Proposal and Design of Monitoring System in Private Spaces Modeled After Echolocation by FM Bats

In order to prevent persons from accidents in private spaces, the authors have proposed and designed an ultrasonic sensor system modeled after the echolocation function of FM (frequency modulation) bats. This system is suitable for private spaces where the use of cameras and electromagnetic sensors is either inappropriate due to privacy concerns or potentially harmful to individuals with electronic artificial organs. The sensor system was integrated into a monitoring system aimed at predicting and preventing drowning accidents in bathtubs by alerting the bathing individual or those outside the bathroom. To answer the research question of how far this system is suitable for monitoring individuals in the bathtub, we conducted some preliminary experiments. The preliminary experimental results demonstrate that the FM ultrasound system can accurately detect the position of a transparent acrylic pole of 25 mm diameter with 1 m length at 250 cm distance and can follow the movement of the pole with shower noise of 80 dB (SPL) in a bathtub, which shows the system is less susceptible to noise. Furthermore, we evaluate the system's ability to detect two types of drowning motion patterns with a volunteer bather in the bathtub. From the result, the system is seen to be effective in alerting the bather by an alarm or voice notification, thereby helping to prevent drowning incidents. The study also explores issues that need to be solved as the monitoring system in bathtubs, identifying avenues for future research to make the system suitable for practical use. The significance of this study also extends to the field of bioacoustics, especially as it pertains to FM bats.