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Method based on broadband compressed pulse superposition to measure properties of underwater acoustic materials 被引量:2
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作者 LI Shui,MIAO Rongxing (National Defence Underwater Acoustic Metrology Center Fuyang Zhejiang 311400) 《Chinese Journal of Acoustics》 2001年第1期52-60,共9页
A method is proposed for the measurements of the performances of underwater acoustic finite sized large area material samples in a free field by using broadband pulse compression technique. As the result of which, th... A method is proposed for the measurements of the performances of underwater acoustic finite sized large area material samples in a free field by using broadband pulse compression technique. As the result of which, the low-frequency cutoff of the standard tests is obviously reduced, and the broadband measurements are also realized. The experimental system provides measurements of complex reflection and transmission coefficients at continuous frequency points. From the data one can obtain the following acoustic parameters: echo reduction and insertion loss, absorption and attenuation coefficients, etc. The measurements are performed for two actual panels with the size 1 m x 1 m in the frequency range from 2-20 kHz. 展开更多
关键词 Method based on broadband compressed pulse superposition to measure properties of underwater acoustic materials
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Oblique incidence properties of locally resonant sonic materials with resonance and Bragg scattering effects 被引量:3
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作者 袁博 温激鸿 温熙森 《Chinese Physics B》 SCIE EI CAS CSCD 2013年第7期267-273,共7页
A locally resonant sonic material (LRSM) is an elastic matrix containing a periodic arrangement of identical local resonators (LRs), which can reflect strongly near their natural frequencies, where the wavelength ... A locally resonant sonic material (LRSM) is an elastic matrix containing a periodic arrangement of identical local resonators (LRs), which can reflect strongly near their natural frequencies, where the wavelength in the matrix is still much larger than the structural periodicity. Due to the periodic arrangement, an LRSM can also display a Bragg scattering effect, which is a characteristic of phononic crystals. A specific LRSM which possesses both local resonance and Bragg scattering effects is presented. Via the layered-multiple-scattering theory, the complex band structure and the transmittance of such LRSM are discussed in detail. Through the analysis of the refraction behavior at the boundary of the composite, we find that the transmittance performance of an LRSM for oblique incidence depends on the refraction of its boundary and the transmission behaviors of different wave modes inside the composite. As a result, it is better to use some low-speed materials (compared with the speed of waves in surrounding medium) as the LRSM matrix for designing sound blocking materials in underwater applications, since their acoustic properties are more robust to the incident angle. Finally, a gap-coupled LRSM with a broad sub-wavelength transmission gap is studied, whose acoustic performance is insensitive to the angle of incidence. 展开更多
关键词 underwater acoustic materials oblique incidence locally resonant sonic materials Bragg scattering
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Measurement of the echo reduction for underwater acoustic passive materials by using the time reversal technique 被引量:8
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作者 YAN Xiaowei LI Jianlong HE Zhiguang 《Chinese Journal of Acoustics》 CSCD 2016年第3期309-320,共12页
A measuring method of the echo reduction of passive materials by using the time reversal(TR) technique is presented. To measure the echo reduction of a sample with this approach, the received signals are firstly foc... A measuring method of the echo reduction of passive materials by using the time reversal(TR) technique is presented. To measure the echo reduction of a sample with this approach, the received signals are firstly focused according to the TR theory. Then, the sample is removed and the TR processing is again employed to realize the focus of the received signal.Finally, the echo reduction of the sample is evaluated with these focusing signals. Besides, to calibrate the measured echo reduction via the TR technique, a standard sample is employed to measure a constant coefficient that only depends on the measurement environment. An aluminum plate sample and a steel plate sample with the same size of 1.1 mxl.O m x0.005 m axe tested in a wave guide tank. The experimental results show that the calibrated values are well consistent with theoretical results under the free field at the measured frequency range of0.5-20 kHz. The relative errors of all the measured values are less than 10% and the values of the expanded uncertainty are less than 1.5 dB. The TR processing focuses the energy in spatial domain and temporal domain, so it can be used to measure the echo reduction of passive materials in the environments with reflections induced by boundaries and low frequency sources. 展开更多
关键词 time Measurement of the echo reduction for underwater acoustic passive materials by using the time reversal technique TR
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Measurement of insertion loss for underwater acoustic passive materials with the time reversal technique 被引量:2
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作者 YAN Xiaowei LI Jianlong KONG Xiangdong 《Chinese Journal of Acoustics》 2014年第2期109-120,共12页
A method using the time reversal(TR) technique to measure the insertion loss(IL) of passive materials is presented.Firstly the received signals are focused according to the TR theory when there is not a sample bet... A method using the time reversal(TR) technique to measure the insertion loss(IL) of passive materials is presented.Firstly the received signals are focused according to the TR theory when there is not a sample between the source and the received array.Then,the sample is placed near the received array and the TR processing is again employed to realize the focus of the received signal.Finally,the IL of the sample is evaluated from these focusing signals.Because the TR processing can focus the energy in spatial domain and time domain,the method can be used to measure acoustic properties of passive materials in a waveguide tank with reflections induced by boundaries or with low source frequencies.Two samples with the same size of 1.1 m×1.0 m×5 mm are tested in the waveguide tank.The method is demonstrated by the comparison of the theoretical and the experimental results in the measured frequency range of 1-20 kHz. 展开更多
关键词 TIME Measurement of insertion loss for underwater acoustic passive materials with the time reversal technique TR
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Investigation on method for measuring dynamic shear modulus of underwater acoustic structure materials 被引量:1
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作者 LI Shui TANG Haiqing MIAO Rongxing (Hangzhou Applied Acoustic Institute Fuyang Zhejiang 311400) 《Chinese Journal of Acoustics》 1999年第2期121-127,共7页
A new method is described to measure the dynamic shear modulus of underwater acoustic structure materials in a small anechoic water tank by using a broadband parametric source, a precise coordinate installation and te... A new method is described to measure the dynamic shear modulus of underwater acoustic structure materials in a small anechoic water tank by using a broadband parametric source, a precise coordinate installation and techniques of signal processing in the frequency range of 20 kHz - 100 kHz. The typical size of material samples is 500×500 mm2. Basic principles, experiment installation and measured results are also presented 展开更多
关键词 Investigation on method for measuring dynamic shear modulus of underwater acoustic structure materials
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