# From FFT to PSD using Pwelch Matlab [duplicate]

I am trying to understand the difference between FFT magnitude and PSD (Power spectral density) with pwelch function of Matlab. In my example, Val1 and Val2 will output the same thing?

% N = 94144

% fs = 44100

segmentLength = N; % window size

[pxx,f] = pwelch(signal,segmentLength,[],segmentLength,fs);

%pwelch(data,segmentLength,overlappedSamples,segmentLength,fs);

Y = fft(signal);

Y_mag = abs(Y);

Val1 = 20*log10(Y_mag);

Val2 = 10*log10(pxx);


PS: I have already seen the other posts and I understand very well the difference between PSD and FFT but here I am interested in the diffeeence in code. Thanks

• – MBaz May 21 '17 at 22:21

N = 94144;