plot an audio file

How do i plot an audio file that shows the measured kHz and also in 20 miliseconds interval? Im using MATLAB r2021b.

My code is now like this

recObj = audiorecorder;

Fs=8000;

filename = sprintf('myAudioData.wav');

disp('Start speaking.')

recordblocking(recObj, 10);

disp('End of Recording.');

%play(recObj);

doubleArray = getaudiodata(recObj);

audiowrite(filename,doubleArray,Fs);

%plot(doubleArray);

%title('Audio Signal (double)');

[x,Fs] = audioread('myAudioData.wav');

[m,n]=size(x);

dt=1/Fs;

t=dt*(0:m-1);

idx = (t>=1.030) & (t<1.032);

selected_t = t(idx);

selected_x = x(idx,:);

plot(selected_t, selected_x);

Thankyou

Answer 1

[Aman Banthia]

Hi Michael,

I understand that you are trying to plot an audio file for 20 milliseconds which is recorded in the file itself.

To display the frequency in kHz, you would typically perform a Fourier transform on the audio signal to convert it from the time domain to the frequency domain. Here's how you can modify your code to do this:

% Record and save audio
recObj = audiorecorder;
Fs = 8000;
filename = 'myAudioData.wav';
disp('Start speaking.')
recordblocking(recObj, 10);
disp('End of Recording.');
doubleArray = getaudiodata(recObj);
audiowrite(filename,doubleArray,Fs);

% Read audio
[x,Fs] = audioread('myAudioData.wav');
[m,n]=size(x);
dt=1/Fs;
t=dt*(0:m-1);

% Select the time segment
idx = (t>=1.030) & (t<1.032); 
selected_t = t(idx);
selected_x = x(idx,:);

% Plot the time domain signal
subplot(2,1,1);
plot(selected_t, selected_x);
title('Time Domain Signal')
xlabel('Time (s)')
ylabel('Amplitude')

% Perform the Fourier transform
Y = fft(selected_x);
m_sel = length(selected_x);
P2 = abs(Y/m_sel);
P1 = P2(1:m_sel/2+1);
P1(2:end-1) = 2*P1(2:end-1);
f = Fs*(0:(m_sel/2))/m_sel;

% Plot the frequency domain signal
subplot(2,1,2);
plot(f/1000, P1) 
title('Frequency Domain Signal')
xlabel('Frequency (kHz)')
ylabel('|P1(f)|')

Refer to the following MATLAB Documentation to know more about Fast Fourier Transform (‘fft’) function:

https://in.mathworks.com/help/matlab/ref/fft.html

Hope the above solution helps you.

Best Regards,

Aman Banthia