bluuebunny/crossref_metadata_2025 huggingface dataset:
Work‐based assessment: qualitative perspectives of novice nutrition and dietetics educators
Authors: Palermo C. , Beck E. J. , Chung A. , Ash S. , Capra S. , Truby H. , Jolly B.
Published: October 2013

Background

The assessment of competence for health professionals including nutrition and dietetics professionals in work‐based settings is challenging. The present study aimed to explore the experiences of educators involved in the assessment of nutrition and dietetics students in the practice setting and to identify barriers and enablers to effective assessment.

Methods

A qualitative research approach using in‐depth interviews was employed with a convenience sample of inexperienced dietitian assessors. Interviews explored assessment practices and challenges. Data were analysed using a thematic approach within a phenomenological framework. Twelve relatively inexperienced practice educators were purposefully sampled to take part in the present study.

Results

Three themes emerged from these data. (i) Student learning and thus assessment is hindered by a number of barriers, including workload demands and case‐mix. Some workplaces are challenged to provide appropriate learning opportunities and environment. Adequate support for placement educators from the university, managers and their peers and planning are enablers to effective assessment. (ii) The role of the assessor and their relationship with students impacts on competence assessment. (iii) There is a lack of clarity in the tasks and responsibilities of competency‐based assessment.

Conclusions

The present study provides perspectives on barriers and enablers to effective assessment. It highlights the importance of reflective practice and feedback in assessment practices that are synonymous with evidence from other disciplines, which can be used to better support a work‐based competency assessment of student performance.
The Green Economy Mirage?
Authors: Chao Chia‐Wei , Ma Hwong‐wen , Heijungs Reinout
Published: October 2013

Taiwan is attempting to implement the concept of a green economy through a Low Carbon Growth Plan (LCGP). However, the existing decision support tools for this measure have three key limitations: ignorance regarding the open economy; a lack of life cycle thinking; and limited categories of environmental impact. This study integrates environmentally extended, multi‐region input‐output analysis and hybrid life cycle assessment to quantify the potential environmental impact of the industrial activities and energy structure in Taiwan in 2020. Two novel indicators, environmental debts and loans, are also applied to identify the geographical shifting effects and tie environmental responsibility to the discussion.

The results of this study reveal that under the existing LCGP, relative decoupling will be attained, but no significant environmental cobenefits other than those affecting climate change can be gained. Moreover, the current emission pledges cannot be fulfilled. The presence of increased environmental debt ratios reveals the geographical shifting effect of the LCGP. The main driver of the expansion of the environmental footprint can be attributed to the export of electronic components and products, which are not included in the agenda of policy discussions. As a result, three crucial policies are suggested to modify the existing LCGP: the implementation of a higher energy efficiency improvement target; rethinking the constraints on the electronics industry; and the development of a mechanism to include environmental issues in free trade agreement negotiations. With these changes, the realization of the current emission pledge and a green economy could be possible.
A FIXED‐ b TEST FOR A BREAK IN LEVEL AT AN UNKNOWN TIME UNDER FRACTIONAL INTEGRATION
Authors: Iacone Fabrizio , Leybourne Stephen J. , Robert Taylor A. M.
Published: October 2013

In this paper, we propose a test for a break in the level of a fractionally integrated process when the timing of the putative break is not known. This testing problem has received considerable attention in the literature in the case where the time series is weakly autocorrelated. Less attention has been given to the case where the underlying time series is allowed to be fractionally integrated. Here, valid testing can only be performed if the limiting null distribution of the level break test statistic is well defined for all values of the fractional integration exponent considered. However, conventional sup‐Wald type tests diverge when the data are strongly autocorrelated. We show that a sup‐Wald statistic, which is standardized using a non‐parametric kernel‐based long‐run variance estimator, does possess a well‐defined limit distribution, depending only on the fractional integration parameter, provided the recently developed fixed‐b asymptotic framework is applied. We give the appropriate asymptotic critical values for this sup‐Wald statistic and show that it has good finite sample size and power properties.
Apathy is more severe in vascular than amnestic mild cognitive impairment in a community: The Kurihara Project
Authors: Nakamura Kei , Kasai Mari , Ouchi Yoshitaka , Nakatsuka Masahiro , Tanaka Naofumi , Kato Yuriko , Nakai Megumi , Meguro Kenichi
Published: October 2013

Aim: 

The aim of this study was to estimate the prevalence of apathy, and to compare vascular mild cognitive impairment (vMCI), amnestic MCI (amMCI), and other type using Clinical Assessment for Spontaneity (CAS).

Methods: 

Agreement to take part in the study was obtained from 590 community dwellers, aged ≥75 years living in Kurihara, Japan. Of the 590 subjects, 221 had a clinical dementia rating (CDR) of 0 (normal); 295 had CDR 0.5 (mild cognitive impairment; MCI); and 74 had CDR 1+ (dementia). The CDR 0.5 subjects were divided into three groups: 55 with vMCI (Erkinjuntti et al. criteria), 91 with amMCI and 149 with other type. To evaluate the various aspects of apathy, we used the three CAS subscales: clinical interview (CAS1), self‐evaluation (CAS2), and caregiver assessment (CAS3). Three analyses were then performed to determine: (i) the validity of CAS; (ii) the prevalence rate of apathy in CDR 0 versus CDR 0.5 versus CDR 1+; and (iii) the prevalence rate of apathy in normal versus vMCI versus amMCI versus other type.

