A method for classifying signals prior to encoding, the method comprising: receiving a digital signal comprising audio data, the digital signal being initially classified as an AUDIO signal; re-classifying the digital signal as a VOICED signal when one or more periodicity parameters of the digital signal satisfy a criteria; and encoding the digital signal in accordance with a classification of the digital signal, wherein the digital signal is encoded in the frequency-domain when the digital signal is classified as an AUDIO signal, and wherein the digital signal is encoded in the time-domain when the digital signal is re-classified as a VOICED signal; wherein the method is characterized in that: re-classifying the digital signal as a VOICED signal when one or more periodicity parameters of the digital signal satisfy a criteria comprises: determining pitch differences between subframes in the digital signal; and re-classifying the digital signal as a VOICED signal when each of the pitch differences is less than a threshold; wherein, determining pitch differences between subframes in the digital signal comprises: determining the pitch differences by using the following expressions: dpit 1 = P 1 − P 2 dpit 2 = P 2 − P 3 dpit 3 = P 3 − P 4 where dpit1, dpit2 and dpit3 are the pitch differences, P 1, P 2, P 3, and P 4 for each subframe are the best pitch candidates found in the pitch range from P = PIT_MIN to P=PIT_MAX, where the PIT_MIN is a minimum pitch limit, and PIT_MAX is a maximum pitch limit. receiving a digital signal comprising audio data, the digital signal being initially classified as an AUDIO signal; re-classifying the digital signal as a VOICED signal when one or more periodicity parameters of the digital signal satisfy a criteria; and encoding the digital signal in accordance with a classification of the digital signal, wherein the digital signal is encoded in the frequency-domain when the digital signal is classified as an AUDIO signal, and wherein the digital signal is encoded in the time-domain when the digital signal is re-classified as a VOICED signal; wherein the method is characterized in that: re-classifying the digital signal as a VOICED signal when one or more periodicity parameters of the digital signal satisfy a criteria comprises: determining pitch differences between subframes in the digital signal; and re-classifying the digital signal as a VOICED signal when each of the pitch differences is less than a threshold; wherein, determining pitch differences between subframes in the digital signal comprises: determining the pitch differences by using the following expressions: dpit 1 = P 1 − P 2 dpit 2 = P 2 − P 3 dpit 3 = P 3 − P 4 where dpit1, dpit2 and dpit3 are the pitch differences, P 1, P 2, P 3, and P 4 for each subframe are the best pitch candidates found in the pitch range from P = PIT_MIN to P=PIT_MAX, where the PIT_MIN is a minimum pitch limit, and PIT_MAX is a maximum pitch limit. re-classifying the digital signal as a VOICED signal when one or more periodicity parameters of the digital signal satisfy a criteria comprises: determining pitch differences between subframes in the digital signal; and re-classifying the digital signal as a VOICED signal when each of the pitch differences is less than a threshold; wherein, determining pitch differences between subframes in the digital signal comprises: determining the pitch differences by using the following expressions: dpit 1 = P 1 − P 2 dpit 2 = P 2 − P 3 dpit 3 = P 3 − P 4 where dpit1, dpit2 and dpit3 are the pitch differences, P 1, P 2, P 3, and P 4 for each subframe are the best pitch candidates found in the pitch range from P = PIT_MIN to P=PIT_MAX, where the PIT_MIN is a minimum pitch limit, and PIT_MAX is a maximum pitch limit. determining pitch differences between subframes in the digital signal; and re-classifying the digital signal as a VOICED signal when each of the pitch differences is less than a threshold; wherein, determining pitch differences between subframes in the digital signal comprises: determining the pitch differences by using the following expressions: dpit 1 = P 1 − P 2 dpit 2 = P 2 − P 3 dpit 3 = P 3 − P 4 where dpit1, dpit2 and dpit3 are the pitch differences, P 1, P 2, P 3, and P 4 for each subframe are the best pitch candidates found in the pitch range from P = PIT_MIN to P=PIT_MAX, where the PIT_MIN is a minimum pitch limit, and PIT_MAX is a maximum pitch limit. determining the pitch differences by using the following expressions: dpit 1 = P 1 − P 2 dpit 2 = P 2 − P 3 dpit 3 = P 3 − P 4 where dpit1, dpit2 and dpit3 are the pitch differences, P 1, P 2, P 3, and P 4 for each subframe are the best pitch candidates found in the pitch range from P = PIT_MIN to P=PIT_MAX, where the PIT_MIN is a minimum pitch limit, and PIT_MAX is a maximum pitch limit.