bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling room impulse response via composites of spatial-temporal Gaussian processes
Authors: Komatsu Tatsuya , Peters Gareth W. , Matsui Tomoko , Nevat Ido , Takeda Kazuya
Published: May 2013

We develop a novel algorithm to estimate a spatial-temporal transfer function of a time-domain room impulse response for reverberation in closed environments. This novel approach involves developing two non-parametric models, one for the early phase and the other for the late phase for reverberation. These models are based on a composite of two Gaussian Process (GP) structures. We also investigate the impact of the choice of spatial and temporal kernels on the estimation and prediction performance. The proposed algorithm incorporates as a special case the widely utilized exponentially decaying model and also extends this model structure within the GP setting to more advanced spatial-temporal structures suitable to perform estimation of the reverberant transfer function. The performance of the proposed algorithm is evaluated in a real environment using nine spatially distributed microphones. The microphones collect reverberant response from a directional speaker allowing observation of noisy realizations of the impulse response to reverberate during early and late stages. We compare the performance of our algorithm with a 3D spatial-temporal cubic interpolation algorithm and show that the proposed algorithm provides equal or better performance than the cubic interpolation.
Large-scale sound field rendering with graphics processing unit cluster for three-dimensional audio with loudspeaker array
Authors: Tsuchiya Takao , Iwaya Yukio , Otani Makoto
Published: May 2013

The sound field rendering is a technique to simulate the sound field from the three-dimensional numerical models constructed in the computer, and it is the same concept as the graphics rendering in the computer graphics. In this paper, a graphics processing unit (GPU) cluster system is applied to the sound field rendering for a large room simulation. The compact explicit finite difference time domain (CE-FDTD) method is implemented on the GPU cluster system. The CE-FDTD method is a kind of the finite difference method in which the wave equation is directly discretized based on the central differences. The developed GPU cluster system consists of eight PC nodes in which four GPUs are mounted respectively. The rendering results are reproduced by a speaker array system in which 157 speakers surround a small room. The sound field renderings are performed for a large room with a volume capacity of about 5000 cubic meters, in which the impulse responses of one-second length with a sampling rate of 40 kHz are calculated at 157 points corresponding to the loudspeaker positions. The impulse responses are then convoluted with dry music sources. The sound field rendering with the 157ch loudspeaker array system provides the realistic sound field reproduction with natural reverberation.
Acoustic characterization of three archeological sites in the state of Guanajuato, Mexico
Authors: Ramos-Amezquita Alejandro , Ibarra-Zarate David I.
Published: May 2013

The present work shows the results obtained in collaboration with the government of the state of Guanajuato in Mexico in a project that looked to include the acoustical analysis of Archaeological sites as a tool for gathering information regarding the historical social use of the areas in question. To that end, the acoustical characterization of 3 archaeological sites recently opened to the public in the state was in order: Cañada de la Virgen, Peralta and Plazuelas. Results include the 3D modeling of the areas of interest and the simulation of the acoustic response of them using the software EASE. Specific acoustic parameters were extracted from the simulations and then analyzed in comparison to archeological hypothesis of the use of such spaces as areas of public appearances, performance, ethno-musicological reports on the type and use of musical instruments, and other archaeological findings in the area in order to support or disprove such hypothesis.
Basic study on discrimination between sound fields of architectural spaces
Authors: Katoh Maya , Terashima Takane
Published: May 2013

Many objective criteria by attenuation property of room acoustic energy have been suggested, and relationships with subjective attributes have been elucidated. The difference of synthetic subjective impression between sound fields could be discriminated by acoustical parameters, i.e., objective criteria above, but details of mechanism in discrimination among different sound fields, weightings or ground of judgment, etc. have not been clarified. The purpose of this study is to clarify the discrimination factor over difference between sound fields. In this report, subjective experiments are carried out by using impulse response data of existing ten concert halls and music data, made from convolution of impulse responses and dry sources, as stimuli. In these experiments, subjects are asked to evaluate the impression of each stimulus, and to judge the difference among stimuli in pared comparison. The results of these experiments are analyzed and it seems that the factor related to the difference of Reverberance is dominant in discrimination by factor analysis, but there are some cases in which Loudness or Clarity is dominant. The weightings of factors, the boundary to switch judgment between factors, etc. will be discussed.
Effect of visual information on subjective impression for sound field in architectural space
Authors: Wani Yuko , Terashima Takane , Tokunaga Yasunobu
Published: May 2013

