Speech sounds are defined by distinctive phonetic properties or features that, when combined, distinguish these sounds from each other. We use the features [-syll, -cont, +ant, +cor, -vce] to represent the phoneme /t/. If any feature is altered, /t/ is no longer /t/, but a combination of the altered features. For example, changing [-vce] to [+vce] yields /d/. These are distinctive features. On the other hand, the features that are predictable when describing a sound are referred to as redundant.
Redundancy refers to the predictability of a certain feature due to the fact that its presence guarantees the presence of another feature. For instance, when describing an aspirated plosive in Standard English, it would be redundant to use the feature [-vce] since only [-vce] plosives can be aspirated. Likewise, vowels are not specified for [+vce] since these sounds are always underlyingly voiced.
Features that are redundant (that is, whose values are predictable) are also referred to as underspecified. In other words, when all phonemes of a given class (ex: nasals) must be specified for a given feature, e.g., [+vce], we say that this class is underspecified for that feature. All nasals in English are [+vce], so we say that they are underspecified for [-vce].
Underspecificity can be either language-specific or universal. Place of articulation underspecificity for affricates in English is language-specific (all affricates are palato-alveolar) since langauges exists that display alveolar affricates as well. Universal underspecificity, however, is cross-linguistic. Vowel classes in all languages are underspecified for [+vce].
Redundancy Rules are used to simplify the description of phonemes when building natural classes by expressing binary (+/-) specifications of certain features. These rules predict the distribution of these features. Redundancy rules are presented in an ‘if X then Y’ format.
Not all languages display the same redundancy rules. This means that certain features may be omitted in the phonemic representation (underlying representation) of a phoneme. In any given language there is a default value for most phonemes based on the binary distribution of its features. Consider, again, nasals in Standard English, which are underspecified for [+vce].
vowels are voiced[+syll, -cons] –> [+vce]
However nasals in Khonoma Angami show contrast for voiced and voiceless nasal. Thus the redundancy rule for English will not apply to Khonoma Angami since not all nasals are voiced.
Below are examples of formalized universal redundancy rules.
- [+son] -> [+vce]
- sonorants are voiced
- [-cons] -> [+cont]
- vowels and glides are continuants
- [-syll, -cons] -> [+high]
- glides are high
Here are examples for Standard American English.
- [+lat] -> [+cor, +ant]
- laterals are alveolar
- [-cont, +del rel, +dist] -> [+cor, +dors]
- affricates are palato-alveolar
- [+syll, -cons, -back] -> [-round]
- front vowels are unrounded
- [+syll, -cons, +low] -> [-round]
- low vowels are unrounded
Redundancy is not an easy concept to grasp initially however taking the time to master this information will yield strong results in assignments and analyses.