bluuebunny/crossref_metadata_2025 huggingface dataset:
Seemingly simple songs: Black-capped chickadee song revisited
Authors: Sturdy Christopher B.
Published: October 2015

Our lab has been studying songbird communication from an integrative perspective for over 13 years. A significant part of this program involves conducting bioacoustic analyses of vocalizations that are critical to survival. Initially, black-capped chickadees and their chick-a-deecall were our main research focus. In more recent years, we have turned our attention back to the fee-bee song, intensely studied by Weisman, Ratcliffe, and colleagues. Our re-examination of the fee-bee song revealed several, previously unreported features of this seemingly acoustically simple vocalization. We showed that songs contain regionalized cues for dominance status, and that females respond differentially to dominant song playback irrespective of their geographic origin. Moreover, females themselves produce a fee-bee song not previously reported in the literature. Female song is acoustically distinct from male song, and we have used operant conditioning experiments to identify features that can be used to identify sex of the singer. Finally, we have begun to explore neural response to different vocalizations, including song, and found that responses vary by singer, listener, and vocalization type. Our current efforts are aimed at unraveling the acoustic basis of communication in this nearly ubiquitous North American species.
How birds perceive the auditory scene
Authors: Dent Micheal L.
Published: October 2015

How are birds able to effectively communicate for survival? How do they separate auditory objects that overlap on the tympanum? How do they perceive distance, overlapping sounds, and noisy signals? In many ways, birds decipher the auditory world in the same way humans do. We know they use intensity as a primary cue for distance perception, that they spatially segregate signals and noise to better hear certain signals, that they are susceptible to auditory illusions, and that spectrotemporally complex and biologically relevant signals are often better isolated than simple tonal sounds. We know these things and more from psychophysical studies in the laboratory where birds are trained to be reliable observers, using operant conditioning techniques in a controlled environment. Subjects are trained to peck keys for food reinforcement when they detect, discriminate, identify, or localize sounds. Years of research on the foundations of hearing in these animals leads us to the present day, where birds are asked much more complicated questions in studies that more closely resemble their natural auditory world. For birds, being able to hear and isolate communication signals in the environment is crucial, and we have discovered much about how they do this in complex acoustic environments.
Context-dependent categorical perception in a songbird
Authors: Nowicki Stephen
Published: October 2015

The division of continuously variable acoustic signals into discrete perceptual categories is a fundamental feature of human speech. Other animals have been found to categorize speech sounds much the same as humans do, although little is known of the role of categorical perception by animals in their own natural communication systems. A hallmark of human categorical perception of speech is that linguistic context affects both how speech sounds are categorized into phonemes, and how different versions of phonemes are produced. I first review earlier findings showing that a species of songbird, the swamp sparrow, categorically perceives the notes that constitute its learned songs and that individual neurons in the bird’s brain show categorical responses that map onto its behavioral response. I then present more recent data, using both discrimination and labeling tests, that show how swamp sparrows perceive categorical boundaries differently depending on context. These results demonstrate that there is a more complex relationship between underlying categorical representations and surface forms in the perception of birdsong. To our knowledge, this work suggests for the first time that this higher-order characteristic of human phonology is also found in a nonhuman communication system.
Vocal conditioning with playback of two template sounds in budgerigars
Authors: Seki Yoshimasa , Dooling Robert J.
Published: October 2015

We examined a capability of budgerigars to produce a similar vocal pattern to a sound stimulus presented immediately just before. For this purpose, we trained birds using an operant conditioning procedure. In the training, two types of the birds’ own call were used as the auditory stimuli. Then, they were tested by probe stimuli (another vocal pattern of the subjects’ own, other birds’ vocalization). At test trials, the birds vocalized not any similar sounds in response to the probe stimuli but one of the vocal patterns which was produced at the training trials. Then, we attempted to train the birds to produce vocal patterns following playback sounds which were slightly changing as the trials went. 24-step intermediate sounds between two birds’ own vocal patterns were synthesized. Those intermediate sounds were shifting step-by-step from one to the other at each trial in a single session. Eventually, a bird created some novel sounds which were similar to those intermediate stimuli and had been never produced at the training trials. Taken together, the birds did not use the playback sounds as the vocal reference under the operant procedure. However, birds might store those playback sounds as the potential vocal repertoire.
Methods and applications for modeling of continuous-wave ultrasound fields
Authors: Mast T. Douglas
Published: October 2015

