Filter to Cancel Noise

I need help in cancelling microphone noise... im just not sure whether or not i should use a lowpass filter... can anyone give me help?

i want to use the filter command along with fir1... but i dont understand how to use them... i couldnt figure out how to customize the filter coefficients that would effectively remove the noise in our recorded signal... am i going in the right direction?

any hepl would be greatly appreciated... our thesis is in dire need of a digital filter... i know this is quite simple but the logic just simply doesnt want to see eye to eye with me...