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acoustic impedance of perforated panels covered by membranes

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Chinese Journal of acoustics 1994年第1期13卷 13-21页

作者： SHENG Shengwo and ZHAO Songling (Institute of acoustics, Tongji University, Shanghai 200092)

In this paper, acoustical characteristic of a perforated panel with cover membranes is theoretically investigated. Based on the fundamental principle of acoustics, the expressions of reflecting the sound transmission of this construction are derived and the formulas of calculating the specific acoustic impedance are obtained, We also discuss the changes of specific acoustic resistance with some important parameters, such as the frequency, the thickness of air layer and the surface density of the membrane. A good agrecment between predicted results and measured data is illustrated.

关键词： Cover membrane Perforated panel acoustic impedance

Research on Hydrodynamic Interference Suppression of Bottom-Mounted Monitoring Platform with Fairing Structure

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China Ocean Engineering 2018年第1期32卷 51-61页

作者： WANG Zhen ZHENG Yi MAO Yu-feng WANG Ya-zhou YU Yan-ting LIU Hong-ning Institute of Oceanographic Instrumentation Qilu University of Technology(Shandong Academy of Sciences)Qingdao 266061China Shandong Provincial Key Laboratory of Ocean Environmental Monitoring Technology Qingdao 266061China National Engineering and Technological Research Center of Marine Monitoring Equipment Qingdao 266061China

In the disturbance of unsteady flow field under the sea, the monitoring accuracy and precision of the bottom-mounted acoustic monitoring platform will decrease. In order to reduce the hydrodynamic interference, the platform wrapped with fairing structure and separated from the retrieval unit is described. The suppression effect evaluation based on the correlation theory of sound pressure and particle velocity for spherical wave in infinite homogeneous medium is proposed and the difference value between them is used to evaluate the hydrodynamic restraining performance of the bottom-mounted platform under far field condition. Through the sea test, it is indicated that the platform with sparse layers fairing structure(there are two layers for the fairing, in which the inside layer is 6-layers sparse metal net, and the outside layer is 1-layer polyester cloth, and then it takes sparse layers for short) has no attenuation in the sound pressure response to the sound source signal, but obvious suppression in the velocity response to the hydrodynamic noise. The effective frequency of the fairing structure is decreased below 10 Hz, and the noise magnitude is reduced by 10 d B. With the comparison of different fairing structures, it is concluded that the tighter fairing structure can enhance the performance of sound transmission and flow restraining.

关键词： bottom-mounted fairing hydrodynamic interference acoustic impedance transmission loss

Feasibility of photoacoustic tomography for ophthalmology

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Chinese Optics Letters 2007年第8期5卷 475-476页

作者：卢涛宋智源苏翼雄张帆姚建铨 Institute of Lasers and Optoelectronics College of Precision Instrument and Opto-Electronics Engineering Tianjin University

For the eyeball composed of membrane and liquid, the contrast of ultrasound imaging is not high due to its small variance in acoustic impedance. As a new imaging modality, photoacoustic tomography combines the advantages of pure optical and ultrasonic imaging together and can provide high resolution, high contrast images. In this paper, the feasibility of photoacoustic tomography for ophthalmology is studied experimentally. A Q-switched Nd：YAG pulsed laser with 7-ns pulse width is used to generate photoacoustic signal of a porcine eyeball in vitro. The two-dimensional （2D） optical absorption image of the entire eyeball is reconstructed by time-domain spherical back projection algorithm. The imaging results agree well with the histological structure of the eyeball and show a high imaging contrast.

关键词： acoustic impedance Algorithms Laser pulses Light absorption Ophthalmology Photoacoustic effect Q switched lasers Two dimensional Ultrasonic imaging

The application of elastic impedance inversion in reservoir prediction at the Jinan area of Tarim Oilfield

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Applied Geophysics 2007年第3期4卷 201-206页

作者： Yang Jinhua Li Guofa Liu Yang Jiang Weidong School of Earth and Space Sciences Peking University Beijing 100871 China Key Laboratory of Geophysical Exploration of CNPC China University of Petroleum Beijing 102249 China East Geophysical Company Zhuozhou 072751 China

The Triassic reservoir in the Jinan area of Tarim Oilfield consists largely of interbedded sand and shale. Because of the large overlap between sandstone and shale impedance, it is difficult to distinguish sandstone from shale by acoustic impedance alone. Compared to acoustic impedance, elastic impedance contains more lithologic and physical information of the reservoir. Based on meticulous well-tie calibration, elastic impedance data volumes for 10°, 20°, and 30° emergence angles are obtained using pre-stack elastic impedance inversion. A non-linear statistical relationship between elastic impedance and shale content is set up by a PNN neural network. The non-linear mapping relationship is used to predict the reservoir shale content from elastic impedance, which will depict and predict the reservoir oil-bearing sands.