Techniques are presented for efficient and accurate computation of three-dimensional, continuous-wave radiated fields from ultrasound transducers of canonical geometries. Fields of flat circular pistons are computed using exact series expressions based on orthogonal function expansions of the Rayleigh integral. Fields of concave circular pistons are computed using analogous series expansions for an integral of effective source contributions over the radiating surface; this approach accurately approximates radiated fields of many focused ultrasound transducers of interest. Fields of flat and focused rectangular transducers are computed using closed-form expressions based on a modified Fresnel approximation; accurate fields are obtained at distances large compared to the radiating aperture dimensions, so that the near field for large transducers can be accurately simulated by subdividing the radiating aperture. Efficient methods for field computation facilitate design optimization for therapy and imaging devices and methods. In simulations of therapeutic ultrasound, local heat deposition is proportional to the squared magnitude of the radiated acoustic pressure. For pulse-echo imaging, beamformed echo signals can be simulated by appropriate convolutions of transmit-receive beam products with a three-dimensional model of the scattering medium. Illustrative examples include simulation of ultrasound thermal ablation, passive cavitation imaging, and pulse-echo B-mode and echo decorrelation imaging.
Ultrasound imaging of the coefficient of nonlinearity
Authors: Demi Libertario , van Sloun Ruud J. , Shan Caifeng , Verweij Martin D. , Mischi Massimo
Published: October 2015

Cardiac ablation (CA) is increasingly used to treat atrial fibrillation. However, long-term success is relatively low, and the procedure carries serious risks. To this end, we are developing a β (coefficient of nonlinearity) imaging method that may be employed to perform both tissue characterization and real time temperature estimation to respectively plan, monitor, and execute optimal CA. Starting from a one-dimensional generalized form of the Westervelt equation, we derived an analytical procedure for extracting β which is then further adapted to echo-mode. To evaluate the method performances, in-silico and in-vitro experiments were performed. First, one- to three-dimensional simulations including linear array scanning of three-dimensional objects were obtained with the INCS method. Next, the ULA-OP scanner was used with an Esaote LA332 linear-array to image a phantom consisting of 2-layers obtained as a mixture of oil, gelatin and water. Varying the percentage of oil (β similar to fat), different β values were obtained for the two layers. Both in-silico and in-vitro results show the capability of the method to estimate β variations. Compared to existing methods, the proposed approach provides more stable estimations (spatially) and does not require a special transducer or set-up, being more easily applicable in a clinical setting.
Characterization of medical ultrasound fields using modeling with a boundary condition obtained from measurements
Authors: Khokhlova Vera , Yuldashev Petr , Rosnitskiy Pavel , Karzova Maria , Sapozhnikov Oleg , Maxwell Adam , Cunitz Bryan , Bailey Michael , Crum Lawrence , Kreider Wayne
Published: October 2015

Numerical modeling is becoming an important metrological tool for accurate characterization of ultrasound fields generated by medical transducers in water and in situ. While acoustic propagation equations are well established, setting a boundary condition relevant to the experiment still remains a critical problem. Two methods differing in complexity are described to address this problem. The first method comprises 3D simulations of the Westervelt equation with a boundary condition determined from acoustic holography measurements. The second, simpler method utilizes simulations based either on the KZK or Westervelt equation with an equivalent source boundary condition obtained by matching linear simulations to low-amplitude beam profiles along and transverse to the axis of the source. Calculations with both methods are compared to fiber optic hydrophone measurements of 2D phased therapeutic arrays, a 128-element diagnostic probe, and strongly focused single-element transducers. It is shown that the 3D Westervelt model with holographic boundary condition can accurately simulate the entire nonlinear ultrasound field. The simplified methods based on an equivalent source are shown to give accurate results in the focal zone of the transducers, even when shocks are present in the focal waveform. [Work supported by NIH EB7643, EB016118, DK043881, and RSF 14-12-00974.]
Angular spectrum methods for nonlinear ultrasound wave propagation: Mathematical development and implementation
Authors: Varray François , Basset Olivier , Cachard Christian
Published: October 2015

The use of simulation tools is required in many domains, especially in medical ultrasound (US). In US propagation, the nonlinear wave distortion is used in clinical application as harmonic or contrast imaging. Various methods exist to compute and evaluate the harmonic increase depending on the medium and the probe geometry. Among these methods, the angular spectrum method (ASM) proposes good compromise between accuracy and computation time. After expressing the wave propagation equation into Fourier domain, either a quasi-linear approximation or a slowly variation envelope approximation (SVEA) can be used to evaluate the harmonic increase which provide two tools. SVEA overcomes the quasi-linear limitation and evaluates the nonlinear frequency interaction during the propagation. A GPU implementation and optimization of both techniques allow a fast computation of the full nonlinear propagation. For both techniques, the computed fields are close and validate our proposed approach. Thanks to the GPU implementation, the computation is strongly reduced compare to Matlab or C version. Of course, some limitations in ASM are present, such as the one way computation of the US field, which did not allow the computation of reflection for media with inhomogeneities in density, celerity, attenuation, or coefficient of nonlinearity.
Computed tomography-based aberration correction for trans-skull acoustic focusing: Comparison of simulations and measurements with focused ultrasound brain systems
Authors: Jones Ryan M. , Huang Yuexi , Pajek Daniel , Hynynen Kullervo
Published: October 2015

