Compute the fft of the record of my voice

This is my starting code:

 a=audiorecorder(8000,8,1);
 record(a)
 % recording for some seconds, don't remember how many...
 stop(a)
 data=getaudiodata(a);
 plot(data)

I obtained this.

How can I know the duration of the recording (because on the x-axis there are not the seconds...)?

Onother question: how can I compute the fft and find the frequency spectrum of this signal?

Thank you!

Answer 1

[Rick Rosson]

N = length(data);
Fs = 8000;
dt = 1/Fs;
t = dt*(0:N-1)';

figure;
plot(t,data);

[Riccardo Barbero]

Perfect! Thank you Rick!

So, the following is the correct signal in time-domain:

(I called the signal "Emi" because is the name of my girlfriend and this is her voice ;))

However, for the fft, i did as follow:

 datafft=fft(data);
 datafft_abs=abs(datafft/N);
 datafft_abs=datafft_abs(1:N/2+1);
 f=Fs*(0:N/2)/N;
 figure;
 plot(f,datafft_abs)

Doing this, I obtained the follow spectrum:

Is it correct? I have doubts about the y scale representing the amplitude of spectrum...

Answer 2

[richard onipede]

a=audiorecorder(8000,8,1);

record(a)

% recording for some seconds, don't remember how many...

stop(a)

data=getaudiodata(a);

plot(data)