bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic condition monitoring of wind turbines: Tip faults
Authors: Comboni Daniel J. , Fazenda Bruno
Published: September 2012

As a significant and growing source of the world’s energy, wind turbine reliability is becoming a major concern. At least two fault detection techniques for condition monitoring of wind turbine blades have been reported in early literature, i.e. acoustic emissions and optical strain sensors. These require off-site measurement. The work presented here offers an alternative non-contact fault detection method based on the noise emission from the turbine during operation. An investigation has been carried out on a micro wind turbine under laboratory conditions. 4 severity levels for a fault have been planted in the form of added weight at the tip of one blade to simulate inhomogeneous debris or ice build up. Acoustic data is obtained at a single microphone placed in front of the rotor. Two prediction methods have been developed and tested on real data: one based on a single feature - rotational frequency spectral magnitude; and another based on a fuzzy logic interference using two inputs - spectral peak and rotational peak variation with time. Results show that the single spectral peak feature can be used to determine fault severity in ranges. The implementation of the fuzzy logic using a further input feature is shown to significantly improve the detection accuracy.
Physics of music for musicians, architects, and science students: Designing a multi-level platform for an undergraduate course
Authors: Hall Robert G.
Published: September 2012

This presentation will describe the development of a new course in the Physics of Music at Laurentian University in Sudbury, Ontario. While the creation of the course was spurred on by the opening of a new School of Architecture in 2013 and the desire to provide an elective containing acoustics for that program, the project also has the added challenges of: developing a course that is available to music students (many of whom have little or no science background), creating a course that is an attractive elective for students across campus, initiating a course that meets the elective requirements for engineering students, and building a course that contains sufficient physics so that it may be cross-listed as a physics course. The presentation will outline the specifics of each of the required parameters and give specifics as to the multi-level project choices within the course that have been developed to allow the different student constituencies to satisfy their pedagogical needs. Also addressed will be the requisite teaching methods used to allow on-line participation, while still encouraging and requiring attendance at the weekly lectures.
Introduction to workshop goals
Authors: Brooks Bennett M. , Schulte-Fortkamp Brigitte , Kang Jian
Published: September 2012

The goal of this workshop is to work toward methodology standardization for the advancement of the developing field of soundscape measurement, analysis and design. The workshop will focus on the terminology lexicon used for soundscape subject interviews. Interviews of local experts, residents and other users and inhabitants of the sonic environment can yield insights into both personal reactions and universal observations. The specific terminology used in this process may significantly affect the outcomes. As the success of a new research or development project can depend on the lessons learned from previous projects, the standardization of interview techniques becomes increasingly important. Workshop participants are invited to develop a standardized lexicon of descriptors for field use in interview questionnaires. The lexicon development will be based on the results of earlier ASA soundscape workshops, and the concurrent activities in ISO and COST Working Groups. An introductory keynote address will review the topics, objectives, and procedures for the day's discussion. The participants will then break out into smaller subgroups to review key issues and to assess the available lexicon terms. The entire group will reassemble to report, assess, and prioritize the proposed actions.
Vibrations of composite bimorph cantilever with multidomain structures
Authors: Sedorook David , Nadtochiy Andrew , Ostrovskii Igor
Published: September 2012

The vibrating piezoelectric cantilevers are important objects in contemporary physical acoustics and their applications including the hot topic of robotic flying insects, MEMS, and various actuators. In this work, we study different cantilevers consisting of the piezoelectric layers and a thin steel layer. The three-layer bimorph composite cantilever includes a central steel sheet covered with two oppositely polarized coatings made of a piezoelectric ceramic. We compare the amplitudes of tip vibrations in the bimorph composite structures with the simpler cases of a single piezoelectric layer with one to three ferroelectric domains sitting on a steel substrate as well as without the steel support. Theoretical calculations of the amplitude of acoustical vibrations of the actuator tip are performed with the help of a finite element method developed for piezoelectric media. The corresponding codes were verified and adopted by the experimental measurements from the 12-mm long and 0.5-mm thick PZT-cantilever vibrating on its fundamental mode at frequency 1.12 kHz. The vibration amplitude of a cantilever with 2 or 3 periodically poled domains is the highest at the 2nd or 3rd resonance frequency, respectively.
Spatial variation of ultrasonic attenuation coefficient in freshly excised human calvarium
Authors: Garcia Armando , Turner Joseph A. , Salzar Robert S.
Published: September 2012

