Recent progress in acoustic metamaterials and active piezoelectric acoustic metamaterials - A review

Ji, Guosheng; Huber, J. E.

doi:10.1016/j.apmt.2021.101260

Cited by 56 publications

(27 citation statements)

References 229 publications

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“…Although various advanced thin-film sensors, such as triboelectric sensors ( 6 – 9 ), have been developed for outstanding sensitivity, the advantage of their formation of a beamforming acoustic array is unclear. The spatial geometry of acoustic beamforming allows room for specially designed acoustic metamaterials, which are known for their sound manipulation capability ( 18 , 41 ). We thus show the first metamaterial spherical shell structure to omnidirectionally confine sound pressure in integrated piezoelectric defected cavities to harvest acoustic energy and record audio signal.…”

Section: Discussionmentioning

confidence: 99%

A wave-confining metasphere beamforming acoustic sensor for superior human-machine voice interaction

Chen

et al. 2022

Sci. Adv.

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Highly sensitive, source-tracking acoustic sensing is essential for effective and natural human-machine interaction based on voice. It is a known challenge to omnidirectionally track sound sources under a hypersensitive rate with low noise interference using a compact sensor. Here, we present a unibody acoustic metamaterial spherical shell with equidistant defected piezoelectric cavities, referred to as the metasphere beamforming acoustic sensor (MBAS). It demonstrates a wave-confining capability and low self-noise, simultaneously achieving an outstanding intrinsic signal-to-noise ratio (72 dB) and an ultrahigh sensitivity (137 mV pp /Pa or −26.3 dBV), with a range spanning the daily phonetic frequencies (0 to 1500 Hz) and omnidirectional beamforming for the perception and spatial filtering of sound sources. Moreover, the MBAS-based auditory system is shown for high-performance audio cloning, source localization, and speech recognition in a noisy environment without any signal enhancement, revealing its promising applications in various voice interaction systems.

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Section: Discussionmentioning

confidence: 99%

A wave-confining metasphere beamforming acoustic sensor for superior human-machine voice interaction

Chen

et al. 2022

Sci. Adv.

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“…Acoustic metamaterials are artificially manufactured materials designed to control, direct, and manipulate sound waves [13], [14]. In particular, they have been developed to modulate acoustic waves within specific frequencies for various applications including noise control [15], [16], sensing [17]- [19], filtering [20], [21], energy harvesting [22], [23], and so on [24]- [28]. While the realization of these unprecedented opportunities demonstrates a high degree-offreedom offered by acoustic metamaterials, their usage in real devices and consumer products is less explored.…”

Section: Introductionmentioning

confidence: 99%

Mitigating Inaudible Ultrasound Attacks on Voice Assistants With Acoustic Metamaterials

et al. 2023

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Voice assistants play an important role in facilitating human-machine interactions and have been widely used in audio consumer electronic products. However, it has been shown that they are susceptible to inaudible attacks in which the malicious signals are in the ultrasound regime and cannot be heard by human ears. In this study, we show that a judiciously designed acoustic metamaterial filter can mitigate such attacks by modulating the received signals by the microphones. The metamaterial filter is composed of rigid plates with individual holes which exhibit local resonance phenomena that suppress incoming waves at specific frequencies. The effectiveness of the metamaterial filter is confirmed by experiments which show that a combination of the holes can collectively distort the attack signals and protect the smart speakers. Moreover, normal audible signals are not affected by the proposed metamaterial, which adds to the flexibility of the device. The metamaterial filter has a small footprint and can be easily installed on various audio products. Our proposed strategy expands the capacity of acoustic metamaterials and improves the security of devices that use voice assistants.

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“…In recent years, acoustic metamaterials composed of active phases have received growing research interest, as discussed in the comprehensive review presented in [50]. The use of active elements, such as e.g.…”

Section: Introductionmentioning

confidence: 99%

Multifield nested metafilters for wave propagation control

Fantoni

Bosco²,

Bacigalupo³

2022

Extreme Mechanics Letters

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Recent progress in acoustic metamaterials and active piezoelectric acoustic metamaterials - A review

Cited by 56 publications

References 229 publications

A wave-confining metasphere beamforming acoustic sensor for superior human-machine voice interaction

A wave-confining metasphere beamforming acoustic sensor for superior human-machine voice interaction

Mitigating Inaudible Ultrasound Attacks on Voice Assistants With Acoustic Metamaterials

Multifield nested metafilters for wave propagation control

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