1. A method for training a speech classifier in a spoken language understanding system using an available set of utterances associated with a single kind of information, the available set of utterances including a first labeled part and a second unlabeled part, the method comprising: (1) training via a processor a speech classifier for a spoken language understanding system with the first labeled part of the available set of utterances; (2) selecting via the processor a portion of the second unlabeled part of the available set of utterances; and (3) augmenting via the processor the trained speech classifier with the selected portion of the second unlabeled part of the available set of utterances, wherein the augmenting further comprises minimizing a loss function.