In this paper, the relationship between sound absorption properties of porous metal-fiber material with inner cavity, and the kind of inner medium, depth and position of cavity is studied. The results show that as medium is air the average absorption coefficient of is 0.62 which is higher than 0.58, that of structure without cavity. But as the cavity filled with sulfate the average absorption coefficient goes down to 0.52. As the depth of cavity increased from 3.5 mm to 6mm, the average absorption coefficient also increased from 0.53 to 0.56 with absorbtion band broadening. The closer of the distance from cavity to absorption surface, the better properties of sound absorption are gained. For the inner structure with many dispersed cavities, the absorption properties of material may be further improved.

one kind of fusion wavelet characteristic and the generalized distinction analysis （GDA） extraction method was proposed and it was applied to descript the efficiency of dimension reduction for multi-scale feature of SEMG. First, wavelet decompose was employed on SEMG, and the mean of absolute value for wavelet coefficient at each level was extracted as original feature vector, then the dimension by GDA was reduced, the new feature of lower dimension was obtained, which was used for classification by Bayes classifier. By selecting felicitous levels of wavelet decomposition as well as pretty kernel parameter and new dimension, it can result in good performance in the pattern recognition of six movements including wrist inward，wrist outward, wrist up, wrist down, fist clench and fist stretch with the accuracy of above 97 % for three testers. The research indicated that the proposed method can successfully acquire the main component of multi-scale SEMG and its feature.

In order to predict the vibration isolation capability of towed line array vibration isolation modules, a planar fluid-structure coupling model of the array is constructed by means of ANSYS code. And the vibration isolation capability is calculated with the consideration of the influence of the load (acoustic module) on the vibration isolation modules. Pseudo-parallel improved genetic algorithm and ANSYS’s parameterized design language APDL are combined to realize the optimization of the main parameters of the vibration isolation modules. And the optimal values of internal oil density, optimal elastic moduli of hull and the components of the isolation modules for 20Hz and 40 Hz exciting frequencies are obtained. This work provides a reference for improving the performance of vibration isolation modules.

In this paper, it is reported that the structure of thin micro-perforated panel (MPP) with its holes penetrated by copper fibers can extend effectively the absorption band and improve sound absorption coefficient. Thus, the sound absorption performance of the micro-perforated plate is greatly improved in the mid-and-low frequency range. The sound-absorption testing was done for the MPP samples with 100 mm and 29 mm diameters respectively, 2 mm thickness, 1mm diameter holes, 3 % perforation rate and 0.13mm diameter penetrating cooper fibers. The results show that the resonance absorption coefficient of MPP with penetration of 3 or 4 copper fibers for each hole can reach 0.99 in the frequency range of 100 Hz ~ 1 600 Hz, and its sound-absorption band can expand by 1 000 Hz when 7-9 fibers are penetrated for each hole. With increasing of the number of the fibers penetrated into each hole, the absorption band will shift to low frequency side. When 11 fibers are penetrated into each hole, the shifting magnitude can reach 464 Hz.

Thick microperforated panels (MPP) usually do not have such a good sound absorption feature as the thin panels do because of their high resistance and/or reactance. In order to improve the thick MPPs acoustical performance, thin stainlesssteel fibers are inserted into the orifices of the thick MPP, and their sound absorption coefficients are measured. Results show that the thin stainlesssteel fibers can widen the frequency band for sound absorption of the thick MPP effectively. When the insertion rate of the fibers reaches 50% and the usage of fibers reaches 0.75mg per orifice, the frequency band of sound absorption is 3921168Hz for the absorption coefficient larger than 0.5. While for the MPP without fiber insertion the frequency band for sound absorption is only 5301076Hz.

MPPs are typically made of a thin metal or plastic panel. However, thin limp panels are generall not suitable as an interiornish of room walls because they do not have sucient strength, which prevent spractica lapplication of MPPs as an interiornish of roomwalls. When we put the air, water, polyvinyl alcohol and wool fiber into the pores of the thick microperforated panel respectively and the epoxy resin panel have a porosity of 7%, 10mm thick and the pore is 1mm in diameter. Measurements of the sound absorption characteristics of microperforated panel with those above material have been carried out in the Pulse 3560 and 4206 made in B&K company. The result show that the absorption coefficient of sound is better when the wool fiber’s number is 53 per pore and the depth of the back air cavity is 20mm than air in its holes. The peak value of sound absorption coefficient is about 0.94 when the resonance frequency is about 956, the frequency from 612Hz to 1600Hz all have the absorption coeifficien above 0.5.