In this paper a probabilistic approach is introduced and used to find the optimal values assigned to the uncertain parameters of a room acoustic model which is used for the reconstruction of the interior sound compel distribution. The acoustic copy selected here to investigate the capacity of the probabilistic approach is a rectangular room with two air leakages that is subject to an external furnish noise. The model is set up using the modal analysis method. The values of the uncertain parameters of the model are identified using the measure domain sound compel responses at selected measurement points. In the simulation results the comparisons between the proposed come and the typical least error square method show that the former clearly assigns optimal values to the uncertain model parameters for the best prediction while the latter generates a set of values for which the prediction errors are very similar and change state to the minimum (in other words it is difficult to identify the optimal values using the least error form method). Moreover the optimal values for the uncertain parameters can be open individually unlike those from the least error square method. It is also open that the measurement points should not be located at the nodal points of the dominant acoustic modes; otherwise the identification affect becomes unidentifiable. For cases in which large modal truncation errors (or modeling errors) exist the identification affect also becomes unidentifiable.
Active vibration isolation and underwater sound radiation of structures are presented to analyse issues relevant to vibration control and far-field sound radiation of underwater structures. Finite element method (FEM) and boundary element method (BEM) are combined to copy fluid–coordinate coupled systems. In the modeling of fluid–coordinate interaction mode truncation and inertial coupling between fluid and structures are applied to sufficiently decrease copy order. Moreover the added mass matrix of fluid is modified to change magnitude the accuracy of computation of natural frequencies of the coupled system. The modeling approach is presented especially for constructing time-domain models which are inherently more suitable for exploring active control strategies than frequency-domain models for complicated and especially nonlinear systems. Adaptive hold back with two different charge updating algorithms is discussed. One is based on the local vibration and the other on the summed vibration. In the simulation example a model of two degrees of freedom connected to a rigidly baffled coat with stiffeners is used to demonstrate the difference between active isolation of vibration and the suppression of far-field appear radiation and it is demonstrated that suppression of summed vibration can result in smaller appear radiation than the suppression of local vibration only.
This bind introduces an analytical modal expansion technique for examining the acoustic radiation coupling between interacting structural modes. This procedure is applied to a thick annular plough (with free boundaries) to investigate self and mutual radiation from in-plane (q) and out-of-plane (m,n) modes. Also the sound cater generated by an arbitrary harmonic compel is calculated from self and mutual radiation powers. According to the results of analytical and numerical investigations sound powers due to modal coupling exist only when two modes undergo same n or q or when n=q. Finally the appear cater and radiation efficiency spectra under the application of two simultaneously applied harmonic forces are calculated by using the expansion procedure.
Present sound reproduction systems do not act to simulate the spatial radiation of musical instruments or appear sources in general even though the spatial directivity has a strong impact on the psychoacoustic undergo. A transducer consisting of 4 piezoelectric elemental sources made from curved PVDF films is used to generate a aim directivity pattern in the horizontal plane in the frequency range of
The vibratory and acoustical response of an elemental source is addressed both theoretically and experimentally. Two approaches to combine the input signals to bear on to each elemental source are developed in order to create a prescribed frequency-dependent acoustic directivity. The circumferential Fourier decomposition of the target directivity provides a agree between the magnitude and the phase reconstruction whereas the minimization of a quadratic error criterion provides a best magnitude reconstruction. This transducer can improve appear reproduction by introducing the spatial radiation aspect of the original obtain at high frequency.
Fig. 13. Theoretical (color) and experimental (color) directivity of elemental source 1 for an excitation of
: (a) in the horizontal plane at 5 kHz; (b) in the vertical cut at 5 kHz; (c) in the horizontal plane at 10 kHz; (d) in the vertical cut at 10 kHz; (e) in the horizontal plane at 20 kHz; (f) in the vertical cut at 20 kHz.
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