bluuebunny/crossref_metadata_2025 huggingface dataset:
TH‐A‐116‐11: Multiple Isocenter IMAT: Impact of Technique On Junction Error Robustness
Authors: Ehler E , Higgins P , Dusenbery K
Published: July 2013

Purpose: Many techniques of delivering multiple isocentric IMRT or IMAT have been described. However, these studies have considered different treatment sites, reported different dosimetric parameters, and considered a limited degree of junction error, typically a 1D beam placement error of 3 mm. This work provides a direct comparison of these techniques by utilizing a consistent set of dosimetric parameters and a common treatment, craniospinal irradiation. Methods: Seven IMAT treatment plans were created, with three main features: (Method1) target subvolumes used to explicitly control the transition of dose from one set of beams to another in the junction region, (Method2) staggering the jaw settings for a set of arcs that overlap with another set of arc fields but not directly controlling the dose transition, (Method3) arranging beams to overlap 5–10 cm and allowing the inverse planning system to control the junction dose. Method3 was subdivided into three and four isocenter plans; four isocenter plans had greatest beam overlap. Then, the beam isocenters were off set 0.25 and 0.5 cm in each dimension (3D); therefore junction errors of 1.0 cm or greater were considered. For all plans, a total of 6 junction errors were considered. Results: Dosimetric impact of junction error was limited mostly to target volumes. The PTV V95 degraded by 6% to 9% and 1% to 3% for the 0.5 and 0.25 cm junction errors, respectively. For the CTV the V95 was impacted by 0.5% to 2.6% and 0.1% to 0.7%, respectively. The four isocenter plans of Method 3 consistently showed the largest degradation in V95 and V105 for both the PTV and CTV. Method1 and three field plans of Method 3 showed the least change in V95 and V105. Conclusion: Robust multiple isocenter IMAT plans, in terms of junction error, can be achieved with proper inverse planning techniques.
TH‐C‐137‐06: An Inter‐Fractional Morphing Aperture Based Reoptimization Tool for Adaptive Radiotherapy
Authors: Kearney V , Jiang L , Gu X , Solberg T , Mao W
Published: July 2013

Purpose: To dosimetrically evaluate a streamlined adaptive radiotherapy tool to account for inter‐fractional tumor shrinkage. A novel aperture‐morphed simultaneously optimized finite sized pencil beam algorithm (AMSO‐FSPB) was investigated over volumetric modulated arc therapy (VMAT) head and neck plans. Methods: AMSO‐FSPB plans were retrospectively designed for head and neck patients in the supine position. CT image sets between fractions were rigidly registered using normalized cross correlation. A demons based deformable image registration algorithm was used to obtain a deformation vector field (DVF) between fractions. The DVFs were used to map contours between fractions. An eclipse and pinnacle compatible contour mapping algorithm was developed to apply the DVFs to the structure dicom set. DRRs at each gantry angle were used to derive the ratio of tumor shrinkage at every MLC position. The DVF and the target contour shrinkage were used to obtain a new set of fluence maps. The machine tolerance guidelines for the Varian True beam were followed for this study. A graphics processor united (GPU) based FSPB dose calculation engine with an embedded weighting factor re‐optimization algorithm was developed to reassign beamlet weighting factors to every 4 degrees of arch length in the VMAT plan. Results: The dosimetric advantages of the AMSO‐FSPB VMAT plans were directly proportional to the amount of the tumor regression between fractions. AMSO‐FSPB VMAT plans were dosimetrically superior to the original plans for all cases. The ratio of the mean and maximum dose for the Paratoids, Spinal Cord, and Brain Stem were lowered for all cases. The mean for the PTV70Gy, PTV60Gy, and PTV54Gy was increased while the standard deviation was decreased for all cases. Conclusion: Implementation of the AMSO‐FSPB algorithm improved the dosimetric quality of the supine head and neck VMAT plans and was done so with minimal additional cost to clinical resources. This research is supported by CPRIT Individual Investigator Award RP110329.
TH‐C‐137‐11: Dose‐Guided Automatic IMRT Planning: A Feasibility Study
Authors: Sheng Y , Li T , Yuan L , Yin F , Wu Q
Published: July 2013

