XE31CZS Exercise  Periodicity in ShortTime DFT Spectrum
Tasks to do:
 Simulated and Real Periodicity in DFT
 Load one period of voiced speech signal vm0per.bin.
(The signal is binary, to load it into MATLAB
use attached function loadbin.m )
and find shortime DFT of these signal. Lenght of the DFT should be
same as the signal (period) length.
 Observe the changes in the spectrum when the given signal is
extended by zeros into 2, 3, 4 times higher length.
 Observe the changes in the spectrum when the length of the signal
is changed by repetition of the same period. Realize it again for 2,
3, 4 times repetition of the period.
 Observe the changes in the spectrum when the signal with 4 times
repeated period is analyzed by DFT of the length
a) 479, 481
b) 470, 490
c) 256, 512
 Observe the periodicity in real signal (voiced sound of speech) vm0.bin, evaluate it for lengths 128, 256, 512, 1024.
 Estimate fundamental period (and fundamental frequency) of sounds
vf5.bin and vm5.bin from their
shorttime DFT spectra.
 Observe shorttime DFT spectra for unvoiced sound of speech uf5.bin and um5.bin
 Weigthing and the Periodicity in STDFT
 Observe periodograms (shorttime DFT spectrum) of above available
signals for widow lengths 128, 256, 512, 1024.
 Observe and explain the changes in achieved results when different
weighting windows are used (rectangular, Hamming, Blackman).
 Evaluation of convolution by DFT
 Create input traingular sequence x1[n] of length 200
 Create input rectangular sequence x2[n] of length 200
 Evaluate convolution of these two sequences using DFT for N =
200, 400, 256, 500 samples

NOTE. Compare linear and
logaritmic scale of yaxis for observation of shorttime magnitude spectra (i.e.
'plot(f,abs(S))' or 'semilogy(f,abs(S))' respectively).