Clinical focused ultrasound brain systems currently employ computed tomography (CT)-based phase and amplitude corrections to mitigate skull-induced distortions and restore an acoustic focus at the intended target. In this study, acoustic measurements were conducted using two transcranial magnetic resonance-guided focused ultrasound systems (ExAblate 4000, InSightec, Haifa, Israel) operating at 230 and 650 kHz. The acoustic fields generated by the devices within intact, water-filled ex-vivo human skulls near the geometric focus were mapped using a 0.5 mm diameter needle hydrophone. In addition, the signals transmitted from each individual array element were captured at various locations within the skull cavity. These measurements were repeated without the presence of the skull in order to determine the element-specific aberrations induced by the cranial bone for each target position. The experimental measurements were simulated using three previously developed transcranial ultrasound propagation models: an analytical method similar to that currently employed by clinical brain systems, a multi-layered ray-acoustic approach, and a three-dimensional full-wave propagation model based on the Westervelt equation. We will present a comparison of the models based on their computational complexity as well as their ability to both predict the phase and amplitude aberrations induced by the skull and reproduce the measured in-situ pressure field distributions.
Comparison between computational and experimental methods for the characterization of therapeutic ultrasound fields
Authors: Maruvada Subha , Liu Yunbo , Soneson Joshua E. , Herman Bruce A. , Harris Gerald R.
Published: October 2015

Analytical modeling of medical ultrasound fields has been developed by the FDA to aid in pre-clinical characterization of therapeutic ultrasound devices. In order to assess this publicly available software, called the HIFU Simulator, acoustic and thermal measurements of power, pressure/intensity and temperature distribution have been performed for comparison. Measurement and modeling issues include using hydrophones and radiation force balances at therapeutic power levels, validation of simulation models, and tissue-mimicking material (TMM) development for temperature measurements. To better understand these issues, a comparison study was undertaken between simulations and measurements of the HITU acoustic field distribution in water and TMM, and temperature rise in TMM. For the specific conditions of this study, the following results were obtained. In water, the simulated values for p + and p- were 3% lower and 10% higher, respectively, than those measured by hydrophone. In TMM, the simulated values for p + and p- were 2% and 10% higher, respectively, than those measured by hydrophone. The simulated spatial-peak temporal-average intensity values in both water and TMM were greater than those obtained by hydrophone by 3%. Simulated and measured end-of-sonication temperatures agreed to within their respective uncertainties (coefficients of variation of approximately 20% and 10%, respectively).
Monitoring hardening of concrete using ultrasonic guided waves
Authors: Zhu Jinying , Sun Hongbin
Published: October 2015

Evaluation of early age properties of concrete is critical for ensuring construction quality of concrete structures. Although ultrasonic wave based methods show potential for monitoring the hardening process of concrete in laboratory, there are many challenges related to sensor installation and data acquisition in practice. In this study, the authors present an ultrasonic guided wave method that uses guided waves in a steel rebar to monitor hardening of surrounding cement paste and mortar. The longitudinal L(0,1) mode guided wave in rebar is excited by an EMAT sensor and received by a piezoceramic P-wave ultrasonic transducer. Continuous measurements during cement hydration were used to monitor the longitudinal wave attenuation resulted from leakage from the rebar to the surrounding cement paste/mortar. Shear wave velocities in cement materials were also monitored at the same time. Experiments were performed on four cement paste samples and three mortar samples. Experimental results demonstrated a strong correlation between the guided wave leakage attenuation and shear wave velocity for all tested samples, and both parameters increase with the age of cement materials.
Characterization of visco-elastic material parameters by means of the ultrasonic polar scan method
Authors: Van Den Abeele Koen , Martens Arvid , Kersemans Mathias , Degrieck Joris , Delrue Steven , Van Paepegem Wim
Published: October 2015

The Ultrasonic Polar Scan (UPS) is a non-destructive technique which insonifies a material spot on a sample using ultrasonic pulses from as many oblique incidence angles ψ(φ,θ) as possible. Mapping the transmitted time-of-flight (TOF) and/or amplitudes as function of the incidence angle ψ(φ,θ) in a polar representation yields a UPS image with intriguing patterns that represent a fingerprint of the local visco-elastic properties. The present paper reports on recent advances in the revival of the UPS technique, involving the construction of an automated high-precision UPS scanner, the implementation of advanced simulation models as well as the development of efficient inversion routines. On the experimental level, unprecedented high quality TOF and amplitude UPS landscapes for a range of orthotropic (fiber reinforced) materials have been obtained. Using numerical simulation models, it can be readily demonstrated that the TOF UPS landscapes are directly connected to the elastic properties of the material, while the signal magnitudes displayed in the amplitude UPS landscapes are merely determined by the viscosity. By developing a coupled inversion scheme using the two landscapes simultaneously, we can achieve a full determination of the visco-elastic tensor. The new advances and inversion scheme will be illustrated in the case of fiber-reinforced plastics.
Preliminary evaluation of the sound absorption coefficient of a thin coconut coir fiber panel for automotive applications
Authors: Lima Key F. , Barbieri Nilson , Terashima Fernando J. , Rosa Victor P. , Barbieri Renato
Published: October 2015

