Ivan Magrin-Chagnolleau, Jean-François Bonastre and Frédéric Bimbot.
Effect of Utterance Duration and Phonetic Content on Speaker Identification
using Second-Order Statistical Methods.
Proceedings of EUROSPEECH 95, Vol. 1, pp. 337-340, Madrid, Spain, September 1995.

Abstract: Second-order statistical methods show very good results for
automatic speaker identification in controlled recording conditions. These
approaches are generally used on the entire speech material available. In
this paper, we study the influence of the content of the test speech material
on the performances of such methods, i.e. under a more analytical approach.
The goal is to investigate on the kind of information which is used by these
methods, and where it is located in the speech signal. Liquids and glides
together, vowels, and more particularly nasal vowels and nasal consonants,
are found to be particularly speaker specific: test utterances of 1 second,
composed in majority of acoustic material from one of these classes provide
better speaker identification results than phonetically balanced test
utterances, even though the training is done, in both cases, with 15 seconds
of phonetically balanced speech. Nevertheless, results with other phoneme
classes are never dramatically poor. These results tend to show that the
speaker-dependent information captured by long-term second-order statistics 
is consistently common to all phonetic classes, and that the homogeneity of
the test material may improve the quality of the estimates.