The propagation of ultrasound through human calvarium poses a great challenge for transcranial diagnosis and treatment of several medical conditions. Moreover, better understanding of how sound waves are attenuated in the human calvarium is gaining relevance with the recent awareness of the problem of blast wave induced traumatic brain injury. In the present study, the spatial variability of ultrasonic properties was evaluated for relevant frequencies of 0.5, 1, and 2.25 MHz. A total of eighteen specimens from four donors were tested using a through-transmission configuration. With the aid of a two interface model, the ultrasonic attenuation coefficient was determined from the total energy loss at various locations on the specimens. Mean volumetric densities at various locations on the samples were determined from computed tomography images. The results show good correlation between attenuation and volumetric density, particularly for the higher frequencies. In addition, the spatial variability of the attenuation, within a single person and with respect to different people, was found to be much larger than expected. These results are anticipated to have a major impact on transcranial biomedical research. [Support of the Army Research Office for this work is gratefully acknowledged.]
Active structural health monitoring during sub-orbital space flight
Authors: Zagrai Andrei N. , Reiser William , Runnels Brandon , White Chris , Light-Marquez Abraham , Marinsek Stephen , Murray Andrew , Stuart Taylor Stuart , Park Gyuhae , Farrar Charles
Published: September 2012

Increasing involvement of commercial enterprises in space activities is among leading forces behind a renewed interest in structural diagnostic methodologies promising potential for improving safety, operability and cost effectiveness of launch vehicles and spaceships. It is envisioned that unobtrusive, real time structural health monitoring (SHM) systems may assist in space vehicle’s prelaunch qualification, orbital operation, safe disintegration during reentry or recertification for a next flight. SHM experiment utilizing piezoelectric wafer active sensors in conjunction with electro-mechanical impedance measurements has been develop to explore feasibility of active structural health monitoring during suborbital space flight. Details of experiment are discussed and some results obtained in real time for all segments of vehicle’s trajectory are presented. Experimental data collected during suborbital space flight has shown feasibility of SHM in the challenging environment, utility of thin wafer piezoelectric sensors as active elements of spacecraft SHM system, and potential of the electro-mechanical impedance method for real time structural integrity assessment of the payload.
Modeling and signal processing for guided wave structural health monitoring
Authors: Croxford Anthony , Wilcox Paul D.
Published: September 2012

Guided wave approaches are a key technique for the implementation of structural health monitoring with a sparse sensor array, offering good sensitivity over a reasonable range. There are however several difficulties, particularly how the system can be modelled to predict performance and how acquired data can be used most effectively post capture. This paper looks at both these issues, starting with a study of the modelling of the scattering of guided waves from features. Models of both the scattering from structural features and predicted damage types can then be used to determine the sensitivity of any network and the process of their derivation and use is described here. In order to maximise this sensitivity it is important to use the data in the most efficient way possible. This is accomplished through the use of statistical models of the changes in the signal and fitting maximum likelihood estimators to these. In choosing a good model of the signal a statistical detector can be designed to optimise the performance for a given use case, be that detection or localisation.
Characterization of porous materials using ultrasonic slow wave
Authors: Lin Lin , Peterson Michael , Greenberg Alan
Published: September 2012

Porous materials are critical engineering components in many process industries. Although porous materials have been successfully utilized in many areas, characterization of porous structures is still a significant problem limiting the applications of porous materials, especially when the application involves the change of porous structure. Ultrasonic techniques have been reported for successful applications on material characterization, including porous materials. This research utilized an acoustic technique for permeability measurement by measuring the critical wave number of Biot’s slow longitudinal wave. The slow longitudinal wave can serve as an important tool for investigating the ability of fluids to penetrate into porous materials. Since the slow longitudinal wave is associated with out-of-phase movement of the pore fluid relative to the matrix structure, it is very sensitive to the permeability of the porous formation. In Biot’s theory the slow wave is highly attenuated below a critical frequency. The critical wave number can be directly related to the permeability of porous materials. The measurement of the critical wave number provides a unique method to obtain the permeability measurement, which can be apply to structure monitoring, quality control, etc.
Determination of leaky Lamb wave modal attenuation coefficient on a solid plate
Authors: Kim Wan-Gu , Yoon Suk Wang
Published: September 2012

Leaky Lamb wave is practically important in an immersion technique of nondestructive evaluation for a solid plate. It is necessary to determine its modal attenuation coefficient in order to evaluate plate defects in industry and to diagnose osteoporosis in medical applications. In this study we present a method to determine the modal attenuation coefficient of leaky Lamb wave using two-dimensional Fourier filtering. A complex leaky Lamb wave signal from a solid plate can be decomposed into several modal signals on frequency-space domain through two-dimensional Fourier filtering. It makes possible to experimentally determine the modal attenuation coefficient along an aluminum plate in water. It is well explained by theoretical estimation with the dispersion relation of leaky Lamb wave.
Simultaneous thickness, velocity, density, and attenuation measurement of a thin layer by time-resolved acoustic microscopy
Authors: Chen Jian , Bai Xiaolong , Yang Keji , Ju Bingfeng , Meng Jianxing
Published: September 2012

