bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimentally determined spectral optimization for dedicated breast computed tomography
Authors: Prionas Nicolas D. , Huang Shih‐Ying , Boone John M.
Published: February 2011

Purpose:

The current study aimed to experimentally identify the optimal technique factors (x‐ray tube potential and added filtration material/thickness) to maximize soft‐tissue contrast, microcalcification contrast, and iodine contrast enhancement using cadaveric breast specimens imaged with dedicated breast computed tomography (bCT). Secondarily, the study aimed to evaluate the accuracy of phantom materials as tissue surrogates and to characterize the change in accuracy with varying bCT technique factors.

Methods:

A cadaveric breast specimen was acquired under appropriate approval and scanned using a prototype bCT scanner. Inserted into the specimen were cylindrical inserts of polyethylene, water, iodine contrast medium (iodixanol, 2.5 mg/ml), and calcium hydroxyapatite (100 mg/ml). Six x‐ray tube potentials (50, 60, 70, 80, 90, and 100 kVp) and three different filters (0.2 mm Cu, 1.5 mm Al, and 0.2 mm Sn) were tested. For each set of technique factors, the intensity (linear attenuation coefficient) and noise were measured within six regions of interest (ROIs): Glandular tissue, adipose tissue, polyethylene, water, iodine contrast medium, and calcium hydroxyapatite. Dose‐normalized contrast to noise ratio (CNRD) was measured for pairwise comparisons among the six ROIs. Regression models were used to estimate the effect of tube potential and added filtration on intensity, noise, and CNRD.

Results:

Iodine contrast enhancement was maximized using 60 kVp and 0.2 mm Cu. Microcalcification contrast and soft‐tissue contrast were maximized at 60 kVp. The 0.2 mm Cu filter achieved significantly higher CNRD for iodine contrast enhancement than the other two filters, but microcalcification contrast and soft‐tissue contrast were similar using the copper and aluminum filters. The average percent difference in linear attenuation coefficient, across all tube potentials, for polyethylene versus adipose tissue was 1.8%, 1.7%, and 1.3% for 0.2 mm Cu, 1.5 mm Al, and 0.2 mm Sn, respectively. For water versus glandular tissue, the average percent difference was 2.7%, 3.9%, and 4.2% for the three filter types.

Conclusions:

Contrast‐enhanced bCT, using injected iodine contrast medium, may be optimized for maximum contrast of enhancing lesions at 60 kVp with 0.2 mm Cu filtration. Soft‐tissue contrast and microcalcification contrast may also benefit from lower tube potentials (60 kVp). The linear attenuation coefficients of water and polyethylene slightly overestimate the values of their corresponding tissues, but the reported differences may serve as guidance for dosimetry and quality assurance using tissue equivalent phantoms.
Frame‐to‐frame image realignment assessment tool for dynamic brain positron emission tomography
Authors: Dinelle Katherine , Ngo Henry , Blinder Stephan , Vafai Nasim , Topping Geoff , Sossi Vesna
Published: February 2011

Purpose:

Subject motion during positron emission tomography (PET) brain scans can reduce image quality and may lead to incorrect biological outcome measures, especially for data acquired with high resolution tomographs. A semiautomatic method for assessing the quality of frame‐to‐frame image realignments to compensate for subject motion in dynamic brain PET is proposed and evaluated.

Methods:

A test set of 256‐raclopride (a dopamine D2‐type receptor antagonist) brain PET image frames was used to develop and evaluate the proposed method. The transformation matrix to be applied to each image to achieve a frame‐to‐frame realignment was calculated with two independent methods: Using motion data measured with the Polaris Vicra optical tracking device and using the image‐based realignment algorithm AIR (automated image registration). The quality assessment method is based on the observation that there is a very low probability that two independent approaches to motion detection will produce equal, but incorrect results. Agreement between transformation matrices was taken to be a signature of an accurate motion determination and thus realignment. Each pair of realignment matrices was compared and used to calculate a metric describing the frame‐to‐frame image realignment accuracy. In order to determine the range of values of the metric that correspond to a successful realignment, a comparison was made to a detailed visual inspection of the frame‐to‐frame realigned images for each image in the test set. The threshold on the metric for realignment acceptance was then selected to optimize the numbers of true‐positives (realignments accepted by both the protocol and the operator) and minimize the number of false‐positives (accepted by the protocol but not the operator).

Results:

The proposed method categorized 53% of the image realignments in the test dataset as successful, of which 11% were incorrectly categorized (6% of the total dataset). Implementation of the proposed assessment tool resulted in a 45% time savings compared to the same visual inspection applied to all image realignments.

Conclusions:

The frame‐to‐frame image realignment assessment tool presented here required less operator time to evaluate realignment success compared to a method requiring visual inspection of all realigned images, while maintaining the same level of accuracy in the realigned dataset. This practical method can be easily implemented at any center with motion monitoring capabilities or, for centers lacking this technology, methods of estimating image realignment parameters that use independent information. In addition, the procedure is flexible, allowing modifications to be made for different tracer types and/or downstream analysis goals.
Characterization of mesothelioma and tissues present in contrast‐enhanced thoracic CT scans
Authors: Corson Neal , Sensakovic William F. , Straus Christopher , Starkey Adam , Armato Samuel G.
Published: February 2011

Purpose:

The purpose of this study was to characterize the Hounsfield unit (HU) distributions of mesothelioma and other tissues present in contrast‐enhanced thoracic CT scans, to compare the HU distributions of mesothelioma, muscle, and liver by scanner and reconstruction filter/kernel combination, and to assess interpatient HU distribution variability.

