| Volume
9, number 1 (August 2002)
Francis
Nolan
Intonation
in speaker identification: an experiment on pitch alignment
features
ABSTRACT
While long-term fundamental frequency statistics have been shown
to be useful in discriminating speakers, relatively little
attention has been paid in work on speaker characterization to
intonation as a linguistically and phonetically structured
phenomenon. To help redress the balance, this article presents the
results of an experiment on between-speaker differences in
linguistically specified intonational events. An autosegmental-metrical
model of intonation is assumed which uses H (high) and L (low)
targets as its primes. Since the pitch of the events corresponding
to these targets is highly variable due to factors such as
within-speaker variation in pitch range (or ‘pitch span’),
this study investigates as a source of speaker discrimination the
temporal alignment of these intonational events with segmental
events. A limited degree of discrimination is achieved in highly
controlled materials. Of theoretical interest is that definable
pitch events lying between H and L targets show more potential for
betweenspeaker discrimination than the targets themselves.
Full Text
R.Rodman
et al.
Forensic
speaker identification based on spectral moments
ABSTRACT
A new method for doing text-independent speaker identification
geared to forensic situations is presented. By analysing
‘isolexemic’ sequences, the method addresses the issues of
very short criminal exemplars and the need for open-set
identification. An algorithm is given that computes an average
spectral shape of the speech to be analysed for each glottal pulse
period. Each such spectrum is converted to a probability density
function and the first moment (i.e. the mean) and the second
moment about the mean (i.e. the variance) are computed. Sequences
of moment values are used as the basis for extracting variables
that discriminate among speakers. Ten variables are presented all
of which have sufficiently high inter- to intraspeaker variation
to be effective discriminators. A case study comprising a
ten-speaker database, and ten unknown speakers, is presented. A
discriminant analysis is performed and the statistical
measurements that result suggest that the method is potentially
effective. The report represents work in progress.
Full Text
Gea
de Jong and Terry Honess
The
perception of speed-modified recordings
ABSTRACT
The overall quality of audio tapes may be affected by such factors
as background noise and the intensity of the signal, or whether
the recording was made at the correct speed. The last would affect
the speaking fundamental frequency (SFF), and therefore perceived
pitch, and phonetic characteristics of the speech sample.
Listeners’ skills regarding the recognition of recording speeds
that had been manipulated are investigated here. It was found that
a majority of correct identifications of speed manipulation is
only achieved when the speed is –6% or +6% off the correct speed
in an experimental procedure that compared deviations of 3, 6 and
9%. Judging samples that are played at higher speeds is easier
than those played at lower speeds. Expert listeners did not
perform any better than naive or trained listeners. However, they
were more cautious and were more often correct when very confident
about their judgments.
Full Text
Gea
de Jong, Paul Newis† and John Hunt
The
effects of repeated copying and recording media on intelligibility
The
increasing use of MiniDisc technology for audio harvesting by law
enforcement agencies gives some cause for concern. The reasons for
its use are understandable: the kit is small, cheap, light and
easy to use. However, there are disadvantages when compared to
some of the existing technologies, due to the use of bit reduction
techniques. In order to demonstrate the potential problems
associated with MiniDisc technology, a two-factor design
experiment was set up in which listeners were asked to listen to
representative lists of words, contaminated with speech babble.
The two factors of interest were (1) type of medium (e.g. analogue
tape, MiniDisc) and (2) the generation copy. It was found that the
copying process of MiniDiscs affects the quality of the signal in
an unpredictable manner: it could improve but also deteriorate the
signal. Quality could be deteriorated but intelligibility could
have improved. The effects of different types of MiniDisc
equipment vary due to different compression techniques. In
addition, the superior quality of DAT and the inferior quality of
analogue tapes was confirmed.
Full Text
Francis
Nolan
The
‘telephone effect’ on formants: a response
This
article is a response to Hermann Künzel’s article ‘Beware of
the “telephone effect”: the influence of telephone
transmission on the measurement of formant frequencies’
(Forensic Linguistics 8(1), 80–99). There, he shows convincingly
that the evaluation of formant frequencies, notably F1, is
affected by the band-pass filter effect of telephone transmission.
This response does not question his data, or cast doubt on the
general lesson to be drawn on the need for caution in estimating
formant frequencies from telephone speech, or engage with the
issues of dialectological methodology with which he is in part
concerned, but it does challenge the apparent strength of the
conclusion he draws for forensic speaker identification (FSI). His
conclusion could be read as endorsing a complete exclusion of
formants from the FSI process, and his article will, I fear, be
misinterpreted by some as justification for setting aside a
valuable source of speaker-characterizing acoustic information in
FSI.
Full Text
Hermann
J. Künzel
Rejoinder to Francis Nolan’s ‘The “telephone effect” on
formants: a response’
Full Text
Robert
Rodman
CASE
REPORT: Linguistics and the law: how knowledge of, or ignorance
of, elementary linguistics may affect the dispensing of justice
Ignorance
of elementary linguistic concepts may have a bearing on justice.
This thesis is drawn from the conviction appeal of a Haitian-born
American sentenced to prison for 12 years for dealing cocaine. The
verdict was based in part on a surreptitious recording of the drug
deal. Although the drug dealer on the tape spoke a dialect of
American Black English, and the defendant speaks English with a
Creole accent, the State persuaded the jury that the Haitian
disguised his voice by purposefully dropping his accent. His
ability to perform this feat was attributed in testimony to the
fact that he had been an interpreter for the United States Army in
Haiti, and was therefore a linguist, and therefore understood
‘sound change’, and therefore could disguise his voice by
dropping his foreign accent. This absurd chain of non sequiturs,
and the resulting miscarriage of justice, is the result of
linguistic naiveté, and would not have occurred if the court knew
that an interpreter is not necessarily a linguist, and that sound
change refers to the historical development of languages.
Full Text
A.
P. A. Broeders, Tina Cambier-Langeveld and Jos Vermeulen
CASE REPORT: Obtaining reference material in a case with two
unknown speakers: getting two suspects on speaking terms
Full Text
A.
P. A. Broeders, Tina Cambier-Langeveld and Jos Vermeulen
CASE REPORT: Arranging a voice lineup in a foreign language
Full Text
Michael
Jessen
CONFERENCE REPORT: Annual Meeting of the International Association
for Forensic Phonetics, Paris, 4–6 July 2001
Full Text
PhD
abstracts
Full Text
Book Reviews
Tim Grant, Pamela S. Morgan, Susan Berk-Seligson
Book reviews
Full Text
Forensic Linguistics is published by the University of Birmingham Press.
User: WEIMING LIU
Session: 21555
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