ELE201 Lab1 - lab 1 PDF

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Divya Thuremella ELE 201 Lab 1

Q1) The first method (“result = a + b;”) is the fastest, the third method (“for i = 1:length(a) result(i) = a(i) + b(i); result = zeros(1, 10000);”) is the second fastest, and the second method (“for i = 1:length(a) result(i) = a(i) + b(i);”) is the slowest. Q2) If you plot the whole signal vs time, you get a shape like a rapidly widening cone because the sine function is so close together that you can’t see the individual waves; you can just see the amplitude decreasing as an exponential of e. Q3) The ph value doesn’t affect the sound because it’s just a time shift, but the sound keeps its frequency and amplitude, and the values that matter. Q4) Respect with Fs = 66100 was my favorite because it made her sound like a chipmunk Q5) – d is the tone before you dial the numbers , b is the sound when you’ve hung up, and r is the phone ringing Q6) It’s a postage stamp, then a penny Q7) high frequency threshold is 3500, and the message is “I think that’s very clever, they’re trying to confuse us to death.” Q8) This is not what I expected; everything is constant except for 4 high points on either side of 0; the highest value of the signal is 1000 and the second highest value is at 500, which is where the frequency is at 400 and -400. Q9) The phone number is 8675309

D1) Changing the amplitude changes the loudness of the sound. Making the amplitude higher makes the sound louder, and making the amplitude smaller makes the sound softer. This is because the energy of the sound is the amplitude squared, so when the amplitude is bigger, the sound is even louder.

D2) Decreasing the sampling frequency to 1 KHz doesn’t drastically change the quality of the sound that much, but it sounds more base-y and broken up. The sound quality changes drastically at Fs = 500 Hz D3) The busy DFT of the dial tone busy signal seems to be a filled in triangle at the bottom whereas the DFT of the dial tone seems to be an outline of a triangle at the bottom. This is because the dial tone is simply a combination of two tones that vary in amplitude, whereas the busy signal is a combination of two tones that vary in amplitude plus an on an off tone that alternates between the tone and 0. D4) Bass Guitar falls into low pass range, string guitar falls into mid pass range, and the drums/cymbals fall into the high pass range. D5) The peaks stay at 1000, but the number of smaller lines around the peaks rise from 400 to 404, fall from 404 to 408, and rise again. The number of smaller lines around the peaks rise from 1000 to 1100 and fall from 1100 to 1200. 400 and 440 are special because they’re multiples of 8, (since sampling frequency is 8000 and N is 1000) and since it samples in multiples of 8, it gets exact values at 400, 404, 408,…440. D6) You see that everything is 0 except for plus or minus the frequencies (in this case, plus or minus 3 for the x axis and plus or minus 2 for the y axis). This is because the coordinates correspond to the frequencies in both directions. D7) In the time domain, it’s an image of the Chrysler building, and in the frequency domain, it’s a gradient of reds and yellows where the center is extremely red, and the outer edges are yellow. This shows that a high number of the pixels in the image have 0 frequencies (in the center), and relatively few have extreme frequencies (outer edges). D8) You can tell which frequencies are present but you can’t tell which numbers from just the graph. You need to inverse transform into time domain to be able to figure out the phone number. Therefore, you can’t visually decode the number from this plot....