3 ms·
18-19 kHz is usually high enough; smartphone speakers can play that fine from my experience. Yes, battery drain is an issue. Most apps use a background service
by Cyph0n 10y ago
18-19 kHz is usually high enough; smartphone speakers can play that fine from my experience.
Yes, battery drain is an issue. Most apps use a background service that wakes up at a fixed interval. The longer the interval, the longer the broadcast has to be though, so it's basically a trial and error kind of thing.
- MichaelMoser123 10y agoAnother issue (besides the privacy issue) is that it may be annoying for pets. Dogs and cats can hear these sounds. Also the apps on the phone have access to the microphone (even though they probably do not need this permission for any other purpose), so these apps are all potential listening devices.
- williamtrask 10y agoi'm so glad you said this... made my day
- zdkl 10y agoClock sync? Protocol usually is to check NTP and broadcast at prechosen times if you wanna keep the battery drain down.
- Cyph0n 10y agoI'm talking about the phone receiving a broadcast. The app has to be designed efficiently such that it minimizes network activity and doesn't hog the input audio stream. You also have the issue of trying to maximize the probability that a device in proximity to a beacon will pick up the full message. So you need some redundancy, which obviously increases overhead. NTP sounds like it would work. As you kindly noted, just make sure the beacons broadcast at a agreed upon time and in fixed increments.