In architectural and urban space, we are always exposed to multimodal stimuli of visual information and sound fields in various scenes of everyday life. The purpose of this study is to clarify relationship of subjective impression of vision and auditory, and acquire knowledge which contributes to architectural design or acoustic design. In this report, two following experiments are carried out in which subjects are presented with sound fields by real time convolution as auditory stimuli and panoramic VR images of 360 interactive views of interior as visual stimuli. (1) Comparison between subjective responses for single or multi modal presentations of visual and auditory stimuli from various architectural spaces. (2) Comparison between subjective responses for various combinations of multi modal presentations of visual and auditory stimuli from various architectural spaces. Analysis for results of these experiments clarify the influence of visual information upon the subjective impression for sound field and mutual relationship between subjective impression of vision and auditory of interior of buildings. It is already found that visual information significantly effects subjective impression for sound field by experiment 1, and the details of relationship between elements of visual information and parameters of sound field will be clarified by experiment 2.
Research on a kind of low-frequency broadband cross-dipole projector
Authors: Yuyu Dai , Penglai Xin , Xiuming Wang , Hongbin He
Published: May 2013

The finite element method (FEM) is used to simulate a low-frequency broadband cross-dipole projector based on trilaminar bender bar in this paper. In the simulated model, four long trilaminar bender bars and four short trilaminar bender bars are attached on a skeleton two form two square arrays, and very array excite two different response frequencies. The four response frequencies distribute on the range from 400 Hz to 5 kHz to reach broadband exciting. Finally, a sample is fabricated, and test in an anechoic tank, it is shown that the test result meet the simulated result very well.
Modeling sound fields from radially symmetric impulsive planar sources using Rayleigh's Integral
Authors: Warshaw Stephen I.
Published: May 2013

The evaluation of Rayleigh's integral in cases where the integrand contains delta functions with time-dependent arguments provides a highly useful and easily implemented vehicle for modeling and understanding the radiation of impulsive sound waves from planar sources. We present elementary examples of such calculations and show their application in various realistic scenarios, including the radiation of impulsive aeroacoustic sound from buried explosions and potential extensions to lithotripsy. In this paper, we represent the surface motions of a planar radiating source as delta functions of radially expanding or contracting arguments with easily specified geometrical parameters, and present model near-field to far-field calculations of the launched sound waves using analytic and numerical integration. We show that significant features in these traveling impulses can easily be related to the details of the kinematic history of the planar source. We restrict our purview to the time domain and to radial symmetry; frequency analyses and azimuthally asymmetric motions will not be considered.
Influence of reflecting walls on edge diffraction simulation in geometrical acoustics
Authors: Pohl Alexander , Schröder Dirk , Stephenson Uwe M. , Svensson U. Peter
Published: May 2013

Edge diffraction can be introduced into geometrical acoustics mainly by three models: detour-based, energetic and wave-based diffraction models. In the past, we thoroughly compared Maekawa's detour law, the uncertainty relation based diffraction method and the secondary source model by the example of edge diffraction of a single wedge. However, the influence of the wedge shape has not yet been analyzed. Therefore, we consequently study in this contribution the influence of the wedge's faces. This is analyzed by varying both the faces’ reflection properties and their opening angle. This is extended to the crucial case of approximately parallel faces (inner angle, e.g., 179°), where diffraction is physically neglectable, but computationally problematic for the uncertainty based diffraction method. Additionally, wedges are placed on an infinitely long surface. Therewith, we can analyze the floor reflections’ impact on the sound field behind the wedge by varying both their absorption and scattering coefficients. Furthermore, we discuss artifacts which can arise in the uncertainty based diffraction model due to arbitrary positioning of diffraction planes, so called “transparent walls.” Finally, we discuss the advantages and disadvantages of the presented methods.
Acoustic response of a buried landmine with a low grazing-angle source array, focused on the ground
Authors: Copenhaver Benjamin J. , Gorhum Justin D. , Slack Charles M. , Barlett Martin , Muir Thomas G. , Hamilton Mark F.
Published: May 2013

An array of 16 loudspeakers, deployed along a segment of the base of a right circular cone, was used to focus intense tone bursts at low audio frequencies on a soil, with and without a buried target, having a compliant lid. The response of the target site was examined as a function of source frequency, intensity level, and excitation signal type, including multi-tone radiations. Nonlinear interaction to produce sum and difference frequencies at the target site was examined and compared with observations of Korman and Sabatier [J. Acoust. Soc. Am. 116, 3354 (2004)]. [Work supported by the ARL:UT McKinney Fellowship in Acoustics.]
Impact of dynamic binaural signal associated with listener's voluntary movement in auditory spatial perception
Authors: Hirahara Tatsuya , Yoshisaki Daisuke , Morikawa Daisuke
Published: May 2013

