Abstract: A wideband transducer for sound tube system is presented in this paper,which combines longitudinal transducer and ClassⅣflexural transducer to improve the performance at low frequency and broaden the working band.The equivalent electrical circuit is obtained by which the coupling between longitudinal transducer and flexural transducer is analyzed.A prototype is fabricated after analyzing the electro-acoustic performances by Finite Element Method.The standing wave in the sound tube stimulated by this transducer has been studied and the absorbing coefficients of two samples of acoustic materials are measured using this sound tube,which shows that the transducer can meet the requirements of measuring acoustic materials,especially with the wide working band ranging from 1.4 kHz to 23 kHz.