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Research on the Effect of Sound Baffle on the Directivity of Vector Sensor

Author: ZuoJianFei
Tutor: LiangGuoLong
School: Harbin Engineering University
Course: Signal and Information Processing
Keywords: vector sensor directivity baffle spheroidal wave functions finiteelement method boundary element method sound scatting sound ifeldseparation
CLC: TP212
Type: PhD thesis
Year: 2012
Downloads: 99
Quote: 0
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Abstract


In recent years, since it could simultaneously pick up the scalar and vectorinformation of the sound field, acoustic vector sensor is widely used in underwateracoustic technical fields. In many applications the vector sensor works in the rfee ifeldwith no effects of the boundary conditions. If the vector sensor is installed on shipshell or unmanned underwater vehicle, it will be inevitably affected by the sounddiffraction, thus affecting its measuring results.This paper analyzes effects of the directivity of vector sensor under the conditionof baffle in shape of sphere, prolate spheroid, finite cylinder at different frequencies.Based on that, it studies the effects of the shape and size of the baffle on thedirectivity of vector sensor, and gives out the optimized shape of the baffle, andproposes the reconstructing technique of the directivity of vector sensor. The keycontributions are:1.This paper deduces the mathematical expression of sound pressure andvibration velocity in the scatting fields of impedance sphere and elastic spherical shellIt also analyzes characteristic of the directivity of pressure and vibration velocity ofthe impedance sphere at different frequencies and impedance conditions, as well asthat of the scatting field of air-filled elastic spherical shell at different frequencies. Interms of impedance ball, the effect of impedance on scatting field is determined by thescattering background. The paper analyzes the change law of the directivity ofpressure and vibration velocity of vector sensor with the impedance and the changerelationship between frequencies and the amplitude as well as the phase difference ofincident and scatting fields of absolute soft sphere and rigid sphere,For the elasticspherical shell iflled with air, the scatting field can be seen as the algebra addition ofrigid sphere scatting field and vibrating elastic spherical shell radiating field Thepaper analyzes the change law of directivity of vector sensor under the condition ofelastic spherical shell baffle at different frequencies, together with the changerelationship between frequencies and the amplitude as well as the phase difference ofscatting and incident ifelds.2,The paper deduces the mathematical expression of sound pressure andvibration velocity in the scatting ifelds of soft and rigid prolate spheroid. It alsoanalyzes characteristic of the directivity of pressure and vibration velocity of vectorsensor under the condition of soft and rigid prolate spheroidal baffle at different frequencies, together with the change law between the incident angle and theamplitude as well as the phase difference of scatting and incident ifelds.3.Using the method of infinite and boundary elements, the paper calculates thescatting pressure and vibration velocity fields of soft ifnite cylinder, rigid finitecylinder and air-filled elastic finite cylindrical shell at different frequencies. It givesout the change law of characteristic of the directivity of vector sensor under thecondition of soft finite cylinder, rigid finite cylinder and air-iflled elastic finitecylindrical shell baflfe at different frequencies, together with the change relationshipbetween frequencies and the amplitude as well as the phase difference of scatting andincident ifelds.4.The size and shape of the balffe are closely related to the directivity of vectorsensor. The paper analyzes effects of the directivity of vector sensor under thecondition of balffe in shape of the sphere with the same vertical and hoirzontaldimensions, long rotating ellipsoid, finite cylinder. Based on that, the paper designsthe reasonable baffle structure to reduce the effects of the scatting field on thedirectivity of vector sensor.5.The position where the vector sensor is installed on the baffle has great effectson its directivity. Choosing the reasonable position to install the vector sensor canreduce the effects of the scatting ifeld on the vector sensor.6.The paper gives the expeirmental verification on basis of the simulation. InThousand Island Lake the expeirments of the effects of balffe on the vector sensor arecarried out,and the paper analyzes the comparison of the simulation and experimentalresults.7.The paper proposes the reconstructing technique of the directivity of vectorsensor under the condition of balffe. Reasonable shape and size of the baffle andreasonable position where the vector sensor is installed on the baffle can only reducethe effects of the directivity of vector sensor in the scatting ifeld, while it is diiffcult tofundamentally eliminate the impacts of the scatting field. The paper proposes thesound field separation method to separate the scatting ifeld from the incident ifeld andreconstruct the directivity of vector sensor.

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