bluuebunny/crossref_metadata_2025 huggingface dataset:
Design of a Novel Vertical Motion Piezoworm Positioner
Authors: Mohammad Tarek , Salisbury Shaun P.
Published: April 2011

Piezoelectric-based positioners are incorporated into stereotaxic devices for microsurgery, scanning tunneling microscopes for the manipulation of atomic and molecular-scale structures, nanomanipulator systems for cell microinjection and machine tools for semiconductor-based manufacturing. This wide range of applications requires the design and development of large load capacity, long stroke and compact positioning stages without compromising high speed and precision. Although several precision positioning systems have been developed for planar motion, most are neither suitable nor readily lend themselves to provide long travel range with large load capacity in vertical axis because of their weights, size, design and embedded actuators. To address the limitations of the traditional technologies, a novel positioner is being developed specifically for vertical axis motion based on a piezoworm arrangement in flexure frames. Analytical calculations and finite element analysis are used to optimize the design of the lifting platform to provide maximum thrust force while maintaining a compact size. To make a stage frame more compact, the actuator is integrated into the stage body which mainly consists of a moveable component outside a rigid frame. The clamps are designed such that no power is needed to maintain a fixed vertical position, holding the payload against the force of gravity.
A Parametric Study and Characterization of Porous, Non-Permeable, and Conductive PEGDA-HEMA Hydrogels
Authors: Chan Christine , Chang Shannon , Naguib Hani E.
Published: April 2011

This study involved the development and characterization of novel porous, non-permeable, and conductive hydrogels. The hydrogels were fabricated with HEMA and crosslinked with PEGDA through a complete parametric study of the synthesis parameters which included water content and crosslinking content. The hydrogels were fabricated using UV photopolymerization and in situ polymerization of PPy, and characterization was conducted with respect to their physical, thermal, mechanical, and electrical properties. The physical properties were analyzed with respect to their swelling ratio and equilibrium water content. The thermal properties were analyzed based on the decomposition temperature and residue weight. The mechanical properties examined the elastic modulus of the hydrogels, and the electrical properties investigated the conductivity of the hydrogels. The relationships observed between the processing, structure, and resulting properties provide the basis for further development and application of these porous, non-permeable, and conductive hydrogels.
Concepts for Standardized Shape Memory Actuators for Positioning Applications
Authors: Meier Horst , Czechowicz Alexander , Langbein Sven
Published: April 2011

Actuators based on shape memory alloys (SMAs) have been developed to be used only in special applications. Therefore solutions based on SMAs generally cannot be transferred to other tasks. Focusing on the development for special applications has two important disadvantages. Firstly, the effort and costs reach a high level due to the individual development and secondly, for many companies the development of complex SMA-actuators turns out to be an insuperable barrier. Reasons for this are the complex characteristics and the missing simulation and design tools. In order to make statements about the functions and durability of the SMA-component, extensive tests need to be conducted. As a result there is a significant interest in providing SMA-actuator systems with complex and also variable functions. Modular systems allow a transfer to different areas of applications and they also lead to a reduction of variants. Using standardized components is an interesting opportunity to reduce the risk of individual development and the effort for single applications effectively. However, the increased system complexity of conventional modular systems is a problem (additional functions are required, e.g. the mechanical and electrical coupling of the modules). Apart from the conventional form of a modular system there is the possibility of a variable SMA-actuator system generated by standardized SMA-components which can be assembled to a stack system. The existing and unique potential of SMAs for function integration and therefore standardization can be used to its full extent. The aim of this paper is to show an application of such an SMA-actuator in stack design. Besides, the study presents the development process and the control concept of this actuator. An actuator system like this can be used in positioning solutions, for example. The task of this variable SMA-actuator is the conversion of a controller output variable into an exact displacement. The evidence of the realization of simple SMA-based actuators in modular design is provided with the development of this actuator system.
Unpowered Wireless Ultrasound Sensor
Authors: Paramo Daniel , Huang Haiying
Published: April 2011

This paper presents a wireless ultrasound sensor that uses frequency conversion to convert the ultrasound signal to a microwave signal and transmit it directly without digitization. Constructed from a few passive microwave components, the sensor is able to sense, modulate, and transmit the full waveform of ultrasound signals wirelessly without requiring any local power source. The principle of operation of the unpowered wireless ultrasound sensor is described first. Implementation of the sensor and the sensor interrogation unit using commercially-available antennas and microwave components is described in detail. Validation of the sensing system using an ultrasound pitch-catch system and the power analysis model of the system are also presented.
Experimental Analysis of a Cantilever Beam With a Shunted Piezoelectric Periodic Array
Authors: Beck Benjamin S. , Cunefare Kenneth A. , Ruzzene Massimo , Collet Manuel
Published: April 2011