Results: 

CAS was validated with the Apathy Evaluation Scale. There were significant differences among the three CDR groups in CAS1, CAS2 and CAS3 (P < 0.001). The prevalence rate of apathy in each CAS in the CDR 1+ group was higher than the CDR 0.5 group, which was higher than the CDR 0 group. There was a significant difference in CAS3 score between the four groups (the normal and the three subgroups; P < 0.001). Apathy in vMCI was more severe than in the other three groups (P < 0.05) on CAS3 score.

Conclusions: 

vMCI subjects have more severe apathy compared with amMCI subjects on caregiver assessment.
Predicting new product success with prediction markets in online communities
Authors: Matzler Kurt , Grabher Christopher , Huber Jürgen , Füller Johann
Published: October 2013

The prediction of new product success is still a challenging task. Traditional market research tools are expensive, time consuming, and error prone. Prediction markets have been introduced as a viable alternative. Utilizing inputs from various participants in game‐like environments, they have been shown to produce accurate results by combining dispersed knowledge via market‐based aggregation mechanisms. While most previous studies use employees or experts as a sample, we test whether online consumer communities can be used to predict the sale of new skis via prediction markets. Sixty‐two users took part in the study. The prediction market was open for 12 days before the main skiing season 2010/2011 began. The outcomes of the prediction markets were compared with the actual sales numbers provided by the ski producers. The mean average errors were between 2.74% and 9.09% in the four markets. Overall, it can be concluded that the prediction markets based on consumer communities produce accurate results.
The role of alloantibodies against human platelet antigen‐15 in multiply platelet transfused patients
Authors: Matsuhashi Mika , Tsuno Nelson H. , Sone Shinji , Mishima Yuko , Nagura Yutaka , Watanabe‐Okochi Naoko , Ikeda Toshiyuki , Kashiwase Koichi , Fukuda Shinya , Iriyama Takayuki , Hyodo Hironobu , Yamashita Takahiro , Kamei Yoshimasa , Arai Shunya , Minami Mutsuhiko , Fujii Tomoyuku , Kurokawa Mineo , Tozuka Minoru , Takahashi Koki , Santoso Sentot
Published: October 2013

Background

Several studies have documented the role of antibodies against human platelet (PLT) antigen (HPA)‐15 in alloimmune‐mediated thrombocytopenia including neonatal alloimmune thrombocytopenia, PLT transfusion refractoriness (PTR), and posttransfusion purpura in Caucasian persons. However, the relevance of anti‐HPA‐15 in PTR among the Japanese population is still unclear.

Study Design and Methods

The sera of 305 multiply PLT transfused (MPT) patients, previously investigated for the presence of human leukocyte antigen (HLA) and HPA antibodies by mixed passive hemagglutination, were reexamined for the presence of HPA‐15 alloantibodies, using the monoclonal antibody–specific immobilization of PLT antigens (MAIPA) technique.

Results

Among the 305 MPT samples, antibodies against HPA‐15 alloantigen was detected in seven (2.3%), two (0.66%) being anti‐HPA‐15a and five (1.64%) being anti‐HPA‐15b. Additionally, one case of CD109 panreactive antibody was found (0.33%). Among them, one aplastic anemia patient with blood group O developed multispecific anti‐HLA and anti‐HPA‐15b alloantibody after MPTs. However, transfusion with HLA‐matched PLTs of blood group AB did not result in adequate PLT count increment. Analysis of the possible influence of immune anti‐A and anti‐B by the MAIPA assay resulted negative, indicating that anti‐HPA‐15b is responsible for the refractory state in this patient.

Conclusion

In this study, we found alloimmunization against HPA‐15a and ‐15b in Japanese populations and demonstrated the relevance of these antibodies in a patient with PTR.
Passive Vibration Control of Structures Subjected to Random Ground Excitation Utilizing Sloshing in Rectangular Tanks
Authors: Ikeda Takashi , Ibrahim Raouf A.
Published: October 2013

Passive vibration control of an elastic structure carrying a rectangular tank, partially filled with liquid, is investigated when the structure is subjected to horizontal, narrowband, random ground excitation. The modal equations of motion for liquid sloshing are derived using Galerkin's method, considering the nonlinearity of sloshing. The system response statistics including mean square values, correlation coefficients, and probability density functions (PDFs) are numerically estimated from the time histories using the Monte Carlo simulation when the natural frequency of the structure is close to that of liquid sloshing. The influences of the excitation center frequency, its bandwidth, and the liquid level on the system responses are examined. As a result, it is found that the mean square responses of the structure decrease when the center frequency is close to the natural frequency of the structure due to sloshing. Tuned liquid dampers (TLDs) are found to be most effective for comparatively low liquid levels.
One year of background underwater sound levels in Haro Strait, Puget Sound
Authors: Veirs Val , Veirs Scott
Published: October 2013

