bluuebunny/crossref_metadata_2025 huggingface dataset:
Age-dependence and variation of elastic properties and cortical porosity in human femoral neck and shaft
Authors: Malo Markus Kalle Henrik , Rohrbach Daniel , Isaksson Hanna , Töyräs Juha , Jurvelin Jukka Sakari , Raum Kay
Published: April 2012

Tissue level structure and mechanical properties are important determinants of macroscopic bone strength. Scanning acoustic microscopy (SAM) provides maps of local elasticity in bone. The present aims were to evaluate spatial variations of elastic and structural properties in human femoral neck and shaft, and their variations with age. A total of 48 transverse cross-sectional bone samples were obtained from femoral neck (Fn) and proximal shaft (Ps) of 24 cadavers (21 men, 4 women; age 49.2±16.3 years). Samples were measured with a custom SAM using a 50-MHz ultrasound transducer. Distributions of the elastic coefficient c33 of cortical (Ct) and trabecular (Tr) tissues and microstructure of cortex (cortical thickness Ct.Th and porosity Ct.Po) were investigated (ANOVA). Significant variations in c33 were observed with respect to tissue type (trabecular < cortical), location (Ct.Ps=32.3GPa > Ct.Fn=29.9GPa > Tr.Ps=28.9GPa > Tr.Fn=26.9GPa, and cadaver age. Regional variations in Ct.Po were found in the neck (inferior 6.7%; superior 13.2%; anterior 11.3%; posterior 9.1%) and in the shaft (medial 9.3%; lateral 8.0%; anterior 8.3%; posterior 12.9%). This study provides a comprehensive database of age-dependent spatial distributions of microstructural and microelastic properties in the femoral neck and shaft.
Numerical investigation of ultrasound reflection properties in cancellous bone
Authors: Hosokawa Atsushi
Published: April 2012

Bone is composed of two components of cancellous and cortical bones, and cancellous bone is generally surrounded by cortical bone. Therefore, ultrasound waves propagating in bone can reflect at the boundary between cancellous and cortical bones. In this study, the ultrasound reflection properties in cancellous bone were numerically simulated using a finite-difference time-domain (FDTD) method with microcomputed tomographic (μCT) models of the bone. From the simulated results, it was investigated how the ultrasound waves propagating in cancellous bone could reflect at the boundary. The reflected waveform at normal incidence to the boundary was calculated using the numerical model comprised of two layers of cancellous and cortical bones, and only the reflection properties were derived by subtracting the waveform calculated using the model adopting the absorbing boundary condition instead of the cortical bone layer. In the case of the strong trabecular orientation parallel to the ultrasound propagation, the reflections of both fast and slow longitudinal waves could be observed.
Influence of healing time on the echographic response of the bone-implant interface
Authors: Mathieu Vincent , Vayron Romain , Soffer Emmanuel , Anagnostou Fani , Haiat Guillaume
Published: April 2012

The study aims at investigating the effect of bone healing on the ultrasonic response of coin-shaped titanium implants. Sixteen implants were inserted on the tibiae of rabbits. Two groups of eight samples were considered, each group corresponding to a healing duration (7 or 13 weeks). After the sacrifice, the ultrasonic response of the bone-implant interface was measured in vitro at 15 MHz with a 2-D scanning device. The average value of the ratio r between the amplitudes of the echo of the bone-implant interface and of the water-implant interface was determined. The fraction of implant surface in contact with bone was measured by histomorphometry. The ultrasonic quantitative indicator r decreases significantly with healing time (p = 2.10-4, from r = 0.53 to r = 0.49). Two phenomena are responsible for the decrease of the gap of acoustical impedance at the bone-implant interface: i) the increase of mineralization of newly formed bone tissue and ii) the increase of the bone-implant contact fraction (from 27 % to 69 %).
Processing dipole acoustic logging data to image fracture network in shale gas reservoirs
Authors: Chunxi Zhuang , Yuanda Su , Xiaoming Tang
Published: April 2012

A recent advance in borehole remote acoustic reflection imaging is the utilization of a dipole acoustic system in a borehole to emit and receive elastic waves to and from a remote geologic reflector in formation. An important application of this new technique is the delineation of fracture network in shale gas reservoirs, as interest and activities in shale gas exploration increase in China. We develop a data processing procedure and implement it to handle routine processing of dipole acoustic logging data. The procedure takes into account the characteristics of the dipole data, such as frequency, dispersion, attenuation, recording length, and dipole source orientation, etc., to obtain an image of reflectors within 20~30 meters around the borehole. We have applied the technique to process dipole acoustic data from several wells drilled into gas reservoirs in China. The obtained images clearly identify major fracture network in the gas producing intervals of the reservoir, demonstrating the effectiveness of the imaging technique.
Effective mass density for periodic solid-fluid composties
Authors: Mei Jun , Wu Ying , Liu Zhengyou , Sheng Ping
Published: April 2012

