The Study On The Structure And Performance Of Novel Acoustic Devices

This thesis studies the structure and performance of novel acoustic devices, which mainly includes three parts:(1) The study on the extraordinary acoustic transmission (EAT) of acoustic grating with base plant; (2) The dual-filter characteristics of an acoustic dual filter with two local resonant systems; (3) The study of sub-harmonic wave based on a nonlinear impact structure. The contents of each part are described briefly as following:1. The study on the extraordinary acoustic transmission (EAT) of acoustic grating with base plantWhen light travel through the sub-wavelength slit, the extraordinary optical transmission (EOT) would occur. It is the same as acoustic. In the first part of the thesis, you can see the recent research of the extraordinary acoustic transmission (EAT) of the acoustic gratings. Not the same as surface plasmon polariton (SPP) resonance in EOT, the excitations of transverse, coupled resonant acoustic modes along the direction of grating period cause the resonant transmissions in acoustic gratings. These extraordinary transmissions for acoustic waves in the acoustic gratings may have important applications in the collimation of sound and one-way transmission of acoustic wave.In the second part of the thesis, firstly the unidirectional transmission of the acoustic gratings with base plant is introduced. The unidirectional transmission is due to the reconstruction of the acoustic pattern, which is motivated by the acoustic gratings. Then by adding the films and changing the fillings between the films and the gratings the transmission efficiency of the energy gap is increased. When acoustic waves travel with obliquely incidence, the transmitted wave would behave negative transmission. The graphs of sound transmission with different incidence angle at negative transmission frequencies are listed. Lastly the acoustic gratings with base plant have the excellent divergent effect with oblique incidence.2. The dual-filter characteristics of an acoustic dual filter with two local resonant systemsAcoustic metamaterial with local resonant would behave negative mass and negative modulus, even both negative, which may have important applications in superlens and sound focusing by flat lenses. The research advances of local resonant acoustic metamaterial can be referred in first chapter of the thesis.In the third part of the thesis, firstly the recent studies on the membrane acoustic metamaterial are presented. Then the dual-filter model is constructed, which is composed of two coupling resonant systems, the PE-A1 system and membrane-air column system. The local vibrational profiles manifest that the transmission peak at lower frequency is mainly dependent on the resonant vibration of the membrane-air system, and the coupling vibrations of two systems generate the blocking frequency and transmission peak at higher frequency. Importantly, two transmission peaks can be controlled independently. It is feasible to realize the acoustic device in sound shield and dual filters.3. The study of sub-harmonic wave based on a nonlinear impact structureIn the forth part of the thesis, the investigation on the sub-harmonic effect of the nonlinear impact is first introduced. When sonic infrared imaging is used in nondestructive testing (NDT), the amazing acoustic chaos could happen. Then the numerical model and the FEM simulation model of the nonlinear impact are presented. We put forward a new model based on nonlinear impact by using PE-A1 local resonant system represents the transducer of sonic infrared imaging and another PE-A1 local resonant system with different resonant frequency represents the metal plant. More plentiful physical effect can be produced through the novel model when the two local systems with different resonant frequencies impact nonlinearly. Finally the initial process of the model by ANSYS is presented.Finally, the conclusions and the prospects of the work were presented.