bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical analysis on the acoustic well logging transducers with various fluid load
Authors: Chen Qiuying , Cong Jiansheng , Wang Xiuming , Zhang Hailan
Published: April 2012

It is numerically analyzed how the acoustic attributions of monopole well logging transducer change when excited in different fluid load media, such as water, silicone oil and mud with different components. The logging transducer is a radially polarized piezoelectric cylindrical tube with both ends shielded, being used as either transmitter or receiver. For the radially resonant mode of the transducer, the resonant frequency, transmitting voltage response and receiving sensitivity of the transducer are affected by the medium density and velocity. When the medium density is constant, the resonant frequency and the transmitting voltage response increase with the increasing of medium velocity, while the receiving sensitivity decrease with the increasing of medium velocity. When the medium velocity is constant, the resonant frequency decrease with the increasing of medium density, while the transmitting voltage response and receiving sensitivity increase with the increasing of medium density. For the given acoustic impedance, medium with different density and velocity have different effect on the transducer, which implies that the acoustic impedance of fluid load can't independently affect the acoustic attributions of transducer. The analysis results above have certain reference significance for the site operations of acoustic logging.
Performance analysis for acoustic well logging receivers
Authors: Cong Jiansheng , Chen Qiuying , Wei Qian , Wang Xiuming
Published: April 2012

The structure of acoustic logging receivers can change their performance directly. In this article, impedance characteristics and receiving sensitivities of three kinds of acoustic logging receivers were numerically analyzed with the finite element method. The modeling results showed that: The piezoelectric tube transducer in radial vibration mode had higher receiving sensitivity in the frequency range of 8-20 kHz with some ups and downs, while its sensitivity changed great below 5 kHz. The laminated circles transducer in bending vibration mode had higher sensitivity and better flatness below 4 kHz, but its sensitivity and flatness changed lower from 8 kHz to 20 kHz. The rectangular laminated piezoelectric transducer in the length stretching mode had better flatness below 20 kHz. In addition, acoustic well logging receivers in the future will have higher sensitivity, wider frequency bandwidth and smaller volume, which was pointed out in the article.
The application of compressive sensing in synthetic transmit aperture imaging
Authors: Lv Yi , Wu Wentao , Xiao Ling
Published: April 2012

Synthetic transmit aperture (STA) imaging requires huge data amount due to its demand for high image quality, thus this increases the need for high performance hardware and limits the flexibility of the post-processing stages. Compressive sensing (CS) theory shows that the signals can be reconstructed from an extremely smaller set of measurements than what is generally considered necessary by Nyquist/Shannon theorem. In this paper, the CS theory is applied to STA imaging by sparse representation of the image in k-space. This method is tested with Field II simulation and the result shows that the quality of image is maintained with reduced data size by the application of CS theory with reduced sampling rates.
Estimation of blood velocity vectors using two generalized beam signals
Authors: Xiao Ling , Meng Xiaohui , Wu Wentao
Published: April 2012

Traditional Doppler methods measure only the velocity component along the ultrasound beam direction, and a flow transverse to the beam is not displayed. The lack of information on the beam-flow angle creates an ambiguity that can lead to large errors in velocity magnitude estimates. Different triangle techniques have been proposed, which basically perform multiple measurements of the Doppler frequency shift originating from the same region. In this work, a generalized model is introduced for triangle and non-triangle techniques, in which two ultrasound beams with known relative orientation are directed toward the same vessel. The velocity vector can then be obtained under the condition, when the phase variations of the two beams are linear independence as the functions of the scatter's movement direction. A novel vector estimator is proposed under the framework of the model. It uses only real received signals and their Hilbert transformation and is simulated by Field II, showing suitable for implementation in steerable linear array transducers.
Novel concept of therapeutic array transducer element using coresonance between oscillations of hemispherical piezoceramic shell and water sphere
Authors: Otsu Kenji , Yoshizawa Shin , Umemura Shin-ichiro
Published: April 2012

For therapeutic array transducers, it is required to reduce the electrical impedance of their elements so that the transducer can produce high ultrasonic power at a relatively low drive voltage. For this purpose, a new concept of concave hemispherical piezoceramic transducer element using its breathing mode has been investigated. The vibrational behavior of such a transducer is theoretically, numerically, and experimentally analyzed. Both resonance frequencies of the breathing-mode oscillation of a piezoceramic spherical shell and the volume oscillation of a water sphere are not only inversely proportional to their diameters, but also very close to each other at the same diameter. Numerical simulation of the transducer element showed high acoustical coupling achieved by the coresonance between the piezoceramic and the water sphere half enclosed by the shell. To confirm the effect by the coresonance, simulation replacing water by virtual materials, having the same acoustic impedance as water but different longitudinal velocities, was performed. The electrical impedance curves of the concave shell were very sensitive to the longitudinal velocities of the virtual materials, whereas those of the convex shell remained unchanged, which strongly support the hypothesis. Experimental results with a prototype transducer element will also be discussed.
A three-dimensional orientation method for estimating a concave spherical array in phased array high intensity focused ultrasound
Authors: Wang Junlin , Wang Xiaodong , Yu Zhongde , Xiao Ling
Published: April 2012