An ultrasonic method for simultaneous determination of thickness, velocity, density and attenuation of thin layer using a time-resolved acoustic microscopy is proposed. Reflection from the thin layer is represented as a function of three dimensionless parameters which are determined from the experimentally normal incidence component of the two dimensional reflection spectrum R(θ,ω) derived based on the inversion of V(z,t) technique with time-resolved acoustic microscopy. The thickness of the thin layer is derived from the signals received from the layer itself considering the geometrical relations when the lens focused on the sample’s surfaces. The simultaneous determination of thickness, velocity, density and attenuation of thin stainless steel plate by using a point-focusing transducer with nominal frequency of around 50MHz were carried out. The determined material properties are comparable, in which the thickness, velocity and density can be measured with a percentage biases less than 5% and the attenuation is close to its real value. The present preliminary work shows the high efficiency, viability and capability of the new non-destructive technique in simultaneously characterize basic mechanical and geometrical properties of thin layers.
Influence of lexical and acoustic context on phonetic categorization depends on listening situation
Authors: Holt Lori L. , Reinisch Eva
Published: September 2012

Phonetic categorization is influenced by multiple sources of contextual information, but little is known about how different sources of information interact. We examined the relative influence of lexical versus acoustic contexts on phonetic categorization of sounds along [s]-[S] continua embedded in word-nonword pairs (e.g., a[S]amed-a[s]amed, ca[s]ino-ca[S]ino). These categorization targets were preceded by sequences of 12 nonspeech tones with mean frequencies a standard deviation above or below the spectral means of the endpoint fricatives. Listeners’ [s]-[S] categorization was influenced by lexical information, exhibiting a Ganong effect with categorization shifted toward responses consistent with words, and also by acoustic context. The effect of the tone sequence was spectrally contrastive; there were more [S] responses (low spectral mean) following higher-frequency tones and more [s] responses (high spectral mean) following lower-frequency tones. In addition, the influence of acoustic relative to lexical context was modulated by listening environment. When the informational load of the lexical context was low (four word-nonword continua) acoustic context exerted a relatively greater influence than when the informational load of the lexical context was high (forty word-nonword continua). Multiple sources of context interact to influence phonetic categorization and the relative influence of different information sources is flexibly modulated by listening environment.
Refining bouba-kiki: Phonetic detail and object dimensionality in sound-shape correspondences
Authors: D'Onofrio Annette
Published: September 2012

Speakers cross-linguistically associate non-words that have round vowels, such as /buba/, with round shapes, and non-words without round vowels, such as /kike/, with spiky shapes (e.g. Kohler 1947). While this link has been attributed to cognitive associations between rounded vowel sounds and images of rounded lips, stimuli have conflated vowel roundness with other phonetic features that may also contribute to the correspondence. In this study, 200 listeners matched abstract objects with nonsense words that systematically varied by vowel frontness, consonant place of articulation, and consonant voicing. Listeners are significantly more likely to select a spiky shape over a round shape when given words with voiceless consonants, alveolar consonants, and front vowels; combinations of these features strengthen the effect. These findings are corroborated in the realm of real-world objects. 102 participants were more likely to name a rounded member of a real-world object class when hearing a word containing non-front vowels than when hearing a word containing front vowels. Further, two- versus three-dimensional object roundness influences the strength of this association. This study provides an empirically and phonetically refined perspective on the paradigm, demonstrating the benefit of considering both detailed phonetic correlates and refined object properties in work on sound symbolism.
The effect of segmental makeup on Mandarin word and tone recognition
Authors: Lai Yuwen , Wu Sheng-Hung
Published: September 2012

The present study adopts the gating paradigm to investigate the effect of onset sonorancy, and coda on Mandarin spoken word and tone recognition. Eight tonal quadruplets (all monosyllabic) with different initial segment (obstruent or sonorant), coda composition (no coda, alveolar nasal, or velar nasal) were used as the stimuli. The gates were formed by a 40-ms increment from the beginning of each word. Twenty native listeners from Taiwan were asked to listen to each stimulus, click the corresponding tone number using a mouse, write down the word and then give their confidence rating on the answer. The Isolation point (IP) based on correct word identification (both segment and tone) and the tone isolation point (TIP) were analyzed. The results indicated that tone recognition can be done before the offset of the stimuli. Tone 1 has an earlier IP than Tone 4, followed by Tones 3 and then Tone 2. Sonorant-initial words have a significant earlier IP than obstruent-initial ones. Words without coda have an earlier IP than alveolar nasal, followed by velar nasals. The processing time course for tone and segment and the effect of tonal features on word processing will be discussed.
Do preceding prosodic patterns influence word recognition in Spanish?
Authors: Morrill Tuuli , Dilley Laura C. , Navarro Jessica
Published: September 2012

