Control Of Sound Radiation Research Articles

A study on active structural acoustic control using force radiation modes

Active Structural Acoustic Control (ASAC) is an effective method for sound radiation control. To solve the coupling effect or inconvenience problems existed in the application of conventional methods, by utilizing the characteristic of intuitive representation of radiated sound power through force radiation modes, the control forces are designed to make the total excitation force vector orthogonal to each dominant force radiation mode. Therefore, an ASAC method by utilizing force radiation modes is proposed, and detailed theoretical research and numerical calculation analysis are carried out. The research results indicate that the control force requirement can be intuitively obtained through the force radiation modes, and decoupled control of radiated sound power corresponding to each force radiation mode is achieved by the proposed method. Thus, the control strategy and system construction can be greatly simplified, and structural acoustic radiation can be effectively controlled.

Applying Michelson-interferometer based optical fiber sensors for active control of road noise in a car

Active noise control (ANC) technology is a promising solution for reducing road noise in cars, where the quality of reference signals is critical for improving the performance. In this paper, an optical fiber sensor based on Michelson interferometer is proposed to obtain the vibration reference signal for active control of road noise in a car. First, the principle of this optical fiber sensor is introduced, then the feasibility of using optical fiber sensor for active control of sound radiation from a panel of an enclosure is verified, where the spectrum, coherence and impulse response of the optical fiber sensor are reported and compared with that of an accelerometer. Finally, the optical fiber sensor is applied in a car for active control of road noise and the simulation results based on the measured data are presented. The research demonstrates the potential of using the proposed optical fiber sensor for active control of road noise in a car by discussing its advantages and weakness.

Refracto-vibrometry for active control of sound radiation through an opening

In this study, refracto-vibrometry is proposed for active control of sound radiation through an opening. First, refracto-vibrometry is used to reconstruct sound field in an opening, and a quantitative comparison of sound fields is made with those obtained from a microphone array at 224 locations. Then, the reconstructed sound field by refracto-vibrometry is used for active noise control. Experimental results indicate that using refracto-vibrometry can obtain about 12.9 dB noise reduction at 500 Hz with no increase in noise observed at higher frequencies above 2 kHz. By offering a significantly larger number of error signals without causing obstructions at an opening, refracto-vibrometry outperforms traditional microphone arrays, making it an effective complementary error sensing method for high frequency noise.

Sound radiation control of an unbaffled long enclosure using wavy micro-perforated panel absorbers

The sound radiation control of an unbaffled long enclosure using wavy micro-perforated panel absorbers (WMPPAs) was numerically and experimentally investigated. First, a hybrid model based on the finite element method (FEM) and the Wiener-Hopf (W-H) technique was established to calculate the sound pressure level (SPL) radiated from an unbaffled long enclosure lined with MPPAs. Then, the hybrid model was validated, and the sound suppression performance of a single WMPPA was evaluated. The results demonstrate that the WMPPA exhibits better sound absorption properties than the flat and corrugated micro-perforated panel absorber (FMPPA and CMPPA), especially in the middle- to high-frequency range. To further enhance the sound attenuation performance, an array of WMPPAs was subsequently proposed to absorb higher-order acoustic modes inside the long enclosure so that broadband-radiated noise could be suppressed. The comparison results demonstrate that the WMPPAs can reduce the radiated SPL within a wide frequency range which is favourable for the suppression of environmental noise. In addition, the WMPPA array shifts the sound reduction curve towards a low-frequency range by approximately 500 Hz compared with that of a single WMPPA, which is promising for the reduction of broadband noise. After that, a mechanistic study was conducted to explain the sound reduction performance of WMPPAs from the perspective of modal contributions. In addition, the diffraction effect of sound waves at the sharp edge of a long enclosure was illustrated. Besides, the contribution of the wavy structure's scattering effect to the sound reduction performance of WMPPAs was analysed. Finally, the sound absorption abilities of the WMPPAs were examined using a quasi-two-dimensional (quasi-2D) experiment. The results show that the WMPPAs exhibit good sound reduction performance in the middle- to high-frequency range, which verifies the feasibility of applying WMPPAs to suppress the broadband noise radiated from long enclosures.

