EXTENSION OF EXCITATION
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As one can see the spectrograms of the top most (wideband speech) and bottom most (extended wideband speech) plots are the most similar. Both wideband spectrograms have most of the energy concentrated on the lower frequencies (0-400Hz), and gradually loses frequency energies as frequencies tend to the Fs/2 (Fs = 8KHz). This is contrary to the narrowband spectrogram pattern, which seems to have a more abrupt fall off in energy at the very high frequency range (3400Hz). For an additional informal testing procedure, one can listen to the wideband, narrowband, and reconstructed wideband speech utterances. These utterances were found by filtering the respective excitation signal with the wideband LPC coefficients. |