bluuebunny/crossref_metadata_2025 huggingface dataset:
Geoacoustic modeling based on sediment particle analysis.
Authors: Ivakin Anatoliy N.
Published: July 2011

Geological underwater processes are affected by physical properties of sediment particles, their size, shape, and spatial variability. In geological modeling, these parameters are normally provided by analysis of sediment cores and documented in certain geologically relevant terms. What is the set of parameters most relevant from acoustics standpoint, or in “acoustically relevant” terms, is an open question. It is addressed using an acoustic scattering model directly based on sediment particle analysis, geo-acoustic model of bottom interaction taking into account the sediment discrete heterogeneity. The particle size distribution in this model is comprised of central and coarse parts. The central part describes the sediment matrix and its large scale variability, or continuous heterogeneity, critical for modeling of acoustic propagation in the sediment. To account for discrete component of heterogeneity, the coarse part of size/shape distributions is attributed to “inclusions” in the sediment matrix and provides direct inputs for evaluation of volume scattering in the sediment. An example of such analysis and modeling based on the SAX04 geo-acoustic data set is presented and used for calculating the frequency-angular dependences of bottom backscattering strength. Comparisons with acoustic backscatter data measured at this site and possibilities for geoacoustic inversions are discussed.
Combination of wave-based and geometrical-acoustics simulation to study acoustic properties of recording rooms.
Authors: Ahnert Wolfgang , Feistel Stefan , Schmalle Holger
Published: July 2011

In small recording rooms the acoustic behavior is determined by geometric as well as wave acoustic phenomena. After introducing basic acoustic parameters of these rooms some tools to acquire the necessary acoustic parameters are presented. For this study, a known recording room is used to establish a geometrical-acoustics model using EASE and to derive its geometrical acoustic properties, primarily the transfer function for a certain listener position valid for different monitor speakers. A new tool allows now to derive the modal distribution for the selected speaker-listener positions. Based on the obtained results a transfer function for the low frequency part is derived. Combing the transfer functions of both the geometrical acoustic and the wave acoustic part, the Fourier transform results in broadband impulse responses, which will be compared with the experimentally measured ones.
Effects of excessive noise and reverberation on listening and learning in a simulated classroom.
Authors: Valente Daniel L. , Lewis Dawna , Heinrichs Elizabeth , Spalding Jody , Franco John , Plevinsky Hallie
Published: July 2011

Elementary students often learn in dynamic discussions during typical classroom lessons. Many classrooms, though, have poor signal-to-noise ratios and long reverberation times. The presence of excessive noise and reverberation may increase a student’s listening effort and result in reduced performance during classroom learning. A simulated classroom environment was created which allowed for varying degrees of room reverberation and background noise. In this experiment, groups of elementary-aged students were seated in the center of the simulated classroom environment and were presented a story read by either five talkers positioned around the student or a single talker in front of the student (reproduced by LCD monitors and loudspeakers). A post-test was used to assess listener comprehension. Comprehension scores are compared to a group of adult subjects as well as a sentence-recognition task in the same condition. Significant differences were seen in comprehension scores as a function of age and condition, both increasing background noise and reverberation degraded performance in comprehension tasks compared to little or no differences in measures of sentence-recognition. Finally, comprehension scores are correlated to measures of the speech transmission index in each of the simulated classroom environments.
Acoustical design of heathcare facilities for leadership in energy and environmental design green building certification: Odd harmonic filter for mechanical system noise control.
Authors: Harrison Seth M.
Published: July 2011

To achieve the leadership in energy and environmental design (LEED) indoor environmental quality credit 2: acoustic environment, healthcare facilities must meet stringent sound and vibration criteria. Mechanical system noise presents one of the largest obstacles to meeting the room noise design requirements. Code requirements intended to promote indoor air quality, and infection control limits the use of typical absorptive materials such as fiberglass duct liner, packed duct silencers, and other porous absorbers. Energy code requirements force mechanical system designers to locate large noise sources such as air handlers, fan-powered terminal air boxes, and exhaust fans close to the spaces they serve, adding to background noise levels. One innovative, practical solution to tonal mechanical system noise is an odd harmonic filter. Acoustical performance of odd harmonic filters and strategies to achieve the room noise criteria for the LEED acoustic environment credit will be discussed.
Using a sustainable material to produce a sound absorbing panel.
Authors: Kanter Shane J.
Published: July 2011

A recent university research project involved the creation of an environmentally friendly sound absorbing panel using bamboo. The goal of this research was to produce a panel with a sustainable material that could be used in similar applications where wood fiber sound absorbing panels would be employed. The test bamboo panel has been made from bamboo rings approximately 1.6 mm thick cut from bamboo stalks with diameters varying from approximately 6 to 50 mm. The bamboo rings were randomly formed into a panel about 25 mm thick using an environmentally friendly adhesive with very low viscosity. Panel sound absorption has been determined using the reverberation room method, an in situ method, and an impedance tube method. [This research was partially funded by an Acoustical Society Robert W. Young award.]
Assessment of cumulative effects of underwater sound: A collaborative approach.
Authors: Racca Roberto
Published: July 2011

