| Popis: |
Acoustic metamaterial can have arbitrary acoustic characteristics , and there is possibility to improve acoustic performance of any products dramatically. As metamaterial, many kind of types have been propounded and studied. It is mainly classified into resonance type and non-resonance type.Resonance type metamaterial can change acousic characteristics drastically, but frequency range is narrow. Non-resonance type’s acoustic characteristics range is less than resonance type, but it can be changed in broad frequency band. It is a great advantage to use. About non-resonance type metamaterial, it has been already studied to control transmitted sound, but it has not been studied about reflection sound. If reflection sound control become possible, effective method can be chosen to solve noise problem. For example, resonance frequency in a duct will be shifted by changing reflection direction from the wall. In this study, the design method of non-resonance type metamaterial to control reflection sound has been studied by using FEM and Transfer-function method, and to verify the design method, element test was conducted. Element test result correspond well with analysis result, and the design method of acoustic metamaterial has been verified in this study. In order to put into practical use, further study with actual product shape is needed to confirm manufacturability. |
