A speech impairment is defined as an impaired ability to produce speech sounds. According to Communication Access UK around 14 million people in the UK have some form of speech impairment. These can range in severity from mild impairments such as the inability to produce certain sounds all the way to having no speech at all.
In terms of digital accessibility people with speech impairments may have issues with the following:
People with limited or no speech can also use speech synthesisers such as the system used by Stephen Hawking. Professor Hawkings system utilised a computer into which he could enter text which would be read out by a speech synthesiser. This text was chosen from a menu of common words with a hand switch at first but when he lost the mobility in his hand text would be entered by highlighting letters or words on his computer screen with the movement of a muscle in his cheek. This movement would be picked up by a sensor in his glasses and he would blink to actually select the word or letter. In later versions of the system it would utilise predictive text to predict what he would type next and give him a series of words to choose from. The designers of his communication system said that one of the predictive settings was to give him a choice of the word ‘black’ after he chose the word ‘the’. If he chose the word ‘black’ he would then automatically be given the word ‘hole’ as a choice.