Abstract
Transceiving ultra-weak sound typically relies on signal pre-amplification at the transmitting end via active electro-acoustic devices, which inherently perturbs the environment in the form of noise that inevitably leads to information leakage. Here we demonstrate a passive remote-whispering metamaterial (RWM) enabling weak airborne sound at audible frequencies to reach unprecedented signal enhancement without altering the detected ambient soundscape, which is based on the extraordinary scattering properties of a metamaterial formed by a pair of self-resonating subwavelength Mie meta-cavities, constituting the acoustic analogy of Förster resonance energy transfer. We demonstrate efficient non-radiative sound transfer over distances hundreds times longer than the radius of the meta-cavities, which enables the RWM to recover weak sound signals completely overwhelmed by strong noise with enhanced signal-to-noise ratio from −3 dB below the detection limit of 0 dB in free space to 17.7 dB.
Highlights
Transceiving ultra-weak sound typically relies on signal pre-amplification at the transmitting end via active electro-acoustic devices, which inherently perturbs the environment in the form of noise that inevitably leads to information leakage
The physical system representing sound transfer between resonant objects strongly coupled to one another can be described using the coupled-mode theory, which has been extensively studied in short-range and mid-range wireless electromagnetic power transfer systems[35,36,37,38]
In order to demonstrate the effect of the remote-whispering metamaterial (RWM) universally, we develop a theoretical model on the basis of a rigorous acoustic scattering theory, which applies well for both the near-field and far-field configurations
Summary
Transceiving ultra-weak sound typically relies on signal pre-amplification at the transmitting end via active electro-acoustic devices, which inherently perturbs the environment in the form of noise that inevitably leads to information leakage. We propose a remote whispering metamaterial (RWM) scheme that incorporates a pair of coupled Mie resonant objects around both the weak source and the receiver site at a deepsubwavelength scale [see Fig. 1c].
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