Recent work shows lexical recognition in English is influenced by prosodic characteristics of preceding words (e.g., Dilley et al, 2010, Journal of Memory and Language). This study investigates whether preceding prosody affects lexical recognition in Spanish, a language with productive lexical stress contrasts (e.g., saco ‘bag’ vs. sacó ‘he carried out’). In an experiment, each of 30 disyllabic test items was embedded in a carrier phrase; each item was consistent with one of two lexical interpretations that were distinguished by having primary stress on the initial vs. final syllable (e.g., saco vs. sacó). The prosody of words preceding the test item was resynthesized with one of two fundamental frequency and timing patterns predicted to generate distinct patterns of syllable prominence favoring perception of primary stress on either the initial or final syllable of the test item. The acoustic characteristics of the test item were identical across prosody conditions. If perception of lexical stress depends in part on prosodic characteristics of the context, then prosody preceding test items should influence lexical perception in Spanish. These findings have implications for understanding the perception of lexical stress during word recognition in languages exhibiting productive lexical stress contrasts.
Influence of recent linguistic exposure on the segmentation of an unfamiliar language
Authors: Namjoshi Jui , Tremblay Annie , Broersma Mirjam , Kim Sahyang , Cho Taehong
Published: September 2012

Studies have shown that listeners segmenting unfamiliar languages transfer native-language (L1) segmentation cues. These studies, however, conflated L1 and recent linguistic exposure. The present study investigates the relative influences of L1 and recent linguistic exposure on the use of prosodic cues for segmenting an artificial language (AL). Participants were L1-French listeners, high-proficiency L2-French L1-English listeners, and L1-English listeners without functional knowledge of French. The prosodic cue assessed was F0 rise, which is word-final in French, but in English tends to be word-initial. 30 participants heard a 20-minute AL speech stream with word-final boundaries marked by F0 rise, and decided in a subsequent listening task which of two words (without word-final F0 rise) had been heard in the speech stream. The analyses revealed a marginally significant effect of L1 (all listeners) and, importantly, a significant effect of recent linguistic exposure (L1-French and L2-French listeners): accuracy increased with decreasing time in the US since the listeners’ last significant (3+ months) stay in a French-speaking environment. Interestingly, no effect of L2 proficiency was found (L2-French listeners).
Time-course of lexical knowledge use in processing pronunciation variants
Authors: Sajin Stanislav M. , Connine Cynthia M.
Published: September 2012

Three experiments examined how listeners process words that are produced with a context conditioned sound change, fricative assimilation. In fricative assimilation, a word final /s/ can change to a /∫ / when a following word begins with an approximate segment (e.g., dress yacht --> dresh yacht). Fricative assimilation is blocked in other segmental environments such as plosives (e.g., dress boat will not alter the word final /s/). Previous research revealed that phonological variation is acceptable as long as it is licensed by the context in which it is embedded (Gaskell &Marslen-Wilson, 1996). However, there is indication that such licensing effects are largely consigned to particular types of assimilation (e.g., place assimilation) and that other word-final variations (e.g., flap variants), which happen more often in natural speech, have a separate phonological representation that is dependent on the frequency with which the variation occurs (Ranbom, Connine, &Yudman, 2009). The present research addresses how assimilated speech is processed in recognizing spoken words, and, specifically, how different sources of knowledge (lexical and phonological context) are utilized at different times during processing. The results point out that word knowledge is not essential for utilizing the phonological context during recognition, but it permits earlier use of the phonological context in recognizing the pronunciation variant.
The contribution of individual words to the meaning of sentences
Authors: Veliz Amber M. , Bell Theodore S.
Published: September 2012

The studies purpose was assessing the contribution of individual words of a sentence to its overall intelligibility. The dependent variable was number of target words in each sentence correctly identified at each of three possible word positions, initial, middle, and last. The question of interest was how degradation of audibility of the initial word would affect other words by decreasing the semantic context for those later words resulting from the audibility of the first word. Other variables in the design included presentation levels that resulted in overall performance from 50 to 100 percent correct. There was a three way interaction of word position, masker, and presentation level on performance scores. Noise levels were fixed at 60 dB SPL, and speech levels were varied to -3, -6 and -9 signal-to-noise ratio (SNR). Between subject factors in the ANOVA design were SNR (-3, -6, and -9 db), and masker (flat or enhanced).
Sentence recognition as a function of the number of talkers in competing multi-talker babble
Authors: Van Engen Kristin , Chandrasekaran Bharath
Published: September 2012

Multiple-talker babble is used in studies of speech perception and processing both as a tool for loading perceptual and cognitive tasks and for direct assessment of speech perception in noise. Single interfering talkers and babbles containing few talkers differ dramatically, however, from babbles with high numbers of talkers. While low N-talker babbles provide greater opportunities for "glimpsing" speech targets during spectral and temporal dips in the maskers (i.e., less energetic masking), the linguistic information available to listeners in the maskers themselves also imposes higher-level interference (i.e., informational masking) that may detract from the identification of target speech. In order to assess the relative overall masking effects of N-talker babble for sentence recognition, the current study utilizes a range of maskers varying in N (1-8), as well as speech-shaped noise. Data collected to date show that performance declines as talkers are added to the masker (that is, as energetic masking increases), but that performance in 6-8 talker babble is significantly better than in speech-shaped noise. Individual variability on speech perception in these various maskers is being assessed by comparing performance on the speech-in-noise task to performance on a range of cognitive and psychoacoustic tasks.
Illumination waveform design for non-Gaussian multi-hypothesis target classification in cognitive radar
Authors: Wang Ke N. , Clark Grace A. , Romero Ric
Published: September 2012

