Phonetic reversal

Phonetic reversal is the process of reversing the phonemes or phones of a word or phrase. When the reversal is identical to the original, the word or phrase is called a phonetic palindrome. Phonetic reversal is not entirely identical to backmasking, which is specifically the reversal of recorded sound. This is because pronunciation in speech causes a reversed diphthong to sound different in either direction (e.g. "eye" becoming "yah" ), or differently articulate a consonant depending on where it lies in a word, hence creating an imperfect reversal.
Backmasking involves not only the reversal of the order of phonemes or phones, but the reversal of the allophonic realizations of those phonemes. Strictly speaking, a reversal of phonemes will still result in allophones appropriate for the new position; for example, if a word with a final /t/ is reversed so that the /t/ is initial, the initial /t/ will be aspirated in line with the conventional allophonic patterns of English phonology.
According to proponents of reverse speech, phonetic reversal occurs unknowingly during normal speech.