A multidisciplinary team of scientists working under a research agreement between the University of California, Santa Barbara and BP America Production Company has undertaken a 2-year project, currently ongoing, to develop one or more standardized and practical methods for assessing cumulative effects of anthropogenic underwater sound on marine mammals. The work of the team is based on access to existing scientific information without substantial involvement of additional primary research although topics for future research may be part of the eventual recommendations. While the final goal of the project is to conceptualize and specify widely applicable methodologies, case studies are being used to help formulate and test the feasibility of assessment frameworks. The primary case study involves the significant hydrocarbon related industrial activity that took place in the Beaufort Sea (Alaska and Canada) during late summer and autumn 2008 and its potential cumulative effect on the population of bowhead whales (Balaena mysticetus) that dwell and transit through the region in their annual migration cycle. Methods that include advanced numerical modeling of sound propagation, individual-specific dose exposure calculation, and sensitivity analysis of the range of potential responses as a function of various influence factors are applied in the execution of these studies.
Application of passive acoustic reflectors to mitigate toothed whale depredation on longlines.
Authors: Deveau David M. , McPherson Geoff
Published: July 2011

Indo-Pacific longline fisheries have noted for decades that entangled fish, particularly those with swallowed hooks or with elements of metal in the entangling gear, were invariably spared from depredation attacks. To enhance the capability of fishery objects to either highlight their presence as foreign or to interfere with the clarity of returning echoes, a range of sonar reflective material logistically acceptable to the fishing industry was modeled. Small alloy spheres were shown to have target strengths equivalent to that expected of the TS of an entire tuna from a rear approach, the normal approach on hooked swimming tuna during depredation events. The performance of reflectors is governed by the ratio of the dimensions of the object to the wavelength of the toothed whale broadband echo click. Known changes in hearing and sonar focus with increasing toothed whale age must be factored into a fishery based approach. Spheres developed for the Coral Sea were trialed by Japan Fisheries Research Agency. Logistic issues were a problem while other fisheries have expanded their commercial utilisation. Spheres with greater logistic simplicity and higher target strengths have been identified for further testing and if commercially constructed could be readily incorporated into fishing operations.
The acoustical components of the Arctic Ocean observing system.
Authors: Sagen Hanne , Sandven Stein
Published: July 2011

The Arctic Ocean is severely under-sampled due to lack of regular observing systems. A future sustainable Arctic Ocean observing system will need to combine data from several underwater sensors with satellite data and models. During the international polar year (IPY) 2007–2009, new technologies for ocean observations such as acoustic thermometry/tomography, ice tethered buoys, floats, and gliders operating under the ice were developed and successfully tested. Based on experience from IPY, a future Arctic Ocean observing system should include a multi purpose acoustic network of source- and receiver moorings with capability to (1) measure the acoustic travel times to derive heat content and mean circulation on a regional or basin scale in minutes or hours, (2) provide an underwater GPS system for navigation and timing for under-ice Lagrangian systems, and (3) provide information about ice dynamics, earthquakes, and marine mammals through passive listening. Near-real time data from Arctic underwater systems can be improved by use of acoustic communication between underwater platforms and ice-tethered platforms with satellite communication. In the future cabled systems can enhance the capability to obtain near-real time data. The Svalbard Integrated Observing System will develop plans for an ocean observing system in the European sector of the Arctic.
Acoustic thermometry of ocean climate and the global ocean observing system.
Authors: Dushaw Brian D.
Published: July 2011

The uniqueness and sustainability of acoustic measurements of basin-scale temperature were demonstrated by the the Acoustic Thermometry of Ocean Climate and North Pacific Acoustic Laboratory programs in the North Pacific over the decade 1996–2006. Tomography has a role to play in the global observing system as a measurement type that complements altimetry and profiling floats. Tomography is a subsurface measurement of temperature; salinity contributes negligibly. Acoustic travel times are inherently precise integral measurements of temperature; mesoscale variability is supressed. Tomographic measurements offer one of the few ways to sample the abyssal ocean. The North Atlantic and Arctic have been highlighted by international conferences as regions that would be suitable for implementing tomographic arrays. Ocean basins can be measured by tomography using a few acoustic sources and receivers, employing platforms of opportunity such as existing or planned components of the ocean observing system. Extensive acoustic sampling can be achieved by sharing resources, while minimizing long-term operation and maintenance costs. Because of the integral nature of the data, tomography is best employed in conjunction with numerical ocean models and data assimilation. [Dushaw et al., “a global ocean acoustic observing network,” OceanObs’09: Sustained Ocean Observations and Information for Society, ESA Publication No. WPP-306].
High intensity focused ultrasound characterization of deep bleeder acoustic coagulation cuffs.
Authors: Sekins K. Michael
Published: July 2011