Methods:

The database consisted of 28 contrast‐enhanced thoracic CT scans from different patients. For each scan, regions of interest were manually outlined within each of 13 tissues, including mesothelioma. For each tissue, the empirical percentiles in HU values were calculated along with the interpatient variability. The HU distributions of select tissues were compared across three different scanner and reconstruction filter/kernel combinations.

Results:

The HU distributions of blood‐containing tissues demonstrated substantial overlap, as did the HU distributions of pleural effusion, mesothelioma, muscle, and liver. The HU distribution of fat had the least overlap with the other tissues. Fat and muscle had the lowest interpatient HU variability and the narrowest HU distributions, while blood‐containing tissues had the highest interpatient HU variability. A soft‐tissue reconstruction filter/kernel yielded the narrowest HU distribution, and fat with artifact had the widest HU distribution.

Conclusions:

Characterization of tissues in CT scans enhances the understanding of those tissues' HU distributions. Due to their overlapping HU distributions and close spatial proximity to one another, separating pleural effusion, mesothelioma, muscle, and liver from one another is a difficult task based on HU value thresholding alone. The results illustrate the wide distributions and large variability that exist for tissues present in clinical thoracic CT scans.
Comparison of three image comparison methods for the visual assessment of the image fidelity of compressed computed tomography images
Authors: Kim Bohyoung , Lee Hyunna , Kim Kil Joong , Seo Jinwook , Park Seongjin , Shin Yeong‐Gil , Kim Soo Hong , Lee Kyoung Ho
Published: February 2011

Purpose:

This study aimed to comparatively evaluate three different image comparison methods: alternate displaywithout an intervening blank image (AWOB), alternate display with an intervening blank image (AWB), and side‐by‐side display (SSD), in terms of the perceptual sensitivity to image differences between Joint Photographic Experts Group 2000 (JPEG2000) compressed body CT images and their originals.

Methods:

A total of 50 body CT images obtained with five different scan protocols (5‐mm‐thick abdomen, 0.67‐mm‐thick abdomen, 5‐mm‐thick lung, 0.67‐mm‐thick lung, and 5‐mm‐thick low‐dose lung) were compressed to one of five compression ratios (reversible, 6:1, 8:1, 10:1, and 15:1) using JPEG2000 algorithm. The fidelity of the compressed images was visually assessed on a four‐grade scale independently by five radiologists using each of the three image comparison methods of AWOB, AWB, and SSD. The fidelity grading results for the 40 irreversibly compressed images were compared between the three image comparison methods using the Friedman tests withpost hoc Tukey tests. The number of image pairs with no perceptible difference was compared using the exact tests for paired proportions. The time required for the fidelity assessment for all of the 50 compressed images was also compared using the Friedman tests with post hoc Tukey tests.

Results:

For the 40 irreversibly compressed images, the fidelity grade was significantly lower for AWOB than for AWB or SSD ( for all readers); however, there was no significant difference between AWB and SSD (‐value range, 0.06–0.92). The percentage of image pairs with no perceptible difference tended to be smaller for AWOB than for AWB ( for all readers) or SSD ( for readers 1–3, for reader 4, and for reader 5). However, there was no significant difference between AWB and SSD (‐value range, ). For all of the 50 compressed images, the fidelity grading time significantly increased in the order of AWOB, SSD, and AWB.

Conclusions:

In assessing the image fidelity of JPEG2000 compressed body CT images, AWOB yields lower fidelity grade and requires less fidelity grading time than AWB or SSD, indicating that AWOB is most sensitive to image differences among of them.
A compensative model for the angle‐dependence of motion estimates in noninvasive vascular elastography
Authors: Mercure Elizabeth , Deprez Jean‐François , Fromageau Jérémie , Basset Olivier , Soulez Gilles , Cloutier Guy , Maurice Roch L.
Published: February 2011

Purpose:

Atherosclerosis of peripheral cerebral arteries can lead to stroke either by stenosis formation or plaque rupture. This pathology is initiated by the alteration of arterial wall mechanical properties shown to be assessable by ultrasound elastography. Recently, noninvasive vascular elastography (NIVE) was introduced for noninvasive imaging of the mechanical properties of superficial arteries as markers of vulnerable plaques. However, NIVE motion estimates are angle‐dependent, with optimal scanning angle being represented by the alignment of tissue motion with ultrasound beam orientation. The objective of this study was to introduce a model that compensates for such angle‐dependence in order to reduce the bias on strain estimates, namely, when investigating longitudinal vessel segments.

Methods:

The model is based on the Lagrangian speckle model estimator (LSME) because the LSME assesses the 2D‐deformation matrix required to compute the scanning angle.

Results:

Experiments on vessel‐mimicking phantoms indicated that such a model enables the estimation of scanning angle with less than 3‐degrees error. The method was also validatedin vivo in human carotid arteries where less than 4‐degrees error was observed. In both cases, the compensative model estimated the inclination angles with low variability.

