1. Please generate a sine waveform with input signal frequency 10kHz and sampling frequency 500kHz. The signal lasts 5 cycles. a. If change the sampling frequency to 15kHz, Plot the signal with the original waveform. b. If change the sampling frequency to 30kHz, Plot the signal with the original waveform. c. If change the sampling frequency to 50kHz, Plot the signal with the original waveform. d. If the sampling frequency to 50kHz, please plot the fft of the signal. Please also find the frequency of the signal on plot.

2. Read the watchdog.wav file in matlab. a. Find out the sampling frequency of the sound file. b. Play the sound with different sampling frequencies. Discuss how the voice changes. c. Calculate the RMS of the sound signal in decibels (dB). d. Generate a Gaussian noise with mean = 0; std = 1; and plot the histogram of noise. e. Regenerate a Gaussian noise so that the SNR is 12dB. f. Add noise to the original signal and plot the new signal watchdog_new.wav.

3. Design a filter to move out the noise. a. Play the sound and plot the spectrum of the watchdog_new.wav. b. Design a bandpass filter. (hint: use butter(*), try different values of variables and find the combination that works well) c. Filter the signal and plot it. d. Play the filtered signal. Does it sound better?