Directivity and effective diameter measurement method of the hydrophone in ultrasound field

The directivity model of hydrophone describes the frequency response of the hydrophone at different incident angles, which can be used for estimation of the effective diameter of the hydrophone. This parameter is very important because of the correction of the spatial average effect and the accurate measurement of the sound field parameters. At present, the nominal diameter of most commercial hydrophones is difficult to meet the requirement that the effective radius of hydrophone should be less than or equal to 1 / 4 of the acoustic wave wavelength, which may result in large errors because of spatial averaging. To solve this problem, this paper studies an effective diameter measurement method based on three kinds of hydrophone directivity models. In this method, the received signals of the hydrophone at different angles are measured, and the directional response model of hydrophone is established by least square method according to rigid baffle (RB), un-baffled (UB) and soft baffle (SB) model. The influence of directional models on effective diameter measurement is evaluated at different frequencies. The experimental results show that the directivity response data of hydrophone are not only matched with one model at different frequencies, but the directivity model closest to the data points should be selected to estimate the effective diameter of hydrophone.