In the article, the equation of the equivalent movement of the oscillator with viscous friction is provided. The statistical specifications and the spectral approach for the density of intensity of the established vibrations are provided. Non-stationary vibrations in the closed form are investigated. The statistical characteristic for intensity of vibrations is obtained.
The work presents a method of investigation of vibration processes of random mechanical vibrations in the equipment and apparatus. The vibratory system of a sufficiently small (as compared to vibrations of a long wave) size is described; the models with the limited number of degrees of freedom are applied. The statistical theory for discussing of vibrations at constructional damping is applied.
With the purpose of clarifying the impact of a model of a longitudinal plate rib on the
excitation of vibrations of a cylindrical shell and sound radiation, research of this model was
performed. The article shows that the longitudinal plate enforced inside the cylinder may be an
efficient mean for the reduction of vibrations and sound radiated from the cylindrical shell at
separate shell resonance frequencies.
At present, after the restoration of independence, intensive construction of modern
buildings for different purposes is being carried out within Lithuania. New effective materials and
forms are being applied to these constructions. Proper usage of these materials improves
vibroacoustic properties of buildings.
The article deals with the vibroacoustic properties of applied building constructions depending on
their forms and strengthening. Means to increase sound and vibration isolation without changing
vibroacoustic properties of used materials have been determined. Examples of practical application
of vibroacoustic properties of materials are given. The effectiveness of these materials has been
determined. Theoretical results of the effectiveness of vibroacoustic properties of building materials
coincide if the application of vibroacoustic properties in technologies of construction work is
proper.
The efficiency of creating and designing noise reduction measures greatly depends on physical, chemical, mechanical and other properties of the selected materials. Some of them and sometimes all of those have a big impact on the general sound insulation of designed measures that also include absorption values predetermining their efficiency.As has been known for a long time, the formed heavy partitions and elements acquire increased sound insulation according to the law of mass, i.e. the heavier is the weight per m2 of the surface (kg/km2), the higher is the sound of insulation.To increase the efficiency of noise reduction in barriers, it is necessary to search for some other properties of the material like design, quality, etc.The article describes how calculations and empirical manipulations facilitate finding an optimal complex construction effectively reducing noise.
The present paper deals with methods aimed at developing calculation models of sound
insulation of various cylindrical shells, making it possible to estimate the shell-radiated noise levels.
The proposed methodology is based on the mathematical analysis of the cylindrical shell as an
element that is subordinated to the equation of dynamic theory of elasticity of thin-walled
constructions of variable rigidity. The work provides the corresponding controls of dynamic theory
of elasticity in partial derivatives with variable coefficients. Theoretical research and calculations
carried out show that sound insulation under analysis at low frequencies is quite high. A slight
reduction of sound insulation at high frequencies conditioned by wave processes is also considered.
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