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Weak Signals Detection by Acoustic Metamaterials-Based Sensor

Weak acoustic signals detection from heavy background noise plays an important role in different research fields. However, the detection limit, namely the detection capability of minimal detectable pressure, of sensitivity still hinders the performance of ordinary acoustic sensors. We propose an acoustic metamaterials-based sensor for weak signals detection. We show that the trapezoidal structure with gradient refractive index (GRIN) can effectively realize the pressure field enhancement through acoustic wave compression effect. The acoustic pressure amplitudes can be amplified more than 20 times around the maximum pressure gain frequencies even with different thicknesses of acrylic plates and measured positions, which makes it possible to achieve a broadband acoustic enhancement. Moreover, we numerically demonstrate that both harmonic and periodic impulse signals can be detected much easier based on the GRIN metamaterial due to the acoustic enhancement. In addition, we also experimentally demonstrate that harmonic and periodic impulse signals can be effectively recovered from the background noise due to the improved signal to noise ratios (SNRs). All the results indicate that acoustic metamaterials-based sensor can be well used for weak acoustic signals detection.