EXTENSION OF SPECTRAL ENVELOPE
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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. It is also seen that the narrowband spectrogram has most of its spectral energy associated with the lower frequencies (0-2KHz). It seems that the reconstructed wideband spectrogram effectively flattens the energy content such that it encompasses the whole frequency spectrum. Regarding the spectral envelopes to the left, it is seen that the reconstructed wideband spectral envelope follows the original wideband spectral envelope much better than the narrowband counterpart, especially for the low frequencies.
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However for high frequencies the narrowband and the reconstructed wideband spectral envelope start to resemble each other more and deviate from the wideband spectral envelope. The estimated spectral envelope shown in green is used primarily for attaining the reconstructed wideband spectral envelope. For further qualitative testing purposes one can listen to the utterances of wideband , narrowband and reconstructed wideband speech. |