The use of both shunted piezoelectric elements and periodic arrays have been investigated independently as well as used in conjunction to modify the vibration of a system. Piezoelectric patches bonded to a cantilever beam which are shunted with an active circuit, specifically a negative capacitance shunt, can control broadband flexural vibrations of a structure. Also, periodic arrays integrated into a structure allow for modification of propagating waves through the mechanical “stop-bands”. The performance of a combined shunted periodic piezoelectric patch array will be analyzed here by investigating the velocity amplitude of the beam away from the array and in the array section, and the number of control elements in the array.
Fabrication and Characterization of Multiwall Carbon Nanotube Polylactide Fiber Composites
Authors: Tong Lemuel K. W. , Rizvi Reza , Biddiss Elaine , Naguib Hani E.
Published: April 2011

An extrusion melt fiber spinner is proposed for the fabrication of Multiwall Carbon Nanotube (MWNT) Polylactide (PLA) fiber composites. The melt fiber drawing system includes only feed rollers and a draw roller to allow the investigation of as-spun properties of the PLA fibers without the conventional heat treatment. The influence of the drawing parameters on the fiber quality is characterized by measuring the fiber diameters and draw ratios. Preliminary studies demonstrate that orientation and dispersion of MWNTs is feasible with this melt spinner design with improvements on the mechanical and thermal properties. Differential scanning calorimetry (DSC) results show an increase in the rate of cold-crystallization with increasing MWNT loading and tensile tests show that there is an optimal Young’s modulus for 0.5 wt% MWNT loading.
Combined AC and DC Energy Harvesting Methods
Authors: Schlichting Alexander , Tiwari Rashi , Garcia Ephrahim
Published: April 2011

Much of the work on ambient energy harvesting currently focuses on maximizing the efficiency of the power extraction method or increasing the power output. However, an important goal is still out of reach: to produce sufficient and sustained power for wireless sensor nodes and their associated components. Achieving this goal will significantly impact the fields of structural health monitoring, secure location surveillance and a multitude of other pertinent applications. While many energy harvesters can power these electronics with a constant energy source, most ambient sources for desired wireless sensor networks only provide intermittent energy. One method for increasing the robustness and versatility of energy harvesting systems would utilize multiple energy sources simultaneously. In order to achieve this, the problem of effectively combining multiple energy harvesting sources, specifically an AC and a DC source, is thoroughly explored with the experimental analysis of proposed circuit configurations. Also, a multi-source energy harvesting circuit configuration is proposed.
Modeling Bilayer Systems as Electrical Networks
Authors: Creasy M. Austin , Leo Donald J.
Published: April 2011

Bilayers are synthetically made cell membranes that are used to study cell membrane properties or make functional devices that use the properties of the cell membrane components. Lipids and proteins are two of the main components of a cell membrane. Lipids are amphiphilic molecules that can self assemble into organized structures in the presences of water and this self assembly property can be used to form bilayers. Because of the amphiphilic nature of the lipids, a bilayer is impermeable to ion flow. Proteins are the active structures of a cell membrane that opens pores through the membrane for ions and other molecules to pass. Proteins are made from amino acids and have varying properties that depend on its configuration. Some proteins are activated by reactions (chemical, thermal, etc) or gradients induced across the bilayer. One way of testing bilayers to find bilayer properties is to induce a potential gradient across a membrane that induces ion flow and this flow can be measured as an electrical current. But, these pores may be voltage gated or activated by some other stimuli and therefore cannot be modeled as a linear conductor. Usually the conductance of the protein is a nonlinear function of the input that activates the protein. A small system that consists of a single bilayer and protein with few changing components can be easily modeled, but as systems become larger with multiple bilayers, multiple variables, and multiple proteins, the models will become more complex. This paper looks at how to model a system of multiple bilayers and the peptide alamethicin. An analytical expression for this peptide is used to match experimental data and a short study on the sensitivity of the variables is performed.
Quantify Temperature Effects on Crack Size Studies in Metallic Structures Using Vibration-Based Health Monitoring
Authors: Afshari Mana , Butrym Brad A. , Inman Daniel J.
Published: April 2011