A cognitive radar (CR) system is one that observes and learns from the environment; then uses a dynamic closed-loop feedback mechanism to adapt the illumination waveform so as to provide system performance improvements over traditional radar systems. Romero et al. recently developed a CR system that performs multiple hypothesis target classification and exploits the spectral sparsity of correlated narrowband target responses to achieve significant performance improvements over traditional radars that use wideband illumination pulses. This CR system was designed for Gaussian target responses. This research generalizes the CR system to deal effectively with arbitrary non-Gaussian distributed target responses via two key contributions: (1) an important statistical expected value operation that is usually evaluated in closed form is evaluated numerically using an ensemble averaging operation, and (2) a powerful new statistical sampling algorithm and a kernel density estimator are applied to draw complex target samples from target distributions specified by both a desired power spectral density and an arbitrary desired probability density function. Simulations using non-Gaussian targets demonstrate very effective algorithm performance.
Randomized sample-level interpolation for audio content manipulation
Authors: Hosakere Shivaswamy Samarth , Roessner Stephen , Zhou Xiang , Ren Gang , Bocko Mark , Headlam Dave
Published: September 2012

In this paper we propose a novel audio signal manipulation algorithm based on sample-level interpolations that can generate multiple unique versions of an audio file without creating any perceptual difference. The proposed algorithm enables important applications such as digital rights management and file distribution tracking. The simplest sample-level interpolation method is based on time domain interpolation of fixed-length audio frames. The processing algorithm first segments the audio signal into fixed-length frames. For each frame, we perform a slight time compression or extension using an audio sample interpolation algorithm and then we recombine the manipulated audio samples to form a manipulated version of the original audio files. To enable better security features a randomization program is applied to control the frame-length and manipulation-length using pseudo-random sequences. The result of this algorithm is effectively a form of weak frequency modulation. If the fame size is larger than the compression/extension sample number, these compression/extension manipulations will not produce any audible difference. Various subjective evaluation experiments are conducted to decide the extent of the admissible processing parameters that will not cause noticeable difference in both fixed-length and randomized-length sample manipulation. The authors also provide several implementation examples and a brief summary.
Phase discontinuity detection as a means of detecting tampering with speech recordings
Authors: Helffrich Jerome , Harrison John D.
Published: September 2012

In the forensic analysis of speech recordings, it is frequently necessary to validate the authenticity of the recording—for example, to determine if it has been altered for the purpose of changing the meaning of what was spoken. One method for doing this is to exploit an incidental steady tonal content in the recording, and look for sudden, discontinuous changes in the phase of that tone. We report on the development of an algorithm based on this idea, to be used for detecting edits in digital or analog speech recordings. Our development process included generating a corpus from the TIMIT speech database, designing an algorithm to exploit possible phase discontinuities in the recorded signals at edit sites, and testing the algorithm against the corpus with both edited and unedited copies of the sentence material. A statistical analysis of the performance of the algorithm on sentences contaminated by noise and compressed by various digital compression schemes will be given.
Exact parabolic equation for the sound field in inhomogeneous ocean
Authors: Maltsev Nikolai
Published: September 2012

A system of equations ∂P/∂x=iωρu,∂u/∂x=(iωρ)-1(−▵yz+▿yzρ,▿yz)−(ω/c)2)P where P(r).u(r) are sound pressure and horizontal particle velocity, c(r),ρ(r)-sound speed and density, ω-angular frequency and ▵yz,▿yz are laplacian and gradient in the plane (y,z), are an exact equations for the P(r) and u(r), derived from Euler equations of small motion of compressible fluid. They have first order with respect to x and ready for different marching type algorithms like split-step and Crank-Nicholson, without any approximations of operators, unlike traditional PE scheme. Different examples, illustrating applications of this equations are presented.
Applications of a higher order operator splitting scheme on parabolic-equation methods for modeling underwater sound propagation
Authors: Lin Ying-Tsong , Duda Timothy F. , Collis Jon M. , Newhall Arthur E.
Published: September 2012

