1. A method for improving an acoustic model, comprising: acquiring, by a computer, a first standard deviation value by calculating standard deviation of a first feature from a first training data acquired in first environment; acquiring, by the computer, a second standard deviation value by calculating standard deviation of a second feature from second training data acquired in a second environment; calculating, by the computer, a modified first feature, by multiplying the second feature acquired from the second training data by a ratio obtained by dividing the first standard deviation value by the second standard deviation value; reconstructing, by the computer, an acoustic model constructed using training data acquired in the first environment, using the modified first feature; acquiring speech data for speech recognition; and performing speech recognition on the speech data using the reconstructed acoustic model.