Soundex is a phonetic algorithm for indexing names by sound, as pronounced
in English. The goal is for names with the same pronunciation to be encoded
to the same representation so that they can be matched despite minor
differences in spelling. Soundex is the most widely known of all phonetic
algorithms and is often used (incorrectly) as a synonym for "phonetic
algorithm". Improvements to Soundex are the basis for many modern phonetic
algorithms. (Wikipedia, 2007)

This module implements the original soundex algorithm developed by Robert
Russell and Margaret Odell, patented in 1918 and 1922, as well as a
variation called "American Soundex" used for US census data, and current
maintained by the National Archives and Records Administration (NARA).

The soundex algorithm may be recognized from Donald Knuth's *The Art of
Computer Programming*. The algorithm described by Knuth is the NARA
algorithm.