Haro Strait, on the west side of San Juan Island, WA, is the home range of the Southern Resident orca whales, a major shipping lane to and from Canada, and a center of private and commercial boating, especially in the summer. Four ITC hydrophones in a near-shore fixed array are used here to localize the underwater vocalizations of Southern Resident orca whales. The system operates 24 hours a day and has a frequency response of 100 Hz 10 kHz. Background sound levels are automatically characterized by half-hour reports that include: statistics and graphics based on mean sound levels (2-min running arithmetic mean pressure); a histogram of mean sound levels binned by frequency; and 2-s sound samples from maximum background events. Sound levels range from ∼90 dB re 1 microPa (quiet conditions) to ∼130 dB re 1 microPa when loud commercial ships are passing in the nearby shipping lane or speedboats are passing close to the hydrophone array. Complete results for one year of continuous monitoring will be presented, segmented by time (season, day of the week, hour in the day), frequency spectrum and dominant noise source class. [Work supported by 35 undergraduate researchers and the Colorado College.]
Design aspects of the five string banjo
Authors: Rae James , Rossing Thomas
Published: October 2013

The five string banjo is a stringed instrument that uses a drum head (membrane) to radiate sound. The strings couple to the head through a moveable bridge. Many have a removable resonator whose spacing from the main part of the banjo is adjustable to allow tuning of the internal air cavity. Holographic interferometry demonstrates vibrational modes of the head that have a strong dependence on head tension. Driving point accelerance measurements demonstrate that the ability of the bridge to be vibrated depends on the mass and stiffness of the materials used in its construction. Peak accelerances usually occur between 1800–2000 Hz. Power spectra measurements of the sound show that 99% of the sound is in a frequency range of 147–5200 Hz. Two substantial formants are seen in the power spectra. The first and largest occurs in about the 400–1800 Hz range, the same frequency range where the most substantial head modes are found. The second is from 2000–4000 Hz, a range where the series combination of bridge and head show increasing accelerances by driving point measurements. Measurements of the transient response following a pluck quantify the frequency content of the rising and falling phase.
Estimating cochlear-filter shapes, temporal-window width and compression from tone-sweep detection in spectral and temporal noise gaps
Authors: Hilkhuysen Gaston , Houtgast Tammo , Lyzenga Johannes
Published: October 2013

A test, designed for naive listeners, measured tone-sweep detection in noise with either spectral or temporal gaps. For normal-hearing (NH) listeners, detections in spectral gaps depended on level, which can be explained from Outer-Hair-Cell (OHC) activity. At low levels, OHC activity increased frequency-selectivity by amplifying the signal in the spectral gap, improving the signal-to-noise ratio (SNR). Relative to the broad passive cochlear filter, OHC activity decreased with rising signal levels. In consequence, SNRs decreased and detection deteriorated. Similarly, decreasing OHC activity may explain the observed level dependence of detection thresholds in temporal gaps. At low and high intensities, signal and noise were equally amplified. Detection was best at intermediate levels when the low-level signal in the temporal gap was amplified more than the high-level noise. All effects are modeled using a one-parameter time window with decaying-exponential shape preceded by a simplified dual-resonance non-linear (DRNL) filter. The filter contains two parallel, one-parameter, Rounded Exponential filters: a broad filter representing passive cochlear filtering and a narrow one, combined with a level-dependent amplifier, representing OHC activity. From estimated filter and time-window widths and OHC amplification, compression curves are derived. Additionally, results for hearing-impaired listeners will be presented.
Effect of aspiration noise and spectral slope on perceived breathiness in vowels
Authors: Shrivastav Rahul , Pinero Maria
Published: October 2013

Breathy voice quality is frequently encountered in both normal and dysphonic voices. Breathiness has been associated with an increase in the intensity of aspiration noise as well as changes in spectral slope [Childers and Ahn, 1995; Fischer-Jorgenson, 1967; Huffman, 1987; Klatt and Klatt, 1990]. Shrivastav and Sapienza (2003) found that subjective ratings of breathiness obtained from a group of listeners were highly correlated with certain measures calculated from the auditory spectrum of the vocal acoustic signal. One of these measures, the partial loudness of the harmonic energy, was related to both the aspiration noise and the spectral slope of the voices. In the present experiment, 10 young adult listeners with normal hearing were presented with voices that varied systematically in terms of their aspiration noise and spectral slope. The stimuli, five male and five female voices, were generated using the Klatt synthesizer and were modeled after naturally occurring voices. Listeners rated breathiness for each of these stimuli using a 7-point rating scale. Results show the relative contribution of spectral slope and aspiration noise to the perception of breathiness.
Salmon enumeration in the Fraser River with the dual-frequency identification sonar (DIDSON) acoustic imaging system
Authors: Holmes John A. , Cronkite George , Enzenhofer Hermann J.
Published: October 2013

