Sound Distribution Research Articles

Managing Interdependencies in Federal Systems: Intergovernmental Councils and the Making of Public PolicyJohannaSchnabelCham, Palgrave Macmillan (2020), 286 p., ISBN 978‐3‐030‐35460‐2

Managing Interdependencies in Federal Systems: Intergovernmental Councils and the Making of Public PolicyJohannaSchnabelCham, Palgrave Macmillan (2020), 286 p., ISBN 978‐3‐030‐35460‐2

Absolute reconstruction of Ultrasonic Tomography for oil-water biphasic medium imaging using modified ray-tracing technique

Oil-water biphasic medium widely existed in mining and transportation process of petroleum industry, where visualized measurement processes vital importance in production increase, state monitoring and fault prognosis. Ultrasonic Tomography (UT) is a non-invasive and non-radioactive sensing modality in industrial Process Tomography, which is demonstrated as a competitive monitoring technique with great potential. However, facing the refraction effect of Ultrasound wave at oil-water interfaces, the accuracy of reconstruction algorithm is with large error and serious artifacts. To address the issue, a modified ray-tracing image reconstruction algorithm is proposed. The amplitude attenuation during ultrasound propagation in nonhomogeneous medium is quantitatively modeled to form absolute UT model. With ray tracing strategy applied and improved, the nonlinear refraction effect is characterized in the form of iterative update of sensitivity matrix, followed by which the sound speed mapping transfers reconstructed attenuation images to sound speed distribution for ray tracing computation. Numerical tests indicate that the proposed method significantly improves reconstruction accuracy through projection-based, regularization-based and algebraic-based inverse algorithms, which demonstrate its benefits in conducting oil-water biphasic medium imaging.

Rounding Harmony in Mfantse: Evidence and Differences

This paper investigated rounding harmony in two subdialects of Mfantse spoken in the Central Region of Ghana. Bɔrbɔr and Edwumako dialects are part of the Akan language and belongs to Kwa on the Niger-Congo branch of languages. Data was from the Mfantseman and Edwumako districts from 45 participants aged 20 years and above. The Autosegmental framework was used for data analysis. We looked first at the sounds and brought out the differences between Bɔrbɔr sounds and that of Edwumako. The study established that Mfantse is not the same in all its phonological presentations in all its subdialects. In terms of sound distribution, the central unadvanced vowel is strictly word final in Bɔrbɔr while it is both word initial and final in Edwumako. Some aspects of rounding harmony occur in both Bɔrbɔr and Edwumako while other aspects occur in Bɔrbɔr and partially in Edwumako. Other aspects are present in Edwumako only.

BENTUK PENYAJIAN KESENIAN KASIDAH REBANA DALAM ACARA PESTA PERKAWINAN DI JORONG SAROHA TAMIANG KECAMATAN LEMBAH MELINTANG KABUPATEN PASAMAN BARAT

AbstractThis research aims to describe the form of a Kasidah Rebana presentation in a wedding party in Jorong SarohaTamiang, Lembah Melintang District, West Pasaman Regency. This research is a qualitative research which focuseson getting issues related to the topic. The data were collected through literature study, observation, interviews, and documentation. The development of sophisticated era and the cultures and arts developed in community give positive and negative effects. However, the art of Kasidah Rebana in the Jorong Saroha Tamiang still exists and is the choice of the community to be presented in a wedding party.The presentation form of Kasidah Rebana in the wedding party now has undergone many changes towards a more modern direction in accordance with the times. This can be seen from the sound system and formations, which neatly arranged by the group on stage, provided by the committee. Based on the composition, the rhythm pattern played is in accordance to the rhythmic musical instrument as well as the keyboard melody combined with chord harmonization and sound distribution. The vocalist sings the song according to the structure of the song's form and the expression according to the song's verse. These are combined to produce a beautiful tambourine blend.Based on the results of the study, to be more creative is an advice the author gives to the group. Song references, music compositions and costumes can be differently arranged, for instance. Thus, it is more interesting and more demanded by the community. The form of a Kasidah Rebana presentation is a mixed ensemble played by 12 players consisting of two vocalists, two tambourine players, two rhythm players, two bass players, three ketipung players, and one keyboard player.Keywords: form of presentation, kasidah rebana, wedding party

Experimental characterization of high-intensity focused airborne ultrasound fields.

