bluuebunny/crossref_metadata_2025 huggingface dataset:
Prediction and measurement of acoustical property for natural fiber reinforced composite laminates
Authors: Yang Weidong , Li Yan , Pan Yongdong
Published: April 2012

Owing to the advantages of low density, low cost, easy availability and biodegradability, natural fibers are promising for industrial use in fiber-reinforced composite materials. Porous structures of natural fibers greatly contribute to the excellent sound absorption properties and multilayered composite panels also possess good sound insulation. Natural fiber reinforced composite (NFRC) laminates were manufactured in view of the process requirements of industrial production. Acoustic properties of NFRC, such as absorption coefficient, transmission coefficient and transmission loss, were measured by transfer function method in four-microphone impedance tube. Moreover, a theoretical model of multilayer material system of NFRC was proposed and the predicted results calculated by transfer matrix method are consistent with experimental measurement. This model can be used to predict acoustic properties of multilayered laminate system of NFRC.
Sound transmission through a double panel structure jointed with rubber isolators
Authors: Qian Zhongchang , Chang Daoqing , Liu Bilong
Published: April 2012

Sound transmission through an aircraft sidewall structure is investigated theoretically and experimentally in this paper. The studied configuration is composed of double-leaf lightweight partitions jointed with discrete placed rubber isolators. The effects of isolator stiffness, damping and spacing on sound transmission loss are calculated and tested. The influence of acoustic absorption treatment filled in the cavity is also included for a comparison. Furthermore, two methods which refers to space-harmonic and modal superposition expansions are employed for infinite and finite dimensions. At last, some approaches for sound transmission loss optimization are proposed.
Civil aircraft cabin noise resource acoustic characteristic and transmission path analysis
Authors: Shi Qian
Published: April 2012

Typically, there are mainly 4 different noise resources critical to cabin +F1184noise: auxiliary power unit (APU) noise, environment control system (ECS) noise, engine noise and turbulent boundary layer (TBL) noise. Because of the different acoustic characteristic and transmission path for each resource, their impacts to cabin noise level are not the similar. A vibration and noise test under ground and flight status of an in-service civil aircraft was conducted. Based on the test results, comparing the data under different test status, the acoustic characteristic and transmission path are analyzed for the 4 noise resources in this paper, including distribution characteristic, spectrum characteristic and transmission path. APU noise mainly affects the rear fuselage, ECS noise transmits by ducts, engine noise and TBL noise transmit through side panel.
The study on sonic response analysis method for civil aircraft structure
Authors: Wang Yu , Zhang Jiazhen , Zheng Xiaoling , Liang Jun
Published: April 2012

Sonic fatigue problem is one of the important terms of civil aircraft airworthiness examination. In this paper, two different engineering analysis methods are employed to study the sonic response characteristics of a kind of typical commercial aircraft structure (skin-string-frame structure). Whereafter the sonic response experiment for this structure is carried out, and the resonance frequency and root mean square (RMS) stress are measured. According to the comparison of engineering analysis results and experimental results, the analysis error and effectiveness of these two methods are studied. The resonance frequency analysis results for both methods are in good agreement with experimental results, and the prediction results of RMS stress are also acceptable in engineering.
Acoustic wavefront tracing in range-dependent ocean
Authors: Godin Oleg A. , Zabotin Nikolay A.
Published: April 2012

It has been established experimentally and confirmed by numerical simulations that early arrivals of acoustic waves at long-range propagation in a deep ocean are stable and identifiable despite strong perturbations of the ray paths due to sound-speed fluctuations primarily induced by internal gravity waves. It is wavefronts rather than rays that are typically observed in underwater acoustic experiments. Wavefronts are much more stable with respect to environmental perturbations than individual rays, which form the wavefronts. The relative stability of the wavefronts takes place because scattering of the end points of rays resulting from weak environmental perturbations occurs primarily along wavefronts of the unperturbed wave with the same travel time [O. A. Godin, J. Acoust. Soc. Am. 122, 3353–3363 (2007)]. When wavefronts are much more stable than rays, the traditional approach, which relies on ray tracing to determine wavefronts' position, may be counterproductive and sometimes misleading, especially for highly structured environments such as the ocean with internal waves and “spice.” This paper presents an efficient numerical technique for modeling acoustic wavefronts and timefronts in range-dependent ocean without solving ray equations. The acoustic wavefront tracing code has been benchmarked using analytic solutions of the eikonal equation. [Work supported by ONR.]
Acoustic propagation modeling in environments which induce horizontal refraction and mode coupling
Authors: Ballard Megan
Published: April 2012

