This category includes methods and devices that enable communication, such as radios, and speakers.
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.
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.
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.
This device causes the sensation of hearing by using electrodes to administer electrical pulses with frequencies in the microwave range (not microwave radio).
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.