The effect of listener's voluntary movement on the horizontal sound localization was investigated using a binaural recording/reproduction system with TeleHead, a steerable dummy head. Stimuli were static binaural signals recorded with a still dummy-head in head-still condition, dynamic binaural signals recorded with a dummy-head that followed precise or modified listener's head rotation, dynamic binaural signals produced by steering-wheel rotation with listener's hands in head-still condition, and dynamic binaural signals produced by an experimenter in head-still condition. For the static binaural signals, some were localized within the head and the front-back errors often occurred. For the dynamic binaural signals, none of them was localized within the head, and the front-back confusions seldom occurred. Sound images of the dynamic binaural stimuli produced by head rotation were localized out-of head, while those produced by the steering-wheel rotation or by an experimenter were moving around the listener's head. Listeners could judge the orientation of each stimulus more correctly with dynamic binaural signals produced by listener's head or steering-wheel rotation than with static binaural signals and with dynamic binaural signals produced by an experimenter. Results suggest that the dynamic binaural signal associated with listener's voluntary movement play crucial role in sound localization.
Broadband acoustic metamaterials with electro-magnetically controlled properties
Authors: Donskoy Dimitri , Malinovsky Vladimir
Published: May 2013

The proposed class of acoustic metamaterials utilizes clouds of electrically charged nano or micro particles exposed to an external magnetic field. The particles are also elastically supported or embedded into elastically compliant medium in a way that the designed structure exhibits two resonances: mechanical spring-mass resonance and electro-magnetic cyclotron resonance. It is shown that if the cyclotron frequency is greater than the mechanical resonance frequency, the designed structure could be highly attenuative (40–60 dB) for vibration and sound waves in a very broad frequency range covering low and very low frequencies. The approach opens up wide range of opportunities for design of adaptive acoustic metamaterials by controlling magnetic field and/or electrical charges.
Broadband directional ultrasound propagation using sonic crystal and nonlinear medium
Authors: Sinha Dipen N. , Pantea Cristian
Published: May 2013

The development of a passive, sonic crystal-based device with unusual properties will be reported. This device combines a 1D sonic crystal, a nonlinear medium, and an acoustic low pass filter to allow broadband ultrasound propagation as a collimated beam for specialized underwater communication. The signal to be transmitted is first amplitude modulated with a high-frequency ultrasonic carrier wave and applied to one side of the device. The device then demodulates this signal and the original low frequency signal appears as a collimated beam on the other side. The sonic crystal provides a band pass acoustic filter through which the high-frequency ultrasonic signal can pass through and the nonlinear medium then demodulates the signal and also generates the low frequency sound beam through the parametric array concept. The low pass filter removes any remaining high frequency components. The device also functions in a unidirectional manner. Design details of the device and experimental data will be presented.
Equations for energy characteristics of oscillatory systems with internal (hidden) degrees of freedom and application to acoustic metamaterials
Authors: Bobrovnitskii Yuri
Published: May 2013

General equations are derived for calculating the kinetic and potential energies and other energy characteristics of linear oscillatory NDOF-systems a portion of DOFs of which are internal or inaccessible for measurement and excluded from consideration. The energy characteristics are expressed through parameters pertaining only to the input or accessible DOFs. The equations are based on the certain novel properties of the so-called Shur matrix complement. The theory is applied to calculating the energy characteristics of acoustic metamaterials for which this is still an unsolved problem, especially for those with negative effective density and stiffness. A metamaterial is thought as a medium or periodic structure in which the role of effective inertia and elastic elements is played by sufficiently complex oscillatory systems with internal DOFs. Applying the derived equations to a cell of periodicity of a metamaterial one can obtain the exact values of the needed energy characteristics. The theory is verified in computer simulation and laboratory experiment.
The role of pad-modes and nonlinearity in instantaneous mode squeal
Authors: Oberst Sebastian M. , Lai Joseph C.S.
Published: May 2013

Disc brake squeal is a major source of customer dissatisfaction and related warranty costs for automobile manufacturers. Although mode coupling is recognized as a mechanism often found in squealing brakes, recent research results show that friction induced pad-mode instabilities could be the cause of instantaneous mode squeal reported in the literature. In this paper, the nonlinear characteristics of instantaneous mode squeal initiated by pad-mode instabilities are studied by analyzing phase space plots of vibrations and sound pressure for a numerical model of a pad-on-plate system as the friction coefficient increases. Results show that as the friction coefficient increases from 0.05 to 0.65, attractors of vibration in the phase space transits from limit cycle to quasi-periodic, showing signs of approaching chaotic behavior. It is shown here that the correlation of the sound pressure behavior in the phase-space with structural vibration is crucial to understanding the role of pad modes and nonlinearity in instantaneous mode squeal.
Squeak and rattle noise prediction for trimmed door of a car using hybrid statistical energy—Finite element method analysis
Authors: Beigmoradi Sajjad , Jahani Kambiz , Hajabdollahi Hassan
Published: May 2013

