Gianluca Memoli | Searcharxiv

arXiv2025

Transmission Loss of a Labyrinthine Acoustic Metamaterial Augmented with Multichannel Feedforward Active Noise Control

Acoustic metamaterials and active noise control are two advanced noise control treatments that can typically offer performance that exceeds that of conventional passive noise control treatments. Acoustic metamaterials utilize sub-wavelength structures to realize sound field control, whilst active noise control treatments achieve control via the introduction of additional sources driven to generate a secondary sound field that interferes in a controlled way with the original, primary sound field. This paper presents an investigation into combining these two noise control techniques, to achieve enhanced noise control over a spatial region using a hybrid device. In particular, conventional feedforward active noise control is combined with a labyrinthine metasurface and the increase in performance offered by the hybrid solution is demonstrated.

physics.app-ph↗

arXiv2017

Metamaterial bricks and quantization of meta-surfaces

Controlling acoustic fields is crucial in diverse applications such as loudspeaker design, ultrasound imaging and therapy, or acoustic particle manipulation. The current approaches use fixed lenses or expensive phased arrays. Here, using a process of analogue-to-digital conversion and wavelet decomposition, we develop the notion of quantal meta-surfaces. The quanta here are small, pre-manufactured three-dimensional units - which we call metamaterial bricks - each encoding a specific phase delay. These bricks can be assembled into meta-surfaces to generate any diffraction-limited acoustic field. We apply this methodology to show experimental examples of acoustic focusing, steering and, after stacking single meta-surfaces into layers, the more complex field of an acoustic tractor beam. We demonstrate experimentally single-sided air-borne acoustic levitation using meta-layers at various bit-rates: from a 4-bit uniform to 3-bit non-uniform quantization in phase. This powerful methodology dramatically simplifies the design of acoustic devices and provides a key-step towards realising spatial sound modulators.

physics.class-ph↗