This paper reports on a signal processing using maximum value, that is, we consider maximum value, when we calculate the probability density (PD) and the exceedance probability. We purpose that maximum value of many samples is useful to emphasize large amplitude of rare phenomena. This signal processing gives us a lot of information. For example, when the ratio generating an impulsive interference is examined on communication channel, the impulsive component is emphasized in PD or exceedance probability. Finally we measured noises and signals on the band (940MHz) of PDC (Personal Digital Cellular) in Japan. Then the experimental results show that we are able to recognize impulsive-type noise well.