在查詢類對話語音識別系統中，詞匯中的少數幾類詞往往占有詞匯量的很大部分，利
用這一重要特點，可以對傳統的基于單樹結構的搜索算法進行改進。本文在采用基于類的語言模型的條件下，在查詢類對話語音識別系統中，對詞匯中的若干大類單獨建樹，從而免除了多數詞匯的語言模型look-ahead 計算時間和存儲空間，并實現了語言分的提前精確運用。針對機票預訂口語對話系統的實驗表明，該搜索策略與單樹方法相比，在同樣的計算資源條件下，時間效率有顯著提高。
關鍵詞: 語音識別 對話系統 搜索 詞樹 look-ahead

Abstract A few of classes often occupy large proportion of vocabulary in speech recognition for many information query dialog system, which can be used to improve traditional search algorithm based on single lexicon tree. Under the condition of using class based n-gram language model, this paper presents a new search strategy which builds separate trees for some big word classes ( classes that own many words) to dispenses with look-ahead computation of many words in decoding process and to use precise probabilities of language model earlier. The experiments on flight reservation dialog system show that the time efficiency of the presented method is obviously higher than single-tree method under equal computational cost.
Key Words speech recognition; dialog system; search; lexicon tree; look-ahead