Reliable data on the number of salmon entering tributaries of the Fraser River to spawn (escapement) is needed for Pacific salmon management. Existing escapement techniques are costly and the number of populations requiring assessments has risen because of stock rebuilding efforts. The efficacy of a DIDSON acoustic imaging system for salmon stock assessment was investigated. Sixteen potential sites within the Fraser watershed were surveyed and based on channel morphology, bottom morphology, flow pattern, fish behavior and location relative to spawning grounds, ten sites in six rivers meet the needs of fisheries managers and the DIDSON system for escapement estimates. Fish count data from the DIDSON were compared to data from a counting fence (used as a standard) using regression techniques, resulting in relationships with slopes ranging from 0.98 to 1.02. The precison of DIDSON counts >50 (measured by CV) among three readers was 1.7%. This work supports the conclusion that the DIDSON system can deliver escapement estimates whose accuracy, precision and scientific defensibility is consistent with or better than existing escapment techniques and at a lower operating cost to assessment programs. [Work supported by the Southern Boundary Restoration and Enhancement Fund of the Pacific Salmon Commission.]
Voices of athletes reveal only modest acoustic correlates of stature
Authors: Owren Michael J. , Anderson John D.
Published: October 2013

Recent studies of acoustic cues to body-size in nonhuman primate and human vocalizations have produced results varying from very strong relationships between formant frequencies and length/weight in rhesus monkeys to weak correlations between formants and stature in humans. The current work attempted to address these discrepancies by compiling a database of naturally occurring speech with a large number of vocalizers of maximally varying size. To that end, fundamental frequency (F0) and formant frequencies were measured in both running speech and filled pauses (i.e., ‘‘ah’’ and ‘‘um’’) produced by male athletes during televised same-day interviews. Multiple-regression analysis of data from 100 male athletes showed that these acoustic measures accounted for at most 17% of variance in height over a 37-cm range. Analyses of filled speech pauses produced by a subset of 48 athletes could account for up to 36%. These outcomes fall within the range of previously reported outcomes, indicating that while speech acoustics are correlated with body-size in human adult males, the cues provided are quite modest.
Application of barrier in industrial noise control
Authors: Chui Jonathan , Ma Yong , Hertil Salem
Published: October 2013

Noise barriers have been widely used in environmental noise control, such as traffic and railway noise. Actually they are also cost-effective mitigation measures in industrial noise control. In this paper, the applications of noise barrier in power plant are introduced. Types of barrier and barrier materials are briefly summarized and compared. A case study of noise barrier implement in a 50 MW power plant is presented. The plant is a natural gas-fired simple-cycle peaking facility, and consists of two opposed gas combustion turbine directly connected through a coupling to a single generator. Some residences are located around the facility. A noise barrier wall was designed and installed surrounding the facility to control the noise impact of the plant on the residences. The acoustic modeling software Cadna/A was used to predict the noise insertion loss of the barrier. The prediction results were also compared with the site measurements.
Modeling auditory localization in the low-frequency range
Authors: Braasch Jonas , Martens William L. , Woszczyk Wieslaw
Published: October 2013

Binaural recordings were made for subwoofer reproduction of octave-band noise bursts at 31.5-Hz, 63-Hz and 125-Hz center frequencies, and these low-frequency responses were analyzed using a binaural model simulating human perception. As expected, the interaural level differences remained nearly constant for different sound source positions within this low-frequency range. On the basis of interaural time differences, however, the model was able to predict the left/right position of the sound source on the interaural axis. In order to visualize the cross-correlation peak at low frequencies in the ITD range from −1.5 ms to +1.5 ms, the cross-correlation functions were decompressed by taking them to the power of 40. At these low-frequencies, the range of phase difference does not vary much with different sound positions although the ITDs are on the same order as for higher frequencies (≊−1.0 ms to 1.0 ms), but the human ability to resolve very small phase differences already has been shown in previous investigations. The predictions of the model simulation were verified in a listening test. The repetition of the experiment in a second more reverberant space showed similar reductions in performance for both the human listeners and the model. [Work supported by VRQ.]
Acoustic and social design of schools—ways to improve the school listening environment
Authors: Hagen Mechthild
Published: October 2013

Results of noise research indicate that communication, and as a result, teaching, learning and the social atmosphere are impeded by noise in schools. The development of strategies to reduce noise levels has often not been effective. A more promising approach seems to be to pro-actively support the ability to listen and to understand. The presentation describes the approach to an acoustic and social school design developed and explored within the project ‘‘GanzOhrSein’’ by the Education Department of the Ludwig-Maximilians-University of Munich. The scope includes an analysis of the current ‘‘school soundscape,’’ an introduction to the concept of the project to improve individual listening abilities and the conditions for listening, as well as practical examples and relevant research results. We conclude that an acoustic school design should combine acoustic changes in classrooms with educational activities to support listening at schools and thus contribute to improving individual learning conditions and to reducing stress on both pupils and teachers.
Geoacoustic inversion for single paths of Haro Strait data
Authors: Tolstoy A.
Published: October 2013

