bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonlinear acoustic pulse propagation in dispersive sediments using fractional loss operators
Authors: Maestas Joseph T.
Published: November 2013

The nonlinear progressive wave equation (NPE) is a time-domain formulation of Euler’s fluid equations designed to model low-angle wave propagation using a wave-following computational domain [ McDonald et al., J. Acoust. Soc. Am. 81]. The wave-following frame of reference permits the simulation of long-range propagation that is useful in modeling the effects of blast waves in the ocean waveguide. However, the current model does not take into account sediment attenuation, a feature necessary for accurately describing sound propagation into and out of the ocean sediment. These attenuating, dispersive sediments are naturally captured with linear, frequency-domain solutions through use of complex wavespeeds, but a comparable treatment is nontrivial in the time-domain. Recent developments in fractional loss operator methods allow for frequency-dependent loss mechanisms to be applied in the time-domain providing physically realistic results [Prieur et al., J. Acoust. Soc. Am. 130]. Using these approaches, the governing equations used to describe the NPE are modified to use fractional derivatives in order to develop a fractional NPE. The updated model is then benchmarked against a Fourier-transformed parabolic equation solution for the linear case using various sediment attenuation factors.
Volume scattering and reverberation in shallow water: A simplified modeling approach
Authors: Ivakin Anatoliy
Published: November 2013

A simplified physics-based approach is described that allows significantly faster yet reasonably accurate estimations of volume reverberation in complex shallow water environments. An integral expression is presented for scattering intensity with a factorized integrand comprised of two kernels, the double propagator and local volume scattering coefficient. The propagator describes the local intensity and can be calculated using available models, such as PE, normal modes, or ray approximations. The scattering kernel can be specified using available volume scattering models for continuous or discrete heterogeneity of sea-water column and seabed caused by spatial fluctuations of compressibility and density, or randomly distributed discrete targets, such as bubbles, fish, shells, and others. The approach is more general than and can be used for verification of existing reverberation models. For instance, calculation of bottom reverberation is not based on using the equivalent surface scattering strength (although considers it as a particular case). Numerical examples for shallow water reverberation time series, based on a PE propagation model, are presented to estimate potential contributions of different mechanisms of scattering. The estimations provide a comparison of relative contributions of scatterers with the same scattering strengths but located at different depths in water column or in the sediment. [Work supported by the US Office of Naval Research.]
Computation of the field of coupled modes using split-step algorithm
Authors: Maltsev Nikolai
Published: November 2013

Euler equations in the form ∂F/∂x = A(x,z)F where 2 × 2 matrix A has elements A11 = 0, A22 = 0, A12 = iωρ, A21 = 1/(iωρ)(−▵yz + (▿yz lnρ, ▿yz) − (ω/c)2) where F = (P(r), u(r))T are sound pressure and horizontal velocity, c(r), ρ(r) -sound speed and density, ω = 2 πf—angular frequency and ▵yz,▿yz are Laplace operator and gradient in the plane (y,z), has first order with respect to x and can be integrated by split step algorithm F(x + d) = exp(0.5A(x + d)d)exp(0.5A(x)d)F(x) + O(d3) using local modes for computation of exponential operators. Integration is performed in one direction but, due to the structure of normal modes of operator A, allows estimate energy reflected back on every integration step. Different examples, including irregular waveguides with ideal boundaries and Pekeris style guide with variable depth are presented.
Equal loudness contours and possible weighting functions for pinnipeds
Authors: Reichmuth Colleen
Published: November 2013

