Hongjuan Chen

Research on calibrating vector hydrophones in small water tank

The hydrophone calibration system in a small water tank has broad application prospects. This paper studies some theory evidence of the practicability of the hydrophone calibration system in a small water tank. Simulation of the sound field in a small water tank shows the distribution of the acoustic field there in. An experiment is conducted to compare a vector hydrophone with a standard hydrophone, and, calibrate the sensitivity of the vector hydrophone, and thence calibrate the directivity pattern. The frequency is ranged from 50Hz to 1000Hz. Finally, the paper compared the result of calibration with the theoretical sensitivity and directivity pattern.

Design of underwater particle velocity pickup sensor

Addressing the subject of a suspended co-oscillating vector hydrophone application platform, a new sound wave receiving theory model of underwater particle velocity pickup sensor was established. Based on the study of the inner sound field of an elastic sphere vibrating freely under the action of sound waves in theory, the influence of material and geometry parameters on the frequency response of particle velocity has been analyzed. According to the results of parameter optimization and taking into account engineering needs, two samples of one-dimensional particle velocity pickup sensor have been designed and tested. By comparing the results of sensitivity tested in a calibration device, the general rules of theoretical analysis have been verified. The theory and experiments confirmed the feasibility of particle velocity pickup sensors in engineering applications.

Instrumentation for underwater acoustic intensity measurement

Acoustic intensity is one of the most important quantities in underwater acoustics. The conventional way of obtaining the acoustic intensity is by using two microphones as an intensity probe. However, the finite difference approximation will bring errors to the intensity calculation. Moreover, few publications mention instrumentation for measuring underwater acoustic intensity, in spite of intensity measurements being more meaningful for underwater usage. The instrumentation for measuring underwater acoustic intensity is presented in this paper: the intensity probe is a pressure-acceleration based vector hydrophone from which the particle velocity can be obtained directly. Therefore, the errors due to finite difference approximation will be eliminated by using the vector hydrophone. To test the instrumentation, the acoustic intensity is measured in a standing wave tube. To measure the self-noise of the intensity probe, a facility called Self-Noise Evaluation System is also presented in this paper.

Analysis of the characteristic of vector hydrophone's inner sound field

Aiming at spherical co-oscillating vector hydrophone, this paper considered it as an elastic sphere vibrating freely underwater, and analyzed the characteristic of vector hydrophones inner sound field, due to an incident train of plane wave. This paper used the finite element simulation software to analyze the vibration modes of elastic sphere, and summarized the influence of these results on the receptivity of vector hydrophone. These analysis results have certain reference function for the optimization of design of new type vector hydrophone.

Simulation study on very low frequency vector hydrophoe application platform's suspension system

Aiming at very low frequency vector hydrophone application platform, this paper simulated and analyzed its performance by using finite element analysis software. The result of simulation indicates that the dynamic performance of suspension system obviously effect the vector hydrophones acoustic performance. By comparing to the experimental results, this paper realized the anticipation of lower limit frequency of co-oscillating vector hydrophone. On this basis, this paper designed and simulated a new structural model of vector hydrophone. The analysis results have reference value for engineering application of vector hydrophone.

Study on a high sensitivity tangential polarized acoustic-pressure hydrophone

In this paper, the cylindrical PZT acoustic-pressure hydrophone has been researched. Based on the analysis of cylindrical piezoelectric ceramic pipe free vibration and statically receiver theory, the sensitivity of hydrophones covered with plate, whose have three different polarization models, can be got. By comparison, the tangential polarized ceramic pipe has the relatively high sensitivity, and at the same time, the hydrophone sample has been fabricated based on the finite element method. The experimental results show that the working frequency band of hydrophone sample is 30 Hz-40 kHz, the average acoustic pressure sensitivity is about ~182dB within 30 Hz-10 kHz. There are some difference in resonance frequency and the sensitivity between the result of simulation and test because of the simplification of structure in simulation.

Study on a high sensitivity and strong anti-jamming co-vibrating vector sensor

For many hydrophone applications in underwater acoustic fields, there is a great demand for vector sensors with the higher sensitivity and easily using. A high sensitivity and strong anti-jamming co-vibrating vector sensor has been described in this paper. The vector sensor with acoustic pressure channel and vector channel can be fixed in any carrier. The length of sample is 166 mm and diameter is 50 mm. The experimental results show that the cylindrical co-vibrating vector sensor has good cosine directivity and the sensitivity of vector channel is -181dB at 1kHz (re 0 dB=1V /μ Pa), and the average acoustic pressure sensitivity is -190dB (re 0 dB=1 V /μ Pa) over the frequency range of 20 Hz to 1600 Hz.