Hybrid Fuzzy PID Sound Radiation Control of a Functionally Graded Porous GPL-Reinforced Plate with Piezoelectric Sensor and Actuator Layers

This paper is the first attempt to investigate the sound radiation control of a functionally graded porous graphene platelet-reinforced composite (FGP-GPLRC) plate integrated with piezoelectric face sheets. A spatial state-space formulation based on the linear 3D piezoelasticity theory is utilized to derive a semi-analytic solution for the coupled vibroacoustic response of the simply-supported arbitrarily thick composite plate. A comprehensive parametric study examines the effect of GPLs’ distribution, weight fraction, and porosity parameters of the core layer on the radiated sound power. Then, the best material configuration is selected to be actively controlled. A hybrid Fuzzy Proportional-Integral-Derivative (FPID) controller, which utilizes an FPID controller integrated with a classical PID controller, is employed to mitigate sound radiation from the smart sandwich plate via the volume velocity approach. The gain parameters of the proposed controller are tuned using the Bat optimization algorithm. Finally, the performance of the active control strategy in attenuating radiated sound power is investigated through several numerical simulations. Results show the proposed control scheme's robustness and rapid disturbance rejection performance.

Investigation of the mechanism of noise radiation reduction from an ABH-cavity under interior acoustic excitation considering multistage coupling

The acoustic black hole (ABH) structure exhibits superior vibration and sound radiation control capability compared to its flat counterpart. However, for a coupled plate-cavity system under interior acoustic excitation, the underlying suppression mechanism of noise radiation has not been explored, especially below the critical frequency of the structure. In this paper, the noise suppression mechanism of an ABH-cavity system under interior acoustic excitation is investigated both theoretically and numerically. Based on the theoretical analysis, the noise radiation depends on both the structural modes and the cavity modes, which can be suppressed in two ways. One is to lower the magnitude of structural transfer functions. The other is to change the mapping matrix which maps the structural modal amplitude to the amplitude of radiation modes. For the former, numerical analysis based on FEM demonstrates that a lower structural transfer function is obtained in the ABH-cavity system compared to its flat counterpart because of the damping enhancement characteristic of the ABH structure. Therefore, attenuated flexural vibrations and reduced sound radiation are achieved at corresponding modal frequencies. For the latter, ABH-cavity systems with varying numbers of ABHs are constructed to demonstrate a simple solution of manipulating the mapping matrix to achieve the reduced radiation efficiency of structural panels and the enhanced suppressing effect of noise radiation. The study in this paper indicates a feasible direction for the further optimization analysis of noise radiation suppression of the ABH-cavity system.

A metamaterial plate with magnetorheological elastomers and gradient resonators for tuneable, low-frequency and broadband flexural wave manipulation

Incorporating magnetorheological elastomers and multiple gradient resonators (MRE–MGRs), a novel metamaterial plate is proposed, which entails low-frequency, broadband and tuneable bandgap features. The proposed MRE-MGR design embeds an adaptive magnetic field adjustment mechanism to alter the elastic modulus of the MRE to modulate the local resonance bandgap frequency and bandwidth. A bandgap prediction model of the metamaterial plate is developed using the plane wave expansion (PWE) method. Integrated into the model through equivalent stiffness terms, the magneto-controlled modulus of the MRE can be estimated using the energy method and magnetic dipole theory. The established model allows for revealing the dispersion relation of the proposed metamaterial plate under various magnetic fields. The predicted tuneable bandgaps, vibration transmission loss and flexural wave modulation of the metamaterial plate are validated through comparisons with finite element simulations. Numerical analyses show the benefit of the gradient resonator design, which alongside the effective MRE tuning, entails broadening low frequency bandgaps at 92 Hz (relative band of 79.3% for the exponential gradient) and 72.7 Hz (relative band of 65.9% for the linear gradient). The mechanisms underpinning the observed bandgap widening phenomenon are analysed and attributed to the combined effects arising from the gradient design of the distributed resonators and the effective tuning of the MRE elastic modulus under magnetic field modulation. The proposed metamaterial plate functionally achieves simultaneous magnetron adjustment of the bandgap frequency and its width, thus holding great promise for applications such as flexural wave guiding as well as vibration and sound radiation control in planar structures.