The idea of developing frequency weighting functions for marine mammals has received considerable attention recently because such functions can determine the relevant bandwidth for noise exposure assessments, and because they take differences in auditory sensitivity between species into account when identifying acoustic risks. However, such weighting functions are difficult to establish for nonhumans as they rely on equal loudness relationships that are subjective. Equal auditory reaction times may serve as a proxy for equal loudness judgments. For this experiment, we measured frequency-specific latency-intensity (L-I) functions for one California sea lion and one harbor seal with tones that were + 0, + 2, + 4, + 6, + 10, + 20, + 30, and + 40 dB re: sensation level (SL). The L-I plots were reliably fit with a power function to enable the determination of sound pressure levels corresponding to discrete latency values for each subject at each frequency. From these data, equal latency contours were drawn to describe differential auditory sensitivity as a function of frequency. The weighting functions derived from these contours are less conservative than the currently proposed “m”-weighting function for marine mammals, and may be more reliable than the alternative inverted audiogram approach. [Work supported by ONR.]
Psychophysical studies of hearing in sea otters (Enhydra lutris)
Authors: Ghoul Asila , Reichmuth Colleen
Published: November 2013

The sensory biology of sea otters is of special interest, given their amphibious nature and their recent evolutionary transition from land to sea. However, little is known about the acoustic sense of sea otters, including sensitivity to airborne and underwater sound. In this study, we sought to obtain direct measures of auditory function. We trained an adult-male southern sea otter to participate in audiometric testing in an acoustic chamber and an acoustically mapped pool. We used a psychoacoustic method of limits to determine absolute auditory thresholds in air and under water across the hearing range. In addition to obtaining aerial and underwater audiograms, we also evaluated hearing in the presence of noise. The otter’s aerial hearing closely resembled that of a sea lion, and showed reduced sensitivity to high-frequency (>22 kHz) and low-frequency (<2 kHz) sounds relative to terrestrial mustelids. Under water, hearing was less sensitive than sea lions and other pinnipeds, especially at frequencies below 1 kHz. Critical ratios were >10 dB above those measured in pinnipeds, indicating that sea otters are not especially well-adapted for extracting acoustic signals from noise. These data suggest that evolutionary changes in hearing are secondary to other adaptations for semi-aquatic living.
Explanation of the loudness and other features of cicada sounds
Authors: Hughes Derke R. , Pierce Allan D. , Katz Richard A. , Koch Robert M.
Published: November 2013

A quantitative explanation is given of features of noise emitted by cicadas (classed as the loudest of all insects). Microphone data shows sounds are emitted in a sequence of closely spaced tone bursts. Listeners do not perceive the individual pulses because of the finite integration time of the ear. The principal sound radiators are two platelets referred to as tymbals, which vibrate after being struck by ribs that have undergone buckling. The energy of each sound pulse is initially stored in tensed muscles and is initially released via buckling into the kinetic energy of ribs, which strike the tymbals in a manner similar to that of a drumstick striking a drum. The tymbals “ring” at a frequency controlled by the mass of the tymbals and the springiness of the air cavity within the abdomen of the cicada. The wavelengths of the radiated sound are much larger than the tymbal radii but comparable to the overall dimensions of the cicada. The detailed theory explains the radiation pattern of the sound radiation, the amplitude of the sound, the number of cycles in each pulse, the radiation damping of the tymbal vibrations, and why the cicada is such an efficient radiator of sound.
Temporal patterns in echolocation and cave use by Guam Swiftlets (Aerodramus bartschi) in native and introduced habitat
Authors: Titmus Andrew J. , Rudd Alexis B. , Brindock Kevin M. , Lammers Marc O. , Au Whitlow
Published: November 2013

The Mariana Swiftlet (Aerodramus bartschi) is a federally listed endangered species of is native to Guam and the Marianas Islands. There is also a small, introduced population of Marianas Swiftlets on the island of Oahu, Hawaii. The nesting cave in Oahu is a small tunnel built for agricultural irrigation. Marianas swiftlets live in caves, which they navigate using echolocation clicks. Ecological Acoustical Recorders (EARs) were modified with a omni-directional microphone with a flat frequency response and −63 dB sensitivity for bird recordings. Data were recorded at a sample rate of 80,000 and a duty cycle of 30 s of recording every 5 min. BEARs (Bird EARs) were placed in swiftlet caves on Oahu, Hawaii, and Guam where they recorded for between five and fifteen days. Swiftlet clicks were detected using Ishmael’s energy sum detector. Temporal patterns of clicking were analyzed and compared between the two sites and correlated with environmental data over the recording period to determine effects of sub-optimal nesting habitat and changed weather patterns on the Oahu population compared to the native population in Guam.
Static and dynamic control of emission beamwidth in horseshoe bats
Authors: Gupta Anupam Kumar , He Weikei , Webster Dane , Müller Rolf
Published: November 2013