Absorbent materials are fibrous or porous and must have the property of being good acoustic dissipaters. The noise reduction process occurs due to transformation of a part of the sound energy into heat. This process occurs when a sound wave propagates through pores or irregular arrangement of fibers. Sound propagation causes multiple reflections and friction of the air present in the absorbent medium transforming sound energy into heat. The acoustic surface treatment with absorbent material are widely used to reduce the reverberation in enclosed spaces or to increase the sound transmission loss of acoustic panels. In addition, these materials can also be applied to acoustic filters with the purpose to increase their efficiencies. The sound absorption depends on the excitation frequency of the sound and it is more effective at high frequencies. Natural fibers such as coconut coir fiber have a high potential to be used as sound absorbing material. Natural fibers are agriculture waste, manufacturing this fiber is a natural product, therefore an economic and interesting option. This work compares the sound absorption coefficient of a thin coconut coir fiber panel in relation to a composite panel made of fiberglass and expanded polyurethane foam used in the automotive industry. The evaluation of sound absorption coefficient was carried out with the impedance tube technique.
Playability of a bowed string physical model including finite-width thermal friction and hair dynamics
Authors: Maestre Esteban , Spa Carlos , Llimona Quim , Scavone Gary P. , Smith Julius O.
Published: October 2015

We report on the playability of a bowed-string physical model that combines digital waveguide and finite-difference time-domain frameworks. We extend previous approaches by combining a finite-width bow-string interaction model with a dynamic friction model based on simulating heat diffusion along the width of the bow. Bow hair dynamics are incorporated in the bow-string interaction, which includes two transversal string polarizations. The bridge termination is realized using a digital reflectance matrix model obtained from fitting two-dimensional driving-point admittance measurements. We present preliminary results from a playability study in which we explore the establishment of Helmholtz motion in static and dynamic bowing conditions.
Measurements of friction instruments with high-speed camera and subpixel tracking
Authors: Bader Rolf , Pfeifle Florian , Plath Niko , Koehn Christian
Published: October 2015

Instruments working with stick-slip interactions not using a string were popular in the West since the invention of the glass harmonica by Benjamin Franklin in 1751. The Terpodion investigated was built by Buschmann in the mid-19th century as a friction instrument with a keyboard, where bars are pressed against a wooden rotating cylinder producing a sound. Using high-speed camera recordings, the only playable instrument today at the Viadrina museum in Frankfurt a.O. shows sinusoidal vibrations of the bars determining the played pitch while the radiated sound is highly complex. Therefore the instrument shows a fundamentally different stick-slip action compared to bowed instruments. Friction instruments of the East, like the singing bowls also show very sinusoidal-like sounds again caused by the stick-slip interaction. The New Ireland Lounuet, a finger-rubbed wooden block has both, a sinusoidal motion as well as a highly complex one which is to imitate bird and frog sounds. A systematic view on the different stick-slip interactions is suggested.
An unconditionally stable scheme for simulation of stick-slip processes
Authors: Chatziioannou Vasileios , Kausel Wilfried
Published: October 2015

Stick-slip processes are often encountered in musical instruments, the most notable example being that of a bowed violin string. Modeling such nonlinear interactions has been often attempted in the field of Musical Acoustics, using a variety of time-stepping algorithms. The nonlinear nature of such problems requires careful analysis of the stability properties of the developed numerical schemes. This is usually carried out using energy based methods, in which case one needs to consider the continuous exchange of energy between the bow and the bowed object. In this paper an unconditionally stable scheme is proposed for the simulation of a bowed, lumped mass. The stability of the algorithm is ensured due to the presence of an invariant quantity. The numerical results are in agreement with well established algorithms, with the proposed methodology possessing no stability constraints and being extensible to a wide range of (lumped and distributed) acoustic systems.
Differences between ANSI S3.4-2007 and the proposed ISO532-2
Authors: Moore Brian C.
Published: October 2015

The ANSI standard for the calculation of loudness (ANSI S3.4-2007) is based on the model developed by Moore, Glasberg and co-workers, and uses the assumption that a diotic sound is twice as loud as that same sound presented monaurally. However, recent data suggest that loudness summation across ears is less than assumed in the ANSI standard. This was taken into account in the revised loudness model of Moore and Glasberg [J. Acoust. Soc. Am., 121, 1604–1612, 2007] using the concept of “binaural inhibition”, whereby the signal at one ear inhibits the internal response to a signal at the other ear. This model predicts that a diotic sound is 1.5 times as loud as that same sound presented monaurally, and it forms the basis for the proposed ISO532-2 standard. The revised model also gives reasonably accurate predictions of loudness in cases where the sounds differ across the two ears, for example, sounds recorded via a dummy head. An extension of the model to deal with time-varying sounds has been shown to give accurate predictions of loudness for a variety of technical and musical sounds. It is proposed that the revised and extended model be used as the basis for a new ANSI standard.
Determining binaural summation for stationary signals across the frequency spectrum
Authors: Novak Colin J. , Charbonneau Jeremy
Published: October 2015