Effective mass density is one of the basic parameters in the study of acoustic wave propagating in fluid-solid composites. Based on the multiple-scattering theory, an analytic solution of the dynamic effective mass density for composites with solid inclusions immersed in fluids periodically in two dimensions is obtained in the low frequency limit. When the concentration of solid is small, the dynamic mass density can be described by an angle-dependent dipole solution and the angle-dependence vanishes if the structure has a four- or six-fold symmetry. When the solid concentration is getting large, the dynamic mass density differs from the dipole solution and also becomes structure-dependent even for square and hexagonal lattices. The Wood's formula is accurately valid, independent of the structures, at any solid concentrations. Numerical evaluations from the analytic solution are shown to be in excellent agreement with finite-element simulations. In the vicinity of the tight-packing limit, the dynamic mass density exhibits a universal behavior independent of the lattice symmetry. Support of this work comes from KAUST Start-up Package, National Natural Science Foundation of China (Grant No. 10804086), the Ph.D. Programs Foundation of Ministry of Education of China (Grant No. 200804861018) and Hong Kong RGC grant HKUST 604207.
Treatment of auxiliary power unit as a ground noise source in airport noise modeling
Authors: Shinohara Naoaki , Iwasawa Katsuji , Yamada Ichiro
Published: April 2012

In Japan, noise index for evaluating airport noise was changed from WECPNL to Lden, which will be enforced from April, 2013. It was also decided to take aircraft ground noise within the airport when necessary. As a part of these ground noise components, it is necessary to take account of noise contributions due to APU operation on the apron before take-off, after landing, or maintenance during the midnight. This presentation explains a brief summary of an investigation of sound source characteristics of APU noise and compares noise calculations using the result with measurements observed by unattended noise monitoring devices.
Discussion on measurement method and standard of airport environment noise in China
Authors: Yang Guang , Wang Jianghua , Guo Dandan , Zhu Xiangdong , Yan Xiang
Published: April 2012

With the blooming of economy, aircraft industry is growing rapidly in China. As result, the problem of disturbance from airport noise becomes more and more serious. However, airport noise control in China is still in the beginning stage. Noise testing is an essential part to hand the problem and collecting exact data can show what extent that the noise has impacted on the sensitive areas around the airport. But the Chinese standard GB 9661-88 Measurement of Aircraft noise around airport was promulgated in 1988. It has been over twenty years up to now. So there are some problems, such as, long measuring time, complicated data progressing and other noise interference including construction noise and so on in the actual measurements, which not only make the testing hard, but also difficult to evaluate the real effects accurately. This study will introduce approaches of testing points setting, data collection, filtration and progressing, and point out the practical deficiencies based on site measurements and obtained data. So the paper will be an important reference to revise measurement standard of aircraft noise.
Excitation source structural analysis of Japanese traditional singing voices
Authors: Kawahara Hideki
Published: April 2012

New set of voice excitation source analysis methods are applied to study Japanese traditional singing voices, especially Noh. The first method, XSX (excitation Structure extractor) is capable of visualize detailed structure of subharmonic periodicity, by using multiple dedicated periodicity detectors. The second one analyzes symmetry of the fundamental component waveform, cycle by cycle. It enables to discriminate voice onset and offset details.
Analysis of high-frequency energy in singing and speech
Authors: Monson Brian B. , Story Brad , Lotto Andrew
Published: April 2012

The human singing and speech spectrum includes energy above 5 kHz, but this portion of the spectrum is typically ignored in speech and voice science. Generally it has been assumed that this high-frequency energy (HFE) contributes to only qualitative percepts of singing and speech, but prior work shows HFE contributes to several non-qualitative percepts, including speech intelligibility. To begin an in-depth exploration of HFE, a database of multi-channel anechoic high-fidelity recordings of singers and talkers was created and analyzed. Third-octave band analysis from the long-term average spectra (LTAS) showed that production level (soft vs. normal vs. loud), production mode (singing vs. speech), and phoneme (for voiceless fricatives) all significantly affected HFE characteristics. Female HFE levels were significantly greater than male levels only above 11 kHz. As expected, HFE was found to be highly directional toward the front of the singer/talker. While this information resulted from a study initially focused on singing voice aesthetic, it is pertinent to various areas of acoustics, including vocal tract modeling, voice synthesis, augmentative hearing technology (hearing aids and cochlear implants), cell phone technology, and training/therapy for singing and speech. [Work supported by NIH-NIDCD.]
Lessons learned for implementing near-field active control systems to achieve global control of fan noise
Authors: Sommerfeldt Scott D. , Gee Kent L.
Published: April 2012

Work has been ongoing for a number of years to develop compact active noise control systems that can effectively achieve global attenuation of radiated fan noise associated with information technology (IT) equipment. Both axial and centrifugal fans are used in IT applications, and both types of fans have been studied. An approach has been developed that can guide the user to properly implement near-field sources and sensors to achieve significant global attenuation of the fan noise. These concepts have been investigated experimentally in numerous configurations to verify the effectiveness of the approach. Both narrowband and broadband noise components have been targeted, and limitations on the attenuation that can be achieved have been established. The sensitivity of various configurations has also been studied, and it has been found that some implementations may be able to achieve greater attenuation, but are also much more sensitive to placement errors of the sources and sensors. This paper will overview the research to date and provide an overview of lessons that have been learned for effective implementation of near-field control techniques in order to achieve global attenuation.
Fixed point realization of partial updating adaptive algorithm for active noise control
Authors: Lu Jing , Chen Kai , Zou Haishan
Published: April 2012

