bluuebunny/crossref_metadata_2025 huggingface dataset:
Computational issues in natural auditory scene analysis
Authors: Lewicki Michael S. , Olshausen Bruno A. , Surlykke Annemarie , Moss Cynthia F.
Published: May 2015

Scene analysis is a complex process involving a hierarchy of computational problems ranging from sensory representation to feature extraction to active perception. It is studied in a wide range of fields using different approaches, but we still have only limited insight into the computations used by biological systems. Experimental approaches often implicitly assume a feature detection paradigm without addressing the true complexity of the problem. Computational approaches are now capable of solving complex scene analysis problems, but these often defined in a way that is of limited relevance to biology. The challenge is to develop approaches for deducing computational principles relevant to biological systems. I will present the view that scene analysis is a universal problem solved by all animals, and that we can gain new insights by studying the problems that animals face in complex natural environments. From this, I will present framework for studying scene analysis comprising four essential properties: (1) the ability to solve ill-posed problems, (2) the ability to integrate and store information across time and modality, (3) efficient recovery and representation of 3D scene structure, and (4) the use of optimal motor actions for acquiring information to progress toward behavioral goals.
Listening through the ears of echolocating Myotis daubentonii bats hunting in groups
Authors: Surlykke Annemarie , Olsen Mads N. , Mol Carien
Published: May 2015

Echolocation allows bats to orient and catch insects in the dark. One intriguing question is how bats are able to recognize their own echoes when hunting in groups. Bats can adjust their call frequency, but this strategy may not be efficient for species like Myotis daubentonii emitting broadband frequency modulated signals. However, the actual masking may be reduced for bats like M. daubentonii emitting short directional signals with low duty cycle. We used a 12-microphone array and infrared camera to record flight and vocal behavior of groups of Daubenton’s bat hunting over a river in the field. We used flight path reconstructions to analyze the acoustic world from the bat’s perspective. For the focal bat, we reconstructed (1) its own emissions, (2) the pulses from conspecifics nearby, (3) its own insect echoes, and (4) insect echoes from pulses of the other bat. The data showed that when two bats fly together echoes were only rarely overlapped by the other sounds. We here provide a framework for obtaining detailed information of flight and echolocation behavior in complex natural surroundings, emphasizing the importance of adapting a “bat’s viewpoint” when studying natural echolocation.
Exploitation of nonlinear acoustical effects of air bubbles in water for a bubble/target discriminating sonar
Authors: Lee Kevin M. , Wilson Preston S.
Published: May 2015

Target detection by traditional sonar can be undermined by air bubbles in various environments, including the surf zone, within gas-bearing sediments, or within seagrass beds. Bubbles introduce a variety of strong acoustical effects, including the onset of many nonlinear effects at sound pressure levels far below that required in bubble-free water. This paper describes laboratory tank experiments demonstrating a bubble/target discriminating sonar that exploits some of these nonlinear effects. Bubble plumes were generated in the tank by releasing compressed air through a porous ceramic plate. Rigid targets were also positioned at various locations in the tank. A high amplitude driving pulse excited translation of bubbles in the water column yielding Doppler signatures from conventional imaging sonar, while Doppler signatures were absent from the heavy rigid targets ensonified by the same driving signal. For sufficient bubble density, subharmonic generation was also observed in regions of bubbly water, but not from the rigid targets. The goal of this work is to use one or both of these nonlinear effects to identify and reduce clutter caused by bubbles and improve target detection for sonar operation in areas where bubbles are present. [Work supported by ARL:UT and ONR.]
Acoustic preservation: Preventing unseen loss in our historic sites
Authors: Jordan Pamela
Published: May 2015

Soundscape research examines the vital role that sound plays within the integrated complexity of any specific environment, be it a rural landscape, cityscape, or indoor scenario. Historic preservation, on the other hand, generally seeks to safeguard shared built histories and frames the physical conservation of a site by prioritizing certain elements or activities for contemporary audiences. These designed interventions function similarly whether they are in “nature” or in the attic of a building. Yet the acoustic dimension of a site is seldom considered a vital part of preservation work. Even more rarely is the aural environment considered a contributing historic resource. Nevertheless, the soundscape of a place is an important cultural resource to learn from and protect—one that can potentially unlock a new dimension of understanding in a site’s past. This submission presents current work being carried out in Berlin that bridges the gap between preservation practice and soundscape research. Acoustic concerns specific to historic sites will be discussed through case study examples. A discussion of developing methodologies for mapping soundscapes of historic sites will follow.
Innovative tools for urban soundscape quality: Real-time road traffic auralization and low height noise barriers
Authors: Jolibois Alexandre , Defrance Jérôme , Maillard Julien , Jean Philippe , Jagla Jan
Published: May 2015