This paper examines the vibration-based monitoring technique to quantify the smallest crack size that is detectable in Aluminum beams using piezoceramic excitation and sensing. Having the analytical model of the effect of crack formation on the frequency response of the system, the effect of temperature is also taken into consideration to have a better understanding of the damage effect. The analytical model used in the present work is based on the recent model introduced by Aydin (2008) which is a simplified version of the model used by Khiem et. al. (2001). The beam studied here is assumed to be a uniform Euler-Bernoulli beam having a single fatigue crack and being axially loaded. The crack is treated as a localized reduction in the stiffness and is modeled as a massless rotational spring at the location of the crack, connecting the bisections of the beam. The beam is assumed to be simply supported and subject to a uniform heat flux along the top surface of the beam. For the simplicity in the modeling, it is assumed that the bottom surface of the beam is insulated. The crack is also assumed to be non-breathing during the deformation of the beam. The change in the temperature will alter the modulus of elasticity of the beam and will also cause thermal moments inside the beam which will add terms in both the equation of motion and the boundary conditions of the vibrating beam. First, the effect of temperature on the modulus of elasticity of the beam is studied analytically for different boundary conditions of the beam ends. These modeling results are then compared to the experimental ones. Second, the effect of temperature variation is analytically modeled into the equation of motion of the beam and the boundary conditions. Having the equation of motion of the vibrating beam, the effect of temperature on the frequency response of the beam having a single fatigue crack is studied. Taking into account the effect of temperature on the resonance frequency of the beam will be essential in distinguishing the two effects of damage presence and temperature variation and will be important in quantifying the smallest detectable crack in a structure.
Characterizing of Ionic Polymer-Metal Composites (IPMC) for Sensitive Curvature Measurement
Authors: Bahramzadeh Yousef , Shahinpoor Mohsen
Published: April 2011

Application of Ionic Polymer Metal Composites (IPMCs) for curvature sensing and measurement of dynamic structures has been presented. IPMC’s are electro active polymers that exhibit the characteristics of both actuators and sensors. The flexibility of IPMC makes it possible to be applied both in small and large deflection applications. Developing a curvature sensor based on IPMC can be of high importance in a wide variety of fields including shape monitoring of deployable structures in which the curvature of structure varies during deployment process until it maintains a target curvature. In this article, in order to characterize the IPMC sensor properties for curvature sensing, various experimental procedures have been conducted including sensing response of IPMC sensor to sinusoidal and step deflections at different frequencies. The effect of voltage recovery of IPMC on sensing signal was studied by applying the deformation in the form of ramp functions at very slow rates of curvature variation. Experiments show that due to the linear response of IPMC sensor to curvature change at different rates, it could be potentially used as a sensitive curvature sensor for several structural applications.
Influence of DC Voltage Bias on the Converse Magnetoelectric Effect Response in PZT/Terfenol-D/PZT Laminate Composites
Authors: Hockel Joshua L. , Wu Tao , Carman Gregory P.
Published: April 2011

The converse magnetoelectric effect (CME) response of a Pb(Zr0.52Ti0.48)O3 (PZT)/ Tb0.30Dy0.7Fe2 (Terfenol-D)/PZT laminate to applied DC voltage bias has been investigated. Experimental data demonstrates that the CME coefficient αCME is highly dependent on applied voltage bias. The voltage bias is shown to increase the piezomagnetic coefficient δλ/δB of the Terfenol-D and by extension the αCME, however an optimal αCME has yet to be identified. The ME laminate exhibits considerable gains in αCME (up to 100%) due in part to the improved magnetostrictive response of Terfenol-D under piezoelectric-induced mechanical stress.
Low Frequency Piezoelectric Synthetic Jets
Authors: Seeley Charles E. , Arik Mehmet , Uttukar Yogen , Icoz Tunc
Published: April 2011

Active cooling is often required for circuit boards with high heat generation densities. Synthetic jets driven with piezoelectric actuators offer interesting capabilities for localized active cooling of electronics due to their compact size, low cost and substantial cooling effectiveness. The design of synthetic jets for specific applications requires practical design tools that capture the strong fluid structure interaction without long run times. There is particular interest in synthetic jets that have a low operating frequency to reduce noise levels. This paper describes how common finite element (FE) and computational fluid dynamics (CFD) codes can be used to calculate parameters for a synthetic jet fluid structure interaction (FSI) model that only requires a limited number of degrees of freedom and is solved using a direct approach for low frequency synthetic jets. Tests are performed based on impinging on a heated surface to measure heat transfer enhancement. The test results are compared to the FSI model results for validation and agreement is found to be good in the frequency range of interest from 200 to 500 Hz.
Validation and Characterization of an Acoustic Sensor Based on PVDF Micropillars and Patterned Electrodes
Authors: Xu Jian , Dapino Marcelo J. , Gallego-Perez Daniel , Hansford Derek
Published: April 2011

This paper addresses the fabrication, validation, and characterization of a millimeter-size acoustic sensor consisting of Polyvinylidene Fluoride (PVDF) micropillars and patterned electrodes. The sensor takes advantage of two key design principles: stress amplification through the area ratio between the overall surface exposed to acoustic waves and the area of the individual micropillars, and patterned electrodes which reduce the capacitance of the sensor by excluding the capacitance of the air between micropillars. In combination, these design principles enable a sensor capable of achieving 100× the sensitivity of flat PVDF film. A sensitivity analysis is presented and sensor fabrication details are described. An experimental setup was developed to characterize the sensor against a reference microphone. A signal conditioning circuit including a preamplifier circuit and a notch filter was designed and constructed. Sensitivity calibration tests show that a micropillar array with a gap ratio of 5.82 exhibits a stress constant g33 = −19.93 V/m/Pa, which is 60.39 times greater than the stress constant of commercial PVDF film. Experimental results also show that the sensitivity of the sensor is in close agreement with theory, thus confirming the performance advantages of the micropillar sensor.
BATMAV: Development and Testing of a SMA-Based Bio-Inspired Flapping Platform
Authors: Bunget Gheorghe , Seelecke Stefan
Published: April 2011

