Design Of Acoustic System Research Articles

Smart controllable wave dispersion in acoustic metamaterials using magnetorheological elastomers

The success in the flexible design of smart acoustic metamaterials is crucially contingent upon the degree of control over the parameters that uniquely define the spectrum of band structure and morphology of dispersion surfaces. In this work, we have studied the driving physical mechanisms, the control of which makes possible operating, in real-time, on the set of band gaps formed in 3D metamaterials based on magneto elastomers. In such acoustic structures, the stiffness of the medium in which unit cells are immersed, as well as the stiffness of the shells surrounding multi-particle cores depend on the induction, B(t), of an external magnetic field. The results obtained are systematized through the qualitative analysis of diversе scenarios for the evolution of the frequency characteristics of the metamaterial and summarized in the following complete physical picture of their dynamics. Variation of the stiffness of the medium/shells changes the wavelength of the shell's surface waves at characteristic frequencies of the core vibrations and, as a result, the level of coupling between the vibration modes of the flexible shells and cores. Consequently, with an increase/decrease in the stiffnesses of the shells/medium, the dispersion surfaces of the entire acoustic system shift up/down along the frequency axis with noticeably different ‘mobilities’ that reversibly lead either to the formation of the band gaps in initially dense frequency spectrum or to the transformation of the band gaps formed into pass bands. The tuning of the set of dispersion surfaces depending on the range of changes in the magnetic field induction can be carried out in dynamic, quasi-stationary, and over-critical regimes when some of the dispersion surfaces degenerate into planes. In anisotropic metamaterials, simultaneously with creating full band gaps, it is possible to create tunable directional band gaps with adjustable frequency and angular widths. The results obtained, within the framework of the idealized discrete mass-spring model, are in good agreement with the data presented in the available experimental works and can be useful in the design of acoustic systems with desirable properties.

Acoustic system design and experimental research on the ultrasonic forming grinding gear

Acoustic system design and experimental research on the ultrasonic forming grinding gear

Simulation and Optimization of Acoustic Package of Dash Panel Based on SEA

The instrument panel assembly is an important structure to shield powertrain noise and front wheel noise, and the instrument panel sound insulation system plays a key role in it. Therefore, the sound insulation characteristics of the instrument panel sound insulation components appear particularly important. In the existing technology, the acoustic design of instrument panel mostly adopts the reverse design method and pays little attention to the forward design of acoustic system, which tends to lead to the shortcomings such as inaccurate acoustic design and poor acoustic design quality. The reverse design also restricts the development cycle, so the control and design of acoustic performance cannot be realized in the initial stage of design. Based on the above problems, the statistical energy model of the dashboard model was established by combining the statistical energy flow method and the proxy model method, and the influences of different acoustic cladding layers, different thickness, leakage, and new material microfibers on the sound insulation parameters of the front coaming were simulated. The general rules that affect the sound insulation performance of the structure are obtained. On this basis, multiobjective genetic algorithm and proxy model method are used to optimize the insertion loss of the front panel acoustic pack and the weight of the dashboard by introducing multiobjective variable and experimental design method, so as to obtain the best solution to meet the requirements of insertion loss and lightweight acoustic pack of the dashboard. It is of great engineering significance for the development of acoustic components for forward design instrument panel.

Three-dimensional broadband omnidirectional acoustic ground cloak

The control of sound propagation and reflection has always been the goal of engineers involved in the design of acoustic systems. A recent design approach based on coordinate transformations, which is applicable to many physical systems, together with the development of a new class of engineered materials called metamaterials, has opened the road to the unconstrained control of sound. However, the ideal material parameters prescribed by this methodology are complex and challenging to obtain experimentally, even using metamaterial design approaches. Not surprisingly, experimental demonstration of devices obtained using transformation acoustics is difficult, and has been implemented only in two-dimensional configurations. Here, we demonstrate the design and experimental characterization of an almost perfect three-dimensional, broadband, and, most importantly, omnidirectional acoustic device that renders a region of space three wavelengths in diameter invisible to sound.

