bluuebunny/crossref_metadata_2025 huggingface dataset:
Passive elastography in soft-tissues: Phase velocity measurement
Authors: Giammarinaro Bruno , Catheline Stefan
Published: June 2017

Elastography is an imaging technique used on medical ultrasound devices. It consists in measuring shear waves in soft tissues in order to give a tomography reconstruction of the shear elasticity. A method of measurement, usually referred as passive elastography, is to use noise correlation techniques on diffuse shear wave fields present in the medium. In human body, these fields can be naturally created by activities like heart beating, arteries pulsatility. Passive elastography allows to locally estimate the group velocity in the medium and this method has already been used for some organs as the liver, the thyroid or the brain. The present study is therefore devoted to improve this method with the calculation of the phase velocity. For example, this information, obtained for each frequency, could allow to measure the attenuation with Kramers-Krönig relations.
Transcranial ultrasound detection of intracranial hemorrhages: time-frequency analysis with empirical and variational mode decomposition
Authors: Jordan Michael P. , Bennoui Amber B. , Molnar-Fenton Anjelica A. , White Phillip J.
Published: June 2017

Ultrasound imaging has become a standard method for evaluating patients who have suffered blunt trauma. Specifically, focused assessment with sonography in trauma, commonly known as the “FAST exam,” is regularly employed to detect free intraperitoneal, intrathoracic, and pericardial fluid in the setting of trauma. Currently, evaluation of the intracranial space remains a significant missing component of the FAST exam because the skull bone acts as a physical barrier to ultrasound transmission for existing approaches in pulse-echo ultrasound imaging. To address this shortcoming, we have explored a grounds-up re-evaluation of the way in which ultrasound can be used in neurosonography based on the hypothesis that backscattered signal from the intracranial space can be analyzed to identify the unique signature of pooling and coagulated blood. Preliminary experiments with tissue phantoms, ex vivo animal blood, and ex vivo human calvaria have established the parameters that optimize the SNR of pulse-echo transcranial ultrasound. The need to improve the sensitivity in isolating the desired signals have led to the exploration of several time-frequency signal analysis techniques, including the recently introduced empirical and variational mode decomposition methods. Our results have established the basis of a much-needed novel intracranial assessment technique to incorporate into the FAST exam.
Analysis of the feasibility of an array of MEMS microphones to machinery condition monitoring or fault diagnosis
Authors: del-Val Lara , Izquierdo Alberto , Villacorta Juan J. , Suarez Luis , Herráez Marta
Published: June 2017

During the last decades, vibration analysis has been used to evaluate condition monitoring and fault diagnosis of complex mechanical systems. The problem associated with these analysis methods is that the employed sensors must be in contact with the vibrant surfaces. To avoid this problem, the current trend is the analysis of the noise, or the acoustic signals, which are directly related with the vibrations, to evaluate condition monitoring and/or fault diagnosis of mechanical systems. Both, acoustic and vibration signals, obtained from a system can reveal information related with its operation conditions. Using arrays formed by digital MEMS microphones, which employ acquisition/processing systems based on FPGA, allows creating systems with a high number of sensors paying a reduced cost. This work studies the feasibility of the use of acoustic images, obtained by an array with 64 MEMS microphones (8x8) in a hemianechoic chamber, to detect, characterize, and, eventually, identify failure conditions in machinery. The resolution obtained to spatially identify the problem origin in the machine under test. The acoustic images are processed to extract different feature patterns to identify and classify machinery failures.
Numerical investigation of normal mode radiation properties of ducts with low Mach number incoming flow
Authors: de Santana Neto José P. , Braga Danilo , Cordioli Julio A. , da Silva Andrey R.
Published: June 2017

Normal mode radiation properties of ducts issuing a subsonic mean flow have been thoroughly investigated in the past. The behavior of the radiation characteristics, such as the magnitude of the reflection coefficient and the length correction, are well understood. Nevertheless, the behavior of the same features in the presence of an incoming low Mach number flow has not been investigated in detail, particularly in the case of the length correction. This work presents a numerical study of the reflection coefficient and length correction of unflanged pipes and pipes terminated by circular horns of different radii in the presence of an incoming flow. The investigations are conducted with a tridimensional lattice Boltzmann scheme. The results suggest that the detachment and reattachment of the incoming flow inside the duct play a significant role on the transfer of kinetic energy from the flow to the internal acoustic field. Moreover, the results show that the mechanism of flow detachment and reattachment is highly sensitive to the geometrical characteristics at the open end.
Analysis and design of Fresnel zone plates with multiple foci
Authors: Candelas Pilar , Fuster José Miguel , Rubio Constanza , Castiñeira-Ibáñez Sergio , Tarrazó-Serrano Daniel
Published: June 2017

