Our 24h CreatED hackathon project.
This Java app allows you to encode a URL into a wav file, which if played on a speaker will produce ultrasound which cannot be perceived by humans. A smartphone, or other device, can however pick up a limited amount of audio in the ultrasonic (20khz+) range. The recorded audio can be analysed and decoded, and the URL can be extracted.
We think that this has potential applications in rivalling QR codes, where the encoded ultrasonic URL will be played in a loop somewhere. Surrounding smartphones can then detect the URL and send the user to a page - no need to launch the camera and point it anywhere.