> There are some parts of the specification that describe triggering microphones with a silent-to-humans sound, but again, the specification does not matter. Just the claims.
and how would one know in practice? Android doesn't even tell you until you if an app access the microphone (while app is in the background) until upcoming Android-P:
2 comments
[ 3.3 ms ] story [ 18.7 ms ] threadnitpicking.
https://www.theverge.com/2018/3/7/17091104/android-p-prevent...
The whole Data over Sound space needs a standard:
https://static1.squarespace.com/static/5129591ae4b0fd698ebf6...
If it isn't facebook it's going to be others (SilverPush, Drawbridge, Flurry (now Yahoo), ...)