In typical applications of modeling underwater sound propagation, three-dimensional effects are assumed to be relatively weak and two-dimensional models are applied on a vertical plane to predict acoustic signals. However, this assumption breaks down for many shallow-water environments. For example, evidence of horizontal refraction has been documented in the context of nonlinear internal waves and sloping bathymetry. In this work, three-dimensional effects are modeled using a coupled-mode technique which includes the effects of out-of-plane scattering. Several examples of propagation in three-dimensional environments will be presented. A decomposition of the field into modal amplitudes will be used to identify features in the environment responsible for the observed effects on the acoustic field. [Work supported by ONR]
Analysis of acoustic fluctuation of the different tracks by the internal waves
Authors: Li Fan , Guo Xinyi , Hu Tao , Ma Li , Chen Yaoming
Published: April 2012

Internal waves in shallow-water cause sound speed profiles variations and acoustic transmission abnormity. The acoustic data show arrival time variations and mode coupling phenomena. The 2009 experiment collected high quality environmental and acoustic data and were used to analyse the effect of internal waves on the acoustic transmission. One notable feature of the experiment is that internal crossed two tracks at different incidence angles. The paper compare acoustic fluctuation character at two different tracks and use mode filter method to investigate the mode coupling caused by internal wave. The correspondence between data and simulation results show that the alternate of mode 2 and mode 1 were observed at the track which is vertical with the internal wave direction. The alternate of Mode 3 and first two modes occur at the another track.
Passive measurement of lengthways transfer function in ocean waveguide using ambient noise
Authors: Guo Xinyi , Li Fan , Ma Li , Chen Yaoming
Published: April 2012

This paper introduces a function of correlation between two hydrophones, basing on the Kuperman-Ingenito ocean ambient noise model. There is a similarity in form between the correlation function and the transfer function in ocean waveguide from a point source to a receiver. Thus, the noise correlation function between two hydrophones in vertical location can extract actual transfer function, then the acoustics line arrival structure of propagation in lengthways waveguide can be analyzed. In this paper, the transfer function in lengthways ocean waveguide can be obtained from broadband ambient noise correlation function of vertical line array. There are some analyses about physical significance of noise interference basing on compared simulation and experience. This method can be used to research layered sea floor considering the arrival time structure of each propagation route.
Long range propagation modeling of offshore wind turbine noise using finite element and parabolic equation models
Authors: Kim Huikwan , Potty Gopu R. , Miller James H. , Smith Kevin B. , Dossot Georges
Published: April 2012

Noise generated by offshore wind turbines and support structures radiates and propagates through the air, water and sediment. Predicting noise levels around wind turbine structures at sea is required to estimate the effects of the noise on marine life. We used Finite Element (FE) and Parabolic Equation (PE) models to predict long range propagation of noise from the construction and operation of offshore wind turbines. FE analysis produced pressure outputs at short ranges were used as a starting field for a modified PE propagation model. Furthermore, we investigated the optimum range for the transition to PE modeling. The effects of various sediment types were also considered determining the pressure starting field. In FE analysis models, we implemented the axisymmetric elements and implicit dynamic analysis with pressure impact loading and vertical acceleration boundary conditions to simulate pile driving and operational noise radiation. We will present the PE long range pressure field outputs from the offshore pile driving and operation for a shallow water environment around Block Island, Rhode Island.
Environmentally robust time reversal processing based on multiple constraint method
Authors: Joo Jae Hoon , Kim Jea Soo , Cho Jung Hong , Moon Sang Taeck
Published: April 2012

Time-reversal processing (TRP) uses the signals from a probe source to refocus the signal at the probe source location by back-propagating the time-reversed version of the received signal. However, the performance of TRP can be degraded by the mismatches due to the non-static environment where propagation condition changes during the time between receiving a probe signal and back-propagating the time reversed signal. In this presentation, two methods for the environmentally robust TRP based on the multiple signal vectors with singular value decomposition and minimum variance with multiple constraint method has been numerically simulated and compared under the condition of mismatches. Multiple sound speed profile, probe source location and tilted array are used to make the TRP robust. The results show that the focal point using robust TRP is well maintained when compared to the conventional TRP. Both methods are efficient for the robustness of time varying environment.
Research on recognizing a cylindrical object using the 3-D formation from highlight and shadow of side scan sonar image
Authors: Lee Jieun , Shim Taebo , Kim Taejung , Hahn Jooyoung
Published: April 2012

There are many researches on recognizing and classifying a cylindrical object using side scan sonar images. In this paper we segment object, shadow of object and background of the images in order to extract the cylindrical object from the segmented object information and figure out whether it corresponds to the cylindrical object what we want to find. Shadow of cylindrical object estimated from 3-dimensional segmented space is compared with the shape of shadow got from morphological method. Many objects of different shape such as cylindrical, cylindrical object-likes and non- cylindrical objects are used as a background objects to simulate the objects are mixed with similar objects. Result shows that more than 90 % of the objects were recognized as objects in a comparably short time of order of 1 second.
Submerged target scattering: comparison of combined finite element/simplified acoustics models to data
Authors: Williams Kevin , Espana Aubrey , Kargl Steven , Zampolli Mario
Published: April 2012

