Aspects of connected speech

Aspects of connected speech

Many years ago scientists tried to develop machines that produced speech from a vocabulary of pre-recorded words; the machines were designed to join these words together to form sentences. For very limited messages, such as those of a "talking clock", this technique was usable, but for other purposes the quality of the speech was so unnatural that it was practically unintelligible. In recent years, developments in computer technology have led to big improvements in this way of producing speech, but the inadequacy of the original "mechanical speech" approach has many lessons to teach us about pronuncia-tion teaching and learning. In looking at connected speech it is useful to bear in mind the difference between the way humans speak and what would be found in "mechanical speech".

Rhythm 

The notion of rhythm involves some noticeable event happening at regular intervals of time; one can detect the rhythm of a heartbeat, of a flashing light or of a piece of music. It has often been claimed that English speech is rhythmical, and that the rhythm is detectable in the regular occurrence of stressed syllables.
Of course, it is not suggested that the timing is as regular as a clock: the regularity of occurrence is only relative. The theory that English has stress-timed rhythm implies that stressed syllables will tend to occur at relatively regular intervals whether they are separated by unstressed syllables or not; this would not be the case in "mechanical speech".
The stress-timed rhythm theory states that the times from each stressed syllable to the next will tend to be the same, irrespective of the number of intervening unstressed syllables. The theory also claims that while some languages (e.g. Russian, Arabic) have stress-timed rhythm similar to that of English, others (e.g. French, Telugu, Yoruba) have a different rhythmical structure called syllable-timed rhythm; in these languages, all syllables, whether stressed or unstressed, tend to occur at regular time intervals and the  time between stressed syllables will be shorter or longer in proportion to the number of unstressed syllables.
Some writers have developed theories of English rhythm in which a unit of rhythm, the foot, is used (with a parallel in the metrical analysis of verse).
The foot begins with a stressed syllable and includes all following unstressed syllables up to (but not including) the following stressed syllable.
Some theories of rhythm go further than this, and point to the fact that some feet are stronger than others, producing strong-weak patterns in larger pieces of speech above the level of the foot.
To understand how this could be done, let's start with a simple example: the word 'twenty' has one strong and one weak syllable, forming one foot. A diagram of its rhythmical structure can be made, where s stands for "strong" and w stands for "weak".