Although noise exposure has been unanimously recognized for its impacts on people’s health, noise is still a current problem in many cities across the world. Besides, most noise analysis tools are based on long term average levels, which were initially meant to be used for inter-city infrastructures and are therefore insufficient to quantify the soundscape quality in urban environments. In this paper, we present some of the recent developments and results regarding two classes of innovative tools dedicated to the improvement of urban soundscape quality. First, recent advances in the field of real-time auralization of road traffic noise are presented and the benefit of realistic sound field restitution as a new analysis tool for the evaluation of urban planning projects is discussed and demonstrated. Second, some promising results regarding innovative urban noise reducing devices, taken among other works from the European project HOSANNA, are presented. In particular, the potential of vegetation and low height noise barriers are emphasized, from a numerical and experimental point of view. Results show that these devices can significantly enhance the soundscape quality in specific places, and therefore can help in the creation of so-called “quiet areas” within urban environments.
Real-time implementation of multi-channel active noise control systems for infant incubators
Authors: Liu Lichuan , Wu Xianwen
Published: May 2015

High noise in infant incubators results in numerous adverse health effects, which have lifelong consequences for neonatal intensive care unit (NICU) graduates. This paper presents multi-channel feed forward active noise control (ANC) systems for infant incubators. Then, the proposed algorithm is implemented by using Texas Instrument TMS320 C6713. The real-time experiment results show that the proposed algorithm is effective in canceling the noises of infant incubators in real NICU environment
Active control of cylindrical shells using the weighted sum of spatial gradients control metric
Authors: Aslani Pegah , Sommerfeldt Scott D. , Blotter Jonathan D.
Published: May 2015

Often it is desired to reduce the sound radiated from vibrating structures, including cylindrical shells. Active structural acoustic control (ASAC) provides a means to control the structural radiation at low frequencies efficiently and effectively. The technique of using the weighted sum of spatial gradients (WSSG) as a control metric has been developed previously for flat structures. This paper will investigate control of WSSG for cylindrical shells. There are specific features associated with WSSG that tend to provide effective control of radiated sound power. The method has also been shown to be quite robust with respect to error sensor location. The effectiveness of WSSG control has been investigated through the use of radiation modes for cylindrical shells, which allows us to determine the radiated sound power both before and after control. Results using WSSG control will be reported, along with comparisons of the results obtained with some of the other possible control approaches reported previously.
A study on analysis of room equalizer using smart modules for analog high-quality audio
Authors: Seonggeon Bae , Jaepyung Kim , Esther Rhee
Published: May 2015

This study proposes room equalizer, which uses movable and variable modules and revises frequency response, and is also applicable to a variety of places. When equalizing frequency responses, commonly used electric graphic equalizers or parametric equalizers have the same effect as the sound signals such as audio passing through electrical elements like condenser or coil, and phase shift of audio signal occurs at this time. Accordingly, they secure frequency response by adjusting and equalizing the characteristics of sound-absorbing materials without any distortion of the original sound. Therefore, this study proposes a room equalizer that does not use these electrical characteristics, but uses non-electronic spatial matching with an excellent sound persistency rate to enable its application to various changes in space.
Effects of ground characteristics on wind-seismic coupling
Authors: Naderyan Vahid , Hickey Craig , Raspet Richard
Published: May 2015

In seismic surveys, wind noise at low frequency seriously degrades seismic data quality. In order to find a solution for this problem, the driving pressure perturbations on the ground surface associated with wind-induced ground motions were investigated in a previous work [Naderyan, Hickey, and Raspet, J. Acoust. Soc. Am. 136, 2139 (2014)]. Multiple triaxial 10 Hz geophones were deployed at different depths to study the induced ground velocity as a function of depth. The displacement amplitudes of the ground motions as a function of depth and frequency were predicted, where the ground was modeled as a homogeneous half-space elastic media. In the current work, the predictions are extended for inhomogeneous ground. The measurements are conducted at a different site with different characteristics. Since wind noise is dominant at lower frequencies, the triaxial 4.5 Hz geophones were used to investigate a lower frequency range. [This work was supported by USDA under award 58-6408-1-608.]
Acoustic meta-structures based on periodic acoustic black holes
Authors: Semperlotti Fabio , Zhu Hongfei
Published: May 2015

This paper presents a class of three-dimensional fully isotropic acoustic metamaterials that support the development of load-bearing thin-walled structural elements with engineered wave propagation characteristics, i.e. the meta-structures. This class of metamaterials is based on the concept of Acoustic Black Hole (ABH) that is an element able to bend and, eventually, trap acoustic waves. A periodic lattice of ABHs enables wave propagation characteristics comparable with resonant metamaterials but without the need and the fabrication complexity associated with the use of either multi-material or locally resonant inclusions. The dispersion characteristics show the existence of several interesting phenomena such as strong mode coupling, zero group velocity points on the fundamental modes, and Dirac points at the center of the Brillouin zone. Numerical simulations, conducted on a meta-structure made of a thin metal plate with an embedded slab of ABH material, show the existence of a variety of wave propagation effects (e.g., collimation and bi-refraction) in an extended operating range. Such an engineered material can pave the way to the design of thin-walled adaptive structures with fully passive wave management capabilities.
Respiratory-laryngeal coordination in airflow conservation and reduction of respiratory efforts of phonation
Authors: Zhang Zhaoyan
Published: May 2015