Conclusion:

Angle‐dependence may be an important factor to consider in avoiding potentially distort clinical diagnoses. Results, reported in this article, suggest that the LSME‐based compensative model might be considered as a very interesting and promising clinical tool for NIVE applications.
Sensitivity of postplanning target and OAR coverage estimates to dosimetric margin distribution sampling parameters
Authors: Xu Huijun , Gordon J. James , Siebers Jeffrey V.
Published: February 2011

Purpose:

A dosimetric margin (DM) is the margin in a specified direction between a structure and a specified isodose surface, corresponding to a prescription or tolerance dose. The dosimetric margin distribution (DMD) is the distribution of DMs over all directions. Given a geometric uncertainty model, representing inter‐ or intrafraction setup uncertainties or internal organ motion, the DMD can be used to calculate coverage, which is the probability that a realized target or organ‐at‐risk (OAR) dose metric exceeds the corresponding prescription or tolerance dose. Postplanning coverage evaluation quantifies the percentage of uncertainties for which target and OAR structures meet their intended dose constraints. The goal of the present work is to evaluate coverage probabilities for 28 prostate treatment plans to determine DMD sampling parameters that ensure adequate accuracy for postplanning coverage estimates.

Methods:

Normally distributed interfraction setup uncertainties were applied to 28 plans for localized prostate cancer, with prescribed dose of 79.2 Gy and 10 mm clinical target volume to planning target volume (CTV‐to‐PTV) margins. Using angular or isotropic sampling techniques, dosimetric margins were determined for the CTV, bladder and rectum, assuming shift invariance of the dose distribution. For angular sampling, DMDs were sampled at fixed angular intervals (e.g., ). Isotropic samples were uniformly distributed on the unit sphere resulting in variable angular increments, but were calculated for the same number of sampling directions as angular DMDs, and accordingly characterized by the effective angular increment . In each direction, the DM was calculated by moving the structure in radial steps of size until the specified isodose was crossed. Coverage estimation accuracy was quantified as a function of the sampling parameters or and .

Results:

The accuracy of coverage estimates depends on angular and radial DMD sampling parameters or and , as well as the employed sampling technique. Target and OAR can be achieved with sampling parameters or , . Better accuracy (target and OAR ) can be achieved with or , . As the number of sampling points decreases, the isotropic sampling method maintains better accuracy than fixed angular sampling.

Conclusions:

Coverage estimates for post‐planning evaluation are essential since coverage values of targets and OARs often differ from the values implied by the static margin‐based plans. Finer sampling of the DMD enables more accurate assessment of the effect of geometric uncertainties on coverage estimates prior to treatment. DMD sampling with or and should be adequate for planning purposes.
Per‐beam, planar IMRT QA passing rates do not predict clinically relevant patient dose errors
Authors: Nelms Benjamin E. , Zhen Heming , Tomé Wolfgang A.
Published: February 2011

Purpose:

The purpose of this work is to determine the statistical correlation between per‐beam, planar IMRT QA passing rates and several clinically relevant, anatomy‐based dose errors for per‐patient IMRT QA. The intent is to assess the predictive power of a common conventional IMRT QA performance metric, the Gamma passing rate per beam.

Methods:

Ninety‐six unique data sets were created by inducing four types of dose errors in 24 clinical head and neck IMRT plans, each planned with 6 MV Varian 120‐leaf MLC linear accelerators using a commercial treatment planning system and step‐and‐shoot delivery. The error‐free beams/plans were used as “simulated measurements” (for generating the IMRT QA dose planes and the anatomy dose metrics) to compare to the corresponding data calculated by the error‐induced plans. The degree of the induced errors was tuned to mimic IMRT QA passing rates that are commonly achieved using conventional methods.

Results:

Analysis of clinical metrics (parotid mean doses, spinal cord max and, CTV , and larynx mean) vs IMRT QA Gamma analysis (3%/3 mm, 2/2, 1/1) showed that in all cases, there were only weak to moderate correlations (range of Pearson's ‐values: −0.295 to 0.653). Moreover, the moderate correlations actually had positive Pearson's ‐values (i.e., clinically relevant metric differences increased with increasing IMRT QA passing rate), indicating that some of the largest anatomy‐based dose differences occurred in the cases of high IMRT QA passing rates, which may be called “false negatives.” The results also show numerous instances of false positives or cases where low IMRT QA passing rates do not imply large errors in anatomy dose metrics. In none of the cases was there correlation consistent with high predictive power of planar IMRT passing rates, i.e., in none of the cases did high IMRT QA Gamma passing rates predict low errors in anatomy dose metrics or vice versa.

Conclusions:

There is a lack of correlation between conventional IMRT QA performance metrics (Gamma passing rates) and dose errors in anatomic regions‐of‐interest. The most common acceptance criteria and published actions levels therefore have insufficient, or at least unproven, predictive power for per‐patient IMRT QA.
A variable echo‐number method for estimating in MRI‐based polymer gel dosimetry
Authors: Watanabe Yoichi , Kubo Hitoshi
Published: February 2011

Purpose:

Spin‐spin relaxation rate is commonly used to quantify absorbed dose for magnetic resonance imaging (MRI)‐based polymer gel dosimetry. is estimated by applying a parameter fitting algorithm to a train of spin‐echo signals. However, a careless application of a large number of echoes can result in anomalous values because the echo signal intensity decreases to the background signal offset level for a long echo time. In this article, the authors proposed and evaluated a variable echo‐number (VAREC) method to remedy the problem.