This presentation will discuss efforts to date for the geoacoustic inversion of selected, single, Haro Strait Source-Receiver (SR) paths. The parameters emphasized will include water depth, linear sound-speed profiles, and the range between SR. The path will assume 3 segments: one segment for the region at S, one for the region at R, and one for an average region in between. The inversions will operate using the SUB-RIGS method which is based on multiple frequencies where higher frequencies are most sensitive to surficial geoacoustic properties while the lower frequencies are most sensitive to the deeper properties. Some paths have already been successfully inverted by earlier research efforts (Chapman et al.). This paper will demonstrate efforts on some of those paths as well as on other, more problematic SR paths.
Induced loudness reduction: A review
Authors: Scharf Bertram , Wagner Eva , Nieder Bärbel
Published: October 2013

Under appropriate stimulus conditions, a tone may decline in loudness the equivalent of 10 dB and more when preceded by a stronger tone. This induced loudness reduction or ILR was uncovered, indirectly, in a large number of studies by L. E. Marks and his associates [e.g. Marks, J. Exp Psychol HPP 20, 382–396 (1994)]. Those studies seemed to suggest that ILR required that tones be presented at two widely separated frequencies over a relatively large range of SPLs. Although part of the measured loudness changes seemed to stem from response biases, recent studies show unequivocally that the reduction in loudness is mostly sensory and that tones need be presented at only a single frequency and at two levels some 10 to 20 dB apart. The present paper puts together what is known about the dependence of ILR on signal frequency, level, duration, temporal relations, and hearing loss. The role of ILR in various other psychoacoustical phenomena such as induced loudness adaptation and loudness enhancement is reviewed. Much of this knowledge was obtained in direct and indirect collaboration with So/ren Buus. [Work supported by NIH/NIDCD Grant No. R01 DC 02241.]
An ultrasonic investigation of retracted consonants in St’at’imcets (Lillooet Salish)
Authors: Namdaran Nahal
Published: October 2013

Tongue retraction is rare in native languages of North America. Previous literature on St’at’imcets (also known as Lillooet) has left unanswered the question of how retracted consonants (uvulars, a pharyngeal, and a subset of retracted coronals) are articulated, and whether they in fact involve tongue retraction. Based on perceptual and acoustic data, previous descriptions differ with respect to the involvement of the tongue dorsum and tongue root in the articulation of St’at’imcets retracted consonants, particularly with the orthographic ‘‘g,’’ disputed to be either a uvular or pharyngeal approximant [Shahin, 1997; van Eijk, 1997]. Articulatory data of retracted and nonretracted consonants were collected from 4 St’at’imcets speakers via a portable ultrasound machine. Results indicate a significant difference in tongue root, dorsum, and body position for retracted versus nonretracted consonants, with the former possessing more tongue root and dorsum backing and tongue body lowering than the latter. Furthermore, results show ‘‘g’’ to be articulated similarly to the uvular consonant, with the tongue dorsum moving towards the posterior uvula/upper pharyngeal region of the vocal tract. These results provide direct evidence for the articulatory makeup of St’at’imcets retracted consonants and shed light on St’at’imcets retraction effects and phonological harmony processes. [Work supported by SSHRC.]
Stochastic filtering
Authors: Havelock David I.
Published: October 2013

Digital filters convolve a signal with an impulse response. This is equivalent to computing a weighted sum of delayed versions of the signal, with the signal versions indexed by their sample-delay and the weights given by the filter impulse response. This talk explores a different approach to filtering. Rather than computing a weighted sum of data values, the stochastic filter uses a sequence of random indices to select output data values from delayed versions of the signal. No summation is done. The probability distribution of the random indices is made identical to the normalized modulus of the impulse response of the corresponding conventional filter. For indices with negative weights, data values are negated. For a random index sequence s(n) the stochastic filter output is simply y(n)=±x(n−s(n)). The output of such a stochastic filter is noisy but it is equal in the mean to the output of the corresponding conventional filter. If the sequence of random indices is identically and independently distributed then the noise is spectrally white. Such a filter can be useful for estimating spectral parameters with minimal computation. The principle is illustrated by an application to double-talk detection for telephones.
Bayesian sampling with applications to energy decay analysis in acoustically coupled spaces
Authors: Jasa Tomislav , Xiang Ning
Published: October 2013

Bayesian inference comprises of parameter estimation and model selection/comparison. A common approach to solving both of these problems has been to use statistical sampling techniques that are inherently non-Bayesian. This paper presents new Bayesian sampling method that solves both problems by changing the focus of Bayesian inference to the model selection problem first. In the papers [N. Xiang and P. M. Goggins, J. Acoust. Soc. Am. 110, 1415–1424 (2001); 113, 2685–2697 (2003)], the authors developed a model for the decay times and decay modes of acoustically coupled rooms in terms of measured Schroeder’s decay functions. This paper shows how the Bayesian sampling method can be used to evaluate the ‘‘Bayesian evidence’’ term used in model selection as well as determining the decay times along with error estimates.
Attenuation in sand sediments due to scattering from force chains
Authors: Hefner Brian T. , Jackson Darrell R.
Published: October 2013