Fresnel Zone Plates (FZPs) become an interesting alternative to traditional lenses when planar fabrication is advantageous, and are used in a wide range of physical disciplines such as optics, microwave propagation, or ultrasounds. Conventional FZPs produce a single focus, which is optimal in most applications. However, certain medical applications, such as MRI (magnetic resonance imaging) guided ultrasound surgery, require multiple foci ultrasound exposures. In this work, new multi-focus Fresnel lenses (MFFLs) based on conventional FZPs are presented. The advantages and drawbacks of these new MFFL structures are thoroughly analyzed. There is a tradeoff on the number of foci achieved in a single MFFL and its focusing efficiency. Therefore, the most efficient MFFL is that with two foci. A procedure for designing 2-foci MFFLs, in which the focal length of both foci may be selected independently, is established. For each 2-foci MFFL, there are several physical implementations. The focusing properties of all implementations are compared among them. From this comparison, the most efficient MFFL is selected and fully characterized.
Experimental study of aeroacoustic damping performance of in-duct perforated orifices with different geometric shapes
Authors: Zhao Dan , Ji C. Z. , Han Nuomin , Li Xinyan
Published: June 2017

In this work, 11 in-duct perforated plates are experimentally tested in a cold-flow pipe. These plates have the same porosities but different number and geometric shaped orifices: (1) circle, (2) triangle, (3) square, (4) pentagon, (5) hexagon, and (6) star. The damping effect of these orifices is characterized by power absorption and reflection coefficient from to. It is found that the orifice shape has little influence on and at lower frequency. However, as the frequency is increased, star-shaped orifice is shown to be with much lower Δ in comparison with that of other shapes orifices. For the perforated plates with the same shaped orifices, increasing does not lead to an increase of power absorption at lower frequency. However, the orifice with the same shape and porosity but larger is found to be associated with more power absorption at approximately. Maximum power absorption is approximately at about, as. The optimum depends on the orifice shape. The present parametric measurements shed light on the roles of the number and geometric shapes of orifices and the flow parameters on its noise damping performance.
Analysis of the tonehole lattice of the northern xiao flute
Authors: Prairie Michael , Lei Da
Published: June 2017

The northern Chinese xiao is an end-blown flute characterized by an array of two to three pairs of holes that separate the main bore from an extended foot. The top pair are tuning holes and the lower ones are described as vent holes, but the design of the latter have shown an influence in the attainability of the third octave as well as the timbre of the notes (G. Ellis, personal communication, 3 March 2014). We analyze these holes in the context of an infinite lattice with a cutoff frequency fc determined by the geometry and spacing of the top holes, and compare the results to that of the pole frequency of the calculated impedance of the actual, irregular lattice below the tuning holes. The input impedance of a cylindrical pipe with a tonehole lattice is calculated, and pressure standing waves are predicted for the peaks of the resulting admittance spectra. The standing waves are compared to experimental results to confirm the high-pass filter properties of the lattice above fc. The effects of varying lattice dimensions on fc and the alignment of upper harmonics with peaks in the spectra will be presented.
Acoustic characterization of chichin bass-drum
Authors: Floody Sergio E. , Núñez Luis E.
Published: June 2017

The objective of this work is to present an acoustic characterization of the chinchín, a bass drum type instrument native of Chile. The instrument is played by the chinchinero, an urban street performer in Chile, who dances acrobatically and plays the instrument simultaneously. Carried like to a backpack, the musician play the instrument with long drumsticks, which also involves a rope tied around the performer's foot to play the hi-hat cymbals. The string that drives the hi-hat cymbals passes through two holes in the cylindrical drum shell, modifying the expected sound of this type of instruments. We present detailed vibro-acoustic characterization in frequency and spatial domain using the Finite Element Method (FEM). Natural frequencies are compared with a usual bass-drum layout of similar dimensions as a baseline. Our preliminary results show differences in the fundamental frequency and the overtones of the chinchín bass drum are different from the normal one.
Physical model of a drum using an edge-diffraction approach
Authors: Martín Román Sara R. , Svensson U. Peter , Rau Mark , Smith Julius O.
Published: June 2017

Physical modeling of musical instruments is of great interest, both due to the interpretation of the parameters that make the model as similar to reality as possible, and because of the faithful sound synthesis. In this paper we will focus on the modeling of percussion instruments and more concretely drums consisting of a vibrating membrane and a rigid body. One recently published physical model [S. Bilbao and C. J. Webb, J. Audio Eng. Soc. 61 (2013) 737-748] uses finite difference time domain schemes to solve both the system of equations describing the dynamics of the membrane, and the influence of the surrounding air. The main drawback of that approach is the growth of computation cost with the scale of the problem. A new approach is suggested here where an edge diffraction-based method [A. Asheim, U. P. Svensson, J. Acoust. Soc. Am. 133 (2013) 3681-3691] is used to compute both the air loading on the surface and the sound radiation. The finite difference time domain method is used in this approach too but only to solve the dynamics of the membrane. The computational complexity is evaluated and results are compared to reference solutions.
Noise forecasting: A machine-learning and probabilistic approach
Authors: Hart Carl R. , Wilson D. Keith , Pettit Chris L. , Nykaza Edward T.
Published: June 2017

