Publisher Summary This chapter discusses the method of distinguishing the noises accumulated in the sensors at the time of radiation measurement from the signals. The study is confined to the noises and signals observed by the sensors. The types of these sensors are NaI scintillator, plastic scintillator, and Geiger–Mueller counter tube. As for the signal observed in each sensor, the waveform of voltage above a certain level is counted as a pulse signal. The voltage levels to be counted are given in every characteristic of sensor type, with the minimum voltage being NaI scintillator 0.3 V. More than 66.7% (0.2 V) of this voltage is subjected to analysis. There is no theoretical ground for determining the minimum voltage as a subject of analysis; the decision has been made entirely on the basis of experience. Furthermore, because voltages above 5.0 V are not feasible, any voltage above this level is discarded as a pulse signal. As for the negative voltage, it is not counted as a pulse signal, and therefore it is exempted from detailed study. However, signals below -0.2 V level will undergo a brief analysis to get their existence made clear. The surge waveform with pulse width below 10 ns is also excluded from the subject of analysis, because the counter fails to react to such short-time pulse signals because of their frequency characteristics.