Effect of bagasse content on low frequency acoustic performance of soy oil‐based biodegradable foams filled with bagasse and regulation mechanism analysis

2021 ◽  
pp. 51457
Author(s):  
Jin Zhao ◽  
Zengcheng Yu ◽  
Huafeng Tian ◽  
Shilin Liu ◽  
Xiaogang Luo
Keyword(s):  
Low Frequency ◽  
Regulation Mechanism ◽  
Soy Oil ◽  
Mechanism Analysis ◽  
Acoustic Performance

Sound insulation performance of pyramidal truss core sandwich structure with frame

2021 ◽  
pp. 109963622110288
Author(s):  
Yu-Zhou Wang ◽  
Li Ma
Keyword(s):  
Mechanical Properties ◽  
Sandwich Structure ◽  
Transmission Loss ◽  
Low Frequency ◽  
Sound Insulation ◽  
Geometrical Parameters ◽  
Acoustic Performance ◽  
Truss Core ◽  
Pyramidal Truss ◽  
Wave Angle

Recently, sandwich structures have been widely used in different fields because of their good mechanical properties, but these structures are weak in acoustic performance. In this paper, by combining pyramidal truss core sandwich structure with frame, a new structure is proposed with both good mechanical properties and excellent acoustic performance at low frequency. An analytical model of the pyramidal truss core sandwich structure with frame is developed to investigate the sound transmission loss (STL) performance. Finite element method (FEM) is also used to investigate the STL performance at low frequency. The effects of the incident wave angle and the geometrical parameters on the STL of the structure are discussed.

Experimental study of smart sound absorber using multimode electromechanical coupling control in the low-frequency range

2021 ◽  
Vol 263 (3) ◽  
pp. 3800-3810
Author(s):  
Xiang Liu ◽  
Keming Wu ◽  
Lixi Huang
Keyword(s):  
Electromechanical Coupling ◽  
Electrical Response ◽  
Low Frequency ◽  
Design Procedure ◽  
Frequency Range ◽  
Acoustic Performance ◽  
Sound Absorber ◽  
Multiple Frequencies ◽  
Broadband Sound ◽  
Shunt Circuit

To construct a smart sound absorber in the low-frequency range with a wide control band, a piezoelectric ceramic (PZT) shunted with multiple resonance circuit is attached onto a micro-perforated panel (MPP) to perform as a smart sound absorber. The absorption can be controlled by the shunt circuit parameters conveniently. This smart micro-perforated panel (MPP) is investigated experimentally to explore the feasibility and design procedure in practical use. Based on the coupling among the acoustical, electrical, and mechanical fields, the proposed broadband sound absorber can achieve good acoustic performance on subwavelength scales. The electrical response of the shunt circuit is tested with a Network Analyzer. The acoustic performance of the smart sound absorber is measured in an impedance tube with the two-microphone transfer function method. The experimental results validate that the shunt circuit can resonate with the PZT patch at multiple frequencies, and hence improve the sound absorption of the smart absorber at these frequencies.

Surface Effect Mechanism Analysis for Vibrational Rotary Forging

2011 ◽  
Vol 314-316 ◽  
pp. 753-758
Author(s):  
Rong Hai Zhang ◽  
Ning Yuan Zhu ◽  
Gai Pin Cai
Keyword(s):  
Surface Effect ◽  
Low Frequency ◽  
Contact Boundary ◽  
Mechanism Analysis ◽  
Vibration Period ◽  
Rotary Forging ◽  
Effect Mechanism ◽  
Low Frequency Vibration ◽  
Highly Nonlinear ◽  
Plastic Process

As a contact of vibrational rotary forging is highly nonlinear, the contact area and boundary between rotary toolhead and workpiece had more accurate calculation, made the contact boundary more tally with the actual situation. For a surface effect is of complexity for vibrational rotary forging, a vibrational rotary forging visco-elasticity plasticity model was built, and the visco-elasticity spatial matrix and the visco-plasticity spatial matrix were derived by the generalized Hooke's law in elasticity theory and the increase theory in mechanics of plasticity, then by the finite element founction of MATLAB for the surface effect analyzed during the vibrational rotary forging deformation, it is shown as blow: the surface effect should be appeared with high frequency vibration or low frequency vibration, but there are some conditions for surface effect produced during plastic process, and then the hypothesis that the friction vector is reversal of deformation load, and it is benefit to deformation process during the part of time in vibration period is validated.

scholarly journals Analysis and Optimization of Micro Speaker-Box Using a Passive Radiator in Portable Device

2017 ◽  
Vol 42 (4) ◽  
pp. 753-760 ◽  
Author(s):  
Yuan-Wu Jiang ◽  
Joong-Hak Kwon ◽  
Hyung-Kyu Kim ◽  
Sang-Moon Hwang
Keyword(s):  
Rapid Development ◽  
Low Frequency ◽  
Main Concern ◽  
The Finite Element Method ◽  
Acoustic Characteristics ◽  
Acoustic Performance ◽  
Tablet Pcs ◽  
Electromagnetic Vibration ◽  
The One ◽  
Two Degree Of Freedom

