Soundex is a phonetic algorithm for indexing names by sound, as pronounced in English. The goal is for homophones to be encoded to the same representation so that they can be matched despite minor differences in spelling.^[1] The algorithm mainly encodes consonants; a vowel will not be encoded unless it is the first letter. Soundex is the most widely known of all phonetic algorithms (in part because it is a standard feature of popular database software such as DB2, PostgreSQL,^[2]MySQL,^[3]SQLite,^[4]Ingres, MS SQL Server^[5] and Oracle.^[6]) Improvements to Soundex are the basis for many modern phonetic algorithms.^[7]

History[edit]

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Soundex was developed by Robert C. Russell and Margaret King Odell^[8] and patented in 1918^[9] and 1922.^[10] A variation, American Soundex, was used in the 1930s for a retrospective analysis of the US censuses from 1890 through 1920. The Soundex code came to prominence in the 1960s when it was the subject of several articles in the Communications and Journal of the Association for Computing Machinery, and especially when described in Donald Knuth'sThe Art of Computer Programming.^[11]

The National Archives and Records Administration (NARA) maintains the current rule set for the official implementation of Soundex used by the U.S. government.^[1] These encoding rules are available from NARA, upon request, in the form of General Information Leaflet 55, 'Using the Census Soundex'.

American Soundex[edit]

The Soundex code for a name consists of a letter followed by three numerical digits: the letter is the first letter of the name, and the digits encode the remaining consonants. Consonants at a similar place of articulation share the same digit so, for example, the labial consonants B, F, P, and V are each encoded as the number 1.

The correct value can be found as follows:

1. Retain the first letter of the name and drop all other occurrences of a, e, i, o, u, y, h, w.
2. Replace consonants with digits as follows (after the first letter):
   • b, f, p, v → 1
   • c, g, j, k, q, s, x, z → 2
   • d, t → 3
   • l → 4
   • m, n → 5
   • r → 6
3. If two or more letters with the same number are adjacent in the original name (before step 1), only retain the first letter; also two letters with the same number separated by 'h' or 'w' are coded as a single number, whereas such letters separated by a vowel are coded twice. This rule also applies to the first letter.
4. If you have too few letters in your word that you can't assign three numbers, append with zeros until there are three numbers. If you have four or more numbers, retain only the first three.

Using this algorithm, both 'Robert' and 'Rupert' return the same string 'R163' while 'Rubin' yields 'R150'. 'Ashcraft' and 'Ashcroft' both yield 'A261'. 'Tymczak' yields 'T522' not 'T520' (the chars 'z' and 'k' in the name are coded as 2 twice since a vowel lies in between them). 'Pfister' yields 'P236' not 'P123' (the first two letters have the same number and are coded once as 'P'), and 'Honeyman' yields 'H555'.

The following algorithm is followed by most SQL languages (excluding PostgreSQL^{[example needed]}):

1. Save the first letter. Map all occurrences of a, e, i, o, u, y, h, w. to zero(0)
2. Replace all consonants (include the first letter) with digits as in [2.] above.
3. Replace all adjacent same digits with one digit, and then remove all the zero (0) digits
4. If the saved letter's digit is the same as the resulting first digit, remove the digit (keep the letter).
5. Append 3 zeros if result contains less than 3 digits. Remove all except first letter and 3 digits after it (This step same as [4.] in explanation above).

The two algorithms above do not return the same results in all cases primarily because of the difference between when the vowels are removed. The first algorithm is used by most programming languages and the second is used by SQL. As examples, both 'Robert' and 'Rupert' yield 'R163', while 'Tymczak' yields 'T520' and 'Honeyman' yields 'H555'. In designing an application, which combines SQL and a programming language, the architect must decide whether to do all of the Soundex encoding in the SQL server or all in the programming language. The MySQL implementation can return more than 4 characters.^[12][13]

Variants[edit]

A similar algorithm called 'Reverse Soundex' prefixes the last letter of the name instead of the first.

The New York State Identification and Intelligence System (NYSIIS) algorithm was introduced in 1970 as an improvement to the Soundex algorithm. NYSIIS handles some multi-character n-grams and maintains relative vowel positioning, whereas Soundex does not.

Daitch–Mokotoff Soundex (D–M Soundex) was developed in 1985 by genealogist Gary Mokotoff and later improved by genealogist Randy Daitch because of problems they encountered while trying to apply the Russell Soundex to Jews with Germanic or Slavic surnames (such as Moskowitz vs. Moskovitz or Levine vs. Lewin). D–M Soundex is sometimes referred to as 'Jewish Soundex' or 'Eastern European Soundex',^[14] although the authors discourage the use of those names. The D–M Soundex algorithm can return as many as 32 individual phonetic encodings for a single name. Results of D-M Soundex are returned in an all-numeric format between 100000 and 999999. This algorithm is much more complex than Russell Soundex.

As a response to deficiencies in the Soundex algorithm, Lawrence Philips developed the Metaphone algorithm in 1990. Philips developed an improvement to Metaphone in 2000, which he called Double Metaphone. Double Metaphone includes a much larger encoding rule set than its predecessor, handles a subset of non-Latin characters, and returns a primary and a secondary encoding to account for different pronunciations of a single word in English. Philips created Metaphone 3 as a further revision in 2009 to provide a professional version that provides a much higher percentage of correct encodings for English words, non-English words familiar to Americans, and first and last names found in the United States. It also provides settings that allow more exact consonant and internal vowel matching to allow the programmer to focus the precision of matches more closely.

