Improving the Consistency of Formant Measurement


  • Martin Duckworth Duckworth Consultancy Ltd
  • Kirsty McDougall University of Cambridge
  • Gea de Jong Forensic Research Associates
  • Linda Shockey University of Reading



formant frequencies, formant measurement, inter-analyst reliability, forensic phonetic evidence, forensic phonetic report-writing


This study examines the inter-analyst robustness of formant frequency (F) measurements before and after agreeing a common measurement procedure. Three laboratories used the latest available version of the same formant extraction software to extract F1, F2 and F3 values from the same sets of high quality audio recordings of six repetitions of read utterances containing six target monophthongs, /i?, æ, ??, ??, ?, u?/. The subjects were two sets of twenty British males with a similar accent profile. Results are presented which show the extent to which analyst, methodology, vowel, and speaker affect the consistency of the values extracted. Agreeing the methodology reduced the extent of variation among the results from the three laboratories as might be expected. However, there remained some differences and even occasionally a greater disparity among the measurements. The paper suggests sources of these differences and makes proposals for a consistent logging of settings and times used when extracting F values. Further, it recommends that practitioners aim to establish an agreed protocol for forensic analysis of formants to facilitate the validation of evidence.

Author Biographies

Martin Duckworth, Duckworth Consultancy Ltd

Martin Duckworth is the director of Duckworth Consultancy. He has an MA in Phonetics and Linguistics from the University of Essex. He became a founder member of IAFPA and since 1993 he has been consulted on issues of forensic speech analysis and undertakes mainly forensic speaker comparison work. His research interests include exploring rate and fluency in conversational speech, and the improvement of measurement and recording of forensic findings.

Kirsty McDougall, University of Cambridge

Kirsty McDougall is a British Academy Postdoctoral Fellow in the Department of Linguistics, University of Cambridge, having previously worked as a Research Associate on the forensic phonetic projects DyViS and VoiceSim. She has a B.A. in linguistics and a B.Sc. in mathematics and statistics from the University of Melbourne, and an M.Phil. and Ph.D. in linguistics from the University of Cambridge. Her research interests include speaker characteristics, theories of speech production, and phonetic realisation of varieties of English. She is a member of IAFPA

Gea de Jong, Forensic Research Associates

Gea de Jong is the Director of Forensic Research Associates: since 1994 she has been consulted on issues of forensic speech and language analysis, including voice comparison and voice parades. She was a senior research associate in the Department of Linguistics, University of Cambridge where she worked on the DyViS project. Her M.Phil. degree was in Computer Speech and Language Processing from the University of Cambridge. She has a Ph.D. in Linguistics from the University of Florida. She is a member of IAFPA.

Linda Shockey, University of Reading

Linda Shockey is a Lecturer in the Department of Applied Linguistics at the University of Reading. She holds a PhD from the Ohio State University (Columbus, Ohio). She specialises in acoustic and articulatory phonetics and aspects of phonology. She is a member of IAFPA.



How to Cite

Duckworth, M., McDougall, K., de Jong, G., & Shockey, L. (2011). Improving the Consistency of Formant Measurement. International Journal of Speech, Language and the Law, 18(1), 35–51.




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