The overall objective of the BATMAV project is the development of a biologically-inspired Micro Aerial Vehicle (MAV) with flexible and foldable wings for flapping flight. This paper presents a platform that features bat-inspired wings which are able to mimic the folding motion of the elbow and wrist joints of the natural flyer. This flapping platform makes use of the dual roll of the Shape Memory Alloys (SMA) to mimic the flexible joints and flapping muscles of the natural wings. The approach of this project was to learn from the natural flyer through a systematic analysis of their flight and to mimic their flapping mechanisms. A systematic study of the bat flight kinematics helped to identify the required joint angles as relevant degrees of freedom for wing actuation. Kinematic models of wings with 2 and 3-DOFs have been developed with the intention of mimicking the wing trajectories of the natural flier Plecotus auritus. A further kinematic model for the joint rotation angle has been developed in order to determine the attachment locations of SMA ‘muscle-wires’ as well as their routes along the wing ‘bones’. As part of this study individual elbow-joint systems were designed, fabricated and used to experimentally validate the above model’s prediction. The elastic skin membrane of the bat wing has been reproduced using a thin-film silicon membrane which has been suitably prestrained and shaped to mimic the leading and trailing edges of the bat wing. To measure the aerodynamic forces developed by the flapping platform, a test stand consisting of two load cells was assembled, and the dynamic tests were performed for a 2-DOF flapping wings. The lift and thrust forces as well as the flapping amplitude were measured.
Analysis of Fiber Bragg Grating Spectral Features for In-Situ Assessment of Sandwich Composites
Authors: Hackney Drew , Webb Sean , Peters Kara
Published: April 2011

In this paper we summarize recent advances derived from full-spectral interrogation of FBG sensors for structural health monitoring and damage identification in composites. Previous work has correlated signals from FBG reflected spectra to stress concentrations near crack tips, curing conditions during processing of composite laminates and the progression of delamination due to multiple low-velocity impacts in woven composite laminates. In this paper we investigate the information gained from FBG sensors embedded at the facesheet-core interface in foam-core sandwich composites subjected to low-velocity impact loading. We also discuss recent advances in interrogation systems for these sensors which will permit dynamic evaluation of these parameters. These results demonstrate the richness of information that can be obtained from full-spectral interrogation of FBG sensors in a complex, multiple stress component environment.
Adaptive Control of a Sliding Seat Using Magnetorheological Energy Absorbers
Authors: Mao Min , Wereley Norman M. , Browne Alan L.
Published: April 2011

Feasibility of a sliding seat utilizing adaptive control of a magnetorheological (MR) energy absorber (MREA) to minimize loads imparted to a payload mass in a ground vehicle for frontal impact speeds as high as 7 m/s (15.7 mph) is investigated. The crash pulse for a given impact speed was assumed to be a rectangular deceleration pulse having a prescribed magnitude and duration. The adaptive control objective is to bring the payload (occupant plus seat) mass to a stop using the available stroke, while simultaneously accommodating changes in impact velocity and occupant mass ranging from a 5th percentile female to a 95th percentile male. The payload is first treated as a single-degree-of-freedom (SDOF) rigid lumped mass, and two adaptive control algorithms are developed: (1) constant Bingham number control, and (2) constant force control. To explore the effects of occupant compliance on adaptive controller performance, a multi-degree-of-freedom (MDOF) lumped mass biodynamic occupant model was integrated with the seat mass. The same controllers were used for both the SDOF and MDOF cases based on SDOF controller analysis because the biodynamic degrees of freedom are neither controllable nor observable. The designed adaptive controllers successfully controlled load-stroke profiles to bring payload mass to rest in the available stroke and reduced payload decelerations. Analysis showed extensive coupling between the seat structures and occupant biodynamic response, although minor adjustments to the control gains enabled full use of the available stroke.
Actuators for Smart Applications
Authors: Paternoster Alexandre , de Boer Andre , Loendersloot Richard , Akkerman Remko
Published: April 2011

