Speech-generating devices (SGDs), also known as voice output communication aids, are electronic augmentative and alternative communication (AAC) systems used to supplement or replace speech or writing for individuals with severe speech impairments, enabling them to verbally communicate their needs. SGDs are important for people who have limited means of interacting verbally, as they allow individuals to become active participants in communication interactions.
There are several input and display methods for users of varying abilities to make use of SGDs. Some SGDs have multiple pages of symbols to accommodate a large number of utterances, and thus only a portion of the symbols available are visible at any one time, with the communicator navigating the various pages. Speech generating devices can produce electronic voice output by using digitized recordings of natural speech or through speech synthesis—which may carry less emotional information but can permit the user to speak novel messages.
The content, organization, and updating of the vocabulary on an SGD is influenced by a number of factors, such at the user's needs and the contexts that the device will be used in. The development of techniques to improve the available vocabulary and rate of speech production is an active research area. Vocabulary items should be of high interest to the user, be frequently applicable, have a range of meanings, and be pragmatic in functionality.
There are multiple methods of accessing messages on devices: directly or indirectly, or using specialized access devices—although the specific access method will depend on the skills and abilities of the user. SGD output is typically much slower than speech, although rate enhancement strategies can increase the user's rate of output, resulting in enhanced efficiency of communication.
The first known SGD was prototyped in the mid-1970s, and rapid progress in hardware and software development has meant that SGD capabilities can now be integrated into devices like smartphones. Notable users of SGDs include Stephen Hawking, Roger Ebert, and Tony Proudfoot.
Speech-generating systems may be dedicated devices developed solely for AAC, or non-dedicated devices such as computers running additional software to allow them to function as AAC devices.
What They Are
A speech generating device (SGD), also referred to as voice-output communication aids (VOCA), are electronic devices that allow the user to select messages to be spoken aloud, thereby assisting people who are unable to use natural speech to meet the majority of their communication needs. SGD technology ranges from simple to complex. Dedicated devices are intended for communication purposes only, while others are integrated into portable computer systems. Additional components may include but are not limited to environmental controls, switch access, rate enhancement programs, and appointment schedules and reminders.
What They're Not
SGDs are not the answer for every environment or communication need. The range of complexity is not a hierarchy, but rather an array of features that tries to address the wide variety of consumer needs. No one device is right for everyone.
How They Work
Letters, words, phrases and sentences can be selected, alone or in combination, from static or dynamic overlays in order to have information spoken aloud by the device to generate language. Voices may be recorded or computer-generated.
While low-tech tools provide the intimacy of co-constructing messages with a communication partner, high-tech SGDs provide auditory information that gives receptive feedback to the device user and familiar output to the partner.
The auditory feedback provides reinforces selections made by the user, models language, provides extra speech input for children who with significant delays who will eventually develop functional speech.
Auditory output is also especially helpful for communicating with unfamiliar partners who may not know how to respond to more subtle communication strategies.
SGD technology provides features such as the following:
Dedicated: The hardware and software is designed solely for communication purposes.
Integrated/Communication Software: The hardware is designed to support both communication software and other applications. Integrated systems usually run on a Windows platform and have a sound card more conducive to voice output.
Digitized Speech: Digitally recorded human voices speaking actual words and sentences are stored in the device and played back upon selection. Some can contain sequential messages in a pre-determined order. Some have language assigned to specific buttons that can be accessed individually or in combination as determined by the user.
Synthesized Speech: Messages are converted via text-to-speech technology using speech generated by a computer that sounds similar to the human voice. There are a variety of device-generated voices to suit a user’s gender and age.
Static Display: These are generally customized via paper overlays that correspond to the language programmed into one of multiple levels.
Dynamic Display: Language selections are displayed via a touch screen. When a selection is made, a message is communicated or a new array of choices appears.
Handheld Devices: There are a growing number of software programs and iPod/iPhone applications with communication software.
Language Representation: Language can be represented by text, symbols, or photographs. Messages may be retrieved as sequential social scripts, phrases/sentences, single words, or letters.
Language Organization: Language can be organized in a myriad of ways. There are a number of commercially available packages stemming from the research and development of both professionals and manufacturers.
Access: Language may be accessed via direction selection using one’s hand, head pointing, or eye pointing, or via switch access scanning methods.