I need help in extracting the fundamental frequency from a recorded wav file. The input is an A-chord from the guitar sampled at 44100 Hz using mono.(adsbygoogle = window.adsbygoogle || []).push({});

my source code is as follows. The variable framed is components of the signal required to be processed. So if the waveform of chord A starts at time 1.2 seconds and starts to dissipate at 3.4 seconds, framed would be the signal components from 1.2 until approximately 2.5 seconds.

y = fft(framed);

m = abs(y); % absolute value to eliminate the imaginary components

blocksize = 8000;

% Avoid taking the log of 0.

index = find(m == 0);

xfft(index) = 1e-17;

mag = 20*log(m); % take the magnitude of the fft in dB

mag = mag(1:floor(blocksize/2));

f = (0:length(mag)-1)*Fs/blocksize;

f = f(:);

% Now create a frequency vector for the x-axis and plot the magnitude and phase.

%f = (0:length(framed)-1)'*100/length(framed);

figure;plot(f,mag),

ylabel('Abs. Magnitude'), grid on

xlabel('Frequency [Hertz]')

[ymax,maxindex]= max(mag); % takes the max values

maxindex

ymax

When running this program, the desired output waveform does not show the frequency of chord A (440 Hz) but rather something else. Please help me! Our thesis doesnt seem to be progressing anymore because of this minor but irritable problem. If anyone can please help me on this. Thanks!

miguel.mcervantes@gmail.com

or

blue_raver19@yahoo.com

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Sound Processing in Matlab: I need help

**Physics Forums | Science Articles, Homework Help, Discussion**