Forecasting the transmission of transient noise is a challenge since several sources of uncertainty exist: source and receiver positions, meteorology, and boundary conditions. These sources of uncertainty are considered to be model parameters. Experimental observations of noise, such as peak sound pressure level, or C-weighted sound exposure level, are data parameters with their attendant sources of uncertainty. Forward models, relating model parameters to the data parameters, are also imprecise. We quantify all of these sources of uncertainty by a probabilistic approach. Probability density functions quantify a priori knowledge of model parameters, measurement errors, and forward model errors as states of information. A conjunction of these states of information is used to generate the joint probability distribution of model and data parameters. Given a forecast of model parameters, say, from a numerical weather prediction model, the joint probability distribution is marginalized in order to forecast the noise field. In this study, we examine the feasibility of this approach using, instead of numerical weather predictions, point measurements of meteorological observations and peak sound pressure level collected during a long-range sound propagation experiment. Furthermore, we examine different types of forward models based on machine learning.
A simple sound metric for evaluating sound annoyance in open-plan offices
Authors: Parizet Etienne , Chevret Patrick , Kostallari Krist
Published: June 2017

Noise in open-plan offices has become a major health issue. Intelligible speech is considered as the most annoying noise sources by the occupants of such offices. Speech level fluctuations prevent people from achieving some high-demanding tasks, thus inducing annoyance and tiredness. Many studies were conducted in order to identify a sound metric closely related to this Irrelevant Speech Effect. Hongisto et al. have shown that Speech Transmission Effect is appropriate for evaluating the annoyance due to a neighbor in the office. More recently, Schlittmeier et al. suggested that the Fluctuation Strength can be used to evaluate the effect of the fluctuations of the ambient noise on task performance. This paper intends to present a new metric. It is based on the measurement of short-term temporal modulation of sound level. Results indicate that it seems to be as efficient as STI or FS, while being more suitable for in-situ experiments and usable by practitioners.
Array-based inhomogeneous soundwave generation to enhance sound transmission into solids
Authors: Kyle Trevor , Woods Daniel C. , Tiwari Rahul , Rhoads Jeffrey F. , Bolton J. S.
Published: June 2017

The acoustic excitation of energetic materials has been demonstrated to be useful in detection and defeat applications, but its efficacy is hindered by the inability to transmit a high percentage of incident acoustic energy across the air/energetic material interface. While large acoustical impedance differences usually prevent energy transmission from air into a solid, inhomogeneous incident waves have been found to transmit a significant percentage of their energy into the target material. Thus, inhomogeneous waves, whose amplitudes decay spatially in a direction different from the propagation direction, are an optimal choice for this application; however, it is difficult to create such a waveform by using a simple source. The objective of the present work is to demonstrate that by tuning the strengths and phases of sound sources in a linear array, an interference pattern can be generated such that an inhomogeneous wave forms on a surface of interest. Furthermore, it is demonstrated that by adjusting the level of inhomogeneity of the wave and its incidence angle, one can target the parameters associated with optimal sound transmission, and that these waves can be generated even in the presence of small errors in the powers and phases of the sources.
A spheroid model for the sound radiation of a loudspeaker on a sound bar
Authors: Roggerone Vincent , Corteel Etienne , Boutillon Xavier
Published: June 2017

The sound radiation of a loudspeaker on a sound bar with a slender shape is analyzed. Measurements and boundary element method (BEM) simulations of a rectangular rigid enclosure with a flat piston turn out to be in close agreement up to the frequency limit imposed by the discretization chosen for the BEM. Looking up for a shorter computation time, we consider an analytic model based on a geometrical approximation of the sound bar by a prolate spheroid. The corresponding spheroidal coordinate system allows for an analytical solution of the sound-radiation problem. The following parameters are adjusted: geometry of the ellipse-based spheroid, size and location of the circular piston, minimum order of the spheroidal wave functions that ensures convergence. In the light of the BEM results, we also predict the frequency validity of the analytic model. In order to improve the control of the acoustical field radiated by a sound bar, we discuss the influence of the enclosure edges on the regularity of the sound field pattern. [Work supported by the ANR-13-CORD-0008 EDISON 3D grant from the French National Agency of Research.]
Computer simulation of synthetic apertures radar for classroom demonstration
Authors: Kirkwood Kathryn P. , Korman Murray S.
Published: June 2017

