Patent Date: Sept. 25, 1958

2995633 USA

A patent for a way of causing silent hearing through bone conduction from items touching the subject

The patent describes a method of using bone conduction (vibrating the skull instead of the air) in order to assist people with bad hearing. It could be used as a silent speaker. The examples suggest that a tooth is implanted with a device which then acts as a speaker.

Patent Date: Dec. 21, 1971

3629521 USA

A further patent for the ability to cause a sensation with radio waves that can now cause a voice sensation

The first patent regarding the Radio Hearing Effect (RHE). It claims to cause the sensation of hearing in a totally deaf person using Radio Frequency (RF). The patent mentions how when Audio Frequency (AF) is applied as well, it feels like you are actually hearing the sound.

Patent Date: March 7, 1972

3647970 USA

A patent for a method of simplifing and compressing speech

This method enables a speech waveform to be fit into a smaller representation. It allows people to send speech using less information, and for the signal to still be intelligable. It mentions transmission though physical mediums such as earth and water.

Patent Date: Oct. 16, 1972

3766331 USA

A patent for directly applying microwave signals to the brain to cause the sensation of a voice using electrodes

This device causes the sensation of hearing by using electrodes to administer electrical pulses with frequencies in the microwave range (not microwave radio).

Patent Date: Sept. 10, 1991

5047994 USA

A patent that allows an ultra sonic soundwave to vibrate a body and cause audible sound

Method of causing a subject to hear a sound using bone conducted ultrasonic sounds, that resonate to cause the actual sound in the ear. It's a silent speaker device.