Speech-generating device
Speech generating devices (SGD), also known as voice output communication aids (VOCA), include a range of voice output augmentative and alternative communication (AAC) systems that enable individuals with severe speech impairment to verbally communicate their needs.[1]
Characteristics
Speech generating software programs can be installed on desktop computers, laptop computers, and personal digital assistant (PDA) and dedicated communication devices providing individuals with easy access to different methods of using SGDs to communicate with others in various settings.[1] SGDs are important for people who have limited means of communicating verbally, as they allow individuals to become active participants in communication interactions.[2] Speech generating devices can produce electronic voice output using speech synthesis or by digitized recording of natural speech.[3]
Digitized speech generating devices
Digitized SGDs play the recorded natural speech of an individual other than the SGD user for voice output. Words, phrases or entire messages are recorded and stored onto the device for automatic playback upon command of the SGD user.[1][4] Digitized systems provide natural prosody and speech naturalness for the listener.[3] A person of the same age and gender of the AAC user can be selected to record the messages[3] and any language can be used due to the accessible process of manually recoding messages.[citation needed] However, with this method the user is unable to produce novel messages; they are limited to the messages recorded into the device, and spelling cannot be used.[3][5] Because digitized speech is recorded, memory space may be an issue, as sound files consume a significant amount of memory.[3][5]
Synthesized speech generating devices
SGDs using synthesized speech apply the phonetic rules of the language to translate the user’s message into voice output via a computerized speech engine (i.e., text-to-speech).[1][6] Users have the freedom to independently create novel words and messages and are not limited to messages that have been pre-recorded on their device by others. Individuals can use synthesized SGDs to formulate messages in a variety of ways, including letters, words, phrases, sentences, pictures, and symbols.[1][5] It is possible to use a combination of these methods for formulating and accessing messages on SGDs. With synthesized speech there is virtually unlimited storage capacity for messages with few demands on memory space.[3] Speech parameters can be manipulated by the user (e.g., speech rate, pitch range, gender, stress patterns, pauses, pronunciation exceptions, etc.)[5] However synthesized speech is not as intelligible as natural speech.[6] Synthesized speech are available in several languages.[5][6] Individuals may also use a combination of digitized and text-to-speech techniques on their SGDs to communicate.[6] As a message is entered into the system it is first converted to a pronunciation code, using a dictionary and the phonemic rules of the language and then it is converted to produce proper intonation, duration and stress. Speech is produced from this code via a digital-to-analog converter.[6] A moderate amount of computer memory is necessary for this process, but it does not require any extra time for the message to be converted from text-to-speech and it results in speech that sounds very natural.[6]
Access to speech generating devices
There are multiple methods of accessing messages on devices, which can be done directly, indirectly and with specialized access devices. Direct access methods involve physical contact with the system, by using a keyboard or a touch screen. Users accessing SGDs indirectly and through specialized devices must manipulate an object in order to access the system, such as manoeuvring a joystick, head mouse, optical head pointer, light pointer, infrared pointer, switch access scanning, or by Morse code.[1]
Notes
- ^ a b c d e f Aetna Inc. (2010). Clinical Policy Bulletin: Speech Generating Devices
- ^ Blischak, D. M., Lombardino, L. J., & Dyson, A. T. (2003). Use of speech-generating devices: In support of natural speech. Augmentative and Alternative Communication, 19, 29–35.
- ^ a b c d e f Glennen, Sharon L. and Decoste, Denise C. (1997). The Handbook of Augmentative and Alternative Communication. Singular Publishing Group, Inc.: San Diego, CA. pp. 88-90
- ^ Beukelman & Mirenda, 2005, p. 105
- ^ a b c d e Radomski, Mary Vining and Trombly Latham, Catherine A. (2007). Occupational therapy for physical dysfunction. Lippincott Williams & Wilkins. p. 527. ISBN 9780781763127.
{{cite book}}: CS1 maint: multiple names: authors list (link) - ^ a b c d e f Beukelman & Mirenda, 2005, p. 105-106
References
Beukelman, D. & Mirenda, P. (2005). Augmentative and Alternative Communication: Supporting Children and Adults with Complex Communication Needs (3rd edition). Baltimore: Brookes.