Synthetic Aperture Radar (SAR) has many civilian and military applications as a high resolution imaging system. A Mathematica® simulation of Synthetic Aperture Acoustic Radar will demonstrate how two-dimensional point targets on a ground plane can be imaged from a collection of acoustic echoes. A transmitter and receiver will be modeled as a one point element that stops along a linear track at collection points and hops to the next location (stop and hop approximation). The transmitter on the hypothetical apparatus will transmit acoustic signals that reflect off the targets as echoes to be collected by the receiver at each location of the track. A matched filter correlation process will complete pulse compression of the LFM (linear frequency modulated) chirp. The image reflectance of the point targets will be constructed using a time correlation/backprojection algorithm developed by Yegulap [“Fast Backprojection Algorithm for Synthetic Aperture Radar,” In Proceedings 1999 IEEE Radar Conference, Waltham, MA, April 20-22, 1999, 60-65]. Image resolution may be improved by increasing chirp bandwidth.
The effects of diffraction on the frequency difference and frequency sum autoproducts
Authors: Worthmann Brian M. , Dowling David R.
Published: June 2017

Previously, a remote sensing technique termed frequency difference matched field processing was developed for source localization in the shallow ocean (Worthmann et al., 2015, 138, 3549-3562). In this technique, field measurements at the in-band frequency are shifted down (or up) in frequency through the use of the bandwidth-averaged frequency-difference (or frequency-sum) autoproduct, a nonlinear construction made from field amplitudes and averaged over the available signal bandwidth. These bandwidth-averaged autoproducts may have phase structure similar to genuine acoustic fields at out-of-band frequencies when the original acoustic field is well-described by a sum of ray-path contributions. While ray theory may be a useful field description in many situations, it does not include diffraction. In this presentation, the effects of acoustic diffraction on the autoproduct are analyzed in an environment where diffraction varies in importance depending on the spatial location. Specifically, the behavior of the autoproducts is investigated in Sommerfeld’s half-plane problem, where a plane wave is incident on a thin, semi-infinite rigid barrier. The bandwidth-averaged frequency difference and sum autoproduct fields are calculated in this environment, and their correlation with exact out-of-band acoustic fields are provided as a function of distance from the barrier and scattering angle. [Sponsored by NSF and ONR.]
Speech intelligibility in complex environments: Modeling and possible applications
Authors: Colburn H. Steven , Mi Jing
Published: June 2017

A summary of recent modeling work from our lab on the topic of speech intelligibility in complex environments will be presented, including some results from experiments designed to evaluate the models. The primary focus will be models of binaural processing, with the dual goals of (1) understanding the processing within the brain and (2) suggesting possible strategies for external processing that could provide more useful acoustic inputs for listeners with impaired hearing. Several processing algorithms based on allocation of individual time-frequency slices will be considered, including one based on EC processing and one based on local (in time-frequency) estimates of interaural time and intensity differences and interaural coherence. Performance of these algorithms will be evaluated using statistics of source-separation accuracy (with the ideal binary mask as the “golden standard”) and also using human listening experiments. In the listening experiments, the waveforms generated by combining the time-frequency slices selected for the target location are presented to the subject in tests of speech intelligibility. Performance with these waveforms are compared to performance with the original binaural waveforms and to performance in collocated conditions. [Work supported by NIH/NIDCD Grant 2R01DC000100.]
Understanding effects of hearing loss on multitalker speech intelligibility in terms of glimpsing
Authors: Best Virginia , Mason Christine , Roverud Elin , Swaminathan Jayaganesh , Kidd Gerald
Published: June 2017

In multitalker mixtures, listeners with hearing loss demonstrate reduced spatial release from masking compared to listeners with normal hearing. However, it is not clear whether this problem reflects an inability to use spatial cues to segregate sounds, or a degraded representation of the target speech itself. In this work, a simple monaural glimpsing model was used to isolate the target information that is potentially available at each ear in spatialized speech mixtures, and intelligibility of these glimpsed stimuli was then measured directly. Performance in the glimpsed condition was strongly correlated with performance in the natural spatial condition, suggesting a common limit in both cases. Similar results were found for different kinds of speech mixtures in which the target and maskers were distinguished by cues other than spatial location (talker sex, or time-reversal). The results suggest that the primary detrimental effect of hearing loss might be on the representation of target glimpses, rather than on the segregation of competing talkers, in multitalker mixtures.
The effect of listener head orientation on speech intelligibility in noise
Authors: Grange Jacques A. , Culling John F.
Published: June 2017

The signal-to-noise ratio at one ear is progressively improved by orienting the head away from the target sound source by up to 65 degrees, so facing the speaker in a sidelong way may be an effective listening tactic in noisy listening situations. In a listening configuration that optimized this effect in a sound-treated room, speech reception thresholds improved by up to 10 dB with head orientation, but without instruction few listeners adopted the tactic. Audio-visual presentation of the target speech further suppressed its use [Grange and Culling, J. Acoust. Soc. Am. 139, 703-712 (2016)]. Audio-visual presentation produced an additive lip-reading benefit that was unaffected by a head orientation 30 degrees away from the speaker. A head-orientation benefit was also observed in realistic listening conditions, simulated over headphones. Binaural room impulse responses from a real restaurant were used to simulate listening at six different tables with nine concurrent interferers. Head orientation of 30 degrees produced a mean benefit of 1 dB for speech interferers and 1.3 dB for noise interferers [Grange and Culling, J. Acoust. Soc. Am. 140, 4061-4072 (2016)]. These results suggest that listeners would benefit from advice to orient away from the speaker while maintaining eye contact.
Objective evaluation of binaural noise-reduction algorithms for the hearing-impaired in complex acoustic scenes
Authors: Schädler Marc René , Warzybok Anna , Kollmeier Birger
Published: June 2017