The stresses in a granular media, such as an ocean sediment, are known to be heterogeneous and tend to form chains along which the stresses are particularly high. Because the elastic properties of a granular medium depend nonlinearly on the static forces between the grains, these force chains should induce inhomogeneities in the frame moduli. The correlation lengths of these inhomogeneities have been observed to be on the order of only a few grain diameters and as a consequence have not been thought to produce any significant scattering of acoustic energy. However, for high frequency sound in a saturated granular medium, these inhomogeneities should be on the order of the slow compressional wave. As a consequence, as the fast wave propagates through the sediment, it may scatter energy into the slow wave which is then rapidly attenuated. This scattering process may account for the deviation of the measured attenuation from the predictions of Biot theory that have been observed in ocean and laboratory sediments at high frequencies. We present a model of sound propagation through sand sediments that incorporates this loss mechanism and compare the results of this model to recent measurements. [Work supported by ONR.]
Dependence of modal attenuation coefficient frequency variation on upper sediment attenuation
Authors: Saintval Wendy , Siegmann William L. , Carey William M. , Pierce Allan D. , Lynch James F.
Published: October 2013

The range-averaged transmission loss increase in shallow water propagation depends critically on the intrinsic attenuation of the upper sediment. The attenuation coefficients of low-frequency (<1 kHz) propagating modes determine the frequency dependence. Ingenito [J. Acoust. Soc. Am. 53, 858–863 (1973)] showed with measurements and theory that while individual mode attenuation coefficients decrease with frequency f, the sediment attenuation coefficient increases proportional to f1.75. When results from many other shallow-water transmission experiments (broadband and narrowband) over sandy-silty sediments are compared to numerical calculations, it is found that a nonlinear-frequency dependent attenuation is required with an exponent between 1.5 and 2. The question considered here is how the intrinsic upper-sediment attenuation produces such behavior. A recent simplification of the Biot model [A. D. Pierce et al., J. Acoust. Soc. Am. 114, 2345 (2003)] has a power-law exponent of two. With this frequency-dependent bottom attenuation, a two-layer Pekeris waveguide yields modal attenuation coefficients that decrease with frequency as observed by Ingenito. However, a depth-dependent attenuation profile or a third near-surface layer with requisite properties can reverse this behavior. This suggests why higher-frequency numerical computations may require nonlinear frequency-dependent sediment profiles to calculate sound transmission accurately. [Work partially supported by ONR.]
Aurally-adequate time-frequency analysis for scattered sound in auditoria
Authors: Norris Molly K. , Xiang Ning , Kleiner Mendel
Published: October 2013

The goal of this work was to apply an aurally-adequate time-frequency analysis technique to the analysis of sound scattering effects in auditoria. Time-frequency representations were developed as a motivated effort that takes into account binaural hearing, with a specific implementation of interaural cross-correlation process. A model of the human auditory system was implemented in the MATLAB platform based on two previous models [A. Härmä and K. Palomäki, HUTear, Espoo, Finland; and M. A. Akeroyd, A. Binaural Cross-correlogram Toolbox for MATLAB (2001), University of Sussex, Brighton]. These stages include proper frequency selectivity, the conversion of the mechanical motion of the basilar membrane to neural impulses, and binaural hearing effects. The model was then used in the analysis of room impulse responses with varying scattering characteristics. This paper discusses the analysis results using simulated and measured room impulse responses. [Work supported by the Frank H. and Eva B. Buck Foundation.]
Extension of infinite elements to explicit dynamic and eigenanalysis of submerged structures
Authors: Cipolla Jeffrey
Published: October 2013

Infinite elements are distinct from alternative methods for exterior problems in that, like a finite element, they describe a small sub-region of the problem domain, and use locally supported shape functions to derive a method of weighted residuals statement thereon. Until recently, transient analyses using explicit time-integration methods, and eigenanalysis, were not possible using infinite elements. A formulation of acoustic infinite element compatible with implicit dynamics, time-harmonic acoustics, far-field extrapolation, explicit dynamics, and eigenanalysis is described. First steps in the development are the adoption of a basis corresponding to spherical radiating harmonics, the Bettess geometric map, and the Astley-Leis weighted residual formulation. A modified means to compute the element integrals, and a modification of the spherical harmonic basis, improve numerical conditioning of the element and stability of the formulation. The trivial frequency dependence of the Astley-Leis formulation, critical for its application to transient problems, also enables a formulation for eigenanalysis, which will be discussed. Finally, a splitting of the element operator into tangential mass- and stiffness-like terms enables a partial lumping of the element, and compatibility with explicit time integration schemes. Importantly, this splitting preserves the essential radiation mode accuracy of the formulation. Some computational examples are shown.
Renovating Teatro alla Scala Milano for the 21st century, Part II
Authors: Arau Higini
Published: October 2013

