A Data-Over-Sound Application: Attendance Book

High-frequency sound beacon is used for various purposes such as advertising, location detecting, and tracking devices. Due to smartphones with speakers and microphones capable of handle high frequency, anyone can use ultrasonic beacon today. Google's Nearby Messages API or Starbucks location beacons are high-frequency data-over-sound applications that are popular to developers and users. However, these high-frequency beacons are not suited for delivering text data because they are prone to the interference of background sound and it heavily depends on the performance of the Digital-to-Analog converter (DAC) and the Analog-to-Digital converter (ADC). In this paper, we propose a method to broadcast data using data sequence control and error correction algorithm for high-frequency sound data communication and its application for an attendance book. The client receives the broadcasted JSON data encoded in UTF-8, processes the data, and reports to the server to identify the attendee location. Experiments have shown that at least 5 smartphones can process at the same time and the operation is guaranteed to 3-meter distance from the speaker. This study shows that data communication using high-frequency sound can be applied to a wide range of applications when sequence control and error correction are properly performed.