A Model for the Fast Determination of Modal Sound Transmission of Large Rectangular Opening

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Jiazhu Li ◽  
Rui Zhang ◽  
Shen Chen ◽  
Can Li ◽  
Jian Chen
Keyword(s):  
Wave Equations ◽  
Three Dimensional ◽  
Sound Transmission ◽  
Computational Effort ◽  
Sound Insulation ◽  
Fast Determination ◽  
High Frequencies ◽  
Higher Order Modes ◽  
Insulation Performance

Abstract The existence of openings affects the sound insulation performance of structures significantly. The determination of sound transmission through large rectangular openings is often time-consuming, because of the large number of modes, especially if there is a need to go to high frequencies. A model is proposed and detailed based on three-dimensional wave equations, the transfer matrix method, and modal superposition. The viscous and thermal boundary layer effects have been concerned; hence, the model accuracy for narrow slits was improved. The computational effort is significantly decreased by neglecting the cross-modal sound transmission. The accuracy of this model is validated by comparing it with the existing model, the measurement, and the acoustic finite element method. The study of sound transmission behavior of higher-order modes is performed. The modal sound transmission is predicted and compared for several modes. The phenomenon that is different from that of the plane wave situation is found and discussed.

HIGH-FREQUENCY DIFFRACTION BY A SPHERE

1961 ◽  
Vol 39 (10) ◽  
pp. 1486-1494
Author(s):  
C. L. Tang
Keyword(s):  
Plane Wave ◽  
High Frequency ◽  
Rotational Symmetry ◽  
Asymptotic Series ◽  
Three Dimensional ◽  
Shadow Region ◽  
High Frequencies ◽  
Present Procedure ◽  
Dimensional Object

A systematic procedure is given for the determination of the asymptotic series directly from the Helmholtz equation and the boundary conditions for the field in the shadow region of a sphere illuminated by a plane wave at high frequencies. The first two terms in the series for the shadow region, including the regions near the axial caustic and the boundary layer near the surface of the sphere, are explicitly evaluated. The present procedure can be generalized to any smooth convex three-dimensional object with a rotational symmetry, illuminated by a plane wave in the direction of the axis of rotational symmetry.

scholarly journals Generation of Novel-Substrate-Accepting Biphenyl Dioxygenases through Segmental Random Mutagenesis and Identification of Residues Involved in Enzyme Specificity

2006 ◽  
Vol 72 (3) ◽  
pp. 2191-2199 ◽  
Author(s):  
Marco Zielinski ◽  
Silke Kahl ◽  
Christine Standfuß-Gabisch ◽  
Beatriz Cámara ◽  
Michael Seeger ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Random Mutagenesis ◽  
Major Influence ◽  
Enzyme Specificity ◽  
Three Dimensional Model ◽  
Wild Type Enzyme ◽  
High Frequencies ◽  
Burkholderia Xenovorans ◽  
Function Relationship

ABSTRACT Aryl-hydroxylating dioxygenases are of interest for the degradation of persistant aromatic pollutants, such as polychlorobiphenyls (PCBs), or as catalysts for the functionalization of aromatic scaffolds. In order to achieve dioxygenation of technical mixtures of PCBs, enzymes with broadened or altered substrate ranges are essential. To alter the substrate specificity of the biphenyl dioxygenase (BphA) of Burkholderia xenovorans LB400, we applied a directed evolution approach that used structure-function relationship data to target random mutageneses to specific segments of the enzyme. The limitation of random amino acid (AA) substitutions to regions that are critical for substrate binding and the exclusion of AA exchanges from positions that are essential for catalytic activity yielded enzyme variants of interest at comparatively high frequencies. After only a single mutagenic cycle, 10 beneficial variants were detected in a library of fewer than 1,000 active enzymes. Compared to the parental BphA, they showed between 5- and 200-fold increased turnover of chlorinated biphenyls, with substituent patterns that rendered them largely recalcitrant to attack by BphA-LB400. Determination of their sequences identified AAs that prevent the acceptance of specific PCBs by the wild-type enzyme, such as Pro334 and Phe384. The results suggest prime targets for subsequent cycles of BphA modification. Correlations with a three-dimensional model of the enzyme indicated that most of the exchanges with major influence on substrate turnover do not involve pocket-lining residues and had not been predictable through structural modeling.

