Self-reciprocity calibration for spherical transducers based on acoustic reflection of spherical shell inwall

Based on the emission of pulsed spherical acoustic waves from a spherical transducer and their reflection on a concentric spherical shell inwall,the electromechanical reciprocity theorem is applied to derive a reciprocity coefficient for the calibration of a spherical transducer in a spherical acoustic field.On top of this,a self-reciprocity calibration method using a closed spherical shell reflector is proposed to obtain the five fundamental electroacoustic parameters of the spherical transducer from a single measurement.Further,a conversion factor is given for converting the voltage sensitivity obtained by the current method to the standard sensitivity defined in plane wave fields.To determine this conversion factor,a method for measuring the scattering coefficient of the transducer is developed.Calibration of a10-mm-radius spherical transducer is performed in the frequency range 25~63 kHz.The results show that the standard uncertainty of the measured voltage sensitivity is up-bounded by 0.9 dB.