The pseudo-inverse matrix method can be used to get complex excitation vector through the forward propagation operator from the surface of the array to the set of control points before the scheduled complex pressure at the control points is formed. The relative positions of the elements in the array should be estimated accurately since the elements are randomly placed with high-frequency and large-size. The high precision three-dimensional coordinates of elements are obtained by ways of comparing phase differences measured and calculated. The ideal distribution of focused sound field validates the precision of this way in which the measured phase differences are regarded as the initial phases of the elements.
Electrode configuration influences electrically evoked compound action potentials of guinea pig
Authors: Meng Li
Published: April 2012

The intracochlear electrode array of cochlear implants is used to electrically stimulate the residual hearing auditory nerve of profound sensorineural hearing loss. The present products used to implant possess configuration with the different contact style and different separation between the contacts. This study investigated the effects of electrode configuration on the auditory nerve compound action potentials in response to electric stimulation. We also investigated the channel interaction of the different electrode configuration. Adult guinea pigs were used in acute experimental sessions. We implanted three kinds of electrode array either (1) a narrow spacing banded array consisting of a tapered silicone elastomer carrier with a linear series of banding contacts; or (2) two wider spacing arrays consisting of a tapered silicone elastomer carrier with oval-shaped contacts. The electrically evoked compound action potential (ECAP) was recorded from the intracochlear. ECAP latency functions indicated that the electrode array with narrow spacing and banded contacts generated shorter latency than the electrode array with wider spacing and oval-shaped contacts. We also observed that the electrode array with banded contacts had greater ECAP amplitude than the electrode with oval-shaped contacts.
Design and implementation of the electronic system of phased array high intensity focused ultrasound
Authors: Wang Xiaodong
Published: April 2012

Phased array technology is the development direction of the high intensity focused ultrasound. In this paper, we will discuss the design and implementation of the electronic system of phased array high intensity focused ultrasound. The structure of the system is distributed, composed of PC and some controlling units, which communicate with CAN bus. Each unit receives data from the PC and controls the phase and amplitude of acoustic emission signals. Specifically, we will discuss some key technology of the electronic system, such as how to control the phase and amplitude of the emission signal, use the time reversal and pseudo-inverse matrix to get the phase of the emission signals.
Acoustical education in architectural engineering program at the University of Nebraska
Authors: Lau Siu-Kit , Wang Lily M.
Published: April 2012

An increasing number of schools are offering Architectural Engineering (AE) programs; currently there are 20 schools across the United States. However, only few of these AE programs include acoustics as a main option in their curricula. A comprehensive review of U.S. graduate programs in a report of “Technology for a Quieter America” by the United States National Academy of Engineering found that there is not sufficient training for students in acoustics in the U.S. This presentation will review the Nebraska Acoustics Group, housed within the AE program at the University of Nebraska which began in 1998. To cope with the needs, students could study acoustics within any of our five engineering degree programs (BSAE, MAE, MEng, MS, and PhD). There are currently two AE faculty out of 13 who focus in acoustics at Nebraska, and the program regularly offers at least six recurring acoustics courses. Descriptions of the acoustics courses, the research interests of the Nebraska Acoustics Group, and where our graduates are to date will be given. Specifically highlighted will be the theme of our acoustics group: to promote the advancement and science of architectural acoustics by closely tying our coursework and research to practice in the `real-world'.
Undergraduate acoustics education in Nanjing University
Authors: Zhang Dong , Qiu Xiaojun
Published: April 2012

The acoustics in the Department of Acoustic Science and Engineering, Nanjing University, has been evaluated as a state key subject for cultivating acoustic talents from undergraduate students to post-doctoral fellows. Our department prepares undergraduates for entry-level positions in the acoustic field and further education at the master's level. Our educational programs are organized around two overlapping areas: Acoustics and Acoustical signal processing. Core courses include fundamentals of acoustics, acoustic measurement, and acoustic transducer. A series of advanced undergraduate courses have also been developed to provide students with formal training in acoustics, including: electronic acoustics, ultrasonics, architectural acoustics, audio signal processing, active noise control, and etc. The goal of this program is to prepare students with both solid foundation in acoustic science and capabilities in acoustic engineering.
Beaming teching application: recording techniques for spatial xylophone sound rendering
Authors: Marković Miloš , Madsen Esben , Krarup Olesen Søren , Hoffmann Pablo , Hammershøi Dorte
Published: April 2012