A higher order operator splitting scheme is presented to increase the accuracy of parabolic-equation (PE) methods. This splitting scheme is essentially applied to the square-root Helmholtz operator resulting from the PE approximation, and it can benefit both the split-step Fourier and split-step Padé methods for modeling sound propagation in three-dimensional environments. Note that the square-root Helmholtz operator in the split-step Fourier PE method is split into a free propagator and a phase anomaly, but in the split-step Padé PE method it is split into two one-dimensional transverse derivatives. Our higher order scheme can handle these two different types of operator splittings, and accuracy improvements come from the fact that our computation includes (to second order) cross terms of the split operators. Numerical underwater acoustic examples are provided to demonstrate the performance of this scheme and comparisons against other schemes. [Work supported by the Office of Naval Research.]
Propagation modeling of under-ice transmissions using the parabolic equation
Authors: Heaney Kevin D. , Campbell Richard L. , Frietag Lee F.
Published: September 2012

A recent reformulation of the RAM Parabolic Equation model (OASIS’ CRAM model) permits efficient Nx2D propagation modelling, including ACOMMS performance estimation. This model is currently set up as a 3-layer propagation model. The 3-layers commonly used are water-column, sediment and basement - where the water-column and sediment have a depth dependent compressional speed, density and attenuation. The basement is an acoustic half-space with a sponge. To model under-ice propagation, the 3-layers can set up as sea-ice, water-column and seafloor. The only loss of generality is the single half-space seafloor, although bottom interaction is not as important a feature in the iso-thermal, upward refracting sound speed profiles in northern latitudes. The ice is modeled as an iso-speed (1700 m/s, rho = .988 kg/m3, alpha= 0.3dB/lambda) fluid on-top of the sea-water. The ice-water boundary is input into the code the same way a complex bathymetric profile is used. Although this approach doesn’t include shear propagation - an important source of frequency dependent attenuation, it does accurately model the scattering within the water column induced by interactions with the complex under-ice morphology. Comparison of measurements with models will be made for 900 Hz broadband transmissions to ranges of 50 km.
Three-dimensional numerical modeling of sound propagation and scattering in the deep ocean with elastic (shear) bottoms
Authors: Udovydchenkov Ilya A. , Stephen Ralph A. , Duda Timothy F. , Lin Ying-Tsong , Peter Daniel
Published: September 2012

A major challenge in bottom-interacting ocean acoustics is to include an accurate description of environmental variability in a computationally feasible model. Wave field predictions are often difficult in environments with strong range dependence, with rapid bathymetric variations, with multiple scattering regions, with interface waves at fluid/solid boundaries, and/or with shear waves in the bottom. In this presentation, we are adapting an existing three-dimensional spectral-finite-element code (SPECFEM3D, distributed and supported by the NSF funded program, Computational Infrastructure for Geodynamics), originally developed for global seismology, to bottom interaction problems in underwater acoustics. Numerical results from SPECFEM3D are compared with the range-dependent acoustic/elastic wave propagation model based on the parabolic equation (PE) method, for a 10 Hz acoustic pulse propagating in the deep ocean. The importance of out-of-plane scattering and bottom shear properties on resulting wave fields are investigated. [Work supported by ONR.]
Elastic coupled modes for range dependent propagation
Authors: Park Minkyu , Odom Robert I. , Frank Scott D. , Collis Jon M.
Published: September 2012

The seismo-acoustic field in a range dependent fluid-elastic environment can be computed from elastic coupled modes. Range dependence breaks the strict mathematical orthogonality of the modes causing energy to be exchanged among the elements of the modal spectrum. The original theory is from Maupin (1988). Range-dependent propagation effects are illustrated for a 2-D model including a seamount. The mode coupling is directly proportional to the bathymetric slope of the range dependence. While the range-dependent environmental model is composed of vertical slices, no iteration is required to solve for both the transmitted and the reflected seismo-acoustic field, which is found by solving a matrix Riccati equation for the modal reflection and transmission matrices. A particular feature of the elastic coupled modes is the automatic inclusion of the interface Scholte wave modes, which are absent from any all-fluid environmental propagation model. The excitation of the Scholte modes may be important for observed deep shadow zone acoustic arrivals. The coupled mode results will be compared to the results from an elastic parabolic equation (PE). [Work supported by ONR.]
Effects of tropical cyclones on underwater sound propagation
Authors: Newhall Arthur E. , Lin Ying-Tsong , Jan Sen , Lynch James F.
Published: September 2012

Environmental data collected near the continental shelf and the shelfbreak in the Southern East China Sea around Taiwan are utilized to study sound propagation effects of tropical cyclones (typhoons). These data were from the Conductivity-Temperature-Depth (CTD) profiling casts conducted during the Quantifying, Predicting, Exploiting (QPE) Uncertainty experiments in both 2008 and 2009. These CTD surveys provided observations for the normal physical oceanographic conditions in the area and, most importantly, the extreme conditions induced by a tropical cyclone Typhoon Morakot in the summer of 2009. Strong upwelling currents near the shelfbreak in the experiment area were observed after the typhoon past by, and the water-column stratification was changed. A sound speed variation of 10 m/s over 50 km in distance was measured in the upwelling area, and this can produce significant effects on sound propagation. Numerical models using parabolic-equation and ray tracing methods will be presented to demonstrate the underlying physics of the sound field variability. [Work supported by the Office of Naval Research.]
Using real sources to measure the acoustical behavior in rooms
Authors: Olson Bruce C.
Published: September 2012

