scholarly journals Numerical and Experimental Studies on Inclined Incidence Parametric Sound Propagation

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Haisen Li ◽  
Jingxin Ma ◽  
Jianjun Zhu ◽  
Baowei Chen
Keyword(s):  
Sound Propagation ◽  
Experimental Studies ◽  
Sound Field ◽  
Source Model ◽  
Calculation Model ◽  
Theoretical Research ◽  
Field Calculation ◽  
Sound Beam ◽  
Sound Fields ◽  
Kzk Equation

The Khokhlov–Zabolotskaya–Kuznetsov (KZK) equation has been widely used in the simulation and calculation of nonlinear sound fields. However, the accuracy of KZK equation reduced due to the deflection of the direction of the sound beam when the sound beam is inclined incidence. In this paper, an equivalent sound source model is proposed to make the calculation direction of KZK calculation model consistent with the sound propagation direction after acoustic refraction, so as to improve the accuracy of sound field calculation under the inclined incident conditions. The theoretical research and pool experiment verify the feasibility and effectiveness of the proposed method.

Synthetic Sound Source Generation for Acoustical Measurements in Turbomachines

2013 ◽  
Author(s):  
Michael Bartelt ◽  
Juan D. Laguna ◽  
Joerg R. Seume
Keyword(s):  
Wind Tunnel ◽  
Sound Source ◽  
Sound Propagation ◽  
Microphone Array ◽  
Sound Field ◽  
Acoustic Mode ◽  
Acoustic Excitation ◽  
Noise Emission ◽  
Noise Sources ◽  
Sound Fields

One of the greatest challenges in modern aircraft propulsion design is the reduction of the engine noise emission in order to develop quieter aircrafts. In the course of a current research project, the sound transport in low pressure turbines is investigated. For the corresponding experimental measurements, a specific acoustic excitation system is developed which can be implemented into the inlet of a turbine test rig and into an aeroacoustic wind tunnel. This allows for an acoustic mode generation and a synthesis of various sound source patterns to simulate typical turbomachinery noise sources such as rotor-stator interaction, etc. The paper presents the acoustical and technical design methodology in detail and addresses the experimental options of the system. Particular attention is paid to the design and the numerical optimization of the acoustic excitation units. To validate the sound generator during operation, measurements are performed in an aeroacoustic wind tunnel. For this purpose, an in-duct microphone array with a specific beamforming algorithm for hard-walled ducts is developed and applied to identify the source locations. The synthetically excited sound fields and the propagating acoustic modes are measured and analyzed by means of modal decomposition techniques. The measurement principles and the results are discussed in detail and it is shown that the intended sound source is produced and the intended sound field is excited. This paper shall contribute to help guide the development of excitation systems for aeroacoustic experiments to better understanding the physics of sound propagation within turbomachines.

scholarly journals Improving the Performance of Mode-Based Sound Propagation Models by Using Perturbation Formulae for Eigenvalues and Eigenfunctions

2021 ◽  
Vol 9 (9) ◽  
pp. 934
Author(s):  
Alena Zakharenko ◽  
Mikhail Trofimov ◽  
Pavel Petrov
Keyword(s):  
Sound Propagation ◽  
Underwater Acoustics ◽  
Computational Cost ◽  
Normal Modes ◽  
Sound Field ◽  
Field Calculation ◽  
Combined Model ◽  
Eigenvalues And Eigenfunctions ◽  
Propagation Models ◽  
Area Of Interest

Numerous sound propagation models in underwater acoustics are based on the representation of a sound field in the form of a decomposition over normal modes. In the framework of such models, the calculation of the field in a range-dependent waveguide (as well as in the case of 3D problems) requires the computation of normal modes for every point within the area of interest (that is, for each pair of horizontal coordinates x,y). This procedure is often responsible for the lion’s share of total computational cost of the field simulation. In this study, we present formulae for perturbation of eigenvalues and eigenfunctions of normal modes under the water depth variations in a shallow-water waveguide. These formulae can reduce the total number of mode computation instances required for a field calculation by a factor of 5–10. We also discuss how these formulae can be used in a combination with a wide-angle mode parabolic equation. The accuracy of such combined model is validated in a series of numerical examples.

THE METHOD OF SEQUENTIAL TRANSFORMATION OF THE SOUND FIELDS

Akustika ◽  
2021 ◽  
pp. 141
Author(s):  
Nickolay Ivanov ◽  
Gennady Kurtsev ◽  
Aleksandr Shashurin
Keyword(s):  
Noise Level ◽  
Sound Absorption ◽  
Sound Propagation ◽  
Sound Field ◽  
Structural Elements ◽  
Noise And Vibration ◽  
Main Assumption ◽  
Efficiency Calculation ◽  
Sound Fields ◽  
Sequential Transformation

A rule for describing the sequential transformation of the sound fields when properties of the surfaces or structural elements change due to such basic processes as sound absorption, reflection, diffraction, or sound divergence is proposed. The main assumption is that sound fields are non-coherent, i.e., resonant phenomena and sound interference are not considered. The examples show solutions to such problems: - sound propagation in space if there are artificial structures; - sound propagation in the rooms; - efficiency calculation of the noise protection structures; - calculation of the expected noise level of the machinery and separation of the contribution of noise and vibration sources to sound fields (for example, an external sound field, a sound field in the office, etc.)

