动态回归系数

http://www1.icsi.berkeley.edu/Speech/docs/HTKBook3.2/node67_mn.html

Delta, Acceleration and Third Differential Coefficients

The performance of a speech recognition system can be greatly enhanced by adding time derivatives to the basic static parameters. In HTK, these are indicated by attaching qualifiers to the basic parameter kind. The qualifier_Dindicates that first order regression coefficients (referred to as delta coefficients) are appended, the qualifier_Aindicates that second order regression coefficients (referred to as acceleration coefficients) and the qualifier_Tindicates that third order regression coefficients (referred to as third differential coefficients) are appended. The_Aqualifier cannot be used without also using the_Dqualifier. Similarly the_Tqualifier cannot be used without also using the_Dand_Aqualifiers.

The delta coefficientsare computed using the following regression formula