Horseshoe bats (family Rhinolophidae) emit their ultrasonic biosonar pulses nasally with their nostrils surrounded by baffle structures known as “noseleaves.” The noseleaves are often characterized by intricate local shape details such as flaps, ridges, or furrows. Furthermore, some of these structures are capable of undergoing non-rigid shape changes over time. One part of the horseshoe bat noseleaf that has both static local shape features as well as a time dynamics is the lancet, a vertical projection on the top of the noseleaf. The most striking static shape features of the lancet are half-open cavities (furrows) and the most obvious in-vivo motion of the lancet is a rotation in the distal-proximal about the base of the lancet. In the present work, the acoustic effects of the furrows and the distal-proximal rotation of the lancet were studied in three individuals of the Greater Horseshoe bat (Rhinolophus ferrumequinum) using numerical methods. The lancet furrows were always found to act as beam-focusing devices irrespective of lancet rotation. The acoustic effect of forward lancet rotation within the range seen in bats (tested angles 0°, 5°, 10°) was always a significant widening of the beam.
Ultrasound velocity mapping with Lorentz force hydrophone
Authors: Grasland-Mongrain Pol , Gilles Bruno , Mari Jean-Martial , Roussel Benjamin , Poizat Adrien , Chapelon Jean-Yves , Lafon Cyril
Published: November 2013

In previous work [Grasland-Mongrain et al. 2013], a Lorentz force hydrophone consisting of a cylindrical arrangement of magnets around a thin metallic wire has been presented. An ultrasonic wave vibrates the wire inside a magnetic field, which induces an electrical current. The ultrasound velocity map is then tomographically reconstructed by recording the current amplitude after translation and rotation of the wire. A hydrodynamic model provides a relationship between the velocity and the measured tension. Wire tension influence, electrical output characteristics, frequency response, sensitivity, directionality, and robustness to cavitation were characterized. A multi-wires hydrophone was also fabricated and tested. Results show that tension of the wire has negligible influence on the signal. No peak of electrical impedance was observed from 0.15 to 10 MHz. The signal was linear over pressure from 50 kPa to 15 MPa. The hydrophone was robust even when cavitation activity occurred. The directivity is explained with the Lorentz force expression. The multi-wire hydrophone could work only at low frequencies. Such hydrophone could be of interest for high intensity acoustic field characterization.
Comparison of invasive and non-invasive methods of measuring high intensity acoustic fields
Authors: Zanelli Claudio I. , Howard Samuel M. , Giridhar Dushyanth
Published: November 2013

We present two methods of characterizing high intensity acoustic fields, namely, a non-invasive Schlieren method, and an invasive fiber-optic based one. The instant display makes the Schlieren method very attractive, although because it is a projection method it does not convey all the information available by the more localized sampling provided by the optical fiber. Numerical comparisons as well as the limitations of each method are described in the context of therapeutic ultrasound applications.
Acoustic characterization and assessment of renal injury with a broad focal width electrohydraulic lithotripter
Authors: Pishchalnikov Yuri A. , McAteer James A. , Connors Bret A. , Handa Rajash K. , Lingeman James E. , Evan Andrew P.
Published: November 2013