It is common practice to use dodecahedron loudspeakers and balloons as the source for acoustical measurements. The drawback to this of course, is that it means an interruption to the normal performance in order to collect data in the presence of an audience. New techniques are now available for measurements using real acoustic sources without degrading the performance.
Applications of mobile computing devices in acoustics
Authors: Faber Benjamin
Published: September 2012

In the emerging post-PC era, more and more day-to-day computing tasks will be accomplished with mobile devices, such as the iPhone and iPad. Efforts to bring acoustical measurement and analysis tools to mobile devices have already begun. Mobile devices are not only smaller and lighter even than notebook computers, but they typically employ capacitive touchscreen technology, which enables an unprecedented level of interactivity between user and device. The media-centric nature of the current crop of mobile devices also makes them well-suited for acoustics-related applications. Several examples of hardware and software solutions for acoustical measurements with mobile devices will be presented and discussed.
Variations in standing-wave impedance tube design and the effect on the resulting data
Authors: Schnitta Bonnie , Enenstein Greg
Published: September 2012

Standing-wave impedance tubes are a practical and common method for estimating the acoustic absorption characteristics of a material. However, the standing-wave impedance tube test contains inherent variability with its design. Impedance tube standards allow for flexibility in tube material and tube dimensions. These variables in the design criteria of the impedance tube can produce disparities between measured absorption coefficients across different impedance tubes as well as when compared to well-established reverberation room data. Consequently, when designing a tube, in order to obtain accurate absorption values, it becomes necessary to optimize a tube, beyond merely preventing cross modes and allowing for a long enough tube to develop a pressure high and low. This study examines the effects of surface interactions in impedance tubes and how varying tube dimensions, most notably the width, will affect wave development.
Dhole (asiatic wild dog) and tapir vocalizations: Whistling in the jungle
Authors: Browning David , Scheifele Peter M.
Published: September 2012

Few land mammals whistle, and then, as with the marmots, usually just a quick alarm signal to visually alert. Yet in the jungle are found two distinctly different examples, both unique in their animal groups, which employ whistling as a means of communication in an acoustically noisy and visually very limited environment. Dholes, commonly referred to as whistling dogs, belong to a pack which typically breaks into smaller groups to hunt, primarily in the daytime. They whistle to keep in contact while trying to surround game hidden in the bush. In contrast, tapirs are solitary herbivores, grazing primarily at night. Both have found that a frequency sweep whistle is an effective means of communication either in the “screeching noise” daytime environment or the “rasping noise” insect dominated darkness.
Using bond graphs to model vocal production in túngara frogs
Authors: Kime Nicole M. , Ryan Michael J. , Wilson Preston S.
Published: September 2012

Male anurans (frogs and toads) produce species-specific advertisement calls. Conceptual models illustrate how anurans produce calls, but quantitative models of vocal production are rare. Consequently, how frogs produce complex or nonlinear signals, and how differences in morphology result in call differences among species, is in many cases unclear. Bond graphs are representations of dynamic physical systems that allow one to model both the hydraulic elements and mechanical oscillators of air-driven vocal production systems. They can be used to model either single components or interactions among components within vocal systems. This paper uses túngara frogs to show how bond graphs can be used to model vocal production. Túngara frogs produce complex calls that contain a species-specific “whine” and a facultative “chuck”. Their calls are frequency- and amplitude-modulated, and exhibit nonlinearities. A bond graph model of the túngara vocal folds produces sustained oscillations at a frequency typical of this frog. The complexity of the túngara frog call is explained by modulating the behavior of integrated components within its vocal production system. The bond graph modeling approach can be used to understand how the biomechanics of vocal production underlies the diversity of animal signals.
Use of social sounds by humpback whales (Megaptera novaeangliae) in the Western Antarctic Peninsula feeding grounds
Authors: Klein Michelle , Nowacek Douglas
Published: September 2012

Humpback whales (Megaptera novaeangliae) are renowned for the complex structured songs produced by males. A second, relatively understudied area of humpback acoustic communication concerns un-patterned sounds known as “social sounds,” produced by both males and females. This paper explores the use of non-song sounds by humpback whales on the Western Antarctic Peninsula feeding ground. To obtain high quality, close range recordings of humpback whale social sounds, digital acoustic tags (DTAGs) were placed on humpback whales exhibiting foraging behavior during the austral autumn of 2009 and 2010. Overall vocalization rates of two types of social sounds, “wops” and “grunts,” showed that there was not a significant diurnal pattern in call production, suggesting that perhaps these calls are not used exclusively for foraging on the feeding ground. These results enhance our understanding of this acoustically advanced species, and will also be useful in conservation and management efforts. The acoustic parameters of the calls that were identified can be used in the development of automatic detection algorithms, and the behavioral contexts during call production can assist in interpretation of passive acoustic monitoring research on humpback whales, and potentially other baleen whale species as well.
Is the ocean really getting louder?
Authors: Stocker Michael A. , Reuterdahl John T.
Published: September 2012

