Phonetic Algorithm

A phonetic algorithm is an algorithm for indexing of words by their pronunciation. Most phonetic algorithms were developed for use with the English language; consequently, applying the rules to words in other languages might not give a meaningful result.

They are necessarily complex algorithms with many rules and exceptions, because English spelling and pronunciation is complicated by historical changes in pronunciation and words borrowed from many languages.

Among the best-known phonetic algorithms are:

• Soundex, which was developed to encode surnames for use in censuses. Soundex codes are four-character strings composed of a single letter followed by three numbers.
• Daitch–Mokotoff Soundex, which is a refinement of Soundex designed to better match surnames of Slavic and Germanic origin. Daitch–Mokotoff Soundex codes are strings composed of six numeric digits.
• (German) Kölner Phonetik: This is similar to Soundex, but more suitable for German words.
• Metaphone and Double Metaphone, which is suitable for use with most English words, not just names. Metaphone algorithms are the basis for many popular spell checkers.
• New York State Identification and Intelligence System (NYSIIS), which maps similar phonemes to the same letter. The result is a string that can be pronounced by the reader without decoding.
• Match Rating Approach developed by Western Airlines in 1977 - this algorithm has an encoding and range comparison technique.
• Caverphone, created to assist in data matching between late 19th century and early 20th century electoral rolls, optimized for accents present in parts of New Zealand.