Hii Jacques,
I understand you want to plot the data in db.
Kindly look into the code given below, it should solve your problem:-
Fs = 16000; % Sampling rate (Hz)
Channels = 1; % Number of audio channels
bits = 16; % Number of bits per sample
r = audiorecorder(Fs, bits, Channels);
duration = 10;
disp('Recording started');
recordblocking(r, duration);
disp('Recording stopped');
X = getaudiodata(r);
N = length(X);
f = (0:N/2) * (Fs/N);
t = (0:N-1) / Fs;
subplot(2,1,1);
plot(t, X);
xlabel('Time (s)');
ylabel('Amplitude');
title('Time Domain Plot');
Y = fft(X, N);
Y = abs(Y(1:N/2+1));
fftResult_dB = 20 * log10(Y); % covert into dB
subplot(2,1,2);
plot(f, fftResult_dB);
xlabel('Frequency (Hz)');
ylabel('Amplitude (dB)');
title('Frequency Domain Plot');
xlim([0, Fs/2]);
grid on;
Hope this helps!
