Reducing the noise from dental drills with adaptive filtering

Objectives: Dental drills produce unwelcome noise which patients dislike and can be damaging to the hearing of the dental team. The aim of this study was to reduce the drill noise levels heard by the patient and staff in the 4kHz to 11kHz frequency range by at least 6 dB. Methods: Digital Notch Filters were used at the major noise frequency peaks. Recordings were made in a dental clinic and noise reduction tests were made on the recordings. The noise peaks vary during the drilling procedures as the drills are loaded and the adaptive filters alter to match the new noise peaks. This aims to provide noise reduction as the noise peaks move. Results: The filter achieved detectable reductions in the sound levels in the offensive frequencies. For high speed drills the peaks near 5KHz and 10kHz were both reduced by at least 11dB, and sometimes as much as 23dB. With slow speed drills we achieved similar reductions, whilst for an ultrasonic scaler the peak near 8kHz was reduced over 23dB, which is equivalent to reducing the noise sound power by a factor of 200. Conclusion: the noise levels were significantly reduced and further work is planned to develop a system to work in real time in the surgery for the benefit of patients and staff.