The environment and the location of the target within that environment affect the scattering from elastic targets in ocean waveguides. Computational power is now realizable to compute the target scattering, in-situ, via finite elements. However, these calculations still require high cost computer facilities and in the end do not offer physical insight into processes involved. Here we compare two models, with different levels of simplification, to data acquired from an Aluminum target machined to replicate an Unexploded Ordnance (UXO). The first model treats the scattering using two-fluid Green's function propagators in combination with finite element calculations of the target scattering as placed within the waveguide. The second model uses free field, plane wave incidence, finite element results for the target scattering in conjunction with simple ray based propagation to account for the waveguide environment. The data/model comparisons are discussed in light of the physical insight they can help provide, the speed of the calculation and the level of fidelity they achieve. [Work supported by ONR and SERDP, USA].
Predicting the acoustic response of targets in an ocean environment based on modal analysis of finite element calculations
Authors: España Aubrey , Williams Kevin , Zampolli Mario , Marston Philip
Published: April 2012

Low frequency sound is a viable means for the detection of elastic targets in contact with the ocean floor. The incoming sound, with wavelengths on the order of the target dimensions, can excite resonant modes of the target leading to enhancements in the scattered field. A hybrid model has been developed to predict the acoustic scattering from cylinders, pipes and unexploded ordnance (UXO) in proud or buried configurations in the ocean sediment. The model exploits the symmetry by decomposing the 3-D problem into a sum of 2-D independent Fourier modal sub-problems. This hybrid modeling technique has been shown to agree well with experimental measurements conducted in a pond [A.L. España et al., J. Acoust. Soc. Am. 130, 2330 (2011)]. Presently, these hybrid model results are used to examine the target response on a mode-by-mode basis. A modal map is generated by keeping track of the number of dominant modes contributing to the bright features observed in the acoustic template. For features that are predominantly due to one or two modes, simple analytical models can be used to predict their evolution as a function of target/sensor geometry within the ocean waveguide. [Work supported by ONR and SERDP.]
A theoretical simulation to the arc expansion process in underwater discharge
Authors: Wang Yibo
Published: April 2012

A one-dimensional simulation to the arc expansion process in underwater discharge is carried out in this paper towards its final destination---the estimation of the acoustic output in the arc expansion process. Theoretical models for these four sub-processes which are strongly coupled in the arc expansion process, are built up. Based on these theoretical models, a simulation code is developed and the time-evolution data of some key parameters in the arc expansion process are simulated, from which the acoustic output is finally estimated.
Speech privacy at community pharmacies
Authors: Koyama Yumi , Hanyu Toshiki , Hoshi Kazuma
Published: April 2012

To identify practical ways to assess privacy protection at counseling area in community pharmacies, we conducted site-visit investigations at 84 community pharmacies including on 10 telephone interviews, and internet questionnaire survey on 160 patients. In the typical Japanese community pharmacies, space is small, the counseling area is open, and there are many patients who are waiting until their name is called. In that situation, busy and noisy and loose concentration, patients must try to accurately grasp medical information, and pharmacist are also working in the same situation. At the site-visits, we asked about aural or visual privacy issues and performed a psychological experiment to determine whether the patient-pharmacist conversation could be heard from the waiting seats for patients. At the internet questionnaire, we asked about counseling environment at community pharmacies. Responses to the site-visit investigation and internet questionnaire survey revealed that privacy-related problems were classified into 4 factors: physical environment (speech privacy), information sharing, pharmacist's social role, and a complex mechanism of the medical system. These factors appear to be interrelated, making it difficult to improve patient-centered care.
Aco(s)ustainability (Acoustics and Sustainability)—is a space truly functional for its intended use?
Authors: Butko Daniel , Randorff Jack
Published: April 2012

Numerous scientific studies defining acoustical values of common building materials and assemblies have been performed throughout history and then correlated to occupant health, productivity, and speech intelligibility within the defined space. Since occupant well-being should be a driving factor during design and construction phases, the effects of sound and noise should be considered an inherent component of sustainable design. The functionality of the inhabitable spaces for the intended purpose suddenly increases the scope of sustainability. Without knowledge of previous experiments or publications, various University of Oklahoma College of Architecture students were tasked with answering the following question: Is a space truly functional for the intended purpose? Various built environments were evaluated, basic SPLs and frequencies were documented, and the results were compared with published data for construction materials and methods including OSHA and ANSI regulations. Students were anonymously surveyed concerning acoustical conditions they experienced to define what they considered helpful and distracting conditions. This paper focuses on introducing architecture students to the intrinsic link between acoustics and sustainability, allowing an appreciation for both the art and science contributing to inhabitable space(s).
Brief review on micro-perforated sound absorbers
Authors: Nocke Christian , Hilge Catja , Scherrer Jean-Marc
Published: April 2012

