Stiffener shape design to minimize interior noise

Engelstad, Stephen P.; Cunefare, Kenneth A.; Powell, E. A.; Biesel, Van

doi:10.2514/6.1997-1620

Cited by 3 publications

(3 citation statements)

References 5 publications

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“…For the acoustic characteristics to be influenced, we can name the sound power, sound pressure level, directivity patterns or other measures. Approaches to formulate an objective function to judge the desired properties can be categorized into three different groups, the first one being the sound pressure level at one or more specified points, primarily utilized for closed domains [28,64,86]. For general-purpose noise control in open domains, the emitted sound power accounted for the objective function in a number of papers [10,16,50,57,58].…”

Section: Acoustic and Structural-acoustic Optimizationmentioning

confidence: 99%

A Unified Approach to Finite and Boundary Element Discretization in Linear Time–Harmonic Acoustics

Marburg

Computational Acoustics of Noise Propagation in Fluids - Finite and Boundary Element Methods

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This chapter introduces the reader too important physical and mathematical concepts in acoustics. It presents an approach to finite and boundary element techniques for linear time-harmonic acoustics starting from the fundamental axioms of continuum mechanics. Based on these axioms, the wave equation is derived. Using a time-harmonic approximation, the boundary value problem of linear time-harmonic acoustics is formulated in the classic and in the weak form. Subsequently, two types of the weak form are used as the basis for discretization resulting in a Galerkin finite element formulation, in a collocation boundary element formulation and in a Galerkin boundary element formulation. Then, different representations of sources and incident wave-fields in finite and boundary element methods are discussed. In the final part of this chapter, the authors categorize the subsequent twenty chapters of this book. The chapter will be completed by an outlook and some open problems in the development of finite and boundary element techniques from the authors' points of view.

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Section: Acoustic and Structural-acoustic Optimizationmentioning

confidence: 99%

A Unified Approach to Finite and Boundary Element Discretization in Linear Time–Harmonic Acoustics

Marburg

Computational Acoustics of Noise Propagation in Fluids - Finite and Boundary Element Methods

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“…One idea is to optimize the shape or the material properties of the fuselage so that characteristic frequencies of the interior space do not match the tones in the propeller noise spectrum. 22 Another idea is to optimize the sound produced by an array of loudspeakers so that the noise due to the propeller is canceled by the "anti-noise" produced by the speakers. 23 A third idea is to optimize the inputs to inertial actuators attached to the airframe so that the vibration of the fuselage is reduced.…”

Section: Noise Controlmentioning

confidence: 99%

Low-frequency interior noise in prop-driven aircrafts: Sources and control methodologies

Ommi

Azimi

2017

Noise & Vibration Worldwide

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Nowadays, noise has turned into one of the most important among the environmental factors on which industry sets down a big part of its efforts and concerns. The recognition of noise as a serious health hazard is a development of modern times. Too much noise obviously impairs our physical and mental existence and therefore it is reasonable to pursue Technology Assessment concerning noisy technologies. The conflicts of interest associated with noise that arise from the operation of airports are well known. Propeller noise is most dominant at low frequencies (below 500 Hz) where traditional passive treatments have only little effect. The many factors contributing to the sound field inside propeller aircraft have led to extensive research directed toward identifying and improving techniques for interior noise reduction.

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“…An interesting study of optimally distributed damping material on a circular plate has been provided by Wodtke and Lamancusa. 56 More realistic applications were discussed by Cunefare and Engelstad et al [10][11][12] Their example, a cylinder clamped at both ends and acoustically excited by a monopole source from outside appears roughly similar to an aircraft fuselage. However, investigation of shell thickness optimization as well as optimal positioning of stringers and frames for stiffening look reasonable to conclude for more complex aircraft constructions.…”

Section: Introductionmentioning

confidence: 97%

Investigation and Optimization of a Spare Wheel Well to Reduce Vehicle Interior Noise

Marburg

Hardtke

2003

J. Comp. Acous.

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Optimization of structures with the intention to reduce noise emission has become an efficient tool during the past decade. Various approaches and applications have been published and will be briefly reviewed in this paper. Then, the structural component model of a spare wheel well and the fluid model of a sedan cabin are described. The noise transfer function is defined as the sound pressure level in vicinity of the driver's ear due to a harmonic force excitation at engine supports. The frequency range of 0-100 Hz is considered. In a first investigation, it is tested whether stiffening of the entire structural component really decreases the noise transfer function. It can be seen that this stiffening mainly affects noise emission in the upper frequency range. In a contribution analysis, i.e. analysis of the surface contribution to the noise at the driver's ear, the original model and the stiffened model are compared. This contribution analysis includes frequency ranges by summation of contribution and/or contribution levels. Modification of the structure by design variables consists of modification of the shell geometry, i.e. curvature. Two regions are selected at the bottom of the wheel well. Optimization of 30 design variables leads to a gain of 1.15 dB in the objective function being the root mean square value of the sound pressure level at the driver's ear. Finally, we discuss the results. In most papers on structural acoustic optimization, higher decreases have been reported. An explanation is provided, why this was not possible for the structure that has been investigated here. The new shape, however, seems to be a reasonable choice.

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Stiffener shape design to minimize interior noise

Cited by 3 publications

References 5 publications

A Unified Approach to Finite and Boundary Element Discretization in Linear Time–Harmonic Acoustics

A Unified Approach to Finite and Boundary Element Discretization in Linear Time–Harmonic Acoustics

Low-frequency interior noise in prop-driven aircrafts: Sources and control methodologies

Investigation and Optimization of a Spare Wheel Well to Reduce Vehicle Interior Noise

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