Research prototype therapeutic ultrasound “cuffs” have been recently constructed to demonstrate the feasibility of cauterizing bleeding (acoustic hemostasis) of deep limb wounds, such as those from military combat or other penetrating trauma. The deep bleeder acoustic coagulation (DBAC) cuffs required a variety of HIFU power and acoustic beam assessments to assure safety and efficacy. The cuff, capable of > 1000 W acoustic power, comprised multiple two-dimensional (2-D) HIFU arrays that surrounded the limb and could dose with multiple arrays simultaneously. Each array was capable of high power (>170 W), significant electronic steering (solid angle = 57×34 deg), and depth focusing (5–20 cm). Device characterization required both individual array power measurements, and “integrated” whole cuff multiarray dosing assessment. The single array characterizations included (a) low-power beam plots, (b) high power focused power assessment in “apertured” radiation force balance tests, and (c) Schlieren beam pattern assessment. The integrated (whole cuff) behavior was evaluated using (1) integrated tissue mimicking material (TMM) phantoms replicating limbs, which included soft tissues, blood vessels, pulsatile arterial and “bleeder” blood flows, and were able to measure HIFU closed-loop targeting accuracy; and (2) TMM HIFU phantoms (measuring full power heating to 100 °C). [This research was sponsored by U.S. DARPA Contract No. HR0011-08-3-0004].
Overview of current research activities in architectural acoustics.
Authors: Muehleisen Ralph T.
Published: July 2011

One of the largest and most active technical committees in the Acoustical Society of America is the Technical Committee on Architectural Acoustics (TCAA). TCAA typically has six to eight special sessions at each meeting. Authors include university researchers, product manufacturers, and practicing acoustical consultants. This talk will focus on reviewing research and activities of TCAA. Some of the more popular TCAA research areas include Green Building Acoustics, Healthcare Acoustics, Classroom Acoustics, Room Modeling, and Auralization. Some of the more popular activities include student paper and design competitions, the development of acoustical design booklets, and work on acoustics standards.
An introduction to the Underwater Acoustics technical committee.
Authors: Isakson Marcia
Published: July 2011

Although sound speed was measured astonishingly accurately as early as 1826 by Colladon and Sturm in Lake Geneva, there was not widespread interest in underwater acoustics until the dramatic sinking of the Titanic in 1912. Today, acoustics is considered the best means of remote sensing in oceans, lakes, and estuaries due to the high attenuation of light in water. The members of the Underwater Acoustics Technical Committee are concerned with the generation and propagation of sound in an underwater environment as well as acoustic reflection and scattering from the seabed, sea surface, and objects in the water column and/or beneath the seabed. In this talk, a short history of underwater acoustics will be followed by an overview of the current state of research in the field.
A tutorial on noise-sensitivity.
Authors: Luz George
Published: July 2011

About one in five people can be categorized as “noise-sensitive.” An individual’s degree of noise-sensitivity appears to be a personal characteristic, not an acquired attitude. Because environmental noise assessments within the United States are based on average response to noise, the existence of noise-sensitive people can be a challenge for land-use planning around airports and other noise-generating facilities. Although there has been some research on noise sensitivity within the United States, the bulk of research has been conducted in Europe and Japan. The purpose of the tutorial is to review key findings from some of the most recent research on this subject.
Perceptual distinctiveness of vowels in relation to dialectal sound change.
Authors: Jacewicz Ewa , Fox Robert A.
Published: July 2011

We examine distinctiveness among four vowels /ɪ, ε, æ, a/ in Appalachian English in the perception of children (9–13 years) and adults (50–65 years) who spoke the same local variety as the talkers who produced the stimuli. Each listener responded to unique exemplars of bids, beds, bads, bides (both stressed and unstressed) produced by 40 talkers, male and female, children (8–12 years) and adults (50–65 years). The highest identification rates were for beds, and the lowest for bides. For each vowel, stressed variants yielded slightly higher rates than unstressed. Examination of confusions among spectral neighbors revealed systematic confusions between bids and beds. Confusions for bads and bides varied as a function of talker age, gender, and listener age, reflecting effects of cross-generational sound change in this dialect. In a second task, the vowels were presented in hVd-frame and stimulus uncertainty was elevated by increasing the number of vowel categories (12), talker age groups (3), and the addition of another dialect. Similar pattern of responses was obtained by different listeners (children and adults) but overall identification rates were comparatively higher. Altogether, these results show listener sensitivity to cross-generational sound change, which affects both vowel position and formant dynamics. [Work supported by NIH.]
Striation processing for sediment geoacoustic characterization.
Authors: Ren Qunyan , Hermand Jean-Pierre
Published: July 2011