An efficient low cost realization of the partial updating FXLMS algorithm is proposed in this paper. Unlike the conventional partial updating adaptive filters, the modified sign-LMS algorithm is used to make it easier to be implemented in a fixed point DSP. Moreover, the calculation of the filtered reference signal is divided into several steps, which further reduces the whole computational burden. An active noise controller using TMS320C5502 DSP chip is designed based on the proposed algorithm. The experiment results demonstrate that at a reasonable updating rate, the proposed algorithm has exactly the same performance with the normal float-point FXLMS algorithm while the computational burden is much lower.
A novel frequency-domain periodic active noise control algorithm with nonlinear secondary path
Authors: Wu Ming , Yang Jun
Published: April 2012

Frequency-domain periodic active noise control (FDPANC) algorithm is usually adopted for harmonic noise reduction. However it may fail to converge when the secondary path includes a nonlinear element. In this paper, the convergence behavior of FDPANC algorithm with nonlinear secondary path is analyzed and a sufficient condition for convergence is derived. Unlike the conventional FDPANC algorithm with linear secondary path, this sufficient condition for FDPANC algorithm with nonlinear secondary path is time-varying and depending on the coefficients of the adaptive filter. If system has a steady-solution, the sufficient condition can be satisfied for all iterations by selecting the proper initial values. In this situation, the adaptive filter will convergent to the optimum value and the disturbance signal can be eliminated totally. If system has no steady-solution, the sufficient condition cannot be satisfied for all iterations whatever the initial values are. Based on the sufficient condition for convergence, a modified FDPANC algorithm integrated with convergence detector is also proposed in this paper.
A pretest of several versions of a survey questionnaire for use in Rocky Mountain National Park, USA
Authors: Schomer Paul , Boyle James
Published: April 2012

This paper presents the results of a pretest of visitors' perception of the soundscape on hiking trails in the Bear Lake area of Rocky Mountain National Park, Colorado, USA. The pretest involved 5 versions of a procedure for administering the questionnaire. This pretest includes concurrent noise monitoring with the noise monitor generally spaced 1 to 2 km apart. For those versions of the pretest survey that included questions during the hike, the test booklet included a position and time recording GPS. Although the majority of visitors to the Bear Lake area go on 0.5 to 3 km long hikes, most hikers that we selected went on hikes that were in the length range of 5 to 10 km. The Bear Lake area is the busiest hiking area in Rocky Mountain National Park; it receives about 10 to 20,000 visitors per day during nice summer days. As a result, one source of anthropogenic sound that contributed negatively to the soundscape was the sound of other hikers; beyond about 1.5 km from the transit area, hikers on the trails thinned markedly. Based on the results of the pretest analysis, a full-scale test plan is recommended.
Cavitation thresholds and why to be wary!
Authors: Bull Victoria , Rivens Ian , ter Haar Gail
Published: April 2012

Many biological studies involving ultrasound exposure report acoustic cavitation “thresholds”. The purpose of these is often to convince the reader either that cavitation activity was avoided, or that it definitely occurred as the exposure was “above the threshold”. Formally, the cavitation threshold is the minimum negative pressure amplitude at which pre-existing bubbles begin to oscillate (non-inertial cavitation) or collapse (inertial cavitation). The cavitation nucleation threshold is that for which bubbles can be drawn out of solution and driven to oscillate. Since the true physical cavitation threshold of a medium can only be measured if it is possible to detect single bubble activity, quoted thresholds are more likely to represent a threshold for detection than for cavitation activity. Furthermore, they may not be relevant beyond the specific experimental conditions tested. In interpreting a negative pressure threshold for cavitation in tissue it is important to know, amongst other things: the tissue status and sample geometry (in order that the in situ pressure may be calculated); details of the ultrasound exposure; method of cavitation detection and detector geometry; data gathering, processing and interpretation methods; threshold definition; sample statistics. Without these details, results may be misleading.
Evolution of acoustic cavitation structures induced by a liquid jet
Authors: Bai Lixin , Deng Jingjun , Li Chao
Published: April 2012

