About how to extract a speech signal's envelope

The above just gives the magnitude squared of each of the waveform values and that is not the envelope. At least probably not in the sense you mean envelope. To illustrate how the Hilbert transform does indeed extract the envelope, I'll give you a simple example with an AM-modulated wave.

    Fs = 1000;
    t = 0:0.001:1-0.001;
    % 250-Hz sine wave modulated at 10 Hz
    x = [1+cos(2*pi*10*t)].*cos(2*pi*250*t);
    y = hilbert(x);
    plot(t,x,'k'); hold on;
    plot(t,abs(y),'b','linewidth',2);
    plot(t,-abs(y),'b','linewidth',2);

If you know zoom in on parts of the waveform, you'll clearly see how the modulus of the analytic signal yields the envelope. Specifically, you see that the envelope oscillates at 10 Hz.

    set(gca,'xlim',[0.05 0.35]);
    set(gca,'ylim',[-2 2])

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Eason 2013-2-18

Hi King,

Thanks for your answer, I use the code

>> y=wavread('h_006.wav');

>> x=hilbert(y);

>> upenv=abs(x);

>> lowenv=-abs(x);

>> plot(y);hold on;plot(upenv,'r');plot(lowenv,'r');

The result as figure.

And then there has another question, I need to create a 500 Hz sine wave which has same length and sampling rate as my speech file. And it also need to has same envelope of my speech file.

Fs=44100;%the sampling rate of speech file

dur=2.5;%the length of speech file

t=[0:1/Fs:dur-1/Fs];%time vector

freq=500;%sine wave's frequency

sin_wave=0.5*sin(2*pi*freq*t);%create sine wave

The code above was used to create a 500 Hz sine wave which has 2.5 sec long, sampling rate 44100 Hz, is that correct?

And how can I modulation sin_wave's envelope that was same as speech?

Thanks

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Answer 2

Wayne King 2013-2-18

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/63935-about-how-to-extract-a-speech-signal-s-envelope#answer_75506

在 MATLAB Online 中打开

Yes, basically, although, I'm not sure why you set the amplitude equal to 0.5

For example:

    load mtlb;
    analmtlb = hilbert(mtlb);
    t = 0:1/Fs:length(mtlb)*(1/Fs)-1/Fs;
    x = cos(2*pi*500*t);
    y = abs(analmtlb).*x';
    soundsc(y,Fs)