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 criteria; and encoding the digital signal in accordance with a classification of the digital signal to create a compressed bit-stream which is packetized and sent to a decoder frame by frame through a communication channel, 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 one or more periodicity parameters of the digital signal satisfy the criteria when: each of pitch differences between subframes in the digital signal is less than a threshold; wherein, the pitch differences between subframes in the digital signal are defined using 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 criteria; and encoding the digital signal in accordance with a classification of the digital signal to create a compressed bit-stream which is packetized and sent to a decoder frame by frame through a communication channel, 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 one or more periodicity parameters of the digital signal satisfy the criteria when: each of pitch differences between subframes in the digital signal is less than a threshold; wherein, the pitch differences between subframes in the digital signal are defined using 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. each of pitch differences between subframes in the digital signal is less than a threshold; wherein, the pitch differences between subframes in the digital signal are defined using 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. <EOS>