Speech communication in older adults: an acoustic and perceptual investigation

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Speech communication can be difficult for older people, due to the combined effects of age-related hearing loss, which is common over the age of 65, age-related decline in the quality of phonation and speech articulation, and cognitive problems such as poorer short-term memory and processing speed. Past studies of how older individuals perceive and produce speech sounds have tended to consider these abilities independently of each other using controlled materials, such as read words or sentences. These studies tell us little about how older speakers function when using speech for communicative purposes, and how these various factors interact. For example, it has been shown that older people benefit from seeing their interlocutor in conversations, but audiovisual speech places greater demands on cognitive processing than auditory speech which leads to increased listener effort and reduced information recall. In our project, we propose to gain a comprehensive account of older people's speech production and perception in situations involving communication with another individual. Adults with age-related hearing loss and the rarer group of older adults with normal hearing will be included as well as younger adult controls. In Study 1, communication with another speaker, while reading sentences or completing a problem-solving task, will either be in good listening conditions, where both speakers hear each other normally, or in adverse conditions, where the participant has to get their message across to another speaker who has a simulated hearing loss or when both are speaking in a noisy background. These comparisons will enable us to get a sense of the degree to which an older person is able to adapt their speech to overcome difficult listening conditions, a skill which is of paramount importance in speech communication in everyday life. We will obtain high-quality digital recordings of the participants' speech but will also, via sensors placed on the neck, record information about their vocal fold vibration, which determines the quality of their voice. Video recordings will also be analysed to investigate whether older speakers make use of eye gaze and head gestures to signal aspects of discourse such as turn-taking and back-channelling (e.g., saying 'okay' to signal understanding), to the same degree as younger speakers. In Study 2, older and younger listeners with normal and impaired hearing will be presented some of the sentence materials recorded in Study 1 by all speaker groups in good and adverse listening conditions. Tests will be presented in both auditory-alone and audiovisual conditions. Intelligibility tests will be run to see what impact age, hearing status and visual cues have on speech understanding and to see whether the 'clear speech' adaptations made by older speakers to counter the effects of poor communication conditions gives the same benefit to that of younger speakers. Sentence recall tests will also be run to investigate whether the listening effort is reduced listening to 'clear speech'. This project will lead to a better understanding of the effects of ageing on speech communication and of the various contributing factors to potentially degraded speech communication in a population of 'healthy aged' individuals. These benchmarks will be of use for practitioners such as speech and language therapists and audiologists who work on aspects of communication with older people who have health complications. A better understanding of communication difficulties that older individuals experience and of their strategies to overcome these difficulties will also assist professionals such as social workers and care professionals who work to improve quality of life for older people, as well as developers of speech technology devices for telemedicine and remote monitoring. Importantly, this research will also contribute to our basic understanding of speech perception and production development across the lifespan.