High-intensity focused airborne ultrasound fields are increasingly applied in various technical fields, for example, to generate haptic feedback during gesture interaction. Reliable measurement data of sound pressure levels are required to assess potential health hazards to users. Such ultrasound fields pose special challenges for a quantitative characterization. The high sound pressure levels in combination with the higher harmonics generated by nonlinear effects require both a high upper limit of the level linearity range and a wide bandwidth of the measuring chain. Furthermore, small wavelengths and the focusing result in spatially strongly varying sound fields. In the present case, a 40 kHz signal was focused on a single point using a transducer array. Different microphone types were investigated with respect to their suitability for measuring high-power airborne ultrasound fields. A spatial characterization of the ultrasound field in the focal region as well as around an artificial head in a simulated application situation was performed. The microphone measurements were supplemented by measuring the radiation force with a balance and were compared to an analytical model of the sound field distribution. The presented results can contribute to the improvement of measurement technology and support a first assessment of the exposure of potential users.

Parameter Optimization of Impedance Gradient Change Medium Based on Reinforcement Learning

Based on the relative researches, in order to solve the problem that the parameters of impedance gradient change medium are difficult to be optimized and generalized in different environments, an optimization method of the parameters of the impedance gradient change medium based on reinforcement learning was proposed. First, the propagation principle of sound wave in impedance gradient medium was analyzed. The sound field distribution in the medium was also studied, in order to master its acoustic characteristics. Second, the parameters of sound velocity and impedance distribution were optimized by DQN algorithm to reduce the sound reflection. Finally, the effectiveness of the proposed reinforcement learning model was verified by the traditional method. The experimental results show that the method presented in this paper was superior to the traditional method. The trained parameters are effective to reduce the acoustic reflection to a lower level.

Effect of Mach number on the mode transition for supersonic cavity flows

Direct numerical simulations of supersonic flows past a two-dimensional cavity with a length-to-depth ratio of 4 under different Mach numbers are performed. Firstly, as the Mach number increased from 1.1 to 2.7 with a small initial boundary layer thickness, the dominant flow mode transforms from a wake mode to the Rossiter II mode, and to the Rossiter III mode, then to a steady mode. Meanwhile, a low frequency mode appears, and then disappears due to the change of vortex-corner interactions. With a sufficiently large initial boundary layer thickness, the wake mode is not obtained, and the dominant flow mode will change from the Rossiter II mode to the steady mode directly. Secondly, in the shear layer mode, the local sound pressure level for the dominant mode and the overall sound pressure level distributions on the cavity floor show reduced pressure oscillations with increased Mach number due to the weakened shear layer instability. Thirdly, the variation of the vortex structures is more complex, and pressure oscillations have a stronger impact on the mean flow in the wake mode, comparing with the shear layer mode. Finally, a dynamic mode decomposition approach is performed to obtain dynamic information. The oscillation frequencies obtained from the dynamic mode decomposition are consistent with the results of local power spectral density analysis, and the dominant mode transition is detected by the dynamic modes obtained from the dynamic mode decomposition.

Factors influencing low-frequency noise reduction in typical Chinese dwelling layouts

Existing approaches to reducing the low-frequency noise exposure of dwellings are not always sufficient. This study investigated the significance of dwelling layout design for low-frequency noise control. The sound distribution in six typical Chinese dwelling layouts was analysed using in-situ measurements under steady-state noise of various low frequencies. The results showed that among two-bedroom dwelling layouts, the overall average noise reduction varied considerably (6 dB). The noise reduction for room levels (number of rooms sound crosses) 1–2 and 2–3 varies by 5 and 3 dB, respectively, and the noise reduction at door openings varies by 5 dB. A model to approximate the low-frequency noise reduction of a layout was developed using the polyline distance from the noise source and the number of walls the polyline has to cross, which were clearly shown to influence low-frequency noise reduction and seem to be the strongest investigated factors.

Using a 2.5D boundary element model to predict the sound distribution on train external surfaces due to rolling noise

