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SUMMARY:Voice quality and forensic speaker identification - Professor Fran
 cis Nolan\, Department of Linguistics
DTSTART:20080115T160000Z
DTEND:20080115T173000Z
UID:TALK10176@talks.cam.ac.uk
CONTACT:Caroline Williams
DESCRIPTION:When phoneticians compare forensic speech samples they often r
 emark in their reports on a ‘similarity of voice quality’. Likewise\, 
 when earwitnesses are asked to describe a voice they have heard\, they wil
 l normally comment on the accent\, if they are able to\, and additionally 
 describe what they heard as an ‘X voice’ where ‘X’ is a term such 
 as\n‘rough’ or ‘resonant’ that can be seen as an informal label of
  voice quality. In this talk I will examine these two main categories of f
 orensic speaker identification – by phonetic experts and by earwitnesses
  – with reference to the notion of voice quality. I will take voice qual
 ity in the broad sense discussed by Laver in his The Phonetic Description 
 of Voice Quality (CUP\, 1980)\, that is\, as covering supralaryngeal as we
 ll as laryngeal characteristics which emerge cumulatively from a person’
 s speech.\n\nIn speaker comparison by phonetic experts the emphasis in aco
 ustic analysis tends to be on segmental properties\, or on pitch-related l
 ong-term features. I will give some examples of how speakers can be differ
 entiated in this way\, and touch on how the dynamics of formants in transi
 tional parts of the speech signal may provide the nearest we have\nto a sp
 eaker’s ‘signature’. Beyond segmental analysis\, however\, I will sh
 ow that an analysis using the long-term distributions of formant frequenci
 es can capture information relating to Laver’s supralaryngeal voice qual
 ity categories. Given the availability of Laver’s\ncomprehensive framewo
 rk for the impressionistic analysis of voice quality we might ask why\, in
  the auditory strand of their forensic analyses\, phoneticians have made l
 ittle use of systematic voice quality description\, and I will explain why
  I think that is.\n\nAs regards earwitness evidence I will focus on the de
 scription of voices by earwitnesses\, and on the use of voice parades. I w
 ill ask whether an earwitness’s description of a voice might be improved
  if questioning of\nthe witness were informed and structured by knowledge 
 of a framework for voice quality description. And in creating a voice para
 de\, I will show how pre-tests are used to ensure that the parade is fair\
 , including one where experimental subjects are\, in effect\, asked to rat
 e the similarity\nin voice quality between all pairs of samples to be used
  in the parade. This is to ensure that the suspect is not an outlier. Fina
 lly I will preview a project which will investigate the effect of the tele
 phone on\nsuch similarity judgments.
LOCATION:GR-06/07\, English Faculty Building
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