---

Systems of recognition and location identification of underwater moving bodies which using acoustic waves are called sonar. Electroacoustic transducers have an important role in underwater communication systems such as Sonar. A set of electroacoustic transducers which is called sonar array, can be used for sending and receiving underwater sound. The most widely used transducer in these arrays are Tonpilz transducer. In this paper, a full simulation of Tonpilz transducer is given and the most important factors for evaluating transducer performance are checked experimentally and numerically. Also for validation of finite element model, the sample of transducer was designed and made. This transducer was tested in two methods, electrically and acoustically. Electrical behavior was tested by Impedance gain analyzer devise. Acoustic test was carried in the acoustic pool. Then the result of FEM compared with experimental results. With comparing FEM results and tested model, it is observed that the finite element model can predict electrical and acoustical behavior of Tonpilz transducer so well. Finally it is tried to improve frequency response of transducer with making changes in the structure. While the addition of damping factors can increase frequency bandwidth.

---

Knowledge of broadband transducers is a new technology in the field of sonar science. Considering that Iran has sea water resources, its importance becomes more and more. In this article, after studying the performance of the kinds of transducers in the field of sonar transducers, a proper broadband transducer with the specific impedance and acoustical characteristics that can send and receive signals, is designed, simulated, fabricated and tested. At first, overall dimension of a broadband transducer with lumped parameter model and electrical equivalent circuit model was approximated and then, with increasing the degrees of freedom of analytical models, all characteristics of the optimum transducer parts were obtained in order to have a large bandwidth. By using a finite element software (COMSOL Multiphysics), the designed model was simulated and the obtained results have been compared with analytical design solution. Finally, the transducer was fabricated and tested in order to the modeled and simulated data be validated with practical ones. The obtained experimental results showed that the simulation with COMSOL Multiphysics can predict the resonance frequency and maximum transmitting voltage response (TVR) of the broad bandwidth transducer with a reasonable precision. The prediction error of resonance frequency and maximum TVR by COMSOL is 3.8% and 5.7%, respectively. The use of lumped parameter and electrical equivalent circuit models, however, gives an initial approximation for transducer dimensions, but in determination of the resonance frequency and the frequency of maximum TVR has a higher error in comparison with the finite element method.