In order to be able to predict train interior noise, it is first important to calculate the external sound pressure distribution on the floor, sidewalls and roof. This can then be combined with the transmission loss of the train panels to determine the interior noise. Traditional techniques such as the finite element and boundary element (FE/BE) methods in three dimensions (3D) can achieve this result but are computationally very expensive. In this paper, a wavenumber-domain boundary element (2.5D BE) approach is instead adopted to predict the propagation of rolling noise from the wheels, rails and sleepers to the train external surfaces. In the 2.5D models, only the cross-section of the vehicle is represented by using boundary elements, while the third direction is considered in terms of a spectrum of wavenumbers. The rail is treated directly in the wavenumber domain but, to include the wheel, a method of representing point sources in a 2.5D approach is developed. An inverse Fourier transform is applied to obtain the spatial distribution of the sound pressure on the train surfaces. The validity of this approach has been verified by comparison with experimental data. The 2.5D BE method was first used to predict the sound distribution on a 1:5 scale train surfaces due to a point source below the vehicle, and later it was used to predict the sound pressure on a full-scale metro vehicle due to a loudspeaker. Comparisons of predictions with measurements on the scale model and on the metro vehicle showed good agreements. For a point source below the vehicle, the sound pressure levels on the train floor were found to be around 20 dB higher than on the sides, and the sound pressure on the train roof was negligible. The 2.5D BE method was also used to predict the sound pressure on the metro vehicle surfaces in running operation, in which the predicted sound pressure levels on the train external surfaces agreed with measurements to within 3 dB and similar trends were found in terms of spectra and longitudinal distribution of pressure.

FEM based 3D modelling of partial discharge detection and localization in an oil-filled power transformer using piezoelectric acoustic sensor

Abstract The main cause of insulation degradation is due to partial discharges (PDs) occurring inside the transformer, and its detection and localization are the most effective, non-destructive methods to assess the insulation condition of the transformer. Among the PD detection methods, the acoustic PD detection technique is popular because of its various advantages. The acoustic PD detection method for accurate PD source localization becomes quite challenging when PD occurs inside the transformer core and windings. As the acoustic sound wave can be distorted and vibration with its distribution, so the type of PD sensors with their setting in the transformer should be thoroughly investigated and chosen. In this work, via simulation, the acoustic sound distribution inside the power transformer due to PD occurs is studied. Based on the knowledge of acoustic pressure wave distribution, a Lead Zirconate Titanate (PZT-5H) sensor is designed using Finite element method based COMSOL Multiphysics software and placed it on the outer walls of the transformer for PD detection and localization. The PD induction position has been recognized from the sensor signal using an artificial neural network. The results of PD detection and localization by the proposed piezoelectric sensor and COMSOL probe point are in good agreement.

Ultrasound Computed Tomography of Knee Joint

Ultrasound computed tomography (UCT) is considered to have great potential for the early diagnosis of knee joint injuries. Combining prior knowledge and sound speeds of tissues, UCT can diagnose a variety of symptoms and the extent of tissue lesion. However, no existing studies can reconstruct the sound speed distributions of knee joints in UCT. Therefore, in this study, sound speed distributions of knee joints are reconstructed to provide an imaging basis for the formulation of a treatment plan. In addition, Full waveform inversion (FWI) methods are utilized to estimate highresolution images. However, for media with large variations in sound speeds, traditional FWI methods may lead to a cycle-skipping phenomenon and incorrect convergence direction. Hence, this study proposes a multi-centerfrequency source based FWI method to overcome the above limitations. A penalized least-squares optimization problem is constructed to obtain a numerical solution of the sound speed distribution. Computer simulations are conducted to prove the effectiveness and robustness of the proposed method. Furthermore, the reasons for selecting the center frequencies of sources are analyzed. Two numerical knee joint phantoms are used to evaluate the performance. The results suggest that the biases of the reconstructed images are less than 1% under a 5% noise condition.

Examining Unintentionality and Intentionality of Sound in Prehistoric Malta

This paper attempts to give an idea of the sonorous past of prehistoric Malta by presenting possible soundscape scenarios. It validates the importance of sound as auditory experience, because this was crucial in the history of humanity, while it attempts to trace the beginnings of organised sound. This research is to introduce a number of findings that are connected to sound perception and distribution among the inhabitants of Malta. Specific emphasis is given to discussions of whether these sounds were essentially intentional or not. By going through the collected facts about the introduced findings, there are overlaps in functions and sound tools that indicate an early cultivation of music. In protecting the related findings, some of these early attempts can be hopefully reconstructed in the future.