BEAMING is a telepresence research project aiming at providing a multimodal interaction between two or more participants located at distant locations. One of the BEAMING applications allows a distant teacher to give a xylophone playing lecture to the students. Therefore, rendering of the xylophone played at student's location is required at teacher's site. This paper presents a comparison of different recording techniques for a spatial xylophone sound rendering. Directivity pattern of the xylophone was measured and spatial properties of the sound field created by a xylophone as a distributed sound source were analyzed. Xylophone recordings were performed using different microphone configurations: one and two-channel recording setups are implemented. Recordings were carried out in standard listening room and in an anechoic chamber. Differences between anechoic and reverberant xylophone sound for binaural synthesis are examined. One-channel recording approach with binaural synthesis for spatial xylophone sound rendering is proposed. One channel recording is processed to define multiple source positions for xylophone width representation. Binaural synthesis was used for the reproduction. This leads to spatial improvements mainly in terms of the Apparent Source Width (ASW). Rendered examples are subjectively evaluated in listening tests by comparing them with binaural recording.
Calibration aspects of binaural sound reproduction over insert earphones
Authors: Hoffmann Pablo , Markovic Milos , Krarup Olesen Søren , Madsen Esben , Hammershøi Dorte
Published: April 2012

Earphones are nowadays widely adopted for the reproduction of audio material in mobile multimedia and communication platforms, e.g. smartphones. Reproduction of high-quality spatial sound on such platforms can dramatically improve their applicability, and since two channels are always available in earphone-based reproduction, binaural reproduction can be applied directly. This paper is concerned with the theoretical and practical aspects relevant to the correct reproduction of binaural signals over insert earphones. To this purpose, a theoretical model originally developed to explain the acoustic transmission to and within the open ear canal is revisited [Mo/ller, Appl. Acoust., 36, 171-218 (1992)]. The model is modified accordingly in order to investigate the aspects of the transmission within the blocked ear canal that are significant to the calibration required to preserve the natural spatial cues that exist during normal hearing conditions, i.e. during an open-ear-canal situation. To evaluate the validity of the theoretical considerations outlined in this paper, measurements are conducted using an IEC711 occluded-ear simulator with a number of different types of insert earphones.
An assessment of the simulation and auralization quality of the Virtusound platform
Authors: Alarcão D. , Bento Coelho J. L.
Published: April 2012

The Virtusound platform was developed for real time room acoustics simulation and auralization through binaural technology. The calculation module uses an accelerated mirror image source method and a time-dependent radiosity method for the computation of the binaural room impulse responses. Informal tests have shown the system to be accurate and the rendered tri-dimensional sound to be quite realistic. However, a more comprehensive assessment was seen to be required in order to guarantee the quality of the platform. This paper presents therefore a first assessment on the capabilities of the Virtusound system in terms of the predicted objective parameters and in terms of the produced auralizations.
Identification and location of the distribution of elementary sources based on phase conjugation method
Authors: Li Ting , Li Sheng
Published: April 2012

Phase conjugation method can achieve the back propagation and adaptive focusing. It can be used for acoustic source localization. Localization of the distribution of elementary sources is discussed with the discrete phase conjugation planar arrays and the discrete phase conjugation sphere array numerically. Here, it is discussed how both of the shape of array and the distance between phase conjugation array and initial source can influence the spatial resolution. Three variants of phase conjugation arrays are studied: Phase conjugation array made of monopoles, dipoles, or both of them. Corresponding to the three variants, analysis is performed in terms of evanescent and propagative waves and an acoustic sink of the three variants, which absorbs the outgoing wave of the time-reverse wave, is also discussed. The interference pattern of the wave generated by the initial source and the time-reverse wave is used to identify the combination acoustic source.
Study on suppression of background noise using near-field acoustic holography with single layer microphone array
Authors: Lu Huancai , Song Yulai
Published: April 2012

A study was carried out to suppress background noise in non-free field generated by target sound source and noise source based on near-field acoustic holography with single layer microphone array. The acoustic pressures in non-free field are expressed as superposition of incoming and outgoing spherical wave functions. The coefficients of those spherical wave functions are determined based on the principle of Helmholtz Equation Least-Squares (HELS) method. The sound field was then separated once both the coefficients of incoming and outgoing spherical wave functions obtained. The error incurred in the process of inverse calculation was minimized via least-squares method as utilized in HELS. Numerical simulations were conducted to validate the approach, in which the non-free field was generated by different sound sources with analytical solutions, such as dilating sphere, oscillating sphere, and vibrating simply-supported thin plate. Those sound sources perform as target source and background noise source alternatively. Experiments in non-free field generated by omnidirectional speaker and JBL speaker was also conducted to examine the validity and accuracy of the approach. The results from both simulations and experiments show that the approach is capable to reconstruct the target sources and suppress the background noise with satisfactory accuracy in low frequency range.
Sound source localization based on laser measurement of air vibration
Authors: Cui TianHao , Cheng XiaoBin , Sun HongLing
Published: April 2012

