Amalia Todiraºcu * A Unification-Based Model for Speech Generation

Some features of any phoneme depend on the phonetic context in which it occurs. The changes will refer to the place of articulation, voicing, lip position, soft palate position. In some languages (like English), phonemes have different realisations depending on the context. In other languages (like Romanian), phoneme realisation does not depend on the context.

Some common modifications which appear suddenly in the continuous speech are the assimilation and elision. A short example is given below for English and Romanian languages.

Assimilation is the process of replacing a sound by another sound under the influence of a third sound which is near to it in the word or sentence. Assimilation can be progressive, regressive, or double, according to the direction in which the process takes place.

Example: For English, there are some examples of assimilation rules:

1. the phoneme /l/ is assimilated by the preceding phoneme /p/, losing the feature of being voiced. The rule can be expressed by using the model proposed in the following manner:

   

2. the phoneme /z/ is replaced by the phoneme /s/ under the influence of the voiceless phoneme /p/:

   

Elision is defined as the disappearance of a sound. Contextual elisions occur frequently in rapid speaking, when a sound which exists in a word said by itself is dropped in a compound or in a connected phrase.

Example:

In English, when the sequence consonant + /δ/ + /r/ + weak vowel is met, there is a tendency to lose /δ/:

The set of context-dependencies rules for the Romanian language is empty. In Romanian, most of the assimilations occurred in the past, in the transformational process of the language. In a word which contains two intervocalic consonants placed in different syllables, the first one is completely assimilated: cununã < lat. corona.

Some context-sensitive rules can be defined in close relation with morphology. These rules are applied in the flexion of the word.

Example: brad + i [ NR : plural ] => brazi, where /d/ is changed to /z/ in the case of appending a final /i/.

4.2. Accent identification rules

The accent is influenced by four factors: stress, pitch, sound quantity, and sound quality.

Stress is influenced by the content of the word. Words can be classified into functional words and content words. Functional words serve to define the relationship between the other parts of the sentence, and usually do not bear stress. Examples of functional words are: determiners, prepositions, conjunctions, personal pronouns, auxiliaries. The model permits us to treat uniformly the phonological features and the syntactic ones.

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