Metaphone 3
VERSION 2.1.3

by Lawrence Philips

Metaphone 3 is designed to return an *approximate* phonetic key (and an alternate approximate phonetic key when appropriate) that should be the same for English words, and most names familiar in the United States, that are pronounced *similarly*. The key value is *not* intended to be an *exact* phonetic, or even phonemic, representation of the word. This is because a certain degree of 'fuzziness' has proven to be useful in compensating for variations in pronunciation, as well as misheard pronunciations. For example, although americans are not usually aware of it, the letter 's' is normally pronounced 'z' at the end of words such as "sounds".

The 'approximate' aspect of the encoding is implemented according to the following rules:

(1) All vowels are encoded to the same value - 'A'. If the parameter encodeVowels is set to false, only *initial* vowels will be encoded at all. If encodeVowels is set to true, 'A' will be encoded at all places in the word that any vowels are normally pronounced. 'W' as well as 'Y' are treated as vowels. Although there are differences in the pronunciation of 'W' and 'Y' in different circumstances that lead to their being classified as vowels under some circumstances and as consonants in others, for the purposes of the 'fuzziness' component of the Soundex and Metaphone family of algorithms they will be always be treated here as vowels.

(2) Voiced and un-voiced consonant pairs are mapped to the same encoded value. This means that:
'D' and 'T' -> 'T'
'B' and 'P' -> 'P'
'G' and 'K' -> 'K'
'Z' and 'S' -> 'S'
'V' and 'F' -> 'F'

- In addition to the above voiced/unvoiced rules, 'CH' and 'SH' -> 'X', where 'X' represents the "-SH-" and "-CH-" sounds in Metaphone 3 encoding.

- Also, the sound that is spelled as "TH" in English is encoded to '0' (zero symbol). (Although Americans are not usually aware of it, "TH" is pronounced in a voiced (e.g. "that") as well as an unvoiced (e.g. "theater") form, which are naturally mapped to the same encoding.)

The encodings in this version of Metaphone 3 are according to pronunciations common in the United States. This means that they will be inaccurate for consonant pronunciations that are different in the United Kingdom, for example "tube" -> "CHOOBE" -> XAP rather than american TAP.

Metaphone 3 was preceded by by Soundex, patented in 1919, and Metaphone and Double Metaphone, developed by Lawrence Philips. All of these algorithms resulted in a significant number of incorrect encodings. Metaphone3 was tested against a database of about 100 thousand English words, names common in the United States, and non-English words found in publications in the United States, with an emphasis on words that are commonly mispronounced, prepared by the Moby Words website, but with the Moby Words 'phonetic' encodings algorithmically mapped to Double Metaphone encodings. Metaphone3 increases the accuracy of encoding of english words, common names, and non-English words found in american publications from the 89% for Double Metaphone, to over 98%.

DISCLAIMER: Anthropomorphic Software LLC claims only that Metaphone 3 will return correct encodings, within the 'fuzzy' definition of correct as above, for a very high percentage of correctly spelled English and commonly recognized non-English words. Anthropomorphic Software LLC warns the user that a number of words remain incorrectly encoded, that misspellings may not be encoded 'properly', and that people often have differing ideas about the pronunciation of a word. Therefore, Metaphone 3 is not guaranteed to return correct results every time, and so a desired target word may very well be missed. Creators of commercial products should keep in mind that systems like Metaphone 3 produce a 'best guess' result, and should condition the expectations of end users accordingly.

METAPHONE3 IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. LAWRENCE PHILIPS AND ANTHROPOMORPHIC SOFTWARE LLC MAKE NO WARRANTIES, EXPRESS OR IMPLIED, THAT IT IS FREE OF ERROR, OR ARE CONSISTENT WITH ANY PARTICULAR STANDARD OF MERCHANTABILITY, OR THAT IT WILL MEET YOUR REQUIREMENTS FOR ANY PARTICULAR APPLICATION. LAWRENCE PHILIPS AND ANTHROPOMORPHIC SOFTWARE LLC DISCLAIM ALL LIABILITY FOR DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES RESULTING FROM USE OF THIS SOFTWARE.