I'm doing a research paper about electronic wireless communication using sound. I've got a few reference regarding its use in underwater networks, networking within a body in a medical context, and one regarding communicating information through a steel wall (such as a sealed pressure vessel). I've not been able to find much of anything on consumer level devices. I believe I saw a reference on this forum as well to using ultrasound through the PA system of a building for automation purposes of some kind or something like that. I do not know if this was a hypothetical example or something that has actually been implemented by anything. If you know of any references regarding audio data communication being used in consumer devices or home/office/public building automation context, please point me to them. NOTE: This paper is specifically about data communication. Ultrasonic imaging, range finding, and motion detection are not appropriate for the topic.