Đồ Án Lab 3 IIR Filter Design ( code đầy đủ)

1. Goals
The goal of this lab is to demonstrate a basic application of Notch IIR filter, which is rejecting the hum noise. You will need to design several IIR filters to satisfy the given specifications.
2. Lab resource
- PC with Matlab
- Sound card installed in PC
- Headphone set
3. Notch filter design (50 points)
3.1. IntroductionYou may have noticed that occasionally inexpensive audio equipment generates a humming sound. This humming is produced by the 60Hz AC electrical power "leaking" into the audio signal processing. This hum is at such low frequency that usually it is not annoying. On most aircraft, the electrical power is at 400Hz and when 400Hz "leaks" into audio signals, the result is very annoying. In this problem you will try to eliminate the 400Hz hum from a digital signal, but of course you will try to accomplish this without eliminating much of the desired signal.
An example of a signal with and without the 400Hz hum is in the files with_hum.wav and without_hum.wav, respectively. These are sampled versions of the audio signal, where the audio was sampled Fs = 8000 times a second. You can load these files to Matlab arrays by using wavread function. In this section, you will design a notch filter, and then apply the notch filter to eliminate the annoying hum from the audio signal[1].
3.2. BackgroundNotch filter is a filter that can reject a narrow frequency band and leave the rest of spectrum little changed. The frequency response of a single notch filter and its transfer function are shown below [2]: