The weakly electric fish use their electric organ discharge (EOD) and electroreceptors to identify their prey, explore in their surrounding environment, and communicate with their members in the same species. They are specialized in active electrolocation. They can detect the distortion of the self-generated electric field, which is caused by a target object. There are two types of electric signals, wave-type and pulsetype, that the weakly electric fish can generate. In this paper, we suggest that periodic EOD signals are helpful to extract localization features from noisy electrosensory signals. The cross-correlation between an efference copy signal and the sensory afferent signals in the waveform can produce accurate relative slope in noisy environment. This process has two-phase filtering. The noise-filtering with cross-correlation with respect to the temporal axis and additional filtering with respect to rostrocaudal spatial axis can effectively remove noise, and thus this process provides accurate information of the distance of a target object.