NON-PARABOLIC MARCHING ALGORITHM FOR SOUND FIELD CALCULATION IN THE OCEAN WAVEGUIDE

1996 ◽  
Vol 04 (04) ◽  
pp. 399-423 ◽  
Author(s):  
A. VORONOVICH
Keyword(s):  
Sound Propagation ◽  
A Priori ◽  
Numerical Algorithms ◽  
Sound Field ◽  
Computer Code ◽  
Couple Mode ◽  
Field Calculation ◽  
Piecewise Constant ◽  
S Matrix ◽  
Piecewise Constant Approximation

An algorithm is presented for calculating sound field in the inhomogeneous ocean waveguide. It does not involve parabolic approximation and can be considered as principally exact (at least for 2D inhomogeneities of the sound speed field). On the other hand, it is “marching” and can be easily implemented as a computer code (note, that marching in this case proceeds in “backward” direction, i.e. towards the source). Those features of the code are similar to couple mode algorithm (COUPLE) developed originally by R. Evans. The principal difference is that suggested code does not assume piecewise constant approximation of the waveguide properties with respect to horizontal coordinates. As a result, the horizontal steps of marching can be increased significantly. The estimate of the efficiency of the approach as compared to stepwise couple modes method is given. The results of the code testing with the help of benchmark problem as well as calculation of sound propagation through a strong inhomogeneity formed by the sub-arctic front are presented. The present version of the code can be used to calculate entries of scattering matrix (S-matrix) for the ocean waveguide as well as travel times of different modes (derivatives of phases of corresponding entries with respect to frequency). A priori restrictions on S-matrix (reciprocity and energy conservation) are also given, and some objective quantitative criterion of the accuracy of the numerical algorithms formulated in terms of S-matrix is suggested.

On the Acoustics of Auditoria

1994 ◽  
Vol 1 (1) ◽  
pp. 27-48 ◽  
Author(s):  
H. Kuttruff
Keyword(s):  
Sound Propagation ◽  
Sound Field ◽  
Great Benefit ◽  
Room Acoustics ◽  
Short Introduction ◽  
New Developments ◽  
Sound Fields ◽  
Field Simulation ◽  
Basic Facts

The paper presents a short introduction into auditorium acoustics and reports on a few new developments in this field, which are believed to be of great benefit both for the acoustical design of auditoria and for research in practical room acoustics. The first part describes in a rather elementary way the basic facts of sound propagation in enclosures, including the effects of reflections and the role of reverberation. Furthermore, some of the numerous objective parameters are discussed which have been introduced in order to characterize particular aspects of sound fields. In the second part, recently developed methods of sound field simulation are described by which such parameters can be predicted. Methods of “auralization” are briefly discussed by which aural impressions from non-existing halls can be created on the basis of digital sound field simulation.

An Acoustic Excitation System for the Generation of Turbomachinery Specific Sound Fields: Part I — Design and Methodology

2016 ◽  
Author(s):  
Akif Mumcu ◽  
Christian Keller ◽  
C. Mandanna Hurfar ◽  
Joerg R. Seume
Keyword(s):  
Sound Propagation ◽  
Microphone Array ◽  
Sound Field ◽  
Radial Mode ◽  
Mode Analysis ◽  
Acoustic Excitation ◽  
Axial Distribution ◽  
Excitation System ◽  
Sound Fields ◽  
Duct Wall

A strong focus in the development of modern aircraft engines is the reduction of the engine tonal core noise. For the development of efficient noise reduction techniques, a detailed understanding of the sound transmission throughout all turbomachinery components of the engine is mandatory. In this paper an excitation system is developed to generate turbomachinery-specific sound fields by controlling their circumferential and radial mode order. The excitation system consists of two rows of eight loudspeakers distributed circumferentially around the outer duct wall. This paper gives a detailed description of the analytically- and numerically-supported design methodology of an optimized excitation system, as well as an optimized microphone array mounted flush with the outer duct wall. A sensitivity analysis of the loudspeaker array and of the microphone array with respect to distance and frequency is then carried out numerically. To analyze the microphone signals and to deconstruct the propagating sound field into its modal components, a Radial Mode Analysis (RMA) is carried out. To ensure high-quality RMA results, the axial distribution of the microphones is optimized with respect to the condition number of the array’s transfer matrix. The procedure explained in this paper shall help guide the development of acoustic excitation and microphone array systems for experiments to better understand sound propagation in turbomachinery and flow ducts.

scholarly journals Coherent Image Source Modeling of Sound Fields in Long Spaces with a Sound-Absorbing Ceiling

2021 ◽  
Vol 11 (15) ◽  
pp. 6743
Author(s):  
Hequn Min ◽  
Ke Xu
Keyword(s):  
Sound Field ◽  
Wave Theory ◽  
Source Model ◽  
Scale Model ◽  
Source Modeling ◽  
Image Source ◽  
Sound Fields ◽  
Absorbing Boundaries ◽  
Proposed Model ◽  
Coherent Image

Sound-absorbing boundaries can attenuate noise propagation in practical long spaces, but fast and accurate sound field modeling in this situation is still difficult. This paper presents a coherent image source model for simple yet accurate prediction of the sound field in long enclosures with a sound absorbing ceiling. In the proposed model, the reflections on the absorbent boundary are separated from those on reflective ones during evaluating reflection coefficients. The model is compared with the classic wave theory, an existing coherent image source model and a scale-model experiment. The results show that the proposed model provides remarkable accuracy advantage over the existing models yet is fast for sound prediction in long spaces.

