Animated models

The basic principle underlying animated models are the notions of a time frame or time window, and a sequence of time windows.

A time window is a function which maps a signal to a continuous range of values in an interval. Examples of time windows are:

• Switching to a radio station for a period of time: the signal from the radio station is mapped on to acoustic values emitted by the radio (and filtered by properties of the radio set).
• A short interval in an signal which is digitally sampled: here, the signal in the interval is mapped to a single digital value.
• A single still television picture: the analog visual signal of the original is mapped to a sequence of lines, each of which consists of a sequence of dots, the whole of which taken together represents a temporal interval.
• A single frame of a movie picture: the analog visual signal of the original scene is mapped to an analog spatial signal representing a temporal interval.

In the speech production animations, this principle is used: a sequence of images is presented one after the other. If the speed of presentation is fast enough, and if the differences between adjacent images are small enough, the effect of continuous movement arises, as in a film.