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Principles of Noise Control
Published in Junbo Jia, Jeom Kee Paik, Engineering Dynamics and Vibrations, 2018
In structural acoustics the primary noise source is the motion of plates and shells that have sufficient surface area and velocity to create significant sound fields. The analysis of the radiation from such panels can be quite complex (Lamancusa Eschenauer, 1994; Cremer and Heckl, Translated by Ungar, 1988; Ver, 2006; and Bies and Hansen, 2009). This chapter will not attempt to provide a thorough examination of sound radiation from structural elements. Instead a few examples will be used to illustrate the basic principles.
Study on compound vibration isolation technology in ship foundation structure
Published in J. Parunov, C. Guedes Soares, Trends in the Analysis and Design of Marine Structures, 2019
S. Wang, J.X. Yue, X.B. Li, W.J. Tu, L. Chen
In the structure of a ship, the vibration energy is transmitted by structural sound. To a certain extent, the damping material can suppress the transmission of structural acoustic energy due to its ability to absorb energy. However, the damping effect on the vibration is often proportional to the vibration speed, and it is basically ineffective in areas where the vibration speed is not obvious.
Exact boundary controllability of the structural acoustic model with variable coefficients
Published in Applicable Analysis, 2023
In the motivating structural acoustics application, the region Ω represents an acoustic cavity. The acoustic medium is described by the variable-coefficient wave equation, while the quantity describes the acoustic back pressure. Let be a flat subset of Γ which represents a flexible wall of the cavity. and are sometimes referred to as the ‘active’ wall of the cavity and ‘hard’ wall, respectively. It is a canonical example of control-structural acoustic interaction, which models the interaction between sound waves in an acoustic cavity and its walls. Mathematically speaking, a structural acoustic model is a class of a system of coupled partial differential equations, which comprises a acoustic wave equation in the interior domain, a structural plate (beam, wave and shell) equation on the boundary portion, with the coupling being accomplished across a boundary interface.
Scattering characteristics through multiple regions of the wave-bearing trifurcated waveguide
Published in Waves in Random and Complex Media, 2022
Hani Alahmadi, Haleem Afsar, Rab Nawaz, Mohammed Omar Alkinidri
Noise control is an emerging science in the recent history of the developing world. The main causes of noise are machinery equipments that are used in heavily built-up areas, such as vehicles and aero-engines, heating and cooling systems, exhausting systems, etc. This primarily motivates the structural engineers to always prefer to design structures that will significantly reduce unwanted noise. Many exhausting systems and modified silencers are being used at a large industrial level to reduce noise. The structural acoustics have provided an interesting and wide range of challenging problems for scientists and engineers. The consideration of appropriate duct geometries is a viable way in reducing and controlling unwanted noise. A fact behind this topic is that it has become a part of current interest to investigate the propagation of an incident mode through a trifurcated structure with various boundary conditions like soft, hard, impedance and flexible.
Stabilization and spectral properties of acoustic flow in a cylindrical shell
Published in Applicable Analysis, 2022
Active control methodology of noise due to structural vibrations has been motivated by the development of a new class of turboprop and turbofan engines. These noisy engines produce vibrations in the fuselage, which lead to the unacceptably high cabin noise level. Control techniques for structural acoustics problem of this type have been studied from a variety of perspectives. The problem of acoustic structural coupling in a cavity enclosed by a thin cylindrical shell has been considered by Banks and Smith [1]. The discussion includes the loads and material contributions resulting from piezoceramic patches bonded to the shell. The motivation of this problem was to reduce the noise, which is generated by the vibration of the cylindrical shell.