This study provides an independent assessment of a novel lithotripter (LG-380, Tissue Regeneration Technologies), marketed as having a long-life self-adjusting spark gap electrode and producing a low-pressure, broad-focal-zone acoustic field. For acoustic characterization we coupled the therapy head of the lithotripter to a water tank and mapped the field using a fiber-optic hydrophone (FOPH-500, RP Acoustics). At the target point of the lithotripter, the peak positive pressure (P +) remained relatively stable (~19±5 MPa at power level 9) during the 6000 shock waves (SWs) lifetime of the electrode. The position of maximum P + (~35 MPa at PL9) was 35mm distal to target point and shifted progressively toward the therapy head as the electrode aged, reaching the target point (while reducing to P + ~20 MPa) after ~5000 SWs. This was likely due to a slight movement in position of the self-adjusting spark gap—changing the focus of the shock wave and the dimensions of the focal volume of the lithotripter. Kidney injury was assessed using an established pig model by routine measures of renal function and quantitation of lesion size. Simulated clinical treatments (3000 SWs dose) damaged <0.1% functional renal volume, suggesting minimal potential for adverse effects with low-pressure broad-focal-zone lithotripters. [NIH DK43881.]
Effect of ex vivo body wall on lithotripter shock waves
Authors: Li Guangyan , McAteer James A. , Williams James C.
Published: November 2013

Current understanding of mechanisms of shock wave (SW) action in shock wave lithotripsy comes almost entirely from laboratory testing. Past attempts to characterize lithotripter SWs in vivo have been hindered by difficulties in hydrophone alignment and physical constraints precluding precise mapping of the acoustic field. We adopted an ex vivo approach in which full-thickness segments of pig abdominal wall were secured against the inside surface of the Mylar acoustic window of a water-filled test tank coupled to a Dornier Compact-S lithotripter. A fiber-optic probe hydrophone was used to measure SW pressures and map the field in 2 mm steps in the focal plane. Peak positive pressure (P +) on axis was attenuated roughly proportional to tissue thickness (6.1% per cm, ~40% for a 5–6 cm body wall). Negative pressure (P−) was less affected. Shock rise time was unchanged (~18–20 ns). Although irregularities in tissue thickness affected SW focusing, step-wise mapping of the field showed no effect of the body wall on focal width (~6 mm with or without tissue). These findings suggest that apart from attenuation, the characteristics of the acoustic field for SWs passing through the body wall are remarkably similar to values collected in the free field. [NIH-DK43881.]
Scattering of high-intensity focused ultrasound by the ribs: Constrained optimization with a complex surface impedance boundary condition
Authors: Gelat Pierre , ter Haar Gail , Saffari Nader
Published: November 2013

One of the challenges of trans-rib high-intensity focused ultrasound (HIFU) treatment is the need to transmit sufficient energy through the ribcage to ablate tissue whilst minimizing the formation of side lobes, and sparing healthy tissue. Ribs strongly absorb and reflect ultrasound. This may result in overheating of bone and overlying tissue during treatment, leading to skin burns. Successful treatment of a patient with tumors of the liver or the pancreas therefore requires a thorough understanding of the way acoustic and thermal energy is deposited. A boundary element approach was developed to predict the field of a multi-element HIFU array scattered by human ribs in 3D. This forward model has been reformulated as a constrained least squares optimization problem where the velocity of each individual element on the array is an optimization variable. A locally reacting complex surface impedance condition at the surface of the ribs has been implemented. The methodology has been tested at an excitation frequency of 1 MHz on a spherical section multi-element array and a total of six array-rib configurations have been investigated. The results were compared against other focusing and rib-sparing approaches, demonstrating the efficacy and flexibility of the constrained optimization approach.
Simulation of diagnostic ultrasound imaging with the fast nearfield method
Authors: Zhu Yi , Beard Peter B. , McGough Robert J.
Published: November 2013

