The Study Of New Type Acoustic Vector Hydrophone

The vector hydrophone,as a new type of underwater acoustic transducer,can provide particle velocity information under the water acoustic field.It has the incomparable advantage over the conventional hydrophone.So researchers can make a more comprehensive understanding of the sound field to promote the study of underwater acoustic physical properties.Its superior low frequency cosine type directivity makes it a higher array gain under a small aperture.Acoustic vector sensor is usually divided into two main types from the working characteristics.One is the inertial sensor.It is usually the co-oscillating cylindrical or spherical vector hydrophone.As the inertial sensor,the structure is mainly composed of suspension system and the sensor itself.On the application as a whole,the performance index is determined jointly by suspension system and the sensor itself.The other type is the noninertial sensor.It mainly includes the acoustic pressure-gradient hydrophone and the multimode sensor.From the sensing way,the multimode hydrophone itself is a kind of pressure-gradient pressure hydrophone.As a noninertial sensor,it doesn't need the suspension system.The Performance index is determined by the sensor itself.Metal springs or rubber cords are usually used as elastic elements to point-to-point suspend the co-oscillating vector hydrophone.Suspending the acoustic vector hydrophone repeatedly would affect the stability of the sensor.A new structure of rigidly mounted co-oscillating cylinder vector hydrophone was described.The suspension system is combined with co-oscillating vector hydrophone.On the structure,the circle type rubber spring and the co-oscillating vector hydrophone are connected face-to-face.In the mode of movement,the shear movement of cirque type rubber springs makes the vector hydrophone moving with underwater sound waves at the same time.For the receiving theory of the co-oscillating cylinder vector hydrophone usually do not include the influence of the suspension system to the performance indicators.Through the equivalent circuit method,the acoustic theory and vibration system are integrated in the equivalent circuit.Through the establishment of an equivalent circuit of the co-oscillating cylinder vector hydrophone with the suspension system,the sensitivity expression of hydrophone is derived in the water.The influence of hydrophone density,internal sensitive element,the suspension system on the characteristics of hydrophone is simulated.In this paper the shear stiffness of rubber spring is studied by the finite element method(ANSYS software).Using two parameters Mooney-Rivlen model,the paper analyzes the ring rubber spring material parameters,size parameters on the influence of the stiffness,and also the influence of different pressure on the shear stiffness.On this basis,the vector hydrophone prototypes are developed which are based on two different sensitive elements.The co-oscillating cylinder vector hydrophone which the piezoelectric accelerometer is inside can work at the frequency of 500Hz-2000Hz,and the sensitivity is not less than-190dB(@1kHz),the co-oscillating cylinder vector hydrophone which moving-coil velocity sensor is inside can work at the frequency of 500Hz-1600Hz,and the sensitivity is-190dB.The elastic suspension system of the co-oscillating vector hydrophone is usually only as part of the vibration system,it does not work directly with the sound waves.An elastic coated spherical vector hydrophone is rasearched in this paper.The sound waves propagate from the elastic inclusions to the internal spherical vector hydrophone which picks up the velocity signal under the water.The physical model of the vector hydrophone is established in this paper.Through the theoretical and simulation analysis,it is determined that how the related parameters influence the performance index of the hydrophone.Finally the prototype of acoustic vector hydrophone is made and measured on the lake in xin'an river.The working frequency band is 63-1600 Hz and the sensitivity is-183 dB(@1kHz)?The pressure-gradient hydrophone is suitable for working at a higher frequency and the working band is very narrow.A new type of sandwich structure pressure-gradient hydrophone is proposed.Bar bending modal can make the hydrophone work under the low frequency band.How to use ANSYS software to analyz and calculate the underwater acoustic characteristics of the pressure-gradient hydrophone is studied in this paper.Firstly the finite element software ANSYS is used to analysis the modal of sandwich structure pressure-gradient hydrophone in the air.This paper researches the material parameters on the influence of the lowest-order modal.Second,the harmonic response analysis in water was carried out on the hydrophone.The principle of reciprocity is used to calculate its sensitivity.Through the analysis of the sound field,the directivity characteristic is derived.Finally,production process of the sandwich structure pressure-gradient hydrophone is studied,and the prototype is manufactured,the electro-acoustic performance of the prototypes is tested in the free-field pool.Test results show a good agreement with the designing expectation.