The authors have observed a relationship between the waveforms of electromagnetic noise and a change of surface for arc discharges of opening Cu-C and Ag-Pd material electric contacts. In the case of Cu-C electrodes, the waveforms of electromagnetic noise and the changes of the electrode surface are affected by electric current polarity. By classification of the noise waveform pattern, the authors showed a close relationship between noise and change of surface. The noise level of Pd(anode)-Ag(cathode) increases in the middle of arc duration, and decreases in the latter half. In high noise level conditions, a change of color on the surfaces of both electrodes was found for Pd(anode)-Ag(cathode). The pattern of noise occurrence depends mainly on the cathode material.