An improved approach for normal-incidence sound transmission loss measurement using a four-microphone impedance tube

2020 ◽  
pp. 107754632092690
Author(s):  
Zechao Li ◽  
Sizhong Chen ◽  
Zhicheng Wu ◽  
Lin Yang
Keyword(s):  
Transfer Matrix ◽  
Sound Absorption ◽  
Transmission Loss ◽  
Sound Transmission ◽  
Normal Incidence ◽  
Sound Insulation ◽  
Sound Transmission Loss ◽  
The Common ◽  
Wavefield Decomposition ◽  
Insulation Performance

The main aim of this study is to introduce an improved method for determining the sound properties of acoustic materials which is more precise than the common wavefield decomposition method and simpler than the common transfer matrix method. In the first part of the article, a group of formulae for calculating sound transmission loss is represented by combining the wavefield decomposition and transfer matrix methods. Subsequently, a formula for calculating sound absorption coefficients is derived from these formulae by definition. Furthermore, the present formulae are validated by comparing the experimental results achieved with the present formulae and those results obtained by other methods recorded in published articles. Eventually, it is demonstrated that the method can accurately measure the sound insulation performance of materials and the sound absorption properties of limp and lightweight materials.

Impact sound transmission: experiments of control at the receiver room

2021 ◽  
Vol 263 (1) ◽  
pp. 5595-5599
Author(s):  
Davi Akkerman ◽  
Paola Weitbrecht ◽  
Mariana Shieko ◽  
Marcel Borin ◽  
Leonardo Jacomussi
Keyword(s):  
Social Housing ◽  
Sound Transmission ◽  
Field Tests ◽  
Sound Level ◽  
Sound Insulation ◽  
Total Cost ◽  
Acoustic Performance ◽  
The Impact ◽  
Insulation Performance

Considering Impact sound level requirements accomplishment in Brazil, floating floors are still considered as an inviable solution for building companies due to the implications in the total cost of building, mainly for social housing. Alternative and sometimes cheaper solutions are those undertaken in the receiver room. However, the lack of laboratory and field tests on the acoustic performance of this type of system is still a barrier for acoustic designing in Brazil. The aim of this paper is to study and validate different constructive solutions developed jointly with building companies for improving the impact sound insulation performance on the receiving room of new Brazilian housing constructions.

AB INITIO CALCULATIONS OF THE ELECTRONIC STRUCTURES AND BIOLOGICAL FUNCTIONS OF PROTEIN MOLECULES

2002 ◽  
Vol 16 (30) ◽  
pp. 1151-1162 ◽  
Author(s):  
HAOPING ZHENG
Keyword(s):  
Ab Initio ◽  
Trypsin Inhibitor ◽  
Electronic Structures ◽  
Biological Function ◽  
Three Dimensional ◽  
Protein Molecule ◽  
Computational Effort ◽  
Biological Functions ◽  
Protein Molecules

The self-consistent cluster-embedding (SCCE) calculation method reduces the computational effort from M3 to about M1 (M is the number of atoms in the system) with precise calculations. Thus the ab initio, all-electron calculation of the electronic structure and biological function of protein molecule has become a reality, which will promote new proteomics considerably. The calculated results of two real protein molecules, the trypsin inhibitor from the seeds of squash Cucurbita maxima (CMTI-I, 436 atoms) and the ascaris trypsin inhibitor (912 atoms, two three-dimensional structures), will be presented in this paper. The reactive sites of the inhibitors are determined and explained. The accuracy of structure determination of the inhibitors are tested theoretically.

Reduction of Sound Transmission Through Finite Clamped Metamaterial-Based Double-Wall Sandwich Plates with Poroelastic Cores

2019 ◽  
Vol 105 (5) ◽  
pp. 850-868
Author(s):  
Jingru Li ◽  
Peng Yang ◽  
Sheng Li
Keyword(s):  
Vibration Isolation ◽  
Transmission Loss ◽  
Sound Transmission ◽  
Sound Insulation ◽  
Sandwich Plates ◽  
Low Frequencies ◽  
Finite Structures ◽  
The Galerkin Method ◽  
Insulation Performance ◽  
Double Wall

Finite structures play a more realistic role in applications designed for sound and vibration isolation. Doublepanel structure with poroelastic cores is able to exhibit a superior sound insulation performance in mid-high frequency range, while is relatively inferior to isolate waves at low frequencies. In order to further reduce sound transmission at low frequencies and cater for the actual situation, this paper decides to introduce the metamaterial concept into finite double-wall sandwich plates and presents an analytical model to calculate the sound transmission loss through the metamaterial-based double-panel with fully clamped boundary conditions. The metamaterial-based double-wall sandwich plates are constructed by replacing the bare panel with the metamaterial plate, consisting of a homogeneous plate and periodically attached local resonators. Biot's theory is used to examine the wave propagation in the poroelastic medium. The vibro-acoustic problem of the proposed sandwich plate is solved by employing the modal superposition theory and the Galerkin method. Numerical results show that the sound transmission is significantly reduced at low frequencies. Unique phenomena caused by attached local resonators are explained and the eff ects of resonator inerter, incident angles and damping on the sound insulation properties are also studied.

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