Researchers of the University of Washington, USA are testing the prototype of their ApneaApp 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 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 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 used a Samsung Galaxy S4 but that's also a smartphone with one of the best frequency responses 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?
(Score: 2) by takyon on Monday June 15 2015, @07:58PM
Put your phone in airplane mode (before it's made obsolete by legislation allowing you to use electronic devices at all times on flight). Then wrap it in a sleeve of aluminium foil.
Try calling or texting your phone when it is not in airplane mode but is wrapped in the foil. The phone's silence will speak volumes.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2) by bob_super on Monday June 15 2015, @08:46PM
If I put the rest of the foil on my head, I can easily argue that the secret numbers the NSA calls from just don't make the phone visibly react...
With enough foil to make a cocked hat, I'd point out that my old phone used to make my PC speakers buzz two seconds before it ran, but the newer ones don't, obviously because the NSA doesn't want me to know that my phone is not really off...
Does Poe's Law apply to conspiracy theorists?