Augmentative and Alternative Communication -- AAC -- refers to non-speech modes of communication that augment spoken language. Electronic devices that digitize or synthesize speech, or non-electronic communication aids such as manual communication boards, are used for persons who have limited or unintelligible spoken language. Objects, photographs, graphics, pictographic or abstract symbols, or printed words are used to represent language concepts.
There are two main types of AAC devices (also know as Voice Output Communication Aids -- or VOCA's), and many variations according to the selection methods, message storage capacity, size, weight, cost, etc. Voice output is either digitized - electronically recording, storing and retrieving spoken messages, or synthesized by combining electronically-generated speech sounds.
Digitized devices produce human-quality speech but are limited by the amount of recording time available for storing words and phrases. Synthesizing devices have no such limits on message storage and may be operated in text-to-speech mode, but the voice quality is "robotic."
The AAC user can use a "direct selection" technique by pointing manually or with a head pointer, mouth stick or light pointing device to messages on an array or device "overlay." If the user has no physical method of pointing, they may use a scanning device which sequentially indicates messages in a repeating pattern. The user activates a single switch with some controlled body movement to select a message when the scan arrives at the desired location. Scanning may be visual or auditory.
There are many possible switch activation movements including manual or fingertip pressure, pneumatic sipping or puffing through a tube, or muscle flexion of any body part, such as an eye blink.
Devices with one or several digital message capability can be purchased for under a hundred dollars. There are digitized devices that can store hours of pre-recorded speech on grids of up to 128 key locations, ranging in cost from one to five thousand dollars. Synthesized speech devices are in the one to five thousand dollar range, many can be interfaced with computers, printers and environmental control units.
The newest solutions for augmentative communication combine both digitized and synthesized speech functions and are available as dedicated devices with full color dynamic screen displays (when a message is activated as on a computer monitor, the screen changes to reveal another array of choices). Laptop computers can also be outfitted with augmentative communication software to function as dynamic screen augmentative communication devices.
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