关键词： acoustic impedance elastic impedance shale content PNN neural network non-linear relationship

Effect of Temperature on the acoustic Reflection Characteristics of Seafloor Surface Sediments

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Journal of Ocean University of China 2022年第1期21卷 62-68页

作者： ZOU Dapeng YE Guican LIU Wei SUN Han LI Jun XIAO Tibing State Key Laboratory of Precision Electronic Manufacturing Technology and Equipment Guangdong University of TechnologyGuangzhou 510006China State Key Laboratory of acoustics Institute of AcousticsChinese Academy of SciencesBeijing 100190China College of Engineering South China Agricultural UniversityGuangzhou 510642China

Because the sound speeds of seawater and seafloor sediment both increase with temperature,the influence of tempera-ture on the bottom reflection characteristics of seafloor sediments needs to be *** on the calculation of the temperature-controlled experimental measurement data of typical seafloor surface sediment samples,the temperature-dependent acoustic characteristics,including acoustic impedance,acoustic impedance ratio between surface sediment and seawater,and reflection coefficient,were *** effective density fluid model was used to analyze and explain the reflection coefficient variation of surface sediments with temperature and predict the dispersion *** show that the acoustic impedance of the seabed sediment increases with temperature,whereas the acoustic impedance ratio and acoustic reflection coefficient slightly *** acoustic impedance,acoustic impedance ratio,and acoustic reflection coefficient of sandy,silty,and clayey sediments vary similarly with tem-perature ***,the influence of temperature on these acoustic characteristics is independent of detection frequencies.

关键词： reflection coefficient seafloor sediment temperature acoustic impedance

The Role of PZT in Flexible 1-3 Piezoelectric Composite for Smart Structure

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稀有金属材料与工程 2006年第A3期35卷 588-589页

作者： Ren Huaishi Fan Huiqing Zhang Jie Wang Wei State Key Laboratory of Solidification Processing School of Materials Science and Engineering Northwestern Polytechnical University Xi＇an 710072 China

Piezoelectric composite materials have the ability to perform both sensing and actuating *** is a viable candidate for smart actuation in underwater noise controlling with its higher coupling factor and lower acoustic impedance, when the piezoelectric rods are inclined to control its both the shear and the compression damping *** this paper, a simple physical model of 1-3 piezoelectric composite is advanced for maximizing the electromechanical coupling factor,the acoustic impedance,and the hydrophone figure of merit.

关键词： piezoelectric composite electromechanical coupling factor the hydrophone figure of merit acoustic impedance

3D modeling of abnormal pore pressure in shallow offshore Niger delta: An application of seismic inversion

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Petroleum Research 2021年第2期6卷 158-171页

作者： Chukwuemeka Patrick Abbey Osita Chukwudi Meludu Adetola Sunday Oniku a a Department of Physics Modibbo Adama University of Technology YolaNigeria Department of Petroleum Chemistry&Physics American University of NigeriaNigeria

Pore pressure is the pressure associated with fluids in the pore spaces of sedimentary rocks. Thispressure varies from hydrostatic to severe overpressure. It is classified as abnormal pressure when itdeviates from hydrostatic pressure. Incorrect prediction or the absence of pore pressure evaluation canlead to severe damage of the drilling platform, loss of personnel, waste of resources and environmentalpollution. This study was carried out in an offshore field in Niger Delta with an objective of predicting theabnormal pressure regime from the seismic volume using seismic inversion technique. First, weemployed the Eaton’s and Bower’s model of predicting pore pressure from Well log. The predicted porepressure from the well was used to calibrate the P-impedance that was used in the inversion process. Apressure-based model for the seismic inversion process was developed. This was constrained by therelationship between the P-impedance and pore pressure in the study area. The predicted pore pressurefrom the Well logs aligned with the measured pore pressure in the formation. At about 3600 m to end ofthe Well, depicts a pressure regime that is a deviation from the hydrostatic pressure trend. The abnormalpressure regime is marked by the region where a change is observed in the normal compaction trendline. The cross plot of acoustic impedance against pore pressure reveals a linear relationship;with adirect relationship indicating a normal pressure interval and the indirect relationship at the abnormalpressure regime. The inverted 3D pressure result from the seismic volume validates the normalcompaction trend line and also the pressure values estimated from the Well logs. The abnormal pressureregime in the study area is predicted to be found towards the end of Agbada Formation and through theAkata Formation due to the un-compacted shales.