This paper proposes a novel approach to locate sound source using laser measurement by testing multi-point air vibrations simultaneously. In this approach, a laser beam is generated in a free space and backscattered by various scattering points. All the backscattering is assumed to take place simultaneously since light travels much faster than sound. The backscattering time intervals can be measured and the locations of scattering points in the space can be calculated. This method could be regarded as a substitute of a receiving array with n- sound transducers, based on which, an algorithm is presented to locate the sound source. Experimental results show that the proposed method exhibits a high locating precision.
Numerical study on reconstruction of acoustic pressure field based on near-field acoustic holography with spherical array
Authors: Lu Huancai , Li Minzong
Published: April 2012

This paper presents the results of numerical study on reconstruction of acoustic pressure field based on near-field acoustic holography (NAH) with spherical array, while standoff distance, diameter of spherical array, number of microphones vary respectively. Two acoustic pressure fields are analytically generated by two monopole sound sources on the opposite sides of spherical array, and on one side of spherical array but apart at small distance. The accuracy of localization and identification of sound sources at different frequencies with different setup of reconstruction parameters was examined by comparison of the reconstructed results to the analytical results. The simulation of reconstruction of acoustic pressure field based on NAH with spherical array may provide guideline for application of NAH with spherical array in engineering.
Near-field acoustic holography of acoustic radiation from structures
Authors: Mao Rongfu , Chen Zhimin , Zhu Haichao
Published: April 2012

There are some difficulties for conventional Near-field Acoustic Holography (NAH) to analyze acoustic radiation from a large scale structure. To solve the problem, a method for NAH of large scale structures was presented. In the method, the normal velocities or sound pressure at a few points on the surface of the structure are measured by transducers, and that at other position on the surface of the structure are calculated by means of the radiation mode theory, then the radiated acoustic field may be analyzed by NAH. Since complex coupling terms no longer appear in the radiation modes, and only a few orders of modes are required to describe the acoustic field at low-to-mid frequencies, the accuracy of NAH analysis may be ensured. Moreover, according to the nesting property of radiation modes, the radiation modes at other frequencies can be replaced by that at maximum frequency, consequently the calculating procedure may be simplified and the calculating speed quicken. Finally, NAH analysis of acoustic radiation from large scale structures was illustrated using a 1m×1m simply supported steel plate. The results show that the radiated acoustic field can be reconstructed accurately under the circumstances of a few measurement points.
To observe and understand the basaltic eruptions with infrasound
Authors: Dupont Aurélien
Published: April 2012

The frequent eruptions of Piton de la Fournaise volcano (Reunion island) release an important quantity of magmatic gas into the atmosphere and generates infrasonic airwaves. The series of volcanic noise recorded, in the near field, on a microbarometer between 1992 and 2008 bring new constraints on the functioning of the eruptions. The detection and the modelling of the waveforms associated to the overpressurized explosions of gas bubbles leads to conceive the volcanic eruption as a puzzle game. The elementary pieces of the game, the eruptive regimes, are characterized and interpreted in the framework of a two-phase flow. The eruptive gas flow is also quantified. The main flow regime is the Strombolian activity where the infrasound signature come from the slug flow bursting. The tracking of the main source of noise, during the eruptions, shows that the size of the gas pockets which are maximum in the starting stage of the eruption, what corresponds to the Lava Fountain regime, constantly decrease until to disappear with the eruption end: the gas volume fraction constantly decrease in the volcanic conduit during an basaltic eruption. The quantitative analysis of the noise produced by the gas flow allows not only to understand a natural system as complex as a volcano but allows also to better monitor it.
Changes in oto-acoustic emissions after exposure to live music
Authors: Ordoñez Rodrigo , Hammershøi Dorte , Voetmann Jan
Published: April 2012

Distortion Product Oto-acoustic Emissions (DPOAE) and Transient Evoked Oto-acoustic Emissions (TEOAE) were measured in subjects before and after attendance to live music. The changes measured were compared to the exposure levels measured at the position of the subject. The main objectives of this experiment were two fold: 1) to assess the validity of the proposed measurement protocol to measure changes in DPOAE and TEOAE after a concert; 2) to test the reliability of the oto-acoustic emission measurement system under field conditions; Initial results shows that it is possible to measure changes in hearing after exposures of relative short duration (<1.5 hours). There are large individual differences both in sound exposure levels as well as in the changes on oto-acoustic emissions produced by similar exposures. Current results will be presented.
The influence of ambient noise and headphone style on listening volume using a personal stereo system
Authors: Lu Shih-Yi , Lin Kuei-Yi , Chen Chiou-Jong
Published: April 2012

