matlab code for digital filter design to remove gaussian noise from a speech signal ?

please give me matlab code for digital filter design to remove gaussian noise from a speech signal ? I have tried as following

Fs = 12000;
x =wavread('d:/assignment_1/speech_safety_-2db_snr.wav');
% plotting original sound signal
figure(1)
%subplot(2,1,1)
plot(x)
xlabel('time');ylabel('Amplitude');title('Original Sound Signal')
% Specifying the filter
%'Fp,Fst,Ap,Ast' (passband frequency, stopband frequency, passband ripple, stopband attenuation)
hlpf = fdesign.lowpass('Fp,Fst,Ap,Ast',4.0e3,5.5e3,01,50,Fs);
% Designing the filter
D = design(hlpf);
% Applying the filter
y = filter(D,x);
% Getting sound after sampling and Filteration
sound(y,Fs)
% plotting modified sound signal
% noise is removed after filteration
figure(2)
%subplot(2,1,2)
plot(y)
xlabel('time');ylabel('Amplitude');title('modified sound signal')

[nazifa nawar]

Did we use wavelet filter? Or what type of filter did we use?

Answer 1

[UA]

Don't use waveread. use audioread.

Answer 2

[Wayne King]

So what is not working about the above code? You can probably push the passband frequency a bit lower without affect intelligibility, try 3000, so maybe a design like:

hlpf = fdesign.lowpass('Fp,Fst,Ap,Ast',3.0e3,3.5e3,0.5,50,Fs);

You have to understand that if you are talking about white Gaussian noise that has power at all frequencies so you cannot filter out that noise completely without removing the signal as well.