Digital Signal Processing Systems, Basic Filtering Types, and Digital Filter Realizations - Digital Signal Processing: Fundamentals and Applications - page 214

d. perform filtering, that is, calculate yðnÞ for the first 1,000 samples for each of the
following inputs and plot the filter outputs using MATLAB, assuming that all initial
conditions are zeros and the sampling rate is 8,000 Hz:
xðnÞ¼ cos

n
8 ; 000

p, 10 3

xðnÞ¼ cos 8

n
8 ; 000 3 p, 10 3

xðnÞ¼ cos 6 p, 10 3

n
8 ; 000

e. repeat (d) using the MATLAB function filter().
6.30. Repeat (d) in Problem 6.29 using direct-form II structure.

6.9.2 MATLAB Projects
6.31. Sound effects of pre-emphasis filtering:

A pre-emphasis filter is shown in Figure 6.36 with a selective parameter 0 a < 1, which
controls the degree of pre-emphasis filtering. Assuming the system has a sampling rate of
8,000 Hz, plot the frequency responses for a ¼ 0, a ¼ 0 : 4, a ¼ 0 : 8, a ¼ 0 : 95, a ¼ 0 : 99,
respectively. For each case, apply the pre-emphasis filter to the given speech (“speech.dat”)
and discuss the sound effects.

6.32. Echo generation (sound regeneration):
Echo is the repetition of sound due to sound wave reflection from the objects. It can easily be
generated using an FIR filter such as that in Figure 6.37 , where j a j < 1 is an attenuation

FIGURE 6.36

A pre-emphasis filter.

FIGURE 6.37

A single echo generator using an FIR filter.