The use and utility of localised speech forms in determining identity: forensic and sociophonetic perspectives

The project aims to investigate variation in accents of English across Northeast England. We focus on the speech of working-class people from Newcastle, Sunderland and Middlesbrough. It is well established that these accents differ significantly from one another, but it is less clear what particular pronunciations lead listeners to group the varieties as one accent (typically, 'Geordie'). The project seeks to identify specific features that cause the accents to be classed together, such that they are heard to be distinct from other accents of northern Britain. Simultaneously, we will ascertain what sounds listeners use to classify speakers into subgroups, e.g. from Newcastle versus Sunderland. The role of socio-economic class is of key importance here. The localised patterns that allow listeners to assign speakers to one group or another are, according to the literature, traditionally associated with speakers from lower socio-economic groups, i.e. the 'working class'. However, in this project we ask whether clear differences exist between the speech of working-class speakers who routinely travel for work or leisure and that of economically marginal individuals we might label 'never worked/long-term unemployed'. Plentiful sociological research on this social divide exists, but how it impacts on people's speech has not yet been investigated systematically. We will also take gender and age differences into account, and assess the data for signs of sound change. It has been shown that greater mobility promotes linguistic uniformity through convergence of speech habits, while limited mobility has the opposite effect. We therefore predict that more mobile members of our sample would converge linguistically over time and across the three localities, while the economically marginal groups in each place would become more divergent.
The project's second strand concerns speech variation at the level of the individual rather than the group or community. This is particularly relevant in the forensic domain, wherein individual identity is crucial. In criminal investigations, forensic speech analysts perform two main tasks. The first, speaker profiling, involves attempting to specify the geographical and social origins of an unknown speaker from a recorded sample of his/her speech, so as to assist the police in identifying potential suspects. The task requires detailed, up-to-date information about the speech of the community/ies to which the unknown speaker may belong. Given its focus on the identification of highly localised speech forms, the corpus produced by the proposed project will satisfy those requirements. The second forensic task is speaker comparison. Here, the expert compares two speech samples, and assesses the likelihood that they were produced by the same or different speakers. Increasingly, this is done in an automated way, using software that extracts information about the acoustic properties of the recordings. The level of similarity between the two samples is evaluated in the context of a relevant 'background population' of recordings of speakers with the same or similar accents. This yields a measure of the samples' typicality. The problem with this approach is that ideally one ought to collect a new corpus for every case, which is likely to be prohibitively expensive. It would be advantageous, therefore, if acoustic parameters in the speech signal which are relatively insensitive to accent variation could be identified. The proposed project tests whether this is possible by combining the Northeast recordings with those from an existing corpus of a markedly different accent (Standard Southern British English). If the approach proves legitimate, its practical value to the forensic speech analysis community would be considerable.
Findings emerging from this two-stranded project will therefore benefit the relevant academic communities as well as having significant applied utility in the field of forensic speech science.

The impact strategy of the project is integral to the project's design, in that we have brought together a steering group of potential end users who will advise on how to optimise the benefits of the project's findings to relevant non-academic audiences. The steering group will include a senior member of the judiciary and a Forensic Audio Specialist from the Metropolitan Police Service. Their role will be to incorporate a non-academic end user's perspective into the design and execution of the project, so as to yield the greatest possible impact among the target communities (police forces, criminal lawyers, judges, and specialists in other branches of the forensic sciences). We will also ensure that awareness of the project's findings is raised among employees of governmental and commercial forensic laboratories, security agencies and software companies. These communities will benefit from the research in the following ways. The research will help to develop understanding among end users of the uses and limitations of automatic speech recognition systems, and the statistical models upon which they depend for the determination of speaker identity. Should our hypothesis be proved correct - that bespoke background population data for every speaker comparison case need not be collected because existing corpora may legitimately be used - the savings in terms of time, cost and effort will be considerable. This would clearly constitute a major benefit.

On the basis of our prior experience, we know that there is a high level of interest among the general public in matters relating to accent variation and speaker identity. We will therefore seek to engage with members of the public, special interest groups (e.g. dialect societies), and schools/colleges through offering talks and workshops tailored specifically to the needs and interests of the audience. The availability of up-to-date data on local pronunciations will also be of great value to speech and language therapists in the region, and we will liaise with representatives of this profession through our connections with the Speech and Language Therapy unit at Newcastle University.

The majority of our dissemination activities designed to achieve maximum impact will naturally take place towards the end of the project, and after it, but we understand how important it is to have end-user input from the outset. To this extent, the incorporation of the steering group will help to guide the process by which we can optimise the impact of the project's findings beyond the academic community.