Actuator manufacturers are developing promising technologies which meet high requirements in performance, weight and power consumption. Conventionally, actuators are characterized by their displacement and load performance. This hides the dynamic aspects of those actuation solutions. Work per weight performed by an actuation mechanism and the time needed to develop this mechanical energy are by far more relevant figures. Based on these figures, a selection process was developed. With time and energy constraints, it highlights the most weight efficient actuators. This process has been applied to the Gurney flap technology used as a morphing concept for rotor-blades. Three control schemes were considered and simulations were performed to investigate the mechanical work required. It brought forward piezoelectric stack actuators as the most effective solution in the case of an actively controlled rotorblade. The generic nature of the procedure allows to use it for a wide range of applications.
Metal-Core Piezoelectric Fibers for the Detection of Lamb Waves
Authors: Liu Jian , Qiu Jinhao , Chang Weijie , Ji Hongli , Zhu Kongjun
Published: April 2011

Metal-core piezoelectric fiber (MPF) is a new type of piezoelectric ceramic device with small size, and has great potential to be used as structurally integrated transducers for guided-wave (GW) structural health monitoring. This paper focuses on the use of MPF as ultrasonic Lamb wave receivers. First, the MPF sensor voltage response is derived by coupling the direct piezoelectric effect to the wave strain field excited by circular crested actuator. The obtained theoretical result is validated on an aluminum plate. Furthermore, the experiment that compares the MPF response to Lamb wave with the PZT response is performed. The results show that MPF sensors can be used to sense Lamb waves clearly. In the end, the directivity of MPF response to Lamb waves was investigated, and another experiment is performed to examine the directivity of MPF response to Lamb waves. The result shows that MPF has high directivity, which can be exploited to triangulate the location of an ultrasound source without prior knowledge of the wave velocity in the medium.
Effect of oxygen deficiency on the photoresponse and reactivity of mixed phase titania thin films
Authors: DeSario Paul A. , Chen Le , Graham Michael E. , Gray Kimberly A.
Published: April 2011

Nonstoichiometric mixed phased titania nanocomposites (TiO2−x) were deposited by reactive direct current magnetron sputtering. The authors explored the role of nonstoichiometry (as defined by oxygen deficiency in synthesis) in mixed phase titania thin films and its effects on the photoresponse and photocatalytic performance for CO2 reduction to methane under UV and visible light. Oxygen partial pressure was varied during film deposition, yielding different levels of oxygen deficiency in the films. Optimized nonstoichiometric films showed a strong redshift. The authors have identified an optimum set of synthesis conditions for TiO2−x films that produce a relative maximum in photocatalytically produced methane under both UV and visible light.
An analysis of the effects of electrical field interaction with an acoustic model of cochlear implants
Authors: Strydom Trudie , Hanekom Johan J.
Published: April 2011

Electrical field interaction caused by current spread in a cochlear implant was modeled in an explicit way in an acoustic model (the SPREAD model) presented to six listeners with normal hearing. The typical processing of cochlear implants was modeled more closely than in traditional acoustic models by careful selection of parameters related to current spread or parameters that could amplify the electrical field interactions caused by current spread. These parameters were the insertion depth, electrode spacing, electrical dynamic range, and dynamic range compression function. The hypothesis was that current spread could account for the asymptote in performance in speech intelligibility experiments observed at around seven stimulation channels in a number of cochlear implant studies. Speech intelligibility for sentences, vowels, and consonants at three noise levels (SNR of +15 dB, +10 dB, and +5 dB) was measured as a function of the number of spectral channels (4, 7, and 16). The SPREAD model appears to explain the asymptote in speech intelligibility at seven channels for all noise levels for all speech material used in this study. It is shown that the compressive amplitude mapping used in cochlear implants can have a detrimental effect on the number of effective channels.
A mathematical model of medial consonant identification by cochlear implant users
Authors: Svirsky Mario A. , Sagi Elad , Meyer Ted A. , Kaiser Adam R. , Teoh Su Wooi
Published: April 2011

The multidimensional phoneme identification model is applied to consonant confusion matrices obtained from 28 postlingually deafened cochlear implant users. This model predicts consonant matrices based on these subjects’ ability to discriminate a set of postulated spectral, temporal, and amplitude speech cues as presented to them by their device. The model produced confusion matrices that matched many aspects of individual subjects’ consonant matrices, including information transfer for the voicing, manner, and place features, despite individual differences in age at implantation, implant experience, device and stimulation strategy used, as well as overall consonant identification level. The model was able to match the general pattern of errors between consonants, but not the full complexity of all consonant errors made by each individual. The present study represents an important first step in developing a model that can be used to test specific hypotheses about the mechanisms cochlear implant users employ to understand speech.
Transmission loss measurement of acoustic material using time-domain pulse-separation method (L)
Authors: Sun Liang , Hou Hong
Published: April 2011

