%Part 1 - (a, b, c)
[x, fs] = audioread('audio.wav')
x = x(:, 1);
n = length(x)
t = (0:n-1)/fs
n/fs
%Figure 1 - Time domain representation
figure(1)
plot(t, x)
grid on
xlabel('Time(s)')
ylabel('Amplitude')
title('Time domain ')
%Figure 2 - Spectrogram
figure(2)
spectrogram(x, 1024, 512, 1024, fs, 'yaxis')
title('Spectrogram')
%Figure 3 - Power spectrum density
figure(3)
w = hanning(n, 'periodic');
periodogram(x, w, n, fs, 'power')
title('power spectrum density')
%Play the audio
sound(x,fs)
%Part 2 - d
% define filters
freq = linspace(1000,(fs/2),500);
% 1 - LPF FIR / cutoff frequency 3 KHz
N = 64;
fc_lp = 3000;
B_lp = fir1(N,2*fc_lp/fs);
h=freqz(B_lp,1,freq,fs);
m_lp=20*log10(abs(h));
% 2 - BPF FIR / cutoff frequencies 2 and 5 KHz
N = 64;
fc_low = 2000;
fc_high = 5000;
B_bp = fir1(N,2*[fc_low fc_high]/fs);
h=freqz(B_bp,1,freq,fs);
m_bp=20*log10(abs(h));
% 3 - HPF FIR / cutoff frequency 4 KHz
N = 64;
fc_high = 4000;
B_hp = fir1(N,2*fc_high/fs,'high');
h=freqz(B_hp,1,freq,fs);
m_hp=20*log10(abs(h));
% apply filters on audio file
%LPF
x_lp = filter(B_lp,1,x); % filtered by LPF
figure(4)
plot(t,x_lp)
grid on
xlabel('Time(s)')
ylabel('Amplitude')
title('Time domain for LPF')
figure(5)
spectrogram(x_lp, 1024, 512, 1024, fs, 'yaxis')
title('Spectrogram - LPF filtered signal')
figure(6)
w = hanning(n, 'periodic');
periodogram(x_lp, w, n, fs, 'power')
title('LPF power spectrum density')
%BPF
x_bp = filter(B_bp,1,x); % filtered by BPF
figure(7)
plot(t,x_bp)
grid on
xlabel('Time(s)')
ylabel('Amplitude')
title('Time domain for BPF')
figure(8)
spectrogram(x_bp, 1024, 512, 1024, fs, 'yaxis')
title('Spectrogram - BPF filtered signal')
figure(9)
w = hanning(n, 'periodic');
periodogram(x_bp, w, n, fs, 'power')
title('BPF power spectrum density')
x_hp = filter(B_hp,1,x); % filtered by HPF
figure(10)
plot(t,x_hp)
grid on
xlabel('Time(s)')
ylabel('Amplitude')
title('Time domain for HPF')
figure(11)
spectrogram(x_hp, 1024, 512, 1024, fs, 'yaxis')
title('Spectrogram - HPF filtered signal')
figure(12)
w = hanning(n, 'periodic');
periodogram(x_hp, w, n, fs, 'power')
title('HPF power spectrum density')
