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DoubleMetaphone

Double Metaphone (Lawrence Philips, 2000): one word, two codes, so a name that is pronounced more than one way can match on either.

public static class DoubleMetaphone

Example — the pair that is the reason this encoder exists.

using Lodestar.Text.Phonetics;

DoubleMetaphoneCode smith = DoubleMetaphone.Encode("Smith");
DoubleMetaphoneCode schmidt = DoubleMetaphone.Encode("Schmidt");

string a = smith.Secondary;  // => XMT
string b = schmidt.Primary;  // => XMT

Remarks — the other four encoders in this namespace answer with one code, which forces a single verdict on a spelling that has more than one plausible reading. Smith is English and sounds like SM0; it is also the anglicisation German speakers write as Schmidt, which sounds like XMT. A single code has to pick one and lose the other match. Double Metaphone returns both, and two words are candidates when any of their codes agree — which is what puts Smith and Schmidt together above without putting every S-word with them.

Secondary is empty when a word has only one reading, which is the common case: over the 423-word corpus this is pinned to, 102 words carry an alternate and 321 do not. Empty means no alternate, not no code — compare against Primary when it is empty.

The output alphabet is A F H J K L M N P R S T X 0, where X is "sh" and 0 is "th". Codes are not truncated to four characters: the reference does not truncate, and a caller who wants the classic four can take them from the front.

Reference behaviour is doublemetaphone.doublemetaphone 1.2. Decision 0075 records why that library rather than jellyfish — which exports no Double Metaphone at all — and the 401-word comparison that showed the two independent permissive implementations agree on every primary, so the choice freezes an algorithm rather than one library's dialect.

Applies to — net10.0, netstandard2.0.

See also — Metaphone, Nysiis, the phonetics index.

Members

Member	What it does
DoubleMetaphone.Encode	The two Double Metaphone codes of one word.