The concept of binaural summation has been widely accepted; however, the value of summation, and the manner in which it is applied, is still under a great deal of debate. This research is an investigation of the binaural summation mechanisms through the use of a loudness comparison experiment for pure tones. Preliminary results have concluded that for pure tones presented at 40 dB the amount of summation increases with frequency from approximately 2 dB at 40 Hz up to 8 dB at 10 kHz. Due to the low hearing threshold at 40 dB, the experiment was modified such that the hearing threshold of each individual is collected in order to presented each signal at a fixed amplitude above the threshold of hearing for each frequency (i.e., a sensation level of 20 dB(SL)). However, similar outcomes have been found using this approach, thus supporting the conclusions that binaural summation does exist and is found to increase at defined increments with increasing frequency for pure tones. The eventual outcome of this work is to improve the existing loudness metrics to allow for the input of binaural measurements taken using binaural mannequins.
On time-varying loudness and nonlinearly propagated sound
Authors: Marshall Andrew , Oelschlaeger Karl , Belzer Emily
Published: October 2015

Time varying loudness models have been found to be highly correlated with subject judgments for many sources of noise. Among these sources are impulsive sounds such as sonic booms, blast noise, and thunder. Aside from the short temporal duration, all of these sound sources are distinctive in that each is of high enough amplitude to have nonlinear propagation effects occur, which change the temporal and spectral character of a signal over distance. Because of this, it is possible that differences in how a model handles spectral content may result in differences in loudness predictions over distance. A series of simulated nonlinear sources were propagated and its time-varying loudness calculated from both the Moore & Glasberg and Zwicker model. These predictions will be compared to examine how these models differ when the spectral content of the signal changes. Other parameters, including historical level metrics and those derived from loudness time histories, such as the loudness time derivative, will also be discussed.
Effects of time-varying grain shape on combustion instability of a solid rocket motor
Authors: Park Taeyoung , Lee Hunki , Ohm Won-Suk , Lee Dohyung
Published: October 2015

A common approach to modeling combustion instability in a rocket propulsion system is to express the pressure oscillation in a combustor as a superposition of acoustic modes with time-varying amplitudes. Here, the tacit assumption is that the acoustic modes themselves remain more or less the same over the entire burning time. However, in the case of a solid rocket motor, the grain shape changes significantly as combustion progresses. This can gradually alter the shapes and frequencies of the acoustic modes, the influence of which on combustion instability has rarely been discussed in the existing literature. In this study, the effects of time-varying grain shape are modeled by introducing a slow time scale associated with the progressive burning of the grain. The resulting model equation accounts for the evolution of acoustic modes as well as their growth/decay in amplitude. Predictions with and without the use of the slow scale are compared with respect to measurements of a static firing test.
Multiresolution non-stationary techniques for the characterization of transient pressure signals embedded in broadband plume noise
Authors: Alvord David , Medda Alessio
Published: October 2015

The acoustic environment generated by the Space Shuttle propulsion system historically was considered one of the most complex rocket noise environments to predict of NASA’s heritage rockets. After the Space Shuttle was retired in 2011, the Space Launch System (SLS) architecture chosen to succeed the shuttle will generate an even more complex acoustic environment than Space Shuttle. Both Space Shuttle and SLS have dual first stage propulsion systems consisting of two Solid Rocket Boosters (SRBs) and three (Space Shuttle) or four (SLS) RS-25 LH2/LOX engines. The additional complexity for the SLS acoustic environment arises due to the in-line propulsion configuration (as opposed to the offset configuration for Space Shuttle) firing both SRB and liquid engine plume into the same exhaust duct at liftoff. For Space Shuttle, the offset configuration meant each acoustic phenomena was separable and could be predicted and analyzed individually. For SLS, the in-line configuration means the IOP waves (one per SRB) are injected directly into the steady state plume meaning the events can no longer be assumed separable. This paper discusses data from a scaled down configuration and applies wavelet analysis in attempt to extract and characterize an injected transient blast wave from steady state plume noise.
Quantitative nonlinearity in subsonic and supersonic model-scale jet noise
Authors: Miller Kyle G. , Reichman Brent O. , Gee Kent L. , Neilsen Tracianne B. , Atchley Anthony A.
Published: October 2015

