A phonetic code is a similarity hash for the sound of a word. Given an input word, a phonetic coding algorithm generates a code representing the important sounds of that word. Thus, words with the same phonetic code will usually have similar sounds. This sort of similarity hash is useful in areas such as census-taking and spelling correction. The codes here were implemented for my thimk spelling word suggestion application.
The package here is currently an implementation of the Soundex and Phonix algorithms in Haskell. The implementations have reasonable Haddock documentation which you may refer to for the details.