Purpose: To develop and evaluate an automatic planning technique for prostate cancer utilizing prior expert plan's dose as guidance. Methods: A plan atlas was created using 10 expert prostate IMRT plans covering a variety of typical anatomical configurations. The target includes both prostate and seminal vesicle. Additional 9 patients (query cases) were used to test the automatic planning, which started by matching the query case to the atlas based on the overall PTV‐OAR anatomical configuration. The anatomy of the matched atlas case is then linked to the query case via deformable registration in MIM Maestro™, which provides fine local‐regional matching. Following the same anatomical deformation, the expert dose in atlas is warped onto the query case, creating the goal dose conforming the query case's target. DVH objectives were sampled from the goal dose to guide automatic IMRT treatment planning in Eclipse™ for the query case. Dosimetry comparison between dose‐guided automatic plans (DAPs) and clinical plans for query cases are reported. Results: Generating goal dose is highly efficient with customized workflows in MIM™. The deformation registration provides a realistic goal dose for the query cases in terms of dose fall off at the PTV‐OAR junctions and PTV conformity. The automatic planning takes ∼2.5 min (∼70 iterations) without human intervention. Compared to clinical plans, DAPs improved the PTV conformity index from 1.031±0.044 for expert plans to 1.005±0.019 (p=0.04). Other dosimetric parameters are similar between DAP and clinical plans (p>0.1): homogeneity indices are 0.073±0.010 and 0.079±0.015; Bladder‐gEUDs are 3917±352 cGy and 3934±354 cGy; Rectum‐gEUDs are 3923±256 cGy and 3932±323 cGy, respectively. Conclusion: Dose‐guided automatic treatment planning is feasible and efficient. Atlas‐based patient‐specific DVH objectives can effectively guide the optimizer to achieve similar or better plan quality compared to clinical plans.(The authors thank Adam Neff from MIM Software Inc. for technical supports.) The study is partially supported by NIH grant and a Varian master research grant.
TH‐C‐103‐07: Iterative Cone Beam CT Reconstruction On a Multi‐GPU Platform
Authors: Wang X , Yan H , Cervino L , Jiang S , Jia X
Published: July 2013

Purpose: Compressed sensing‐based iterative cone beam CT (CBCT) reconstruction techniques can reconstruct CBCT from under‐sampled noisy projection data, allowing for imaging dose reduction. The long computation time prevents them from clinical applications. Although GPU dramatically improves computational efficiency, the computation time is still too long. The purpose of this project is to develop a reconstruction algorithm on a multi‐GPU platform. Methods: We have developed tight‐frame(TF) based CBCT reconstruction system on a workstation with 4 NVIDIA GTX590 GPUs. The algorithm iterates two steps: a conjugate gradient least square step (CGLS) enforcing projection condition and a regularization step improving image quality through TF domain. The first step involves frequent forward and backward x‐ray projections, which is accelerated by distributing tasks corresponding to different projection angles among GPUs. A parallel‐reduction algorithm is employed to accumulate data at all GPUs. The regularization step is achieved by having each GPU processing a sub‐volume. Boundary‐layer data between sub‐volumes are kept to maintain correct boundary conditions. A half‐fan reweighting technique is also invented to mitigate ring artifacts caused by imperfect scanning geometry. Results: Under the quad‐GPU system, the CGLS step, the regularization step are accelerated by 3.2∼3.6 times and 1.6∼2.6times compared to single‐GPU version, respectively. The overall speed‐up factor is 3.06∼3.51 times. As for the absolute time, it takes 0.41∼3.90 sec per iteration step depending on the image resolution and number of projections. Considering it usually takes about 10 iteration steps for the algorithm to achieve satisfactory image quality, the total reconstruction time ranges from a few seconds to up to 40 seconds. High quality CBCT images have been obtained in our system. The reweighing strategy also removes the ring artifacts in half‐fan cases. Conclusion: A TF‐based CBCT reconstruction on a multi‐GPU platform has been successfully developed. The achieved efficiency and image quality facilitates clinical implementations. This work is supported in part by NIH (1R01CA154747‐01), Varian Medical Systems through a Master Research Agreement, the Early Career Award from Thrasher Research Fund, and the University of California Lab Fees Research Program.
TH‐C‐144‐04: Robust Optimization in Intensity‐Modulated Proton Therapy for Base‐Of‐Skull Cancers
Authors: Liu W , Mohan R , Zhu X , Grosshans D
Published: July 2013

Purpose: Intensity‐modulated proton therapy (IMPT) is highly sensitive to uncertainties in beam range and patient setup. Here we evaluated plan robustness and optimality generated by a robust optimization method for a population of base‐of‐skull cases. The method incorporates uncertainties directly in optimization algorithm to ensure clinical target volume (CTV) coverage to uncertainties. Methods: Two IMPT plans were generated for each of 10 base‐of‐skull cases, one PTV‐based conventionally optimized and the other CTV‐based robustly optimized. For the conventionally optimized plans, uncertainties are considered with PTV margins, while delivering the prescribed dose to PTV. For the robustly optimized plans, optimization was guided to minimize deviation from the prescribed dose under extreme setup and range uncertainties, while delivering the prescribed dose to CTV. For each of these plans, we calculated dose distributions under various uncertainty scenarios. The root‐mean‐square‐deviation‐dose (RMSD) for each voxel was computed and the area under the RMSD‐volume histogram (RVH) curves (AUC) was used to compare relative plan robustness. Data derived from the dose volume histogram (DVH) in the worst‐case and nominal doses were used to evaluate plan optimality. Then the plan evaluation metrics were averaged and compared with paired t tests. Results: Compared with the conventional optimization, robust optimization led to more robust dose distributions (smaller AUCs) for both targets and organs‐at‐risks (OARs). In the nominal dose, robust optimization resulted in similar D95% doses (D95% CTV: 63.3 versus 64.8 Gy[RBE] [p<0.01]) and D5% minus D95% (D5% – D95% CTV: 8.0 versus 7.1 Gy[RBE] [p<0.01) for targets and irradiation of OARs was less with robust optimization (brainstem V60: 0.076 versus 0.26 cm3 [p<0.01]). Results in the worst‐case dose were consistent. Conclusions: CTV‐based robustly optimized IMPT for base‐of‐skull cancer provides a significantly more robust dose distribution to targets and OARs and better or equivalent sparing of OARs than PTV‐based conventionally optimized IMPT. Supported by National Cancer Institute Program Grant P01CA021239, by the University Cancer Foundation via the Institutional Research Grant program at The University of Texas MD Anderson Cancer Center, and by the National Cancer Institute of the National Institutes of Health under Career Award Number K25CA168984
TH‐C‐144‐05: Distal and Lateral Dose Perturbation From Collimator Scattering in Proton Radiotherapy
Authors: Zhao T , Grantham K , Goddu S , Klein E
Published: July 2013