It is well known that exposure to excessive noise for long durations can cause a significant noise-induced hearing loss (NIHL). Although most research has focused on occupational sources of NIHL, there is growing concern about the potential damage caused by non-occupational noise exposure such as that from portable stereo system headphones. The purpose of current study was to measure the sound level generated by headphones of portable stereo system, and provide hearing conservation guidelines. Using a B&K Torso and a personal computer, output sound levels across volume control set by thirty participants were measured from headphone driven by music samples of five different genres. Three different styles of headphones (in-ear, circum-aural, supra-aural) were used to determine if styles of headphone influence sound level inside of ears. The study results suggested that the supra-aural headphone used by listener in noisy environment shall set a higher volume, in a result of a larger sound level in eardrum. The authors would like to thank the Institute of Occupational Safety and Health of Taiwan for the support that made the completion of this work possible.
Sound transmission through stiffened plates
Authors: Ou Dayi , Mak Cheuk Ming
Published: April 2012

It is known that proper stiffening treatments may improve the sound insulation of plate-like structures. In this study, the sound transmission loss (STL) of a thin plate with stiffening treatments is investigated using a coupled finite element and boundary element method. A stiffened-plate element used in this method allows the plate to have arbitrary elastic boundary conditions and arbitrarily located stiffeners. Numerical studies of the effects of various stiffening conditions on the STL of a window are carried out. The boundary condition of the window lies somewhere between clamped and simply supported. The results can be used to guide the design of windows with better sound insulation performance.
Isolation of structure-borne noise in buildings from exterior sources
Authors: Wilson George Paul
Published: April 2012

The increasing frequency of construction of new performance, residential and other noise sensitive facilities in locations with high amplitudes of ground-borne noise has required development of effective building isolation design configurations to reduce to acceptable values the structure-borne noise transmitted into the buildings from the foundation. Isolating a large building such as a concert hall or multi-story residence necessarily requires structurally separating the isolated building, or isolated parts of the building, from the foundation. The structural support is then provided by resilient bearings that must properly support the building gravity load, provide a controlled seismic restraint and structural stability, and provide the noise reduction required. The goal of this presentation is to demonstrate that the technology and materials now exist to allow placement of any large noise sensitive building, either a performance facility or a residential building, in any location where it is subject to ground-borne vibration and noise that would normally cause intrusion and be incompatible with the intended occupancy. The development of the gravity load support bearings and the preloaded seismic restraint rubber bearing concepts are presented along with examples of successful applications.
Vibration isolation for concert hall next to busy street
Authors: Phillips James
Published: April 2012

A new, world-class performing arts center is currently being developed in a metropolitan center in the United States. The center will include two grand performance theaters. One of these theaters will be located close to a busy surface street. Vibration measurements conducted at the undeveloped site indicated that groundborne noise from street traffic would be audible within the completed theater unless measures were incorporated into the design to reduce vibration transmitted from the street to the interior of the theater. This will be achieved by structurally separating the performance area of the theater from the surrounding structure by supporting the theater on custom designed, resilient bearing pads. This paper discusses the vibration measurements taken, the projections of groundborne noise and the vibration mitigation measures that were incorporated into the structural design of the theater building to reduce groundborne noise to meet the project design criteria for background noise.
Acoustical performance assessment of Swiss low-noise road surface solutions in urban areas
Authors: Bühlmann Erik , Ziegler Toni
Published: April 2012

Recently Switzerland has experienced a new momentum in the construction of low-noise road surfaces in order to combat traffic noise in urban areas. Various regions have taken action and developed individual approaches to reduce traffic noise at the source. As a result, new requirements on the acoustical properties or on the void content of road surfaces were imposed, leading to the development of new products. The present work aims at both summarizing and cross comparing the acoustical performance of these products as well as analyzing the data produced to understand how the noise reduction was achieved. A large number of road surfaces (50 thin-layer asphalts, 30 SMA-like surfaces with increased void content) were therefore subjected to acoustical property monitoring using the CPX (close proximity) method. The acoustical performance of these road surfaces was quantified and evaluated in respect to AC and SMA surfaces, commonly used in urban areas in Switzerland and elsewhere in Europe. An approach was developed where measurement data of surface texture, airflow resistance and sound absorption, combined with SPERoN modeling (a tyre/road surface contact model) was included in the analyses. This approach provided an evaluation of the contribution of isolated factors to the overall noise reduction.
Two decades of noise control engineering and implementation for the Mass Transit Railway Corporation Ltd
Authors: Frommer Glenn
Published: April 2012

