United States Patent 4,877,027 31 October 1989
This invention relates to a hearing system for human beings in which high frequency electromagnetic energy is projected through the air to the head of a human being and the electromagnetic energy is modulated to create signals that can be discerned by the human being regardless of the hearing ability of the person.
Link To Patent
Similar methods of creating “clicks’ inside the human head are reported in I.E.E.E. Transactions of Biomedical Engineering, volume BME25, No.3, May 1978.