Squeak and rattle (S&R) noise are important in-cabin sources of annoyance for occupants. Originally, S&R is generated as a result of colliding and slamming of car’s trim and body structure, which in turn occurs because of the dynamic displacements of components excited by road and powertrain. Squeak noise is interpreted as periodic stick and slip phenomena in the contact boundary of two neighbor surfaces. While rattle noise is the emitted noise when adjacent surfaces collide and impact. Both squeak and rattle phenomena happen in high-frequency range, even though the excitation sources (road and powertrain line) works in low frequency range. In practice, squeak and rattle noise can be minimized via controlling the gaps through a tolerance analysis, as well as the appropriate choice of materials. In this research, potential S&R sources are investigated for the trimmed door of a car using clearance analysis. Impact statistics and overall force level at potential rattle places are calculated through random vibration excitation analyses and afterwards, acoustic sensitivity, overall acoustic response, and loudness are calculated by the aim of hybrid SEA-FE method. The results of this prediction will be used in noise and vibration control plan of the whole car in design phase.
Intrinsic characterization of structure-borne sound sources and isolators from in-situ measurements
Authors: Moorhouse Andy , Elliott Andy , Heo Yong Hwa
Published: May 2013

The paper addresses the problem of how to characterize vibration sources and isolators with measurements made in-situ, either on a working installation or on a test bench. For example, automotive components are often characterized by test bench measurements, but there is a need to know how they will behave when coupled to components with potentially different properties in a vehicle. Ideally all components should be characterized by intrinsic properties, which can then be transferred to other installations. In the paper, some novel in-situ measurement methods for obtaining these properties are presented. First, the active properties of a source are characterized by the blocked force measured in situ. Structural dynamic properties are represented by frequency response functions (mobilities) and it is shown how, if necessary, these may be obtained by indirect measurements, for example when access to measurement points is difficult. New results for dynamic stiffness of isolators are then presented obtained using a novel in-situ measurement approach. The method allows rotational (moment) as well as translational (force) dynamic stiffness to be obtained over a wider frequency range than many test rigs. Results are validated by measurement on an ideal laboratory structure.
Application of differential amplitude and phase-shift keying in underwater acoustic communication based on orthogonal frequency division multiplexing
Authors: Zhengrong Pan , Chi Wang , Xiao Han , Jingwei Yin
Published: May 2013

With the increase of of marine resource and underwater users, developing a high-bit-rate underwater acoustic communication has become a hot topic. Amplitude and phase-shift keying (APSK) is a modulation technique having high efficiency in spectrum utilization, it attracts more and more attention in high-bit-rate underwater acoustic communication. Differential APSK (DAPSK) is modulated using differential amplitude and phase code in time domain, and it has higher bandwidth efficiency and be easier to realize the system than APSK. A transmission system based on DAPSK modulation and OFDM is presented to solve the problems of effectiveness and reliability in high-bit-rate underwater acoustic communication. Simulation results show that the system using DAPSK modulation has a better performance than those using APSK and QAM modulation.
Study of underwater speech coding technique based on contact conduction transmitter.
Authors: Sheng Xuelli , Bai Ye , Lu Jia , Han Jin , Dong Weijia
Published: May 2013

Low bit rate speech coding of 2.4 kbps is actualized by mixed excitation linear prediction algorithm, which meets the requirement of high data rate of underwater speech communication system and the limit of high communication rate of underwater acoustic communication technique. In the process of speech coding, a great deal of speech data is compressed to high speed underwater acoustic communication, and the main characteristics of speaker are remained perfectly. Meanwhile, the capability of avoiding interference is improved obviously by the speech based on contact conduction transmitter as input signal. This underwater speech coding technique and differential OFDM technique are combined and experimented under 434, 1310, and 2000 m in the lake. The real-time transmission of speech signal is presented in the condition of complicated multi-path in the extremely shallow sea. The results show the synthesized speech has well quality of intelligibility and clarity, which satisfies the demand of underwater speech coding.
Modeling binaural receivers in finite difference simulation of room acoustics
Authors: Sheaffer Jonathan , Webb Craig , Fazenda Bruno
Published: May 2013

Binaural room impulse responses are important for auralization as well as for objective research in room acoustics. In geometrical room simulation methods, obtaining such responses is easily achieved by convolving each computed reflection tap with a corresponding pre-measured angle-dependent head-related impulse response. Unfortunately, employing such an approach in wave based methods is challenging due to temporal overlap of room reflections in the calculated response. One alternative is to physically embed a listener geometry in the grid. Whilst this method is straightforward, it requires voxelization of a geometrically complex object. Furthermore, with non-conformal boundary conditions, the voxelized geometry is sample-rate dependent, meaning that numerical consistency is compromised. In this paper, we discuss the merits and drawbacks of embedding different listener geometries in the grid, ranging from a simple rigid sphere to a fully featured laser-scan of a Kemar mannikin. We then introduce a parametric model of a human listener whose head related effects are structurally approximated by digital filters. The model is applied to simulated results in order to extrapolate a binaural response from a single pressure-velocity receiver, without the need to embed any objects in the grid. A comparative analysis of the two methods is presented, and results are discussed in light of room acoustics modeling.
Reduction in reverberation time, resulting from acoustic treatment behind the final surface layer of plywood or drywall
Authors: Mittendorf Steve
Published: May 2013

