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SignalProcessingMidterm
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Gabri6 2023-04-20 11:16:27 +02:00
parent c99f4cd218 fe60a1a27d
commit 1d82712707
2 changed files with 109 additions and 3 deletions
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48
frequencySpectrum.m Normal file
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function power = frequencySpectrum(signal, fs)
%%%%%%%%%%%%%%%%%%
%function frequencySpectrum(signal, fs)
%
% Task: Display the power spectrum of a given signal
%
% Input:
% - signal: the input signal to process
% - fs: the sampling rate
%
% Output:
% - power: power spectrum of the signal
%
%
% Guillaume Gibert, guillaume.gibert@ecam.fr
% 25/04/2022
%%%%%%%%%%%%%%%%%%
n = length(signal); % number of samples
y = fft(signal, n);% compute DFT of input signal
power = abs(y).^2/n; % power of the DFT
[val, ind] = max(power); % find the mx value of DFT and its index
% plots
figure;
subplot(1,3,1) % time plot
t=0:1/fs:(n-1)/fs; % time range
plot(t, signal)
xticks(0:0.1*fs:n*fs);
xticklabels(0:0.1:n/fs);
xlabel('Time (s)');
ylabel('Amplitude (a.u.)');
subplot(1,3,2) % linear frequency plot
f = (0:n-1)*(fs/n); % frequency range
plot(f,power, 'b*'); hold on;
plot(f,power, 'r');
xlabel('Frequency (Hz)')
ylabel('Power (a.u.)')
subplot(1,3,3) % log frequency plot
plot(f,10*log10(power/power(ind)));
xlabel('Frequency (Hz)')
ylabel('Power (dB)')

64
main.m
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%Last Modified: 20/04/23 10:08
%
%%%%%%%%%%%%%%%%
pkg load signal;
Fs = 300; %Hz
samplingFreq = 300; %Hz
fMin = 30; %Hz
fMax = 40; %Hz
signal = csvread('unknownsignal.csv');
signalDuration = size(signal)/Fs; %s
t=[0:1/Fs:(size(signal,2)-1)/Fs];
signalDuration = size(signal,2)/samplingFreq; %s
t=[0:1/samplingFreq:(size(signal,2)-1)/samplingFreq];
windowDuration = signalDuration/2;
figure;
plot(t,signal)
xlabel('Time (s)');
ylabel('Sound (dB)');
title('unknown Signal');
blackmanWin = zeros(1, length(t));
for l_sample=1:windowDuration*samplingFreq
blackmanWin(l_sample+signalDuration*samplingFreq/4) = (0.42 - 0.5 * cos(2*pi*(l_sample)/(signalDuration*samplingFreq/2)) + 0/08*cos(4*pi*(l_sample)/(windowDuration*samplingFreq/2)));
end
% plot Blackman window
%~ figure;
%~ plot(t, blackmanWin);
% apply the Blackman window
for l_sample=1:length(t)
signal_blackman(l_sample) = signal(l_sample) * blackmanWin(l_sample);
end
% plot signal windowed by rectangular window
%~ figure;
%~ plot(t, signal_blackman);
% plot the frequency spectrum of this windowed signal
power_blackman = frequencySpectrum(signal_blackman, samplingFreq);
fft_signal = fft(signal);
size(fft_signal)
figure;
plot(t, fft_signal);
xlabel('Freq (Hz)');
ylabel('Sound (dB)');
title('FFT of signal');
N=size(signal)(2);
freq=(0:N-1)*samplingFreq/N;
%frequency from frame rate
minfreq=30; %Hz
maxfreq=40; %Hz
idx_min = find(freq >= minfreq, 1);
idx_max = find(freq <= maxfreq, 1, 'last');
filtered_freq = freq(idx_min:idx_max);
figure;
plot(t, filtered_freq);
%[a, b] = butter(1, [1/fMax, 1/fMin], 'bandpass');
%filtered_signal = filter(b,1, signal);
%figure;
%plot(t,filtered_signal)
%xlabel('Time (s)');
%ylabel('Sound (dB)');