In a signal transmission medium such as an ac power line, impulse noise in the line may be dealt with by detecting impulse noise in the transmission medium, determining whether the impulse noise is periodic or complex, and, at least approximately, correlating the time at which periodic impulse noise occurs in the transmission medium to the phase of the ac power line frequency. One or more noise mitigation techniques may be applied with respect to the impulse noise. Methods also include predicting at least the approximate time of the next periodic noise impulse, and at least its approximate occurrence in the phase of the ac power line frequency. Methods also address impulse noise in complex impulse conditions.