Purpose: Dose perturbation from collimator scattering is not modeled by current treatment planning systems and is usually ignored in proton radiotherapy. In this work we study the dosimetric impact of collimator scattering and possible solutions. Methods: Three sets of apertures with non‐diverging edge, diverging edge and stepped edges that averaged divergence for each single piece, were milled by CURA to produce a 10cm×10cm field at isocenter. Cross‐plane profiles were measured at a shallow (2cm) and deep (7.5cm) depths with EBT3 films, delivered with the Mevion S250 system, which has a relatively shorter SAD (∼2m). Films were irradiated with a fully modulated proton beam with range of 15cm in water. In‐plane profiles were also acquired on a coronal plane along the central axis. Results: Although negligible changes in lateral penumbra were observed in all cases, collimator scattering added up to 11% extra dose near the field edge for the non‐diverging edge aperture. For diverging and stepped edge apertures, extra dose from collimator scattering were reduced to less than 5% at 2cm depth, and was negligible at 7.5cm depth. Deterioration of distal penumbra was observed in both non‐diverging and stepped edged apertures, broadened to 13mm from 8mm, which was measured for the diverging edge aperture. Conclusion: Collimator scattering from apertures not only introduce extra dose near the field edge at shallow depths, but also deteriorates the distal penumbra. A diverging‐cut aperture can eliminate both contaminations. Divergent edges should be considered in apertures when sensitive organs are lateral at shallow depths, or distal to the target. blown MC. The method can be integrated in existing TPS to enable PET‐based treatment verification in the daily clinical routine of proton therapy.
TH‐C‐144‐08: Characterizing Prompt Gamma Signal During Proton Radiotherapy
Authors: Polf J , Mackin D , Lee E , Avery S , Dolney D , Beddar S
Published: July 2013

Purpose: Recent studies have suggested that the characteristics of prompt gammas (PG) emitted from excited oxygen nuclei during proton therapy are advantageous for determining beam range during treatment delivery. Since PGs are only emitted while the beam is on, the feasibility of using oxygen PGs for treatment verification depends greatly on the design of highly efficient detectors. The purpose of this work is to characterize the oxygen PG emission emitted from the patient to help drive the design of clinically viable detectors. Methods and Materials: Using a validated Monte Carlo (MC) model of PG emission during proton irradiation, we studied the oxygen PG detection efficiency in a high purity Germanium detector. PG spectra recorded by the detector were calculated as a function of distance for a patient irradiated with clinical proton pencil beams. Changes to the fluence of 6.13 MeV oxygen PGs incident on the detector were characterized as a function of distance from patient isocenter and proton beam energy. Results: The detection efficiency was found to be 2.33×10−8 oxygen PGs per proton at 10 cm distance at 40 MeV. Falloff of the measured PG signal was found to decrease rapidly as a function of distance. However, compared to the efficiency at 40 MeV, the detection efficiency increased by 60% at 70 MeV and by up to 90% for energies greater than 150MeV. Conclusion: Due to the characteristics of PG emission from oxygen with respect to proton energy (i.e. depth in the patient), the falloff of detected 6.13 MeV PGs varied with the distance from the patient, the solid angle subtended by the detector, and the energy of the proton beam. The falloff of the PG signal was described well by that of a point source at isocenter irradiating a cylindrical detector of a known diameter. National Institute of Health, Grant# R21CA137362
Application of nonlinear sliding mode control to ultrasound contrast agent microbubbles
Authors: Carroll James M. , Lauderbaugh Leal K. , Calvisi Michael L.
Published: July 2013

A sliding mode control system is developed and applied to a spherical model of a contrast agent microbubble that simulates its radial response to ultrasound. The model uses a compressible form of the Rayleigh-Plesset equation combined with a thin-shell model. A nonlinear control law for the second-order model is derived and used to design and simulate the controller. The effect of the controller on the contrast agent response is investigated for various control scenarios. This work demonstrates the feasibility of using a nonlinear control system to modulate the dynamic response of ultrasound contrast agents, but highlights the need for improved feedback mechanisms and control input methods. Possible applications of the nonlinear control system to contrast agents illustrated in this work include radius stabilization in the presence of an acoustic wave, radial growth and subsequent collapse, and generation of periodic radial oscillations while a contrast agent is within an acoustic forcing regime known to cause a chaotic response.
Within-consonant perceptual differences in the hearing impaired ear
Authors: Trevino Andrea , Allen Jont B.
Published: July 2013

