reading, writing and processing .wav files in Matlab

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?

Answer 1

[Star Strider]

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.

[Haraldur Mímir Bjarnason]

I don't really know how to use the fft function, this is a script that I've been using, with psd.

[y,Fs]=audioread('2.h10-2000Hz.wav');

%mic

mic = y(:,1);

dt = 1/Fs;

%figure

plot(psd(spectrum.periodogram,mic,'Fs',Fs,'NFFT',length(mic)));

axis([0 2.1 -180 0])

[Star Strider]

Here is the approach I outlined, with a synthesised signal since I don’t have your .wav file:

t = linspace(0, 1, 1E+4);                       % Create Signal
y = sin(2*pi*t*100) + cos(2*pi*t*50);
Fs = 1/mean(diff(t));

Fn  = Fs/2;                                     % Nyquist Frequency
fty = fft(y)/length(y);                         % Take FFT & Normalise
fv  = linspace(0, 1, fix(length(fty)/2)+1)*Fn;  % Frequency Vector For Plot
iv  = 1:length(fv);                             % Index Vector For Plot

figure(1)
plot(fv, 20*log10(abs(fty(iv))))                % Plot In dB
xlabel('Frequency (Hz)')
ylabel('Amplitude (dB)')
axis([0  250    ylim])

You will likely have to experiment to get the result you want with your signal.