Hong Kong relies on electrically powered railways as the backbone of its mass transit. With 84 heavy rail stations and 218 route length, more than 4.3 million out of Hong Kong's 7 million residents use the Mass Transit Railway (MTR) each working day. Hong Kong is also one of the most densely populated cities in the world. The density of the city, the large number of high-rise residential developments and the city's reliance on railways poses unique challenges for the railway noise control engineer when considering airborne noise, ground-borne noise, building services, speech intelligibility and noise within compartments. Starting with the design development of the Airport Railway, noise control has been successfully applied to all new railway lines and stations since 1992. Though cutting edge at that time, the methods are now standard for railway noise control throughout the region. This paper will provide an overview of the strategies and proven outcomes. A read across to operating railway noise will also be presented. A `How – to' guideline will also be presented and the issue of noise as energy inefficiency will be discussed.
A comparative study of high-speed train noise prediction models
Authors: Yanjie Guo , Junhai Liang , Dongzhen Wang , Jianmin Ge
Published: April 2012

The present train noise prediction model in Chinese standards (HJ 453-2008 and HJ 2.4-2009) is only aimed for conventional train. Aerodynamic/rolling noise contribution of high-speed train noise are different from those of conventional train noise, thus, the Chinese prediction model might not be adaptable for the prediction of high-speed train noise. The aim of this paper is to discuss the noise prediction models of high-speed train above 300 km/h. Based on the comparative analysis of different models, our work mainly focus on noise source identification. Firstly the sound pressure level distribution on the surface of high-speed train body is investigated. In order to overcome the shortage of single line source, the noise source is divided into three line sources of different heights parallel to each other according to the energy distribution of sound source. Then sound pressure level generated by the three line sources at the receiving point is calculated separately. Finally the predicting outcomes are compared with measured results to verify the reliability of the model.
The relationship between structural vibration and noise of railway vehicles
Authors: Lv Gong , Liang Junhai , Liu Jinzhu , Ge Jianmin
Published: April 2012

With the rapid development of China's rail-vehicles industry, the property of the interior noise of the vehicles has become an important indicator of its quality. With the increasing speed of rail vehicles recent years, the airborne noise and the structural acoustics generated during the operation have had a great impact on the sound field inside the vehicle. In order to solve this problem, through the analysis of the noise and vibration produced during its operation, a rail vehicle sample is taken as the object of the study. Together with the basic principles of acoustics, the relationship between internal noise and the structural vibration and also the transmitting patterns of the structural vibration can be researched, so that it could provide a reference for the reduction of vibration and noise.
Acoustical device using helmholtz resonator for the high-speed train noise barrier
Authors: Koh Hyo-In , Cho Jun-Ho , Park Joon-Hyuk
Published: April 2012

This study is primarily aimed at developing a measure to overcome the limited shielding performance of the noise barriers for the high-speed train. Up to the train speed of 300km/h and more the noise incidence angle and the source height change due to the pronounced aerodynamic noise source parts located at the higher positions compared to the height of the conventional rolling noise source. By means of the experimental analysis on the sound radiation characteristics and the sound pressure distribution around the noise barrier, a prototype of an acoustical attachment is porduced based on the analytical model calculation and numerical analysis. The principle of the Helmholtz resonator is used to optimize the acoustical impedance on the surface of the upper dege of the noise barrier. Using the model it was possible to find an appropriate acoustical property for the impedance according to the target frequency,sound incidence angle relative to the barrier and the receiver position. In this paper the results of the experiment in an anechic room and from the out door experiment are shown and discussed.
The value of quiet areas in providing respite from traffic noise
Authors: Bristow Abigail L , Rowcroft Petrina , Shields Paul , Woodin Stuart
Published: April 2012

Prolonged exposure to unacceptable levels of noise is associated with a wide range of adverse impacts on human health, public amenity, productivity and ecosystems. As transport demand and development increases there is an associated reduction in the availability of areas that are perceived to be quiet or tranquil. The beneficial effects of access to quiet areas are not well understood. Critically there is a dearth of evidence on the value of benefits derived from quiet or green areas that offer a respite from traffic noise. Here we review the available evidence and propose a framework to assess the benefits that people derive from quiet areas and conversely the costs of loss of access to such areas. This requires a value to be placed on how residents, workers and visitors value publicly accessible quiet areas.
Optimisation of noise reducing device intrinsic performances
Authors: Leissing Thomas , Defrance Jérôme , Jean Philippe , Guigou-Carter Catherine , Clairbois Jean-Pierre
Published: April 2012

