The branch of science devoted to the transmission, reception, and reproduction of sounds, such as speech and tones that represent digits for signaling. Note 1: Transmission may be via various media, such as wire, optical fibers, or radio. Note 2: Analog representations of sounds may be digitized, transmitted, and, on reception, converted back to analog form. Note 3: "Telephony" originally entailed only the transmission of voice and voice-frequency data. Currently, it includes new services, such as the transmission of graphics information. 2. A form of telecommunication set up for the transmission of speech or, in some cases, other sounds.