Noise reduction of dental drill noise

Dental drills produce a characteristic noise that is uncomfortable for patients and is also known to be harmful to dentists under prolonged exposure. It is therefore desirable to protect the patient and dentist whilst allowing two-way communication, which will require a headphone- type system. Re-establishing good communication between the dentist and patient will be achieved through a combination of three noise cancellation technologies, namely, Passive Noise Control (PNC), Adaptive Filtering (AF) and Active Noise Control (ANC). This paper describes how far a test-rig has been developed to achieve sufficient noise reduction that the uncomfortable noise can no longer be heard. 1. DRILL NOISE CHARACTERISTICS Dental drill noise occurs at high frequency ranges, typically 2kHz to 6kHz, and is proportional to its rotational speed. Figure 1 shows the noise peaks of electromotor driven, which has a narrow band characteristic. Burr Bur shaft shaft 200.000 rpm rpm (3,33 (3,33 kHz) kHz) Intermediate shaft shaft 150.000 150.000 rpm rpm (2,5 (2,5 kHz) kHz) Figure 1 Electromotor driven drill, and its related peaks These pitched noises are produced by both electromotor and pneumatically driven drills. High speed dental