Question

MATLAB FIR filter design.

The audio file, covering the frequency range of roughly 0 to 3000 Hz, is very badly corrupted with high?level noise. Your problem is to design a digital filter that will sufficiently attenuate the noise so that the audio speech is intelligible. (sorry but chegg doesn't allow me to attach the wav file)

Here is the design template:

clear, clc      % clear all variables

%%  Read in the noisy audio signal from the file 'CapnJ.wav' using audioread function
[Signal_Noisy, Fs] = audioread('CapnJ.wav');
Signal_Noisy = Signal_Noisy'; % Change to column vector
N = length(Signal_Noisy);
Index = 0:N-1;

%%  Play the noisy audio signal using sound function
sound(Signal_Noisy, Fs), % Play the "Noisy" audio signal

%% Plot the time-domain noisy signal 
figure(1), clf
subplot(2,1,1)
plot(Index, Signal_Noisy)
ylabel('Orig. Time Sig. Amp.'),
xlabel('Time (Samples)'),
grid on, zoom on

%% Obtain and plot the DTFT magnitude of the noisy signal 
% You can use FFT with a very large number of points
% Plot the normalized magnitude in dB (i.e., 20*log10(mag/max(mag))
% Use Hz for the horizontal frequency axis (based on Fs sampling rate
% obtained above)
% Use proper axis limits for your plot



%%  Using fir1 function, design a lowpass FIR filter
% You need to select your filter order as well as the desired cut-off
% frequency. 
% For cut-off, try a few values in 2-4KHz range.
% Play with both cut-off and the filter order till you can properly hear and understand the spoken words.  
% Remember that the cut-off frequency input to fir1 is 0<Wn<1 with 1
% corresponding to the Nyquist rate (i.e., Fs/2 Hz or pi rad/sample)
F_cutoff = []; % Lowpass filter cutoff freq in Hz
B = fir1([],[]); % Simple lowpass FIR coeffs


%% Obtain and plot the filter normalized mag response
% Again, you can use FFT with a large number of points





%%  Lowpass filter the "Signal_Noisy" using the filter function and the filter you designed above 




%% Obtain and plot the normalized DTFT mag of your filtered signal

                

%% Play the reduced-noise sound using the sound function

Answer 1