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kaszz [soylentnews.org] writes:

Researchers of the University of Washington, USA are testing the prototype of their ApneaApp [washington.edu] to diagnose sleep apnea, a health problem that can become life-threatening. To monitor a person's sleep, the app uses a smartphone as an active sonar system that tracks tiny changes in a person's movements during sleep. The phone speaker sends out an inaudible sound that bounce off the sleeping person's body and which is picked up again by the phone's microphone. "It's similar to the way bats navigate," said Rajalakshmi, lead author and a doctoral candidate in the UW's department of computer science and engineering. "They send out sound signals that hit a target, and when those signals bounce back they know something is there." In technical terms, the app continuously analyzes changes in the acoustic room-transfer-function [wikipedia.org] which is sampled at ultrasonic frequencies to detect motion and it works at a distance of up to 0.9 meter. This is very similar to what the iPhone app Sleep Cycle Sonalarm Clock [sonalarm.net] does, except that the UW researchers have improved the sensitivity of the method so it can precisely track the person's breathing movements which allows it to not only detect different sleep phases but also sleep apnea events. The advantage in both use cases is that the sleep monitoring is contact-less (there's nothing in the user's bed that could disturb their sleep) and doesn't require any additional hardware besides the user's smartphone.

The researchers uses a Samsung Galaxy S4 but that's also a smartphone with one of the best frequency responses [anandtech.com] with a total variation of only 0.014 dB in a 61 tone sweep from 20 - 20 000 Hz so perhaps this kind of use can only be done with specific smartphones?

Original Submission