Page 14 - The Modul of Psycholinguistics Studies_2

Figure 2 for an example). Speech sounds do not strictly follow
one another, rather, they overlap. A speech sound is influenced

by the ones that precede and the ones that follow. This influence
can even be exerted at a distance of two or more segments (and

across syllable- and word-boundaries).
Because the speech signal is not linear, there is a problem
of segmentation. It is difficult to delimit a stretch of speech

signal as belonging to a single perceptual unit. As an example,
the acoustic properties of the phoneme /d/ will depend on the
production of the following vowel (because of coarticulation).

b. Lack of invariance
Study of speech perception must deal with several
problems which result from what has been termed the lack of

invariance. Reliable constant relations between a phoneme of a
language and its acoustic manifestation in speech are difficult to
find. There are several reasons for this:

1) Context-induced variation
Phonetic environment affects the acoustic

properties of speech sounds. For example, /u/ in English
is fronted when surrounded by coronal consonants. Or,
the voice onset time marking the boundary between

voiced and voiceless plosives are different for labial,
alveolar and velar plosives and they shift under stress or

depending on the position within a syllable.
2) Variation due to differing speech conditions
One of important factor that causes variation is

differing speech rate. Many phonemic contrasts are
constituted by temporal characteristics (short vs. long

vowels or consonants, affricates vs. fricatives, plosives vs.
14 | Fatma Yuniarti, M.Pd., B.I