sound so focused that only people inside a narrow path can hear it. "It's phenomenal," says Simon Beesley, an audio marketing manager for Sony's European business division. So far Sony has sold just a handful of directional-sound systems for specialty installations in stores and other locations, but ultimately, says Beesley, "Without question, this is going to be a billion-dollar-plus product."