When sound energy generated in room strikes a surface, it is partially reflected, partially transmitted, and partially absorbed. This is true for each layer of material in a wall, ceiling, or floor. The wave interaction with the surface depends on many factors, but the main factors that are typically involved in calculations of reverberation time are the frequencies of concern, the rigidity, and density of the surfaces, and the absorption of various objects in the room. For the case of an empty room, the estimation of the reverberation time is simplified down to the absorptive properties of the surfaces. This paper presents results that show the importance of considering the composition of the surface (wall, floor, or ceiling) including materials located behind the exposed surfaces. Specifically, it will be demonstrated that a properly installed layer of a loaded vinyl sheeting under the final wall surface layer of drywall will produce a significant reduction in the room reverberation time. With this technique, the preferred reverberation time can be achieved more naturally, while accommodating design constraints such as washable surfaces and minimizing the amount of additional surface treatments required. An additional benefit in the use of the loaded vinyl product behind the surface is a significant improvement in the STC of the wall or ceiling in which it was installed.
Spectral probability density as a tool for marine ambient noise analysis
Authors: Merchant Nathan D. , Barton Tim R. , Thompson Paul M. , Pirotta Enrico , Dakin D. Tom , Dorocicz John
Published: May 2013

The empirical probability density of the power spectral density has been successfully applied as tool to assess signal variability and sensor system performance in the seismic literature. This paper presents the application of this analysis method to underwater ambient noise measurements, and demonstrates its utility in assessing the field performance of passive acoustic monitoring systems and the statistical distribution of noise levels across the frequency spectrum. Using example datasets from an autonomous passive acoustic recorder in the Moray Firth, Scotland, UK, and a cabled subsea observatory in the Strait of Georgia, British Columbia, we show how this method can reveal data limitations such as persistent tonal components and insufficient dynamic range, and phenomena such as bimodality and outliers, which may be undetected by standard analysis techniques. We then combine this approach with conventional percentiles and spectral averages, illustrating how the underlying noise level distributions influence these metrics, and propose this technique as a standard, integrative presentation of ambient noise spectra. Finally, the paper presents cumulative probability density as a method for frequency-domain characterization of chronic noise exposure in marine acoustic habitats.
Global ocean soundscapes
Authors: Porter Michael B. , Henderson Laurel J.
Published: May 2013

There has been increasing interest in understanding the effects of human-induced noise on the marine environment. Under a variety of programs around the world, researchers are modeling “soundscapes” that depict the undersea sound fields in localized areas such as national exclusive economic zones (EEZs). In this work, we develop techniques for modeling soundscapes on a truly global scale and present as an example world maps of ship noise. The resulting soundscapes compose a database for global shipping noise. The noise due to such shipping can travel very long distances producing sort of a background haze for localized modeling in the EEZs.
Probing of crack breathing by pulsed laser-generated acoustic waves
Authors: Tournat Vincent , Ni Chenyin , Chigarev Nikolay , Delorme Nicolas , Shen Zhonghua , Gusev Vitalyi
Published: May 2013

Experimental results on all-optical monitoring of the nonlinear motion of a surface-breaking crack are reported. Crack closing is induced by quasi-continuous laser heating, while Rayleigh surface acoustic pulses and bulk longitudinal surface skimming acoustic pulses are also generated and detected by lasers. By exploiting the strong dependence of the acoustic pulses reflection and transmission efficiency on the state—open or closed—of the contacts between the crack faces, the parametric modulation of ultrasonic pulses is achieved. It is observed that bulk acoustic waves, skimming along the surface can be more sensitive to crack motion than Rayleigh surface waves. It has been found that crack closure by thermo-elastic stresses modifies the propagation paths of the acoustic rays from the point source to the point receiver. Consequently, the arrival times of the acoustic waves contain information on the state of crack closure induced by a particular intensity of laser heating. An important dependence of the detected signals on the initial width/state of the crack and on the presence of necks in the crack opening profile is revealed. It is demonstrated that the mode conversion of the skimming longitudinal bulk waves incident on the crack into the transmitted Rayleigh waves is very sensitive to imperfectness of crack closure. The proposed interpretation of the experimental observations is supported by atomic force microscopy measurements.
Detection and characterization of defects in aerostructures using non-contact ultrasonic transducers
Authors: Netshidavhini Ngeletshedzo , Mabuza Raymond B.
Published: May 2013

