Three-dimensional Acoustic Model Research Articles

Estimation methodology for three-dimensional acoustic modeling: Predicting surf noise soundscapes in coastal urban environments

This research develops an estimation methodology for coastal surf noise soundscapes for implementation in three-dimensional acoustic modeling to improve communication of acoustic design and for assessment with sustainability, wellness and acoustic standards. As sustainability standards include more parameters relating to soundscapes, it is becoming increasing important to develop methods of communicating acoustics to designers in the built environment. Three-dimensional acoustic modeling provides a graphical tool for designers to engage with and understand the impacts multidisciplinary engineering and design decisions have on the soundscape of different parts of a project. As a nation with many coastal urban environments, the view, scents and sounds are all marketing and wellness points for residential and commercial projects. The methodology includes consideration of typical software-agnostic three-dimensional modeling inputs, capabilities and graphical outputs as well as the primary variables that influence measurement and prediction of coastal surf noise in relation to the constant environmental noise. Coast surf noise measurements have been collected and undertaken as part of this work and the data within the method may be updated for most locally measured data. This research aims to enhance the demonstration of soundscapes, facilitating more informed decision-making fostering sustainable development in acoustics, engineering and design.

Digital design and experimental testing of a compressor's suction muffler transmission loss

Abstract The purpose of this paper is to provide a fast, efficient, and low-cost digital design method for the design of suction mufflers in refrigerator compressor plants. The main content of this paper is to establish a three-dimensional acoustic model of the compressor suction muffler by using Solidedge software, combine the upper suction port of the muffler with the valve group, then use Hypermesh to mesh the acoustic model and carry out the theoretical calculation, transform the control differential equation in the solution domain into the integral equation on the boundary by Green's function, discretize the boundary and carry out the numerical solution. The boundary is discretized and solved numerically. The transfer matrix quadrupole parameters are used to describe the acoustic components, and the transfer matrix of the discontinuous cross section is obtained to transform the complex system into a chain superposition of simple systems. The dependent variable in the partial differential equation to be solved is changed to a linear system of equations, and the transmission loss is calculated from the incident and transmitted sound pressure. The theoretical calculation of the transmission loss of the muffler is performed using LMS. Virtual. Lab software and the design solution is continuously optimized using this software. The experimental analysis shows that the designed muffler is printed and trimmed by 3D printing equipment and loaded onto the transmission loss test bench for experimental testing, and the highest theoretical value differs from the test result by 10dB.

Creating an acoustic simulation of noise pollution

This project utilises acoustic simulations to represent traffic noise pollution and prevention in affected residential areas. Noise has “wide-ranging adverse health, social and economic effects” (Goines, 2007, p. 287). Noise pollution `is more severe and widespread than ever before' and is predicted to worsen with growth in highway traffic (Goines, 2007, p. 287). This paper presents the development of a three-dimensional acoustic model of traffic noise pollution. This three-dimensional acoustic simulation is a computer program that enables the user to walk through a modelled housing estate. Road traffic is programmed to drive along a motorway that runs adjacent to the estate. The user experiences traffic noise pollution in real-time while being given the tools to reduce it. The author examines the techniques of propagating noise pollution in three-dimensional space and how noise level is dependent on average speed, category of vehicle and the average number of vehicles passing through a road section (Kephalopoulos, 2014). Reflection and absorption techniques allow noise to move realistically in 3-D space (Funkhouser, 1998; Shearer, 2007; Murphy, 2007; Rober, 2007).

Unsupervised clustering method to convert high-resolution magnetic resonance volumes to three-dimensional acoustic models for full-wave ultrasound simulations

Simulations of acoustic wave propagation, including both the forward and the backward propagations of the wave (also known as full-wave simulations), are increasingly utilized in ultrasound imaging due to their ability to more accurately model important acoustic phenomena. Realistic anatomic models, particularly those of the abdominal wall, are needed to take full advantage of the capabilities of these simulation tools. We describe a method for converting fat-water-separated magnetic resonance imaging (MRI) volumes to anatomical models for ultrasound simulations. These acoustic models are used to map acoustic imaging parameters, such as speed of sound and density, to grid points in an ultrasound simulation. The tissues of these models are segmented from the MRI volumes into five primary classes of tissue in the human abdominal wall (skin, fat, muscle, connective tissue, and nontissue). This segmentation is achieved using an unsupervised machine learning algorithm, fuzzy c-means clustering (FCM), on a multiscale feature representation of the MRI volumes. We describe an automated method for utilizing FCM weights to produce a model that achieves agreement with manual segmentation. Two-dimensional (2-D) and three-dimensional (3-D) full-wave nonlinear ultrasound simulations are conducted, demonstrating the utility of realistic 3-D abdominal wall models over previously available 2-D abdominal wall models.

Making the Most of Focused Ultrasound: Tissue Heating to Improve Chemotherapy Release.

Making the Most of Focused Ultrasound: Tissue Heating to Improve Chemotherapy Release.

Three-dimensional acoustic modeling of a complex harbor environment

Typically, we model sound propagation in the ocean viewing it as an “open” environment where the sound propagates outwards from the source. Of course, targets are reflectors, and other features such as islands and seamounts have been of interest as false targets. However, the standard acoustic models based on rays, normal modes, spectral integrals, and parabolic equations generally consider outgoing energy confined to a single bearing line. In contrast, constrained or partially closed environments such as harbors introduce special issues. Obviously, the sound can be reflected back by seawalls and ship hulls, to mention just a couple of features of harbors environments. Considering coastal environments more broadly, sound reflections also may be caused by wharves, docks, piers, boat landings, quays, floats, groins, and jetties as well as natural features such as submarine canyons. In short, we have sound refracted in the latitude/longitude plane and reflected by a variety of features. In terms of computational ocean acoustics there are few options for modeling such problems. We discuss a comprehensive 3D beam tracing approach implemented in a model called BELLHOP3D that can handle 3D effects including complete reversal of the sound. It is also capable of handling narrowband waveforms (tonals) as well as full broadband timeseries. We will demonstrate and test the model using an example location that is expected to become the site of a future sea test.

