MATLAB: Analysis number from dtmf sound

hello, i have a wav file, which use dtmf i do spectrogram on the file and i receive 10 amplitude peak how can i return the 2 frequency of each peak (high and low frequency)

Best Answer

You did not post your data so I cannot be specific. You can get the frequency and time output as vectors from spectrogram:

[S,F,T] = spectrogram(...) returns a vector of frequencies, F , and a vector of times, T , at which the spectrogram is computed. F has length equal to the number of rows of S . T has length k (defined above) and the values in T correspond to the center of each segment.

There is probably no neat and efficient way to do what you want. I would loop through S at each time, sort and threshold the amplitudes to find the indices of the values >-35dB or so, then use the indices returned by sort to determine the frequencies. (Using the find function is also a possibility, but I am not certain it would make this more efficient.)

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MATLAB: How to use periodogram

wavread() will return the sampling frequency. Then you input the sampling frequency into periodogram() (along with the other documented inputs) to get a meaningful frequency vector as an output.

[x,Fs] = wavread('balaclava5s.wav'); 
[Pxx,Freq] = periodogram(x,rectwin(length(x)),length(x),Fs);
plot(Freq,10*log10(Pxx))
grid on;
xlabel('Hz'); ylabel('dB/Hz');

Just

   periodogram(x,rectwin(length(x)),length(x),Fs);

produces a plot without outputting any data.

MATLAB: The resolution on the spectrogram plot is WAY too low

Experiment with more elements to your frequency vector, for example:

spectrogram(datVec,fs,[],[3:3:300],fs)

I’m not certain that will do what you want, however it’s always best to experiment.

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MATLAB: How to use periodogram

MATLAB: The resolution on the spectrogram plot is WAY too low

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