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In the graying society, it is important to monitor health-related biosignal with sensors in the living environment for the sake of emergency response and long-term health management. In order to use biosignal data monitoring systems daily at home, noninvasive monitoring and system maintenance are crucial. We propose a method of estimating the sleep stages of sleeping subjects through noninvasive measurement of heartbeat and respiration using a pneumatic method and an air mattress. However, the method incurs maintenance for periodically refilling the air of the mattress. In this paper, another pneumatic method, which uses an air tube made of the silicon rubber instead of the air mattress, is proposed. The change in S/N ratio in heartbeat and respiration signals, under greater background noise, are compared for the following: in a room with wooden flooring; in a room with tatami mats; in a bathtub; and in a lavatory. The results show that both the heartbeat and respiration can be measured with the S/N ratio of around 30 dB, and the signal of each heartbeat can also be confirmed provided the maximum background noise in the room with wooden flooring, in the room with tatami mats, in the bathtub, and in the lavatory are 0.1 m/s 2,0.9 m/s2, 100 mI/s, and 0.1 m/s 2, respectively.
Date of Publication: Dec. 2009