3 edition of **Modal element method for scattering of sound by absorbing bodies** found in the catalog.

Modal element method for scattering of sound by absorbing bodies

Kenneth J. Baumeister

- 38 Want to read
- 14 Currently reading

Published
**1992**
by National Aeronautics and Space Administration, For sale by the National Technical Information Service in [Washington, DC], [Springfield, Va
.

Written in English

- Scattering (Physics),
- Modal analysis.

**Edition Notes**

Statement | Kenneth J. Baumeister and Kevin L. Kreider. |

Series | NASA technical memorandum -- 105722. |

Contributions | Kreider, Kevin L., United States. National Aeronautics and Space Administration. |

The Physical Object | |
---|---|

Format | Microform |

Pagination | 1 v. |

ID Numbers | |

Open Library | OL15365417M |

Abstract. This chapter reviews the development and applications of the multi–domain boundary element method in acoustics. Early development of the method originated from the need for solving problems involving two or more acoustic media, as well as radiation and scattering from thin by: 5. Jimin He, Zhi-Fang Fu, in Modal Analysis, Identification of modal parameters. The modal parameters can be identified from the coefficient matrices [A r].The method to do so is to formulate an eigenvalue problem using the coefficient matrices [A r].The solution to this eigenvalue problem will produce natural frequencies, damping ratios and mode shapes.

In order to simulate sound propagation within a real-world scene, a 3D surface representation is needed, usually in the form of a triangle mesh. Another important requirement for sound prop-agation is the need for accurate acoustic material properties for the 3D scene representation. These properties include absorption and scattering coefﬁcients. Abstract. The impedance theory of scattering (which was proposed by the author—see Acoust. Phys. 52, No. 5 ()) is used as the basis for studying the extremum properties of the absorption and scattering sound powers of arbitrary elastic bodies in an arbitrary acoustic nce-type conditions are obtained for the surfaces of a best absorber, a perfect scatterer, and a so-called Cited by:

1. ISO , Acoustics-Determination of sound absorption coefficient and impedance in impedance tubes - Part 2: Transfer-function method 2. ASTM E, Standard Test Method for Impedance and Absorption of Acoustical Material Using a Tube, Two Microphones and a Digital Frequency Analysis System Dept. of Mech. Engineering 6File Size: 2MB. A material's sound absorbing properties are expressed by the sound absorption coefficient, α, (alpha), as a function of the frequency.α ranges from 0 (total reflection) to (total absorption).. The sound absorption coefficient is normally measured by the room measurements are done in a large room with a diffuse sound field, i.e. the sound has evenly distributed angles of.

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The modal element method for acoustic scattering from 2-D body is presented. The body may be acoustically soft (absorbing) or hard (reflecting). The infinite computational region is divided into two subdomains - the bounded finite element domain, which is characterized by complicated geometry and/or variable material properties, and the surrounding unbounded homogeneous by: 4.

The modal element method for acoustic scattering from a two-dimensional body is presented. The body may be acoustically soft (absorbing) or hard (reflecting). The infinite computational region is divided into two subdomains—the bounded finite element domain, which is characterized by complicated geometry and/or variable material properties, and the surrounding unbounded Cited by: 2.

Get this from a library. Modal element method for scattering of sound by absorbing bodies. [Kenneth J Baumeister; Kevin L Kreider; United States.

National Aeronautics and Space Administration.]. The modal element method for acoustic scattering from 2-D body is presented. The body may be acoustically soft (absorbing) or hard (reflecting). The infinite computational region is divided into two subdomains - the bounded finite element domain, which is characterized by complicated geometry and/or variable material properties, and the surrounding unbounded homogeneous domain.

The modal element method for acoustic scattering from a 2-D body is presented. The body may be acoustically soft (absorbing) or hard (reflecting). The infinite computational region is divided into two subdomains - the bounded finite element domain, which is characterized by complicated geometry and/or variable material properties, and the surrounding unbounded homogeneous domain.

The modal element method for acoustic scattering from 2-D body is presented. The body may be acoustically soft (absorbing) or hard (reflecting). The infinite computational region is divided into two subdomains - the bounded finite element domain, which is characterized by complicated geometry and/or variable material properties, and the surrounding unbounded homogeneous : Kenneth J.

