Finite element simulations of passive damped system applied to the simply-supported excited squared steel plate, is the aim of the analysis. The full mechanical, piezoelectric, electric and acoustic field coupling is analysed in Ansys Package. As the result the acoustic pressure radiated by plate is analysed. The results show possibility of application of the discussed method to reduction of the sound pressure level in realistic engineering structures.

The study is a next part of earlier works by the authors, and explores how does the sequence of activated actuators and the level of applied voltage affect the radiated acoustic energy. The analysis uses the finite element method for structural vibrations and combination of the finite element and the intensity hybrid method to assess the level of sound radiation. The vibrating element is a steel plate with glued on actuators, supported on one edge and excited by a harmonically variable, concentrated load with a constant amplitude value.

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The paper presents simulations and research results of testing of the aluminium plate with active vibration control. The aim of this paper is to analyze and compare two ways of excitation of the test plate, various influence on its vibrations and active damping control. Vibration control of the smart structure is realized through four piezoceramic PZT actuators and one PZT sensor bonded to the plate. Simulations and numerical computations of the structure are performed in ANSYS environment. Measurements are executed on specialized sound insulation suite for small elements in reverberation chamber. At the beginning white noise sound source is used in purpose to measure basic vibration modes. After numerical computations and measurements three particular frequencies has been chosen and for them active damping is applied. There are two ways of exciting the test plate; first method is sound wave, second is mechanical vibrations via one of piezoceramics. The test results indicate that PZTs can decrease vibrations by approximately 15 dB for a pure sound input with acoustic excitation method, for mechanical excitation method 18 dB for a sinus vibration signal is achieved.

The paper presents results of determination of sound wave direction based on signals from rst-order ambisonic microphone. The experiment consisted in recording the test signals with the SoundField microphone positioned in the axis of the turntable in the anechoic chamber. The spherical coordinates of the sound intensity vector were calculated with use of three dierent conceptual and numerical approaches and were compared to actual values resulting from the geometry of the system. Accuracy of the localization of the sound source depending on the frequencies and the method for determination of the spherical coordinates as well as on the time constant and the parameters of the signal recording was presented. The obtained results show the eectiveness of the calculation methods used for localization of the sound source.

Using statistical energy analysis method to gain knowledge of coupling loss factors (CLFs) of structural elements of complex mechanical systems is fundamental, therefore the evaluation of CLFs for different constructional connections of thin rectangular plates merits studying. CLFs for different constructional perpendicular connections of thin rectangular plates were investigated. Three types of couplings were studied: line junction, stiff bridges, and point connections. Investigations were realized with method of energy stored at anechoic chamber. Experimental test included two kinds of connections of tested perpendicular plates: welded line junctions and point junctions. Several combinations of thickness ratio on CLFs values were tested for welded plates. Also, the distribution points were studied to show the impact on CLFs. There is evidence of decreasing of CLFs for larger ratios of thickness especially for higher frequency bands. Acoustic power flow across riveted junctions shows up to 20 dB lower transmission than similar spot welded junctions. In the examined screwed junctions demonstrate lower than average CLFs activity than riveted and higher than point welded.

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This paper presents numerical analysis of eciency of dierent shapes and material composition of piezoelectric actuators used for vibration reduction. Four numerical models representing a plate clamped on all sides with two attached piezoelectric elements were created. For each model, one element had the same shape and composition and was used for plate excitation, and the other one, used for vibration reduction, had dierent shape and possibly material composition and could be of square or circular shape with either homogeneous or two-part material composition. Two modes were taken into account: the rst mode and the fth mode. Analysis of results was performed with ANSYS software.