Encodes names and words as phonetic codes, so that names which sound alike but are spelled differently can be matched. Implements the Metaphone algorithm of Philips (1990, Computer Language, 7(12), 38-43) and the Double Metaphone algorithm of Philips (2000) < https://web.archive.org/web/20250702064845/https://drdobbs.com/the-double-metaphone-search-algorithm/184401251>, which gives a primary and an alternate code for names of many language origins. Unlike most implementations, including 'PGRdup', the codes are not cut to four characters, which keeps long and multi-part names apart. Provides metaphone(), double_metaphone() and sounds_like() for record linkage, deduplication and name search, and includes a data set of common United States surnames.