Methods:

The VAREC algorithm uses only echo signals, whose intensities are greater than a preset threshold. Here, the threshold is defined as the standard deviation of Gaussian noise times a multiplier. The authors implemented three estimation methods in an in‐house program: The nonlinear least‐squares algorithm (NLLS), the VAREC method, and the maximum likelihood estimator with the Rician signal intensity distribution (MLE_R). Those methods were used to estimate the values of test phantoms with known values and BANG3‐type polymer gels, which were irradiated to 12 different doses ranging from 0 to 50 Gy. The values were measured by using a 32‐echo CPMG pulse sequence on 3 T MRI scanners. The values of the VAREC method were compared with those of NLLS and MLE_R.

Results:

The values of the NLLS method incorrectly decreased to the zero‐dose level for doses greater than 10 Gy. The values of the VAREC method with agreed with those of MLE_R within the measurement uncertainty. The uncertainties of the values were the smallest for or 3 among various values.

Conclusions:

The VAREC algorithm is simple, fast, and robust for the estimation. The authors recommend this method with or 3 for estimation using multispin echo MRI protocols.
Simplifying EPID dosimetry for IMRT treatment verification
Authors: Pecharromán‐Gallego R. , Mans Anton , Sonke Jan‐Jakob , Stroom Joep C. , Olaciregui‐Ruiz Ígor , van Herk Marcel , Mijnheer Ben J.
Published: February 2011

Purpose:

Electronic portal imaging devices (EPIDs) are increasingly used for IMRT dose verification, both pretreatment andin vivo. In this study, an earlier developed backprojection model has been modified to avoid the need for patient‐specific transmission measurements and, consequently, leads to a faster procedure.

Methods:

Currently, the transmission, an essential ingredient of the backprojection model, is estimated from the ratio of EPID measurements with and without a phantom/patient in the beam. Thus, an additional irradiation to obtain “open images” under the same conditions as the actual phantom/patient irradiation is required. However, by calculating the transmission of the phantom/patient in the direction of the beam instead of using open images, this extra measurement can be avoided. This was achieved by using a model that includes the effect of beam hardening and off‐axis dependence of the EPID response on photon beam spectral changes. The parameters in the model were empirically obtained by performing EPID measurements using polystyrene slab phantoms of different thickness in 6, 10, and 18 MV photon beams. A theoretical analysis to verify the sensitivity of the model with patient thickness changes was performed. The new model was finally applied for the analysis of EPID dose verification measurements of step‐and‐shoot IMRT treatments of head and neck, lung, breast, cervix, prostate, and rectum patients. All measurements were carried out using Elekta SL20i linear accelerators equipped with a hydrogenated amorphous silicon EPID, and the IMRT plans were made usingPINNACLE software (Philips Medical Systems).

Results:

The results showed generally good agreement with the dose determined using the old model applying the measured transmission. The average differences between EPID‐basedin vivo dose at the isocenter determined using either the new model for transmission and its measured value were , , and for 47 patients treated with 6, 10, and 18 MV IMRT beams, respectively. For the same group of patients, the differences in mean analysis (3% maximum dose, 3 mm) were , , and , respectively. For a subgroup of 11 patients, pretreatment verification was also performed, showing similar dose differences at the isocenter: , , and , with somewhat lower mean difference values: , , and , respectively. Clinical implementation of the new model would save 450 h/yr spent in measurement of open images.

Conclusions:

It can be concluded that calculating instead of measuring the transmission leads to differences in the isocenter dose generally smaller than 2% (2.6% for 6 MV photon beams forin vivo dose) and yielded only slightly higher ‐evaluation parameter values in planes through the isocenter. Hence, the new model is suitable for clinical implementation and measurement of open images can be omitted.
Ultrasound internal tattooing
Authors: Couture Olivier , Faivre Magalie , Pannacci Nicolas , Babataheri Avin , Servois Vincent , Tabeling Patrick , Tanter Mickael
Published: February 2011

Purpose:

The ability of remotely tagging tissues in a controlled and three‐dimensional manner during preoperative imaging could greatly help surgeons to identify targets for resection. The authors' objective is to selectively and noninvasively deposit markers under image guidance for such internal tattooing.

Methods:

This study describes the production of new ultrasound‐inducible droplets carrying large payloads of fluorescent markers and thein vivo proof of concept of their remote and controlled deposition via focused ultrasound. The droplets are monodispersed multiple emulsions produced in a microfluidic system, consisting of aqueous fluorescein in perfluorocarbon in water. Their conversion (either by vaporization or cavitation) is performed remotely using a clinical ultrasonic imaging probe.

Results:

When submitted to 5 MHz imaging pulses, the droplets vaporizein vitro at 1.4 MPa peak‐negative pressure and eject their content. After several seconds, a brightly fluorescent spot (0.5 mm diameter) is observed at the focus of the transducer. Experiments in the chorioallantoique membrane of chicken eggs and chicken embryo demonstrate that the spot is stable and is easily seen by naked eye.