The consonant recognition of 17 ears with sensorineural hearing loss is evaluated for 14 consonants /p, t, k, f, s, ʃ , b, d, g, v, z, ʒ, m, n/+/ɑ/, under four speech-weighted noise conditions (0, 6, 12 dB SNR, quiet). One male and one female talker were chosen for each consonant, resulting in 28 total consonant-vowel test tokens. For a given consonant, tokens by different talkers were observed to systematically differ, in both the robustness to noise and/or the resulting confusion groups. Such within-consonant token differences were observed for over 60% of the tested consonants and all HI ears. Only when HI responses are examined on an individual token basis does one find that the error may be limited to a small subset of tokens with confusion groups that are restricted to fewer than three confusions on average. Averaging different tokens of the same consonant can raise the entropy of a listener's responses (i.e., the size of the confusion group), causing the listener to appear to behave in a less systematic way. Quantifying these token differences provides insight into HI perception of speech under noisy conditions and characterizes each listener's hearing impairment.
A comparison of spectral magnitude and phase-locking value analyses of the frequency-following response to complex tones
Authors: Zhu Li , Bharadwaj Hari , Xia Jing , Shinn-Cunningham Barbara
Published: July 2013

Two experiments, both presenting diotic, harmonic tone complexes (100 Hz fundamental), were conducted to explore the envelope-related component of the frequency-following response (FFRENV), a measure of synchronous, subcortical neural activity evoked by a periodic acoustic input. Experiment 1 directly compared two common analysis methods, computing the magnitude spectrum and the phase-locking value (PLV). Bootstrapping identified which FFRENV frequency components were statistically above the noise floor for each metric and quantified the statistical power of the approaches. Across listeners and conditions, the two methods produced highly correlated results. However, PLV analysis required fewer processing stages to produce readily interpretable results. Moreover, at the fundamental frequency of the input, PLVs were farther above the metric's noise floor than spectral magnitudes. Having established the advantages of PLV analysis, the efficacy of the approach was further demonstrated by investigating how different acoustic frequencies contribute to FFRENV, analyzing responses to complex tones composed of different acoustic harmonics of 100 Hz (Experiment 2). Results show that the FFRENV response is dominated by peripheral auditory channels responding to unresolved harmonics, although low-frequency channels driven by resolved harmonics also contribute. These results demonstrate the utility of the PLV for quantifying the strength of FFRENV across conditions.
Measuring stimulus-frequency otoacoustic emissions using swept tones
Authors: Kalluri Radha , Shera Christopher A.
Published: July 2013

Although stimulus-frequency otoacoustic emissions (SFOAEs) offer compelling advantages as noninvasive probes of cochlear function, they remain underutilized compared to other evoked emission types, such as distortion-products (DPOAEs), whose measurement methods are less complex and time-consuming. Motivated by similar advances in the measurement of DPOAEs, this paper develops and characterizes a more efficient SFOAE measurement paradigm based on swept tones. In contrast to standard SFOAE measurement methods, in which the emissions are measured in the sinusoidal steady-state using discrete tones of well defined frequency, the swept-tone method sweeps rapidly across frequency (typically at rates of 1 Hz/ms or greater) using a chirp-like stimulus. Measurements obtained using both swept- and discrete-tone methods in an interleaved suppression paradigm demonstrate that the two methods of measuring SFOAEs yield nearly equivalent results, the differences between them being comparable to the run-to-run variability encountered using either method alone. The match appears robust to variations in measurement parameters, such as sweep rate and direction. The near equivalence of the SFOAEs obtained using the two measurement methods enables the interpretation of swept-tone SFOAEs within existing theoretical frameworks. Furthermore, the data demonstrate that SFOAE phase-gradient delays—including their large and irregular fluctuations across frequency—reflect actual physical time delays at different frequencies, showing that the physical emission latency, not merely the phase gradient, is inherently irregular.
Determination of the complex acoustic scattering matrix of a right-angled duct
Authors: Graf Thomas , Pan Jie
Published: July 2013

A method for determining the complete higher-order scattering matrix of an acoustic discontinuity is developed. The method is demonstrated for a right-angled waveguide bend, and the magnitude and phase of the reflection and transmission coefficients are extracted precisely. The procedure is straightforward and based on the solutions to the Helmholtz equation by the finite element method (FEM). The consistency of the scattering coefficients found by this method is verified by their properties of symmetry, and their accuracy is established by the conservation of energy. The reliability of the new technique is further proved by means of an arbitrary sound source and by comparing the direct FEM response to the reflection matrix calculation. Some features of the scattering matrix as a function of frequency are surprising, such as the steps and reversion of the phase evolution or the complete loss of transmission of the incoming wave. The methodology detailed in this paper can be extended to other multiport junctions, such as T-junctions or size discontinuities in ducts.
Relation of distortion-product otoacoustic emission input-output functions to loudness
Authors: Rasetshwane Daniel M. , Neely Stephen T. , Kopun Judy G. , Gorga Michael P.
Published: July 2013

