How to filter frequencies from a wav file

Hi, I have to clear the noise from a wav file using the Fourier Transform. My teacher gave me a code that obtains the fast Fourier Transform. I need to clear the noise of the signal and save the file without noise but I have no idea how to do that.

Here is my code:

clear all; clc
[song,Fs,bits] = wavread('vagon.wav');
%Check channels and convert to mono
if size(song,2)==2
y=zeros(size(song,1),1);
y(:)=0.5*(song(:,1)+song(:,2));
else
y=song;
end

Nsamps = length(y);
t = (1/Fs)*(1:Nsamps);         %Prepare time data for plot

sound(song,Fs)

%Do Fourier Transform
yFT = fft(y);

% %Prepare plot FT
y_fft = abs(yFT);            %Retain Magnitude
y_fft = y_fft(1:floor(Nsamps/2));      %Discard Half of Points
f = Fs*(0:Nsamps/2-1)/Nsamps;   %Prepare freq data for plot

%Plot Sound File in Time Domain
figure
plot(t, y)
xlabel('Time (s)')
ylabel('Amplitude')

%Plot Sound File in Frequency Domain
figure
plot(f, y_fft)
xlim([0 20000])
B=1;
if(A>1) B=A; end
ylim([0 max(y_fft)*B])
xlabel('Frequency (Hz)')
ylabel('Amplitude')

I hope you can help me, I don't want you to do my homework, I just want to know a way to do it, I'm new to Matlab so I don't know how does it work.

Answer 1

[Star Strider]

I encourage you to read through the documentation on filters and related functions in the Signal Processing Toolbox. I summarised my filter design procedure here. That should help you get started.