Conclusions:

These ultrasound‐inducible multiple emulsions could be used to deliver large amounts of contrast agents, chemotherapy, and genetic materialsin vivo using a conventional ultrasound scanner.
Acoustical scattering by multilayer spherical elastic scatterer containing electrorheological layer
Authors: Cai Liang-Wu , Dacol Dacio K. , Orris Gregory J. , Calvo David C. , Nicholas Michael
Published: February 2011

A computational procedure for analyzing acoustical scattering by multilayer concentric spherical scatterers having an arbitrary mixture of acoustic and elastic materials is proposed. The procedure is then used to analyze the scattering by a spherical scatterer consisting of a solid shell and a solid core encasing an electrorheological (ER) fluid layer, and the tunability in the scattering characteristics afforded by the ER layer is explored numerically. Tunable scatterers with two different ER fluids are analyzed. One, corn starch in peanut oil, shows that a significant increase in scattering cross-section is possible in moderate frequencies. Another, fine poly-methyl methacrylate (PMMA) beads in dodecane, shows only slight change in scattering cross-sections overall. But, when the shell is thin, a noticeable local resonance peak can appear near ka = 1, and this resonance can be turned on or off by the external electric field.
Common humpback whale (Megaptera novaeangliae) sound types for passive acoustic monitoring
Authors: Stimpert Alison K. , Au Whitlow W. L. , Parks Susan E. , Hurst Thomas , Wiley David N.
Published: February 2011

Humpback whales (Megaptera novaeangliae) are one of several baleen whale species in the Northwest Atlantic that coexist with vessel traffic and anthropogenic noise. Passive acoustic monitoring strategies can be used in conservation management, but the first step toward understanding the acoustic behavior of a species is a good description of its acoustic repertoire. Digital acoustic tags (DTAGs) were placed on humpback whales in the Stellwagen Bank National Marine Sanctuary to record and describe the non-song sounds being produced in conjunction with foraging activities. Peak frequencies of sounds were generally less than 1 kHz, but ranged as high as 6 kHz, and sounds were generally less than 1 s in duration. Cluster analysis distilled the dataset into eight groups of sounds with similar acoustic properties. The two most stereotyped and distinctive types (“wops” and “grunts”) were also identified aurally as candidates for use in passive acoustic monitoring. This identification of two of the most common sound types will be useful for moving forward conservation efforts on this Northwest Atlantic feeding ground.
Multiple scattering by cylinders immersed in fluid: High order approximations for the effective wavenumbers
Authors: Norris Andrew N. , Conoir Jean-Marc
Published: February 2011

Acoustic wave propagation in a fluid with a random assortment of identical cylindrical scatterers is considered. While the leading order correction to the effective wavenumber of the coherent wave is well established at dilute areal density (n0) of scatterers, in this paper the higher order dependence of the coherent wavenumber on n0 is developed in several directions. Starting from the quasi-crystalline approximation (QCA) a consistent method is described for continuing the Linton and Martin formula, which is second order in n0, to higher orders. Explicit formulas are provided for corrections to the effective wavenumber up to O (n04). Then, using the QCA theory as a basis, generalized self-consistent schemes are developed and compared with self-consistent schemes using other dynamic effective medium theories. It is shown that the Linton and Martin formula provides a closed self-consistent scheme, unlike other approaches.
Toneburst-evoked auditory brainstem response in a leopard seal, Hydrurga leptonyx
Authors: Tripovich J. S. , Purdy S. C. , Hogg C. , Rogers T. L.
Published: February 2011

Toneburst-evoked auditory brainstem responses (ABRs) were recorded in a captive subadult male leopard seal. Three frequencies from 1 to 4 kHz were tested at sound levels from 68 to 122 dB peak equivalent sound pressure level (peSPL). Results illustrate brainstem activity within the 1–4 kHz range, with better hearing sensitivity at 4 kHz. As is seen in human ABR, only wave V is reliably identified at the lower stimulus intensities. Wave V is present down to levels of 82 dB peSPL in the right ear and 92 dB peSPL in the left ear at 4 kHz. Further investigations testing a wider frequency range on seals of various sex and age classes are required to conclusively report on the hearing range and sensitivity in this species.
Wind-generated ambient noise in a topographically isolated basin: A pre-industrial era proxy
Authors: Reeder D. Benjamin , Sheffield Edmond S. , Mach Susan M.
Published: February 2011

During the mid-1980s, calibrated measurements of ambient noise and wind speed were made in the Tongue of the Ocean in the Bahamas to quantify the spectra and statistics of wind-generated noise. This deep basin is topographically isolated from the Atlantic Ocean and, therefore, largely acoustically decoupled from the Atlantic Ocean deep sound channel. The quantitative effects of contaminating (non-surface wind-generated) noise sources within the basin were eliminated by careful measurement and robust statistical analysis methodologies. Above 500 Hz, the spectral slopes are approximately −5 dB per octave and independent of wind speed. Below 500 Hz, the ambient noise is no longer a linear function of wind speed. Below 100 Hz and for wind speeds greater than 18.5 knots (kt), the ambient noise is independent of frequency. The minimum observed ambient noise level falls 13 dB below Urick’s “light shipping” level at 30 Hz and 2–5 dB below Wenz’s sea state zero level through the wind-dominated portion of the spectrum. The basin’s geographical isolation and the rigorous measurement and analysis methodologies employed make this two-decade-old data set a reasonable and justified proxy for pre-industrial era ocean noise levels in the 20 Hz to 20 kHz frequency band.
Interpretation of multi-frequency acoustic data: Effects of fish orientation
Authors: Jech J. Michael
Published: February 2011