The simulation framework for auditory discrimination experiments (FADE) was used to predict the benefit in speech reception thresholds (SRT) with the German matrix sentence test when using a range of single- and multi-channel noise-reduction algorithms in complex acoustic conditions. FADE uses a simple robust automatic speech recognizer to predict SRTs from simulated speech recognition experiments in an objective way, independent from any empirical reference data. Here, it was extended with a simple binaural stage and individualized by taking into account the audiogram. Empirical data from the literature was used to evaluate the model in terms of predicted SRTs and benefits in SRT when using eight different noise-reduction algorithms. In a realistic binaural cafeteria condition, FADE explained about 90% of the variance of the empirical SRTs for normal-hearing listeners and predicted the corresponding benefits in SRT with a root-mean-square prediction error of 0.6 dB. In contrast to the surprisingly high performance of this simple approach for normal-hearing listeners, much less of the inter-individual variance can be explained for hearing-impaired listeners, where individual audiograms only sufficed for aided group performance predictions. In a single competing talker condition, the prediction even failed for the normal listeners, clearly demonstrating the limits of the current versatile approach and demanding further extensions.
On the relationship between a short-term objective metric and listening efficiency data for different noise types
Authors: Prodi Nicola , Visentin Chiara
Published: June 2017

This study aims to compare the distinct effects of a steady-state (SSN) and a fluctuating (ICRA) masker on speech reception performance. SNR, reverberation and masker type were combined as to create several acoustic scenarios; matrixed-word listening tests in the Italian language were proposed to a panel of young adults with normal hearing, collecting data on intelligibility scores (IS) and response time (RT). The listening conditions were objectively qualified with the short-term metric STIr, defined as the average of the STI values calculated over short time-windows, whose duration reflects the typical phoneme length. The results showed that for a given STIr, both maskers yield the same IS, being the fluctuation benefit already accounted for by the objective metric. The slope of the STIr-IS function only depends on the speech material. Anyway, the fluctuating masker calls for an increased amount of cognitive resources to be deployed in the speech reception process, traced by a statistically significant higher response time. These results shade a new light on the fluctuating masker release (FMR) phenomenon.
Influence of interaural time differences on the loudness of low-frequency pure tones at varying signal and noise levels
Authors: Berthomieu Gauthier , Koehl Vincent , Paquier Mathieu
Published: June 2017

Directional loudness sensitivity, which is generally accounted for by at-ear pressure modifications because of the perturbation of the sound field by the head, has been reported to occur at 400 Hz where shadowing effects are usually considered small. Then, an effect of the interaural time difference (ITD) on loudness has been observed for pure tones below 500 Hz. The latter was rather small but still significant, contributing to directional loudness sensitivity. In addition, it has been shown that the effect of ITD on loudness was caused by the ITD itself and not by its related localization. As this effect appeared significant at low level only (40 phon), it was hypothesized that ITD could help separate the signal from the internal noise and enhance its loudness. The aim of the present study is to confirm this hypothesis by observing the effect of ITD on the loudness of low-frequency pure tones (100 and 200 Hz) for various signal-to-noise ratios. The signal level was varied from 30 to 90 phon and the noise could be internal only or external also. The effect of ITD appeared significant up to 40 or 50 phones depending on the frequency.
Computational study of head geometry effects on sound pressure gradient with applications to head-related transfer function
Authors: Farahikia Mahdi , Su Quang T.
Published: June 2017

Effects of object geometry on sound scattering of far-field incident sound waves for two different head models (spherical and ellipsoidal) have been studied using an optimized Finite Element Method (FEM) based on frequency-dependent adaptive dimensions. This optimized FEM technique is proven both efficient and accurate when compared with analytical results for the spherical model, with maximum deviation of 0.6 dB. Comparisons between models have been made on the equivalent Head-Related Transfer Functions (HRTFs) for acoustic pressure, and for the first and second order pressure gradients on the surface. It is shown that while directionality cannot be achieved at lower frequencies using only pressure, pressure gradients provide sound cancellation for certain source orientations. Hence, it is possible to cancel incoming sound from the front (or behind) or sides depending on the direction (radial, azimuthal) and order of pressure gradients. While the pattern of pressure gradient directionality remains similar between the spherical and ellipsoidal models, the difference in dimensions affects the amplitude of the equivalent HRTFs for these parameters. This study provides insight into the placement of directional microphones on the head for hearing aids.
My personal head related transfer function: High quality individualized computer models
Authors: Fingerhuth Sebastian , Angles Danny , Barraza Juan
Published: June 2017

