This research aimed to study the sound absorption properties of natural fibers and their reinforced composites.Sound absorption coefficients of three types of natural fibers,i.e.,ramie,flax and jute fibers and their c...This research aimed to study the sound absorption properties of natural fibers and their reinforced composites.Sound absorption coefficients of three types of natural fibers,i.e.,ramie,flax and jute fibers and their composites were measured by the two-microphone transfer function technique in the impedance tube.The results were compared with synthetic fibers and their composites.It was found that both natural fibers and their composites had superior capability of noise reduction.The multi-scale and hollow lumen structures of natural fibers contributed to the high sound absorption performance.Moreover,the sound absorption properties of these natural fibers were also calculated by the Delany-Bazley and Garai-Pompoli models.They showed good agreement with the experimental data.It was concluded that multi-functional composite materials can be made by natural fibers so that both the mechanical and acoustical functions can be achieved.展开更多
针对矿用锚杆的轴力监测,提出了一种锤击声学监测方法。利用结构的固有频率与载荷之间的线性关系,改变结构自由振动时发出声音的频率,根据不同频率的声音来判断锚杆轴向力的大小。通过ANSYS模态分析和Virtual.lab声场分析,得出监测装置...针对矿用锚杆的轴力监测,提出了一种锤击声学监测方法。利用结构的固有频率与载荷之间的线性关系,改变结构自由振动时发出声音的频率,根据不同频率的声音来判断锚杆轴向力的大小。通过ANSYS模态分析和Virtual.lab声场分析,得出监测装置承受载荷从0变到178 k N,声音的频率变化216.92 Hz。并对锤击力的位置、大小及工作人员所处监测位置进行声场分析,证明了该监测装置具有一定的可行性。展开更多
针对经典疗法在耳鸣声治疗有效性或康复音可听性上存在的不足,本研究基于迭代函数系统(iterative function system,IFS)和乐器数字接口技术(musical instrument digital interface,MIDI),提出一种多音轨个性化耳鸣康复音的合成方法,使...针对经典疗法在耳鸣声治疗有效性或康复音可听性上存在的不足,本研究基于迭代函数系统(iterative function system,IFS)和乐器数字接口技术(musical instrument digital interface,MIDI),提出一种多音轨个性化耳鸣康复音的合成方法,使合成康复音在保持频率特性的同时提升心理感知特性。从个性化匹配的MIDI音乐中提取音调和节奏组合,在IFS算法映射下合成时长可控分形音乐。以丰富的频率集中自然声、流畅的类白噪声自然声和分形音乐合成多音轨个性化耳鸣康复音,其中频率集中自然声匹配患者耳鸣频率,代替传统掩蔽中听感不佳的窄带噪声。仿真结果表明,客观上本研究方法所合成康复音中的旋律与原曲相似,符合1/f波动和分维特性,康复音输入耳鸣模型能有效抑制对应频段耳鸣;试听结果表明,主观上整体试听效果舒缓自然。本研究方法对耳鸣治疗具有一定参考价值。展开更多
This study investigates the vibration and acoustic properties of porous foam functionally graded(FG)plates under the influence of the temperature field.The dynamics equations of the system are established based on Ham...This study investigates the vibration and acoustic properties of porous foam functionally graded(FG)plates under the influence of the temperature field.The dynamics equations of the system are established based on Hamilton's principle by using the higher-order shear deformation theory under the linear displacement-strain assumption.The displacement shape function is assumed according to the four-sided simply-supported(SSSS)boundary condition,and the characteristic equations of the system are derived by combining the motion control equations.The theoretical model of vibro-acoustic coupling is established by using the acoustic theory and fluid-structure coupling solution method under the simple harmonic acoustic wave.The system's natural frequency and sound transmission loss(STL)are obtained through programming calculations and compared with the literature and COMSOL simulation to verify the validity and reliability of the theoretical model.The effects of various factors,such as temperature,porosity coefficients,gradient index,core thickness,width-to-thickness ratio on the vibration,and STL characteristics of the system,are discussed.The results provide a theoretical basis for the application of porous foam FG plates in engineering to optimize vibration and sound transmission properties.展开更多
基金supported by the National Basic Research Program of China ("973" Program) (Grant No. 2010CB631105)
文摘This research aimed to study the sound absorption properties of natural fibers and their reinforced composites.Sound absorption coefficients of three types of natural fibers,i.e.,ramie,flax and jute fibers and their composites were measured by the two-microphone transfer function technique in the impedance tube.The results were compared with synthetic fibers and their composites.It was found that both natural fibers and their composites had superior capability of noise reduction.The multi-scale and hollow lumen structures of natural fibers contributed to the high sound absorption performance.Moreover,the sound absorption properties of these natural fibers were also calculated by the Delany-Bazley and Garai-Pompoli models.They showed good agreement with the experimental data.It was concluded that multi-functional composite materials can be made by natural fibers so that both the mechanical and acoustical functions can be achieved.
文摘针对矿用锚杆的轴力监测,提出了一种锤击声学监测方法。利用结构的固有频率与载荷之间的线性关系,改变结构自由振动时发出声音的频率,根据不同频率的声音来判断锚杆轴向力的大小。通过ANSYS模态分析和Virtual.lab声场分析,得出监测装置承受载荷从0变到178 k N,声音的频率变化216.92 Hz。并对锤击力的位置、大小及工作人员所处监测位置进行声场分析,证明了该监测装置具有一定的可行性。
文摘针对经典疗法在耳鸣声治疗有效性或康复音可听性上存在的不足,本研究基于迭代函数系统(iterative function system,IFS)和乐器数字接口技术(musical instrument digital interface,MIDI),提出一种多音轨个性化耳鸣康复音的合成方法,使合成康复音在保持频率特性的同时提升心理感知特性。从个性化匹配的MIDI音乐中提取音调和节奏组合,在IFS算法映射下合成时长可控分形音乐。以丰富的频率集中自然声、流畅的类白噪声自然声和分形音乐合成多音轨个性化耳鸣康复音,其中频率集中自然声匹配患者耳鸣频率,代替传统掩蔽中听感不佳的窄带噪声。仿真结果表明,客观上本研究方法所合成康复音中的旋律与原曲相似,符合1/f波动和分维特性,康复音输入耳鸣模型能有效抑制对应频段耳鸣;试听结果表明,主观上整体试听效果舒缓自然。本研究方法对耳鸣治疗具有一定参考价值。
基金Project supported by the National Natural Science Foundation of China(No.11972082)。
文摘This study investigates the vibration and acoustic properties of porous foam functionally graded(FG)plates under the influence of the temperature field.The dynamics equations of the system are established based on Hamilton's principle by using the higher-order shear deformation theory under the linear displacement-strain assumption.The displacement shape function is assumed according to the four-sided simply-supported(SSSS)boundary condition,and the characteristic equations of the system are derived by combining the motion control equations.The theoretical model of vibro-acoustic coupling is established by using the acoustic theory and fluid-structure coupling solution method under the simple harmonic acoustic wave.The system's natural frequency and sound transmission loss(STL)are obtained through programming calculations and compared with the literature and COMSOL simulation to verify the validity and reliability of the theoretical model.The effects of various factors,such as temperature,porosity coefficients,gradient index,core thickness,width-to-thickness ratio on the vibration,and STL characteristics of the system,are discussed.The results provide a theoretical basis for the application of porous foam FG plates in engineering to optimize vibration and sound transmission properties.
