Page 16 - The Modul of Psycholinguistics Studies_2

4) Perceptual constancy and normalization

Figure 3: The left panel shows the 3 peripheral American English vowels
/i/, /ɑ/, and /u/ in a standard F1 by F2 plot (in Hz). The mismatch
between male, female, and child values is apparent. In the right panel
formant distances (in Bark) rather than absolute values are plotted using
the normalization procedure proposed by Syrdal and Gopal in 1986.
Formant values are taken from Hillenbrand et al. (1993)

Despite the great variety of different speakers and
different conditions, listeners perceive vowels and
consonants as constant categories. It has been proposed

that this is achieved by means of the perceptual
normalization process in which listeners filter out the

noise (i.e. variation) to arrive at the underlying category.
Vocal tract size differences result in formant frequency
variation across speakers; therefore a listener has to

adjust his/her perceptual system to the acoustic
characteristics of a particular speaker. This may be

accomplished by considering the ratios of formants rather
than their absolute values. This process has been called
vocal tract normalization (see Figure 3 for an example).

Similarly, listeners are believed to adjust the perception
of duration to the current tempo of the speech they are

16 | Fatma Yuniarti, M.Pd., B.I