In this paper, we present a method to obtain individual 3D CAD-models of the head and pinna. The method is a hybrid method: A photogrammetric technique for the head is combined with a molding process for the pinna. For the 3D reconstruction of the head, a set of pictures from different perspectives of the person is taken. Therefore the person is stepwise rotated while seated and pictures are taken using semi-professional photographic equipment. Four different orbits are used: top level, upper level, eye level, and low level. These pictures, about 120, are then combined using a commercial photogrammetric software. Due to the complex and concave geometry of the pinna, an additional step has to be taken. An alginate mold is made for each pinna which then is molded again to obtain a positive plaster replica of the pinna. This replica is then converted to a CAD model. For this last step, two methods were compared: the same photogrammetric process as before and using a 3D scanner. Both CAD models, head and pinna, are then carefully combined into one CAD mesh. The CAD-models can then be used to compute HRTFs by means of the Boundary Element Method (BEM).
Interactive simulation and free-field auralization of acoustic space with the rtSOFE
Authors: Seeber Bernhard U. , Clapp Samuel W.
Published: June 2017

The Simulated Open Field Environment (SOFE), a loudspeaker setup in an anechoic chamber to render sound sources along with their simulated, spatialized reflections, has been used for more than two decades in free-field hearing research. In 2004, the concept was revised to incorporate room-acoustic simulation software that computes sound reflections in arbitrarily-shaped rooms and auralizes them via many loudspeakers—the principle of various systems used today (Hafter and Seeber, ICA 2004). For a complete redesign of the system, an anechoic chamber has been purpose-built at TUM and I will talk about its specifications. The anechoic chamber hosts the real-time SOFE (rtSOFE), a setup with 61 loudspeakers to create a spatial sound field in a 5 m x 5 m area along with 360° of visual 3D projection. New room-acoustic simulation software for interactive computation of reflections computes room impulse responses in sub-millisecond intervals and updates a convolution system capable of convolving seconds-long impulse responses for many independent loudspeaker channels with very short latency. I will present the general concept and capabilities of the new rtSOFE, give details about its implementation and first experimental results. The rtSOFE in the new anechoic chamber at TUM forms a cutting edge research facility for interactive psychoacoustic and audio-visual research in virtual acoustic space.
Benchmark problem identifying a pollution effect in boundary element method
Authors: Marburg Steffen
Published: June 2017

In his former contributions on the boundary element method (BEM) in acoustics, the authors had not found any indication of a dispersion error similar to what is known as the pollution effect for the finite element method (FEM). However, in a recent paper, the author has demonstrated the effect of numerical damping in BEM. A consequence of the pollution effect of FEM and numerical damping in BEM is that the common rule of choosing a fixed number of elements per wavelength is not valid. By using one of the benchmark cases of the EAA Technical Committee for Computational Acoustics, this can be easily shown. Traveling waves in a long duct are decaying. In this presentation it will be shown that the numeric error depends on the length of the duct. For models with many waves over its surface, numerical damping adds an additional numeric error which can be understood as a pollution error because a local refinement in certain regions of the model will not significantly decrease the error. It will be discussed in which cases this problem may become relevant for practical use of BEM.
A brief review, benchmark, future development of structural acoustic tools
Authors: Wu Kuangcheng
Published: June 2017

Numerical tools have been widely applied to real world applications for noise and vibration control. Each tool has its own advantages and limitations. To properly use the tool in the correct environment, it is imperative to understand its underlying physics. One of the main challenges in modeling a marine structure is to correctly simulate its unbounded surrounding domain. Analytic solutions are limited to certain geometries (Junger & Feit, Sound, Structure, and Their Interaction, ASA, 1993), semi-analytic solution (i.e., Surface Variational Principle), and different numerical techniques (i.e., boundary element, infinite element, and perfectly matching layer) has been used to model complex structures with unbounded fluid implicitly or explicitly while satisfying the Sommerfeld radiation BC (Pierce, Acoustics: An Introduction to its Physical Principles and Applications, ASA, 1989). In this paper, those numerical techniques will be briefly reviewed and several benchmark cases for simple structures will be presented. With the understanding of underlying physics, ideas in speeding up the numerical analysis by proper simplification or model reduction will be addressed.
Comparison of three-dimensional acoustical Green’s functions for a half-space BEM formulation
Authors: Ochmann Martin A.
Published: June 2017