Software for simulating diagnostic ultrasound imaging with the fast nearfield method is now available in FOCUS (http://www.egr.msu.edu/~fultras-web). The implementation of ultrasound imaging simulations in FOCUS first decomposes the excitation pulse into two shorter pulses that, when convolved together, are equivalent to the original excitation pulse. These two shorter pulses are applied to the transmit and receive apertures, reciprocity is applied to the receive aperture, and then the results of the intermediate pressure calculations are convolved to obtain the simulated pulse-echo signal. Simulation results using point scatterers are compared to Field II (http://field-ii.dk/) for simulations with a linear phased array. Results show that FOCUS achieves equal or smaller errors in less time than Field II, and the FOCUS results require much smaller sampling frequencies. The FOCUS results are achieved with an analytically equivalent algorithm that avoids aliasing problems by calculating pressures with the fast nearfield method combined with time-space decomposition. To further improve the efficiency of the imaging simulation in FOCUS, intermediate signals are computed, stored, and re-used. Ongoing efforts to incorporate new features into ultrasound imaging simulations with FOCUS will also be discussed. [This work was supported in part by NIH Grant R01 EB012079.]
Progress in inferring desmoplastic stromal tissue microstructure noninvasively with ultrasound nonlinear elasticity imaging
Authors: Ferreira Elizabete R. , Oberai Assad A. , Barbone Paul E. , Hall Timothy J.
Published: November 2013

Desmoplasia is the abnormal growth of fibrous tissue that is often associated with malignancy in breast and other solid tumors. The collagen comprising the extracellular tissue matrix tends to be more dense than in normal breast tissue, and to exhibit altered microstructure. The distinctive mechanical properties of solid tumors are often attributed to the abnormal density and microstructure of their collagen extracellular matrices. For example, a higher concentration of collagen implies a larger linear elastic modulus, while a decrease in fiber tortuosity would mean a smaller “toe” region in the stress-strain curve. This talk describes progress of inferring local tissue microstructural properties from noninvasive, in vivo measurement of nonlinear elastic properties of breast tissue. An ultrasound elasticity-imaging based approach for determining the average local micro-structural properties of tissue was developed and implemented. It utilizes multiscale homogenization methods to determine effective macroscopic properties from assumed microstructural arrangements of collagen fibers. The resulting nonlinear constitutive equation is then used in a model-based elastic inverse problem solver to obtain local microstructural tissue properties from macroscopic observations of tissue deformation. Its potential in diagnosing malignant breast tumors in a small set of patients was also examined. [NSF Grant 50201109; NIH NCI-R01CA140271.]
Analysis and measurement of the modulation transfer function of harmonic shear wave induced phase encoding imaging
Authors: McAleavey Stephen A.
Published: November 2013

B-scan imaging relies on geometric focusing of ultrasound echoes. In contrast, the method of Shear Wave Induced Phase Encoding imaging achieves lateral resolution of an elastic target by using traveling shear waves to encode the position of scatters in the phase of the received echo. A Fourier series description of the phase modulated echo signal is developed, demonstrating that echo harmonics at multiples of the shear wave frequency reveal target k-space data at identical multiples of the shear wavenumber. Modulation transfer functions (MTFs) are calculated for maximum shear wave acceleration and maximum shear constraints, and compared with a conventionally focused aperture. The relative SNR of this method versus a conventionally focused aperture is determined from these MTFs. Reconstructions of wire targets in a gelatin phantom using a cylindrical shear wave source are presented, including Images generated from the fundamental and second harmonic of the shear wave modulation frequency. Comparison of images generated at 1 and 3.5 MHz demonstrate the weak dependence of lateral resolution on ultrasound frequency with this method.
A quantitative assay of neovascularization using high-frequency ultrasonic spectroscopy
Authors: Cadet Michaelle A. , Quiroz Andrea N. , Stiles Janeese E. , Thompson Laurel A. , Doyle Timothy E.
Published: November 2013