The aim of this study is to further explore the relationship between distortion-product otoacoustic emission (DPOAE) measurements and categorical loudness scaling (CLS) measurements using multiple linear regression (MLR) analysis. Recently, Thorson et al. [J. Acoust. Soc. Am. 131, 1282–1295 (2012)] obtained predictions of CLS loudness ratings from DPOAE input/output (I/O) functions using MLR analysis. The present study extends that work by (1) considering two different (and potentially improved) MLR models, one for predicting loudness rating at specified input level and the other for predicting the input level for each loudness category and (2) validating the new models' predictions using an independent set of data. Strong correlations were obtained between predicted and measured data during the validation process with overall root-mean-square errors in the range 10.43–16.78 dB for the prediction of CLS input level, supporting the view that DPOAE I/O measurements can predict CLS loudness ratings and input levels, and thus may be useful for fitting hearing aids.
A multi-resolution envelope-power based model for speech intelligibility
Authors: Jørgensen Søren , Ewert Stephan D. , Dau Torsten
Published: July 2013

The speech-based envelope power spectrum model (sEPSM) presented by Jørgensen and Dau [(2011). J. Acoust. Soc. Am. 130, 1475–1487] estimates the envelope power signal-to-noise ratio (SNRenv) after modulation-frequency selective processing. Changes in this metric were shown to account well for changes of speech intelligibility for normal-hearing listeners in conditions with additive stationary noise, reverberation, and nonlinear processing with spectral subtraction. In the latter condition, the standardized speech transmission index [(2003). IEC 60268-16] fails. However, the sEPSM is limited to conditions with stationary interferers, due to the long-term integration of the envelope power, and cannot account for increased intelligibility typically obtained with fluctuating maskers. Here, a multi-resolution version of the sEPSM is presented where the SNRenv is estimated in temporal segments with a modulation-filter dependent duration. The multi-resolution sEPSM is demonstrated to account for intelligibility obtained in conditions with stationary and fluctuating interferers, and noisy speech distorted by reverberation or spectral subtraction. The results support the hypothesis that the SNRenv is a powerful objective metric for speech intelligibility prediction.
Speech rhythm analysis with decomposition of the amplitude envelope: Characterizing rhythmic patterns within and across languages
Authors: Tilsen Sam , Arvaniti Amalia
Published: July 2013

This study presents a method for analyzing speech rhythm using empirical mode decomposition of the speech amplitude envelope, which allows for extraction and quantification of syllabic- and supra-syllabic time-scale components of the envelope. The method of empirical mode decomposition of a vocalic energy amplitude envelope is illustrated in detail, and several types of rhythm metrics derived from this method are presented. Spontaneous speech extracted from the Buckeye Corpus is used to assess the effect of utterance length on metrics, and it is shown how metrics representing variability in the supra-syllabic time-scale components of the envelope can be used to identify stretches of speech with targeted rhythmic characteristics. Furthermore, the envelope-based metrics are used to characterize cross-linguistic differences in speech rhythm in the UC San Diego Speech Lab corpus of English, German, Greek, Italian, Korean, and Spanish speech elicited in read sentences, read passages, and spontaneous speech. The envelope-based metrics exhibit significant effects of language and elicitation method that argue for a nuanced view of cross-linguistic rhythm patterns.
An investigation of articulatory setting using real-time magnetic resonance imaging
Authors: Ramanarayanan Vikram , Goldstein Louis , Byrd Dani , Narayanan Shrikanth S.
Published: July 2013

This paper presents an automatic procedure to analyze articulatory setting in speech production using real-time magnetic resonance imaging of the moving human vocal tract. The procedure extracts frames corresponding to inter-speech pauses, speech-ready intervals and absolute rest intervals from magnetic resonance imaging sequences of read and spontaneous speech elicited from five healthy speakers of American English and uses automatically extracted image features to quantify vocal tract posture during these intervals. Statistical analyses show significant differences between vocal tract postures adopted during inter-speech pauses and those at absolute rest before speech; the latter also exhibits a greater variability in the adopted postures. In addition, the articulatory settings adopted during inter-speech pauses in read and spontaneous speech are distinct. The results suggest that adopted vocal tract postures differ on average during rest positions, ready positions and inter-speech pauses, and might, in that order, involve an increasing degree of active control by the cognitive speech planning mechanism.
Elliptical acoustic particle motion in underwater waveguides
Authors: Dall'Osto David R. , Dahl Peter H.
Published: July 2013

Elliptical particle motion, often encountered in acoustic fields containing interference between a source signal and its reflections, can be quantified by the degree of circularity, a vector quantity formulated from acoustic particle velocity, or vector intensity measurements. Acoustic analysis based on the degree of circularity is expected to find application in ocean waveguides as its spatial dependence relates to the acquisition geometry, water column sound speed, surface conditions, and bottom properties. Vector sensor measurements from a laboratory experiment are presented to demonstrate the depth dependence of both the degree of circularity and an approximate formulation based on vertical intensity measurements. The approximation is applied to vertical intensity field measurements made in a 2006 experiment off the New Jersey coast (in waters 80 m deep) to demonstrate the effect of sediment structure on the range dependence of the degree of circularity. The mathematical formulation presented here establishes the framework to readily compute the degree of circularity from experimental measurements; the experimental examples are provided as evidence of the spatial and frequency dependence of this fundamental vector property.
Unilateral and bilateral hearing aids, spatial release from masking and auditory acclimatization
Authors: Dawes Piers , Munro Kevin J. , Kalluri Sridhar , Edwards Brent
Published: July 2013