We consider three-dimensional acoustical scattering or radiation problems in frequency domain above an infinite flat plane equipped with a local impedance condition. For such half-space problems, a BEM formulation is of advantage, where the Green’s function used satisfies not only the Helmholtz equation, but also the boundary condition at the impedance plane. When using such a tailored Green’s function, only the surface of the sound radiating or scattering object has to be discretized, since the influence of the impedance ground is automatically taken into account. Simple formulas for such half-space Green’s function exist only for rigid or soft infinite planes. For a ground with arbitrary surface impedances, many different expressions of the Green’s function are given in the literature. For incorporating these functions into a BEM formulation, the first and second normal derivatives must be calculated in such a way that they do not possess strong singularities. In the present work, four representations of half-space Green’s functions are investigated and compared for three different kinds of surface impedances with respect to accuracy and computing time: (1) for a pure absorbing ground, i.e., with real impedance, (2) for a masslike, and (3) for a springlike ground corresponding to pure imaginary impedances.
Comparison of finite element and analytical modeling of scattering of an acoustic wave by particles in a fluid
Authors: Pinfield Valerie J. , Forrester Derek M. , Gower Artur L. , Parnell William J. , Abrahams Ian D.
Published: June 2017

Ultrasonic wave propagation through dispersions of particles in liquids is of interest for particle characterization and process monitoring applications. Interpretation of the measurements relies on a theoretical model; we typically use a multiple scattering model which builds on models of scattering by independent particles. We report finite element modeling of an acoustic wave propagating through a liquid and interacting with a particle, using the linearized thermo-acoustic equations for propagation in a viscous liquid. We demonstrate that the interaction of the acoustic field with the particle leads to decaying thermal and shear wave fields in the region very close to the particle. Since the length scale of the thermal and shear decay is orders of magnitude smaller than the propagational mode acoustic wavelength, fine meshing is necessary in the region of the particle/fluid boundary. The simulation results are compared with analytical solutions for scattering of a plane wave by a single spherical particle, provided by Epstein and Carhart [JASA, 25, 533, (1953)] and Allegra and Hawley [(JASA, 51, 1546 (1972)].
Vibroacoustic analysis of table tennis rackets and balls: The acoustics of ping pong
Authors: Russell Daniel A.
Published: June 2017

Table Tennis rackets (ping-pong paddles) exhibit a large number of structural vibration modes which follow patterns first observed by Ernst Chladni and Mary Waller for elliptical plates. Vibrational mode shapes and frequencies obtained through experimental modal analysis will be shown. Acoustic analysis reveals that one structural mode of the paddle, in particular, dominates the sound produced by the ball-paddle impact. The rubber padding provides some damping, and a significant mass loading to the paddle vibrations. The hollow cellulose nitrate balls exhibit a number of vibrational mode shapes typical of a hollow spherical shell, starting at frequencies around 5900 Hz; these will be demonstrated from experimental and computational results. However, the contact time between ball and paddle is such that the lowest acoustic modes of the ball do not contribute to the radiated sound. Instead, the ball appears to radiate sound at a much higher frequency sound (10-12 kHz) most likely due to snap-through buckling common to spherical shells undergoing deformation while impacting a rigid surface at high speeds.
Acoustic cues and linguistic experience as factors in regional dialect classification
Authors: Alcorn Steven , Meemann Kirsten , Walpole Erin , Clopper Cynthia G. , Smiljanic Rajka
Published: June 2017

Listeners rely on a variety of acoustic cues when identifying regional dialects, including segmental, prosodic, and temporal features of speech. The purpose of this study was to examine how native speakers of American English (AE) classify AE talkers by regional dialect when segmental and prosodic features are manipulated in the stimuli they hear; it also considered experience with different regional dialects as an additional factor affecting classification. Native AE listeners residing in Ohio and Texas completed a free classification task in which they heard the same sentence read by 60 monolingual AE talkers and grouped talkers together based on perceived regional similarities. Three versions of the stimuli were presented in a between-subjects design: unaltered, monotonized (f0 flattened to remove intonation cues), or low-pass filtered (to remove segmental cues). Preliminary analyses indicate that performance in the unaltered and monotone conditions was more accurate overall than in the low-pass filtered condition, suggesting that listeners rely on segmental information more than prosodic information for classification. Overall performance was similar across the Ohio and Texas listener groups for all three conditions, but Ohioans outperformed Texans at grouping talkers from the local Midland dialect together, providing preliminary evidence for an effect of experience on classification.
Splitting of Arabic communal dialects at childhood: The case of consonant acquisition in Kfar Kanna Israel
Authors: Rosenhouse Judith K. , Abu Dahoud Jomana
Published: June 2017