Design and implementation of a passive acoustic bedload monitoring surrogate system

Various methods of employing passive acoustics to monitor bedload transport by listening to noise generated by colliding gravel have been explored in both the lab and field. Expanding upon this research, a hydrophone-based passive bedload-monitoring system was designed, tested, and deployed by researchers at the University of Mississippi and the National Sedimentation Laboratory in Oxford, MS. A series of laboratory experiments was used to measure the dependence of acoustic propagation on various parameters such as depth of the water and placement of the hydrophones. These tests employed a calibrated acoustic transmitter to broadcast tones of various frequencies across a gravel bed. Additional flume tests used a motorized carrier to drag rocks across the gravel bed, allowing a known sediment flux to be measured acoustically without any flow noise. The hydrophone-based system was deployed on the Trinity River, Weaverville, CA, in the summer of 2012 and the Elwha River, Port Angeles, WA, in the summer of 2013. Both deployments were co-incident with physical bedload measurements taken by Graham Mathews and Associates. The design of the acoustic system, methods used to analyze the data, results from laboratory experiments, and preliminary results from field data collection will be presented.

Design of Longitudinal-Torsional Vibration Stepped Horn with Multiple Diagonal Slits

Based on the theory of acoustic propagation, the realization mechanism of longitudinal-torsional vibration (LTV) by converter of cylinder with multiple diagonal slits (MDS) under single excitation was studied. The influences of composite stepped horns structural parameters on resonant frequency were studied by numerical analysis method, and the horn (resonant frequency about 20kHz) with LTV was designed. The results show that LTV could be realized under single excitation of longitudinal vibration when resonant frequency is 20498Hz, and the amplitude varied periodically. The results can be applied in the design of acoustic system in ultrasonic machining with LTV.

Kinematics Analysis on Ultrasonic Deep Rolling with Longitudinal-Torsional Vibration

The kinematics model was built based on the principle of ultrasonic deep rolling (UDR) with longitudinal-torsional vibration (LTV), and the trajectory equations of any particles on edge of the roller involved in the process were given; the influences of vibration parameters including phase angle, frequency of LTV, amplitude of longitudinal vibration, amplitude ratio and the rolling process parameters including roller radius, rolling depth, feed rate, the rotation frequency of roller on the trajectory, acoustic system design and processing quality were discussed. The results can provide theoretical basis for the design of acoustic system and optimization of process parameters.

Evaluating transducer bandwidth and effectiveness on overall acoustic system performance

Piezoelectric ceramic cylindrical transducers are used extensively for underwater acoustic communication applications on mobile platforms (UUVs). Employing piezoelectric single crystals, used in either fully-active or active-passive segmented cylinders, in the transducer design has the potential to increase the usable bandwidth while reducing the overall size and weight of the device. In some instances, one single crystal transducer may replace several ceramic transducers and reduce the number of hardware channels. The impact on acoustic system design (power amplifier, matching transformer, and tuning network) for several piezoelectric ceramic and single crystal cylindrical transducer technologies is modeled and supported with measured transducer data.

Advanced Applications for Underwater Acoustic Modeling

Changes in the ocean soundscape have been driven by anthropogenic activity (e.g., naval-sonar systems, seismic-exploration activity, maritime shipping and windfarm development) and by natural factors (e.g., climate change and ocean acidification). New regulatory initiatives have placed additional restrictions on uses of sound in the ocean: mitigation of marine-mammal endangerment is now an integral consideration in acoustic-system design and operation. Modeling tools traditionally used in underwater acoustics have undergone a necessary transformation to respond to the rapidly changing requirements imposed by this new soundscape. Advanced modeling techniques now include forward and inverse applications, integrated-modeling approaches, nonintrusive measurements, and novel processing methods. A 32-year baseline inventory of modeling techniques has been updated to reflect these new developments including the basic mathematics and references to the key literature. Charts have been provided to guide soundscape practitioners to the most efficient modeling techniques for any given application.

A terminal-boundary value problem that describes the process of damping the vibrations of a rod consisting of two segments with different densities and elasticity coefficients but with identical wave travel times

In this paper, in terms of a finite-energy weak solution, we study a terminal-boundary value problem describing the complete damping, at a terminal time T, of the longitudinal vibrations of a rod consisting of two segments with different densities and elasticity coefficients under the condition that the lengths of the segments are such that the wave travel times along these segments are equal. We find an explicit analytic expression for a solution to this problem and prove its uniqueness. This problem is important for the design of acoustic systems in which one can completely damp an acoustic signal by a terminal time instant by applying boundary controls at the ends of a vibrating rod.