Execute the provided MATLAB program dsb_sc_example. Note that this program also calls MATLAB functions that were provided in Module 2, so you need to have these available as well. This program loads a built-in sound file of a train whistle which lasts approximately 1.6 seconds. The program plays the train whistle through the speakers. You should hear two bursts, each of which sounds like a musical chord (this is actually a slightly out-of-tune D minor chord for you musicians). The program then displays the time function and the frequency domain approximation of the signal in figure 1. The train whistle is then upsampled to a higher sampling rate and replayed. The result is shown in figure 2. The signal is then modulated to a carrier using DSB-SC (figure 3), demodulated using the same carrier (figure 4), and filtered (figure 5). The demodulated and filtered signal is played through the speakers again. Do you hear a difference? Use the zoom, pan, and cursor controls on the graphics windows to answer the following questions: What are the frequencies of the three tones in the original train whistle signal? What is the carrier frequency of the modulator signal? What are the frequencies of the USB and LSB tones in the modulated signal? What do you observe in the demodulated signal before filtering? What differences do you observe between the original signal and the final filtered, demodulated signal? In particular, what is the ratio of the amplitudes of the time domain signal? Explain. What MATLAB command is used to upsample the signal in this program? What MATLAB command is used to filter the demodulated signal? Now execute the provided MATLAB program am_example. This program performs the same operations, using AM modulation rather than DSB-SC. Again, use the zoom, pan, and cursor controls on the graphics windows to answer the following questions: What are the frequencies of the three tones in the original train whistle signal? What is the carrier frequency of the modulator signal? What are the frequencies of the USB and LSB tones in the modulated signal? What do you observe in the demodulated signal before filtering? What differences do you observe between the original signal and the final filtered, demodulated signal? In particular, what is the ratio of the amplitudes of the time domain signal? Explain. How is an ideal diode approximated in the MATLAB code? How is the DC value of the demodulated signal removed? In the modulated signal, what are the amplitudes of the frequency tones? What is the amplitude of the carrier signal? What is the significance of the fact that a carrier is not required for AM demodulation? You are also encouraged to single step through the details of the code, noting how the signals are created and modified. MATLAB has a number of other interesting sound files that you can play with in addition to train. These include chirp, gong, laughter, splat, and handel. You can also easily change parameters, such as the carrier frequency or the modulation index within the code.