The acoustic phase of La Scala renovation began in September 2002, after the main stalls and other sections of the theater were demolished. This assignment was twofold: (a) design of the auxiliary building with architect Mario Botta, and more importantly, (b) collaboration with architect Elisabetta Fabbri in restoration of the auditorium through acoustic analyses of proposed solutions. Only one set of acoustical measurements was known to be taken before demolition; and reliance had to be placed on hearsay from audience members. The author used his own computer program that included some of the salient features of other programs such as Odeon, Epidaure, Raynoise, etc. but avoided their pitfalls. This program was the only one that correctly predicted the known RT of the auditorium through the use of H. Arau Purchades formula [Arau, H., 1988. Acustica. Hirzel Verlag 65(4), 163–180] and the authors dimension theory [Arau, H. 1997. Variation of the reverberation time of places of public assembly. Building Acoustics 4(2).]. A new floor was designed to provide sufficient vibration transmission to the audience, actuating as a radiation box installed to direct sound vertically. Music Director Ricardo Muti pronounced the acoustical results as being excellent.
Historical preservation of acoustics at Spelman College, Atlanta
Authors: Rosenberg Carl , Markham Benjamin , Black Barbara Kovacs
Published: October 2013

In 1926, Spelman College in Atlanta dedicated its new Sisters Chapel, named after Laura Spelman Rockefeller and Lucy Maria Spelman, mother and aunt of John D. Rockefeller, Jr., the major donor. The Chapel has around 1000 seats and serves as a major venue for a myriad of programs, ceremonies, concerts, and student activities. In 2003, architects Surber Barber Choate and Hertlein were commissioned to renovate and rehabilitate the chapel with air-conditioning, new toilet facilities, new roof, enlarged balcony, and new sound system. The neo-classic pseudo Georgian basilica has a barrel vault running the length of the room. Sometime in the past, probably around 1950, the chapel ceiling was covered with a sound absorbing acoustic tile, presumably to rectify a focusing problem from the curved ceiling. With computer modeling, Acentech reconstructed the apparent acoustical problems and used this information to guide a renovation. The goal was to recapture the visual aspects of the original design, enhance the reverberation for the renovated Holtkamp organ and singing, and at the same time avoid any focusing problems for which the acoustic tile was presumably added. The project included mechanical system noise and vibration control and a new highly directional sound system.
MRI system vibration and noise considerations in hospital design
Authors: Ungar Eric E. , Zapfe Jeffrey A.
Published: October 2013

Magnetic Resonance Imaging (MRI) systems are increasingly being located on above-grade floors of hospital buildings. The floor structures that support these systems need to provide vibration environments that satisfy the system’s criteria, and airborne and structure-borne transmission of noise to neighboring areas needs to be taken into account in order to provide acceptable acoustical environments in these spaces. The fundamental operating principles of MRI systems are reviewed in relation to the systems’ susceptibility to vibration and to their sound producing mechanisms. Vibration criteria for some widely used systems are discussed and spectra of airborne and structure-borne noise are illustrated. Means for vibration control and for the attenuation of structurally transmitted sound are delineated, together with architectural considerations for limiting noise transmission to spaces adjacent to MRI suites.
Sound sources and propagation
Authors: Burkhard Mahlon
Published: October 2013

From July 1945 through May 1950, the Acoustics Laboratory of the Department of Physics at Pennsylvania State [College] University conducted ‘‘investigations concerning the production and propagation of sound, both sonic and ultrasonic, in the lower atomosphere, through the ground, and in other media.’’ Wesley L. Nyborg was a key member of the group of 53 researchers employed in the program at some-time during the period. A sound source used extensively in the study of ultrasonic propagation in the atmosphere was a small whistle. ‘‘Edge tones’’ generated by a jet of air impinging on a narrow object are phenomena critical to the operation of these whistles as well as organ pipes and many sounds associated with fluid flow. Because the sound can be controlled and levels can be quite high, one proposed application was as a source for radiating small quantities of liquids with ultrasound. In addition to developing a physical understanding of this sound generation mechanism, Nyborg participated in studies and analysis of the influence of micrometeorology on propagation of high frequency sound in the atmosphere.
Spatial release from informational masking along the front-back dimension
Authors: Aaronson Neil L. , Rakerd Brad , Hartmann William M.
Published: October 2013

When two independent speech samples are presented together from a single location in front of the listener, one will mask the other. The amount of masking can be reduced by presenting a repeated masker from a different location off to the side and shifting it slightly forward (+) or backward (−) in time compared to the masker in front. New experiments, using the coordinate response measure technique with a two-female-talker masker and a female target, show that masking release can also be obtained when the target and masker are in front and the repeated masker is directly in back. Release is seen for both forward and backward time shifts, ranging from −32 to 32 ms. The amount of release is somewhat more than half that obtained when the repeated masker is off to the side. Release from masking can also be seen when the repeated masker comes from a location directly above the target and masker in front, but only for a single value of time shift, namely ±2 ms. It is concluded that both spatial and spectral cues mediate release from informational masking in the front-back dimension. [Work supported by the NIDCD grant DC 00181.]
Different interaural level difference processing with complex sounds and pure tones
Authors: Zhang Yuxuan , Wright Beverly A.
Published: October 2013

