A method of detecting live speech comprises: receiving a signal containing speech; forming a framed version of the received signal that comprises a plurality of frames; forming a first subset of the plurality of frames, wherein each frame of the first subset contains a signal that contains voiced speech; forming a second subset of the plurality of frames, wherein each frame of the second subset contains a signal that contains unvoiced speech; forming a first frame that is representative of a sum of a plurality of frames of the first subset; forming a second frame that is representative of a sum of a plurality of frames of the second subset; performing a time-frequency transformation operation on the first frame, to form an average voiced frequency spectrum; performing a time-frequency transformation operation on the second frame, to form an average unvoiced frequency spectrum; obtaining one or more voiced features from the voiced frequency spectrum; and obtaining one or more unvoiced features from the unvoiced frequency spectrum. Based on the one or more voiced features and the one or more unvoiced features, a determination is made whether the speech is live speech, or not.