Dominant frequency control of sound radiation from largely deformed thin plates

Dominant frequency control of sound radiation from largely deformed thin plates

Modal Performance Analysis of Compressor for Active Control of Acoustic Radiation

Compressor has a complex internal structure and contains various kinds of motion mechanism. At present, research on compressor’s vibration and sound radiation characteristics is insufficient. In this paper, structure and sound radiation modes of control objects are analysed by mode analysis. Explore the mode distribution law and correspond the structure mode to the sound radiation mode. On this basis, by suppressing the vibration mode, the influence is transmitted to the acoustic domain to realize the active control of sound radiation of the structure as a whole.

Low-frequency enhancement of acoustic black holes via negative stiffness supporting

Acoustic black holes (ABHs) attract increasing attention in the field of vibration suppression, sound radiation control and energy harvesting. Though the ABH effect usually works well in the mid-high frequency range, it cannot be triggered below the cut-on frequency. Thus, enhancing the vibration reduction at low frequencies is an urgent task. Inspired by the impressive low-frequency performance of the negative stiffness, we propose a novel idea that combines an ABH beam with a negative stiffness element (NS-ABH beam). To characterize such a system, a semi-analytical model is developed based on the Gaussian expansion method (GEM) in the framework of the Rayleigh–Ritz method. The modal loss factors (MLFs) and mean square velocity (MSV) are calculated to estimate the damping performance. The results show that the proposed NS-ABH beam can achieve remarkable vibration reduction below the cut-on frequency without sacrificing the ABH effect at higher frequency. The coupling mechanism between negative stiffness and ABH beam and the reduction mechanism behind are studied based on the modal projection method to better understand the observed phenomena. Finally, experiments have been implemented to validate the theoretical model and the NS-ABH performance.

Active feedback control of sound radiation in elastic wave metamaterials immersed in water with fluid–solid coupling

Due to their potential properties unlike traditional materials and structures, elastic wave metamaterials have received significant interests in recent years. With the coupling between the acoustic and vibration, their mechanical characteristics can be tuned by the active feedback control system at low frequency ranges in which the traditional passive control is limited. This work illustrates that the superior performances of the effective mass density and sound pressure level (SPL) of an elastic wave metamaterial can be significantly changed by the active control, in which the periodic array of local resonators and orthogonal stiffeners are included. Significantly, based on the locally resonant mechanism, the negative density occurs over a frequency range. Due to the effects of lattice constant, structural damping and other parameters, the SPL with the function of fluid–solid coupling are illustrated and discussed.

Comparison of smart panels for tonal and broadband vibration and sound transmission active control

ABSTRACT This paper presents a comprehensive overview of the principal features of smart panels equipped with feed-forward and feedback systems for the control of the flexural response and sound transmission due respectively to tonal and to stochastic broadband disturbances. The smart panels are equipped with two types of actuators: first, distributed piezoelectric actuators formed either by small piezoelectric patches or large piezoelectric films bonded on the panels and second, point actuators formed by proof-mass electromagnetic transducers. Also, the panels encompass three types of sensors: first, small capacitive microphone sensors placed in front of the panels; second, distributed piezoelectric sensors formed by large piezoelectric films bonded on the panels and third point sensors formed by miniaturized accelerometers. The proposed systems implement both single-channel and multi-channel feed-forward and feedback control architectures. The study shows that, the vibration and sound radiation control performance of both feed-forward and feedback systems critically depends on the sensor-actuator configurations.