This paper describes an investigation into the possibility of using non-contact ultrasonic transducers for detecting and characterizing defects in aerostructures. Our study deals with an ultrasonic method that underscores the recent advances in non-contact and analytical methodologies. Ultrasonic waves are generated by a transducer connected to a Sonatest DryScan 410D using through-transmission mode. In this investigation, ultrasonic through-transmission signals are analyzed for their amplitudes. We treat this problem analytically and experimentally. Various aspects of our approach are presented. The observations reported in this paper deal with defects in aluminum structures. Confirmation of defect geometry is obtained by comparing the results of the non-contact ultrasonic sensors with a conventional ultrasonic testing method. The results obtained are in good agreement with those of the conventional ultrasonic method, indicating that both techniques can be considered as quantitative nondestructive tools for detecting and characterizing defects. Results are presented and discussed.
Basic examination of noncontact inspection in solid material by using high-intensity aerial ultrasonic waves and optical equipment
Authors: Osumi Ayumu , Ito Youichi
Published: May 2013

Recently, developments have improved methods employing aerial ultrasonic waves for contactless inspection of internal defects in materials such as metals, pipe walls, and fiber-reinforced plastics. Specially, this method is noncontact way differ from conventional ultrasonic inspection that is necessary to contact probe to object. We have developed a new method of aerial ultrasonic inspection that uses high-intensity aerial ultrasonic waves and optical equipments. That is, the object is excited in noncontact way using high-intensity aerial ultrasonic waves and the vibration velocity on the object surface is measured with a laser Doppler galvanometer at same time. We analysis the vibration information and detect defect in materials. We also developed a point-converging acoustic source with a stripe-mode vibration plate to generate the high-intensity aerial ultrasonic waves, an essential component of the method. While the sound source operates at a single resonance frequency, the generated ultrasonic wave has nonlinear acoustic characteristics and generates nonlinear higher harmonics at the focal point because the sound intensity increases by converging a sound wave. Under nonlinear ultrasonic irradiation, the object vibrates at the fundamental frequency and harmonic frequencies corresponding to the ultrasonic waves. Therefore, we also attempted to detect defect in materials for analyzing nonlinear vibration.
Ultrasonic transducers for navigation
Authors: Boser Bernhard E. , Przbyla Richard J. , Horsley David A. , Shelton Stefon E. , Guedes André
Published: May 2013

Free space ultrasonic ranging is attractive for applications such as gesture recognition and robotic navigation. Unlike optical ranging technologies, ultrasound based solutions are insensitive to ambient illumination and can therefore be used in- and outdoors. Using time-of-flight, ultrasound rangers work over distances of up to a few meters and achieve sub-mm resolution. Using arrays, objects can be localized in three dimensions. Transducers consist of 400μm aluminum-nitride membranes sandwiched between actuation electrodes batch fabricated on silicon wafers. Unlike capacitive transducers, which require actuation voltages in excess of 100 V, piezoelectric devices are compatible with low-voltage actuation. At the 200 kHz resonance frequency, the wavelength at atmospheric pressure is 2 mm, ideal for compact arrays. The transducers do not dissipate static power and are therefore ideal for battery powered applications. Energy consumption is dominated by the low-noise readout amplifier and is on the order of 1μJ per channel including analog-digital conversion and signal processing, enabling video-rate object tacking at less than 1 mW power dissipation. A prototype system consisting of seven transducers on a 1 mm grid operates up to a 750 mm range and ±35o angle span with ±3.5mm accuracy and ±3o worst case angle error.
Design, development, and testing of transducers for creating spiral waves for underwater navigation
Authors: Brown David A. , Bachand Corey , Aronov Boris
Published: May 2013

The use of spiral waves for underwater acoustic navigation has received much attention in recent years. A spiral wave is characterized as a diverging wavefront that is omnidirectional by magnitude but with a phase that varies linearly by azimuthal angle. Such a signal may be exploited in underwater acoustic navigation when compared with a reference signal of constant phase with respect to azimuthal angle. This paper summarizes our sine/cosine spiral wave transducer (SC-SWT) design approach, which creates a spiral wave by generating two orthogonal dipoles driven in phase quadrature using the same cylindrical piezoceramic element. Several acoustic navigation beacon designs that also contain the constant-phase reference transducer have now been fabricated, including variants where spiral and referencing sources have the same effective acoustical origin in the horizontal and vertical planes. Experimental results, test tank calibrations, and problems to overcome are presented.
Transient phenomena in brass instruments
Authors: Chick John , Logie Shona , Norman Lisa , Campbell Murray
Published: May 2013