Temporal evolution and spatial distribution of acoustic cavitation structures induced by a liquid jet in a 20 kHz ultrasonic field were investigated experimentally with high-speed photography. It is revealed that a large-scale flare structure is produced by a liquid jet shooting towards a transducer radiating surface. A few large bubbles and numerous small bubbles are formed on the interface of liquid jet. The size of large bubbles differs almost by an order of magnitude from that of small bubbles. The flare structure hits the radiating surface, spread and adhere. The liquid jet is arrested and a thin bubbly layer lying at the radiating surface is formed. The cavitation cloud will evolve from one structure to another without the interference of liquid jet. (a) Most bubbles move towards the center, and the bubbly layer will become thicker at the centre than at the periphery like a lens. (b) Large bubbles accumulate at the center and skip off the surface, and the lens structure becomes a conical structure. (c) Large bubbles align themselves along the axial line, and the conical structure becomes a fishbone structure. Many other interesting phenomena were observed. The liquid-jet method is useful for the investigation of cavitation structure. This work is supported by the National Natural Science Foundation of China (Grant No. 11174315) and the National Science and Technology Major Project of China (Grant No. 2011ZX05032-003).
Cortical activation associated with the unmasking effect of perceived separation on speech perception
Authors: Li Huahui , Mao Lihua , Wu Xihong , Li Liang
Published: April 2012

Spatial separation between the sound images of the target speech and the masker can improve recognition of the target speech, especially when the masker is irrelevant speech. In the present study, functional magnetic resonance imaging (fMRI) was used to investigate the neural basis of the unmasking effect of the perceived spatial separation. Target sentence was presented along with either steady-state speech-spectrum noise or irrelevant 2-talker speech at the signal-to-noise ratio of -8 dB through headphones. Position of the target image and that of the masker image were manipulated separately by modulating the time interval between the left and the right headphones, thus the two images were either co-located or separated. Sparse temporal sampling was used to avoid the influence of scanner noise. The results show that bilateral superior temporal gyrus (STG) activation was larger under the speech-masking condition relative to the noise-masking condition. When the masker is speech but not noise, the target-masker co-location was associated with more activation in left post parietal lobe and bilateral precentral/postcentral gyrus relative to the target-masker separation. The results suggest that more demand of both attention resource and central processing are required when the target speech is perceived as co-located with the speech masker.
Feature-specific cortical plasticity after rapid perceptual learning during speech segregation: a MEG study
Authors: Du Yi , He Yu , Wu Xihong , Li Liang , Alain Claude
Published: April 2012

This study examined whether 1-hour perceptual training could elicit feature-specific improvement of performance and corresponding cortical plasticity in humans during speech segregation by using magnetoencephalography (MEG). One group of participants learned to segregate concurrent vowels by using difference in fundamental frequency (f0) while the other group learned to use difference in sound location. MEG recordings were conducted after the training and required participants to identify the two different vowels, which may have the same f0 and location or differ in f0 only, location only or both f0 and location. Compared to Control Group who didn't receive pre-scan training, the trained groups showed behavioral improvements specific to the trained cues which were paralleled by feature-specific changes on brain activities. That is, f0-difference-induced changes in dipole source-waveforms in auditory cortex were only modulated in Frequency Group, while location-difference-induced changes were only modulated in Location Group. Furthermore, Frequency Group showed stronger activations in auditory “what” pathway than Location Group when processing f0-difference, while Location Group revealed stronger activation in auditory “where” pathway than Frequency Group when processing location-difference. The double-disassociation in both behaviors and neuromagnetic responses indicates that rapid perceptual learning could elicit highly feature-specific plasticity in human cortex during speech segregation.
Cabin noise controlling on MA600
Authors: Hou Feng , Yan Qun
Published: April 2012

MA600 is one turbo-propeller driven regional aircraft modified from MA60, which has considerable high interior noise level. Project on MA600 cabin noise reduction involve numbers flight test, huge laboratory measurement campaign as well as numerical simulations. Based on the understanding of noise sources and their transmission path learned from both test and simulation, an integrated acoustic treatment plan was drawn and implemented on the MA600 to reduce the interior sound pressure level while weight reduction was also archived.
The experimental research of acoustic property of anti-ice shield for propeller aircrafts
Authors: Pan Kai , Qin Haoming
Published: April 2012

For propeller driven aircraft, the structural noise caused by periodic aerodynamic load on the fuselage hence transmitted into cabin is dominating, especially on the propeller rotating plane. The anti-ice shield is effective against such. Through experimental research, the sound isolation property of the anti-ice shield from one particular aircraft was improved, and the routine of acoustic property optimization was summarized.
The effect of random bottom bathymetry on mode structure and coherence in shallow water propagation
Authors: Wylie Jennifer , DeFerrari Harry
Published: April 2012

Ideal flat bottoms in shallow water propagation channels produce predictable surface-reflected-bottom-reflected ( SRBR) mode structures. Further, modes have predictable group velocities so that arrivals patterns for pulse transmissions can be identified by travel time. But bathymetry is rarely truly flat to a fraction of an acoustic wavelength over ranges of a few km. Here, we examine the mode pattern deviation from the flat bottom case as random variations in bathymetry are introduces. A PE propagation model with range dependent bottom reveals that mode structures become distorted with increasing fluctuation in bathymetry. Higher order modes deteriorate first and the fundamental mode propagates longest without distortion. For higher order modes, RMS fluctuations greater than 1/2 the acoustic wavelength destroy recognizable mode structure as compared to the smooth bottom case. If the fluctuations are further increased to 1 wavelength, discreet modes give way to continuous ones and energy is smeared in space and arrival time and mode arrivals become incoherent and undetectable with the commonly used phase coherent signal processing methods. The coherence of modes has implications on both temporal and spatial coherence. The models are used here to predict the frequency/depth/range limits on coherence for simple statistical description of bottom bathymetry fluctuations.
The mode coupling and effect on ambient noise vertical directionality caused by internal waves in shallow water
Authors: Jiang PengFei , Lin JianHeng , Yi XueJuan , Jiang Guojian
Published: April 2012