Broadband spectrogram of sound radiated by a moving source, i.e., surface ship, exhibits striations. According to normal mode theory, the slope and position of the striations are related to the modal group and phase speeds, which are determined by the propagation medium and source movement. Waveguide invariant theory provides an interpretation of the phenomenon and has been applied in underwater inverse problems including source localization, sediment geoacoustic characterization, etc. The successful extraction and identification of the striations is a critical step for these applications. In this paper, a multiscale line enhancement filter based on Hessian matrix eigenvalue analysis is adopted for the features’ extraction. Typical shallow-water environment models are selected for numerical simulations. The interference structure is effectively enhanced, the striations are extracted, and their position and slope are estimated. The effects of varying the respective parameters of a sediment layer on the striations, i.e., position shift and slope change, are also discussed. Preliminary inverse results that use the striation features for sediment geoacoustic characterization are presented.
Modeling fish aggregation sounds in very shallow water to estimate numbers of calling fish in aggregations.
Authors: Sprague Mark W. , Luczkovich Joseph J.
Published: July 2011

Many fishes in the Family Sciaenidae produce courtship sounds associated with spawning. Some estuarine sciaenid species such as weakfish Cynoscion regalis, spotted seatrout C. nebulosus, and silver perch Bairdiella chrysoura occur in very shallow water (water depths 3–10 m) aggregations so large that individual calls are no longer audible above the combined sound of calling fish in the aggregation. We have measured sound levels in these aggregations that are 30 dB greater than the estimated received level of an individual fish at a distance of 1 m. To estimate the number of individual calling fish that would result in these sound levels, we have produced a model of virtual fish aggregations based on echosounder data. We used a finite difference time domain (FDTD) model to calculate the pulsed sounds from the individual fish in randomized aggregations at our virtual hydrophone location. We produced many randomized instances of fish aggregations to obtain statistical distributions of sound levels produced by different densities of calling fish. The characteristics of aggregation sounds will be presented for different densities of calling fish for these species. These calculations could lead to better estimations of fish densities from single-hydrophone measurements.
Acoustic communication in the electric yellow cichlid, Labiochromis caeruleus.
Authors: Higgs Dennis M. , Barkley Amanda N. , Radford Craig A.
Published: July 2011

The cichlidae represent an attractive model for acoustic communication as their well-characterized adaptive radiation can serve as a backdrop for testing evolutionary hypotheses. Despite interest in sound communication in cichlids, little is known of their hearing ability and less is known about hearing and sound production in the same species. The current study examined sound production, hearing, and auditory morphology in a Lake Malawi cichlid Labidochromis caeruleus. Males and females were paired in the laboratory and all behavioral and acoustic displays recorded. Hearing was tested to tone bursts and samples of recorded calls using auditory evoked potentials and morphology was assayed using MicroCT scans of intact fish. Males produced calls with dominant frequency of approximately 300 Hz but only when simultaneously performing a quiver display. Fish detected tones from 100–1000 Hz and were more sensitive to tones than to playbacks of call segments. Finally, MicroCT showed a heart-shaped swim bladder with anterior protrusions directed at the large saccular otoliths, possibly reducing self-generated noise by focusing the call away from the ears. With this combination of behavioral, morphological, and physiological approaches, we were able to fully characterize acoustic communication in this species for the first time.
The effect of noise on behavior and acoustic communication in the blacktail shiner (Cyprinella venusta).
Authors: Holt Daniel E. , Johnston Carol E.
Published: July 2011

Despite their seemingly quiet underwater habitat, freshwater fishes are not sheltered from elevated noise levels. Anthropogenic noise along with natural noise sources increase noise levels in aquatic environments. Higher noise levels can result in elevated hearing thresholds and decrease the signal-to-noise ratio of acoustic signals. Because many fishes use acoustic signals during critical life history stages, it is important to determine whether elevated noise levels affect behavior or sound production during these stages. This study describes sound production and corresponding behaviors as well as hearing in the black tail shiner (Cyprinella venusta). An attempt was also made to determine the effect of elevated noise levels on acoustic communication and behaviors associated with reproduction and aggression. Behavioral interactions of C. venusta were recorded under noisy and quiet acoustic conditions. Temporal and spectral parameters of the calls as well as the type and number of behaviors performed by the dominant male of each trial were compared between the two conditions to determine if noise affected them. Hearing sensitivity and range were determined using the auditory brainstem response approach.
Real-time monitoring and control of thermally induced lesions using high intensity focused ultrasound.
Authors: Liu Dalong , Ballard John R. , Jeunghwan Choi , Bischof John C. , Ebbini Emad S
Published: July 2011