An alternative method for measuring the normal incidence sound transmission loss (nSTL) is presented in this paper based on the time-domain separation of so-called Butterworth pulse with a short-duration time about 1 ms in a standing wave tube. During the generation process of the pulse, inverse filter principle was adopted to compensate the loudspeaker response, besides this, the effect of the characteristics of tube termination can be eliminated through the generation process of the pulse so as to obtain a single plane pulse wave in the standing wave tube which makes the nSTL measurement very simple. A polyurethane foam material with low transmission loss and a kind of rubber material with relatively high transmission loss are used to verify the proposed method. When compared with the traditional two-load method, a relatively good agreement between these two methods can be observed. The main error of this method results from the measuring accuracy of the amplitude of transmission coefficient.
Delay and Doppler spreads in underwater acoustic particle velocity channels
Authors: Guo Huaihai , Abdi Ali , Song Aijun , Badiey Mohsen
Published: April 2011

Signal processing and communication in acoustic particle velocity channels using vector sensors are of interest in the underwater medium. Due to the presence of multiple propagation paths, a mobile receiver collects the signal with different delays and Doppler shifts. This introduces certain delay and Doppler spreads in particle velocity channels. In this paper, these channel spreads are characterized using the zero-crossing rates of channel responses in frequency and time domain. Useful expressions for delay and Doppler spreads are derived in terms of the key channel parameters mean angle of arrival and angle spread. These results are needed for design and performance prediction of systems that utilize underwater acoustic particle velocity and pressure channels.
Trends in aircraft noise annoyance: The role of study and sample characteristics
Authors: Janssen Sabine A. , Vos Henk , van Kempen Elise E. M. M. , Breugelmans Oscar R. P. , Miedema Henk M. E.
Published: April 2011

Recently, it has been suggested that the annoyance of residents at a given aircraft noise exposure level increases over the years. The objective of the present study was to verify the hypothesized trend and to identify its possible causes. To this end, the large database used to establish earlier exposure–response relationships on aircraft noise was updated with original data from several recent surveys, yielding a database with data from 34 separate airports. Multilevel grouped regression was used to determine the annoyance response per airport, after which meta-regression was used to investigate whether study characteristics could explain the heterogeneity in annoyance response between airports. A significant increase over the years was observed in annoyance at a given level of aircraft noise exposure. Furthermore, the type of annoyance scale, the type of contact, and the response percentage were found to be sources of heterogeneity. Of these, only the scale factor could statistically account for the trend, although other findings rule it out as a satisfactory explanation. No evidence was found for increased self-reported noise sensitivity. The results are of importance to the applicability of current exposure–annoyance relationships for aircraft noise and provide a basis for decisions on whether these need to be updated.
Changes in amplitude and phase of distortion-product otoacoustic emission fine-structure and separated components during efferent activation
Authors: Henin Simon , Thompson Suzanne , Abdelrazeq Shukrallah , Long Glenis R.
Published: April 2011

Medial olivocochlear (MOC) efferent fibers synapse directly on the outer hair cells (OHCs). Efferent activation evoked by contralateral acoustic stimulation (CAS) will affect OHC amplification and subsequent measures of distortion-product otoacoustic emissions (DPOAEs). The aim of this study was to investigate measures of total and separated DPOAEs during efferent activation. Efferent activation produces both suppression and enhancement of the total DPOAE level. Level enhancements occurred near fine-structure minima and were associated with consistent MOC evoked upward shifts in DPOAE fine-structure frequency. Examination of the phase of the separated components revealed that frequency shifts stemmed from increasing phase leads of the reflection component during CAS, while the generator component phase was nearly invariant. Separation of the two DPOAE components responsible for the fine-structure revealed more consistent reduction of the levels of both components. Using vector subtraction (which takes into account both level and phase) to estimate the changes in the unseparated DPOAE provided consistent evidence of DPOAE suppression. Including phase information provided a more sensitive, valid and consistent estimate of CAS function even if one does not know the position of the DPOAE in the fine-structure.
Auditory discrimination of force of impact
Authors: Lutfi Robert A. , Liu Ching-Ju , Stoelinga Christophe N. J.
Published: April 2011

The auditory discrimination of force of impact was measured for three groups of listeners using sounds synthesized according to first-order equations of motion for the homogenous, isotropic bar [Morse and Ingard (1968). Theoretical Acoustics pp. 175–191]. The three groups were professional percussionists, nonmusicians, and individuals recruited from the general population without regard to musical background. In the two-interval, forced-choice procedure, listeners chose the sound corresponding to the greater force of impact as the length of the bar varied from one presentation to the next. From the equations of motion, a maximum-likelihood test for the task was determined to be of the form Δlog A + αΔ log f > 0, where A and f are the amplitude and frequency of any one partial and α = 0.5. Relative decision weights on Δ log f were obtained from the trial-by-trial responses of listeners and compared to α. Percussionists generally outperformed the other groups; however, the obtained decision weights of all listeners deviated significantly from α and showed variability within groups far in excess of the variability associated with replication. Providing correct feedback after each trial had little effect on the decision weights. The variability in these measures was comparable to that seen in studies involving the auditory discrimination of other source attributes.
Material parameter computation for multi-layered vocal fold models
Authors: Schmidt Bastian , Stingl Michael , Leugering Günter , Berry David A. , Döllinger Michael
Published: April 2011