The theory of microperforated panel sound-absorbing constructions has been introduced by D.-Y. Maa in 1975. Since then many variations of micro-perforated sound absorbing devices and materials have been introduced. Materials that have been used to be micro-perforated have been metal, wood, plastics and many others. Stretched sheets used as ceilings, wall coverings and other set-ups have been applied for more than 40 years. In 2001 a nearly invisible micro-perforation has been introduced to the stretched material making it highly sound absorptive. The classical set-up of a micro-perforated sound absorber consists of a micro-perforated panel in front of an air cavity. The sound absorption coefficient of these set-ups can easily calculated with a high accuracy according to the well-known approximation of D.-Y. Maa if all defining geometrical parameters (diameter of microperforation, distance between orifices, panel thickness and air cavity depth) are known. For other assemblies no closed calculation model exists so far. In this contribution measured sound absorption coefficients of various set-ups with micro-perforated materials as well as combinations with different porous materials will be presented.
Coupled mode analysis of thin micro-perforated panel absorbers
Authors: Maury Cedric , Bravo Teresa , Pinhede Cedric
Published: April 2012

The prediction of the isolating properties of lightweight Micro Perforated Panels (MPP) is a subject that has been intensively studied due to their important applications in a wide range of areas such as building acoustics and the aeronautic, astronautic and automotive industries. MPPs have been mostly considered as rigid structures, accounting only for inertia and neglecting any vibrating effects. However, simulation and experimental studies on thin MPPs have found that the absorbing performance can experience variations in the low frequency range from the results expected assuming a rigid structure. The work presented here is a theoretical and experimental study on the influence of panel vibrations on the sound absorption properties of thin MPP absorbers. Measurements show that the absorption performance generates extra absorption peaks or dips that cannot be understood assuming a rigid MPP. A theoretical model is established that exactly accounts for structural-acoustic interaction between the micro-perforated panel and the backing cavity without restriction on the absorber cross-sectional shape or on the panel boundary conditions. This model is verified experimentally against impedance tube measurements and laser vibrometric scans of the cavity-backed panel response. The effect of micro-perforations on panel-cavity or hole-cavity resonances is revealed through coupled mode analysis.
Hybrid sound absorbers combining micro-perforated panels with conventional absorption mechanisms
Authors: Buret Marc , Iu King Kwong
Published: April 2012

Combination of microperforated panels with optimised efficiency in the low frequency range and other sound absorption systems, that provide performance in the mid and high frequencies, is presented for two sound absorber designs. In the first instance, proprietary fabric cover and fibrous absorption have been used to extend the performance range of discrete microperforated absorber units by optimising sound absorption by the edge of the units. The second development consists of conventional Helmholtz resonator perforated panels that have been customised using a micro-perforated panel in view to tune and enhance the low frequency performance. Results of testing conducted in a reverberation chamber are presented.
Modeling vibro-acoustics behaviour of micro-perforated structures using patch transfer function approach
Authors: Guyader J.-L. , Maxit L. , Cheng L.
Published: April 2012

Micro-perforated structures with a backing cavity is a device for providing efficient noise absorption. In a practical and industrial setting, the efficiency of Micro-Perforated Structure (MPS) may be influenced by the vibro-acoustic behavior of the surrounding systems, the shape of the micro-perforated structure as well as different kinds of excitation. In this paper, the Patch Transfer Functions (PTF) approach is proposed to model the MPS behaviour in such Complex Vibro-Acoustic Environment The PTF method is a substructuring approach which allows assembling different vibro-acoustic subsystems coupled through surfaces. The proposed PTF formulation of the MPS is capable of taking the micro-perforations and the flexibility of the structures into account and allows easy prediction of the efficiency of a MPS in a practical vibro-acoustic environment. In order to validate the present approach, PTF results are compared with experimental measurements.
A study on the sound insulation performance of obliqe micro-perforated absorbers in shading louver
Authors: Wen-Sung Chu , Yu-Che Wang , Rong-Ping Lai
Published: April 2012

Generally shading louver are used for shading and natural ventilation, but in noisy urban area, sound insulation is necessary, in the trend of green building design, shading natural ventilation and insulation are taken the same weighting, but it is contradictory, meanwhile, the performance of water proof also required in louvre. In study, we try to use oblique micro-perforated for shading louvre, and reach it sound insulation. Acoustics louvres normally use in silencers for Air conditioning duct, it is composited by Perforated plate any glass fiber, for the water proof season, we use oblique micro-perforated instead of glass fiber, and design and some influence factors those are specified of form, blade length, blade width, blade angle and air gap and blade is composed of an infill of sound absorption material enclosed by perforated sheet material, sound insulation of an acoustic louvres generally is not high, particularly at low frequencies. We designed several type of the louver and test it acoustical performance, and discussed it is low, median. high frequencies. Finally, we calculate it's Rw by ISO 140, by the way, we also asses it ventilation, lighting, shading, affect, it is very important in green building.
A broad band dolphin mimetic sonar—inspiration and modification from the nature
Authors: Akamatsu Tomonari , Imaizumi Tomohito , Abe Koki , Nishimori Yasushi , Wang Young , Matsuo Ikuo , Ito Masanori
Published: April 2012

