Speech communication in older adults: an acoustic and perceptual investigation

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.

Although this project is primarily a basic science project concerned with advancing our knowledge of the impact of ageing on speech communication in good and adverse conditions, we consider that the work has the potential to have impact in a number of fields. The main non-academic beneficiaries of this research, in the short- to medium-term, will be speech and language therapists (SLT), adult social care and charity sectors and, in the longer-term, developers of speech technology applications for older users. Finally a project leading to a better understanding that speech communication in older adults is of wider relevance to the general public.

Speech and Language Therapy: Much of the caseload for speech and language therapists (SLTs) working with adults involves older adults, primarily referred following stroke, which might result in dysarthria. When assessing the impact of stroke on speech production, it is paramount to have some normative data on the effect of ageing on speech articulation in the 'healthy aged' but this information is scarse at present and does not reflect speech produced in communicative settings. Broader information on the interaction between cognitive load, speech production and visual information would also help establish how communication in clients with stroke may differ from an age-appropriate norm.

Adult social care and charity sectors: Social workers responsible for assessing the needs of elderly clients need to consider their ability to communicate effectively as this is an important component of wellbeing. A better understanding of which factors (hearing status, vision, cognitive abilities) seem to have the most influence on communication ability would be important in terms of attracting attention to the needs of older clients for maintaining effective communication and deciding on the provision of appropriate aids and advice for those in regular contact with the elderly client. Some of the charities dealing with the welfare of older adults provide guidance about effective communication (e.g. Alzheimer Society, Sense UK) so further knowledge about the communication in the 'healthy aged' could be used to refine the advice given in this area.

Developers of speech technology: Speech technology applications aimed at older users are likely to increase in coming years, as they can be used as a way to maintain communication remotely, for example, to carry out regular medical monitoring (e.g. of sugar levels, blood pressure) via voice input (e.g. Siri or similar systems) or for remote control of devices in the home. The automatic recognition of the speech of older speakers is challenging due to weak phonation and increased within-speaker variability. Knowledge of the way in which speech of older speakers varies acoustically from that of younger speakers could help adapt ASR devices for use for speech by older users.

Wider public: Given population demographics, most adults in the general public have relatives who are elderly or are themselves within this population, and will likely be experiencing difficulties with communication at times. The effect of ageing on hearing is quite well known by the general public but there is probably a lower degree of public awareness on the effects of ageing on the ability to produce speech clearly and on how effects linked to cognitive processing, such as the complexity of task demands or short-term memory may impact on the ability to speak clearly, especially in challenging situations.