Acquisition of biomedical signals using microphones of MEMS technology
A system for biomedical signal acquisition using MEMS microphones (Micro Electro-Mechanical Systems) as sensors is studied and developed. While these microphones are designed for audio, typical biomedical signals’ spectrums are far below audio frequencies. Therefore, a special approach is required for acquiring biomedical signals using MEMS microphones. This paper is focused on consider these microphones for acquiring signals of pressure in the airway, arterial pulse, and heart sounds. After acquisition and sampling of the signals, each one is properly filtered and amplified considering its bandwidth and amplitude, and the frequency response of the MEMS is compensated when required. In addition, the developed system allows the measurement of the pulse transit time (PTT), allowing a continuous estimation of blood pressure, because it was possible simultaneously obtaining the heart sounds and the arterial pulse signal. Measurements on the signals acquired were performed. Airway pressure signals obtained were not physiologically understandable. On the other hand, arterial pulse signals showed similarity with those observed in the literature. The cardiac sound s1 and s2 were successfully obtained and, in some cases, s3 was also detected. It was possible to measure the PTT in a non-invasive way, resulting this work a first step for future works.