

Gyrophone: Recognizing Speech  from Gyroscope Signals [pdf] - signa11
https://www.usenix.org/system/files/conference/usenixsecurity14/sec14-paper-michalevsky.pdf

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gjmulhol
What this tells me after a cursory read is that while this is in theory
possible, both hardware limitations and software ones limit the maximum
sampling frequency of a gyro. As such, it is going to be incredibly difficult
to recover any usable information. There are some indications that using the
right classifiers might improve results here, but their 10% accuracy for
identifying digits is about equivalent to random guessing. Expand the corpus
to include all of colloquial English (and potentially all other languages) and
that precision drops to a very low number.

With that said, someone crafty may be able to convince the OS (most likely
Android, in this case) to turn up the sampling frequency to 8kHz -- that same
sampling frequency as POTS -- and there might be a real risk of this technique
used as a data gathering technique (or at least a way to drain your battery
really fast).

