Introduction

Spoken language can be regarded as the combination of two processes. The first is the process of encoding a message as an utterance. The second is the transmission process which ensures the encoded message is received and understood by the listener.

In this chapter I will argue that the clarity variation of individual syllables is a direct consequence of such a transmission process and that a statistical model of clarity change gives an insight into how such a process functions.

Clarity

We often do not say the same word the same way in different situations. If we read a list of words out loud we say them differently from when we produce them, spontaneously, in a conversation. Even within spontaneous speech there are wide differences in the articulation of the same word by the same speaker. If you remove these words from their context some instances are easier for a listener to recognise than others. The instances that are easier to recognise share a number of characteristics. They tend to be carefully articulated, the vowels are longer and more spectrally distinct and there is less coarticulation. These instances have been articulated more clearly than others. One extreme example of a clear instance of a word is when a speaker is asked to repeat a word because the listener does not understand it. For example:

The second instance of “margarine” will be significantly different acoustically from the first instance. It will be much more clearly articulated.