One goal of fisheries acoustics is to develop objective classification or identification methods to automate allocation of acoustic backscatter to species. Classification schemes rely on consistent relationships for successful apportionment of acoustic backscatter to species. A method is developed that compares frequency-dependent volume backscatter from an acoustical survey of Atlantic herring (Clupea harengus) to investigate the potential for classifying herring. Predicted backscattering patterns by a Kirchhoff-ray approximation are used to explain the observed relationships and evaluate the potential for classification of multi-frequency data. Combining predicted backscatter with observations of the frequency-dependent volume backscatter gave approximately 40% classification success, which is not sufficient for survey purposes. However, this method highlighted potential consequences that fish orientation may have on classification schemes and density and abundance estimates. This method of comparing multi-frequency volume backscatter appears to be beneficial for detecting behavioral changes by groups of fish, which may be used to select target strength values for density or abundance estimates. Utilizing predicted target strengths from numerical or analytical solutions or approximations, appropriate target strengths could be selected and would provide more accurate estimates of fish density and abundance.
Material selection for acoustic radiators that are light and stiff
Authors: Porter S. P. , Markley D. C. , Van Tol D. J. , Meyer R. J.
Published: February 2011

The headmass is a key element in tonpilz transducer design. As an acoustic radiator, a successful headmass must be built from a material that is both light and stiff. To assess the suitability of ceramics for this application, the authors used the mechanical properties of candidate materials to perform a theoretical comparison based on the flexural behavior of square plates. Although not a comprehensive metric for identifying the best headmass materials, the headmass flexure may be usefully employed as a first-level selection criteria. A software routine based on thin plate and thick plate theory was created to evaluate the flexural behavior in candidate materials.
Experimental study of a smart foam sound absorber
Authors: Leroy Pierre , Berry Alain , Herzog Philippe , Atalla Noureddine
Published: February 2011

This article presents the experimental implementation and results of a hybrid passive/active absorber (smart foam) made up from the combination of a passive absorbent (foam) and a curved polyvinylidene fluoride (PVDF) film actuator bonded to the rear surface of the foam. Various smart foam prototypes were built and tested in active absorption experiments conducted in an impedance tube under plane wave propagation condition at frequencies between 100 and 1500 Hz. Three control cases were tested. The first case used a fixed controller derived in the frequency domain from estimations of the primary disturbance at a directive microphone position in the tube and the transfer function between the control PVDF and the directive microphone. The two other cases used an adaptive time-domain feedforward controller to absorb either a single-frequency incident wave or a broadband incident wave. The non-linearity of the smart foams and the causality constraint were identified to be important factors influencing active control performance. The effectiveness of the various smart foam prototypes is discussed in terms of the active and passive absorption coefficients as well as the control voltage of the PVDF actuator normalized by the incident sound pressure.
Fluctuating arrivals of short-range acoustic data
Authors: Park Cheolsoo , Seong Woojae , Gerstoft Peter , Hodgkiss William S.
Published: February 2011

Geoacoustic inversion using fluctuating signal observations can be challenging. The origin of these fluctuations needs to be understood so the signals can be used appropriately. A set of experiments [Tang et al., Oceanogr. 20(4), 156–167 (2007)] was carried out in shallow water near the New Jersey shelf break in summer 2006. Significant fluctuations in the direct path and surface-reflected arrivals of short-range chirp transmissions (1.1–2.9 kHz) were observed on a vertical line array. This paper explains the origin of these signal fluctuations through analysis of the arrival amplitudes. It is shown that the strong thermocline combined with an oscillating source motion due to ocean surface waves results in the signal fluctuations.
Green’s function of radial inhomogeneous spheres excited by internal sources
Authors: Zouros Grigorios P. , Kokkorakis Gerassimos C.
Published: February 2011

Green’s function in the interior of penetrable bodies with inhomogeneous compressibility by sources placed inside them is evaluated through a Schwinger–Lippmann volume integral equation. In the case of a radial inhomogeneous sphere, the radial part of the unknown Green’s function can be expanded in a double Dini’s series, which allows analytical evaluation of the involved cumbersome integrals. The simple case treated here can be extended to more difficult situations involving inhomogeneous density as well as to the corresponding electromagnetic or elastic problem. Finally, numerical results are given for various inhomogeneous compressibility distributions.
Detecting high-frequency hearing loss with click-evoked otoacoustic emissions
Authors: Keefe Douglas H. , Goodman Shawn S. , Ellison John C. , Fitzpatrick Denis F. , Gorga Michael P.
Published: February 2011