Broadband techniques are getting popular for underwater sensing methods because of its high spatial resolution and target discrimination abilities. We have been developing a broadband split beam system to locate and identify each species in the ocean. Our system initially learned from dolphins and then modified architecture appropriately. For example, biological sonar sound was effective for the short range sensing to locate individual target, chirp sound provided clear target image for the long range up to 200 m. Multi angle scanning of a target was proved to be essential for the species discrimination in our system. It was just like a finless porpoises rolled their body possibly to enlarge sensing volume and change beam incident angles to a target. Unlike dolphins, the split beam system was not able to change transmitting beam directions. The sound incident angle to a fish was calculated using the body movement vector and the position of a target fish in the beam. Reconstruction of target strength spectrum according to the incident angle provided significant difference of species between jack mackerel and chub mackerel that has not been possible by conventional active sonar systems.
Localization of the moving object by echolocation
Authors: Matsuo Ikuo
Published: April 2012

Using the echolocation, bats can capture moving objects in real 3D space. Bats emit the frequency modulation sound and can accurately localize these objects from echoes. The object's range could be estimated from delay times between the emitted sound and echoes from objects. These positions in 2D space could be estimated from the difference between delay times at two ears, and the accuracy of localization was dependent on the range accuracy, which was dependent on the frequency width of the emitted sound, the signal-noise-ratio (SNR), and the Doppler shift. It has been shown that the previous proposed model could accurately estimate each range of static objects by using the frequency modulation sound at the low SNR. However, it is unknown whether this model could estimate the moving object in 2D space. In this study, the echoes were measured from the rotating pole by emitting intermittently the LFM sounds. These echoes were analyzed by using the Gaussian Chirplet filters with a carrier frequency compatible with emission sweep rates. It was clarified that this proposed model could track the moving object by estimating object's position in 2D space at each time.
Research on blind source separation of marine mammals signal processing under watercraft emitted noise
Authors: Liang Zhang , LongXiang Guo
Published: April 2012

As statistical independence exists between marine mammals sound and watercraft emitted noise, and among different organism signals, the paper introduces blind source separation (BSS) into marine mammal signals processing. BSS with single hydrophone is a special underdetermined blind separation problem, and BSS based on matrix calculating is no longer suitable. The problem can be solved by expanding channels, and further study finds that second iteration of blind separation can improve the performance. Algorithm simulation and experimental data analysis show that not only marine mammals signal but also different organism signals can be separated by this method with single hydrophone. It is proved that the correlation coefficient of the separated signal is obviously improved, which lays the foundation for the feature extraction and recognition of marine mammals signal. Keywords-marine mammals signal processing; BSS; maximum signal noise ratio criterion; second iteration
Progress and challenges in axial transmission measurements of guided modes in cortical bone
Authors: Minonzio Jean-Gabriel , Foiret Josquin , Moreau Ludovic , Talmant Maryline , Laugier Pascal
Published: April 2012

Cortical bone porosity has been evidenced as being a major if not the major `footprint' of bone loss and fragility. Several studies report that cortical bone behaves like a waveguide. Measurements of guided mode wavenumbers together with appropriate waveguide modeling have therefore the potential for providing estimations of effective stiffness coefficients (which are largely determined by cortical porosity) and also cortical thickness. However, data interpretation is challenging due to the heterogeneous, dissipative and irregular nature of the wave guide. Moreover surrounding and internal tissues modify the guided modes. This paper presents current progress by our group in the measurement of the wavenumbers of guided wave modes, using a multi-transmitter multi-receiver axial transmission probe. The guided mode wavenumbers are obtained after projection of test vectors onto the basis of the singular vectors of the transfer response matrix, at each frequency. The method has been validated, first on isotropic elastic and visco-elastic plates, then on bone-mimicking plate and tube phantoms made of transverse isotropic absorbing material. The effect of soft-tissue mimicking layers on top of a bone mimicking phantom has also been studied. Finally, preliminary in vivo testing of the approach on human radius will be presented.
Circumferential cortical wave propagation at the proximal femur predicts bone strength
Authors: Grondin Julien , Grimal Quentin , Guérard Sandra , Barkmann Reinhard , Glüer Claus , Laugier Pascal
Published: April 2012