Experiments show that internal waves can cause the fluctuation of the depth of thermocline in shallow water, which may bring about two results: one is the change of hit number of sound rays and sea bottom, the other is mode coupling. The former changes the sound intensity, and the latter changes the sound energy distribution. The previous studies show that internal waves cause mode coupling by changing the sound propagation paths, which can fill the noise notch. In the calculation, it is found that the notch is deepened when some solitary internal waves are present. The reason is that the sound wave excited by the distant sources which are located on the palne near the sea surface propagates through the soliton which is a single downward undulation. The mode coupling from low-order modes to higher-order modes happens first, then the reverse conversion occurs. However, the former coupling is stronger, the lower-order modes fall off and the filling ability is weakened, so the notch is deeper.
Quantitative predictions of impact pile driving noise in water using a hybrid finite-element propagation model
Authors: Zampolli Mario , Nijhof Marten J.J. , Ainslie Michael A. , De Jong Christ A.F. , Jansen Erwin H.W. , Abawi Ahmad T.
Published: April 2012

The quantitative prediction of noise radiated into the underwater environment during offshore impact pile driving is a topic of major interest to the underwater acoustics community. This problem is addressed by using a hybrid model consisting of a high fidelity local model describing the vibrating pile and its vicinity, and an efficient model for the propagation of the sound to large distances from the pile in the underwater waveguide. The local model is an axisymmetric linear frequency domain structural acoustic finite-element model, and the propagation model is based on ring-source Green's functions in the water and in the sediment surrounding the pile, obtained by horizontal wavenumber integration. The coupling between the two models is achieved via the Helmholtz integral, in which the pressure and normal displacement in the media surrounding the pile are obtained by sampling the finite-element model results and the Green's functions are obtained from the propagation model. The simulation results are compared to measurements conducted during pile driving operations, showing that the quantitative prediction of the sound exposure levels with such a tool is possible.
Low- to mid-frequency scattering from submerged targets partially buried in the sediment at an oblique angle
Authors: Zampolli Mario , Espana Aubrey L. , Williams Kevin L. , Marston Philip L.
Published: April 2012

The scattering from elastic targets in the low- to mid-frequency regime is affected by the environment surrounding the target. For axisymmetric targets with the axis of symmetry parallel to the water-sediment boundary, previous work has dealt with the change in the target strength as a function of frequency and aspect angle in relation to the burial depth in the sediment. The present work deals with the extension of a finite element model, based on the decomposition of the acoustic and elastic fields into azimuthal Fourier modes, to the case of a target buried at a tilt angle. The interaction between the target and the sediment is represented by the model up to the first order of the scattering series, which means that the scattering of the incident field and of the target reflected field is taken into account, but the rescattering of the boundary reflected echo from the target is neglected. Model results up to 30 kHz are compared to experimental data for a 2 foot long aluminum cylinder of 1 foot diameter buried in sand at a tilt angle.
The effects of lumped mass attachments on vibro-acoustic behavior of a fluid-loaded plate
Authors: Yu Danzhu , Li Sheng , Chen Yunfei
Published: April 2012

The effects of attachments on the dynamics of a master structure are of fundamental significance. In this study, the changes in the vibro-acoustic behavior of a fluid-loaded plate due to variations in lumped mass attachments are examined. The finite element for modeling the structure with lumped mass attachments is coupled with the Rayleigh integral for the acoustic fluid to solve the structure–fluid interaction problem and to obtain the response of the coupled system. The changes in the modal parameters due to the variations in attachments are determining from a model reduction method. The Monte Carlo simulation is used for the uncertainty analysis of the vibro-acoustic behavior. Both the mean and the standard deviation of the changes attributable to the attachments are discussed. A baffled plate with water loading/air loading is involved in the study. The numerical results show that the effects and the changes-in-impedance on the master plate due to the attachments vary with the frequency spectrum.
Study on an underwater focused acoustic phased array and the sound fields characteristics
Authors: Zeng Xinwu
Published: April 2012

