Abstract: In the paper, a perforated plate impedance transformer of piezoelectric transducer is investigated. The acoustic behaviour of the perforation is taken to be equivalent to that of a closed tube of length equal to the thickness of the plate with end corrections. Formulas of the resonance frequency, quality factor of the transformer and the relative radiation efficiency of the transducer are derived rigorously. For a composite piezoelectric transducer with or without impedance transformer, experimental results are given and discussed. <
It is shown that a proper transformer operating under resonance condition will increase the relative radiation efficiency of the transducer 12 dB approximately without changing the quality factor and directive property of the system. Experimental results are in good agreement with theoretical values.