A hammer includes a jacket having an inner chamber; an inlet circuit for the entry of compressed air, and an outlet circuit for the exit of compressed air. The hammer includes a motion mechanism, for generating vibratory motion under the action of compressed air; and a punch or beater, connected to the motion mechanism, for contacting the casting to be de-cored, forming a first end of the hammer. The hammer has a measurement circuit measuring the oscillation frequency of the motion circuit. The measurement circuit includes a sensor for measuring the oscillation frequency of the motion circuit; a processing circuit, enclosed in a protective casing, for receiving electric signals transmitted by the sensor, and a communication line for conducting electric signals from and/or to the measurement circuit. The jacket includes a housing formed in the outer surface of the jacket, such that it incorporating the measurement circuit protective casing.