Position detection and remote controls powered by micro whistles

This paper describes the design and detection of mechanically actuated micro whistles not equipped with any electronics. When actuated, the micro whistle generates an ultrasonic tone above the audible range. A set of three or more microphones in the near record this tone and the position of the whistle is calculated from the differences of the arrival times of the acoustic signals at the microphones. In experiments the positions of whistles were measured in a 2 m × 2 m area with an accuracy of less than 10 cm. Besides this, micro whistles have been employed as remote controls such as switches for room light or air conditioning. The micro whistles have been fabricated by ultrasonic hot embossing of thermoplastic foils at low-cost and their overall size is approximately 1 cm. The paper also describes how to overcome obstacles such as accidentally generated ultrasonic noise, frequency shifts due to changing activation forces of the whistles, and distinguishing the signals of different whistles.