The work presented in this paper is part of the QUIESST European project, in which one of the objective is to perform optimisations of noise reducing devices. We present here optimisation results concerning the intrinsic performances of noise barriers. First the limits of these optimisations are determined: this concerns geometrical limitations as well as limitations on the number of materials. The intrinsic performances under interest are calculated using numerical simulations (the Boundary Element Method and the Transfer Matrix Method) in such a way that calculated values are as close as possible to quantities that one could measure using the CEN/TS 1793-4 -5 -6 standards. These simulations lead to reflection, transmission and diffraction performance values, which are expressed as a relative gain (or loss) to a reference noise barrier. The multi-objective optimisation strategy is then detailed and applied to nine coherent noise reducing device families. It is shown that using a specific set of parameters can largely improve the noise reducing device performances, and more importantly, that some selected set of parameters allow one to optimize several objectives simultaneously.
Nonlinear acoustic impedances of thermoacoustic stacks with different structures in resonance pipes
Authors: Xiao Shu-yu , Tao Sha , Qiu Mei-chen , Ge Huan , Fan Li , Zhang Shu-yi , Zhang Hui
Published: April 2012

The acoustic impedances of thermoacoustic stacks in the resonance pipes are measured by the method for measuring the nonlinear fluid resistances of porous materials. The thermoacoustic stacks with different structures of plate-type, pipe-type and meshed copper stacks are studied, in which the influences of the porosity and thickness of the stack and the operating frequency are evaluated experimentally. In the evaluations, the velocity variations in the stacks are neglected, so the thicknesses of the stacks must be much shorter than the acoustic wavelengths in the resonance pipe. The measured results show that the resistance of the stack keeps constant when the acoustic pressure level is low, but it increases rapidly with the tendency of quadratic function when the acoustic pressure level increases more than about 130 dB. Furthermore, both the linear and nonlinear acoustic resistances of the stacks increase with the thicknesses, while decrease with the increase of the porosity and/or the operating frequency. Finally, it is believed that the results of the influences of the structures and parameters of stacks on the acoustic impedances can be used in the nonlinear model of the thermoacoustic refrigerator.
Study of the acoustic impedance characteristics of linear alternator used in thermoacoustic generator
Authors: Zhang Jianwei , Li Zhengyu , Li Qing
Published: April 2012

A thermoacoustic generator is a long-life, high efficient generator, it is composed of thermoacoustic heat engine and linear alternator. As a resonance system, the acoustic impedance match between both of them greatly influences the whole system's performance. In order to test the acoustic characteristics of the linear alternator, an experimental system was set up in TIPC. In this system, the displacement of alternator's piston and the pressure in the generator were measured. Correlation arithmetic was used to analyze the impedance characteristics of the linear alternator at several mean pressures. The analysis let us know the characteristics, which the linear alternator would be in the whole machine. It could be used to design the thermoacoustic generator. Some results were attained. They showed the experimental system could effectively work. The design of thermoacoustic generator has benefited from it. The authors gratefully acknowledge the Natural Science Foundation of China (Grant No. 10804114).
Oscillation of sound wave in the straight-tube type miniature thermoacoustic system with closed-closed ends
Authors: Shibata Kenji , Sakamoto Shin-ichi , Kuroda Kentaro , Nakano Yosuke , Onaka Takeshi , Watanabe Yoshiaki
Published: April 2012

Downsizing of thermoacoustic system is discussed in order to be applied to the electronic equipments. In our previous studies for the miniature thermoacoustic system, the stable oscillation is successfully realized on the straight-tube with opened-closed ends type although the inner working fluid cannot be shut in. To realize the working fluid be shut in the tube and keeping the stable oscillation, a new system is combined of two tubes with different cross-sectional area. The large sized system is applied instead of the small sized one because of the measurement difficulty. As the results, it was confirmed that the efficiency of the energy conversion was improved by using the system which combines two kinds of tubes with different cross-section tube. The reason of the efficiency improvement was estimated that the resonance became to be strong by the overlap of two kinds of resonances. This estimation was confirmed by changing the ratio of length of connecting tubes with different cross-section. The efficiency of the energy conversion was improved by controlling of the acoustic field. Those were realized by connecting of two tubes with different cross-sectional area.
Investigation on streaming sources in thermoacoustic prime mover
Authors: Paridaens Richard , Kouidri Smaïne , Jebali Jerbi Fathi
Published: April 2012

Thermoacoustic devices either prime mover, heat engines or refrigerators are not known for their high efficiency. Even though these systems have many advantages regarding environmental constraints, they are not yet used in the industrial applications. Energy conversion efficiency improvement of thermoacoustic systems is now in the priority of the thermoacoustic community. One of the reasons of the relative low efficiencies is in the physical understanding which is not well achieved. The appearance of steady mass flow of second order usually called streaming and superimposed to the oscillating flow in these systems is shown as an important dissipating energy phenomenon. From energy consideration and despite their low level, this DC flow involves heat transfer to the wall which is undesirable loss mechanism. This phenomenon which is a quite old topic is still widely investigated experimentally and theoretically. The design, construction and performance measurements of the traveling wave thermoacoustic engine will be presented and discussed. A non-linear acoustic approach has been developed in order to determine the contribution of the different sources of streaming generation. The purpose is to emphasize on the physical interpretation of each source.
Low temperature drive of a straight tube thermoacoustic system filled with mixture gases by using numerical calculation
Authors: Nakano Yosuke , Sakamoto Shin-ichi , Kuroda Kentaro , Shibata Kenji , Tsuchiya Takao , Watanabe Yoshiaki
Published: April 2012

