An official website of the United States government
Achieving sound attenuation across a broad frequency range while maintaining adequate ventilation remains a significant challenge in acoustic engineering, as there exists a rigid trade-off between attenuation ability and ventilation. In this Letter, we propose a double-layered microperforated meta-shells to serve as broadband acoustic ventilation barrier. Multiple scattering theory is first employed to characterize sound attenuation performance of the proposed design in terms of both sound absorption and transmission loss, which is not reported before. Experimental result demonstrates a good enhancement of absorption due to the insertion of inner shell with a specific perforation rate of micro cores. The mechanism can be attributed to the inter-cell coupling, which is further utilized to devise a different configuration by wrapping the meta-shell with porous sponge. It is found that adding an extra layer of sponge can further improve the low-frequency attenuation performance. The proposed broadband sound barrier with effective ventilation can find potential applications in architectural acoustics and office noise insulation.
more »
« less
Ultra-broadband low-frequency high-efficiency acoustic energy harvesting with metamaterial-enhanced loudspeakers
Acoustic energy harvesters (AEHs) open up opportunities to recycle noise waste and generate electricity. They provide potential power solutions to a wide range of sensors. However, the practicality of AEHs has long been limited by their narrow bandwidths and low efficiencies. In this study, we present an ultra-broadband AEH and a highly efficient AEH that transforms sound energy into usable electrical power. Our broadband device comprises an electrodynamic loudspeaker driver and an optimized acoustic metamaterial matching layer and is capable of converting 7.6% to 15.1% of total incident sound energy from 50 to 228 Hz. Moreover, we demonstrate that by replacing the loudspeaker surround with a lower-loss material such as PDMS, the energy conversion rate can be significantly increased to 67%. The proposed broadband AEH has a fractional bandwidth eight times the state-of-the-art, while the proposed highly efficient AEH has a peak efficiency three times the state-of-the-art. The outstanding performance makes our designs cost-effective and scalable solutions for noise reduction and power generation.
more »
« less
- Award ID(s):
- 1951106
- PAR ID:
- 10525533
- Publisher / Repository:
- AIP
- Date Published:
- Journal Name:
- Applied Physics Letters
- Volume:
- 123
- Issue:
- 7
- ISSN:
- 0003-6951
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
The goal of this study is to introduce practical state-of-the-art considerations for designing a highly efficient power generation, transmission, and conversion chain system, PGTCC, to power up the front-end’s electronics that acquire satisfactory EEG signal acquisition in a portable wireless and battery-free EEG cap. Several solutions, strategies, and unique configurations have been presented to reach this goal, including, a highly efficient and compact resonance-inductive link, multi-resonator power transfer, use of magnetized materials to improve power transmission efficiency, closed-loop power transmission, and a highly efficient power conversion chain. The proposed design has the potential to significantly improve the total efficiency and supply stable power for the front-end units that include the EEG signal, filtering, noise cancelation amplification units, processing units, and transceivers.more » « less
-
null (Ed.)The primary noise sources of the vehicle are the engine, exhaust, aeroacoustic noise, and tire–pavement interaction. Noise generated by the first three factors can be reduced by replacing the combustion engine with an electric motor and optimizing aerodynamic design. Currently, a dominant noise within automobiles occurs from the tire–pavement interaction over a speed of 70–80 km/h. Most noise suppression efforts aim to use sound absorbers and cavity resonators to narrow the bandwidth of acoustic frequencies using foams. We demonstrate a technique utilizing acoustic metasurfaces (AMSes) with high reflective characteristics using relatively lightweight materials for noise reduction without any change in mechanical strength or weight of the tire. A simple technique is demonstrated that utilizes acoustic metalayers with high reflective characteristics using relatively lightweight materials for noise reduction without any change in mechanical strength or weight of the tire. The proposed design can significantly reduce the noise arising from tire–pavement interaction over a broadband of acoustic frequencies under 1000 Hz and over a wide range of vehicle speeds using a negative effective dynamic mass density approach. The experiment demonstrated that the sound transmission loss of AMSes is 2–5 dB larger than the acoustic foam near the cavity mode, at 200–300 Hz. The proposed approach can be extended to the generalized area of acoustic and vibration isolation.more » « less
-
Wireless assistive listening devices (ALDs), such as induction loops, radio-frequency transmitters, and digital streaming systems, improve accessibility for people with hearing loss by transmitting from a venue’s sound system directly to the listener. Today, ALDs are used primarily for lectures and performances. When paired with advanced hearing devices, however, they could form part of an augmented listening system that lets users "remix" sounds in their environment, including from loudspeakers in public spaces. For example, users could amplify public announcements or suppress background music while having a conversation. In the proposed system, a binaural adaptive filter uses the ALD signal to estimate the loudspeaker sound at the ears. The hearing device can then either enhance or remove the loudspeaker sound in the hearing device output while preserving other nearby sounds. We demonstrate the proposed system using several commercial ALDs and assess the effects of delay, bandwidth, distortion, and noise on real-world system performance.more » « less
-
The acoustic and aerodynamic fields of blunt porous plates are examined experimentally in an effort to mitigate trailing-edge bluntness noise. The plates are characterized by a single dimensionless porosity parameter identified in previous works that controls the influence of porosity on the sound field. Hot-wire anemometry interrogates the velocity field to connect turbulence details of specific regions to flow noise directivity and beamforming source maps. Porous plates are demonstrated to reduce the bluntness-induced noise by up to 17 dB and progressively suppress broadband low-frequency noise as the value of the porosity parameter increases. However, an increase in this parameter also increases the high-frequency noise created by the pores themselves. The same highly perforated plate characterized by a large value of the porosity parameter reduces the bluntness-induced vortex shedding that is present in the wake of the impermeable plate. Lastly, pore shape and positional alignment are shown to have a complex effect on the acoustic field. Among the porosity designs considered, plates with circular pores are most effective for low-frequency noise reductions but generate high-frequency noise. No meaningful difference is found between the acoustic spectra from plates of the same open-area fraction with pores aligned along or staggered about the flow direction.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1063/5.0158079
