牙医的消声装置

[Sound of dentist drill.] That’s a sound that inspires fear around the world: the dentists’ drill. And fear of that sound itself could play a part in keeping some people from getting their regularly-scheduled check-up. Now, a solution to this “sound effect” may be in sight. Because researchers in London have developed technology to cancel out the drill’s unpleasant high-pitched whine.

Noise cancelling headphones usually do away with low pitches. So the scientists designed a variation that a dentist could keep on hand. The device fits between any MP3 player or mobile phone and the patient’s own headphones. The patients could still hear the dentist or listen to their own music. But the microphone and chip in the device sample the incoming sound and produce an inverted wave that cancels out just the sound of the drill. As the drill’s frequency changes, the waveform quickly adapts to maintain the silence.

The researchers have built and tested a prototype. They hope that it could eventually finally provide a definitive answer to the question, “Is it safe?”

—Cynthia Graber