As the temperature ratio of the both ends of the stack increases gradually and reaches a critical value, sound waves begin to oscillate. This temperature ratio is called the onset temperature ratio. The thermoacoustic systems can use waste heat effectively, and are applied as electrical generation and cooling systems. However, the required temperature to drive the current thermoacoustic systems is higher than the temperature of waste heat, and energy conversion efficiency of the systems is just only a few percent. In order to use of the systems effectively, these need to be improved. The onset temperature ratio and energy conversion efficiency are dependent on the geometry of the systems and working fluids. In this report, it is focused on the gas in the systems, and the mixture gas of argon and helium was used as working fluids. The influence of the onset temperature ratio and energy conversion efficiency was investigated, when the mixture ratio was changed. These are calculated by using the linear stability theory and a transfer matrix method. As a result, the mixture ratios which give the minimum onset temperature ratio and the maximum energy conversion efficiency have been calculated.
Real-time measure system of linear alternator efficiency in Thermoacoustic electricity generator
Authors: Li Zhengyu , Zhang Jianwei , Zhou Gang , Hu Zhongjun , Li Qing
Published: April 2012

Thermoacoustic electricity generator could convert heat to electric power. It is composed of thermoacoustic engine and linear alternator. In TIPC, a traveling wave thermoacoustic electricity generator had been built and tested. Long resonator was replaced by linear generator in the thermoacoustic electricity generator. There were mechanical impedance, acoustic impedance and electric impedance. Only adjustment parameter was electric load when the generator ran. Electric load could affect the acoustic impedance of linear alternator, which was close related with efficiency from acoustic power to electric power. In order to optimize the electric load in real time, a kind of on-line measure method was supposed and tested. Volume flow rate and pressure were measured by resistance strain gauge and piezo-electric pressure sensor respectively. Correlation arithmetic was used to evaluate the acoustic power. On-line analysis of acoustic power and electric power made it possible to measure efficiency. Some tests were done to verify this technology. The improvement of electric power has benefited from the technology. The authors gratefully acknowledge the Natural Science Foundation of China (Grant No. 10804114).
Effect of source-motion and self-motion on the resetting of auditory scene analysis
Authors: Kondo Hirohito , Pressnitzer Daniel , Toshima Iwaki , Kashino Makio
Published: April 2012

Auditory scene analysis needs to parse the incoming flow of acoustic information into perceptual streams, such as distinct musical melodies or sentences from a single talker. Previous studies have demonstrated that the formation of auditory streams is not instantaneous: rather, streaming builds up over time and can be reset by sudden changes in the acoustics of the scene. The present study examined the effect of changes induced by voluntary head motion on streaming. A telepresence robot in a virtual-reality setup was used to disentangle all potential consequences of head motion: changes in acoustic cues at the ears, changes in apparent sound location, and changes in motor processes. The results showed that self-motion induced resetting of auditory streaming. An additive model analysis further revealed that resetting was largely influenced by acoustic cues and apparent sound location rather than by non-auditory factors related to head motion. Thus, low-level changes in sensory cues can affect perceptual organization, even though those changes are fully accounted for by self-motion of the listener. It is suggested that our results reflect a widely distributed neural architecture for the formation of auditory streams.
Using low-frequency threshold interaural time differences to test models of binaural hearing
Authors: Qu Tianshu , Hartmann William
Published: April 2012

All models for detecting an interaural time difference (ITD) begin with model cross-correlator cells. Models differ in their inputs (excitatory/inhibitory) and in the distribution of cells with respect to interaural delay and frequency. For instance, the Jeffress model postulates a broad distribution on delay. Also, alternative binaural displays are based on different moments of the cross-correlation. For instance, the centroid is based on the first moment. The different models predict different frequency dependences of the threshold ITD in the limit of low frequency. Limiting behavior was computed for the various models using different assumptions about the frequency dependence of the synchrony of inputs to cross-correlator cells and about the sharpness of the rate-ITD function from the cells. The results were compared with the measured low-frequency functional behavior of ITD thresholds for four human listeners, which ranged from ƒ-0.8 to ƒ-1.4. These measured exponents disagree with predictions from some combinations of models. In particular, the popular centroid display within the Jeffress model tends to lead to slopes that are steeper than observed experimentally. [Work supported by the National Natural Science Foundation of China grant 61175043 and the Air Force Office of Scientific Research grant 11NL002.]