An arc discharge generated by breaking electrical contact is considered as a main source of an undesired electromagnetic (EM) noise. The current and radiation noise from 30M to 3G Hz generated by slowly breaking silver compound contacts were investigated experimentally in order to clarify mechanisms of generation of the EM noise. It was demonstrated that frequency responses of the current and radiation noise are corresponding to circuit admittance and radiation efficiency of experimental setup. Current noise at lower frequencies band (10MHz) was largest in the measured frequency range. Although current noise above 100MHz decreases, radiation noise increases as the frequency increases. It was demonstrated that even if current noise at GHz band is very small, slight current noise can cause large radiation noise because of the high radiation efficiency. Time-frequency domain characteristics of current noise also were studied in order to clarify the correspondence of noise generation to contact breaking phenomena. The peaks of current noise at 10MHz band arise when immediately after the initiation of arc discharge and transition from metallic phase to gaseous phase. The peak of current noise above 100MHz arises when just after the initiation of arc discharge. This study is a basic consideration to realize methods for good electromagnetic compatibility design for electrical contacts.