Design of transducers for multiple-frequency operation

Use is frequently made of a λ/4 mechanical impedance matching section on the face of a transducer to improve coupling of acoustic energy from the transducer into the medium and to increase operating bandwidth of the transducer. It is shown that the addition of this matching section introduces additional, higher-frequency, resonances in the transducer. By proper design of the transducer and matching section, the resonances can be independently controlled as to frequency and operating bandwidth so as to result in a device capable of operation at multiple, widely-spaced, frequencies.