Regarding to the fact that the hydrodynamic characteristics of supercavitating torpedoes strongly depend on the supercavity envelops, this paper describes a high intensity underwater focused acoustic phased array used to remotely disrupt this envelope surface. First, the demand of designing an underwater focused acoustic phased array was discussed, and then an efficient sound field calculation formula for the convex spherical-section phased array was obtained. Furthermore, the effects of element size and array aperture on the valid focusing region of above array were analyzed based on pseudo-inverse method. It is demonstrated, via simulation, that the arrays composed of minimum element size with large beam angle perform well on the intensity of focus pressure, and the valid focusing region under the similar size of emission area. However, the change of valid focusing region is small when merely enlarge the aperture of array. And the possible application of multiple-focus pattern was investigated.
Acoustics of traditional Chinese theatres
Authors: Wang Ji-qing
Published: April 2012

The traditional Chinese theatre is a unique architectural form. Chinese opera is a form of imaginary performing art; therefore, it does not require large stage and realistic stage settings. A pavilion stage open on three sides and thrusting into the audience area is its commonly applied characteristic feature. A comparatively low ceiling with elegant dome-like caisson acts as a sound shell, providing beneficial reflections to the audience, and to actors on the stage as well. The older generation Chinese opera goers used the term “going to listen opera” which well explains how they placed great demands on vocal performance. In Chinese theatrical history, there were different types of theatre from open-air theatre to hall theatre, built both in cities and rural areas all over the country. Nevertheless, the courtyard theatre was the most popular. Up to the present day, thousands of ancient traditional theatres still exist in China, and many of them are well preserved. Interesting results are reported in this paper after acoustical surveys of these theatres. Acoustical issues are raised from these studies, such as, does the classical parameter of reverberation time still adequate for qualifying the acoustics for a roofless courtyard theatre, or for an amphitheatre as well? A primary subjective survey conducted in our laboratory recently presents the negative conclusion. Another presentation is involved in this paper: the puzzle of vase resonators beneath the traditional stage which was long believed to be effective for sound enhancement as recorded in the Chinese historical accounts. The author also gives other acoustic analysis of the kind with pictorial presentations.
Emerging findings from the Healthcare Acoustics Research Team (HART)
Authors: Ryherd Erica E , Persson Waye Kerstin , West James E , Zimring Craig , Ackerman Jeremy
Published: April 2012

Hospital patients, staff, and visitors need healthy soundscapes: patients need to sleep and heal without stress; staff, patients and family need to communicate accurately but privately; staff need to hear alarms and calls for help. Unfortunately, many hospitals are noisy and stressful places. Although there is growing and strong evidence that the hospital soundscape is problematic, there are many remaining questions and obstacles. This presentation will discuss recent case studies and findings from the Healthcare Acoustics Research Team (HART), an international, interdisciplinary collaboration of specialists in architecture, engineering, medicine, nursing, and psychology. HART is actively engaged in research in the United States and Sweden, having worked in a dozen hospitals and a broad range of unit types including intensive care, emergency, operating, long-term patient care, mother-baby, and others. HART seeks to advance the understanding of how various aspects of the hospital soundscape impact occupants, how to best measure and quantify these aspects, and how to translate results into evidence-based-design. Taken as a whole, these studies provide new insight into how to create healthier hospital acoustic climates.
Speech intelligibility in hospitals
Authors: Hsu Timothy , Moeller Mike , Mahapatra Arun , Ryherd Erica
Published: April 2012

In hospitals, background noise has been shown to be problematic, not only for the patients but also for the staff. With respect to staff members, perceived stress and psychosocial factors can be affected negatively by noise. One particular factor that noise can inhibit is effective speech communication. Speech communication is essential for functions such as evaluation, admittance and treatment of patients. This paper will discuss results from measurements made in several different hospital units where traditional speech intelligibility metrics were analyzed. Additionally, newer analysis techniques such as Noise Occurrence Rates were investigated for their potential usefulness in speech intelligibility applications. Preliminary results show that in general, the hospital units show “poor” to “marginal” Speech Intelligibility (SII) qualitative scores. The results of this study help to better explain how speech is understood in various locations within the hospitals and can aid in hospital designs that support speech communication.
Investigation into the acoustical performance of single stud steel wall assemblies
Authors: LoVerde John , Dong Wayland , Betit Aaron
Published: April 2012

The draft “Interim sound and vibration design guidelines for hospital and healthcare facilities” by the Joint Subcommittee on Speech Privacy of the ASA includes recommended STC ratings for partitions between exam rooms. In a typical hospital, these partitions are about 15 feet high and constructed with 16 gauge studs at 16 inches on center. However, virtually all laboratory testing is performed on 8 foot high walls with 25 gauge studs at 24 in. on center. These tests are used for design and evaluation even though there is little published data on the effects of stud gauge and spacing and wall height on transmission loss. A previous study investigated the acoustical effects of stud gauge and spacing, and documented substantial changes in transmission loss and STC rating [A. Betit, “Performance Dtails of Metal Stud Partition,” J. Sound and Vibration, 44(3), 14–16 (2010)]. A second testing program was established to extend the investigation to the effect of changes in wall height. Transmission loss (STC) tests were performed on drywall partitions of various heights and construction. The results of the testing program are presented.
Public address system reinstallation
Authors: Ho Wilson , Ng Eddy
Published: April 2012