关键词： acoustic impedance Pressure Seismic inversion Formation Overpressure

Inclusive reservoir characterization from rock physics and sequence stratigraphic analyses of Middle Miocene,Niger delta

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Petroleum Research 2021年第3期6卷 213-223页

作者： Austin E.Okoli Okechukwu E.Agbasi School of Engineering GeosciencesInfrastructure and SocietyHeriot Watt UniversityEdinburghEH144ASUnited Kingdom Department of Geology Federal University of TechnologyOwerriImo StateNigeria Department of Physics Michael Okpara University of AgricultureUmudikeAbia StateNigeria

The estimation of seismic reservoir properties faces difficulties such as delineating deceptive fluid contacts,over-estimating reserves and drilling dry *** overcome these problems,sequence strat-igraphic and rock physics analyses that were constrained by the compaction trend were implemented in the Sigma *** field is located in the Coastal Swamp depobelt,in the distal *** data from the field and a total of three wells,Sigma-30,26,and 25 were provided for the *** data was also given for the field and dated to shale marker *** strati-graphic sequence analysis of the wells in field indicate they were deposited in a regressive,transgressive and aggradational episodes,whereas the entire depositional history shows predominantly regressive *** field reservoirs,SM-14(LST),SM-04(TST),and SM-02(HST)were *** analysis of the landscape from sequence stratigraphic analyses of the field indicates that Sigma feld reservoirs were deposited in a front region of the *** to compaction has been generated for the *** wells showed a normal trend toward *** physics analysis of the reservoirs of interest reveals that LST and TST reservoirs have been dificult to distinguish against HST reservoirs which are easy to classify regardless of their depth for fluids in a Vp/Vs crossplot versus acoustic *** the analysis,a pattern is suggested for TST ***,this research work shows that fluid discrimination becomes simpler as we go basin ward as the sorting of the reservoir rocks increases with finer grain sand sizes.

关键词： acoustic impedance Lambda-rho Mu-rho Poisson impedance Reservoirs

Parameter Study on a Composite Sound-Absorbing Structure Liner in Elevator Shafts

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Journal of Renewable Materials 2023年第9期11卷 3433-3446页

作者： Ting Qu Bo Wang Hequn Min Key Laboratory of Urban and Architectural Heritage Conservation of Ministry of Education School of ArchitectureSoutheast UniversityNanjing210096China

With the growing global environmental awareness,the development of renewable and green materials has gained increased worldwide interest to substitute conventional materials and are favorable for sustainable economic *** paper proposed a novel eco-friendly sound absorbing structure(NSAS)liner for noise reduction in elevator *** base layer integrated with the shaft walls is a damping gypsum mortarboard,and a rock wool board and a perforated cement mortarboard are used to compose the *** on the acoustic impedance theory of porous materials and perforated panels,the sound absorption theory of the NSAS was proposed;the parameter effects of the rock wool board(flow resistivity,porosity,structure factor)and perforated panel(perforated rates,thickness,density,perforated diameter)on NSAS absorption were discussed theoretically for absorption improvement,and experiments were also *** results showed that the perforation rate,the thickness of the perforated plate,and the porosity,flow resistance,and volume density of the rock wool board played a key issue in the absorption performances of the *** verified the accuracy of the proposed theoretical *** sound absorption performance of the NSAS at frequencies between 500–1600 Hz was achieved in both numerical analysis and experiments,and the sound absorption coefficient was improved to 0.72 around 1000 Hz after parameter *** NSAS proposed in this paper can also be made of other renewable materials with preferable structure strength and still has the potential to broaden the absorption *** can provide a reference for controlling the elevator shaft noise.

关键词： Elevator shafts sound-absorbing liner porous material ﬂow resistivity acoustic impedance