Limitations to Soundex Coding
There are several limitations to the Russell Soundex system:
• It was designed to work with English names and English phonetic sounds. There is no support for characters beyond the 26 letters (A to Z) found in the English language.
• Soundex is also based on English pronunciations. Continental European family names often code poorly. For example, many French family names have silent last letters that are not pronounced, but end up being coded using soundex. Thus, Beaux has a Soundex code of B-200 even though the “x” is not pronounced.
• This problem can also occur with family names that sound exactly alike, but have different spellings because the name contains silent letters. For example, Michum (M-250) has a different soundex code from Mitchum (M-325) because the silent “t” is coded in Mitchum.
• Names that sound alike, but start with a different letter, will have different Soundex codes. In particular, be aware of names that begin with either C or K. They are often a variation on spelling of the same name, but will have different Soundex codes. For example, Craft is C-613, but Kraft is K-613.
• Family names that are totally unrelated to each other can have the same Soundex code. This occurs most often with short names or names with a high percentage of vowels (i.e. names with less than three phonetic sounds, or a Soundex code that contains zeros). For example, Smith (S-530) shares the same Soundex code with such diverse family names as Saint, Sand, Schmid, Snead and Sunday.
• Soundex also has trouble discriminating long English names (i.e. names with more than 3 phonetic sounds) or names with non-English phonetic sounds. For example, the Russell soundex coding system does not work well on Slavic or Yiddish family names. The Jewish Genealogical Society has developed a refined system that is more independent of ethnic considerations. This system was designed by Randy Daitch and Gary Mokotoff and is known as the Daitch-Mokotoff Soundex system. It is more complicated than the Russell Soundex system because it can handle more phonetic sounds and because it is based on a six-digit Soundex code. The U.S. National Archives and Records Administration, however, continue to use the Russell Soundex system.