In the last decade, new functions for the Public Address (PA) system have been continuously developed and integrated. On the other hand, the existing PA systems are being less repairable and maintainable due to lack of supply of old version components although the system and loudspeakers are still functioning well within the specifications after many years of use. It appears to be sensible way to reinstall the control and amplification system without replacing existing loudspeakers in order to accommodate the new function and zoning requirements. This approach is being tested in Lantau and Airport Railway (LAR) line in Hong Kong operated since 1998. This paper presents the pros and cons using this reinstallation approach in practice and investigates the feasibility and effectiveness through acoustic simulation and on-site verification test of sound coverage and speech intelligibility.
(Micro-)Perforated wooden panels as sound absorbers
Authors: Eichhorn Adrian , Beckmann Michael , Nocke Christian
Published: April 2012

Different materials have been used as micro-perforated or perforated panels for applications as sound absorbers. The theory of microperforated panel sound absorbers introduced by D.-Y. Maa in 1975 is independent on the material of the panel. So also micro-perforations in wooden panels will give sound absorption. In combination with porous absorbants the efficiency of the absorbers set-ups can be improved. Modern manufacturing tools for wood and wooden veneers allow for perforations of submillimeter diameters of the single pores. Optically these perforations hardly change the impression of the wooden panel. Acoustically the combination of perforated wooden panels and a backing cavity give highly effective sound absorbers. Measured sound absorption coefficients of various set-ups with (micro-)perforated wooden panels will be presented. The new possibilities in design and applications in architectural acoustics will be discussed.
Acoustical perforated facings: a synthesis study of theoretical and experimental developments
Authors: Jaouen Luc , Chevillotte Fabien , Bécot François-Xavier
Published: April 2012

Perforated facings (including Micro Perforated Panels) or perforated ceiling tiles have been widely studied since the fundamental work by Uno Ingard. This work specially focus on flow modifications in the vicinity of the perforations leading to modifications of the reactance of the panel. This communication is a synthesis study of pioneer and recent works on this topic for linear flow regimes, clarifying and correcting some results. One aspect of this communication revisits the length corrections for circular, rectangular and slits perforated panels. A second aspect aims at accounting for perforated panel vibrations based on Biot's theory. Coupling this last approach to the one by Atalla & Sgard [J. Sound Vib. 303, 195–208 (2007)], the current work allows to model perforated facings as elastic-frame porous media. Simulations results are validated using a recently proposed method for the characterization of perforated facings. Based on these results, general trends for dimensioning the acoustical performances of perforated panels are drawn.
Noise attenuation by sonic crystal barriers made of microperforated units
Authors: García-Chocano Victor M. , Cabrera Suitberto , Sánchez-Dehesa José
Published: April 2012

This work studies the absorptive properties of periodic arrays of microperforated cylindrical shells. Structures made of cylinders 3 meters height have been constructed and their reflectance and transmittance spectra are measured in open air at normal incidence. A broadband strong attenuation is found in the low frequency region. Experimental data are supported by model simulations performed in the framework of multiple scattering theory. It is concluded that these structures in combination with high frequency absorbing units are suitable to produce general purpose broadband noise barriers. Work supported by ONR (USA) and MICNN (Spain).
Immediate changes in whale hearing sensitivity
Authors: Nachtigall Paul E. , Supin Alexander Ya
Published: April 2012

We have been examining the hearing of both the outgoing clicks and the returning echoes of actively echolocating odontocetes using evoked auditory potential techniques. In order to protect themselves from the loud outgoing sound while still maximizing the hearing of the acoustic echo return, odontocete echolocators appear to have developed both passive and active control of hearing. Passive control has been demonstrated by comparing hearing of their own outgoing signals to similar signals presented to them from the outside. Clicks produced by the animal itself are heard about 40 dB down. Active control has been demonstrated by a comparison of hearing outgoing clicks during target present and target absent trials. During target absent trials, when searching for targets, hearing is 20 dB more sensitive than during target present trials. The current critical question is: If the animal is warned that a loud sound is about to arrive, does it possess a mechanism of self-mitigation that will allow it to control its own hearing and reduce the level of the incoming sound? Initial results indicate that a false killer whale will reduce hearing sensitivity by at least 15 dB when warned that a 170 dB signal is about to arrive.
Cochlear structural variants in echolocators
Authors: Ketten Darlene R. , Simmons James , Riquimaroux Hiroshi , Cramer Scott , Arruda Julie
Published: April 2012