The importance of predicting hip fracture risk and the key role of cortical bone to maintain femur neck mechanical integrity both motivate one important aspect of the research presented here which is to focus ultrasound measurements on cortical bone at the femoral neck. Hypothesizing that the circumferential propagation at the femur neck may be predictive of femur strength, this in vitro experiment investigates the relationship between ultrasound circumferential propagation and femur strength. For nine femurs of women we measured: (1) the time-of-flight (TOF) of the first arriving circumferential wave guided by the cortical shell at the femoral neck; (2) structural features and density (BMD) using quantitative X-ray computed tomography; (3) femur strength in one-legged stance configuration with state-of the-art mechanical tests. Significant relationships were observed between TOF and mechanical parameters: failure load: R2=0.79; elastic energy: R2=0.63; apparent stiffness: R2=0.70; TOF was also well correlated with BMD in the inferoanterior quadrant of the neck, consistently with a circumferential propagation path along the thicker inferior cortex. Our results evidencing that circumferential propagation TOF is related to strength and reflects local properties of the femoral neck cortex offer perspectives for enhanced in vivo assessment of bone strength directly at the hip.
Photo-acoustic excitation and detection of fundamental antisymmetric Lamb mode in coated bone phantoms
Authors: Moilanen Petro , Karppinen Pasi , Karppinen Timo , Zhao Zuomin , Myllyla Risto , Haeggstrom Edward , Timonen Jussi
Published: April 2012

Photo-acoustic (PA) imaging was combined with skeletal quantitative ultrasound (QUS) for multi-mode ultrasonic assessment of human long bones. This approach permits tailoring the ultrasonic excitation and detection to efficiently receive the fundamental antisymmetric Lamb mode (A0) through a coating of soft tissue. The method was tested on five axisymmetric bone phantoms of individualized wall thickness (1-5 mm) made of a composite material and coated with a layer (2.5 mm) of soft material that mimics the soft tissue. Signals were excited with a pulsed Nd:Yag laser at 532 nm wavelength and detected on the same side of the coated phantom with (i) a laser Doppler vibrometer (LDV) and for comparison also with (ii) a piezoelectric contact ultrasound receiver, scanning a source-receiver distance of 20-50 mm along the phantom. At a centre frequency of 50 kHz, a phase velocity consistent with that of the theoretically predicted A0 mode was identified in the recorded signals. Our results thus suggest that photo-acoustic quantitative ultrasound enables assessment of the thickness-sensitive A0 mode in bone through a layer of soft tissue. Ultrasonic in vivo characterization of the cortical bone thickness may thus become possible.
Dependence of local wave velocity in bovine cortical bone on the decalcification
Authors: Fukui Kenji , Tsubota Ryo , Matsukawa Mami
Published: April 2012

Bone is a composite material, mainly composed of HAp crystallites and type I collagen. It is known that the amount and orientation of HAp crystallites contribute to the “bone quality”, which affects the bone elasticity. In this study, using a micro-Brillouin scattering technique which is able to evaluate wave velocity in the minute area, the effect of HAp amount on the velocity was measured. 36-plate-specimens in the plane of bone axis and radial directions were obtained from the middle part of a bovine femur. Wave velocity and HAp amounts were evaluated by the micro-Brillouin and XRD techniques, respectively. The specimens were then decalcified using ethylenediaminetetraacetic acid and measured again. Before decalcification, the average velocity was 5.06×103 m/s, and showed a moderate correlation with the HAp amounts (R2}=0.56). After decalcification, the average velocity dramatically decreased to the value of 3.28×103 m/s, showing a strong dependence on the HAp amounts. In addition, the wave velocities except for the lateral part shows the moderate correlation (R2}=0.30) before and after decalcification, which implies the possible effects of collagen on the wave velocities.
The comparison between passive and active methods of online cavitation detection
Authors: Liu Jin , Yan Zhaoli , Yang Jun , Qiao Wenxiao
Published: April 2012

Cavitation is the Achilles' heel of kinetic pumps and propellers. It can lead to performance degradation, structure vibration and noise, and bring about material erosion. Therefore some methods should be taken to detect cavitation. In this work, passive and active acoustics methods of online cavitation detection are set up to recognize cavitation and non-cavitation state. The former uses a hydrophone to receive emitted hydroacoustics signal. The signals from 10 kHz to 60 kHz are analyzed to extract features for pattern classification. The latter applies ultrasound to acquire flow field message. The ultrasound received is demodulated and the modulating signal is also analyzed for pattern classification. Experiments based on the two methods are carried out. Classification accuracy, computational complexity and installation difficulty are compared. Their applicability is also summarized.
Simultaneous measurement of density and viscosity of fluid using vibration of structure constrained by fluid
Authors: Kim Deokman
Published: April 2012