Effect of Azimuthally Nonuniform Heat Release on Longitudinal Combustion Instabilities

Combustion instabilities arise from interactions between the acoustic field and unsteady heat release within a confined chamber. In the present study, a three-dimensional acoustic model is developed to explore the effect of azimuthally nonuniform distribution of heat release on longitudinal combustion instabilities. The governing equations are solved by means of a spectral collocation method with domain decomposition to accommodate the flow discontinuities across the flame. It is shown that the circumferential nonuniformity in heat release has only a marginal effect on instability frequency but may cause a potentially significant decrease in the growth rate. For some combinations of flow parameters, a high degree of heat-release asymmetry may qualitatively change the stability characteristics of the combustor, with a sign change of the growth rate. It is found that vorticity waves produced by the azimuthally nonuniform heat release may contribute damping to the thermoacoustic system.

Evaluation of a Cascade-Based Acoustic Model for Fan Tonal Noise Prediction

This study aims at evaluating an analytical model for the prediction of tonal fan noise created by the rotor–stator interaction. The methodology consists of comparing unsteady flow simulations with the cascade-based acoustic model to quantify the influence of some technological effects not included in the model. The simulations are performed with a dedicated turbomachinery flow solver Turb’Flow on a simplified stator vane cascade. They allow discussing the effects of both model assumptions of no vane thickness and inviscid flow on the predictions of the acoustic sources as well as on the modal acoustic powers radiated within the duct. The Kutta condition is found to be efficient to locally represent the viscosity effects, and the vane thickness tends to moderately modify the distributions of the sources and the amplitudes of the duct modes. Moreover, a three-dimensional decomposition of the aerodynamic excitation is proposed and coupled with the three-dimensional analytical cascade response. This fully three-dimensional acoustic model is evaluated by comparisons with an unsteady simulation of a realistic axial compressor stage. An improvement in the prediction of the acoustic sources and powers is clearly shown with respect to the previously used two-dimensional version of the model.

Attenuation of Gas Pulsation in the Valve Chamber of a Reciprocating Compressor Using the Helmholtz Resonator

This paper presents testing and analysis results associated with a new control method based on the Helmholtz resonator to suppress the pressure pulsations in the valve chamber and cylinder nozzle of a reciprocating compressor. The characteristic response of the designed Helmholtz resonator was analyzed and its attenuation characteristics on the gas pulsation were investigated. A three-dimensional acoustic model of the gas pulsation was established by means of the finite element method (FEM) for a compressor discharge piping system with and without the resonator. The gas column natural frequencies of the piping system and the pressure wave profiles were predicted using the presented model and validated by comparing the simulated results with the experimental data. The results showed that the pressure pulsating amplitude in the valve chamber was reduced by 40.4% when the resonator was installed. If the resonance frequency of the resonator shifted from the cylinder nozzle characteristic frequency by a range of ±13%, the reduction in the pressure fluctuations within the valve chamber was about 24%. The best attenuation effectiveness on the valve chamber, a reduction of 47%, was obtained when two resonators were installed on the valve covers of both the head and crank ends. Two new frequencies of 40.4 Hz and 66.9 Hz appeared to replace the original cylinder nozzle characteristic frequency of 53.9 Hz with the Helmholtz resonator installation, and the corresponding resonance region was transferred from the valve chamber to the resonator.

Attenuation of Gas Pulsation in a Reciprocating Compressor Piping System by Using a Volume-Choke-Volume Filter

This paper presents an investigation of the use of a volume-choke-volume low-pass filter to achieve gas pulsation attenuation in a reciprocating compressor piping system, with a focus on its frequency response characteristics and influence on the actual attenuation effects. A three-dimensional acoustic model of the gas pulsation was established for a compressor discharge piping system with and without the volume-choke-volume filter, based on which the gas column natural frequencies of the piping system and the pressure wave profiles were predicted by means of the finite element method. The model was validated by comparing the predicted results with the experimental data. The results showed that the characteristic frequency of the filter was sensitive to both diameter and length of the choke but independent of the parameters of the piping beyond the filter. It is worth noting that the characteristic frequency of the filter constituted one order of the gas column natural frequencies of the piping system with the filter. The pressure pulsation levels in the piping system downstream of the filter could be significantly attenuated especially for the pulsation components at frequencies above the filter’s characteristic frequency. The measured peak-to-peak pressure pulsation at the outlet of the filter was approximately 61.7% lower than that of the surge bottle with the same volume.

Three-dimensional acoustic finite element analysis

Three-dimensional acoustic modeling is a novel application of finite element analysis (FEA) techniques and the successful use of FEA modeling towards the simulation of an empirically tested prototype assembly is described. The finite element analysis method is well known for its applications in structural design. The technique has attained widespread usage in numerous industries and it has enabled engineers to make structural design decisions long before the availability of test hardware or prototypes. The finite element methods, however, are not restricted to structural applications. In fact, this method provides a general approximation scheme, based upon the representation of a continuum by a finite number of interconnected elements. The method is applicable to numerous nonstructural problems and for many of these, the element properties have the same basic features as in the structural model. This paper describes the successful execution of finite element analysis techniques for three-dimensional acoustical analysis.