In contrast to clinical click-evoked otoacoustic emission (CEOAE) tests that are inaccurate above 4–5 kHz, a research procedure measured CEOAEs up to 16 kHz in 446 ears and predicted the presence/absence of a sensorineural hearing loss. The behavioral threshold test that served as a reference to evaluate CEOAE test accuracy used a yes–no task in a maximum-likelihood adaptive procedure. This test was highly efficient between 0.5 and 12.7 kHz: Thresholds measured in 2 min per frequency had a median standard deviation (SD) of 1.2–1.5 dB across subjects. CEOAE test performance was assessed by the area under the receiver operating characteristic curve (AUC). The mean AUC from 1 to 10 kHz was 0.90 (SD = 0.016). AUC decreased to 0.86 at 12.7 kHz and to 0.7 at 0.5 and 16 kHz, possibly due in part to insufficient stimulus levels. Between 1 and 12.7 kHz, the medians of the magnitude difference in CEOAEs and in behavioral thresholds were <4 dB. The improved CEOAE test performance above 4–5 kHz was due to retaining the portion of the CEOAE response with latencies as short as 0.3 ms. Results have potential clinical significance in predicting hearing status from at least 1 to 10 kHz using a single CEOAE response.
Observation and analysis of in vivo vocal fold tissue instabilities produced by nonlinear source-filter coupling: A case study
Authors: Zañartu Matías , Mehta Daryush D. , Ho Julio C. , Wodicka George R. , Hillman Robert E.
Published: February 2011

Different source-related factors can lead to vocal fold instabilities and bifurcations referred to as voice breaks. Nonlinear coupling in phonation suggests that changes in acoustic loading can also be responsible for this unstable behavior. However, no in vivo visualization of tissue motion during these acoustically induced instabilities has been reported. Simultaneous recordings of laryngeal high-speed videoendoscopy, acoustics, aerodynamics, electroglottography, and neck skin acceleration are obtained from a participant consistently exhibiting voice breaks during pitch glide maneuvers. Results suggest that acoustically induced and source-induced instabilities can be distinguished at the tissue level. Differences in vibratory patterns are described through kymography and phonovibrography; measures of glottal area, open/speed quotient, and amplitude/phase asymmetry; and empirical orthogonal function decomposition. Acoustically induced tissue instabilities appear abruptly and exhibit irregular vocal fold motion after the bifurcation point, whereas source-induced ones show a smoother transition. These observations are also reflected in the acoustic and acceleration signals. Added aperiodicity is observed after the acoustically induced break, and harmonic changes appear prior to the bifurcation for the source-induced break. Both types of breaks appear to be subcritical bifurcations due to the presence of hysteresis and amplitude changes after the frequency jumps. These results are consistent with previous studies and the nonlinear source-filter coupling theory.
A measurement model for general noise reaction in response to aircraft noise
Authors: Kroesen Maarten , Schreckenberg Dirk
Published: February 2011

In this paper a measurement model for general noise reaction (GNR) in response to aircraft noise is developed to assess the performance of aircraft noise annoyance and a direct measure of general reaction as indicators of this concept. For this purpose GNR is conceptualized as a superordinate latent construct underlying particular manifestations. This conceptualization is empirically tested through estimation of a second-order factor model. Data from a community survey at Frankfurt Airport are used for this purpose (N = 2206). The data fit the hypothesized factor structure well and support the conceptualization of GNR as a superordinate construct. It is concluded that noise annoyance and a direct measure of general reaction to noise capture a large part of the negative feelings and emotions in response to aircraft noise but are unable to capture all relevant variance. The paper concludes with recommendations for the valid measurement of community reaction and several directions for further research.
Mathematically trivial control of sound using a parametric beam focusing source
Authors: Tanaka Nobuo , Tanaka Motoki
Published: February 2011

By exploiting a case regarded as trivial, this paper presents global active noise control using a parametric beam focusing source (PBFS). As with a dipole model, one is used for a primary sound source and the other for a control sound source, the control effect for minimizing a total acoustic power depends on the distance between the two. When the distance becomes zero, the total acoustic power becomes null, hence nothing less than a trivial case. Because of the constraints in practice, there exist difficulties in placing a control source close enough to a primary source. However, by projecting a sound beam of a parametric array loudspeaker onto the target sound source (primary source), a virtual sound source may be created on the target sound source, thereby enabling the collocation of the sources. In order to further ensure feasibility of the trivial case, a PBFS is then introduced in an effort to meet the size of the two sources. Reflected sound wave of the PBFS, which is tantamount to the virtual sound source output, aims to suppress the primary sound. Finally, a numerical analysis as well as an experiment is conducted, verifying the validity of the proposed methodology.
Test of the movement expansion model: Anticipatory vowel lip protrusion and constriction in French and English speakers
Authors: Noiray Aude , Cathiard Marie-Agnès , Ménard Lucie , Abry Christian
Published: February 2011

