PRACTICAL MATLAB® FOR ENGINEERS PRACTICAL MATLAB

370 Practical MATLAB® Applications for Engineers

ynoise = 3*cos(2*pi*x/2000)+noise;

subplot(2,2,2)

plot(x,y);title(‘Sinusoid test funct ‘);

ylabel(‘Amplitude’)

axis([0 4000 -4 4]);

subplot(2,2,3)

plot(x,noise);title(‘noise vs. t’)

ylabel(‘Amplitude’)

axis([0 100 -1 3]);

xlabel(‘time’);

subplot(2,2,4)

plot(x,ynoise)

xlabel(‘time’);title(‘[sinusoid+noise] vs. t’);

ylabel(‘Amplitude’)

axis([0 1000 -6 6]);

figure(2)

subplot(2,2,1)

specgram(mtlb);title(‘spectrogram of the speech file mtlb’)

subplot(2,2,2)

psd(mtlb);title(‘power spec. den.of mtlb’)

subplot(2,2,3)

specgram(ynoise);

title(‘specgram of sinusoid+noise’)

subplot(2,2,4)

psd(ynoise);

title(‘power spec. den. of sinus.+noise’)

The script fi le specpsol is executed and the resulting plots are shown in Figures 4.20
and 4.21.

FIGURE 4.20
Plots of parts 1, 2, 3, and 4 of R.4.125.

[Speech file mtlb] versus t

4

2

− 2

− 4

0 0 3 2 1 0 0

− 1

Amplitude

1000 2000 3000 4000

noise versus t

Amplitude

50 100

time

Sinusoid test funct

4

2

− 2

− 4

0

Amplitude

0 1000 2000 3000 4000

[sinusoid+noise] versus t

6

4

2

0

− 2

− 4

− 6

0 500

Amplitude

1000

time