A method is designed for emphasizing a howling frequency component of a sound signal observed in an acoustic feedback system during an observation period having a predetermined length. The method is carried out by the steps of successively sampling the sound signal from the acoustic feedback system to provide a running set of samples of the sound signal during the observation period such that a total number of the samples in the running set increments each time one or more of new sample is added to the running set until the total number of the samples corresponds to the predetermined length of the observation period, recurrently calculating a running frequency characteristic of the sound signal on a common frequency axis for the observation period from the running set of the samples each time one ore more of new sample is added to the running set, and accumulating the recurrently calculated running frequency characteristics on the common frequency axis so as to emphasize a howling frequency component contained in the sound signal.