Educational Device for Detection of Harmful Sound Levels
Abstract: The purpose of this thesis was to design and construct a low cost noise dosemeter, according to the class 2 instrument specifications presented in IEC 61252 and IEC 61627-1. The idea being to provide an instrument for a first evaluation of the noise environment at a workplace. There is still a lack of knowledge in industry about the dangers of high sound levels and its effects on human physiology. By providing a low cost instrument, hopes are that more measurements will be carried out and in the end lead to improving the working conditions and health of employees.
The instrument consists, in essence, of a microphone connected to the ADC of a microcontroller via an anti-aliasing filter in the form of a Sallen-Key low-pass filter. Data is sampled and processed by an A-weighting filter, the purpose of which being to mimic human hearing, as described in the above mentioned standards. When the measurement session is completed the data can be presented to the user via LEDs, indicating exposure. Tests revealed that the anti-aliasing and A-weighting filters both performed as desired. The microphone could not be properly evaluated due to lack of equipment, but shows promising results. On the whole it seems to be a working concept.
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