Although many previous studies investigated the effects of respiratory-laryngeal coordination during voice production, the importance of respiratory-laryngeal coordination to airflow conservation and reducing respiratory efforts of phonation has not been systematically investigated. In this study, a computational model of the pressure-volume-flow relationship in the respiratory system is developed and coupled to a three-dimensional continuum model of phonation. Simulations at different conditions of the lung initiation volume and laryngeal resistance show that small laryngeal resistance, as observed in vocal fold paralysis or soft voice conditions, leads to large airflow rate out of the lungs and thus below-normal duration of speech between breaths. Although the speech duration can be increased by an increase in either the lung initiation volume or laryngeal resistance, increased laryngeal resistance also reduces the respiratory effort required to maintain a target subglottal pressure. The demand for laryngeal resistance increase in order to maintain a normal breath group duration increases when phonating at a lower lung initiation volume or when a higher subglottal pressure is desired. Finally, the simulations show that tightening vocal fold approximation is more effective than vocal fold stiffening in increasing speech duration between breaths and reducing respiratory effort of phonation. [Work supported by NIH.]
Influences of word frequency and response delay on imitation of visual speech
Authors: Dias James W. , Rosenblum Lawrence D.
Published: May 2015

Human perceivers unconsciously imitate the subtle articulatory characteristics of perceived speech (phonetic convergence) during live conversation [e.g., Pardo, 2006] and when shadowing (saying aloud) pre-recorded speech [e.g., Goldinger, 1998]. Perceivers converge along acoustical speech dimensions when shadowing auditory (heard) and visual (lipread) speech [Miller, Sanchez, & Rosenblum, 2010], suggesting the information to which perceivers converge may be similar across sensory modalities. It is known that phonetic convergence to auditory speech is reduced when shadowing high-frequency words and when shadowing responses are delayed. These findings suggest that stored lexical representations and working memory processing time may modulate speech imitation [Goldinger, 1998]. The question arises of whether phonetic convergence to shadowed visual speech would demonstrate the same effects of word frequency and shadowing response delay. Phonetic convergence was reduced when shadowing lip-read high-frequency words, suggesting lexical information may be similarly accessed by auditory and visual information, consistent with the effects of word frequency on auditory and visual speech comprehension [e.g., Auer, 2002, 2009]. However, where shadowing delay reduced phonetic convergence to auditory speech, it increased phonetic convergence to visual speech. The results are discussed with respect to possible differences in processing of auditory and visual speech information across response delays.
Auditory feedback perturbation of vowel production: A comparative study of congenitally blind speakers and sighted speakers
Authors: Trudeau-Fisette Pamela , Bellavance-Courtemanche Marie , Granger Thomas , Rapin Lucile , Turgeon Christine , Ménard Lucie
Published: May 2015

Studies with congenitally blind speakers show that visual deprivation yields increased auditory discrimination abilities as well as reduced amplitude of labial movements involved in vowel production, compared with sighted speakers. To further investigate the importance of auditory and visual feedback in speech, a study of auditory perturbation of rounded vowels was conducted in congenitally blind and sighted French speakers. Acoustic and articulatory (electromagnetic articulography) recordings from ten congenitally blind speakers and ten sighted speakers were obtained during the production of the French rounded vowel /ø/. All participants were first asked to produce the vowel repeatedly in a normal condition, i.e., with regular auditory feedback. In the perturbed condition, participants received, in real-time through headsets, an altered version of their speech, in which F2 was gradually increased up to 500 Hz. To compensate for this perturbation, speakers had to enhance lip protrusion and/or tongue retraction. These adaptive maneuvers should have been concurrent with auditory perception abilities. Preliminary results show that congenitally blind speakers gave greater weight to auditory perception than their sighted peers, while compensating differently for the perturbations. These findings support the hypothesis that vision plays a significant role in the implementation of phonological targets.
Vocal imitations of basic auditory features
Authors: Lemaitre Guillaume , Jabbari Ali , Houix Olivier , Misdariis Nicolas , Susini Patrick
Published: May 2015

We recently showed that vocal imitations are effective descriptions of a variety of sounds (Lemaitre and Rocchesso, 2014). The current study investigated the mechanisms of effective vocal imitations by studying if speakers could accurately reproduce basic auditory features. It focused on four features: pitch, tempo (basic musical features), sharpness, and onset (basic dimensions of timbre). It used two sets of 16 referent sounds (modulated narrow-band noises and pure tones), each crossing two of the four features. Dissimilarity rating experiments and multidimensional scaling analyses confirmed that listeners could easily discriminate the 16 sounds based the four features. Two expert and two lay participants recorded vocal imitations of the 32 sounds. Individual analyses highlighted that participants could reproduce accurately pitch and tempo of the referent sounds (experts being more accurate). There were larger differences of strategy for sharpness and onset. Participants matched the sharpness of the referent sounds either to the frequency of one particular formant or to the overall spectral balance of their voice. Onsets were ignored or imitated with crescendos. Overall, these results show that speakers may not imitate accurately absolute dimensions of timbre, hence suggesting that other features (such as dynamic patterns) may be more effective for sound recognition.
Articulation of vowel height in Taiwanese Vowels: An EMA study
Authors: Chang Yuehchin , Chen Yi-cheng , Hsieh Feng-fan
Published: May 2015

