How can PLOT the time waveform and its frequency-domain representation using FFT

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CHIN XUAN TEE 2020-6-12

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https://ww2.mathworks.cn/matlabcentral/answers/546998-how-can-plot-the-time-waveform-and-its-frequency-domain-representation-using-fft

回答： Surya Talluri 2020-8-14

filename = 'abc.mp3';
audioinfo(filename)
[y,Fs] = audioread(filen);  
N = size(y,1);             
t = [0:1/Fs:(N-1)/Fs];     
f = ([0:1:N-1]/N-0.5)*Fs;  
ys = y(:,1);  % 
plot(t);

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KSSV 2020-6-12

Read the documentation of fft. It is a striaght forward task. It is easy.

CHIN XUAN TEE 2020-6-12

filename = 'abc.mp3';

audioinfo(filename)

[y,Fs] = audioread(filen);

N = size(y,1);

t = [0:1/Fs:(N-1)/Fs];

f = ([0:1:N-1]/N-0.5)*Fs;

ys = y(:,1); %

plot(t);

Y = fft(ys,N);

magnitudeY = abs(Y);

plot(f,magnitudeY);

Is this correct？

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Answer 1

Surya Talluri 2020-8-14

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/546998-how-can-plot-the-time-waveform-and-its-frequency-domain-representation-using-fft#answer_479658

在 MATLAB Online 中打开

I understand that you want to observe the signal in both time and frequency domain.

You can directly plot the signal in time domain

[y,Fs] = audioread(filename);
N = size(y,1);
t = (0:N-1)/Fs;
  
plot(t, y)
xlabel('Time(s)')
ylabel('Amplitude')

You can obtain Frequency domain using “fft” function

Y = fft(y,N);
F = ((0:1/N:1-1/N)*Fs).';
magnitudeY = abs(Y);        % Magnitude of the FFT
phaseY = unwrap(angle(Y));  % Phase of the FFT
dB_mag=mag2db(magnitudeY);
subplot(2,1,1);
plot(F(1:end/2),dB_mag(1:end/2));
title('Magnitude response of signal');
ylabel('Magnitude(dB)');
 
subplot(2,1,2);
plot(F(1:end/2),phaseY(1:end/2));
title('Phase response of signal');
xlabel('Frequency in kHz')
ylabel('radians');