Although microchiropteran bats and odontocete cetaceans operate in radically different media, both have sophisticated sonar capabilities and evident similarities in their ability to detect and analyze ultrasonic signals. This paper compares the similarities and differences of cochlear cytoarchitecture and its implications for ultrasonic encoding and acuity amongst these groups through the use of three-dimensional models obtained via micro-CT imaging of intact heads and temporal bones. Inner ear anatomy was fundamentally similar with notable parallels in fenestral placement and ratios, membrane dimensions, and neural density and distribution across bats and dolphins with common cochlear types. Specialist ears are present in both groups, suggesting that like some CF-CM bats, one or more odontocete species have cochleae with specialized basilar membrane “foveal” regions. Cochlear specializations in both groups are primarily linked to peak spectra of signal, expanded frequency representation, and may enhance tuning in adjacent ear segments by generating standing wave phenomena. [Supported by N45- US Navy Environmental Division and the Office of Naval Research]
Recovery cycles of inferior collicular neurons in the leaf-nosed bat, Hipposideros armiger
Authors: Tang Jia , Fu Zi-Ying , Jen Philip Hung-Sun , Chen Qi-Cai
Published: April 2012

When stimulated with biologically relevant constant frequency–frequency modulation (CF–FM) sounds, the inferior collicular neurons of the CF–FM bat, Hipposideros armiger, either only discharged impulses to the onset (76%, single-on neurons) of the CF-FM sounds or to the onset of both CF and FM components of CF–FM sounds (24%, double-on neuron). Some neurons were single-on responders at low sound amplitude but become double-on responders at high sound amplitude. Single-on responders had longer latency and recovery cycle than double-on responders. While most neurons did not respond to the second sound when the paired CF-FM sounds overlapped, 3 single-on and 7 double-on neurons did such that they had “cyclic” recovery cycles with inter-pulse intervals. The different response latency and dynamic variation in the recovery cycle of these two types of neurons suggest they may serve as the neural basis underlying a bat's ability to perform echo ranging throughout different phases of hunting.
A simulation and experimental study of long cortical bones fracture evaluation using lamb waves
Authors: Xu Kailiang , He Runxin , Ta Dean , Qin Yixian , Sun Peng , Wang Weiqi
Published: April 2012

Ultrasonic guided waves are promising to evaluate fractured long cortical bones. Guided modes conversion, occurred always on the sites of fractures, contains rich information of bone geometric and material properties. The study is to analyze the correlation between Lamb modes conversion and crack depth of fractured long bones. Axial experiments were designed to investigate the influences of different deep fractures in steel-made bone phantoms and sheep diaphyseal tibias over Lamb modes propagation, especially modes conversion. For comparison, the phantoms were modeled by two dimension finite-difference time-domain method. Group velocities and energies of S0, A0 and converted modes were extracted and analyzed under varying crack depth conditions. Being consistent with the simulation, experimental data showed obvious modes conversions occur between S0 and A0 modes. The fracture positions can be predicted from converted modes velocities. It illustrated the modes conversions become gradually observable with the fracture depth increasing, which can be indicated by the parameter, converted energy proportion (EP). The sensitivity and practicality of EP to assess bone fractures were validated in quantitative analysis of phantoms, simulations and sheep tibias experiments in vitro. In conclusion, ultrasonic guided wave is a reasonable method for long cortical bone fracture detection and evaluation.
Determination of bone thickness: effect of group velocity filtering in multi-component waveguides
Authors: Moilanen Petro , Talmant Maryline , Timonen Jussi
Published: April 2012

Previously, the Jyväskylä group has used the F11 guided wave of an empty tube as the reference dispersion curve for identification of in vitro bone thickness. The role of the marrow has remained an open issue. The objective of this study was thus to test several reference waveguides, empty, fluid-filled and fluid-coated tubes, in modelling of guided modes. For instance, fluid filling in a tube strongly modifies the spectrum of guided waves found for an empty tube, because of coupling of guided waves in the tube wall and in the fluid-filled cavity. However, it is shown that, using group velocity filtering on the signal component of highest amplitude, the effect of fluid filling can essentially be eliminated. The dispersion curve of an apparent F11 mode is obtained with a slight shift only at the lowest frequencies. This small shift means that the dispersion curve of this apparent mode is, in that frequency range, between those of A0 (2D plate) and F11 (3D cylinder), and can to some extent be interpreted as either one of these.
Time-frequency spectrum segmentation method for separating multimodal guided waves in long bones
Authors: Zhang Zhenggang , Ta Dean , Wang Weiqi
Published: April 2012

Ultrasonic guided waves have great potential for evaluating long bones. However, the measured signal often contains multiple wave modes because of the complicated characteristics of guided waves, which cause difficulties to further analysis. In this study, a hollow cylinder filled with a viscous liquid was used to model the long bone, and the multimodal signals were simulated using finite difference time-domain (FDTD) method. The time-frequency spectrum segmentation method was proposed to separate multiple modes. First, the Gabor time-frequency spectrum of multimodal signals was calculated. Second, a multilevel image segmentation algorithm, including the watershed and region growing, was used to find the corresponding area of each mode in the spectrum. Finally, time domain signals representing individual modes were reconstructed from these areas. The validations of this method were analyzed by simulated multimodal signals under different elastic modulus (EM) of long bones, with or without noise. The results showed that the Gabor time-frequency representations of the individual modes were in good agreement with the theoretical dispersion curves. This study suggests that time-frequency spectrum segmentation method can correctly separate multimodal guided waves, which provides a foundation for feature extraction of individual guided modes.