This computer exercise is a combination of Problems 2.24 and 2.25 in Chapter 2. In particular, the FFT analysis/synthesis module, in Problem 2.25, will be used within the two bands of the QMF bank. The configuration is shown in Figure 7.5.
a. Given, $H_0(z)=1-z^{-1}, H_1(z)=1+z^{-1}$. Choose $F_0(z)$ and $F_1(z)$ such that the aliasing term can be cancelled. Use $L=32$ and the peak-picking method for component selection. Perform speech synthesis and give timedomain plots of both input and output speech records.
b. Use the same voiced frame selected in Problem 2.24. Give time-domain and frequency-domain plots of $x_{d 0}^{\prime}(n)$ and $x_{d 1}^{\prime}(n)$ in Figure7.5.
c. Compute the overall SNR (between $x(n)$ and $x^{\prime}(n)$ ) and estimate a MOS score for the output speech.
d. Describe whether the perceptual quality of the output speech improves if the FFT analysis/synthesis module is employed within the subbands instead of using it for the entire band.