Abstract: A method of detecting break-ins in an intrusion-detection barrier which includes an array of sensors in signal communication with one another and connected to a control unit may include: calibrating at least one of the sensors of the array, the calibrating including: applying mechanical stress to the barrier to cause the barrier to resonate at characteristic frequencies; and creating a digital filter, for the at least one of the sensors, configured to identify the characteristic frequencies; and/or detecting external forcing applied to the barrier, the external forcing having oscillation-forcing frequencies, the detecting including: applying the filter to identify the oscillation-forcing frequencies applied to the barrier, and discriminating the oscillation-forcing frequencies from the characteristic frequencies of the barrier; selecting at least one energy threshold value; calculating an energy value for each of the oscillation-forcing frequencies; and comparing each of the energy values with the at least on