Optimization of Dynamic Vibration Absorbers for Suppressing Sound Radiation of Plate Structures

Abstract Dynamic vibration absorber (DVA) is a practical tool used for sound and vibration suppression in the specific frequency band. The parameters of DVAs should be optimally tuned to obtain the best sound and vibration suppression application effects. When the DVAs are used for structural vibration reduction, DVAs’ two parameters which are the optimal frequency ratio and damping ratio have simple analytical expressions. However, the concise analytical expressions of the DVAs that are used for suppressing the structural sound radiations have not been reported. First, this paper investigates the characteristics of DVAs in suppressing sound radiation from thin plates. Second, the fixed points’ phenomenon of the sound radiations of the plate carrying DVAs is revealed. In addition, the classical fixed points’ theory is extended into the optimization process of the DVAs that are used for sound radiation control of the plate. The analytical expression of the optimal frequency ratio, as well as the damping ratio optimization method of the DVA, is simultaneously proposed. Third, the installation position of DVAs is also presented to obtain a better acoustic radiation effect. Finally, the numerical simulations are performed to verify the availability of the method. It is showed that the best sound radiation control effect could be obtained by adopting the optimization means proposed in this paper.

Sound Radiation of Orthogonal Antisymmetric Composite Laminates Embedded with Pre-Strained SMA Wires in Thermal Environment

The interest of this article lies in the sound radiation of shape memory alloy (SMA) composite laminates. Different from the traditional method of avoiding resonance sound radiation of composite laminates by means of structural parameter design, this paper explores the potential of adjusting the modal peak of the resonant acoustic radiation by using material characteristics of shape memory alloys (SMA), and provides a new idea for avoiding resonance sound radiation of composite laminates. For composite laminates embedded with pre-strained SMA, an innovation of vibration-acoustic modeling of SMA composite laminates considering pre-stain of SMA and thermal expansion force of graphite-epoxy resin is proposed. Based on the classical thin plate theory and Hamilton principle, the structural dynamic governing equation and the frequency equation of the laminates subjected to thermal environment are derived. The vibration sound radiation of composite laminates is calculated with Rayleigh integral. Effects of ambient temperature, pre-strain, SMA volume fraction, substrate ratio, and geometrical parameters on the sound radiation were analyzed. New laws of SMA material and pre-strain characteristics on sound radiation of composite laminates under temperature environment are revealed, which have theoretical and engineering functional significance for vibration and sound radiation control of SMA composite laminates.

An alternative and optimized thickness profile of an acoustic black hole plate

Owing to their unique wave retarding features, Acoustic Black Hole (ABH) structures with standard power-law thickness profiles have been extensively explored for various structural vibration and sound radiation control applications. In order to achieve even better ABH effects for a given minimum thickness that can be achieved or accepted in practice, this paper reports an alternative ABH thickness profile in a plate through an optimization procedure by using the fast and elitist nondominated sorting genetic algorithm II in conjunction with a 2D semi-analytical Daubechies wavelet model. The new thickness profile features a different geometry from the standard ones in that the position of the imposed minimum thickness is off-set from the ABH indentation center, thus forming a flexible ring-shaped area and creating bi-directional ABH effects, which is conducive to energy focusing and dissipation. Numerical results show that a plate embedded with the optimized ABH indentation exhibits better ABH effects than its standard ABH counterpart, as evidenced by an increase in the total system damping as well as an impairment of other vibration and sound radiation metrics. Mode shape analyses of the optimized ABH plate show that the observed damping increase is mainly attributed to these local (n¯, 1) and (n¯, 2) modes, as a result of the flexible ring-shaped area that is formed inside the optimized ABH indentation. Finally, the optimized ABH plate is shown to entail reductions in both the vibration response of the plate and its sound radiation into a free acoustic medium.

A near-field error sensing strategy for compact multi-channel active sound radiation control in free field.

Noise reduction performance of a compact active sound radiation control system is significantly affected by locations of the error microphones which are required to be installed near the primary source. In this paper, near-field error sensing for multi-channel active radiation control systems in free field is investigated, and it is found that the optimal locations of error sensors for minimizing the sum of squared sound pressure are between the primary source and the secondary sources distributed uniformly on a sphere surface surrounding the primary source. Both simulation and experiment results show that the optimal locations of error microphones are independent of the type of primary source when there are sufficient secondary sources. These optimal locations remain unchanged at low frequencies and move toward secondary sources when the secondary source number increases. Therefore, for active radiation control applications in low frequency range, a compact multi-channel system can be developed by locating error microphones between the primary source and secondary sources.

