https://en. wikipedia.org/wiki/Tempest_(codename)
"While much of TEMPEST is about leaking electromagnetic emanations, it also encompasses sounds and mechanical vibrations.[5] For example, it is possible to log a user's keystrokes using the motion sensor inside smartphones.[7] Compromising emissions are defined as unintentional intelligence-bearing signals which, if intercepted and analyzed (side-channel attack), may disclose the information transmitted, received, handled, or otherwise processed by any information-processing equipment."