Spatial release from masking (SRM) was tested within the first week of fitting and after 12 weeks hearing aid use for unilateral and bilateral adult hearing aid users. A control group of experienced hearing aid users completed testing over a similar time frame. The main research aims were (1) to examine auditory acclimatization effects on SRM performance for unilateral and bilateral hearing aid users, (2) to examine whether hearing aid use, level of hearing loss, age or cognitive ability mediate acclimatization, and (3) to compare and contrast the outcome of unilateral versus bilateral aiding on SRM. Hearing aid users were tested with and without hearing aids, with SRM calculated as the 50% speech recognition threshold advantage when maskers and target are spatially separated at ±90° azimuth to the listener compared to a co-located condition. The conclusions were (1) on average there was no improvement over time in familiar aided listening conditions, (2) there was large test-retest variability which may overshadow small average acclimatization effects; greater improvement was associated with better cognitive ability and younger age, but not associated with hearing aid use, and (3) overall, bilateral aids facilitated better SRM performance than unilateral aids.
Soundwalk approach to identify urban soundscapes individually
Authors: Yong Jeon Jin , Young Hong Joo , Jik Lee Pyoung
Published: July 2013

This study proposes a soundwalk procedure for evaluating urban soundscapes. Previous studies, which adopted soundwalk methodologies for investigating participants' responses to visual and acoustic environments, were analyzed considering type, evaluation position, measurement, and subjective assessment. An individual soundwalk procedure was then developed based on asking individual subjects to walk and select evaluation positions where they perceived any positive or negative characteristics of the urban soundscape. A case study was performed in urban spaces and the results were compared with those of the group soundwalk to validate the individual soundwalk procedure. Thirty subjects (15 architects and 15 acousticians) participated in the soundwalk. During the soundwalk, the subjects selected a total of 196 positions, and those were classified into 4 groups. It was found that soundscape perceptions were dominated by acoustic comfort, visual images, and openness. It was also revealed that perceived elements of the acoustic environment and visual image differed across classified soundscape groups, and there was a difference between architects and acousticians in terms of how they described their impressions of the soundscape elements. The results show that the individual soundwalk procedure has advantages for measuring diverse subjective responses and for obtaining the perceived elements of the urban soundscape.
Application of a methodology for categorizing and differentiating urban soundscapes using acoustical descriptors and semantic-differential attributes
Authors: Torija Antonio J. , Ruiz Diego P. , Ramos-Ridao A. F.
Published: July 2013

A subjective and physical categorization of an ambient sound is the first step to evaluate the soundscape and provides a basis for designing or adapting this ambient sound to match people's expectations. For this reason, the main goal of this work is to develop a categorization and differentiation analysis of soundscapes on the basis of acoustical and perceptual variables. A hierarchical cluster analysis, using 15 semantic-differential attributes and acoustical descriptors to include an equivalent sound-pressure level, maximum-minimum sound-pressure level, impulsiveness of the sound-pressure level, sound-pressure level time course, and spectral composition, was conducted to classify soundscapes into different typologies. This analysis identified 15 different soundscape typologies. Furthermore, based on a discriminant analysis the acoustical descriptors, the crest factor (impulsiveness of the sound-pressure level), and the sound level at 125 Hz were found to be the acoustical variables with the highest impact in the differentiation of the recognized types of soundscapes. Finally, to determine how the different soundscape typologies differed from each other, both subjectively and acoustically, a study was performed.
The perceived quality of soundscape in three urban parks in Rome
Authors: Brambilla Giovanni , Gallo Veronica , Asdrubali Francesco , D'Alessandro Francesco
Published: July 2013

The present paper reports a socio-acoustic survey carried out in three large urban parks in Rome, selected on the basis of the outcome of a preliminary online survey. According to the experimental protocol applied in a previous study carried out in Milan and Naples, binaural recordings in 85 sites and interviews with 266 users of the three parks were performed only during the day in summertime. On the basis of selected acoustical descriptors, the sonic environment of the three parks was categorized and, thanks to statistical analysis, three clusters were identified. The results confirm that the sound environment in urban parks is often considered as “good” or “excellent” even if the sound pressure level is nearly always higher than the limits commonly used to define quiet areas. This is due to the influence of other factors, such as the presence of trees, natural features, and the tranquility; all of these components cannot be neglected in the assessment of the soundscape because they directly affect the psychological state of the person.
Lexically guided retuning of visual phonetic categories
Authors: van der Zande Patrick , Jesse Alexandra , Cutler Anne
Published: July 2013

