Development And Application Of Multi-frequency Resonant Cavity Hydrophone

Applications such as underwater acoustic detection,acoustic leak detection,underwater acoustic communication,etc.require hydrophones to have high sensitivity at narrowband operating frequencies.However,at present,hydrophones are mostly broadband,and the manufacturing process for increasing the sensitivity of the overall frequency band is usually very costly and complicated.Therefore,there is a need for a highly sensitive hydrophone that can easily adjust the operating frequency band.In this paper,a multi-frequency resonant cavity hydrophone is proposed based on the principle of acoustic resonance of closed air cavity of inside rigid wall.The main works are as follows:(1)The relationship between the radius of the sealed spherical cavity and the characteristic frequency of any a certain modal is derived.According to the closed cavity resonance principle,a spherical cavity hydrophone is designed.The structure of the hydrophone is formed by placing a tiny microphone inside the closed air cavity.Through finite element simulation,it is proved that the frequency response characteristic peak of the hydrophone is only determined by the air cavity of the hydrophone,it is found that the sound field distribution of hydrophones with different characteristic modes is different,and the microphone position affects the sensitivity of the hydrophone at the resonance frequency.The experimental platform was built to verify the simulation results.(2)The directivity curves at the characteristic frequency of the hydrophone,the sound permeability of the spherical shell and the receiving signal phase are analyzed;the simulation and experiments shows that the directivity curve of the hydrophone is different in different modes,the material and thickness of the spherical shell affect the sensitivity of the hydrophone,and the phase of the hydrophone receiving signal to the acoustic part is stable and regular.Compared with the standard hydrophone,the sensitivity of the proposed hydrophone is 10 times higher at the characteristic frequency,and the signal-to-noise ratio is also higher.(3)The hydrophone is applied to the water-filled pipeline leak detection and underwater acoustic ranging.The detection array of this hydrophone is designed and constructed to try to realize the imaging of the sound source.However,due to the high Q value of the hydrophone and the residual vibration disturbing the phase,the imaging resolution is lower than the theoretical calculation value.Efforts on improving the phase stability should be made in the future work.