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A study on the design of an acoustic actuator
No full text학위논문(석사) - 한국과학기술원 : 기계공학전공, 2004.2, [ vii, 94 p. ]한국과학기술원 : 기계공학전공
Evaluation of System Configuration to Check the Suitability for the Sound Field Rendering Using the Inverse Approach
No full textZero Poisson's ratio metamaterial and meander-inspired diaphragms for enhancing low-frequency performance in flat-panel loudspeaker
No full textFlat-panel loudspeakers, designed with a planar configuration, provide space-efficient audio solutions; however, they frequently exhibit limitations in low-frequency performance due to constrained diaphragm displacement. This study addresses the challenge of enhancing low-frequency sound pressure levels in flat-panel loudspeakers while preserving their slim profiles. We demonstrate that integrating metamaterial-inspired Zero Poisson's Ratio Diaphragms (ZPD) and Edge-Patterned Diaphragms (EPD) significantly improves low-frequency sound pressure levels in piezoelectric flat-panel loudspeakers. The selection of ZPD and EPD designs leverages the unique monoclastic behavior of zero Poisson's ratio structures and the high displacement characteristics of meanderspring patterns, respectively, which results in increased diaphragm flexibility and displacement. Our finite element analysis, supported by experimental results, shows that both ZPD and EPD designs enhance sound pressure levels below 200 Hz compared to a conventional bare diaphragm, achieving maximum enhancements of 11.6 dB and 20.0 dB, respectively. These findings advance the field by introducing diaphragm designs that exploit zero Poisson's ratio principles and structural patterns to improve acoustic performance without increasing overall thickness. The proposed metamaterials and structural designs demonstrate considerable potential for acoustic applications across multimedia systems, portable devices, and automotive audio, where superior low-frequency response in slim-profile loudspeakers is highly beneficial.
Improved Flat Frequency Response of Conical Shellular Metamaterial-Enabled Flat Panel Loudspeaker
No full textA piezoelectric flat panel loudspeaker operates by utilizing a piezoelectric film actuator to vibrate a diaphragm, offering advantages in miniaturization, embedding, and spatial efficiency. However, achieving high sound pressure levels (SPL) at low frequencies and maintaining a flat frequency response remains challenging. This study presents a Conical Shellular Sandwich Diaphragm (CSSD), derived from conical shellular metamaterials, which combines lightweight properties with high stiffness. The CSSD enhances low-frequency SPL and improves frequency response flatness through structural optimization, eliminating the need for complex systems. Finite element analysis identifies optimal geometric parameters for the CSSD unit cell, resulting in an 11.5 dB increase in low-frequency SPL and a 53% reduction in peak-dip deviation across the 200 Hz-20 kHz range, compared to a conventional Flat Panel Diaphragm (FPD). These enhancements stem from a reduction in the CSSD's effective mass (meff) to one-hundredth of an equivalent-volume FPD and an increase in effective bulk modulus (keff) relative to structures with the same mass. Experimental tests of 3D-printed CSSD and FPD prototypes integrated with piezoelectric actuators match the simulation results. This study demonstrates the potential of mechanical metamaterials to address design limitations in flat panel loudspeakers, enabling improved sound quality and simpler configurations for commercial use.
Finite elastic metasurface attachment for flexural vibration amplification
No full textIn this study, we propose a compact elastic metasurface structure that confines and amplifies flexural vibration energy over an internal local area. The proposed structure utilizes the well-known internal wave trapping mechanism of metasurfaces, developed for an incident wave beyond the critical angle. Our novel method is the first to optimize the metasurface structure for wave energy amplification and to realize a metasurface structure in practical attachment form with a finite compact dimension. These aspects clearly distinguish the proposed metasurface structure from conventional structures, which have mainly been developed for wave energy dissipation and are typically realized in an unpractical form. The proposed metasurface structure can be divided into three finite regions in terms of role: metasurface, phase-matching, and attaching regions. We validated our proposed metasurface through experiments whose results show an amplification of the input flexural vibration amplitude of more than twenty times. This drastic amplification was achieved by the intrinsic negligible damping characteristic of the pro-posed simple metallic structure. In this study, the detailed working physics of the proposed structure and the physical significance of the constituents are thoroughly addressed with nu-merical simulations.
Cross-comparison of the optical and acoustical calibration methods for microphones based on microelectromechanical system technologies
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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