Within human speech, there are two methods employed to form our words. These
sounds are categorized as voiced and unvoiced. For the voiced part, our throat acts like a transfer function. The vowel sounds are included in this category. The unvoiced part describes the noise-like sounds of speech. These are the sounds made with our mouth and tongue (as opposed to our throat), such as the “f” sound, the “s” sound, and the "th" sound.
Often after having calculated the cepstrum, we want to lifter (i.e., filter in the
cepstral domain). When we lifter, we are separating the transfer function and the excitation signal. The transfer function usually appears as a steep slant at the beginning of the plot. The excitation appears as periodic peaks occurring after
around 3 to 9 ms.
Muhammad (2020). Homomorphic Deconvolution (https://www.mathworks.com/matlabcentral/fileexchange/40962-homomorphic-deconvolution), MATLAB Central File Exchange. Retrieved .