On its website, Able Planet likens the technology to replacing a single C note on a piano with a C chord created by playing several C keys together. If the listener can't hear one of the C notes because of cochlear damage, she'll still hear the chord because of the redundancy of having several "versions" of the note.

This focus on enhancing the harmonics distinguishes Able Planet's products from devices that improve clarity by using noise-reduction algorithms that generate out-of-phase waveforms to cancel out undesired sounds. (Many of Able Planet's devices offer active noise cancellation as well.)

Kevin Semcken, Able Planet's CEO, pursued the technology because he was struggling with a high-frequency hearing loss himself. "To test the impact on intelligibility," he says, "we put the technology into one of two identical headphones, and I could easily hear the difference. I switched between them and was able to hear high-frequency tones in the Linx Audio headphones that were not intelligible in the unretrofitted version."

Able Planet is taking aim at the computer-gaming population with one of its lines of Linx Audio-enabled headsets, called LoSt-CaUzE, its nonstandard capitalization in emulation of the quirky typography favored by gamers. Many popular games are played in multiplayer mode over the Internet, with players talking to each other to strategize. A review of the LoSt-CaUzE headset noted that the Linx Audio technology made it especially easy to hear the in-game chatter of the other players amid the gunfire and footsteps.

It's not every day that one finds a technology designed to make women's voices and wanna-be soldiers' voices easier to hear, but there it is: an innovative use of high-frequency harmonics.