Abstract
Developing the monitoring system in a bathroom is important to prevent the accidents there. One of the method to prevent the accidents in a bathroom without violeting one's privacy is using an acoustic sensor. The authors proposed an idea of immersing a pipe, which an acoustic sensor is set inside, in the water. By this procedure, we can obtain not only a direct sound information from the people in the bathroom but also the water level information. That is, stationary wave depending on the water level will be formed inside the pipe and the frequency analysis of it enables the real time measurement of the level. But a thermometer is needed to the measurement of the water level in the proposed method.
To overcome this problem, the authors propose a new idea of using a pipe which has a narrow portion. That is, 2 types of the stationary wave are formed in the pipe. Therefore, we can obtain a direct sound information and the water level information without a thermometer.