A real-time temperature/strain imaging system for monitoring HIFU-induced lesions was implemented in conjunction with a pulsed HIFU (pHIFU) phased array driver. The integrated system is capable of collecting two-dimensional (2D) strain/temperature fields at high frame rates (>200 fps) to capture intricate tissue motions and deformations in the vicinity of the pHIFU focus. In addition, the system is capable of refocusing and updating the pHIFU beam at rates up to 1000 times per second. These capabilities of the guidance and pHIFU control allow for precise lesion formation in the presence of tissue motion and deformation due to breathing and pulsation in the vicinity of large blood vessels. We present results from in vivo experiments in the hind limbs of Copenhagen rats (250 g average). The results demonstrate the capability of the strain imaging system to estimate the thermally induced strain (due to pHIFU) in the presence of high strains from breathing and vessel pulsation in vivo. In this paper, we describe the architecture and the signal processing algorithms used in the estimation of pHIFU-induced strains. The robustness of the method will be illustrated by describing the results from the application of pHIFU beams in close proximity to femoral artery of the rat model.
Improved prediction of community noise footprints from high performance military aircraft.
Authors: Hobbs Christopher M. , Powers Russell W. , McLaughlin Dennis K. , Plotkin Kenneth J. , Morris Philip J.
Published: July 2011

Experimental research has shown how the addition of properly designed chevrons to model scale supersonic nozzles reduces the noise of the high speed jets issuing from such nozzles. It has also been shown that, to reasonable accuracy, this noise benefit scales between small- and moderate-scale nozzle geometries. The new advanced acoustic model (AAM) developed by Wyle Laboratories has the capability to use noise source data to produce dynamic acoustic footprints showing noise exposure in the vicinity of airfields: especially for landing and take-off operations. AAM uses information on aircraft engine jet exhaust noise sources for specific aircraft engine operating parameters and given flight conditions. This presentation describes the measurement and modeling of jet noise reduction using chevrons in both small and moderate scale nozzles. Then the AAM is used to demonstrate the expected change in acoustic footprint size for a full-scale jet aircraft, where it equipped with chevrons. The effects of the chevrons are described as a decibel correction to the noise source spheres used by the model. The AAM is run for a simulated trajectory of a typical operation for a jet aircraft with and without chevrons to show the effects on the acoustic footprint.
Development of fighter aircraft flight procedures for reduced noise impact.
Authors: Pilon Anthony R. , Psencik Robert A. , Cribbs Darrell W. , Elliott Jeanette M.
Published: July 2011

Lockheed Martin engineers have recently developed a unique process to rapidly develop realistic and community-friendly fighter aircraft procedures for use near airports. The process integrates known aircraft performance (takeoff distance, rate of climb, etc.) with community noise estimation tools (Noisemap, INM), allowing rapid calculation of the changes in community noise impact due to proposed changes in flight procedures or the integration of new aircraft. Automated performance calculations capture the effects caused by changes in aircraft weight, external loading, and airfield density altitude. Operational pilots from the airport under study validate each proposed procedure in a realistic flight simulator (with performance matching the actual aircraft). These “flights” ensure that each proposed profile is safe, realistic, and reasonable for that base. The process has been applied to contemporary fighter (F-16) operations, as well as those for aircraft entering service soon (F-35). When necessary, the newly developed process can be used to create flight procedures which reduce the aircraft noise impact in nearby communities. Initial studies have demonstrated that the community area significantly impacted by noise (i.e. that within the 65 DNL contour) can be significantly reduced through judicious control of power settings, climb angles, and other flight parameters, without modification of the aircraft.
Source directivity in the parabolic equation method using an inverse Fourier transform technique.
Authors: Rosenbaum Joyce E. , Atchley Anthony A. , Sparrow Victor W.
Published: July 2011

The parabolic equation (PE) method is accurate for prediction of low-frequency noise in the situation that the starting field does not emit significant energy at large elevation angles. The typical PE sound source is assumed to be omnidirectional and represented with a Gaussian starting field, defined at all heights of the grid. A method of representing a source with arbitrary directivity has been developed for the unique form of the PE starting field. By extending the defined vertical wave number spectrum of the arbitrary far-field directional function of the source to include evanescent wave numbers, the approach uses array theory and Fourier transform techniques to define the starting field. The approach recognizes the elevation angle limitation of the PE method and adheres to the accepted wavelength-dependent vertical grid point spacing, satisfying the fundamental requirements of the PE method. Results for horizontal and vertical dipole sources in the free field and above a ground surface are presented and compared with analytical solutions within the valid PE elevation angle range. [This research was funded by the Federal Aviation Administration (FAA) Western-Pacific Region through U.S. Department of Transportation Volpe National Transportation Systems Center.]
A portable calibration system for infrasound microphones.
Authors: Watson Chris , Helmericks Jay , Szuberla Curt
Published: July 2011

