A method for processing a speech signal comprising a plurality of frames, the method comprising: determining an unvoicing parameter for a current frame of the speech signal, wherein the unvoicing parameter reflects a characteristic of unvoiced speech in the current frame; wherein the unvoicing parameter is determined based on a product of 1- P voicing and 1- P tilt, P voicing is a periodicity parameter and P tilt is a spectral tilt parameter; smoothing the unvoicing parameter to obtain a smoothed unvoicing parameter for the current frame, wherein the smoothed unvoicing parameter for the current frame is a weighted sum of the unvoicing parameter for the current frame and a smoothed unvoicing parameter for a frame prior to the current frame of the speech signal; if the smoothed unvoicing parameter for the frame prior to the current frame is greater than the unvoicing parameter for the current frame, a weight of the unvoicing parameter for the current frame is 0.1 and a weight of the smoothed unvoicing parameter for the frame prior to the current frame is 0.9; if the smoothed unvoicing parameter for the frame prior to the current frame is not greater than the unvoicing parameter for the current frame, the weight of the unvoicing parameter for the current frame is 0.01 and the weight of the smoothed unvoicing parameter for the frame prior to the current frame is 0.99; computing a difference between the unvoicing parameter for the current frame and the smoothed unvoicing parameter for the current frame; and determining whether the current frame of the speech signal is an unvoiced speech signal using the computed difference as a decision parameter. determining an unvoicing parameter for a current frame of the speech signal, wherein the unvoicing parameter reflects a characteristic of unvoiced speech in the current frame; wherein the unvoicing parameter is determined based on a product of 1- P voicing and 1- P tilt, P voicing is a periodicity parameter and P tilt is a spectral tilt parameter; smoothing the unvoicing parameter to obtain a smoothed unvoicing parameter for the current frame, wherein the smoothed unvoicing parameter for the current frame is a weighted sum of the unvoicing parameter for the current frame and a smoothed unvoicing parameter for a frame prior to the current frame of the speech signal; if the smoothed unvoicing parameter for the frame prior to the current frame is greater than the unvoicing parameter for the current frame, a weight of the unvoicing parameter for the current frame is 0.1 and a weight of the smoothed unvoicing parameter for the frame prior to the current frame is 0.9; if the smoothed unvoicing parameter for the frame prior to the current frame is not greater than the unvoicing parameter for the current frame, the weight of the unvoicing parameter for the current frame is 0.01 and the weight of the smoothed unvoicing parameter for the frame prior to the current frame is 0.99; computing a difference between the unvoicing parameter for the current frame and the smoothed unvoicing parameter for the current frame; and determining whether the current frame of the speech signal is an unvoiced speech signal using the computed difference as a decision parameter.