Listeners retune the boundaries between phonetic categories to adjust to individual speakers' productions. Lexical information, for example, indicates what an unusual sound is supposed to be, and boundary retuning then enables the speaker's sound to be included in the appropriate auditory phonetic category. In this study, it was investigated whether lexical knowledge that is known to guide the retuning of auditory phonetic categories, can also retune visual phonetic categories. In Experiment 1, exposure to a visual idiosyncrasy in ambiguous audiovisually presented target words in a lexical decision task indeed resulted in retuning of the visual category boundary based on the disambiguating lexical context. In Experiment 2 it was tested whether lexical information retunes visual categories directly, or indirectly through the generalization from retuned auditory phonetic categories. Here, participants were exposed to auditory-only versions of the same ambiguous target words as in Experiment 1. Auditory phonetic categories were retuned by lexical knowledge, but no shifts were observed for the visual phonetic categories. Lexical knowledge can therefore guide retuning of visual phonetic categories, but lexically guided retuning of auditory phonetic categories is not generalized to visual categories. Rather, listeners adjust auditory and visual phonetic categories to talker idiosyncrasies separately.
Numerical methodologies for optimizing and predicting the low frequency behavior of anechoic chambers
Authors: Bonfiglio Paolo , Pompoli Francesco
Published: July 2013

This paper presents a description of the use of simplified numerical methodologies for the optimization of the low cut-off frequency of anechoic and hemi-anechoic chambers. The anechoic chamber is modeled as a cavity with proper surface impedance boundary conditions. First, the shape of the wedges is optimized by means of a minimization-based procedure of a finite element model of such elements in a “virtual” impedance tube for a plane wave field. An equivalent surface impedance of the wedges is determined from those data. An analytical procedure is then used to determine the complex reflection coefficient for spherical waves at oblique incidence. Finally, a complex image source approach is used to predict the sound field within the chamber. The methodology is applied to two anechoic chambers and the results are compared in terms of sound decay along fixed directions and surface pressure distributions.
Effectiveness of focused source generation methods with consideration of interaural time and level difference
Authors: Zheng Jianwen , Lu Jing , Chen Kai
Published: July 2013

Several methods have been proposed for the generation of the focused source, usually a virtual monopole source positioned in between the loudspeaker array and the listener. The problem of pre-echoes of the common analytical methods has been noticed, and the most concise method to cope with this problem is the angular weight method. In this paper, the interaural time and level difference, which are well related to the localization cues of human auditory systems, will be used to further investigate the effectiveness of the focused source generation methods. It is demonstrated that the combination of angular weight method and the numerical pressure matching method has comparatively better performance in a given reconstructed area.
Source levels of social sounds in migrating humpback whales (Megaptera novaeangliae)
Authors: Dunlop Rebecca A. , Cato Douglas H. , Noad Michael J. , Stokes Dale M.
Published: July 2013

The source level of an animal sound is important in communication, since it affects the distance over which the sound is audible. Several measurements of source levels of whale sounds have been reported, but the accuracy of many is limited because the distance to the source and the acoustic transmission loss were estimated rather than measured. This paper presents measurements of source levels of social sounds (surface-generated and vocal sounds) of humpback whales from a sample of 998 sounds recorded from 49 migrating humpback whale groups. Sources were localized using a wide baseline five hydrophone array and transmission loss was measured for the site. Social vocalization source levels were found to range from 123 to 183 dB re 1 μPa @ 1 m with a median of 158 dB re 1 μPa @ 1 m. Source levels of surface-generated social sounds (“breaches” and “slaps”) were narrower in range (133 to 171 dB re 1 μPa @ 1 m) but slightly higher in level (median of 162 dB re 1 μPa @ 1 m) compared to vocalizations. The data suggest that group composition has an effect on group vocalization source levels in that singletons and mother-calf-singing escort groups tend to vocalize at higher levels compared to other group compositions.
Polarity effects on place pitch and loudness for three cochlear-implant designs and at different cochlear sites
Authors: Carlyon Robert P. , Deeks John M. , Macherey Olivier
Published: July 2013

Users of Advanced Bionics, MedEl, and Cochlear Corp. implants balanced the loudness of trains of asymmetric pulses of opposite polarities presented in monopolar mode. For the Advanced Bionics and MedEl users the pulses were triphasic and consisted of a 32-μs central phase flanked by two 32-μs phases of opposite polarity and half the amplitude. The central phase was either anodic (TP-A) or cathodic (TP-C). For the Cochlear Corp. users, pulses consisted of two 32-μs phases of the same polarity separated by an 8-μs gap, flanked by two 32-μs phases of the opposite polarity, each of which was separated from the central portion by a 58-μs gap. The central portion of these quadraphasic pulses was either anodic (QP-A) or cathodic (QP-C), and all phases had the same amplitude. The current needed to achieve matched loudness was lower for the anodic than for the cathodic stimuli. This polarity effect was similar across all electrode locations studied, including the most apical electrode of the MedEl device which stimulates the very apex of the cochlea. In addition, when quadraphasic pulses were presented in bipolar mode, listeners reported hearing a lower pitch when the central portion was anodic at the more apical, than at the more basal, electrode. The results replicate previous reports that, unlike the results of most animal studies, human cochlear implant listeners are more sensitive to anodic than to cathodic currents, and extend those findings to a wider range of cochlear sites, implant types, and pulse shapes.
Evaluation of a separation method for source identification in small spaces
Authors: Braikia Yacine , Melon Manuel , Langrenne Christophe , Bavu Éric , Garcia Alexandre
Published: July 2013