Infrasound signals have the characteristic that they propagate for long distances in the atmosphere. The far field recording of the signal is a convolution of the characteristics of the signal source, the atmosphere through which it propagates, and the infrasound microphones used to measure the signal. There is an emerging interest in knowing how well the signal source can be characterized using signals recorded in the far field. Characterization of the signal source requires the deconvolution of the recorded signal. Ensuring that the infrasound microphones are operating within manufacturer specifications is a standard way to simplify this process. To that end, Chaparral Physics is developing an economical calibration system that can be used to determine the calibration constants for infrasound microphones using an automated process controlled from a laptop. This paper will detail the mechanical theory associated with the calibration and the software used to collect and analyze the data.
A large scale portable infrasound network as upper atmospheric monitor.
Authors: Assink Jelle D. , Waxler Roger , Talmadge Carrick , Blom Phil , Drob Doug
Published: July 2011

Analysis of data from this summer’s large scale infrasound array deployment in the American West will be presented. The deployment consisted of an arc of arrays at a fixed range of 220 km and a northward line of arrays from 220 to 400 km. In this presentation particular attention will be given to data from the northward line. Tropospheric, stratospheric, and thermospheric arrivals were observed. The evolution with range of the arrivals’ propagation parameters and waveforms will be discussed and compared with theoretical predictions that make use of atmospheric specifications. The data input in these specifications decreases with height; the specifications above the stratosphere are based on semi-empirical models rather than observations. Naturally, the largest deviations are found in the predictions of thermospheric arrivals at the various arrays. By reducing the misfit between predictions and observations, we work on updating upper atmospheric wind models using infrasound.
Harvesting ambient acoustic energy using acoustic resonators.
Authors: Li Bin , You Jeong Ho
Published: July 2011

There is currently a high demand for the development of powering systems to supply electricity to small wireless electronic devices. This has led to various energy harvesting concepts aimed to harvest potential energy sources, such as solar, thermal, wind, and vibration/wave energies. Harvesting acoustic energy has been rarely investigated because of its lower energy density compared with other resources. Even though a single acoustic wave has the lowest energy density among the above candidates, sound is abundant in our everyday life and is currently wasted. Therefore, harvesting sound energy would be a good alternative to already existing other energy harvesters. In this work, a computational model for harvesting acoustic energy using a Helmholtz resonator will be presented. To convert acoustic energy to electricity, piezoelectric wires are placed inside a Helmholtz resonator. When an external sound excites the resonator at acoustic resonant frequencies, the amplified acoustic pressure is developed and generates the vibration motion of the piezoelectric wires resulting in electricity generation. Fundamental mechanisms coupling the electrical power generation by acoustic resonant behavior of Helmholtz resonators will be presented. The effects of geometries of Helmholtz resonators and piezoelectric wires on electricity generation have been studied numerically and will be presented.
Suprasegmental features of Chinese-accented English.
Authors: Li Bin , Shuai Lan
Published: July 2011

This study compares read speech by Cantonese and Mandarin learners of English with those by native speakers of English. The utterances produced by learners of English are all rated as accented. We aim to identify measurable prosodic differences leading to such perceptual judgment. The prosodic correlates we examine include both syllable duration and pitch values. Our preliminary results reveal in generally mean syllable durations of Cantonese and Mandarins learners are very similar, and much longer than that of the native speakers of English. It is also found that all learners’ production exhibits much greater variations in duration than native speakers. Examination on duration of stressed and unstressed syllables reveals more differences across L1 groups. With regard to pitch correlates, a much wider pitch range is found in the production of native speakers of English than in those of both Mandarin and Cantonese learners of English. Of the Chinese learners, Mandarin group employ a wider pitch range than Cantonese. Moreover, Cantonese learners’ speech is found dominated by a rather “flat” overall pitch contour. We propose that the prosodic deviations in Chinese learners’ English from a native speaker can be accounted for from the perspective of rhythmic and tone system in Chinese.
Acoustic correlates of perceptual ratings of foreign-accented English.
Authors: McCullough Elizabeth
Published: July 2011

What acoustic cues contribute to the perception of foreign accent? While many previous studies have explored this question for a single foreign accent, few have simultaneously considered several foreign accents in a single language. In this perception study, ten American English listeners rated 360 stop-vowel sequences extracted from English words produced by L1 American English, L1 Hindi, L1 Korean, and L1 Mandarin talkers on a continuous scale of degree of foreign accent. Despite this minimal input, listeners robustly rated Korean- and Mandarin-accented productions as having a higher degree of foreign accent than native productions, and Hindi-accented productions as having a higher degree of foreign accent than all other productions. Acoustic cues of the stimuli were measured, and stepwise linear regression models revealed that vowel quality and VOT contributed significantly to the ratings. These cues collectively accounted for 26% of the variance in the ratings of all stimuli and for 38% of the variance in the ratings of stimuli beginning with voiceless stops. The results suggest that vowel quality and VOT contribute substantially to the perception of foreign accent in stop-vowel sequences, and perhaps in larger units of speech.
Decomposition of vowel and consonant contributions to the time-varying vocal tract shape.
Authors: Story Brad H. , Bunton Kate
Published: July 2011

