AUDIBLE SOUND SENSING ENHANCEMENT VIA STRUCTURAL COUPLED DESIGNS OF BROADBAND METAMATERIAL

Abstract

Acoustic sensors play an important part in military, scientific, and industrial applications. Current audible sound sensing performance is mainly limited by the minimum detectable pressure of the sensor material and the energy transmission efficiency of the metamaterial component. A practical solution is to enhance the detection limit of an audible sensing device with additional amplification components and bring in impedance matching designs for high-refractive-index metamaterials containing complex internal structures. In the thesis, impedance-gradient metamaterials with structural coupled designs (SCDs) are developed and investigated to increase the overall energy efficiency and improve the audible sound sensing ability of a measurement device. Moreover, by applying SCDs, the quarter-wavelength acoustic resonator and the anisotropic sonic crystals can realize broadband sound pressure amplification. The two metamaterial-enhanced sensing systems provide broadband improvements of signal-to-noise ratio (SNR) with incident signals below the detection limit of the measurement devices.