MATLAB: Reading, writing and processing .wav files in Matlab

frequencywav

Im on a school project and my problem is that I have a .wav file and I want to find the highest Db vs. frequency (Hertz) in that file. I'm measuring what frequency will sound (in the human ear) the highest. So I need a plot Db vs. frequency.

any idea?

Best Answer

The fft function will do what you want, although you have to specify the magnitude of the fft in dB. The documentation for fft has the essential code between the first two figures in the documentation. You will need the log10 function to calculate dB from the magnitude.

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MATLAB: Can the amplitude be plotted in dB

Try this:

semilogx(Fv, 20*log10(abs(FT_af(Iv,2))*2)), xlabel('Frequency, Hz'),ylabel('magnitude');

That will convert the amplitudes to dB. The y-axis will reflect those changes, however the tick marks will not be in integer powers-of-10 such as with your x-axis and the semilogx call. You will have to format the y-axis ticks yourself.

MATLAB: How to plot (1) amplitude vs time and (2) amplitude vs frequency plots from .wav file

The amplitude - Frequency plot would go something like this:

[y,Fs]=audioread('HornC5.wav'); %Reads .wav file into 2 matrices for amplitude (y) and sampling frequency 
L = size(y,1);
Fn = Fs/2;
FTy = fft(y)/L;
Fv = linspace(0, 1, fix(L/2)+1)*Fn;
Iv = 1:numel(Fv);
figure
plot(Fv, abs(FTy(Iv,:))*2)
grid
xlabel('Frequency')
ylabel('Amplitude')

There could be two channels in the .wav file. This will plot both of them in the same plot. Note that ‘Fn’ is the Nyquist frequency, ‘Fv’ is the frequency vector, and ‘Iv’ is the index vector for the plot or other analyses.

I do not have your .wav file so I could not test this with it. It should work.

Best Answer

Related Solutions

MATLAB: Can the amplitude be plotted in dB

MATLAB: How to plot (1) amplitude vs time and (2) amplitude vs frequency plots from .wav file

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