An important aspect of speech production is the temporal overlap of the different vocal tract movements that produce vowels and consonants. In previous work a method was proposed for separating the time-varying vocal tract shape of a talker into vowel transitions and consonant superposition functions [Story, J. Acoust. Soc. Am. 126 (2009)]. The purpose of this study was to apply the method to a wider variety of consonant and vowel contexts than were previously reported. The specific aims were to analyze x-ray microbeam data produced by one male speaker for three stop consonants [p,t,k] embedded in six vowel contexts [ia, ai, oae, aeo, ii, aa] and reconstruct them as separate consonant and vowel components. When superimposed, these were shown to be reasonable approximations of the original VCVs, as assessed qualitatively by visual inspection and quantitatively by calculating rms error and correlation coefficients. The information extracted through these analyzes can be used as input to a speech production model to simulate the original utterances. [Research supported by NIH R01-DC04789.]
Rocket noise predicton models: An update.
Authors: Sutherland Louis C.
Published: July 2011

This paper summarizes revised or improved elements of rocket engine noise prediction models including overall sound power for rocket, noise source locations in undeflected/deflected rocket exhausts, sound power and/or pressure spectrum, and directivity for the rocket noise sources at, and after, launch with emphasis on locations on the launch tower. Finally, influence of the flow deflector and water injection on the rocket noise levels is considered. The data presented are from a number of previously published reports by the author, and others, including Eldred, Crocker, and Potter. The sound power of the rocket is predicted by a Lighthill theory-consistent model as proportional to a flow-dependent multiplier corresponding to the ratio of flow mechanical power at the supersonic core tip to mechanical power at nozzle exit. Data from 27 measurements of sound power of jets and rockets covering a range from 135 to 200 dB re 1 PW show a prediction accuracy of +/−2.8 dB. The model is a more robust approach to rocket sound prediction than previous methods such as assuming 1% acoustic efficiency. The paper also presents graphical models for the other rocket noise parameters defined above.
Spectrum of measured infrasonic emissions from clear air turbulence.
Authors: Zuckerwar Allan J. , Weistroffer George R. , Shams Qamar A.
Published: July 2011

An array of three infrasonic microphones (0.2–20 Hz), operating continuously in the field at NASA Langley Research Center, on several occasions received a class of signals interpreted as infrasonic emissions from clear air turbulence. The presence and location of the turbulence were confirmed by pilot reports (PIREPS), and the direction of emitted signals toward the array was determined by slowness mapping. The coherence of the signals among the three microphone pairs in the array was close to unity. The amplitude spectrum of the received signals was found to fit a power law having an exponent of −7/2, which disagrees with the exponent of −7/4 of Meecham and Ford [J. Acoust. Soc. Am. 30, 318–322 (1958)], based on turbulence self-noise and with the exponent of −1 of Meecham [J. Acoust. Soc. Am. 33, 149–155 (1971)], based on mean shear fluctuations. Thus the above models do not account for the observed spectrum. Two case histories are described in detail.
Determining the importance of building features in sonic boom simulation and comparison to measured data.
Authors: Riegel Kimberly A. , Sparrow Victor W.
Published: July 2011

Accurately simulating sonic booms in and around structures is the first step to determining the effect on the structures and the people who inhabit them. In order to do these simulations, a combined ray tracing/radiosity method was developed. A variety of parameters was examined in order to determine their effect on the resulting sound field. These parameters include building façade features, building absorption, and diffusion coefficients. These simulations were compared to the NASA 2009 SonicBOBS test data to determine the accuracy of the simulations. Two building configurations were examined: a single building and a two building configuration. [Work supported by the NASA. The authors appreciate NASA making test data available for this work.]
Interactive noise mapping methods to support resource management in National Parks.
Authors: Fristrup Kurt M. , Lee Cynthia
Published: July 2011

Noise modeling of complex management scenarios spanning large areas requires many days of processing time. To enable a rapid, iterative process for formulating and evaluating management alternatives, the NPS Natural Sounds and Night Skies Division and the John A. Volpe National Transportation Systems Center developed methods to separate noise modeling into two steps. Noise models, such as INM 6.2, are used to predict noise exposures from each combination of aircraft type and route that could be included in the scenarios being considered. This processing step is embarrassingly parallel without modifying any software. The individual noise predictions are ingested by a second program, which combines noise doses to predict aggregate noise exposure from the traffic on all operational routes. For noise duration metrics, such as audibility or time above 35 dB(A), the aggregation of noise exposures requires an algorithm to account for the potential overlap between adjacent noise events. A relatively simple formula has been derived using the assumption that waiting times between noise events have an exponential distribution; this fits model validation data from Grand Canyon quite well. The interactive mapping tool evaluates alternatives in about 1 min of compute time, facilitating intuitive understanding of the consequences of management options.
Prof. Rongju Wei and the Institute of Acoustics: A valuable source of US graduate students.
Authors: Crum Lawrence A. , Tu Juan
Published: July 2011

