an acoustic projector wherein a unitary acoustic resonator produces active sonar signals in more than one frequency band . the double - slotted resonator is coupled to a transducer which is capable of exciting the resonator in two , distinct , volumetric modes of vibration using two asymmetric , generally arcuate vibrating members . transduction techniques can include variable reluctance or piezoceramic transduction . internal cavity pressure release may be achieved by bladders , compliant tubes , and the like .