1. A method for performing a telephone directory assistance function, comprising: for each of a plurality of callers: prompting the caller to speak a name associated with a desired directory listing; determining a telephone number desired by the caller based on a speech signal received from the caller subsequent to the step of prompting the caller; releasing the desired telephone number to the caller; and creating a call record comprising the released telephone number and a representation of the speech signal; processing according to a parameter modification algorithm a plurality of the call records to modify parameters of a speech recognition algorithm; and employing the speech recognition algorithm to recognize names spoken by callers in directory assistance calls received subsequent to modification of the parameters of the speech recognition algorithm.