Undergoing dental treatment is usually a very unpleasant experience for people who have toothaches, especially when they are hurting and there exists some intolerable mechanical noise. To reduce the noise and promote the work efficiency of dentists, a new noisefiltering earplug system with optional music was developed to filter out dental machine noise; if necessary, it can also be adopted as a solution to reduce pain and anxiety of patients during treatments. Furthermore, it can also simultaneously serve as a communication tool between the patient and dentist. In this study, various kinds of noises were initially collected through an off-line receiver and then connected to a personal computer. The software, CoolEdit and LABVIEW, were used to analyze the frequency ranges of the mechanical noises, and a cutoff frequency was identified through several comparisons. After the cutoff frequency was determined, the active noise-filtering system was designed with several circuits to filter out those frequencies higher than the cutoff frequency but reserving only the range of speech. In addition, music signals from an MP3 or CD player can also be transmitted into the earplug system for increasing the signal to noise ratio. The anxiety and tension of patients during treatment can thus be partially relieved by the euphonious music, and the pain of toothaches of patients might be further reduced. Moreover, when the voice signal from the dentist is transmitted into the patient’s earplug, the musical signal will automatically reduced by 12 dB for convenient communication. It was found that the developed noisefiltering earplug system performed well in several tests, such as detecting various powers of signals by monitoring the waveforms, identifying variations in noise and speech signals before and after the use of the filter, and checking working conditions of the designed circuits.

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