Today, the prevention and treatment of voice disorders is an ever-increasing health concern. Since many occupations rely on verbal communication, vocal health is necessary just to maintain one’s livelihood. Commonly applied models to study vocal fold vibrations and air flow distributions are self sustained physical models of the larynx composed of artificial silicone vocal folds. Choosing appropriate mechanical parameters for these vocal fold models while considering simplifications due to manufacturing restrictions is difficult but crucial for achieving realistic behavior. In the present work, a combination of experimental and numerical approaches to compute material parameters for synthetic vocal fold models is presented. The material parameters are derived from deformation behaviors of excised human larynges. The resulting deformations are used as reference displacements for a tracking functional to be optimized. Material optimization was applied to three-dimensional vocal fold models based on isotropic and transverse-isotropic material laws, considering both a layered model with homogeneous material properties on each layer and an inhomogeneous model. The best results exhibited a transversal-isotropic inhomogeneous (i.e., not producible) model. For the homogeneous model (three layers), the transversal-isotropic material parameters were also computed for each layer yielding deformations similar to the measured human vocal fold deformations.
On the difference between negative damping and eigenmode synchronization as two phonation onset mechanisms
Authors: Zhang Zhaoyan
Published: April 2011

Negative damping and eigenmode synchronization as two different mechanisms of phonation onset are distinguished. Although both mechanisms lead to a favorable phase relationship between the flow pressure and the vocal fold motion as required for a net energy transfer into the vocal folds, the underlying mechanisms for this favorable phase relationship are different. The negative damping mechanism relies on glottal aerodynamics or acoustics to establish before onset and maintain after onset the favorable phase relationship, and therefore has minimum requirements on vocal fold geometry and biomechanics. A single degree-of-freedom vocal fold model is all that is needed for self-oscillation in the presence of a negative damping mechanism. In contrast, the mechanism of eigenmode synchronization critically depends on the geometrical and biomechanical properties of the vocal folds (at least 2-degrees-of-freedom are required), and has little requirement on the glottal aerodynamics other than flow separation. The favorable phase relation is established once synchronization occurs, regardless of the phase relationship imposed by glottal aerodynamics before onset. Unlike that of the negative damping mechanism, initiation of eigenmode synchronization requires neither a velocity-dependent flow pressure nor an alternating convergent-divergent glottis. The clinical implications of the distinctions between these two mechanisms are discussed.
The prioritization of voice fundamental frequency or formants in listeners’ assessments of speaker size, masculinity, and attractiveness
Authors: Pisanski Katarzyna , Rendall Drew
Published: April 2011

Key features of the voice—fundamental frequency (F0) and formant frequencies (Fn)—can vary extensively among individuals. Some of this variation might cue fitness-related, biosocial dimensions of speakers. Three experiments tested the independent, joint and relative effects of F0 and Fn on listeners’ assessments of the body size, masculinity (or femininity), and attractiveness of male and female speakers. Experiment 1 replicated previous findings concerning the joint and independent effects of F0 and Fn on these assessments. Experiment 2 established frequency discrimination thresholds (or just-noticeable differences, JND’s) for both vocal features to use in subsequent tests of their relative salience. JND’s for F0 and Fn were consistent in the range of 5%–6% for each sex. Experiment 3 put the two voice features in conflict by equally discriminable amounts and found that listeners consistently tracked Fn over F0 in rating all three dimensions. Several non-exclusive possibilities for this outcome are considered, including that voice Fn provides more reliable cues to one or more dimensions and that listeners’ assessments of the different dimensions are partially interdependent. Results highlight the value of first establishing JND’s for discrimination of specific features of natural voices in future work examining their effects on voice-based social judgments.
Prediction of optimal conditions for verbal-communication quality in eating establishments
Authors: Nahid Musarrat , Hodgson Murray
Published: April 2011

This paper discusses the prediction of verbal-communication quality in eating establishments (EEs). EEs contain talkers and listeners who require high speech intelligibility at their tables, and high speech privacy between tables. Using catt-Acoustic, verbal-communication quality—quantified by speech transmission index (STI)—in models of three existing EEs was predicted. Talker voice-output levels were predicted using an existing empirical model accounting for the Lombard effect. With these, catt-Acoustic predicted impulse responses, speech levels and noise levels at primary and secondary listener positions, and the corresponding STIs. The untreated EEs were first modeled for various talker and listener positions, and occupancies. Then various treated configurations, involving reduced volume, increased absorption and barriers were studied to determine the effectiveness of the treatments. The results suggest that placing barriers around tables can be an effective way to achieve good verbal-communication quality. Increasing the absorption of the room surfaces or decreasing the ceiling height to control reverberation may not be effective. However, increasing the surface absorption and putting barriers around tables may achieve optimal speech conditions in EEs. Subdividing large EEs into smaller ones can also be effective.
Virtual sensors for active noise control in acoustic-structural coupled enclosures using structural sensing: Part II—Optimization of structural sensor placement
Authors: Halim Dunant , Cheng Li , Su Zhongqing
Published: April 2011