Abstract With the rapid development of multimedia devices such as smart phones and tablet PCs, microspeakers have been recently increasingly used for audio equipment. Improving the acoustic performance of a microspeaker is always a main concern, especially in the low frequency range. To avoid sound cancelation, a microspeaker unit is usually inserted into a speaker box. A passive radiator is also used in speaker boxes to improve the sound performance in the loudspeaker system. However, passive radiators have not been applied into microspeaker system. In this study, a speaker box with a passive radiator was analyzed and optimized to achieve a higher Sound Pressure Level (SPL) in a microspeaker system. The Finite Element Method (FEM), two-degree-of-freedom (DOF) vibration theory, and a plane circular piston sound source were used to study the electromagnetic, vibration, and acoustic characteristics, respectively. Optimization was conducted by changing the mass, stiffness, and size of the passive radiator. Based on the optimized parameters, a new sample was manufactured. The experiment results show that the SPL of the optimized speaker box with a passive radiator is improved by 5 dB at 200 Hz compared with the one without a radiator. The analysis results also matched the experiment results.

scholarly journals Mechanism Analysis of a Low-Frequency Disc Brake Squeal Based on an Energy Feed-In Method for a Dual Coupling Subsystem

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Yidong Wu
Keyword(s):  
Vibration Mode ◽  
Low Frequency ◽  
Element Model ◽  
Disc Brake ◽  
Mechanism Analysis ◽  
Brake Squeal ◽  
Complex Mode ◽  
Vehicle Noise ◽  
Complex Modal Analysis ◽  
The Difference

Brake squeal is a major component of vehicle noise. To explore the mechanism of the low-frequency brake squeal, a finite element model of an automobile disc brake was established, and a complex mode numerical simulation was performed. According to the unstable modes stemming from the complex modal analysis results, the low-frequency range brake squeal can be determined. Based on an energy feed-in method, the coupling subsystems of the piston-caliper and the disc-pad were established, and a calculation formula for the feed-in energy of the dual coupling subsystem was derived. The results showed that when the feed-in energy of the dual coupling subsystem is close to zero, the complex mode cannot be excited at the corresponding frequency. In addition, the difference in feed-in energy between the two coupling subsystems is positively correlated with the probability of the brake squeal, which can be used to determine the complex mode under which the brake squeal may occur. The greater the feed-in energy of a coupling subsystem is, the more likely it is that the maximum brake vibration mode will appear at this subsystem or its adjacent parts. The increase in brake oil pressure will eliminate some lower-frequency sounds but will not change the frequency of the original low-frequency brake squeals.

Optimization of an absorbing surface with 2D Helmholtz resonators for reduced sensitivity to the incidence angle

2021 ◽  
Vol 263 (4) ◽  
pp. 2114-2125
Author(s):  
Diana Maria Garza-Agudelo ◽  
Vicente Cutanda Henriquez ◽  
Cheol-Ho Jeong ◽  
Peter Risby Andersen
Keyword(s):  
Absorption Coefficient ◽  
Incidence Angle ◽  
Low Frequency ◽  
Large Degree ◽  
Acoustic Performance ◽  
Helmholtz Resonators ◽  
Sound Control ◽  
Extended Frequency ◽  
High Absorption Coefficient ◽  
High Absorption

It has been shown in several recent publications that acoustic materials consisting of a combination of resonators tuned to different frequencies can render high absorption coefficient values over an extended frequency range while maintaining compactness. This makes them attractive solutions for applications in which low frequency sound control is needed, and/or when there are significant space constraints. Nevertheless, the acoustic performance of these surfaces varies with the angle at which a wave impinges on the surface. The changes in the absorption characteristics with the incidence angle occur both on the maximum absorption coefficient, and on the effective frequency bandwidth. Numerical optimization is a tool that can help realize designs with a large degree of geometrical freedom, and using this framework we have demonstrated an array of coupled 2D Helmholtz resonators that is less sensitive to changes in the incidence angle.

Sound reflection of acoustic porous metasurfaces under uniform mean flow

2021 ◽  
Vol 263 (4) ◽  
pp. 2601-2608
Author(s):  
Renhao Qu ◽  
Jingwen Guo ◽  
Yi Fang ◽  
Siyang Zhong
Keyword(s):  
Surface Wave ◽  
Critical Incident ◽  
Incident Angle ◽  
Low Frequency ◽  
Noise Attenuation ◽  
Mean Flow ◽  
Background Flow ◽  
Reflected Waves ◽  
Acoustic Performance ◽  
Sub Wavelength

Acoustic metasurfaces are artificial 2D structures with a sub-wavelength thickness that can realize some exotic properties such as non-trivial refraction, broadband and low frequency absorption. However, most relevant studies are still in a static medium, hindering their realistic applications in aviation, where background flow exists. To address it, the effects of mean flow on the acoustic performance of metasurfaces, which is designed based on the generalized Snell's law (GSL) to achieve anomalous reflections, are systemically studied. Firstly, an analytical model of GSL taking the effect of background uniform mean flow into account is built, in which the wavenumbers of both incident and reflected waves are corrected. Then, taking an acoustic porous metasurface for instance, the effectiveness of the derived model is validated by numerical simulations. Results reveal that the reflected waves are deflected in the presence of background flow. The critical incident angle, at which the incident sound wave is converted to surface wave, decreases with the increasing flow velocity. Since the converted surface wave can only propagate along the metasurface, there is little sound energy radiated into far field, which is benefit for the noise attenuation in the presence of flow.

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