The modeling of anticipatory coarticulation has been the subject of longstanding debates for more than 40 yr. Empirical investigations in the articulatory domain have converged toward two extreme modeling approaches: a maximal anticipation behavior (Look-ahead model) or a fixed pattern (Time-locked model). However, empirical support for any of these models has been hardly conclusive, both within and across languages. The present study tested the temporal organization of vocalic anticipatory coarticulation of the rounding feature from [i] to [u] transitions for adult speakers of American English and Canadian French. Articulatory data were synchronously recorded using an Optotrak for lip protrusion and a dedicated Lip-Shape-Tracking-System for lip constriction. Results show that (i) protrusion is an inconsistent parameter for tracking anticipatory rounding gestures across individuals, more specifically in English; (ii) labial constriction (between-lip area) is a more reliable correlate, allowing for the description of vocalic rounding in both languages; (iii) when tested on the constriction component, speakers show a lawful anticipatory behavior expanding linearly as the intervocalic consonant interval increases from 0 to 5 consonants. The Movement Expansion Model from Abry and Lallouache [(1995a) Bul. de la Comm. Parlée 3, 85–99; (1995b) Proceedings of ICPHS 4, 152–155.] predicted such a regular behavior, i.e., a lawful variability with a speaker-specific expansion rate, which is not language-specific.
The role of temporal fine structure information for the low pitch of high-frequency complex tones
Authors: Santurette Sébastien , Dau Torsten
Published: February 2011

The fused low pitch evoked by complex tones containing only unresolved high-frequency components demonstrates the ability of the human auditory system to extract pitch using a temporal mechanism in the absence of spectral cues. However, the temporal features used by such a mechanism have been a matter of debate. For stimuli with components lying exclusively in high-frequency spectral regions, the slowly varying temporal envelope of sounds is often assumed to be the only information contained in auditory temporal representations, and it has remained controversial to what extent the fast amplitude fluctuations, or temporal fine structure (TFS), of the conveyed signal can be processed. Using a pitch matching paradigm, the present study found that the low pitch of inharmonic transposed tones with unresolved components was consistent with the timing between the most prominent TFS maxima in their waveforms, rather than envelope maxima. Moreover, envelope cues did not take over as the absolute frequency or rank of the lowest component was raised and TFS cues thus became less effective. Instead, the low pitch became less salient. This suggests that complex pitch perception does not rely on envelope coding as such, and that TFS representation might persist at higher frequencies than previously thought.
Characterizing auditory processing and perception in individual listeners with sensorineural hearing loss
Authors: Jepsen Morten L. , Dau Torsten
Published: February 2011

This study considered consequences of sensorineural hearing loss in ten listeners. The characterization of individual hearing loss was based on psychoacoustic data addressing audiometric pure-tone sensitivity, cochlear compression, frequency selectivity, temporal resolution, and intensity discrimination. In the experiments it was found that listeners with comparable audiograms can show very different results in the supra-threshold measures. In an attempt to account for the observed individual data, a model of auditory signal processing and perception [Jepsen et al., J. Acoust. Soc. Am. 124, 422–438 (2008)] was used as a framework. The parameters of the cochlear processing stage of the model were adjusted to account for behaviorally estimated individual basilar-membrane input-output functions and the audiogram, from which the amounts of inner hair-cell and outer hair-cell losses were estimated as a function of frequency. All other model parameters were left unchanged. The predictions showed a reasonably good agreement with the measured individual data in the frequency selectivity and forward masking conditions while the variation of intensity discrimination thresholds across listeners was underestimated by the model. The model and the associated parameters for individual hearing-impaired listeners might be useful for investigating effects of individual hearing impairment in more complex conditions, such as speech intelligibility in noise.
Investigations on the balloon as an impulse source
Authors: Pätynen Jukka , Katz Brian F.G. , Lokki Tapio
Published: February 2011

Measurements of impulses produced by bursting balloons are presented. Various sizes of balloons were popped with a mechanical device in an anechoic chamber and recorded with a spherical microphone array. The power responses and directivity of the balloons are analyzed. Results indicate that power responses have two emphasized frequencies which depend on balloon size and inflation level. Larger balloons radiated more energy and higher inflation levels resulted in stronger high frequency content. Balloon directivity patterns are stable over repetitions. However, balloons do not radiate omnidirectionally. The degree of omnidirectionality improves with balloon size and for midrange frequencies.
Separating overlapping click trains originating from multiple individuals in echolocation recordings
Authors: Starkhammar Josefin , Nilsson Johan , Amundin Mats , Kuczaj Stan A. , Almqvist Monica , Persson Hans W.
Published: February 2011

Recordings of the acoustic activity of free-swimming groups of echolocating dolphins increase the likelihood of collecting overlapping click trains, originating from multiple individuals, in the same set of data. In order to evaluate the click properties of each individual based on such recordings it is necessary to identify which clicks originate from which animal. This paper suggests a computationally efficient strategy to separate overlapping click trains originating from multiple free-swimming bottlenose dolphins, enabling echolocation analysis at an individual level on several animals. This technique is based on sequential matching of the frequency spectra of successive clicks. The clicks are grouped together as individual click trains if the correlation coefficients between clicks are higher than a pre-set threshold level. The robustness of the algorithm is tested by adding artificially generated white Gaussian noise and comparing the results with other comparable commonly used methods based on inter-click intervals, centroid frequencies, and amplitude levels. The described method is applicable to a variety of experimental and observational contexts, e.g., those regarding echolocation development of calves, the hypothesized acoustic “etiquette” among dolphins when investigating the same object, and the possible occurrence of eavesdropping in large dolphin pods.