This is the tone that is usually regarded as more or less neutral. If someone is asked a question and the reply is yes or no, it will be understood that the question is now answered and that there is nothing more to be said. Thus the falling tone gives an impression of finality.
The term accentual refers to accent. Some writers attach the word accent to stress. When it is said that intonation has accentual function, it implies that the placement of stress is somewhat determined by intonation.
1-The most common position for the placement of tonic syllable is the last lexical word (nouns, adjectives, words, adverbs) and not the functional words. For contrastive purpose, however any word may become the bearer of tonic syllable.
The listener is better able to recognize the grammar and syntax structure of what is being said by using the information contained in the intonation. For example such things as
a- The placement of boundaries between phrases, clauses and sentences.
b- The difference between questions and statements.
Grammatical function performed by tone boundaries
Grammatical intonation is used in those sentences which when written are ambiguous, and whose ambiguities can only be removed by using differences of intonation. In the following example the difference caused by the placement of tone-unit boundaries causes two different interpretations of sentence.
Another grammatical function of intonation is the choice of tone on the tonic syllable. For example rising tone is used with questions. Simply by changing the tone from falling to raising the possibility of changing a statement to question is created.
Intonation can signal to the listener what is to be taken as “new” information and what is already “given”. It can indicate when the speaker is indicating some sort of contrast or link with material in another tone unit. In conversation it can convey to the listener what kind of response is being expected from him.
Sometimes the stress is placed on syllables in terms of “information content”. The more predictable a words occurrence in a given sentence, the lower its information content will be. Tonic stress will be placed on words with high information content.
The mentioned outlined intonation patterns are certainly not obligatory. The risk with these approaches is that one might end up making generalizations that are too broad and will have little power to predict with accuracy the intonation that a speaker will use in a particular context. Moreover generalizations like these are very broad and foreign learners do not find it easy to learn to use intonation through studying them. An intonation function is perhaps the most controversial topic relating phonetics and so it is not possible to draw any definite sketch regarding it.