Phonetic studies of the acquisition of Arabic dialects are few, both in Israel and in Arab countries where native speakers use Arabic dialects as their daily communication means. The need to know when and how dialects split in the numerous Arabic-speaking communities is important both for the linguistic aspect and for some practical clinical goals. The current study focuses on the acquisition of consonants in Kfar Kanna (near Nazareth), a village in the north of Israel, which has a mixed population of Christian and Moslem inhabitants. Participants were altogether 127 girls and boys, in six age groups (3:00 to 7:00 years old) of those faith communities. The children had normal development and no hearing or speech problems. Our findings show that the pronunciation of the colloquial Arabic consonantal inventory develops with age, as expected. It also assimilates gradually to the adult faith groups' phonetic systems. This is evident, especially in a few distinctive consonants, e.g., /q, D³/. Due to schooling, some effects of the Modern Standard Arabic phonetic system are also evident in the older children's data. This is a first study of communal Arabic dialects development in Israel, as far as we know.
Detection of creaky voice as a function of speaker pitch and gender
Authors: Davidson Lisa
Published: June 2017

Creaky voice in American English speakers (especially women) has been flagged as a negative characteristic, such as in business and radio (Anderson et al. 2014, Glass 2015). However, it is unclear how accurately naïve listeners can identify creaky voice, and what factors facilitate or hinder its identification. American listeners (N = 55) are presented with stimuli from four podcast hosts: a high- and low-pitched male speaker, and a high- and low-pitched female speaker. Other manipulated factors include whether or not the utterance is a full sentence, and whether the utterance is completely modal, completely creaky, or partially creaky (begins modal and ends creaky). After a short familiarization, listeners identify whether 1.5sec utterances contain creaky voice. Results show that listeners are significantly less accurate in identifying creak in both male speakers than in both female speakers, and less accurate when the utterance is partially creaky. For male speakers, listeners are more accurate on fragments than on full sentences. Lower accuracy on male speech may be a combination of smaller, less noticeable differences between average modal and creaky pitch, if listeners heavily rely on low F0 as a cue to creaky voice (Khan et al 2016), and bias toward attributing creak to female voices.
The role of voice onset time in the perception of English voicing contrasts in children’s speech
Authors: Hitchcock Elaine R. , Koenig Laura L.
Published: June 2017

The perception of phonemic voicing distinctions is typically attributed mainly to voice onset time (VOT). Most previous research focusing on voicing discrimination used synthetic speech stimuli varying in VOT. Results of this work suggest that adult listeners show stable crossover boundaries in the 20-35 ms range. However, no research has evaluated how VOT values correspond to adult labeling regardless of whether the intended target is voiced or voiceless. The present study obtained adult labeling data for natural productions of bilabial and alveolar pairs produced by 2-3-year-old monolingual, English-speaking children. Randomized stimuli were presented twice to 20 listeners resulting in 5,760 rated stimuli. Stimuli were categorized as short VOT (<20 ms), ambiguous VOT (20-35 ms) and long VOT (>35 ms). The findings show that listeners demonstrated the greatest accuracy for bilabials (>99%) and alveolars (>92%) when the target matched the expected VOT duration (i.e., doe→short lag and toe→long lag). As expected, ambiguous tokens showed generally lower levels of accuracy across all stimuli although listeners were able to identify the target phoneme with greater than chance accuracy. These findings suggest that other variables such as burst intensity, fundamental frequency, and first formant transition duration contribute to adults’ perception of children's stops.
Acoustic analysis of whispery voice disguise in Chinese
Authors: Zhang Cuiling , Lin Bin
Published: June 2017

This paper investigates the auditory and acoustical features of disguised whispery voices, the acoustic difference between normal (non-disguised) voices and whispery voices, and the effect of whispery disguise on forensic speaker recognition. Recordings of eleven male college students’ normal voices and whispery disguised voices were collected. All their normal and whispery speech was acoustically analyzed and compared. The parameters average syllable duration, intensity, vowel formant frequencies, and long term average spectrum (LTAS) were measured and statistically analyzed. The effect of whispery disguise on forensic speaker recognition by auditory and phonetic-acoustic approach were evaluated. Correlation and regression analyses were made on the parameters of whispery voice and normal voice. To some extent, these simple regression models can be used for parameter compensation in forensic casework.
Power priming and speech perception
Authors: Calloway Ian C.
Published: June 2017

English listeners use information about speaker gender in categorizing a sibilant as /s/ or /ʃ/. This study investigates whether sibilant categorization is influenced by whether cues to speaker gender are congruous and whether self-perceived power in turn influences one’s ability to process incongruous gender cues. One’s self-perceived power, the perceived capacity to control another individual’s resources, can inhibit how one attends to information associated with a social category. Participants were primed experimentally for a high or low degree of self-perceived power. They then performed a forced-choice identification task—for each trial, participants were presented with an auditory stimulus—a word ranging from “sigh” to “shy”—and a visual stimulus—a male or female face—and they indicated whether they heard “sigh” or “shy.” Participant likelihood to respond “sigh” was significantly influenced by speaker gender, whether the gender of the face matched that of the speaker, and the power prime the participant received. For the female voice, both participants responded “sigh” more often when presented with a male face. For the male voice, however, low-power individuals were less likely to respond “sigh” when presented with a female face, while high-power individuals responded similarly regardless of the face presented.