MATLAB

3.3 Spectrogram: Section Length and Negative Frequency In this part, you must display the spectrogram of the signal synthesized in the previous section with different parameters. Remember that the spectrogram displays an image that shows the frequency content of the synthesized time signal. Its horizontal axis is time and its vertical axis is frequency. Use the function specgram (xx, 512, fs)The second argument is the window length which could be varied to get different looking spectrograms. The spectrogram is able to "see" the separate spectrum lines with a longer window length, e.g., 1024 or 2048.4 In order to see a typical spectrogram, run the following code: fs-8000; tt-0:1/fs:0.5xx - cos (4000 pi tt); spectrogram(xx, 1024,,3,s,'yaxis or, if you are using plotspec(xx,fs) colorbar tt-0:1/fs:0.5; yy-xx+cos(1600 pitt) plotspec(yy,fs,1024): colorbar Notice that the spectrogram image now contains two horizontal line at the correct frequencies of the sinu soids similar to what was displayed in Fig. 1. To obtain a spectrogram with negative frequencies, try the following plotspec (yy j 1e-9,fs,1024); colorbar To obtain a spectrogram with a different section length, try the following plotapec(yyj1-9,s, 128); colorbar For this verification, show the spectrogram features with negative frequencies and different section lengths to your lab instructors. You can also use the spectrogram of the DTMF digit 8 obtained in the previous lab. Instructor Verification (separate page)