Abstract: A pulsator for a jet resonator finding particular value and utility in rodent control while maintaining and achieving improved effectiveness together with built-in safe guards against accidental detrimental or fatal effects of ultrasonic sound on human beings while maintaining a low cost of parts and production thereby making improved pest control available to the broad populous, the pulsator including an elongated upright tube having a jet in a lower-end opening and having a ball-receiving seat structure circumscribing and as a part of the upper outlet opening, with a metal ball of smaller size than the cross-section of the elongated space defined in the tube such that the ball is tossed reciprocatingly upwardly in the tube without unduly limiting fluid stream when the ball is tossed upwardly but retarding the flow of the stream as the ball falls downwardly toward the open nozzle end of the lower-end jet which nozzle preferably projects upwardly into the space for a minor distance, pressure of the stream of