Experimental commmunication aids for the deaf

High-frequency loss is a common hearing impairment and several methods of recoding speech have been developed to make better use of low-frequency residual hearing. An important application of these devices is to help the deaf person articulate correctly by providing him with usable auditory feedback of his own speech production. In one such device, /s/ and /sh/ sounds are replaced by low-frequency pulse trains which are clearly distinguishable, even to those having limited, low-frequency residual hearing. A pilot study showed this device to be of value in teaching severely hard-of-hearing children to articulate these sounds correctly. For the totally deaf, communication must involve some other modality. A simple, practical device is the experimental visual-tactile telephone which contains a voice-operated light and special tactile transducer for monitoring the speech signal. A key is provided for transmitting messages by some mutually agreed upon code. Another means of communication which may overcome some of the difficulties of Morse-code transmission is to spell out the message on the dial of a conventional Touch-Tone telephone. An experimental system for using a Touch-Tone set in this way is currently being evaluated. Since as many as three letters are assigned to each button, a simple code is necessary for identifying the transmitted symbol. One press indicates the first letter, two rapid presses the second letter, and three rapid presses the third. At the receiving end, the corresponding buttons on the dial are illuminated and the message can be decoded mentally. With additional circuitry, a simple decoding unit may be used to provide a visual indication of the transmitted symbols. Transmission speeds of 8 to 10 words per minute are typically obtained after 1 to 2 hours practice.