Interesting, plenty of activity on Linkedln on the same subject, but here flat dunk zero response.
Have people ever dealt with code word "TEMPEST" or EMC issues in the past, although the name has changed, it still exists even today.
Tempest (Transient ElectroMagnetic Pulse Emanation STandard) project is a joint research and development effort of the U.S. National Security Agency (NSA) and the Department of Defense (DoD) and has been classified for about 20 years.
There are a number of countermeasures - remember the Hessian net curtains, to prevent oversight through windows, this does not prevent vibrations from people talking within the targeted room, but it does reduce the likelihood that optical attacks will succeed. Also use for bomb blast protection to a certain extent too.
The other one which comes to mind "Get Smart" - the Dome of Silence, yes its a comedy, but these techniques have been experimented with in the past, although they appear to be a gimmick, even white noise generators can reduce the likelihood of being overhead - but these days with good analytical filtering systems, even these can be eliminated from the background noise.
An amusing moment from 1966: