A Silent Drill

A new invention could allow dentists to cancel out their cringe-inducing drills. Cynthia Graber reports:

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.