This paper investigates the efficiency of a field separation method for the identification of sound sources in small and non-anechoic spaces. When performing measurements in such environments, the acquired data contain information from the direct field radiated by the source of interest and reflections from walls. To get rid of the unwanted contributions and assess the field radiated by the source of interest, a field separation method is used. Acoustic data (pressure or velocity) are then measured on a hemispheric array whose base is laying on the surface of interest. Then, by using spherical harmonic expansions, contributions from outgoing and incoming waves can be separated if the impedance of the tested surface is high enough. Depending on the probe type, different implementations of the separation method are numerically compared. In addition, the influence of the walls' reflection coefficient is studied. Finally, measurements are performed using an array made-up of 36 p-p probes. Results obtained in a car trunk mock-up with controlled sources are first presented before reporting results measured in a real car running on a roller bench.
Enhanced multistatic active sonar signal processing
Authors: Zhao Kexin , Liang Junli , Karlsson Johan , Li Jian
Published: July 2013

Multistatic active sonar systems involve the transmission and reception of multiple probing sequences and can achieve significantly enhanced performance of target detection and localization through exploiting spatial diversity. This paper mainly focuses on two signal processing aspects of such systems, namely, enhanced range-Doppler imaging and improved target parameter estimation. The main contributions of this paper are (1) a hybrid dense-sparse method is proposed to generate range-Doppler images with both low sidelobe levels and high accuracy; (2) a generalized K-Means clustering (GKC) method for target association is developed to associate the range measurements from different transmitter-receiver pairs, which is actually a range fitting procedure; (3) the extended invariance principle-based weighted least-squares method is developed for accurate target position and velocity estimation. The effectiveness of the proposed multistatic active sonar signal processing techniques is verified using numerical examples.
Range dependent sediment sound speed profile measurements using the image source method
Authors: Pinson S. , Guillon L. , Holland C. W.
Published: July 2013

This paper presents a range dependent sediment sound speed profile measurement obtained using the image source method. This technique is based on the analysis of the seafloor reflected acoustic wave as a collection of image sources which positions are linked with the thick-nesses and the sound speed of the sediment stack. The data used were acquired by the NURC in 2009 during the Clutter09 experiment. The equipment used was an autonomous undersea vehicle towing a 1600–3500 Hz frequency band source and a 32 m horizontal line array of 32 hydrophones at 12 m above the seabed. Under the assumption of locally range independent seabed properties, the moving horizontal array provides successive range independent sediment sound speed profiles along a track to obtain the range and depth dependent structure of the seafloor. Two key steps include recovery of the time-varying unknown array shape from the data and spatial filtering of the successive sound speed profiles. A comparison of the image source method result and seismic data along nearly the same 14 km track indicates that the seabed stratigraphy is correctly mapped by this method.
Subcritical penetration into rough seafloors due to Bragg scattering
Authors: Peng Linhui , Yu Gaokun
Published: July 2013

A tank experiment and theoretical analysis are carried out to study acoustic Bragg scattering by a sinusoidal surface with period 0.3 m and amplitude 2 cm between water and sand sediment. The penetrating field is measured in the frequency range from 20 to 40 kHz at grazing angles 10° to 90° in the tank. A theoretical solution for acoustic scattering by the sinusoidal surface is derived to explain the interference pattern observed in the experiment. The result shows that the minus first order Bragg scattering wave is strong enough to interfere with the refracted wave obeying Snell's law, forming interference patterns that can be detected experimentally.
ACOUSTICAL STANDARDS NEWS
Authors: Blaeser Susan B. , Schomer Paul D.
Published: July 2013

American National Standards (ANSI Standards) developed by Accredited Standards Committees S1, S2, S3, and S12 in the areas of acoustics, mechanical vibration and shock, bioacoustics, and noise, respectively, are published by the Acoustical Society of America (ASA). In addition to these standards, ASA publishes catalogs of Acoustical Standards, both National and International. To receive copies of the latest Standards catalogs, please contact Susan B. Blaeser.

Comments are welcomed on all material in Acoustical Standards News.

This Acoustical Standards News section in JASA, as well as the National and International Catalogs of Acoustical Standards, and other information on the Standards Program of the Acoustical Society of America, are available via the ASA home page: http://acousticalsociety.org.
Acoustic discrimination of healthy swallows from upper airway movements
Authors: Skowronski Mark D. , Crary Michael A. , Shrivastav Rahul
Published: July 2013

Spontaneous swallowing in dysphagic individuals has been shown to occur at a lower rate compared to healthy controls, and passive swallowing detection may function as a valid screening test to identify dysphagia in at-risk populations. To automate swallow identification, acoustic source and vocal tract features were extracted from two types of swallows and eight upper airway movements from nine healthy subjects. Swallow vs non-swallow classification accuracy was 96.3 ± 1.1%. The results provide useful methods for further development of automated tools for identification of patients with swallowing impairment.