The Study Of Vector Hydrophone's Design And Measurement In 10-100Hz

Vector hydrophone can measure pressure and particle velocity at the same location and the same time in an underwater sound field, and then the sound field message can be described briefly. Because of the demand of remote probing techniques and low noise measurement, the development of vector hydrophone trend to low frequency. The advantage of moving coil velocity transducer in low frequency offers a valuable reference. As we know, the sensitivity of vector hydrophone by mounting a piezoelectric accelerometer inside it can reduce as the frequency debasing. But the sensitivity of velocity vector hydrophone can keep the same. So this vector hydrophone can get much higher sensitivity in low frequency. In this paper, the lowest frequency of the vector hydrophone can be 10Hz because of the use of moving coil velocity transducer.As we know, vector hydrophone's measurement in low frequency especially in 10～100Hz is very difficult. Theory of standing-wave tube shows that vector hydrophone can be measured in standing-wave tube. Many experiments show that piezoelectric emitter can't be used to measure low frequency vector hydrophone in standing-wave tube because of its low signal-to-noise ratio in 10～100Hz. But low frequency emitter with the thin board as its radiant surface can supply enough signal-to-noise ratio in standing-wave tube in 10～100Hz. ANSYS software can be used to emulate the sound field in the standing-wave tube.Sound field in standing-wave tube has to be calibrated before measuring vector hydrophone. The value of flat surface pressure fluctuation and longitudinal pressure variation has to be small enough comparing with the theory value. And the error has to be in the permissive error range. In order to prove that the standing-wave tube can be used to measure vector hydrophone in 10～100Hz, several low frequency vector hydrophones have been measured in the tube.