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Pneumatically-Actuated Acoustic Metamaterials Based on Helmholtz Resonators

Metamaterials are periodic structures which offer physical properties not found in nature. Particularly, acoustic metamaterials can manipulate sound and elastic waves both spatially and spectrally in unpreceded ways. Acoustic metamaterials can generate arbitrary acoustic bandgaps by scattering sound...

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Autores principales: Hedayati, Reza, Lakshmanan, Sandhya
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7143092/
https://www.ncbi.nlm.nih.gov/pubmed/32210047
http://dx.doi.org/10.3390/ma13061456
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author Hedayati, Reza
Lakshmanan, Sandhya
author_facet Hedayati, Reza
Lakshmanan, Sandhya
author_sort Hedayati, Reza
collection PubMed
description Metamaterials are periodic structures which offer physical properties not found in nature. Particularly, acoustic metamaterials can manipulate sound and elastic waves both spatially and spectrally in unpreceded ways. Acoustic metamaterials can generate arbitrary acoustic bandgaps by scattering sound waves, which is a superior property for insulation properties. In this study, one dimension of the resonators (depth of cavity) was altered by means of a pneumatic actuation system. To this end, metamaterial slabs were additively manufactured and connected to a proportional pressure control unit. The noise reduction performance of active acoustic metamaterials in closed- and open-space configurations was measured in different control conditions. The pneumatic actuation system was used to vary the pressure behind pistons inside each cell of the metamaterial, and as a result to vary the cavity depth of each unit cell. Two pressures were considered, P = 0.05 bar, which led to higher depth of the cavities, and P = 0.15 bar, which resulted in lower depth of cavities. The results showed that by changing the pressure from P = 0.05 (high cavity depth) to P = 0.15 (low cavity depth), the acoustic bandgap can be shifted from a frequency band of 150–350 Hz to a frequency band of 300–600 Hz. The pneumatically-actuated acoustical metamaterial gave a peak attenuation of 20 dB (at 500 Hz) in the closed system and 15 dB (at 500 Hz) in the open system. A step forward would be to tune different unit cells of the metamaterial with different pressure levels (and therefore different cavity depths) in order to target a broader range of frequencies.
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spelling pubmed-71430922020-04-14 Pneumatically-Actuated Acoustic Metamaterials Based on Helmholtz Resonators Hedayati, Reza Lakshmanan, Sandhya Materials (Basel) Article Metamaterials are periodic structures which offer physical properties not found in nature. Particularly, acoustic metamaterials can manipulate sound and elastic waves both spatially and spectrally in unpreceded ways. Acoustic metamaterials can generate arbitrary acoustic bandgaps by scattering sound waves, which is a superior property for insulation properties. In this study, one dimension of the resonators (depth of cavity) was altered by means of a pneumatic actuation system. To this end, metamaterial slabs were additively manufactured and connected to a proportional pressure control unit. The noise reduction performance of active acoustic metamaterials in closed- and open-space configurations was measured in different control conditions. The pneumatic actuation system was used to vary the pressure behind pistons inside each cell of the metamaterial, and as a result to vary the cavity depth of each unit cell. Two pressures were considered, P = 0.05 bar, which led to higher depth of the cavities, and P = 0.15 bar, which resulted in lower depth of cavities. The results showed that by changing the pressure from P = 0.05 (high cavity depth) to P = 0.15 (low cavity depth), the acoustic bandgap can be shifted from a frequency band of 150–350 Hz to a frequency band of 300–600 Hz. The pneumatically-actuated acoustical metamaterial gave a peak attenuation of 20 dB (at 500 Hz) in the closed system and 15 dB (at 500 Hz) in the open system. A step forward would be to tune different unit cells of the metamaterial with different pressure levels (and therefore different cavity depths) in order to target a broader range of frequencies. MDPI 2020-03-23 /pmc/articles/PMC7143092/ /pubmed/32210047 http://dx.doi.org/10.3390/ma13061456 Text en © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Hedayati, Reza
Lakshmanan, Sandhya
Pneumatically-Actuated Acoustic Metamaterials Based on Helmholtz Resonators
title Pneumatically-Actuated Acoustic Metamaterials Based on Helmholtz Resonators
title_full Pneumatically-Actuated Acoustic Metamaterials Based on Helmholtz Resonators
title_fullStr Pneumatically-Actuated Acoustic Metamaterials Based on Helmholtz Resonators
title_full_unstemmed Pneumatically-Actuated Acoustic Metamaterials Based on Helmholtz Resonators
title_short Pneumatically-Actuated Acoustic Metamaterials Based on Helmholtz Resonators
title_sort pneumatically-actuated acoustic metamaterials based on helmholtz resonators
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7143092/
https://www.ncbi.nlm.nih.gov/pubmed/32210047
http://dx.doi.org/10.3390/ma13061456
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