Whalen et al.’s (2010) ultrasound study has suggested that constriction degree “may be the best descriptor for height” in American English front vowels {i, ɪ, e, ɛ}. The present study took a further step, investigating the case of height and backness distinction in Taiwanese front and back vowels. Stimuli consisted in /CV/ sequences with V corresponding to one of the six vowels {i, e, a, ɔ, ɣ, u} (Southern variety). Five adult speakers were asked to repeat each sequence six times in random order. The articulatory data were collected using the Carstens AG500 EMA system. Our results show that vowel height and backness in Taiwanese vowels can be reliably differentiated as follows: (1) for front and central vowels, height is primarily distinguished by Tongue Body Constriction Degree (TBCD) (i>e>a) (less robustly by Tongue Tip Constriction Degree), whereas height distinction of back vowels is made in Tongue Dorsum Constriction Degree (TDCD) (u>ɣ>ɔ), (2) backness can be distinguished by Tongue Tip and Tongue Body Constriction Location. Therefore, Whalen et al.’s (2010) claim can be extended to back vowels as well (at least in Taiwanese). Furthermore, our results are compatible with Ladefoged’s (2001) “holistic” view of vowel height as long as his “highest point of the tongue” can be “locally” interpreted: TBCD for height of front and central vowels and TDCD for back vowels. In sum, the present study suggests that distinction in vowel height be relativized to different gestural constriction degree.
A task dynamic approach to the coda-voicing effect on vowel duration
Authors: Hagiwara Robert
Published: May 2015

The coda-voicing effect on vowel duration (CVE), in which vowels are longer with voiced codas and shorter with voiceless, is well attested. However, the precise mechanism of this relationship is not well studied. Task-dynamic models such as articulatory phonology (e.g., Browman & Goldstein, 1986) offer two ways to affect the duration of a vowel in a CVC syllable: the relative phasing of the onset, vowel, and coda gestures (when they start relative to one another), and the relative stiffness of an individual gesture (roughly how quickly it is executed). Onosson (2010) argued that for /ai/, the principal mechanism of Canadian Raising (CR) was vowel shortening via increased overlap of the onset gesture and the vowel, rather than vowel-coda phasing or stiffening the vowel gesture. This study investigates whether this explanation holds generally for 15 vowels in Canadian English, using controlled wordlist-style data (originally from Hagiwara, 2006). Preliminary investigation suggests that onset-phasing may hold for the diphthongs, but does not adequately characterize CVE across the vowels. The observable mechanism(s) of CVE will be discussed, as well as implications for CVE and related effects (e.g., CR) across dialects/languages generally.
A novel method to measure the resonances of the vocal tract
Authors: Delvaux Bertrand , Howard David
Published: May 2015

In speech/singing, knowledge of the frequencies of the resonances of the vocal tract gives access to the vowel type (lower resonances) and the voice timbre (higher resonances). It is therefore crucial to be able to measure accurately these resonant frequencies directly. Several approaches have been developed such as glottal excitation, excitation at the lips, or medical imaging. More accurate measurements of the vocal tract resonances have emerged from physical modeling in recent years but a simple-to-use in vivo measurement tool would be much more valuable to give feedback to the singer/actor and their teacher(s), as well as voice therapists, language teachers, speech scientists, phoneticians, and linguists. In this article, we suggest a novel method using a sinesweep to measure the resonant frequencies of the vocal tract simultaneously with the voice spectrum.
Leonid Brekhovskikh and his lasting impact on underwater acoustics
Authors: Godin Oleg A.
Published: May 2015

This paper will discuss Brekhovskikh’s groundbreaking contributions into physical oceanography and the theory of wave propagation, scattering, and diffraction from the prospective offered by current developments in underwater acoustics. In hindsight, three major contributions stand out in Brekhovskikh’s legacy, which highlight different facets of his personality and his talents. For many decades, ocean acoustics was Leonid’s passion. He developed and promoted an approach to underwater acoustics, which embraced the ocean’s complexity and centered on devising techniques to reliably characterize the uncertain environment by acoustic means. The approach led to creation of an informal but rather productive and enduring “Brekhovskikh’s school.” Leonid worked only briefly on wave scattering by rough surfaces. However, his findings, which became known as the tangent plane approximation, revolutionized the field. Universally recognized are Brekhovskikh’s systematic theoretical studies of underwater sound propagation, which are summarized in his celebrated book Waves in Layered Media. The theory includes spectral representations of wave fields, normal mode theory for open waveguides, and a clear treatment of diffraction phenomena attendant to caustics, lateral waves, and reflection of wave beams and pulses. The book charted the ways forward which have been and are followed by numerous researchers around the globe.
The University of California Division of War Research and the Marine Physical Laboratory
Authors: Kuperman W A.
Published: May 2015

