A failed effort to soften the noise from British military helicopters led to a breakthrough enabling surfaces from mobile telephone screens to car roof liners to be turned into stereo speakers.

The technology was sold to Cambridge-based NXT, which christened it "SurfaceSound" and arranged for it to be crafted into Toyota cars, Gateway computers, Hallmark greeting cards and more.

"The UK ministry of defense was experimenting with a way to dampen the sound in helicopters and developed a honeycombed material that did the opposite -- conducted sound," James Bullen of NXT told AFP.

A prototype of a folding flat-panel speaker about the size of a pocket journal and 14 millimeters thick was among creations NXT showed off at this week's Consumer Electronics Show in Las Vegas.

Bullen flipped open a Butterfly speaker made by Iqua Ltd. and plugged in an iPod Nano. An instant later, Frank Sinatra's voice belted out richly in NXT's suite in the Las Vegas Hilton.