Cepstral Analysis

Question 1

Cepstrum

order of cepstral analysis

Answer 1

signal, DFT, log, IDFT

Retrieve signal with DFT and exponent

High pass - excitation source
Low pass - vocal tract

Question 2

Quefrency

Answer 2

Measured in units of psuedo-time (1/f)

Question 3

Separating Source and Filter with Cepstrum

Answer 3

• In cepstrum domain, the quefrency axis will show lower frequencies separated from higher frequencies
• The slower frequencies are the vocal tract impulse response
• The faster frequencies are the excitation

Question 4

Homomorphic Filtering

Answer 4

• Change domain so decomposition is easier (into filter and source)
• log(spectrum) = log(excitation spectrum) + log(vocal tract frequency response)
• Extract vocal tract/filter with low pass filter (changes slower as speed limited by biology)
• Extract excitation with high pass filter