In 1941, motivated by the large-scale destruction of ships by submarines in World War II, three university-operated laboratories were established: Columbia University Division of War Research, Harvard Underwater Sound Laboratory, and The University of California Division of War Research (UCDWR). UCDWR was led initially by Vern Knudsen of the University of California, Los Angeles, with senior staff recruited from academic institutions across the country. After the war, UCDWR was dissolved with the The Navy Electronics Laboratory absorbing most of the UCDWR employees. Further, by agreement between the Navy and the Regents of the University of California, the Marine Physical Laboratory (MPL) was formed with an initial scientific staff of five people from UCDWR with Carl Eckart as its Director. We review this transition period and MPL’s subsequent trajectory within the University of California system to its ultimate venue in the Scripps Institution of Oceanography.
Contributions to the development of underwater acoustics at the Harvard Underwater Sound Laboratory
Authors: Pestorius Frederick M. , Blackstock David T.
Published: May 2015

The Harvard Underwater Sound Laboratory (HUSL) began in June 1941, six months before Pearl Harbor, and closed on January 31, 1946. HUSL was directed throughout its existence by (then) Assoc. Prof. Frederick V. Hunt, who incidentally coined the acronym sonar. This paper traces several contributions HUSL made to undersea warfare through exploitation of underwater acoustics. Especially significant were developments by HUSL in sonar and underwater ordnance (torpedoes). Both developments were supported by numerous subprojects on a wide range of applications such as reverberation suppression, Doppler enhancement, and torpedo transducer design. Particular attention is paid to work on air-dropped and submarine-launched acoustic homing torpedoes. HUSL’s far-reaching influence continues to be evident in today’s sonar and torpedo systems. Closure of HUSL spawned Penn State’s Ordnance Research Laboratory (now Applied Research Laboratory) and enriched sonar development at the US Navy Underwater Sound Laboratory, New London. Moreover, HUSL personnel returning to the University of Texas soon founded the Defense Research Laboratory (now Applied Research Laboratories) at Texas. We pay particular homage to living HUSL alumnus A. Wilson Nolle, who, along with our recently departed colleague, Reuben Wallace, and 12 other deceased alumni, had come to HUSL from the University of Texas.
Effect of adhesives in structure-borne and impact sound measurements
Authors: Paley Sharon , Hunt Bradlay
Published: May 2015

Based on a preliminary finding in “Contribution of Floor Treatment Characteristics to Noise Levels in Health Care Facilities Part 2,” we investigate the effect that various adhesives may have in surface generated sound and impact sound transmission levels. The aforementioned study demonstrated that lower source room sound levels were generated with an acrylic adhesive assembly when compared to sound levels generated with a urethane adhesive assembly. These findings led to two follow-up questions: (1) What effect does adhesive have in IIC ratings? and (2) Is there a clear inverse relationship between sound levels within a source and receiving room, and how much does the adhesive affect this relationship? Results from tests conducted in a lab environment with multiple floor finishes and multiple assemblies will be discussed.
The use of articulation theory and the speech intelligibility index in the design of clinical speech perception tests
Authors: Brungart Douglas , Grant Kenneth W.
Published: May 2015

For more than 50 years, the Articulation Index (AI) and its successor the Speech Intelligibility Index (SII) have been recognized as essential tools for predicting the impact that reduced bandwidth, background noise, and differences in speech materials will have on the speech perception performance of normal hearing listeners. However, one caveat about both AI and SII is that neither is considered to be valid for predicting the performance for hearing impaired listeners. Nevertheless, the insights provided by the AI and SII can be invaluable in the design and analysis of clinical speech tests designed to evaluate the relative performance of hearing impaired listeners. In this talk, we discuss role that the SII and AI played in the development of a speech-in-noise test based on the Modified Rhyme Test that is intended for use in the evaluation of Auditory Fitness-for-Duty in military personnel. In this case, the information drawn from the SII was essential both in the selection of appropriate speech materials and SNR values and in finding ways to analyze the results of normal and hearing impaired listeners. The results of the study provide evidence for a “pure” SNR loss in hearing impaired listeners that occurs even when all components of the speech signal are audible. [The views expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Department of Defense or U.S. Government.]
Predicting speech intelligibility for hearing-impaired listeners
Authors: Kates James M.
Published: May 2015

Karl Kryter was instrumental in developing the Articulation Index (AI) standard and demonstrating its effectiveness. The AI, and its successor, the Speech Intelligibility Index (SII), predict intelligibility based on the audibility of speech sounds. The concept of audibility is also relevant to hearing loss and the effectiveness of hearing aids, and extensions of the AI have been developed to predict hearing-aid benefit. However, audibility alone cannot explain the impact of nonlinear distortion and nonlinear hearing-aid processing on intelligibility. This talk will present a review of the how the AI and SII have been used for hearing aids, extensions to the SII targeted at predicting hearing-aid effectiveness, and more recent work that focuses on envelope fidelity rather than audibility in predicting intelligibility for hearing-aid users.
The angle of intromission in muddy sediments: Measurements and inferences
Authors: Holland Charles W. , Dettmer Jan , Dosso Stan E.
Published: May 2015