The starting transient and the transition between notes are known to be of fundamental musical significance on all instruments. On a brass instrument, the player needs to establish a strongly coupled resonance between the air column and the lips for a note to sound effectively. In the case of a slurred transient, the player must decouple the lips from one resonance before establishing the next. The ease with which this can be achieved depends on several factors including tube length and bore profile, and resonant modes being played. Analysis of measured mouthpiece pressure data and time domain computer modeling have been used to explore transient phenomena in brass instruments, with the aim of identifying desirable playing characteristics of an instrument.
Transient variation in mechanical action and electric action pipe organs
Authors: Woolley Alan
Published: May 2013

Control of the transients by the player has often been cited as one of the most important characteristics of mechanical pipe organ actions since their reintroduction toward the middle of the last century. Previous research indicates that players do not vary the way that they move the key to a significant extent, except as the result of starting the finger movement from some distance above the key rather than in contact with it. This does not necessarily lead to an audible difference. There are, however, other factors in pipe organ action design, pipe voicing, and the way in which organs are played that may lead to real or apparent transient variation irrespective of the type of action. It is well recorded that it is desirable to stagger the release of a chord starting with the pipes with least wind requirement in order to minimize the effect on the wind chest pressure particularly with traditional pressure regulators remote from the wind chest. This paper investigates some of these mechanisms and compares transient variation on mechanical action organs and electric action organs due to different playing styles.
Modes of reed vibration and transient phenomena in free reed instruments
Authors: Cottingham James P.
Published: May 2013

The motion of air-driven free reeds used in the harmonica, accordion, and reed organ is dominated by the fundamental transverse beam mode, but higher transverse modes and the first torsional mode are usually present during steady oscillation, even at low amplitude. In addition, a lateral mode has sometimes been detected, in which the reed tongue oscillation is perpendicular to the transverse oscillation. Interaction of the reed with a resonance in the instrument can result in unusual effects. In the accordion, resonances of the reed cavity can interfere with the reed self-excitation mechanism. In the harmonica, when the reed is nearly closed, a strong aerodynamic instability can in some cases lead to torsional flutter. A characteristic of some free reed instruments is a slow attack, in which the sound builds gradually and often unevenly, with the effect being greater for the longer, lower-pitched reeds. There is evidence that the first torsional mode and the second transverse mode may be significant in initiating reed oscillation, so that reed design enhancing the torsional mode may be helpful in alleviating the problem of slow attack.
Numerical reproducibility of time-dependent motions of spatial waves in air-columns of wind instruments
Authors: Takahashi Kin'ya , Goya Saya , Goya Kana , Susaki Chisato
Published: May 2013

Since Schumacher introduced a time-domain model of single-reed instruments and McIntyre et al. gave the general concept of time-domain models of wind instruments, the time-domain models, namely, delayed feedback models, have become an important numerical tool for study of wind instruments due to their simplicity, easiness to handle, and reliability. However, those models only reproduce wave oscillations observed in mouthpieces of wind instruments. In this talk, we will propose a numerical technique, which is able to reproduce time dependent motions of spatial waves in an air-column. It is composed of inversed wave propagator matrices combined with the forward and backward Fourier transformations. The resultant spatial waves in the air-column exhibit very similar time-dependent behavior to those observed by an experiment for the clarinet. Actually, backward and forward rounded-off step waves are observed. We will also discuss difference in wave shapes and their time-dependent behavior depending on the shapes of air-columns, cylindrical one like the clarinet, conical one like the saxophone and horn-shaped one like brass instruments. For the conical and horn-shaped air-columns, Helmholtz-like waves are observed rather than the step waves observed for the cylindrical air-column.
A thermoviscous tube propagation model suitable for time domain analysis
Authors: Thompson Stephen C. , Gabrielson Thomas B. , Warren Daniel M.
Published: May 2013

Modeling acoustic propagation in tubes including the effects of thermoviscous losses at the tube walls is important in thermoacoustics, in hearing aid modeling, and in modeling wind musical instruments. Frequency dependent impedances for a tube transmission line model in terms of the so-called thermal and viscous functions are well established, and form the basis for frequency domain analysis of systems that include tubes. However, frequency domain models cannot be used for systems in which significant nonlinearities are important, as is the case with the pressure-flow relationship through the reed in a woodwind instrument. This paper describes a tube model based on a continued fraction expansion of the thermal and viscous functions. The expansion can be represented as an analog circuit model, which allows its use in time domain system modeling. A simple model of a clarinet-like oscillation will be shown.
Analysis of railway vibration signals using supervised machine learning for the development of exposure-response relationships
Authors: Sharp Calum , Woodcock James , Peris Eulalia , Sica Gennaro , Moorhouse Andrew , Waddington David
Published: May 2013

