Augmentative & Alternative Communication : David R. Beukelman :NCBI Bookshelf. The ease and simplicity of use of typical natural speech mask the complexity of a speech production process that involves precise control and coordination of respiration, voice, articulation, and language comprehension and expression van der Merwe, For many, speech is the external expression of language, and the motor skills involved are performed with accuracy and speed, without conscious control Netsell, With impairment, alterations in speech subsystems become apparent and the complexity revealed. The primary rationale for individuals' electing to use augmentative and alternative communication AAC is the inability of their natural speech to meet all of their daily communication needs.
Augmentative and alternative communication
The Promise of Assistive Technology to Enhance Activity and Work Participation.