Understanding the impact of jet noise, including annoyance due to crackle, can be improved by quantifying the nonlinearity in a signal with a single-microphone measurement. An ensemble-averaged, frequency-domain version of the generalized Burgers equation has been used to find a quantitative expression for the change in sound pressure level spectrum, Lp, with distance, r, due to the separate effects of geometric spreading, absorption, and nonlinearity. The nonlinear term, based on the dimensionless nonlinearity indicator known as “Q/S,” has been used to characterize the frequency-dependent nonlinearity as a function of angle and distance in subsonic (Mach-0.85), overexpanded (Mach-1.8), and ideally expanded (Mach-2.0) model-scale jet data. Analyses show that nonlinear effects in the Mach-2.0 data are about twice as strong as those in the Mach-1.8 data, but such effects are completely absent in the Mach-0.85 data. [Work supported by the AFRL SBIR program.]
Estimating aircraft noise levels and spectra from aircraft flyover and ground operations
Authors: Wall Alan T. , McKinley Richard L.
Published: October 2015

The noise from military aircraft operations can adversely affect people within the civilian community near an airbase and within the military community living and operating within the confines of the airbase. The aircraft noise levels and spectra should be estimated to determine the building noise attenuation treatments to achieve the desired interior noise levels. This presentation describes a method to estimate the noise levels and spectra from both ground operations and flyover operations of high performance military jet aircraft for the community near the airbase and the airbase proper. Sound levels are predicted over a typical airbase region using an equivalent source model for a fighter jet aircraft and atmospheric propagation modeling. Overall level contours are generated over the entire area, and spectral levels are predicted at desired points corresponding to noise sensitive building locations. [Work supported by USAFRL through ORISE.]
Clear speech adaptations across the lifespan
Authors: Hazan Valerie
Published: October 2015

Talkers need to be able to alter their speech production in order to communicate effectively in conditions in which there are acoustic or linguistic barriers to communication. The clear speaking styles that result from such adaptations have been well documented, but mostly for young adult talkers. As a skilled aspect of speech production, the ability to make such adaptations may develop late during acquisition and be affected by reduced motor or cognitive control in older talkers. In a series of studies, we are investigating how speech adaptations in challenging communicative conditions change across the lifespan: in children aged 9 to 15 years, in young adults, in older adults aged 65 and above. In all three studies, recordings were made while talker pairs complete a cooperative problem-solving task (diapix) when communication was easy or when a communication barrier was placed on one talker. Acoustic analyses have shown adaptations to speaking rate, intensity, fundamental frequency characteristics, vowel formant space. While young adults seem adept at making adaptations that are well suited to overcome the specific interference experienced by their interlocutors, younger talkers appear to make less nuanced adaptations. We will discuss factors affecting such speech adaptations across the lifespan.
Phonetic and lexical influences on changes across the lifespan
Authors: Harrington Jonathan , Reubold Johann U.
Published: October 2015

The study considers longitudinal studies over several decades within the same individual in order to determine whether phonetic sound change takes place initially in more frequent words. The focus of the analysis was on the vowels of the Christmas Broadcasts by Queen Elisabeth II over several decades and in Alistair Cooke's Letter from America broadcasts. For the first of these, a re-analysis of the phonetic lowering of the vowel in the lexical set TRAP and of tensing of final lax vowel in HAPPY showed no effect of lexical frequency on sound change. The focus of analysis in the second was during a period in which the speaker was shown to acquire General American characteristics after emigrating to the United States from Britain, but then in later life to revert over a 5–10 year period back toward characteristics of British English Received Pronunciation. This reversion is shown to take place at a faster rate in lexically frequent words. While the evidence overall for lexically gradual changes is equivocal, the changes in both speakers are most appropriately modeled as a leveling due to variation in dialect contact: increasingly with middle class speakers for the Queen; decreasingly with American English speakers for Cooke.
Time-domain Helmholtz-Kirchhoff integral for forward surface scattering in a refractive medium
Authors: Choo Youngmin , Song Heechun , Seong Woojae
Published: October 2015

Time-domain Helmholtz-Kirchhoff integral (H-K integral) for forward surface scattering is extended to a refractive medium. Ray theory is applied to obtain the Green’s function, while the normal derivative in the integral is evaluated analytically using a ray geometry along with the ray-based Green’s function. This approach allows for stationary phase approximation which reduces the surface integration to a line integration. For high-frequency signals with a narrow bandwidth, an asymptotic form of the time-domain H-K integral then can be derived using the Fourier transform. The pressure field scattered from a sinusoidal surface wave in a constant-gradient sound speed profile is evaluated and compared to the result based on a conventional ray model.
A modeling approach to scattering and reverberation in shallow water
Authors: Ivakin Anatoliy
Published: October 2015

