Academic literature on the topic 'Noise vibro-acoustic cavities'

An imperfect sealing system would be the main path of the noise propagating into the interior compartment of a high-speed vehicle. The study on the sound insulation modeling of automotive door sealing systems, which involve complicated threedimensional sealing structures and gap cavities, has attracted more and more attention. This study employs hybrid finite element–statistical energy analysis (FE-SEA) models to predict the sound transmission loss of three simplified sealing specimens and an actual automotive door sealing system. For the actual sealing system under compression, a three-dimensional FEmodel is built to simulate the nonlinear compression, which can acquire the compressed geometries and pre-stress modal results of the seals for further prediction of the sound transmission loss. The hybrid FE-SEA method is firstly verified by the experimental result of a double plate vibro-acoustic system and another numerical method. Several factors concerning the modeling, including the boundary conditions, the equivalent elastic modulus for the hyper-elastic rubber, the specimen length, and the structural grid size, are considered to study their impacts on the sound transmission loss. The effects of using shell elements and using solid elements to model the sealing rubber layers are also compared. The results of this study can provide guides regarding the trade-off between the modeling efficiency and accuracy, so that it has significance for engineering modeling, as well as the design and optimization of automotive door sealing systems.

PurposeThe purpose of the study is to obtain and analyze vibro-acoustic characteristics.Design/methodology/approachA unified analysis model for the rotary composite laminated plate and conical–cylindrical double cavities coupled system is established. The related parameters of the unified model are determined by isoparametric transformation. The modified Fourier series are applied to construct the admissible displacement function and the sound pressure tolerance function of the coupled systems. The energy functional of the structure domain and acoustic field domain is established, respectively, and the structure–acoustic coupling potential energy is introduced to obtain the energy functional. Rayleigh–Ritz method was used to solve the energy functional.FindingsThe displacement and sound pressure response of the coupled systems are acquired by introducing the internal point sound source excitation, and the influence of relevant parameters of the coupled systems is researched. Through research, it is found that the impedance wall can reduce the amplitude of the sound pressure response and suppress the resonance of the coupled systems. Besides, the composite laminated plate has a good noise reduction effect.Originality/valueThis study can provide the theoretical guidance for vibration and noise reduction.

This paper explores use of the Kalman filter to estimate modal states in Modal Filtered-X LMS algorithm. Modal Filtered-x LMS (M FxLMS) algorithm is an adaptive algorithm, recently proposed by the authors, to minimize global acoustic potential energy of a vibro-acoustic cavity for reducing global level of noise in the cavity. For a weakly coupled vibro-acoustic cavity, global acoustic potential energy can be expressed as sum of squares of modal amplitudes of rigid walled acoustic modes of the cavity. Therefore, the algorithm was formulated to minimize sum of squares of modal amplitudes of the rigid walled acoustic modes. The M FxLMS algorithm turned out to be modal counterpart of the conventional FxLMS algorithm. In the conventional FxLMS algorithm, sum of squares of pressures at the location of microphones is minimized and hence, values of acoustic pressure at the location of error microphones and physical secondary path impulse responses are used. A physical secondary path impulse response represents the variation of acoustic pressure at location of error microphone when secondary source is driven by an impulse function. In the M FxLMS algorithm, sum of squares of modal amplitudes of some chosen acoustic modes is minimized and hence, values of modal amplitudes of the chosen acoustic modes and modal secondary path impulse responses are used. A modal secondary path impulse response represents the variation of modal amplitude of a particular acoustic mode when secondary source is driven by an impulse function. In the earlier study, modal amplitude of the acoustic modes are obtained using information of acoustic pressure at some discrete locations inside the cavity and information of the chosen acoustic mode shapes at those locations. In that approach, number of the acoustic pressure sensors must be adequately more than number of the acoustic modes contributing in desired frequency range. In a view of reducing number of the acoustic pressure sensors, this paper explores use of Kalman filter to estimate modal amplitudes of the acoustic modes. A modal model of the vibro-acoustic cavity is used in the formulation of Kalman filter for estimation of modal amplitudes of acoustic modes. A numerical study is carried out on the same irregular vibro-acoustic cavity which was used for the earlier study. An acoustic disturbance acting inside the cavity and a structural disturbance acting on the flexible surface of the cavity are considered. An acoustic control source is used as a secondary source. The study is carried out for three frequencies: a cavity controlled resonance, a panel controlled resonance and an off-resonance frequency. It is found that with the use of Kalman filter; only 6 microphones are required as against the 18 microphones required in the previous approach for the accurate estimation and then, control of modal amplitudes of first 12 acoustic modes.

In this paper, an analog velocity feedback controller is considered for active vibration suppression of a thin plate for attenuation of sound levels in the frequency range of 0–100 Hz. The active control methods can be applied to interior cavity noise reduction, as encountered for instance in automotive applications. For that purpose, a simplified experimental vibro-acoustic cabin model was built in our laboratory and developed methodologies are demonstrated on the set-up. The set-up includes a rectangular box (1 × 1 × 2 m) which is separated with a flexible thin plate (1 × 1 × 0.001 m) to obtain two enclosed cavities: the passenger compartment (PC) and the engine compartment (EC). The vibration control is applied only on the flexible plate since the walls enclosing the cavities are made of more rigid material (wood filled concrete). By employing piezoelectric patch as actuator and laser doppler vibrometer as vibration sensor, an analog proportional velocity feedback controller is designed and built experimentally for suppressing the low-frequency modes of the flexible plate. In order to attenuate only lower-frequency structural modes of the thin panel, pre-filters are also included in analog circuit. The vibration of thin plate and sound in the passenger compartment is measured for controller-inactive and active cases while disturbing the thin plate via shaker. By measuring vibration and sound response, closed and open loop experimental frequency responses are obtained and presented. The aim of this experimental study is to investigate performance of active vibration control applications on acoustic attenuation as the first step towards robust structural acoustic control.