Acousmatic Music: Principles of Graphic Visualization

The article analyzes approaches to graphic visualization of acousmatic music. The specificity of this electronic music’s genre variety is considered, the characteristic features of which are masking of the sound source and the absence of traditional written encryption – notation.The purpose of this research is to reveal the modern possibilities of graphic visualization of acousmatic works.The research methodology of the research is based on the use of the structural-functional methods to study the attributive characteristics of sound objects, as well as a comparative method aimed at analyzing different sound approaches to electronic scores. The principles of transforming the functions of musical notation in acousmatic works are revealed. It is noted that due to the absence of the performer, the notation loses its most important role – to serve as an instruction for repeatedly playing music since the composition is recorded in the studio and broadcast at the concert in the form of a phonogram.The scientific novelty of the research is to improve approaches to the study of avant-garde electronic music without author’s notation. Based on the study of composer’s scores “Vivente non vivente” by S. Gubaidulina, “Articulations” by D. Ligeti, “Electronic study No. 2” by K. Stockhausen, which are created on the basis of audio recordings, the functions of graphic fixation carried out after sounding are analyzed. Analogies with the notation of folk songs are drawn. Computer methods for visualizing acoustic processes are considered. It was revealed that almost all of them have the form of a graph of the sound vibrations distribution in the coordinates of frequency and time corresponding to the vertical and horizontal of traditional notation. The disadvantages of the automatic image of acoustic processes that do not reveal the uniqueness of the timbre and texture of sound objects are analyzed. A comparison of different musicological approaches to solving this problem made.Conclusions. The necessity of creating visualization for the study of compositions that do not have an author’s score has been substantiated. Based on the study of avant-garde notation patterns, an assumption has been formulated regarding the type and characteristics of graphic symbols. The principles of acousmographic visualization, which adds written signs to the sonogram aimed at revealing the author’s intention, have been investigated.

Applied current thermoacoustic imaging for biological tissues.

BACKGROUND: The large differences of electrical characteristics can be used to reflect the physiological and pathological changes about biological tissues, and it can provide evidence for the early diagnosis and treatment of cancer in potential applications.OBJECTIVE: This paper describes a method called Applied Current Thermoacoustic Imaging (ACTAI) and explores the theory and demonstrates a low conductivity numerical simulation and fresh pork experimental studies.METHODS: In this paper, firstly, the principle of ACTAI is studied. In ACTAI, a target is applied with a microsecond width Gaussian pulse current. Then the target absorbs Joule heat and expands instantaneously, sending out thermoacoustic waves. The waves contain the conductivity information of the target. The waves received by sound transducers are processed by the time inversion method to reconstruct the sound source distribution of the target to illustrate the conductivity information of the target. Secondly, a square model with low conductivity was used as a target to conduct numerical simulation of ACTAI. Lastly, a fresh pork experiment study was conducted.RESULTS: The presented experimental results suggest that ACTAI can identify the conductivity changes information of the target with perfect imagery contrast and deep penetration.CONCLUSION: The ACTAI modality would benefit from the noncontact measurement and can be convenient for clinical application.

Structural Diagnostics of Superconducting Magnets Using Diffuse Field Ultrasound

Among various diagnostics, acoustic techniques are valuable for characterizing mechanical instabilities associated with lengthy training, premature quenching and other performance limitations of high-field accelerator magnets. While acoustic emissions from magnets were studied since early 80 s, techniques involving external acoustic excitation have so far been of limited use. As such techniques are already well-developed in materials science and geoscience, they offer a great potential for the superconducting magnet applications. In a typical magnet coil an acoustic pulse emitted by a coupled ultrasonic transducer would experience multiple scatterings from boundaries and interfaces along its propagation path, in resemblance to a diffusion process. The resulting diffuse ultrasonic field uniquely samples geometrical boundaries, scatterer locations and sound velocity distribution in the propagation medium. Variation of these properties can be tracked in real time and with high accuracy by monitoring shape distortions and temporal shift of the ultrasonic waveforms acquired by sensors coupled to the coil. We discuss key physical principles and capabilities of diffuse field ultrasound, and give examples of using it for detecting interface instabilities in Canted Cosine Theta (CCT) Nb3Sn superconducting accelerator magnets built by the US Magnet Development Program.

On the role of acoustic reflections from duct boundaries in fan flutter

The role that acoustic reflections from duct boundaries play in aeroengine fan flutter is theoretically investigated. To make a systematic parametric study attainable, a three-dimensional semi-analytical approach is employed. Based on the transfer element method combined with a boundary integral equation method, this approach effectively captures the acoustic coupling effect of an annular rotor undergoing incipient oscillation and a finite-length non-rigid duct in subsonic flow. For a given vibration mode, the disturbances generated both inside and outside the duct are determined by a simultaneous solution. The flutter likelihood is subsequently evaluated through the energy method. Results reveal that near the flutter boundary, the aeroelastic impact of duct boundary reflections becomes evident and critical when propagating (cut-on or weakly damped) acoustic modes exist in the flow duct. Under such condition the aerodynamic interaction between both duct openings strongly affects the sound field distribution, thus contributing to the notable installation effect on aeroelastic stability. Moreover, the flutter-driven acoustic field is also susceptible to the sound reflection effect of the partially lined duct wall. It is found that the variation of the blade aerodynamic damping with the liner impedance is markedly different when the duct end reflections come into play. Under appropriate conditions the mutual effect of the lined wall and the duct openings significantly strengthens their acoustic couplings with the ducted fan, where a reasonable estimate of aeroelastic stability can only be provided with an adequate consideration of the realistic acoustic boundary conditions for the entire duct.

