Browsing by Subject "Transmission loss"

Now showing 1 - 3 of 3

Open Access
Biomimetic acoustic metamaterial design for architectural applications
(2020-08) Yazıcı, Beyza
This study investigates the potentials of acoustic metamaterial (AMM) applications in room and building acoustics by means of impedance tube experiments. With their extreme properties in either sound absorption or transmission loss, AMMs can perform better than many traditional acoustic materials in buildings. Importantly, they are also more sustainable and hygienic than ﬁbrous and porous materials. Depending on the matrix material used, AMMs can vary in transparency and color. Considering both their acoustic and aesthetic values, this study develops diﬀerent types of metamaterial for possible uses as a partition wall, a surface layer, or a design element. The proposed metamaterials are primarily based on the exploration of ratios and forms from nature – the golden ratio, web-labyrinthine structures, genetic and neural systems such as DNA molecules and the synapse structures in the brain – reproduced on a sub-wavelength scale. These abstractions are then combined with the 3D space coiling and 3D labyrinth approaches of AMM design. Modules of the proposed AMMs are manufactured in a 3D printer and tested in an impedance tube to estimate their normal incidence sound absorption coeﬃcients and transmission loss characteristics. Based on the results obtained, the modules with the higher performances are used in the design of partition walls of varying heights. Two real-case architecture studios are simulated with and without the proposed AMM interventions over ﬁeld test-tuned acoustical models of the studios to assess the eﬀectiveness of such an approach in a possible acoustical design problem.
Open Access
Biomimetic metamaterial design simulation and evaluation for building acoustics by impedance measurements
(A S T M International, 2021-09-01) Yazıcı, Beyza; Gül, Zühre Sü
This study investigates the potentials of acoustic metamaterial (AMM) applications in room and building acoustics by means of impedance tube experiments. With their extreme properties in either sound absorption or transmission loss, AMMs can perform better than traditional acoustic materials in buildings. Importantly, they are also more sustainable and hygienic than fibrous and porous materials. Depending on the matrix material used, AMMs can vary in transparency and color. Considering both their acoustic and aesthetic values, this study develops different types of metamaterial for possible uses as a partition wall, a surface layer, or a design element. The proposed metamaterials are primarily based on the exploration of ratios and forms from nature—the golden ratio, web-labyrinthine structures, genetic and neural systems such as deoxyribonucleic acid (DNA) molecules, and the synapse structures in the brain—reproduced on a subwavelength scale. These abstractions are then combined with the 3-D space coiling and 3-D labyrinth approaches of AMM design. Modules of the proposed AMMs are manufactured in a 3-D printer and tested in an impedance tube to estimate their normal incidence sound absorption coefficients and transmission loss characteristics. Based on the results obtained, the modules with the higher performances are used in the design of partition walls of varying heights. Two real-case architecture studios are simulated with and without the proposed AMM interventions over field test–tuned acoustical models of the studios to assess the effectiveness of such an approach in a possible acoustical design problem.
Open Access
Fabrication and characterization of negative curvature hollow core polymer optical fibers for near-infrared light guidance
(2023-07) Rahman, Mahmudur
Polymer optical fibers (POFs) have attracted significant attention for their short-distance data transmission, industrial automation, and chemical and biological sensing applications. The low cost, lightweight, flexibility, accessibility, and ease of material processing features of the polymers make them superior to their silica counterparts. Moreover, compared to conventional POFs, hollow core polymer optical fibers (HCPOFs) exhibit light guidance through the air, significantly reducing material absorption loss in the near-infrared (NIR) region. Structuring the cladding part with the appropriate fiber material can further modify the light-guiding properties of HCPOF with low transmission loss in NIR. Several methods have already been employed for the successful fabrication of POFs, but the possibility of fabricating intricate geometry-based HCPOFs with these approaches and optimization of fabrication methods are yet to be resolved. This study explored the stack and draw technique and fused deposition modeling (3D printing) approaches to find the fabrication feasibility of long-length and intricate geometry-based negative curvature-based HCMPOFs with two different polymeric materials. A detailed investigation was carried out on the modified thermal drawing process to achieve well-structured HCMPOFs directly drawn at high tension from the fabricated preforms. Moreover, during the thermal drawing, expansion and contraction of the core and cladding part of the fibers were frequently observed. Inflation of the cladding tubes during the fiber drawing was required to preserve the designed structure in the fibers. This was achieved by applying gas pressurization inside the fibers in both preforms made by the stack and draw technique and 3D printing. Optical characterization is performed using Supercontinuum (SC) Laser in the 600 − 1700 nm wavelength range. Differences in the transmission spectra between core and cladding structures significantly prove the light-guiding prop-erties of the proposed HCMPOFs. The transmission losses of the HCMPOFs were measured using Optical Spectrum Analyzer (OSA), and were found to average 49.26 dB/m for stack and draw-based fabricated six-tube HCMPOF and 16 dB/m for 3D printed six-pointed star cladding-based HCMPOF. Further investigation is carried out on bend-induced loss against the mechanical effects of the 3D printed intricate geometry-based HCMPOF at different bending angles. The lower transmission loss with a low bend-induced loss against the mechanical effects of HCMPOFs explicitly shows the potential of using HCMPOFs as an alternative to conventional polymer optical fibers for visible and infrared light guidance.