Invariance in Phonetics.

The concept of invariance is widely used in studies of speech sounds, but a definition that is both clear and sufficiently general has not been available. In this paper, the concept is explored by comparison with its use in modern geometry. In this usage, one says that property x is invariant with respect to a particular set of transformations. Several well-known models of the phonetic space (those of traditional phonetics, the Jakobsonian model and the phonetic model of The Sound Pattern of English), are recast in terms of the invariance transformations that seem to be implied by the theories.