cf1 = 2000; % central fq
bw = 0.25; % bandwidth in octave
low_f1 = cf1 / 2 ^ (bw/2); % lower limit of the fq range
high_f1 = cf1 * 2 ^ (bw/2); % upper limit of the fq range
fs = 8000; % sampling frequency
% geberate a gaussian white signal
n = round(0.6*fs); % number of samples
x = randn(n ,1);
% band pass the white noise to get the narrow band
y = bandpass(x, [low_f1 high_f1],fs);
[p, f] = pwelch(y, 1024, 768, 1024, fs);
plot(f, 10*log10(p))