Technical Note: Prediction of the Characteristics of Complicated Sound Fields in Long Enclosures by a Beam-Tracing Method

2002 ◽  
Vol 9 (2) ◽  
pp. 139-150 ◽  
Author(s):  
Xiangyang Zeng ◽  
Jincai Sun ◽  
Ke'an Chen
Keyword(s):  
Sound Pressure ◽  
Sound Propagation ◽  
Sound Field ◽  
Technical Note ◽  
Pressure Level ◽  
Reverberation Time ◽  
Complex Sound ◽  
Sound Fields ◽  
Sound Receiver ◽  
The Subject

The subject of this paper is the characterisation of the sound field in long enclosures. A beam-tracing computer model has been developed especially for the simulation of sound propagation throughout long enclosures. Surface diffusing reflection and air absorption are included in the model, which can predict the impulse response and acoustic indexes at arbitrary positions in the enclosure. This paper describes how the algorithm models the sound source, sound propagation and sound receiver. The algorithm was then tested in both common rooms and long enclosures by comparison of the measurement, theoretical calculation and prediction results. The characteristics of more complex sound fields in long enclosures, the prediction of reverberation time, early decay time and sound pressure level, etc, at individual points are discussed in terms of the algorithm. The results indicate that the primary characteristics of complicated sound fields in non-rectangular long enclosures are similar to those in rectangular ones.

scholarly journals Identification of Sleeper Support Conditions Using Mechanical Model Supported Data-Driven Approach

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3609
Author(s):  
Mykola Sysyn ◽  
Michal Przybylowicz ◽  
Olga Nabochenko ◽  
Lei Kou
Keyword(s):  
High Speed ◽  
Experimental Studies ◽  
Dynamic Interaction ◽  
Theoretical Research ◽  
Rolling Stock ◽  
Monitoring Methods ◽  
Beam Dynamic ◽  
Track Geometry ◽  
Data Driven Approach ◽  
Support Conditions

The ballasted track superstructure is characterized by a relative quick deterioration of track geometry due to ballast settlements and the accumulation of sleeper voids. The track zones with the sleeper voids differ from the geometrical irregularities with increased dynamic loading, high vibration, and unfavorable ballast-bed and sleeper contact conditions. This causes the accelerated growth of the inhomogeneous settlements, resulting in maintenance-expensive local instabilities that influence transportation reliability and availability. The recent identification and evaluation of the sleeper support conditions using track-side and on-board monitoring methods can help planning prevention activities to avoid or delay the development of local instabilities such as ballast breakdown, white spots, subgrade defects, etc. The paper presents theoretical and experimental studies that are directed at the development of the methods for sleeper support identification. The distinctive features of the dynamic behavior in the void zone compared to the equivalent geometrical irregularity are identified by numeric simulation using a three-beam dynamic model, taking into account superstructure and rolling stock dynamic interaction. The spectral features in time domain in scalograms and scattergrams are analyzed. Additionally, the theoretical research enabled to determine the similarities and differences of the dynamic interaction from the viewpoint of track-side and on-board measurements. The method of experimental investigation is presented by multipoint track-side measurements of rail-dynamic displacements using high-speed video records and digital imaging correlation (DIC) methods. The method is used to collect the statistical information from different-extent voided zones and the corresponding reference zones without voids. The applied machine learning methods enable the exact recent void identification using the wavelet scattering feature extraction from track-side measurements. A case study of the method application for an on-board measurement shows the moderate results of the recent void identification as well as the potential ways of its improvement.

The Finite Element Analysis of the Large-Scale Converter Transformer Valve Side of the Electric Field

2013 ◽  
Vol 325-326 ◽  
pp. 476-479 ◽  
Author(s):  
Lin Suo Zeng ◽  
Zhe Wu
Keyword(s):  
Finite Element ◽  
Electric Field ◽  
Large Scale ◽  
Calculation Model ◽  
Simulation Software ◽  
Field Calculation ◽  
Element Analysis ◽  
Ansys Simulation ◽  
The Finite Element Analysis ◽  
Electric Field Calculation

This article is based on finite element theory and use ANSYS simulation software to establish electric field calculation model of converter transformer for a ±800kV and make electric field calculation and analysis for valve winding. Converter transformer valve winding contour distribution of electric field have completed in the AC, DC and polarity reversal voltage.

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