Research On Actively Sound Detection And Passively Tunable Acoustic Metasurfaces

How to accurately detect and control sound waves arbitrarily are two main directions in the field of acoustic.The former is in the engineering field,by using acoustic sensors and building electronic circuits to collect and process the sound waves generated by the mechanical vibration of the object,and analyze the structural characteristics and defects of the object;the latter is manually designing compact and efficient acoustic phase adjustment unit to achieve arbitrary control of acoustic waves,which also has extremely important application prospects.In this paper,we propose a active keyboard abnormal sound detection system written in Lab VIEW,and a passive acoustic metasurface designed by the structure of a annular-shaped tunable unit.In the chapter one,we mainly introduce the research background of keyboard abnormal sound detection system and acoustic hypersurface design,including the theoretical derivation of generalized Snell's law.The second and third chapters are the active noise detection part of keyboard keys.The second chapter introduces the function and hardware structure of the abnormal sound detection system,and shows the control and operation process of the hardware part realized by Lab VIEW.The hardware part includes: the mechanism controlled by the PLC,the circuit that controls the electromagnet to strike the keycap,the microphone and the acquisition card and other abnormal sound signal acquisition parts.The third chapter uses Lab VIEW to realize the collection,display,processing and analysis of different sound signals,and demonstrates the operation status and achievable function expansion of the detection system.The fourth chapter is the study of passive tunable acoustic metasurface.In order to make up for the defects and deficiencies of acoustic metamaterials in the process of realizing sound wave control,programmable metamaterials and adjustable metamaterials came into being.They can change the material structure parameters in real time according to the sound wave frequency and the function to be realized.They are extremely efficient in sound wave control and can adapt to different working frequency bands,which really paves the way for the practical application and development of metamaterials.Based on the development of many tunable passive acoustic metasurfaces,this chapter proposes an acoustic metasurface designed by a annular-shaped tunable unit structure.The structural unit of the adjustable metasurface has the characteristics of compactness,flexibility.By rotating the shell of the unit structure,the volume of the cavity inside the unit structure is adjusted to achieve flexible and efficient adjustment of the phase of the sound wave.Based on this,the adjustable acoustic metasurface formed achieves acoustic focusing at different operating frequencies The effect is of great significance for the development of the metasurface towards practicality and versatility.Chapter 5 summarizes the two main studies in this article and prospects for future work.