| Volume
7, number 2 (December 2000)
Contents
Full Text
Hermann J. Künzel
Effects of voice
disguise on speaking
Patterns of voice
disguise in forensic cases involving speaker identification or
speaker profiling may contain clues to features of the undisguised
voice of a speaker. In a longitudinal and synchronous study, 100
subjects were asked to read a text on five occasions during a
period of six months, first using their normal voices, and
subsequently with two out of three modes of voice disguise, (1)
raising fundamental frequency, (2) lowering fundamental frequency,
(3) denasalization by firmly pinching their nose. The focus of
this investigation is on fundamental frequency (F0). Results show
that most subjects were in fact able consistently to change their
F0 according to the mode of disguise they had selected. However,
there were differences between both sexes with regard to their
preference of disguise modes as well as to the individual
articulatory ‘strategies’ which they employed to implement
them. Results corroborate experience with forensic casework, that
is, they show that there is a constant relation between the F0 of
a speaker’s natural speech behaviour and the kind of disguise he
will use in an incriminating phone call. Speakers with
higher-than-average F0 tend to increase their F0 levels. This
process may or may not involve register changes from modal voice
to falsetto. Speakers with lower-than-average F0 prefer to
disguise their voices by lowering F0 even more and often end up
with permanently creaky voice. The latter trend can be observed
much more clearly in males. Females are generally more reluctant
to make drastic changes to their fundamental frequency patterns.
Full Text
Paul Foulkes
and Anthony Barron
Telephone speaker
recognition amongst members of a close social network
This article presents
results from a speaker recognition task carried out by a
close-knit network of speakers (university friends who have lived
in shared accommodation with each other for two years). Ten male
speakers recorded a scripted message on to an answer machine via a
mobile telephone. Two foil speakers from outside the network were
also recorded. Samples of between 8 and 10 seconds were extracted
from all twelve recordings, and used as stimuli for an open
speaker recognition test performed by the network members.
Listeners varied widely in their performance, and one listener
failed to recognize his own voice. Some of the voices were easy to
identify, but several speakers were consistently misidentified,
and one speaker was particularly hard to identify. Both of the
foil speakers were sometimes mistaken for network members.
Auditory analysis of the voices shows, as expected, that speakers
with the most distinctive regional accents and other idiosyncratic
features were the most consistently identified. Acoustic analysis
of F0 was also undertaken. It was found that the speakers who were
most consistently identified were those with relatively high and
low mean F0 values, as well as those with the widest and narrowest
overall F0 range. Speakers with average pitch values and ranges in
the middle of the overall group values proved harder to identify.
The findings support the view that average pitch is a robust
diagnostic of speaker identity, not only for forensic
phoneticians, but also for naïve listeners. They furthermore
demonstrate that naïve speaker recognition, even among
members of a close-knit social network, is not a task which can be
achieved infallibly.
Full Text
Harry Hollien
and Reva Schwartz
Aural-perceptual
speaker identification:
The degree to which
speech and/or speech samples are noncontemporary is considered
important to the speaker identification process. There are two
dimensions to the problem; the first relates to the listener and,
especially, to earwitness lineups. Here, the subject or witness is
asked to make identifications at various times after having heard
(but not having seen, of course) the speaker. It has been found
that a person’s memory for a voice decays over time. In the
second case, it is the samples of the speaker’s utterances which
are temporally displaced. The prevailing opinion here has been
that the use of non-contemporary speech samples poses just as
difficult a challenge to the speaker identification process as
does the decaying memory of a witness. Accordingly, research was
carried out to test this possibility (Hollien and Schwartz, in
press); it was found that the overall drop in correct
identification over latencies from four weeks to six years was
only about 15–25 per cent. It was not until the greatest of the
time separations was studied (i.e., twenty years) that a
substantial drop occurred (to 31 per cent). At this juncture, a
number of questions arose; and three of them have been
investigated. First, is listener gender important to the process;
second, are the identification levels affected by the type of
listeners employed and, finally, can external factors serve to
differentially degrade listener performance? It was found that the
first question could be answered in the negative and the second
two in the affirmative. These findings should aid in clarifying
some of the relationship between sample latency and identification
accuracy.
Full Text
Susan
Berk-Seligson
Interpreting for
the police: issues in pre-trial phases of the judicial process
During the
investigative phase of the judicial process, interpreting for
those who do not speak the language of the courts is often carried
out either by bilingual police officers and other employees of the
police department, or by relatives and friends of suspects or
detainees. In any of these cases, the norms of professional court
interpreting can easily be violated. A review of appellate cases
coming from California, Florida and New York reveals that when the
police make use of unqualified interpreters during their
investigative interviews or interrogations, frequently the Miranda
rights of detainees are jeopardized. Issues of hearsay also arise
in such cases. The use of ad hoc interpreters in police
investigative work is questioned by the author.
Full Text
Christophe
Champod and Ian W. Evett
Commentary on A.
P. A. Broeders (1999) ‘Some observations on the use of
probability scales in forensic identification’, Forensic
Linguistics, 6(2): 228–41
Full Text
Dennis Kurzon
The right to
understand the right of silence: a few comments. (A commentary on
discussions on the right of silence which appeared in issue 7(1))
Full Text
Book Reviews
Book Reviews
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User: WEIMING LIU
Session: 18888
Forensic Linguistics
is published by the University of Birmingham Press.
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