The aim of this work is to investigate the applicability of the use of supervised machine learning methods to classify unknown railway vibration signals within a measurement database. The results of this research will be implemented in the development of exposure-response relationship for annoyance caused by freight and passenger railway vibration, so as to better understand the differences in human response to these two sources of environmental vibration. Data for this research come from case studies comprising face-to-face interviews with respondents and measurements of their vibration exposure collected during the University of Salford study “Human Response to Vibration in Residential Environments.” Vibration data from this study are then classified into freight and passenger categories using supervised machine learning methods. Finally, initial estimates of exposure-response relationships are determined using ordinal probit modeling. The results indicate that the annoyance response due to freight railway vibration may be significantly higher than that due to passenger railway vibration, even for equal levels of exposure. The implications of these findings for the potential expansion of freight traffic on rail are discussed. [Work funded by the Department for Environment, Food and Rural Affairs (Defra) UK, and EU FP7 through the CargoVibes project.]
Prediction of the effectiveness of a sound-masking system in an open-plan office including the Lombard Effect
Authors: Lei Yizhong , Hodgson Murray
Published: May 2013

Sound masking can improve speech privacy in rooms by increasing background-noise levels that mask distracting speech sounds. The Lombard Effect indicates that an increase in background-noise level can increase talker voice levels, reducing speech privacy and the benefit of a sound-masking system. To investigate this, a model of an existing open-plan office was created in CATT-Acoustics and validated. The model was used to predict speech-transmission index (STI) and the effectiveness of a sound-masking system, without and with the Lombard Effect, described by the existing Lombard Voice Model. Predictions were made for ambient-noise levels of 30, 40, and 45 dBA, at various distances from a primary talker, and for 0–4 secondary talkers. With 30-dBA ambient noise, STIs at 1 and 4 m varied with the number of talkers from 0.67 to 0.91 and 0.23 to 0.62 without the sound-masking system, from 0.58 to 0.70 and 0.13 to 0.25 with it but ignoring the Lombard Effect, and from 0.64 to 0.73 and 0.18 to 0.27 with the Lombard Effect. The Lombard Effect reduced the benefit of the sound-masking system by 3–9% and 7–22%. With higher ambient noise, the system is less effective; the Lombard Effect can almost cancel its benefit, resulting in increased STI (decreased privacy) with the system operating.
Sound quality in small music classrooms
Authors: Cunha Iara B. , Mattos Tiago , Bertoli Stelamaris R.
Published: May 2013

Good conditions for teaching, learning, and practicing a musical instrument are crucial for a musician’s progress. Small rooms for teaching and practicing musical instruments have specific requirements about acoustic performance and strong influence on the perception of the users. Acoustical problems in music classrooms may cause difficulties for teachers to identify mistakes from the young students performance other than those originated from the room itself. For this paper, three music classrooms were evaluated according to reverberation, background noise, and airborne sound insulation between rooms. Thus, reverberation time (RT), background noise level, and standardized level difference (DnT), as a function of frequency and according to ISO 3382-2:2008 and ISO 140-4:1998 standards, were measured and judged. As some results have disagreed from literature recommendations, the main faults of each room were highlighted, considering the type of instrument that is taught, and suggestions for acoustic adjustment were made.
Ocean noise: Lose it or use it
Authors: Kuperman William A.
Published: May 2013

Ocean noise, natural or man-made, has typically been treated as unwanted interference in the context of detecting signals. However, more recently noise has itself also become a signal of interest in which, for example, ocean or geophysical properties are embedded in the noise field. There is now significant ongoing research in trying to extract information from noise. Much of the latter has utilized either own-ship noise, surface generated noise, biological noise, and/or distant shipping noise. Here we review the evolution of research in ocean noise as it progressed from basic descriptive categorization to attempts to minimize its impact on signal detection, and finally, to its utilization as an environmental descriptor.
Ambient noise measurements with deep sound in the Philippine Sea
Authors: Buckingham Michael J. , Barclay David R.
Published: May 2013

Most measurements of ambient noise in the deep ocean have been performed using an array of hydrophones located at a fixed depth. Recently, an instrument platform known as Deep Sound has been developed, consisting of a glass sphere containing data acquisition, data storage, and system control electronics, with a pair of vertically aligned hydrophones mounted externally. Deep sound descends under gravity, jettisons a drop weight at a pre-assigned depth, and returns to the surface under buoyancy, traveling in both directions at a nominal 0.6 m/s. Throughout the descent and ascent, the hydrophones record the ambient noise over a bandwidth from 3 Hz to 30 kHz. In April–May 2009, Deep Sound was deployed to a depth of 5500 m in the Philippine Sea. The vertical coherence of the measured noise, from 1 to 10 kHz, matches accurately a simple theory of deep-water, wind-generated ambient noise, provided that the local sound speed is used in evaluating the theoretical coherence function. Moreover, the cross-correlation function of the noise, obtained by taking the Fourier transform of the coherence function, provides the basis of an inversion technique for returning the sound speed profile in the water column. [Research supported by ONR.]