The work proposed an optimization approach for structural sensor placement to improve the performance of vibro-acoustic virtual sensor for active noise control applications. The vibro-acoustic virtual sensor was designed to estimate the interior sound pressure of an acoustic-structural coupled enclosure using structural sensors. A spectral-spatial performance metric was proposed, which was used to quantify the averaged structural sensor output energy of a vibro-acoustic system excited by a spatially varying point source. It was shown that (i) the overall virtual sensing error energy was contributed additively by the modal virtual sensing error and the measurement noise energy; (ii) each of the modal virtual sensing error system was contributed by both the modal observability levels for the structural sensing and the target acoustic virtual sensing; and further (iii) the strength of each modal observability level was influenced by the modal coupling and resonance frequencies of the associated uncoupled structural/cavity modes. An optimal design of structural sensor placement was proposed to achieve sufficiently high modal observability levels for certain important panel- and cavity-controlled modes. Numerical analysis on a panel-cavity system demonstrated the importance of structural sensor placement on virtual sensing and active noise control performance, particularly for cavity-controlled modes.
Anomalous waveforms observed in laboratory-formed gas hydrate-bearing and ice-bearing sediments
Authors: Lee Myung W. , Waite William F.
Published: April 2011

Acoustic transmission measurements of compressional, P, and shear, S, wave velocities rely on correctly identifying the P- and S-body wave arrivals in the measured waveform. In cylindrical samples for which the sample is much longer than the acoustic wavelength, these body waves can be obscured by high-amplitude waveform features arriving just after the relatively small-amplitude P-body wave. In this study, a normal mode approach is used to analyze this type of waveform, observed in sediment containing gas hydrate or ice. This analysis extends an existing normal-mode waveform propagation theory by including the effects of the confining medium surrounding the sample, and provides guidelines for estimating S-wave velocities from waveforms containing multiple large-amplitude arrivals.
Vocal effort with changing talker-to-listener distance in different acoustic environments
Authors: Pelegrín-García David , Smits Bertrand , Brunskog Jonas , Jeong Cheol-Ho
Published: April 2011

Talkers adjust their vocal effort to communicate at different distances, aiming to compensate for the sound propagation losses. The present paper studies the influence of four acoustically different rooms on the speech produced by 13 male talkers addressing a listener at four distances. Talkers raised their vocal intensity by between 1.3 and 2.2 dB per double distance to the listener and lowered it as a linear function of the quantity “room gain” at a rate of −3.6 dB/dB. There were also significant variations in the mean fundamental frequency, both across distance (3.8 Hz per double distance) and among environments (4.3 Hz), and in the long-term standard deviation of the fundamental frequency among rooms (4 Hz). In the most uncomfortable rooms to speak in, talkers prolonged the voiced segments of the speech they produced, either as a side-effect of increased vocal intensity or in order to compensate for a decrease in speech intelligibility.
Retrieval of Green’s function and generalized optical theorem for the scattering of complete dyadic fields
Authors: Lu Laiyu , Ding Zhifeng , Zeng Rong Sheng , He Zhengqin
Published: April 2011

Green’s function retrieval has been widely used in different research fields due to the fact that the Green’s function can be extracted by cross-correlating the records at two receivers. In this paper, the retrieval of the dyadic Green’s function is studied by investigating the representation theorem. The generalized optical theorem for the dyadic fields is derived based on the elastic dynamic interferometric equation. By addressing the cross-correlation recorded at two receivers, the important role of the generalized optical theorem and energy equipartition in retrieving the exact Green’s function is shown. The presented derivation also shows the Newton–Marchenko equation holdsif the condition of equipartition is not satisfied.
Improving beampatterns of two-dimensional random arrays using convex optimization
Authors: Gerstoft Peter , Hodgkiss William S.
Published: April 2011

Sensors are becoming ubiquitous and can be combined in arrays for source localization purposes. If classical conventional beamforming is used, then random arrays have poor beampatterns. By pre-computing sensor weights, these beampatterns can be improved significantly. The problem is formulated in the frequency domain as a desired look direction, a frequency-independent transition region, and the power minimized in a rejection-region. Using this formulation, the frequency-dependent sensor weights can be obtained using convex optimization. Since the weights are data independent they can be pre-computed, the beamforming has similar computational complexity as conventional beamforming. The approach is demonstrated for real 2D arrays.