The
value of some features of single phoneme is predictable or redundant due to the
specification of the other features of that segment. That is, given the
precence of certain values, one cen predict the value of other features in that
segment.
In
English, all nasal consonant phonemes are predictably voiced. Thus voicing is
non-distinctive for nasal consonants and need to be specified in marking the
value of the voicing feature for this set of phonemes. Phonetically in English,
the nasal phonemes may be voiceless (indicated by a small ring under the
symbol) when they occur after a syllable initial /s/ as in snoop, which
phonemically is /snup/ and phonetically may be [snup]. The devoicing is,
however, predictable from the context.
This
can be accounted for at the phonemic level by the following :
Redundancy
rule : if a phoneme is [+ nasal} it is also [ + voiced] In burmese, however, we
find the following minimal pairs:
Note
that the value of the voicing feature is left blank for the English phoneme /m/
since the [+] value for this feature is specified by the redundancy rule given
above.
As
noted earlier, the value of some features in a segment is predictable because
of the segments that that precede of follow; the phonological context
determines the value of the feature rather than the presence of other feature
values in that segment. Aspiration cannot be predicted in isolation but only
when a voiceless stop occur in a word, since the presence of absence of the
feature depends on where the voiceless stop occurs and what precedes or follows
it. It is determined by its phonemic environment. Similarly, the oral or nasal
quality of a vowel depends on its environment. If it is followed by a nasal
consonant it is predictably [+ nasal].
For
certain classes of sounds, the values of some features are universally implied
for a languages. Thus all stops ([-continuant] segments) are universally and
predictably [- syllabic], regardless of their phonemic context.