A physics-based modeling approach is described that allows prediction of reverberation in complex shallow water environments. An integral expression is presented for the backscatter intensity with a factorized integrand comprised of two kernels, the two-way propagator and the scattering kernel. The propagator is defined by Green’s function, describes the local intensity, and can be calculated using available models, such as PE, normal modes, or ray approximations. An expression for the scattering kernel is obtained using a unified approach to volume and roughness scattering [Ivakin, JASA Feb. 1998], and represents a sum of volume and roughness scattering coefficients. They are specified for sea-water column and rough heterogeneous seabed with continuous spatial fluctuations of compressibility and density, and/or discrete randomly distributed targets, such as bubbles, fish, shells, and others. Results of numerical simulations for shallow water reverberation time/range series, based on a PE propagation model, are presented, and potential contributions of different mechanisms of scattering are compared and discussed. The approach is applied to consider reverberation in a complex shelly sand/mud environment, such as one at the Target and Reverberation Experiment 2013 (TREX), and results in model/data comparisons based on analysis of TREX acoustic scattering data and environmental ground truth measurements. [Work supported by ONR-OA.]
Model/data comparisons of high-frequency backscattering from well-characterized sand sediment
Authors: Hefner Brian T.
Published: October 2015

In the Spring of 2010, acoustic backscattering from an artificially-smoothed sand sediment was measured in the NSWC PCD test pond. The measurements were made at frequencies from 200 to 500 kHz as a function of grazing angle. The residual roughness of the smoothed surface was measured using a laser line scanner while the sediment parameters were determined through diver core analysis and sound speed and attenuation measurements. At the time of the experiment, it was not possible to characterize the volume heterogeneities within the sediment. Subsequent analysis of historic conductivity probe measurements collected in the same test pond under similar conditions has been used to fill this gap. With this additional dataset, the environmental characterization of the sediment places significant constraints on models of scattering from both the sediment roughness and the subsurface volume heterogeneities. Using the sediment parameters, the predictions of small perturbation roughness and volume scattering theories are compared to the data when the sediment is modeled as a fluid and as a poroelastic medium. The effect of the measured porosity fluctuations on sound propagation within the sediment is also examined using a recently developed scattering loss model. [Work supported by ONR.]
Reverberation modeling approximately accounting for three-dimensional forward scattering effects
Authors: Thorsos Eric I. , Yang Jie , Henyey Frank S.
Published: October 2015

A transport theory approach has been developed for modeling shallow water propagation and reverberation at mid-frequencies with emphasis at 1–3 kHz. With this approach, sea surface forward scattering can be taken into account in a 2-D (range-depth) approximation. While the effects of surface forward scattering on transmission loss are found to be modest (1–2 dB), the corresponding effects on reverberation level for typical conditions can be significant (~10 dB), even though bottom backscatter dominates reverberation in shallow water. An attempt to make data/model comparisons brought out the issue of the proper way of using the 2-D (in horizontal plane) surface roughness spectrum to model forward scattering with a 2-D (range-depth) propagation model. For reverberation modeling, we are investigating the approximation of preserving the distribution in vertical scattering angles in reducing the full 3-D problem to a 2-D (range-depth) problem when using the traditional N ' 2-D approach. A description of the method will be given, followed by data-model comparisons for TREX-13. [Work supported by ONR Ocean Acoustics.]
Environmental factors that contribute to high frequency bottom loss variability
Authors: George Jacob , Harvey David W. , Lowrie Allen , Conner Lori S.
Published: October 2015

We discuss three factors: short range sediment variability, bio-attenuation, and seafloor roughness. In a previous presentation (ASA 2013), we have shown that statistical distributions of bottom loss values derived from measured transmission loss (TL) are nearly invariant to measured sediment properties such as sound speed, density, and porosity. To test if this surprising result was caused by under-sampling of sediment cores, three TL runs were done in 2014 when cores were collected at 1 km intervals. The results of these showing short range variations will be discussed. Among the stations in our HFBL database we have found possible evidence for bio-attenuation due to fish (anchovies) swim bladder resonance (Diachok-Wales, JASA 2005). Finite element modeling of a TL station has shown that seafloor roughness can explain the observed frequency dependence of HFBL values (Isakson, report to NAVO). All these will be discussed.
Annoyance perception of complex multi-tone noise signals in both harmonic and inharmonic structures within the built environment
Authors: Lee Joonhee , Wang Lily M.
Published: October 2015

Assorted building mechanical systems generate tonal components within the background noise of built environments. In most cases, this type of noise includes multiple tones in harmonic or inharmonic structures rather than a single tone. However, there is limited information on the comprehensive annoyance caused by multiple tones as perceived by human occupants. Two current standards, ISO 1996-2 and ANSI S1.13, propose calculation methods to address tones in noise, but those methods only analyze the tones individually. This paper aims to investigate how each tone contributes to overall annoyance perception when complex tones are present in background noise. Noise stimuli with five-tone complexes between 125 Hz to 2 kHz were artificially generated for subjective testing. The levels of each tone were randomly adjusted for every trial, and both harmonic and inharmonic structured tone complexes were utilized. Ten musically trained subjects participated in the subjective test involving paired comparisons. Each participant was asked to choose which noise stimulus is more annoying between two noise signals. Perceptual weighting analysis is applied to the results to compute a spectral weighting function for overall annoyance. The performance of the derived spectral weighting function is examined against annoyance ratings of actual building mechanical noises.
Evaluation of a real-time convolution system for perception of self-generated speech in simulated rooms
Authors: Whiting Jennifer K. , Leishman Timothy W. , Eyring Nathan G. , Berardi Mark L. , Rollins Michael K.
Published: October 2015

