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cidence of voice disorders than do nonteachers (Roy et al., 2004). Many women in their fifties may experience signifi- cant changes to their voice due to hormonal changes linked to the menopause that cause physiological and functional changes to the vocal folds (see the review in D’haeseleer et al., 2009). This can result in a decrease in fundamental fre- quency linked to increased vocal fold mass, although it is difficult to separate the effects of menopause from those of vocal aging. Changes in pitch characteristics and speaking rate can also be seen in adults as a result of depression or other mental health issues (for a review, see Cummins et al., 2015).
Speech Production in Later Adulthood
When considering how speech production changes in lat- er adulthood (e.g., 65 years onward), a number of factors that are surprisingly similar to those that affect adolescents are found. In both age groups, changes in vocal tract size occur, with documented increases in vocal tract length in older adults, resulting in increased vocal tract volume (Xue and Hao, 2003). Both age groups also experience changes affecting the larynx, although these are less drastic in older adults where the physiological changes to the larynx include a thinning of the vocal folds and hardening of the laryngeal cartilages. Also, motor control appears to be reduced in both groups compared with young adults; adolescents and older adults show greater within-speaker variation in articula- tory movement and placement. Finally, there are cognitive changes in both groups that may affect the willingness to make additional efforts to be understood and the empathy experienced toward a conversational partner. This could af- fect the effort they are prepared to make to be understood by an interlocutor who is having problems communicating. A useful review of various influencing factors can be found in Hooper and Cralidis (2009).
These various factors can lead to changes in speech produc- tion in older adults, although the degree to which these af- fect the ability to communicate effectively and fluently is still a matter of debate; there is great individual variability in speech production performance given the complex inter- relation of many external influencing factors such as physi- cal and mental health, cognitive abilities, and hearing. Typi- cally, changes have been shown in pitch characteristics, with the fundamental frequency of the voice reducing with age in women but increasing or remaining stable in men. Vocal fold vibration also tends to be less stable in older talkers, re- sulting in decreased stability in terms of both the frequency and amplitude of the sound source (for a review, see Baken,
2005). In terms of speech articulation, older talkers may show reduced accuracy relative to young adults when pro- ducing complex novel words (Sadagopan and Smith, 2013), although older adults showing high accuracy do not show decrements in motor coordination, and age-related differ- ences were only found in that study for long words with a complex structure. The articulation rate has also been shown to be reduced in older adults compared with young adults for both read speech and conversational speech (Jacewicz et al., 2010).
In addition to these changes in speech production, older talkers also show other changes that can affect their abil- ity to communicate effectively. It is well documented that a high proportion of older adults experience a degree of age-related hearing loss or presbyacusis that has a number of consequences (see the review in Gordon-Salant, 2014). Hearing thresholds are raised, especially for high-frequen- cy sounds, and the dynamic range is reduced. Presbyacusis is also linked to a broadening of auditory filters within the cochlea that has the serious consequence of making it es- pecially difficult for individuals to perceive speech in noisy environments due to increased masking.
This combination of potentially weaker speech production and difficulties in perceiving speech can lead to a “perfect storm,” at least for individuals in later old age conversing with each other. These older adults may find it difficult un- derstanding each other and may not be able to counteract these problems as effectively as younger adults by making adaptations to their speech production, such as using a “clear speaking style.” To compound these difficulties, if conversing in a day care environment, for example, interference from a television or radio in the background or other conversations may further affect the ability to communicate effectively.
Examining Speech Production in Spontaneous Speech Across
the Life Span
Most studies examining speech production characteristics at points along the life span have based their investigations on speech produced in laboratory settings, with talkers reading materials such as words or sentences or doing tasks to elicit spontaneous speech monologues such as describing a picture or recounting a simple story. Although such an approach en- ables researchers to record speech that is well controlled and comparable across talkers, it lacks a key dimension in speech production, that of communicative intent. The speech pro- duced in this way would not reflect how speech production
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