Baumeister and Kevin L. Kreider. The modal element method for acoustic scattering from a 2-D body is presented. The body may be acoustically soft (absorbing) or hard (reflecting). The infinite computational region is divided into two subdomains - the bounded finite element domain, which is characterized by complicated geometry and/or variable material properties, and the surrounding unbounded homogeneous : K.

Baumeister and K. Kreider. Modal approach and Padé approximants for the efficient modelling of sound absorbing porous materials in structural-acoustic finite element problems Article September with 11 Reads.

cylinder solution to describe sound scattering by high aspect ratio (•> ) shelled bodies: prolate spheroid, straight finite cylinder, and uniformly bent finite Size: 1MB. Acoustic Applications in Mechanical EngineeringSpeed of sound –wavelength –frequency §Note that we solve the acoustic wave equation to model reflection, scattering, absorption and thus we have to resolve each wave in its spatial pattern §important equation: §air: c≈m/s, f=Hz → λ=m §water: c≈m/s, f=Hz → λ=m.

Modal element method for scattering and absorbing of sound by two-dimensional bodies, J Vib Acous, Baumeister, Kreider. Scattering cross section of sound waves by the modal element method, in Acoustic Radiation and Wave Propagation (ASME Publications), This paper is concerned with the application of the Boundary Integral Equation (BIE) method to acoustic radiation and scattering in a three-dimensional half space.

Problems in this class include the radiation of sound from vibrating machines near reflecting surfaces and the scattering of sound from objects in air or water that are in close Cited by: Structural-acoustic finite element models including three-dimensional (3D) modeling of porous media are generally computationally costly.

While being the most commonly used predictive tool in the context of noise reduction applications, efficient solution strategies are required. In this work, an original modal reduction technique, involving real-valued modes computed from a classical Cited by: The finite element and boundary element methods, are used to determine the scattering coefficients when the geometries of the ducts and scatterers are complicated.

While these wave matching and numerical methods are capable of producing accurate coefficients, they are less useful in directly delivering the physical insight into the peaks and Cited by: 3.

Kevin L Kreider. University of Akron Modal Element Method for Scattering and Absorbing of Sound by Two-Dimensional Bodies. Article. Aug ; Modal element method for scattering of sound by. i The boundary element method for the solution of acoustic problems has been devel-oped over the last three or four decades.

Out of the three problem classes considered, only the interior problem has been found to be straightforward. The development of the BEMs for the exterior problem and the interior modal. The sound field in the half space bounded by a rigid baffle can be described as [5] () cos()cos, 1 (13) 2, 2 ≈ scattering sound pressure:File Size: KB.

generation by pipe ﬂows, and with respect to more advanced th eory on modal expansions and approx-imation methods.

This particular choice is motivated by industrial applications like aircraft engines and gas transport systems. This course is inspired by the book of Dowling and Ffowcs Williams: “Sound and Sources of Sound” [52].

for pTane-wave scattering and for radiation. electromagnetic radiation and scattering fromhighly conducting bodies of revolution. Specific€ Radiation and Scattering of Waves by L. Felsen, Nathan Marcuvitz,available at Book Depository with free delivery worldwide.

Radiation and scattering of water waves by rigid bodies. The modal ring method for electromagnetic scattering from PEC (perfectly electric conducting) symmetrical bodies is presented. The scattering body is represented by a line of finite elements (triangular) on its outer surface.

sound-absorbing structures that can attain near-equality for the causal relation with very high absorption performance; such structures aredenoted “optimal.” Our strategy involves using carefully designed acoustic metamaterials as backing to a thin layer of conventional sound absorbing material, e.g., acoustic Size: KB.modal representation for sound eld reconstruction and beamforming.

A method for obtaining surface modes of arbitrarily shaped rigid microphone arrays based on the boundary element method (BEM) and the singular value decomposition (SVD) is introduced and an Author: Fabio Kaiser.Sound absorption by viscoelastic coatings with periodically distributed cavities The Journal of the Acoustical Society of America( “ Analysis of the scattering of a plane wave by a doubly periodic structure using the finite element method: Cited by: