BBC News - Device cancels out the sound of the dentist Some people find the sound of a dentist's drill distressing An invention which cancels out the noise of a dentist's drill could help people overcome their fear of a check-up, researchers say. For many, the sound of the drill is a big cause of anxiety when it comes to visiting the dentist. This new device allows patients to listen to music on an MP3 player, while the sound of the drill is blanked out. Patients are, though, still able to hear the dentist's voice because not all sounds are filtered out. The device is similar to noise cancelling headphones. It works by turning the sounds of the dental consulting room into a digital signal. A special chip called a digital signal processor analyses the incoming sound from microphones placed close to the dental drill. It produces an inverted sound wave to cancel out unwanted noise in the headphone signal. It also uses "adaptive filtering" technology, where electronic filters lock onto sound waves and remove them, even if the wave's amplitude and frequency change as the drill is being used. But this also allows other noises like the dentist's voice to come though. So a patient could simply plug the device into their MP3 player and then, via their headphones, listen to their own music without being disturbed by the noise of the drill but still be able to hear the dentist.