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 Valerie Hazan
Department of Speech Hearing and Phonetic Sciences University College London (UCL) Chandler House 2 Wakefield Street London WC1N 1PF United Kingdom
Speech Communication Across the Life Span
What factors affect our ability to communicate effectively at different ages across the life span?
The task that an infant faces when acquiring speech and language can be likened to deciphering a fiendishly complex code. What makes speech so complex is the fact that there is a lack of constancy between the acoustic signal and the abstract referent that it represents. Indeed, the acoustic patterns that cue phonetic distinc- tions vary from talker to talker. This between-talker variability is partly linked to the physical makeup of the talker, which, to a great extent, determines the acoustic characteristics of the speech that is produced. Talkers may also vary from each other in terms of their regional accent (Jacewicz and Fox, 2016) or the social and gender markers in their speech. Further variability in this complex code arises be- cause a given talker will not produce acoustic patterns in an identical fashion even when uttering the same word on different occasions; much of this within-talker variability occurs as a function of how fast we speak and in what speaking style, the physical and mental health of the talker, and other such factors.
The fact that infants are able to show a basic understanding of speech and begin to utter their first words within the space of relatively few months after birth is a source of wonder, and speech acquisition has been the focus of extensive research in the speech and language sciences. In the traditional view of acquisition, devel- opment in childhood is seen as a trajectory toward an “adult norm.” Indeed, many studies are concerned with establishing when this adult norm is achieved for dif- ferent aspects of speech production or perception. Given the population typically tested in experimental studies, this adult norm has been based on the testing of un- dergraduate university students within an 18- to 25-year age bracket. However, a picture is increasingly emerging that there are ongoing changes in speech produc- tion throughout the life span, from childhood to old age. The notion of an adult norm as a target for speech development is, therefore, becoming more blurred.
In this paper, I briefly review factors affecting these life span changes following the very initial stages of speech acquisition in preschool children and how they affect the production of speech. I arbitrarily define an “infant” as an individual from birth to 3 years, a “child” as between 3 and 12 years, an “adolescent” as between 13 and 18 years, a “young adult” as between 19 and 35 years, “middle aged” as between 36 and 64 years, and an “older adult” as aged more than 65 years. I also argue that investigating speech produced in communicative settings, for example, involving speech produced to impart a message to another talker, gives a more ecologically valid picture of speech production changes across the life span than can be obtained from more traditional “laboratory speech.”
Early Development of Speech Production
In the last few decades, there have been tremendous advances in our understand- ing of how speech is acquired, with a strong focus on development from infancy
36 | Acoustics Today | Spring 2017
| volume 13, issue 1 ©2017 Acoustical Society of America. All rights reserved.

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