Noise from surroundings in DSP

hi,

     I am working on C5505 ECG MDK. When I acquire ECG signals I come across with lots of noise at frequencies beyond my LPF @ 40 Hz.

    I was wondering if there is a case of addition of noise from surroundings. I am thinking of building a " Metal box" where i would put the dsp kit, fully enclosed in it and then ground it.

   Would that be effective???

               Thanks.