Novel reconstruction algorithm of magnetoacoustic tomography based on ring transducer array for acoustic speed inhomogeneous tissues.

Magnetoacoustic tomography with magnetic induction (MAT-MI) is a technique that utilizes the acoustic signals induced by magnetic stimulation to reconstruct the electrical impedance distribution in biological tissues. Most algorithms ignored the fact that acoustic properties in human tissues are heterogeneous, which lead to distortion and blurring of small reconstructed objects. In this study, a novel algorithm is proposed for exact reconstruction of the sound source distribution in acoustic heterogeneous tissues. Based on the ring transducer array, we develop an algorithm which combines algebraic reconstruction technique (ART) and time reversal method. Different to existing reconstruction methods, the ultrasonic transmission tomography (UTT) and the MAT-MI can be completed in same system, which decreases the system complexity. The sound velocity distribution is reconstructed with the ART so that the propagation time of the magnetoacoustic signals in the heterogeneous tissue is corrected. And then, the sound source image is reconstructed based on the time reversal method from new sound pressure data. Both numerical simulations and phantom experiments are established to validate the proposed method. Compared with the results without consideration of the variation on acoustic speed, sound sources reconstructed by our method are more consistent with the model in terms of size and shape. The novel algorithm can be used to reconstruct the high-accuracy image of MAT-MI sound source in the sound velocity inhomogeneous media. In addition, this method is applicable to scenarios that the prior knowledge of the imaging targets is unknown. The signal acquisition time of MAT-MI in acoustically heterogeneity media is greatly reduced due to the introduction of ring transducer array into the imaging system. Therefore, our method will promote the application of MAT-MI in noninvasive early diagnosis of tumor for preclinical study.

Study of the Influence of the Temperature Field’s Nonuniformity on the Pressure Pulsations in the Inlet Duct Using the RANS/ILES Method

The paper is devoted to the RANS/ILES high-resolution method application for studying the influence of a nonuniformity of the inflow temperature field on the throttle characteristics of a supersonic mixed compression inlet, and the intensity and spectral characteristics of pressure pulsations in the inlet duct. Five cases of inflow parameters are investigated, three of which have a nonuniform temperature field. The sound pressure level distributions in the inlet duct and the pressure pulsation spectra at points on the inlet walls are obtained.

Analysis of the flow noises of the nuclear main pump caused by the high temperature liquid Sodium in the two-circuit main loop liquid Sodium pump system

The paper investigates the flow noises caused by the high temperature liquid Sodium in the nuclear main pump system. Three-dimensional unsteady CFD coupled sound field methods are exploited. Spectrum characteristics of sound source load are obtained. Directional sound pressure level distribution based on sound source load of rotor blades and guide vanes are presented and discussed. Distribution of sound pressure level of inlet and outlet pipes along the flow direction are also further discussed. Results indicate that with the increase of blade passing frequency, the amplitude of sound pressure level decreases. Response of sound field mainly depends on the load characteristics of rotor blades. Research results have remarkable significances for the analysis of flow noises in liquid Sodium pump systems.

Broadband underwater sound absorbing structure with gradient cavity shaped polyurethane composite array supported by carbon fiber honeycomb

A sound-absorbing periodically arrayed structure (SPAS) based on the combined effects of cavity resonance and impedance transition is designed. Different types of polyurethane composites are integrated to fabricate the sound-permeable layer, the gradient resonant cavity layer and the viscoelastic bottom layer. The carbon fiber honeycomb (CFH) is incorporated to the SPAS as a skeleton for better sound absorption performance under hydraulic pressure. The approximate multi-layered sound-absorption theory based on a modified transfer matrix method is adopted to predict the SPAS sound-absorption coefficient. The experimental sound-absorption coefficient of SPAS with CFH achieves 0.9 in the frequency range of 2400–10000 Hz under the hydraulic pressure of 1.5 MPa, which is promising for further practical application. The radial velocity, displacement and acoustic pressure distribution of SPAS were simulated to analyze the sound-absorption improvement in specific frequency points, showing that addition of CFH changes the sound field distribution in a positive sense.