Measurement of rheological properties of fluid using vibration of structure constrained by fluid. The fluid density and viscosity is the quantity to be measured and monitored during various manufacturing process. In this study, a real-time experimental method to simultaneously measure the density and viscosity of the fluid is proposed. The effects of fluids on flexural vibration of the beam structure partially immersed in fluid are analyzed. The density and viscosity have effects on the fluid-structure interaction. To analyze the fluid-structure interaction effects, the fluids are modeled as a simple support at one end of the beam. Using the proposed method, the density and viscosity of viscosity standard fluids were measured and its result was verified. The proposed method is advantageous in that the setup is possible to be installed in any fluid undergoing manufacturing process for real-time monitoring.
Flow noise from the transition region of an axisymmetric body in water
Authors: Li Xuegang , Yang Kunde , Ma Yuanliang
Published: April 2012

Flow noise from transition region of an axisymmetric body is important for predicting the self-noise of a sonar mounted on an underwater platform. Numerical calculation of the flow noise for an axisymmetric body is presented and the diffracted loss on the head surface of the body is calculated by the geometrical theory of diffraction. The main physical features of flow noise are obtained. The flow noise in horizontal symmetry profile of the axisymmetric body is non-uniform, but it is omni-directional and has little difference in the cross section of the body. Based on the simulation, the noise power level increases with velocity to approximately the fifth power at high frequencies, which is consistent with the experiment data reported in the literature. Meanwhile, the flow noise received by the acoustic array on the curved surface has a stronger correlation than that on the head plane at the designed center frequency, which is import for sonar system design. Furthermore, the flow noises of two models with different shapes are compared and a rather optimum fore-body geometric shape is given.
On the characterization of acoustic two-port sources using multi-load method
Authors: Zhang Hao , Feng Tao , Zhou Chengguang , Liu Bilong , Liu Ke
Published: April 2012

A multi-load method for determining the source data of acoustic two-port sources is presented. By eliminating the term of source strength, the scattering matrix can then be obtained by solving a set of nonlinear algebraic equations, and the source strength is determined by the scattering matrix and the directly measured spectrum matrix corresponding to one of the acoustic loads. Numerical simulations indicate that the proposed method is effective. The method has been tested on a loudspeaker and an axial flow fan in a duct. The source data obtained by this method show reasonable agreement with that measured by the direct method. The multi-load method avoids using external sources, and it can be used as an alternative method when the external source is not easy to realize in practice.
Flow-induced acoustic resonance prediction using the transfer matrix method
Authors: Liu Fei , Yang Sam , Cattafesta Lou
Published: April 2012

Acoustic resonance in a flow piping system may trigger an occupational or safety issue and can lead to equipment damage. Computational fluid dynamics (CFD) simulations are often used to predict such resonance phenomenon. However, this approach is generally time consuming and requires specialized training and expensive software. In addition, CFD is not viable for routine design purposes due to its computational expense. In this study, an alternative plane-wave based model for a hydraulic piping system is therefore developed using the transfer matrix method (TMM). Such a model can offer a fast yet reasonably accurate prediction for self-sustained pressure oscillation in a piping system. The advantage of the TMM is the simplicity with which the transfer matrix of a system can be generated from a combination of the TMs of its subsystems via matrix operations. The hydraulic piping system under study consists of a duct with constant cross-sectional area, diffuser, nozzle, bends, valves and orifice plate. The TM of each component is developed and compared to either CFD predictions or available experimental data, the TM of the complete system is derived. Design recommendations are made to reduce and/or avoid resonance in the piping system.
Low-dimensional modelling of sound generation by a flow past a bluff body
Authors: Seid K. H. , Leung Randolph C. K. , Lam Garret C. Y.
Published: April 2012

Searching for a unified methodology for controlling aeroacoustics of common structural discontinuities (e.g. bluff body, open cavity, etc.) has been a major topic among aeroacoustics research community. However, constrained by the complexity and nonlinearity of the flow governing equations, the process of reduced order modeling is usually required in which a low-dimensional, reduced-order model is created for approximating the full high-dimensional dynamics of the flow unsteadiness for control implementation purpose. The present study aims to extend two model reduction approaches, namely Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) via Galerkin projection method, to develop the reduced-order models for full compressible flows. The versatility of these methods are evaluated and compared by applying them to the aeroacoustics of flow past a square cylinder. It is expected that the outcome of this study could facilitate the development of a unified and versatile closed-loop control methodology for effective aeroacoustics control.
Investigation of noise radiation from a jet engine inlet by direct numerical simulation
Authors: Parrish Sarah , Tam Christopher
Published: April 2012

In a jet engine, strong tones are produced by the fan and are radiated out of the inlet. Such fan noise is an important contributor to the total aircraft noise during take-offs and landings. Experimentally, it has been found that the sound radiation patterns from in-flight tests are quite different from those measured in static conditions. What accounts for this difference? In the current work, the radiation problem is studied computationally using direct numerical simulation based on the most advanced computational aeroacoustics methods. Both static conditions and flight conditions are reproduced. A thorough study of the computed results involving static and flight conditions leads to a physical explanation of the observed difference in the sound radiation patterns. (Invited for presentation in the Aeroacoustics Session)
Numerical simulation of grazing incidence of sound waves on an acoustic liner
Authors: Tam Christopher , Pastouchenko Nikolai
Published: April 2012