In 1975 Donald Ross indicated a long term trend of low frequency anthropogenic noise increase of 0.55dB/year between 1958 and 1975. This trend in ocean ambient noise levels due to expansion in global shipping has yielded an increase in the ambient noise floor of the ocean that is anywhere from 6dB to 12dB higher than what it was in 1958 (depending on location). What became known as the “Ross Prediction” did not incorporate other anthropogenic sources of noise such as navigation and communication signals, noise from offshore fossil fuel exploration and extraction, and the noises from other marine industrial enterprises. There is a concern that the increase in ambient noise is masking biologically significant sounds, although the evidence for this is still scarce and somewhat speculative. Meanwhile perhaps 90 percent of the biomass of complex vertebrates has been removed from the ocean since 1850 due to industrialized whaling and fishing operations. This paper examines whether the ocean ambient noise floor may have been significantly higher in 1800 than in the 1958 baseline year of the “Ross Prediction,” and speculates that ambient noise levels may be less of a biological aggravator than the particular characteristics of a noise source.
The problem of sound propagation through the fluctuating ocean and the interplay between ocean acoustics and physical oceanography
Authors: Colosi John A.
Published: September 2012

While the ocean provides a particularly amenable environment for acoustic remote sensing, navigation, and communication, the confounding effects of fluctuations have bedeviled ocean acousticians for decades. To attack this problem the communities of ocean acoustics and physical oceanography became new bedfellows, with the development of ocean acoustic tomography and path-integral/moment-transport theories driven by internal-wave models being major accomplishments for describing low and high-frequency fluctuations. With the advent of relatively inexpensive oceanographic mooring equipment, experiments in the last decades have deployed nearly as many oceanographic instruments as acoustic instruments, thus leading to fundamental discoveries concerning internal tides, solitons, random internal waves and spicy thermohaline structure. These measurements are in turn providing strong constraints on acoustic fluctuation theories and Monte Carlo simulations used to interpret acoustic observations. This presentation will give a review of what has been learned about ocean sound-speed structure and how this information can be better integrated into acoustic fluctuations calculations. It will be shown that acoustic fluctuation theory has developed to the point in which reasonable inversions for internal-wave parameters are now possible.
Acoustic waves in characterizing biological materials: From molecules to soft tissue and bone. A review
Authors: Sarvazyan Armen
Published: September 2012

Various types of acoustic waves: bulk compressional, shear, surface, and numerous modes of guided waves, are used for characterizing structure and composition of biological media. Bulk waves can be used to assess the composition of biological fluids, such as blood, plasma, milk, urine, stomach juice, and biopolymers in solutions and both bulk and shear waves can be used when characterizing soft tissues. While the assessment of skin is primarily performed using surface waves; various modes of guided waves are used to characterize bone and blood vessels. Historically, the problem of acoustic characterization of tissue properties became a hot topic in the early 1970s in conjunction with the emergence and great success of ultrasonography. The idea of remotely assessing the properties of tissue in a region of interest, as seen on an ultrasonic image, attracted the attention of numerous researchers, but until recently and despite intensive studies and great expectations, not many examples of acoustic characterization of tissue properties made a significant impact. Only in the last decade, this idea started to bring first fruits and is being implemented in commercial devices which are using shear elasticity modulus of tissue as a characterization parameter.
A comparison of mechanical wave measurement techniques to quantify soft tissue viscoelasticity up to 8 kHz: A phantom study of shear, Rayleigh and Lamb waves
Authors: Yasar Temel K. , Royston Thomas J. , Magin Richard L.
Published: September 2012

Over the past few decades different techniques based on measurement of mechanical wave motion have been developed for noninvasive quantitative measurement and mapping of soft biological tissue shear viscoelastic properties. In this talk we compare two different measurement approaches, three wave types, and several models for quantifying material viscoelasticity up to 8 kHz for a soft tissue phantom material known as ecoflex. Surface waves and Lamb waves are measured using scanning laser Doppler vibrometry (SLDV). Lamb waves and shear waves are measured using magnetic resonance elastography (MRE). Different linear models of viscoelasticity, including Voigt, Maxwell, more generalized and fractional order types, are optimized and compared based on the different experiments. Challenges and limitations of the different techniques and model types, and their adaptation to more complex biological tissue and anatomical structures are discussed. [Work supported by NIH Grants EB012142 and EB007537.]