Fine-grained sediments, e.g., mud, often exhibit sound speeds less than that of the interstitial fluid. This leads to an angle of intromission (AI), or Brewster angle, at which there is nearly complete transmission of acoustic energy from the water column into the sediment. It is generally difficult to observe this angle directly inasmuch as (1) fine-grained sediments typically have a very low attenuation and (2) underlying granular sediments have a higher sound speed and thus the total seabed reflected field tends to be dominated by the underlying more highly reflective sediments. In some cases, the AI can be directly observed by time-gating the reflected field such that only the fine-grained sediments are insonified. Nominally, the AI is independent of frequency. However, reflection measurements from hundreds of hertz to several kilohertz show a frequency dependence. This dependence is due to sound speed and density gradients (which thus can be estimated from the reflection data). Reflection measurements and core data indicate that geoacoustic gradients depend upon location on the continental shelf. In the Italian littoral, density gradients are always observed to be positive and decrease seaward. Curiously, sound speed gradients can be positive or negative and have a less obvious correlation with position. [Research supported by ONR Ocean Acoustics.]
Broadband ultrasound scanning and frequency sweep measurement for trabecular bone with novel wideband single crystal transducer
Authors: Jiao Jian , Li Xiaofei , Lin Liangjun , Sahul Raffi , Nesvijski Ed , Qin Yi-Xian
Published: May 2015

Quantitative ultrasound has been developed as a radiation-free technique to evaluate both bone density and strength. The ultrasound parameters, such as velocity (UV), attenuation (ATT), and broadband attenuation (nBUA), have been widely used as indicators for bone health status. In our study, a novel spiral-wrapped wideband ultrasound transducer is developed by TRS. Bovine trabecular bone samples (15 mm thickness) were prepared for frequency scanning. In each group, TRS transducer was used to emit the frequency from 0.5 to 7 MHz to propagate through samples; and pulses were received by the hydrophone. Frequency sweep response mostly correlated to bone density at frequency under 3 MHz, and barely showed any correlation with bone density at a frequency above 3 MHz, as higher frequency ultrasound energy attenuated significantly in trabecular bone. With controlled bone density reduction by 34.71%, UV decreased from 2575.03±34.38 m/s to 1717.15±48.19 m/s, ATT decreased from 3.66±0.71dB to 2.21±0.76 dB, and nBUA decreased from 2.09±0.96 dB/MHz/cm to 1.21±0.47 dB/MHz/cm. Generally, bone density decrease resulted in UV, ATT, and nBUA decreases, but were sensitive to the change of the wideband frequency from 0.5 MHz to 0.8 MHz. This new wideband transducer offers more information than the conventional ultrasound transducer, and can thus be used as a modality to evaluate bone health status.
Ultrasonic wave velocities in radial direction of bovine cortical bone
Authors: Nishimura Yuma , Kawasaki Satoshi , Matsukawa Mami
Published: May 2015

The ultrasonic axial transmission (AT) techniques have been proposed to evaluate the cortical bone of arms and legs. For the mode analysis of propagating waves, the information of anisotropy and heterogeneity of the cortical bone is important. Yamato has pointed that longitudinal wave velocity in the axial direction of bovine cortical bone changes due to the measurement positions and microstructures. In this study, we have investigated longitudinal wave velocities in radial direction of cortical bone. The cuboid samples were obtained from the cortical bone of bovine femur. During ultrasonic pulse immersion experiments, a sinusoidal ultrasonic wave in the range from 3 to 10 MHz was transmitted from a PVDF transducer, which passed through the sample in the radial direction. By reducing the sample thickness gradually, wave velocities were measured. The average velocities in radial direction of samples were around 3450 m/s and depended on the positions of the samples in the femur. They variation of the velocities due to the thickness was about 7 %. These data give us the information of heterogeneity of cortical bone in radial direction which should be considered in the AT techniques. [1] Y. Yamato, et al., Jpn. J. Appl. Phys., 47, 4096–4100 (2008).
Development of an acoustics outreach program for the deaf
Authors: Vongsawad Cameron T. , Berardi Mark L. , Gee Kent L. , Neilsen Tracianne B. , Lawler M J.
Published: May 2015

The Hear and Seemethodology (Groppe, 2011) has often been used as ameans of enhancing pedagogy by focusing on the two strongest learningsenses, but this naturally does not apply to deaf or hard of hearing students. Because deaf students’ prior nonaural experiences with sound will vary significantly from those of students with typical hearing, different methods must be used to build understanding. However, the sensory-focused pedagogical principle can be applied in a different way for the Deaf by utilizing the senses of touch and sight, called here the “See and Feel” method. This presentation will provide several examples of how acoustics demonstrations have been adapted to create an outreach program for a group of junior high students from a school for the Deaf and discuss challenges encountered.
Using acoustics and vibrations to teach experimental concepts and technical communications
Authors: Ryan Teresa J. , Turo Diego , Vignola Joseph F. , Judge John A.
Published: May 2015