Active control of sound radiation from rib stiffened plate using the weighted sum of spatial gradients as the cost function

The active structural acoustic control of the rib stiffened plate highly improves the sound insulation performance in the low frequency range. This promotes the engineering relevance of the active control technic since the ribbed plate is a classical structural element widely applied in practical engineering. One of the key problems encountered when implementing such system is error sensing strategy. The traditional sensing strategy, such as sensing the radiation modes using distributed piezoelectric sensors, is difficult to implement due to the block of the ribs in the ribbed plate case. The pseudo-uniform structure quantity proposed recently, i.e., the weighted sum of spatial gradients (WSSG) is highly correlated with the radiated sound power of the radiating plate, which can be easily obtained by only sensing vibrating information of single point and is also less sensitive with the sensor location. Hence, WSSG is adopted in this paper to establish the error sensing strategy for the active structural acoustic control of the ribbed plate. The weights in WSSG directly impact the control performance, and should be chosen appropriately for the plates with different parameters. The parameter-based weights, which can be obtained conveniently according to the ratio of the flexural rigidity to the mass per unit area of the plate, are more preferable in real implementation for broadband frequency control. As for the ribbed plate case, due to the coupling effects of the ribs, the flexural rigidity of the ribbed plate is not uniform and varies for different kinds of rib arrangements. This is another parameter that will also affect the parameter-based weights. This paper compares the regions of the near-optimal weights for different locations of the ribs and summarizes the influence of this parameter on choosing the optimal weights. Combining the special resonant characteristics of the ribbed plate induced by the coupling effects of the ribs, the rule of the influence by the ribs are interpreted particularly. Then experiments are carried out to validate the conclusions. Results obtained can help for choosing the optimal weights of WSSG for the ribbed plate case.

Active Vibration Control of Rib Stiffened Plate by Using Decentralized Velocity Feedback Controllers with Inertial Actuators

Active control of low frequency vibration and sound radiation from a rib stiffened plate has great practical significance as this structure is widely applied in engineering, such as aircraft or ship fuselage shells. This paper presents an investigation on the performance of active vibration control of the rib stiffened plate by using decentralized velocity feedback controllers with inertial actuators. A simple modeling approach in frequency domain is proposed in this research to calculate the control performance. The theoretical model of vibrating response of the ribbed plate and the velocity feedback controllers is first established. Then, as an important part, the influences of the control gain and the number of the decentralized unit on the control performance are investigated. Results obtained demonstrate that—similar to that of the unribbed plate case—appropriately choosing the number of the unit and their feedback gains can achieve good control results. Too many units or very high feedback gains will not bring further noise reduction.

Fluid-structural coupling in metamaterial plates for vibration and noise mitigation in acoustic cavities

Locally resonant metamaterials exhibit sub-wavelength tunable bandgaps that can be exploited for vibroacoustic mitigation. The present work investigates the use of metamaterial plates for the simultaneous control of structural vibration and acoustic sound radiation in an adjacent acoustic cavity. We adopt a coupled fluid-structure finite element model based on a variational mathematical framework in terms of structural displacement and fluid pressure to capture the vibroacoustic characteristics of the coupled system and shed light onto the spatial average pressure levels inside the cavity. The model is used to predict and distinguish between structural and fluid modes within frequency ranges of interest. Furthermore, differences between the metamaterial’s structural response in the presence and lack of fluid coupling are explained. The pressure changes inside the cavity are discussed in relation to the frequency bandgap range predicted theoretically via a dispersion analysis for a couple of different metamaterial designs. Results obtained from the numerical analysis can be used to set design guidelines to optimally tune locally resonant metamaterials to achieve prescribed acoustic properties in the fluid component of such coupled systems.

Sound Radiation Control for Uniform Directionality in the Presence of Strong Early Reflections

Sound Radiation Control for Uniform Directionality in the Presence of Strong Early Reflections