‘In actual fact, a suitably modified amateur radio transmitter operating in either the 420 to 450 megahertz band or the 1.3 gigahertz band, with a highly directional antenna, is capable of transmitting voice to skull signals at less cost than the price of an automobile.’
They are a very faint sound, therefore a person interprets them as their own thoughts. Since they are a very faint sound, only those things that are know to a person can be manipulated. Put it simply they won’t be able to teach you Chinese. An example of this is that if a person says a sentence very slowly and close to your ears, then you will only understand it if you know it or parts of it, otherwise your interpretation of what’s being said would be different as compared to what was actually said
