Soundex

Phonetic algorithm for indexing names by sound

Soundex

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Class	Phonetic algorithm
Data structure
Worst-case performance
Best-case performance
Average performance
Worst-case space complexity
Optimal

Soundex is a phonetic algorithm for indexing names by sound, as pronounced in English. The goal of Soundex is to encode homophones to the same representation so that they can be matched despite minor differences in spelling. Soundex is used primarily in genealogy and data management.

History

Soundex was developed by Robert C. Russell and Margaret King Odell and patented in 1918 and 1922. It was initially used in the United States Census to help match names despite variations in spelling.

Algorithm

The Soundex algorithm converts a name to a four-character code. The first character of the code is the first letter of the name, and the remaining three characters are numbers that encode the remaining consonants. Similar sounding consonants share the same number, while vowels are ignored unless they are the first letter.

Steps

1. Retain the first letter of the name. 2. Remove all occurrences of 'h' and 'w' except first letter. 3. Replace all consonants (include the first letter) with digits as follows:

  - b, f, p, v → 1
  - c, g, j, k, q, s, x, z → 2
  - d, t → 3
  - l → 4
  - m, n → 5
  - r → 6

4. Replace all adjacent same digits with one digit. 5. Remove all occurrences of a, e, i, o, u, y except first letter. 6. If the result is too short (less than 4 characters), pad with zeros. 7. If the result is too long, truncate to four characters.

Example

For example, the Soundex code for "Robert" is R163: - R (first letter) - o (ignored) - b → 1 - e (ignored) - r → 6 - t → 3

Applications

Soundex is widely used in genealogy for matching surnames that sound similar but are spelled differently. It is also used in data management systems to find duplicate records.

Limitations

Soundex has several limitations: - It is designed for English names and may not work well with names from other languages. - It can produce the same code for names that sound different. - It may not handle names with non-standard spellings well.

See also

• Metaphone
• Double Metaphone
• Caverphone
• NYSIIS
• Phonetic algorithm

Related pages

• Genealogy
• Data management
• Phonetic algorithm
• United States Census