Sound coding is an algorithm for creating indices for words based on their pronunciation. The goal is for homophones to be encoded to the same representation so that they can be matched despite minor differences in spelling. From an English word, you generate a letter and three numbers that roughly describe how a given word sounds. Similar sounding words will have similar codes. The first letter of the sound code is simply the first letter in the word. The remaining numbers range from 1 to 6, indicating different categories of sounds created by consonants following the first letter. If the word is too short to generate 3 numbers, 0 is added as needed. If the generated code is longer than 3 numbers, the extra are thrown away.

Code	Letters	Description
1	B, F, P, V	Labial
2	C, G, J, K, Q, S, X, Z	Gutterals and sibilants
3	D, T	Dental
4	L	Long liquid
5	M, N	Nasal
6	R	Short liquid
SKIP	A, E, H, I, O, U, W, Y	Vowels (and H, W, and Y) are skipped

There are several special cases when calculating a sound code:

Letters with the same sound number that are immediately next to each other are discarded. So Pfizer becomes Pizer, Sack becomes Sac, Czar becomes Car, Collins becomes Colins, and Mroczak becomes Mrocak.

If two letters with the same sound number separated by "H" or "W", only use the first letter. So Ashcroft is treated as Ashroft.

Sample Sound Codes

Word	Sound Code
Washington	W252
Wu	W000
DeSmet	D253
Gutierrez	G362
Pfister	P236
Jackson	J250
Tymczak	T522
Ashcraft	A261