ECE 425/525 Digital Signal Processing

Posted 2021-11-29 blogy

ECE 425/525 Digital Signal Processing
Spring 2019
Dept. of Electrical and Computer Engineering Miami University
1
Homework 11 Assignment
Weights: 60pts
Due Date: May 10, 2019.
Turn in Method: Turn in your report with your Matlab? program and other supporting materials
listed at the end of this handout via Canvas by the midnight of May 10, 2019.
Project Description:
In this project, you will use two bandstop IIR filters to filter out noise.
Conduct the following task.
1. Download the test wave file, ‘test3.wav’, from the Canvas.
2. Use Matlab audioread command (or other Matlab command) to find out the sampling
frequency of the wave file and save the voice to x[k].
3. Play x[k] with Matlab?.
4. Get the magnitude and phase spectra of x[k] with fft command and plot them. Since the
length of x[k] can be too long, you might want to specify the size of FFT output. Refer to
Matlab help menu on how to specify the length of FFT result. (Note: x-axis unit needs to
be Hz and y-axis unit needs to be dB (magnitude spectrum) or radian (phase spectrum))
a. Since fft(x) will generate a complex valued array, you need to use Matlab
commands ‘abs’ and ‘angle’ to get magnitude and phase spectrum of your
signal.
b. You only need to plot the first-half of you FFT result. Why?
5. The signal (x[k]) is corrupted by two narrowband interferences. Based on the magnitude
spectrum you obtain in step 4, design two bandstop digital IIR filters so you can use them
sequentially to remove these interferences.
6. Plot the frequency response spectra of the bandstop filters with freqz command (x-axis
unit: Hz)

代写ECE 425/525作业、代做Digital Signal Processing作业
7. Apply your two bandstop filters in sequence to filter the x[k] and save your result into y[k].
8. Play y[k].
9. Get the magnitude and phase spectra of y[k] with fft command and plot them. (Note: xaxis
unit needs to be Hz and y-axis unit needs to be dB (magnitude spectrum) or radian
(phase spectrum))
10. Save y[k] into a wav format file.
Submission Request
You need to turn in the followings:
(1) Matlab? codes
(2) The filtered voice in wav format
(3) The frequency response spectra of two bandstop filters
ECE 425/525 Digital Signal Processing
Spring 2019
Dept. of Electrical and Computer Engineering Miami University
2
(4) The magnitude and phase spectra of x[k] and y[k].
Matlab? Commands You Might Need
audioplayer, play, wavread, sound, xcorr, zeros, ones, fft, ifft, abs, angle, unwrap, real,
imag, freqz, freqzplot, filter, subplot, buttord, cheb1ord, cheb2ord, ellipord, butter, cheby1,
cheby2, ellip, lp2bp, bilinear.
Note: These commands are provided for you convenience, you should not assume that they are
the only commands you need for this assignment.
Example Matlab Program for filter design (Read Matlab help for ellipord and ellip)
Fs=8000;
Wp1=[300 3000];
Ws1=[500 2000];
[N, Wp] = ellipord(Wp1/(Fs/2), Ws1/(Fs/2), 0.5, 40)
[B1,A1] = ellip(N,0.5, 40,Wp,‘stop‘);
freqz(B1,A1,1024,Fs);

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