WindTrack: Leveraging Sound and Wind to Track Angular Position of Users on Commercial Internet-Connected Fans

A recent trend in electric fans is the support of smarter features based on Internet connectivity, such as remote control. This work opens new opportunities to make these devices more intelligent, particularly by proposing WindTrack, a novel angular positioning technique for electric fans. This would encourage the emergence of a new class of smart fans that use spatial information for automatic wind direction control. Many works have extensively studied angular positioning, but had limitations realizing such smart fans in terms of deployability (due to hardware requirements), accuracy, and usability. WindTrack overcomes these limitations by leveraging the acoustic phenomenon of refraction caused by wind. More specifically, it transmits and receives sound signals by using a smartphone located close to a user, while operating a fan in an oscillating mode. Therefore, WindTrack only requires Internet-connected fans for collaboration with smartphones. It then identifies the user's angular position based on the relationship between the propagation characteristics of the received signals and the oscillating fan. We further improve the robustness of WindTrack by using multiple speakers and microphones built-in smartphones and listening to wind sounds captured when wind passes across microphones. Extensive experiments on a WindTrack prototype demonstrate that it can achieve an angular positioning accuracy of a few degrees, especially in various environments and with no modification to commercial smartphones and Internet-connected fans.