Abstract
This thesis discusses what is meant by "phonetic quality" in so far as vowel sounds are concerned. The first chapter points out
that phoneticians implicitly describe speech sounds in two different
ways firstly in terns of phonetic quality which is in practice
the attributes of a sound -which convey information by virtue of being
part of a socio-linguistic code; and secondly in terms of their
personal quality, which consists of the attributes that convey
information only about the speaker considered as an individual.
The second chapter discusses, the historical development of our
present descriptions of the phonetic quality of vowels. It is
suggested that not only is there very little evidence for the
traditional articulatory descriptions, but also that the acoustic
descriptions of vowels in tens of their formants have never been
shown to be adequate for all vowels.
The third chapter describes the collection and spectrographic
analysis of a large number of sets of cardinal vowels spoken by
twelve phoneticians. It appears that no precise .statements about
the acoustic correlates of phonetic quality can be made; but it
is probable that vowels such as [e, ɛ, a,ɑ] are best specified
in terms of the relation between the pitches of their first
two formants and the pitches of the first two formants. of other vowels
of this general type spoken by the same speaker. This is not
true of vowels such as [i, u, o, ɔ]. These vowels often cannot
be conveniently analysed as having two or three formants; nor,
even when a procrustean formant specification is possible, are
they adequately specified in terms of formant frequencies (or
pitches). An illustration is given of a pair of vowels
spoken by one speaker in which the frequencies of the first three
formants are almost identical, but which are nevertheless heard
as having quite different qualities (viz. [ɔ] and [o]) , probably
because their formant bandwidths are very different.
In chapter four it is shown that in so far as a formant
frequency specification is adequate, it is the relative and not
the n. salute values of the formant frequencies which convey
linguistic information. In an experiment using synthetic speech
it was found that the same test sound was identified in
different way when it was preceded by different versions of an
introductory sentence.
Chapter five discusses the psychological mechanism responsible
for this process. It is suggested that previous theories accounting
for similar processes are not fully adequate, in that they incorrectly
consider a subject's adaptation tJ a series of stimuli to be
independent of the response which he makes to the stimuli.
The sixth chapter discusses an experiment in which 18 phoneticians
specified the vowels in ten words in a language which was unknown
to them in terms of a standardised cardinal vowel diagram.. It is
shown that among. phoneticians trained in the use of the cardinal
vowel system, there is often a high degree of agreement in the
dpecification- of a vowel which has á degree of lip rounding' similar
to that of the nearest cardinal vowel; but many disagreements occur
in the specifications of vowels with less familiar lip positions.
Nevertheless it is concluded that, in view of the results
detailed in the previous chapters, at present the best method of
specifying many vowels is in terms of the traditional cardinal
vowel system,