This work describes an experience-based conceptual course in vibrations and acoustics. This one-hour course is designed with the goal of framing general experimental issues, interpreting experimental results, and developing technical communication skills in engineering by way of acoustics and vibrations experiments. Like other laboratory experiences, the goal is to support the skill of making the connection between experimental results and the physical system. Unlike other courses offered at East Carolina University and The Catholic University of America, the primary learning objectives are those connections and technical communication skills rather than the acoustics and vibrations content. Experimental issues explored include error, repeatability, linearity, uncertainty, and general experimental design. This particular set of acoustics and vibrations experiments is well suited to this purpose because they do not require extensive laboratory infrastructure, they are inherently safe, and they use commonplace tools. These tools include a speaker, microphone, and accelerometer, which the students already have as part of their laptop and/or smartphone. These tools, along with a copy of MATLAB, provide the opportunity to perform a wide array of experiments, which can illustrate sophisticated concepts using these basic, familiar items.
A simply constructed condenser microphone as a teaching aid
Authors: Ali Randall A. , Thompson Stephen C.
Published: May 2015

To gain a deeper appreciation and a better understanding of the operation of condenser microphones, it is instructive to have a tangible device, which can undergo a fair amount of experimentation. Low cost condenser microphones used in laptops, mobile phones, and other similar devices can be purchased, but not necessarily deconstructed to serve as an effective learning tool. On the other hand, condenser microphones used in recording studios can be taken apart, but can become quite expensive and making any elaborate modifications to the design may prove challenging. As an alternative, we present a functional and cost-effective condenser microphone that can be simply constructed from readily available materials. The device enables students to make changes to the diaphragm material, back plate, electrostatic gap spacing, and the electronic circuit for connection to a lower impedance device. A SPICE model of the condenser microphone is also presented, which was used to guide the design and can provide further insight for the student.
Environmental noise assessment by means of psychoacoustics and its relation to in-situ annoyance judgments of urban noise
Authors: Fiebig André
Published: May 2015

It is obvious that environmental noise assessment only based on the consideration of LAeq values cannot determine the character of environmental noise and its specific reactions and responses evoked. Noise is not only perceived in terms of lower or higher (averaged) sound pressure levels; noise leads to different auditory sensations and perceptions, which are influenced by context. The introduction of psychoacoustics allows for describing the character of noise more in detail and for predicting human responses to noise more reliably. In order to investigate the link between psychoacoustic parameters and annoyance judgments, soundwalk data including in-situ noise judgments from several measurement campaigns were analyzed. It turned out that by taking into account psychoacoustic parameters more variance in noise annoyance data is explained. Based on the analysis and results of the soundwalk data, the questions are addressed about how long must be measured to encompass all relevant acoustical situations and how the measurement of short-term reactions are related to long-term noise effects. Based on the presented case studies, it is intended to gain insight into the benefits and limitations of psychoacoustics with respect to environmental noise assessment.
Status of psychoacoustics in noise analysis
Authors: Genuit Klaus
Published: May 2015

Psychoacoustics provides knowledge about the relationship between acoustical stimuli and provoked hearing sensations for specific “one-dimensional” sensations like loudness, sharpness, roughness, or fluctuation strength. Psychoacoustic measures are often applied in the context of sound quality investigations. Sound quality has to be understood as a multi-dimensional phenomenon related to the perception of sensory pleasantness (sound character) and suitability of sound in context. It is widely accepted that psychoacoustic measures offer better agreement with auditory sensation than conventional A-weighted sound pressure levels and spectra do. In particular, the psychoacoustic parameter loudness gains extensively in significance, because it shows a higher correspondence with the sensation of volume (loudness) than any sound level indicator. Thus, loudness represents a dominant feature for sound quality evaluation and is frequently applied in numerous applications. In the field of environmental noise the main focus lies on the exact measurement and description of the acoustical situation in a pure physical sense, whereas the community noise perspective tries to bridge acoustical exposure and the human assessment of noise in sense of annoyance level. In contrast to it, the disciplines of psychoacoustics, sound quality, and soundscape put more emphasis on the perceiving human being. This paper gives an overview about the status of psychoacoustics with respect to application in noise.
Ultrasound propagation in concentrated random dispersions of spherical particles: Thermal- and shear-mediated contributions to multiple scattering
Authors: Pinfield Valerie , Forrester D Michael
Published: May 2015

