Electrical apparatus such as transformers radiate noise which is almost completely harmonic in its frequency characteristic and stationary in the time domain. Those two parameters enable us to look at the transformer noise through its vibration pattern on the structure. Estimat ion of the radiated noise characteristic can be performed processing vi...
The possibility of control of dynamical condition of the shakers that are designed for vibration treatment of parts interacting with granular media is discussed. The aim of this article is to develop the methodological basis of technology of creation of mathematical models of shake tables and the development of principles of formation of vibrationa...
A compact multi-layered structure is proposed based on the coiled-up space concept for power transformer noise absorption at 100 and 200 Hz. Current methods of constructing multi-band absorbers are impractical for power transformer noise control due to the high coupling effect deteriorating their performance. To overcome this shortcoming, the proposed structure is composed of multiple connected layers creating two separate coiled ducts with adjustable dimensions to minimise the coupling effect. In the modelling stage, the geometrical features are optimised using the genetic algorithm to maximise the absorption coefficient and minimise the thickness. The proposed dual-tone absorber has a thickness of 43.5 mm which is significantly thinner than the existing conventional absorbers. The measurement results on a 3D-printed structure demonstrate the feasibility of the design.
This paper presents a new method to compute the sound radiation emanating from a thin plate structure due to complex inputs that include normal force and in-plane bending moments. A set of new formulas for the sound radiation of baffled and unbaffled plates are derived by substituting the moment components of the plates with the equivalent couples using finite difference analysis. This approach allows to calculate sound power purely by the input location and amplitude of each component. Thus, it enables faster, more accurate calculations than the existing methods such as the average radiation efficiency analysis and the radiation mode analysis. Based on these calculations, the vibroacoustic characteristics of a simply supported rectangular plate are analyzed. The computational results are in good agreement with the finite element analysis results. It is suggested to keep the grid spacing less than 2.5% of the shortest dimension of the target structure to accurately calculate the moment mobility. Accurate sound power can also be obtained by downsampling the grid to satisfy ka<0.2 within the frequency band of interest. Furthermore, a sound reduction method is proposed by analyzing each structural mode's contribution to the sound radiation. Using the proposed methodology, sound power at a specific frequency or multi-frequency range can be reduced or amplified by changing the location and angle of the complex inputs.