My uncle was a career NSA man. In the 1970s, his job (I learned decades later) was to modify and maintain all the typewriters in the White House so their keystrokes couldn't be used to identify what was being typed on them. Presumably the concern was that something like a Buran eavesdropping system could be used to detect vibrations in windows, and the sound of the typewriter keys then extracted and analyzed to recover the text.

My grandfather (also career NSA) used to tell me that it would seem like fiction if people knew some of the things that technology and a good cryptanalyst could do. I think he was right.