11. A system comprising: one or more computers and one or more storage devices storing instructions that are operable, when executed by the one or more computers, to cause the one or more computers to perform operations comprising: receiving a voice search query from a user device; determining a query context associated with the voice search query; determining, based on the query context, to apply one or more language model rules; dynamically adjusting one or more probabilities in a base language model according to the applied language model rules to generate a customized language model; using the customized language model to generate a text search query from the voice search query; and providing for display on the user device, one or more search results responsive to the text search query.
11. A system comprising: one or more computers and one or more storage devices storing instructions that are operable, when executed by the one or more computers, to cause the one or more computers to perform operations comprising: receiving a voice search query from a user device; determining a query context associated with the voice search query; determining, based on the query context, to apply one or more language model rules; dynamically adjusting one or more probabilities in a base language model according to the applied language model rules to generate a customized language model; using the customized language model to generate a text search query from the voice search query; and providing for display on the user device, one or more search results responsive to the text search query. 18. The system of claim 11 , wherein the query context includes event information and the language model rules include event language model rules having an adjustment factor for adjusting a probability value of the base language model.