Assessing the effects of accent-mismatched reference population databases on the performance of an automatic speaker recognition system


  • Dominic Watt University of York
  • Philip Harrison University of York
  • Vincent Hughes University of York
  • Peter French University of York
  • Carmen Llamas University of York
  • Almut Braun Bundeskriminalamt (BKA)
  • Duncan Robertson University of York



Forensic phonetics, automatic speaker recognition, speech technology, forensic speaker comparison


Automatic Speaker Recognition (ASR) systems are designed to provide the user with statistics relating to the similarity of two or more speech samples and to the typicality of those shared features in the wider population. When an ASR system is used as part of a forensic investigation, the user must decide what counts as the appropriate ‘wider population’ and select a reference database accordingly. While it has generally been held that the voices populating the reference database should be similar in accent to that of the samples under consideration, the degree to which the accents should correspond has until now not been investigated empirically. We report in this article on a study in which the composition of the reference database was systematically varied in terms of accent, using corpora of samples of Standard Southern British English and of three subvarieties spoken in North-East England (Newcastle, Sunderland, Middlesbrough).

Author Biographies

Dominic Watt, University of York

Dominic Watt is Senior Lecturer in Forensic Speech Science at the University of York, UK. His research interests include forensic linguistics and phonetics, speech perception, sociophonetics, dialectology, and language and identity studies. He was Co-Investigator on the UK Economic and Social Research Council-funded projects  'The  Use  and  Utility  of  Localised  Speech  Forms  in  Determining  Identity:  Forensic and Sociophonetic Perspectives' (2016–19, ES/M010783/1) and 'Accent Bias and Fair Access in Britain' (2017–20, ES/P007767/1). He is co-editor of The Handbook of Dialectology (Wiley, 2018) and, with Carmen Llamas, Language and Identities (Edinburgh University Press, 2010). He undertakes occasional forensic casework on behalf of JP French Associates, York.

Philip Harrison, University of York

Philip Harrison is a forensic consultant and company director, specialising in the areas of acoustics, phonetics and the analysis of evidential recordings. He has worked at J P French Associates since 1997 and has expertise in authentication, enhancement, transcription and speaker comparison. He is also active in carrying out research in the fields of forensic speech and audio analysis: in the efficacy of acoustic analysis software, measuring the performance of biometric systems and evaluating methods for expressing the strength of forensic speech evidence. He is playing a key role in developing quality standards in the field in conjunction with the UK Forensic Science Regulator, and teaches technical aspects of forensic speech science at the University of York.

Vincent Hughes, University of York

Vincent Hughes is Lecturer in Forensic Speech Science at the University of York, UK. His research interests lie in forensic speech science, phonetics, phonology, sociophonetics and sociolinguistics. His current research focuses on understanding the bases and limitations of individual speaker characterisation and the relative contribution of acoustic, auditory and biological information. He is also interested in the application of the numerical likelihood ratio framework to the evaluation of speech evidence in forensic voice comparison cases. His doctoral research considered how the definition of the relevant population with regard to regional and social dimensions of variability and sample size affects the numerical estimation of the strength of evidence.

Peter French, University of York

Peter French is Professor of Forensic Speech Science in the Department of Language and Linguistic Science at the University of York, UK, Visiting Professor of the same subject in the Department of Modern Languages and Linguistics at the University of Huddersfield, UK, Company Chairman of J P French Associates Forensic Speech and Acoustics Laboratory, and President of the International Association for Forensic Phonetics and Acoustics.

Carmen Llamas, University of York

Carmen Llamas is Senior Lecturer in Sociolinguistics at the University of York, UK. She is Principal Investigator on ‘The Use and Utility of Localised Speech Forms in Determining Identity: Forensic and Sociophonetic Perspectives’ (TUULS) project. She is co-author, with Joan Beal and Lourdes Burbano-Elizondo, of Urban North-Eastern English: Tyneside to Teesside (Edinburgh University Press, 2012), and co-editor (with Dominic Watt) of Language and Identities and Language, Borders and Identity (Edinburgh University Press 2010, 2014). She is also co-editor of The Routledge Companion to Sociolinguistics, with Louise Mullany and Peter Stockwell (Routledge, 2007).

Almut Braun, Bundeskriminalamt (BKA)

Almut Braun was Postdoctoral Research Associate on the TUULS project at the University of York, UK, between 2016 and 2019. In November 2015, she completed her doctoral research entitled ‘The speaker identification ability of blind and sighted listeners – an empirical investigation’ (Philipps-Universität Marburg, Germany). She holds an MA in German Philology, Phonetics and Linguistic Engineering. Since March 2020 she has been employed as a forensic speech and audio analyst by the Federal Criminal Police Office (Bundeskriminalamt, BKA) in Wiesbaden, Germany.

Duncan Robertson, University of York

Duncan Robertson was Postdoctoral Research Associate on the TUULS project at the University of York, UK, between 2016 and 2019. He completed his doctoral research at the University of Glasgow in 2015, investigating implicit and explicit associations towards different social accents of English. He is now employed by the UK's Office of Qualifications and Examinations Regulation (Ofqual) as a data analyst.


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How to Cite

Watt, D., Harrison, P., Hughes, V., French, P., Llamas, C., Braun, A., & Robertson, D. (2020). Assessing the effects of accent-mismatched reference population databases on the performance of an automatic speaker recognition system. International Journal of Speech, Language and the Law, 27(1), 1–34.




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