Prof. Rongjue Wei was very interested in ensuring that students at the Institute of Acoustics in Nanjing had an opportunity to do graduate work in the United States. He had many contacts with researchers at institutions around the world that performed acoustics research. Over a period of 25 years, Prof. Wei communicated with one of the authors (L.A.C.) about various research efforts undertaken in his laboratory and at various times, suggesting that students at Nanjing could move directly into these programs. On several occasions, these students were admitted to the author’s institution and worked under him or his colleagues. This relationship with Nanjing was very productive, producing some outstanding graduates, and still continues.
A re-examination of human underwater sound localization abilities in the azimuth.
Authors: Qin Michael K. , Aaronson Neil , Babina Matthew , Cudahy Edward
Published: July 2011

Divers are frequently exposed to underwater sounds. The subjective impression of the diving community is that sound localization underwater is extremely difficult. However, Feinstein [1973a, 1973b] found underwater minimum audible angles (MAAs) to be approximately 10 deg. To the extent that underwater MAAs reflect the general performance of the binaural system, this would suggest that humans should be reasonably effective at underwater sound localization. A re-examination of the underwater MAAs, with greater subject and environment control, was performed. The present work indicates underwater MAAs at approximately 20–30 deg, significantly poorer than previous findings. [Work supported by the ONR.]
Effects of spatial visual information and head motion cues on auditory spatial judgments.
Authors: Ericson Mark A. , Weatherless Rachel
Published: July 2011

Virtual audio systems are commonly used today to create auditory environments for various listening tasks. The dimensions and absorption characteristics of the surrounding real visual space often do not match the virtual auditory listening space. This mismatch in spatial information has been shown to have a small or negligible effect in the perceived direction of sound sources. However, spatial cues can have a large effect on perceived auditory distance. The most veridical auditory spatial renderings are ones that match the visual space around the observer. Several experiments were conducted to investigate the effects of visual spatial information and head motion cues on perceived auditory distance. In the first experimental condition, naive observers were deprived of all visual cues while making judgments on the egocentric distance of sound sources played over loudspeakers. In the second condition, subjects were presented with mismatched visual and auditory spatial cues via a manikin. The acoustic manikin was either non-moving or would rotate in correlation with the listener’s head motion. In the last (control) condition, sound sources were presented from loudspeakers with matching visual and auditory cues. The effects of the visual spatial cues and head motion cues on auditory distance judgments will be described.
Amplitude modulation detection by human listeners in sound fields.
Authors: Zahorik Pavel , Kim Duck O. , Kuwada Shigeyuki , Anderson Paul W. , Brandewie Eugene , Srinivasan Nirmal Kumar
Published: July 2011

The temporal modulation transfer function (TMTF) approach allows techniques from linear system analysis to be used to predict how the auditory system will respond to arbitrary patterns of amplitude modulation (AM). Although this approach forms the basis for a standard method of predicting speech intelligibility based on estimates of the acoustical modulation transfer function (MTF) between source and receiver, human sensitivity to AM as characterized by the TMTF has not been extensively studied under realistic listening conditions, such as in reverberant sound fields. Here, TMTFs (octave bands from 2–512 Hz) were obtained in three listening conditions simulated using virtual auditory space techniques: diotic, anechoic sound field, and reverberant room sound field. TMTFs were then related to acoustic MTFs estimated using two different methods in each of the listening conditions. Both diotic and anechoic data were found to be in good agreement with classic results, but AM thresholds in the reverberant room were lower than predictions based on acoustic MTFs. This result suggests that simple linear systems techniques may not be appropriate for predicting TMTFs from acoustical MTFs in reverberant sound fields, and may be suggestive of mechanisms that functionally enhance modulation during reverberant listening.
Investigating the relationship between carrier frequency and effective bandwidth of peripheral filtering in an amplitude-modulation notch detection task.
Authors: Shim Allison I. , Berg Bruce G. , Borucki Ewa M.
Published: July 2011

Effective bandwidths of initial auditory temporal processing are measured in an amplitude-modulation in notched-noise detection task. The signal is a 200 Hz wide, sinusoidally amplitude-modulated narrowband noise centered at four different center frequencies. The frequency of the sinusoidal modulator is set at 10 Hz. The use of a slow modulation frequency aims to avoid possible central limitations of temporal processing at higher modulation frequencies. Threshold functions are obtained for 10–14 notch widths for each center frequency to determine the maximum notch width at which the masker has an effect. Averaged thresholds for each center frequency are fitted using a leaky integrator model with a min/max decision statistic. Two free-parameters define the high and low slopes of the initial bandpass filter and a third represents internal noise. Filter bandwidth estimates are wider than critical bands and do not exhibit a constant-Q relationship. It is proposed that the initial level of integration is not a basilar membrane process but a process that involves the reconstruction of information from the auditory nerve. [Work supported by NSF Grant No. BCS-0764003]