Ultrasonic techniques offer advantages for process monitoring for dispersions of colloidal or nano particles; such materials occur in a wide variety of process industries. However, the application of ultrasonic techniques has been limited by the inaccuracy of ultrasonic propagation models used to interpret the measurements (typically attenuation spectra). Multiple scattering models, such as the Lloyd and Berry model [Proc. Phys. Soc. London 91, 678 (1967)], have been used with great success in relatively dilute colloidal dispersions, but fail for higher concentrations, smaller particles, and low frequencies, primarily due to the neglect of thermal- and shear-mediated effects. We present a modified multiple scattering model that includes these thermal- and shear-wave contributions and explore their significance. The model develops work by Luppé, Conoir and Norris [J. Acoust. Soc. Am. 2012 (131) 1113) for compressional, thermal and shear wave propagation. We identify the dominant scattering contributions for emulsions [Pinfield, J. Acoust. Soc. Am. 136, 3008 (2014)] and suspensions and develop analytical forms for them. Numerical calculations demonstrate the contribution of the additional multiple scattering effects to the compressional wave speed and attenuation through the emulsion or suspension. The calculations are compared with previously published experimental data.
Direct computation of acoustic scattering and difference frequency generation
Authors: Nguon Chrisna , Mudasiru Ololade , Mogulla Sameera , Chandra Kavitha , Thompson Charles
Published: May 2015

A simulation of the scattered field at the difference-frequency resulting from the nonlinear interaction of two beams at differing frequencies incident on a fluid scatterer is performed. The total wavefield response is modeled using a finite-difference time-domain approximation and a perfectly matched layer to estimate the spatial scattering features of the medium. A pulsed ultrasonic transducer beam is modeled and its interaction with a fluid scatterer with spatially varying compressibility contrast is visualized. The second-order pressure field is determined as a response to the difference-frequency source field constructed from the first order-response of the scatterer to the two incident beams as well as a spatial distribution of the nonlinear parameter. The performance and accuracy of the numerical simulation is examined.
The weak sensitivity of acoustic resonance frequencies to temperature gradients
Authors: Gillis Keith A. , Moldover Michael R. , Mehl James B. , Schmidt James W.
Published: May 2015

We determined the mass of argon gas contained within an un-thermostatted, commercially-manufactured 300 L pressure vessel (tank) with an uncertainty of 0.16 % at 0.6 MPa by combining measurements of the argon pressure, the frequencies of microwave and acoustic resonances within the tank, and an equation of state for argon. After correction for the thermoacoustic boundary layer and for the tank’s center-of-mass motion, the measured acoustic resonance frequencies fac determined the average speed of sound, and therefore the average temperature, of the argon in the tank. We show that, consistent with first-order perturbation theory, fac for the 3 lowest-frequency longitudinal gas modes gave the correct average temperature even when we imposed a 13 K temperature difference ΔT across the tank’s diameter. However for the nearly degenerate doublet modes, we observed a linear dependence on ΔT for fac, which the theory does not predict. Using the thermal expansion deduced from the microwave measurements, we show that the linear dependence on ΔT was consistent with anisotropic changes in the tank’s shape in response to the applied temperature gradient. We will discuss the predictions from perturbation theory of the changes in fac due to temperature gradients in cylindrical and spherical cavities. From these results, we argue that resonance frequencies can be used to “weigh” a compressed gas in much larger tanks in un-thermostatted environments and at high pressures.
Investigation of acoustic scattering using fast-multipole Padé approximant methods
Authors: Zhou Hui , Noursadeghi Elaheh , Sadeqi Aydin , Chandra Kavitha , Thompson Charles
Published: May 2015

The scattering of acoustic waves from three-dimensional compressible fluid scatterers is considered. Particular attention is paid to cases where the scatterers have moderate magnitude in compressibility contrast and nondimensional wave number. The scattered field is cast in terms of asymptotic series valid in the limit of small compressibility contrast. It has been shown that pointwise application Padé Approximants in the scattering volume may be used to expand the range of validity of the result. However pointwise divergence in the scattering volume can result as the magnitude of the compressibility contrasted is increased. In this work the utility of low-frequency Fast-multipole method in evaluating the Born series coefficients is examined.
Neuroplasticity with cochlear implants: Underlying neuronal mechanisms
Authors: Kral Andrej
Published: May 2015

Chronic cochlear implant (CI) stimulation in congenitally deaf cats (CDCs) leads to cortical maturation matching imaging data from humans (Kral and Sharma, 2012, TINS). One possible measure of auditory plasticity is the reorganization of aural preference following monaural CIs (Kral et al., 2013, Brain), showing a sensitive period of <4.2 months in cats. A substantial reduction of binaural information following developmental unilateral hearing was found in cortical neurons (Kral et al., 2015, Audiol Neurootol). Consequently, auditory maturation requires experience. Additional to reduced synaptic plasticity, loss of acuity in feature representation, deficits in integrative function of the cortical column and deficits in corticocortical, particularly top-down, interactions, close the sensitive periods (Kral 2013, Neuroscience). Cross-modal plasticity recruits auditory resources for non-auditory tasks. Despite of cross-modal reorganization in some auditory areas the extend of the underlying reorganization of corticortical connections (Barone et al., 2013, PLoS One) indicates that this only moderately limits auditory processing capacity. Electrophysiological recordings in the dorsal auditory cortex of CDCs demonstrate that the cross-modally reorganized secondary auditory areas maintain a predominance of dormant auditory inputs additional to moderate cross-modal reorganization. [Supported by Deutsche Forschungsgemeinschaft (Cluster of Excellence Hearing4all).]