Information Transmission with Elementary Auditory Displays

A procedure for transmitting the letters of the alphabet by tone-coded signals was examined in quiet and against a noise background. The procedure employed successive selections, each from among a small number of alternatives, in order to transmit a target vocabulary of 25 letters. Four stimulus variables: tonal frequency, sound level, location, and duration were examined, one at a time. Successive selections were made among two, three, and five alternatives per variable. The highest reception rate was obtained with a three-alternative frequency-coded display. Reception of tone-coded signals in noise was nearly equivalent to that in the quiet, when the tonal signals were about 3 db above masked threshold.