Investigation of an air-coupled transducer with a closed-cell material matching strategy and an optimization design considering the electrical input impedance.

A high sensitivity air-coupled transducer with a hollow polymer microsphere filled epoxy resin matching layer is investigated. A new closed-cell porous material is introduced and a new acoustic impedance matching solution is discussed. An electrical impedance matching and parameter optimization method based on artificial bee colony algorithm is investigated which can significantly improve the sensitivity on the basis of acoustic impedance matching approach. The diameter of the piezoelectric plate and the thickness of the acoustic matching layer play an important role in this method. Experimental results are given, illustrating a 20.9 dB sensitivity enhancement by applying our acoustic impedance matching method, and an 8.4 dB additional sensitivity enhancement by applying our electrical impedance matching and parameter optimization method.