See also[edit]

References[edit]

1. ^ ^ab'The Soundex Indexing System'. National Archives and Records Administration. 2007-05-30. Retrieved 2010-12-24.
2. ^'PostgreSQL: Documentation: 9.1: fuzzystrmatch'. postgresql.com. Retrieved 2012-11-03.
3. ^'MySQL :: MySQL 5.5 Reference Manual :: 12.5 String Functions - SOUNDEX'. dev.mysql.com.
4. ^'SQL As Understood By SQLite - Core Functions'. sqlite.org. Retrieved 2017-01-27.
5. ^'SOUNDEX (Transact-SQL)'. msdn.microsoft.com. Retrieved 2012-11-03.
6. ^'SOUNDEX'. docs.oracle.com. Retrieved 2017-10-20.
7. ^'Phonetic Matching: A Better Soundex'. Retrieved 2012-11-03.
8. ^Odell, Margaret King (1956). 'The profit in records management'. Systems. New York. 20: 20.
9. ^US patent 1261167, R. C. Russell, '(untitled)', issued 1918-04-02 (Archived)
10. ^US patent 1435663, R. C. Russell, '(untitled)', issued 1922-11-14 (Archived)
11. ^Knuth, Donald E. (1973). The Art of Computer Programming: Volume 3, Sorting and Searching. Addison-Wesley. pp. 391–92. ISBN978-0-201-03803-3. OCLC39472999.
12. ^CodingForums.com ([1])
13. ^'MySQL :: MySQL 5.5 Reference Manual :: 12.5 String Functions - SOUNDEX'. dev.mysql.com.
14. ^Mokotoff, Gary (2007-09-08). 'Soundexing and Genealogy'. Retrieved 2008-01-27.

English Language Phonetic Matcher

Soundex match surnames that sound similar but have different spellings. It was originally used by the National Archives to index the U.S. censuses.

Use this surname to soundex converter to calculate the soundex code for your surname. Read the soundex limitations to understand how to use soundex searches to find ancestors in genealogy databases.

Since some online genealogy database search engines today are based on soundex and other sound-alike coding in their search algorithms, understanding how soundex works is a key to understanding phonetic searching. Basically, soundex searches are ways of searching for a surname the way it is pronounced, rather than the way it is spelled.

If you are using a genealogy search engine that allows a soundex search, use the chart below to understand what the search engine is doing.

If you type in the surname Smith, you will get surname sound-a-likes with the same soundex code, in this case, Schmidt, Smyth, Smithe, Smithee, Schmitt, Smead, Smit, Sneed, Smoote and many other variations. Notice the vowel variations and the how 't' and 'd' (both with the same soundex code of #3) are used interchangeably.

Enter a surname to find other surnames sharing the same soundex code.
Soundex has its limitations and many genealogy search engines now use a more advanced algorithm, but Rootsweb and others still offer a soundex choice.

RootsWeb World Connect offers a soundex search. If you use the pulldown box that says 'exact', you will notice the other search choices are soundex and metaphone. These choices offer a way to search the database based on the way the name sounds rather than the way it is spelled.

Always start your genealogy searches with an exact search and only if that doesn't work should you extend your search to soundex, metaphone , or other sound-alike searches.

The Soundex Algorithm

• Soundex codes always start with the first letter of the surname and are always followed by three numbers. The numbers represents the first three remaining consonants in the surname. If there are not enough letters in the surname, zeros will be added until there are 3 digits. If the surname is very long, the numbers will be truncated to three. No matter how long or how short the surname, a soundex code always will have one letter followed by three digits.
• Soundex Coding Guide (Consonants that sound alike have the same code)
  1 - B,P,F,V
  2 - C,S,G,J,K,Q,X,Z
  3 - D,T
  4 - L
  5 - M,N
  6 - R
  
• The letters A,E,I,O,U,Y,H, and W are not used.
• Names with adjacent letters having the same equivalent number are coded as one letter with a single number.
• Surname prefixes such as La, De and Van are generally not used in the soundex, although the prefixes Mc, Mac and O generally are coded.

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Soundex Limitations

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• Surnames that sound alike do not always have the same soundex code. For example, Huff (H100) and Hough (H200) are pronounced identically, but have different soundex codes because although the different constanant combinations in English may produce the same sound, the soundex algorithm does not see the names as pronounced the same.
  
• Surnames that sound alike but start with a different first letter will always have a different soundex code. For example, the names Carrigan (C625) and Kerrigan (K625) have different soundex codes even though they sound similar. Surnames that sound alike but have different first letters will need to be searched for separately in a soundex search. However, a metaphone search will find both surnames in the same search. This is one of the reasons to try a metaphone search if the genealogy database offers one.
  
• Since soundex is based on English pronunciation, some European names may not soundex correctly. An example is the French name Roux - where the x is silent. While Rue (R000) is pronounced identically to Roux (R200), they will have different soundex codes. This could be true of any surname that does not use English pronunciation.
  
• Sometimes names that don't sound alike may have the same soundex code and this will give false results in a soundex search. One of my family names is Powers (P620). I get soundex search results for surnames such as Prigg, Perrigo, Porreca and Park which all have the same soundex code, but do not sound similar to my name Powers. Yet the Irish Power (P600) surname, from which my Powers name originated, has a different soundex code. Keep this in mind while soundex searching. Soundex searching will not necessarily catch all variations of a surname.
  

Soundex Tips

When you are searching genealogy databases, do not assume that your surname was spelled many years ago the same way it is today, and that is the way it will appear on the census 100 years ago. The census taker, in a lot of cases, wrote the surname how he heard it, and not the way it was spelled. This is especially true if the person was an immigrant who spoke with an accent. Try listening out loud to the surname and thinking of as many spelling variations as you can think of. One of these may be how your surname was spelled in the census.

Today, we no longer have to use the government soundex cards on microfilm to search the census. The US census that have been released to the public are online and each has a unique database search engine. Many of the search engines use a soundex or similar formula to search for surnames. By understanding how soundex manually works will help to getting the best results from search engines

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