LAB ASSIGNMENT 13 (due 05/07/14)
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(20 pts.)


The signal in the file NOISY_CLIP_HW.WAV is a music clip corrupted with
noise. The objective of this assignment is to denoise it.

i)	Use WAVREAD to import the noisy audio signal as vector x.  What
	is the sampling rate Fs? Listen to x using SOUNDSC.

ii)	Use the SPECTROGRAM function and a mesh plot (as in Lab 13, item 5)
	to determine the frequency bands occupied by the clean signal and 
	the noise.  What type of filter (lowpass or highpass) will remove
	the noise, and what should the filter frequency parameters roughly 
	be?

iii)	Using FDATOOL, design a filter inline with the following constraints,
	and import its coefficient vector into your workspace and name it bb:

	  Order: 60, i.e., 61 filter coefficients will be generated.

	  Transition bandwidth: wstop and wpass should be selected so as to
	  satisfy |wstop-wpass| = 0.05 in normalized units (i.e., 0.05*pi
	  rad/sample)

	  Passband ripple and stopband attenuation tradeoff:  If the filter
	  obtained with the default weights (1.0 and 1.0) does not produce
	  a satisfactory result in iv) below, repeat with a different weight
	  ratio until the playback sounds right.

iv)	Use the FILTER function to compute the filter output (for input x)
	and play it back using SOUNDSC (and the right value for Fs).
	Verify that your result is satisfactory and write the clean (denoised)
	audio signal into lastname_labhw_13.wav.

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Submit (use exact file names as shown):

lastname_labhw_13.m

	Should include: the value of Fs, the type of filter used, its
	parameters (passband, stopband, ripple and attenuation).

	Also, paste the entire coefficient vector bb as a column vector
	using FORMAT LONG.

	Useful comments should be given.

lastname_labhw_13.wav

	The clean (denoised) audio signal.

The zip or rar package should be named as lastname_labhw_13.zip / .rar, and 
should be uploaded from the upload link on the course lab web page 
<http://terpconnect.umd.edu/~jzsimon/enee222/lab.html>, or if not possible, 
emailed to enee222S2013@gmail.com.