Interaural level differences (ILDs) are one of the primary cues to sound source position on the horizontal plane. Most studies on human performance with ILDs use simple sounds such as pure tones. However, naturally occurring acoustic stimuli usually have complex waveforms. Here human learning of ILD discrimination was examined with complex waveforms. Sixteen listeners were trained 1 hr/day for 9 days on ILD discrimination with a 4-kHz tone sinusoidally amplitude modulated at 0.3 kHz conveyed through headphones. Before and after training, they were tested, together with sixteen untrained controls, on the trained condition and five related untrained conditions (three with amplitude modulated tones, two with pure tones). The trained listeners improved significantly more than controls on all conditions with amplitude-modulated tones, but not on those with pure tones. The lack of generalization of ILD learning from modulated to pure tones suggests that practice modified ILD processing in a region that encodes complex sounds with a variety of carrier frequencies and modulation rates, but not pure tones. Thus, these findings suggest that waveform complexity is an important factor in ILD processing, and must be considered when evaluating human ILD performance. [Work supported by NIH.]
Diffuse fields in open systems and the emergence of the Green’s function
Authors: Weaver Richard
Published: October 2013

As is now well known, the relation between diffuse field correlations and the Green’s function follows directly from a definition of a diffuse field as an uncorrelated smooth spectral superposition of normal modes. Such a definition is, however, inapplicable in most open structures, the earth in particular. A preferable definition might be that of room acoustics: a diffuse field is an uncorrelated isotropic superposition of plane waves. But that definition is inapplicable to heterogeneous structures, or near boundaries. Here, a definition of a local diffuse field applicable to open heterogeneous systems is proposed. A local diffuse field is taken to be one in steady-state equilibrium with the field in a homogeneous region having an uncorrelated isotropic superposition of incident plane waves. This definition is applicable to both heterogeneous and open systems, and is shown using a reciprocity argument to lead to the familiar identity between the local Green’s function of the structure and the diffuse fields correlations.
Adaptive multi-modal active noise control
Authors: Smith Adam K. , Vipperman Jeffrey S. , Budny Daniel D.
Published: October 2013

Low frequency Active Noise Control (ANC) has been found to work well for sound suppression in acoustic ducts. Feedforward and feedback are the two distinct methods in which to implement (ANC) schemes. A feedforward implementation is realized by utilizing a known disturbance measurement (e.g. with a microphone), and using the measurement to compute the actuator (loudspeaker) signal. Feedback control modifies dynamics of an enclosed sound field to add damping. For example, one can use a resonant filter in the feedback path that is tuned to a selected mode in the enclosed sound field to be controlled. The resonant filter model is similar to those used for positive position feedback (PPF) in structures. A method of compensating the strong speaker dynamics (phase angle) was recently investigated by Bisnette and Vipperman (2004). The method was found to improve the performance and stability of the controller. Here, the above mentioned procedure is expounded upon to provide improved multi-modal performance, using higher order band-bass filters. Methods for adapting the controller parameters (e.g., gain, frequency, bandwidth) are also presented.
Microbubble oscillations and stability for drug delivery
Authors: Allen John S.
Published: October 2013

Ultrasound contrast agents have been developed from micron size bubbles whose gas core is enclosed by a polymer, lipid or protein shell. Furthermore, specific designs have been developed for drug delivery in which the ultrasound contrast agent acts as drug delivery vehicle. A drug may be suspended in the shell of these agents which is released at a particular site as the microbubble undergoes destruction. Localized delivery depends on the destruction of a sufficient number of bubbles within a confined geometry typically a capillary or small vessel. Experimental evidence suggests the composition and thickness of the shell play important role in the break-up. Break-up scenarios of buckling have been suggested for elastic shell agents and shape stability for fluid shell agents. However, these have not been rigorously examined theoretically. The formulations of contrast agent designed for drug delivery are highlighted including a description of a double polymeric layer design. Shape stability equations for fluid shell agents are derived and analyzed in limiting cases. Furthermore, biological issues related to potential endothelial cell transport and interactions are briefly discussed.
Acoustic explorations of the upper ocean boundary layer
Authors: Vagle Svein
Published: October 2013

The upper ocean boundary layer is an important but difficult to probe part of the ocean. A better understanding of small scale processes at the air-sea interface, including the vertical transfer of gases, heat, mass and momentum, are crucial to improving our understanding of the coupling between atmosphere and ocean. Also, this part of the ocean contains a significant part of the total biomass at all trophic levels and is therefore of great interest to researchers in a range of different fields. Innovative measurement plays a critical role in developing our understanding of the processes involved in the boundary layer, and the availability of low-cost, compact, digital signal processors and sonar technology in self-contained and cabled configurations has led to a number of exciting developments. This talk summarizes some recent explorations of this dynamic boundary layer using both active and passive acoustics. The resonant behavior of upper ocean bubbles combined with single and multi-frequency broad band active and passive devices are now giving us invaluable information on air-sea gas transfer, estimation of biological production, marine mammal behavior, wind speed and precipitation, surface and internal waves, turbulence, and acoustic communication in the surf zone.