Porous sound-absorbing materials (review)

Shashkeev, K. A.; Shuldeshov, E.M.; Popkov, O. V.; Kraev, I.D.; Yurkov, G. Yu.

doi:10.18577/2307-6046-2016-0-6-6-6

Cited by 3 publications

(4 citation statements)

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“…Less role is attached to the absorption of sound energy caused by the material viscosity though it is noted that at low frequencies it makes major contribution to the absorption. Also it is noted that the efficiency of sound absorption of all mentioned materials depends on the thickness of the sound absorbing layer and the frequency of acoustic affect with obvious decrease in the low frequency area …”

Section: Introductionmentioning

confidence: 99%

“…The most multi‐purpose and effective materials are porous sound absorbing ones which can be divided into three basic groups: honeycomb, fibrous and granular …”

Section: Introductionmentioning

confidence: 99%

“…All of them are solid substances with large number of pores and canals of various structures: open, close, blind, end‐to‐end, and internal. In terms of acoustics, in all above‐mentioned types of materials the sound absorbing properties depend, first of all, on the type of pores on the surface of such material and the nature of internal porosity . The efficiency of acoustical absorption is made dependent upon the size of pores, content of through porosity, fiber layout, form of grain, etc, assuming that the loss of sound wave takes place mainly due to friction on the internal walls of open pores and canals.…”

Section: Introductionmentioning

confidence: 99%

“…It is remarkable fact that in many cases the perforation of porous material leads to improvement of sound absorbing properties …”

Section: Introductionmentioning

confidence: 99%

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Free and forced bending vibrations of a thin plate in a perfect compressible fluid with energy dissipation taken into account

et al. 2020

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A refined statement of stationary dynamic acoustoelasticity problems of thin isotropic plates surrounded from both sides by acoustic media assumed to be perfect compressible fluids has been studed. The problem statement takes into account the energy dissipation in the material of the plate and fluid on the basis of the Kelvin-Voigt hysteresis model. The refinement of the fluid behavior is based on the assumption that the pressure increment is proportional not only to volumetric strain, but also to the rate of its volumetric strain. This assumption allows us to obtain the generalized Helmholtz wave equation by introducing Skudrzyk's complex sound velocity into consideration to take account of the energy dissipation. The motion equations of the plate are based on the classical Kirchhoff-Love model and are obtained in two versions. In the first version unsimplified three-dimensional wave equations are used to determine the aerohydrodynamic load acting on a plate. The second version is based on simplifying the equations of fluid motion by the introduction of the well-known hypothesis of plane reflection and emission of sound waves. On the basis of the derived equations, exact analytical solutions of two types of problems are obtained. The first type is related to the problem of free vibrations of a rectangular plate hinged around the contour when complex eigenfrequencies were defined. The second type is related to the problem of forced vibrations of the plate under the action of a flat mono-harmonic incident sound wave when sound transmission loss, the stress-strain state parameters of the plate as well as the laws of change in sound pressure in a fluid were determined. It is shown that correct and more meaningful solutions of acoustoelasticity problems of the considered class are possible only in case of describing the behavior of a fluid with unsimplified three-dimensional wave equations with consideration of the energy dissipation. K E Y W O R D Sacoustoelasticity problems, complex oscillation frequency, complex sound velocity, energy dissipation, free and forced vibrations, generalized Helmholtz equation, Kelvin-Voigt model, perfect compressible fluid, plate, sound pressure, sound transmission loss

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Section: Introductionmentioning

confidence: 99%

“…The most multi‐purpose and effective materials are porous sound absorbing ones which can be divided into three basic groups: honeycomb, fibrous and granular …”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…It is remarkable fact that in many cases the perforation of porous material leads to improvement of sound absorbing properties …”

Section: Introductionmentioning

confidence: 99%

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Free and forced bending vibrations of a thin plate in a perfect compressible fluid with energy dissipation taken into account

et al. 2020

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Dielectric Characteristics of Structural Organoplastics

et al. 2022

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Using Persistence to Generate Incentives in a Dynamic Moral Hazard Problem

Bohren

2018

SSRN Journal

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This paper studies how persistence can be used to create incentives in a continuous-time stochastic game in which a long-run player interacts with a sequence of short-run players. Observation of the long-run player's actions are distorted by a Brownian motion and the actions of both players impact future payoffs through a state variable. For example, a firm or worker provides customers with a product, and the quality of this product depends on both current and past investment choices by the firm. I derive general conditions under which a Markov equilibrium emerges as the unique perfect public equilibrium, and characterize the equilibrium payoff and actions in this equilibrium, for any discount rate. I develop an application of persistent product quality to illustrate how persistence creates effective intertemporal incentives in a setting where traditional channels fail, and explore how the structure of persistence impacts equilibrium behavior. This demonstrates the power of the continuous-time setting to deliver sharp insights and a tractable equilibrium characterization for a rich class of dynamic games.

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Porous sound-absorbing materials (review)

Cited by 3 publications

References 0 publications

Free and forced bending vibrations of a thin plate in a perfect compressible fluid with energy dissipation taken into account

Free and forced bending vibrations of a thin plate in a perfect compressible fluid with energy dissipation taken into account

Dielectric Characteristics of Structural Organoplastics

Using Persistence to Generate Incentives in a Dynamic Moral Hazard Problem

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