A real-time convolution system has been developed to quickly manipulate the auditory experiences of human subjects. The system is used to study perceptions of self-generated speech and music, and responses of talkers and musicians to varying acoustical conditions. It allows talkers in an anechoic environment to experience simulated room responses excited by their own voices. While their direct sound travels directly to their ears, they hear convolved room responses via specialized headphones spaced away from their heads. This presentation discusses the system’s development, as well as its objective and subjective validations. Several existing rooms were modeled using EASE. Oral-binaural room impulse responses (OBRIRs) from these models were generated and implemented with the convolution system. Binaural recordings and measurements from the rooms were also made using a G.R.A.S. KEMAR mannequin. Objective comparisons of the OBRIRs from the measurements and simulations were explored in the investigation. Subjective evaluations of auralizations made from the OBRIR measurements and simulations, and binaural recordings, followed from A/B listening and speaking tests. In the latter, participants spoke in the various simulated acoustical environments and compared and rated the effects of each experience.
A case study investigation of the indoor environmental noise in four urban South African hospitals
Authors: van Reenen Coralie A.
Published: October 2015

This multiple case study was designed to investigate acoustics in multi-bed general wards in four South African hospitals. Evidence-based research shows that a quiet indoor environment has positive outcomes for hospital patients and staff. Though international guidelines define noise limits in hospitals, numerous studies world-wide reveal that few hospitals, if any, comply. The goal of this research was to determine whether hospital design paradigms in South Africa should be changed to improve the acoustic environment based on the findings of an acoustic assessment. The acoustic conditions in wards were assessed in terms of sound levels, user opinions, and architecture. The objectives were to determine whether the sites comply with guidelines, to determine user perceptions of noise, and to determine whether design factors influence the noise. It was found that the average sound levels exceeded the guidelines, yet the overall user perception was that noise is not disturbing. Layout and workflow have a likely influence on noise, requiring further research with particular reference to the difference found between patient and staff perceptions of sound. Further discussion pertains to the interpretation, application, and relevance of noise guidelines in an operational hospital environment, recommending further extensive research of human responses to noise exposure.
Acoustical study of historical large room for a contemporary use: The oratory of Albergo dei Poveri in Genova
Authors: Chiari Anna , Pittaluga Ilaria , Schenone Corrado , Borelli Davide
Published: October 2015

The conversion of deconsecrated religious buildings in conference halls or music auditoria is nowadays frequent, especially throughout Italy and Europe, although in most cases these rooms are under artistic and architectural preservation due to their historical heritage value. In this way, acoustic control interventions in such spaces, generally characterized by high reverberation time values, tend to be highly complex. The Oratory of “Albergo dei Poveri” building in Genova, transformed during the 90s in the Auditorium of the Departments of Law and Political Sciences of the University of Genova, faced these needs. After several interventions regarding the installation of sound systems and acoustical curtains, nowadays the acoustical features of the room are not still sufficient for the achievement of the adequate acoustic comfort. In this paper, the acoustic analysis of the hall has been evaluated and effective correction interventions at the same time compliant and non-invasive with the architectural constraints have been designed and investigated. A numerical model of the room was implemented through computer simulations and the model was validated by in situ measurement campaigns. Then, the numerical model was used to develop the subsequent design-scenarios calculations.
Assessing the range of spatial impression metrics from varying source position across a stage in assorted performing arts venues
Authors: Cho Sungbeen , Wang Lily M.
Published: October 2015

A listener’s perception of sound in the built environment is determined by various physical factors such as the size and form of a space, and shape and finishing of materials. Spatial impression is a term used to describe the spatial perception of the auditory field by listeners, and a number of metrics have been proposed to quantify this, including Interaural Cross-Correlation Coefficient (IACC) and Lateral Energy Fraction (LEF). While values for these metrics have been presented for a number of performing arts venues, few investigations have studied the range of these metrics within a specific venue, particularly as a source moves across the stage. This paper assesses data from both computer-simulated and measured rooms on how IACC, LEF, and Interaural Level Differences (ILD) vary within a venue, due to early reflections, as the source location varies across the stage. How greatly do the ranges of these metrics differ with source location? The range and values of these spatial impression metrics due to source movement may be another way in which a venue’s spatial impression can be quantified and compared, correlating to how a listener at a fixed location spatially perceives sound sources within that room.