The perception of speaker sex depends on the listener's integration of a complex range of factors. These may relate, for example, to the style of delivery, the use of particular language, pronunciation (Trudgill, 1983; Smith, 1979), the use of particular intonation patterns (McConnell-Ginet, 1983) and the perceived pitch of the speaker (Aronovitch, 1976, Elyan, 1978; Lass et al., 1976). Some acoustic-phonetic investigations have explored through instrumental analysis how speaker sex differences are perceived. These have shown that acoustic phonetic differences exist between the read speech of men and women speakers. It has been demonstrated that fundamental frequency differences exist between men and women, with men having on average, lower fundamental frequencies (Aronovitch, 1976; Coleman, 1973a). This can be explained in part by their larger larynges. However it is also acknowledged that it is not a low overall average fundamental frequency alone that contributes to the perception of an adult male voice. Some evidence shows for example that use of a wider pitch range will contribute to the perception of femininity, even where the overall pitch is low (Terrango, 1966). In addition women have been found to have on average higher formant frequencies (Coleman, 1976; Henton, 1986; Peterson & Barney, 1952; Childers & Wu, 1991; Wu & Childers, 1991) as a result of the smaller vocal tract. Women have different glottal source characteristics (Karlsson, 1989) which are reflected in the filter characteristics of the speech signal (Klatt & Klatt, 1990). There is also some evidence to suggest that other speaker sex differences exist in the temporal domain. Byrd (1992) found differences between men and women speakers in speaking rate in read speech in American English in the TIMIT database. Byrd states that under the recording conditions used for the TIMIT database, women spoke appreciably more slowly than the men and that men tended to reduce vowels to schwa ([ə]) more often than the women. Byrd also found that female speakers in the TIMIT database released stops in sentence-final position more frequently and produced more glottal stops than male speakers. All these findings were statistically significant.