Acoustic liner is extremely effective for suppressing fan noise of jet engines. A resonant acoustic liner consists of a face sheet with cavity backing. Numerous small holes are drilled on the face sheet. When a sound wave is incident on a liner, pressure on the liner surface alternates from high to low. At high pressure, fluid is forced into the liner cavities through the holes. At low pressure, the process is reversed. The oscillatory motion of the fluid masses at the hole-openings is crucial to the damping of the sound waves. However, the hole diameter is typically one millimeter or less. Because the holes are small, experimental measurements of the fluid motion around the hole-openings are difficult to perform. Hence, this task is best carried out by numerical simulation; as small holes are not detrimental to numerical computation. The objective of this investigation is to seek an understanding of the flow physics responsible for acoustic damping by a liner. In all previous investigations, only one resonator is simulated. In this study, a liner with eight resonators is simulated. This allows, for the first time, a study of the aggregated effect of multiple resonators on an acoustic field. (Invited for presentation in the Aeroacoustics Session)
Assessment of nonlinear perfectly matched layer boundary conditions for CAA benchmark problems
Authors: Lin Dakai , Li Xiaodong , Hu Fang Q.
Published: April 2012

Non-Reflecting Boundary Conditions (NRBCs) are very crucial for accurate numerical simulation of aeroacoustic problems. This paper aims to assess the performances of recently developed nonlinear Perfectly Matched Layer (PML) NRBCs by several Computational Aeroacoustics (CAA) benchmark problems through the comparison with the linearized PML, the characteristic and the asymptotic NRBCs. Numerical results show that the performances of the nonlinear PML NRBCs are tantamount to each other, and there is no substantial difference. But for strongly nonlinear cases, the error caused by using nonlinear PML NRBC is 1~2 orders of magnitude smaller than the one caused by using the linearized PML NRBC. Thus, using nonlinear PML is necessary in strong nonlinear aeroacoustic problems. Numerical tests also demonstrate that the nonlinear PML NRBCs outperform the characteristic NRBCs significantly, and have better performances than the asymptotic NRBCs.
A new algorithm for deghosting in passive acoustic air surveillance systems
Authors: Zhang Xuelei , Feng Jie , Li Zhaoli
Published: April 2012

This paper addresses the false association (called ghosts) problem of multi-target tracking in a distributed passive acoustic sensor network. To eliminate these ghosts, a new deghosting scheme based on the generalized triangulation has been proposed. First, the received angle information of different targets is reordered by using the gray theory to obtain the correct sequence. Successively, time span match triangulation based on pretreatment algorithm of angle association is used to get the most-likely position of different targets. Last, the residual ghosts are cancelled by using a reasonable hypothesis and third site notarization. The validity of the proposed scheme is evaluated using both simulation and experimental results.
Gauging the likelihood for acceptance of a paper submitted to the Journal of the Acoustical Society of America
Authors: Pierce Allan
Published: April 2012

Authors contemplating submitting papers to the Journal of the Acoustical Society of America (JASA) should first determine whether JASA is an appropriate journal, as it is possible that submissions for which this is not the case will be immediately rejected. A principal criterion is whether the paper will find a wider readership with JASA publication than with an alternative journal. If the appropriateness for JASA may not be manifestly obvious to the editors, then the authors should submit a cover letter explaining why, and they should write their paper so that there is a clear tie-in with articles previously published in JASA, preferably recent articles. Authors are advised to select the Associate Editor who is most likely to be familiar with the subject matter of the paper. Given that the paper is appropriate and an Associate Editor can be identified who is willing to handle the paper, it will be subsequently judged for possible acceptance based on several criteria: the most important being whether the paper is (i) original, (ii) significant, (iii) clearly written, and (iv) suitably limited in scope. The significance criterion is discussed at some length. The talk is illustrated by several disguised examples of recent submissions which were rejected.
Understanding the peer-review process in the Journal of the Acoustical Society of America
Authors: Xiang Ning
Published: April 2012

The Journal of Acoustical Society of America (JASA) is an archival, peer-reviewed journal that has served the acoustics community for over 80 years. A rigorous peer-review process often results in significantly improved manuscripts qualified for publication; it also allows relative academic freedom and fairness. To help prospective authors disseminate their research results and progress, the JASA editorial board regularly publishes detailed, updated information, and guidelines. In addition to following these guidelines, a better understanding of the peer-review process is also critically important for prospective authors. This talk will provide some insights into the different roles and the interrelationship between the author(s), and the reviewers. This talk will also discuss criteria for accepting manuscripts, and engagement of knowledgeable reviewers using some disguised examples.