DARPA’s research into brain-computer interfaces (BCIs) using sound waves resonates with Nikola Tesla’s idea that the entire mental system of humankind could be controlled electronically.

“If you want to find the secrets of the universe,
think in terms of energy, frequency and vibration”
– Nikola Tesla

The Defense Advanced Research Projects Agency (DARPA) is pursuing a range of minimally-invasive approaches that use optics, acoustics, and electromagnetics to record neural activity and/or send signals back to the brain at high speed and resolution.