Totally true and old common knowledge, check this out: https://en.wikipedia.org/wiki/Tempest_%28codename%29 https://en.wikipedia.org/wiki/Tempest_%28codename%29

Totally true and old common knowledge, check this out: https://en.wikipedia.org/wiki/Tempest_%28codename%29 https://en.wikipedia.org/wiki/Tempest_%28codename%29 When chips and devices were slower and used more energy, it was just easier to observe those differences. I also have had many mobile phones which leaked information as audio, I think most of that leak was from RF tramsitter unit power consumption and speaker amplifier power not being properly filtered. But it's just perfect example of acoustic information leak.