The stimulation and inhibition of tissue vascularization has important applications to tissue engineering and oncology. Approaches to quantitatively evaluate neovascularization in vivo in adult animals with differentiated tissue include both invasive methods that use an implanted or injury-induced matrix in the study organism, or noninvasive small animal imaging methods such as MRI, CT, and PET. The objective of this study was to determine if ultrasonic spectra in the 10–100 MHz range could be used as an in vivo neovascularization assay. Numerical simulations and phantoms were used as model systems to test the feasibility of the approach. The simulations modeled ultrasonic scattering from microscopic vascular networks using clusters of walled, randomly oriented cylinders to represent blood vessels and cylindrical wave functions to represent ultrasonic waves. Phantoms with microscopic channels were fabricated from gelatin, soluble fiber, and thin polymer strands embedded into the gel. The strands were removed after the gel solidified and filled with ultrasonic blood simulant. Initial numerical results indicated that increasing the number of blood vessels in tissue significantly altered the spectra. Methods for analyzing the data, including the use of spectral parameters and pattern recognition programs such as principal component analysis, will be discussed.
Determining affects of temperature change on tissue using high-frequency ultrasound: Porcine heart (aorta)
Authors: Stroud David S. , Haskel Chad , Doyle Timothy E.
Published: November 2013

The purpose of this study was to determine if high-frequency (HF) ultrasound (20–80 MHz) is sensitive to the change of average human body in temperature (approximately 37 °C) to average room temperatures of approximately 20 °C to 25 °C. When temperatures decrease, water molecules within organic tissue expand, decreasing their density. Changes in temperatures can alter the number of molecules found within a given area, altering tissue density. Two parameters in high-frequency ultrasound (20–80 MHz) have been found to be sensitive to a range of pathologies in resected margins from breast conservation surgery: The number of peaks (the peak density) in the waveform spectrum and the slope of the Fourier transform of the waveform spectrum. Changes in temperatures may affect the accuracy of these two parameters. To test this hypothesis, through-transmission and pulse-echo measurements were acquired fresh (within one hour of slaughter from local butchers) aorta samples from porcine hearts. Results will be presented and discussed. [This work was supported by a Utah Valley University Presidential Fellowship Award.]
High-frequency ultrasound study of excised tissue cryopreserved via simple sugars
Authors: Sutherland Christopher D. , Warner Logan L. , Doyle Timothy E.
Published: November 2013

High-frequency ultrasound (20–80 MHz) has been found to be sensitive to a range of pathologies in excised breast tissue before fixation in formalin or other formaldehyde analogues. Formalin fixation, however, may alter the structure and rigidity of a sample so that data gathered using high-frequency ultrasound after fixation may no longer be viable for research purposes. This limits the amount of time researchers may conduct tests, so preservation via simple sugars is being considered. Numerous studies have been conducted using sucrose, trehalose, or glucose as cryoprotectants for cells and simple tissues. The objective of this study was to test the sensitivity of high-frequency ultrasound to changes in the microstructure, stiffness, and cellular integrity of tissue samples due to cryopreservation with these sugars. Domestic pig heart tissue was placed in aqueous solutions of sucrose, trehalose, and D-(+)-glucose. The specimens were refrigerated and observed over time using high-frequency ultrasound to detect tissue damage. The results of this study suggest that cryopreservation with sugars will not only allow more time for researchers to conduct ultrasonic tests on surgical specimens, but also that high-frequency ultrasound could potentially be used as an assay to measure tissue degradation in preserved living tissues such as transplant organs.
Correlation between nano- and macro-properties of cell walls
Authors: Tittmann Bernhard R. , Xi Xiaoning
Published: November 2013

This report is on the imaging and characterization of the nano-composite structure of native primary cell walls. In particular, the structure of primary celery epidermis cell walls was imaged with sub-nanometer resolution using the atomic force microscope (AFM). The high-frequency acoustic microscope was used to image onion cell (Allium cepa) wall epidermis at the micro-scale at 600 MHz at 1 micron resolution. V(z) signatures were obtained and used to estimate the bulk modulus of 3.30 GPa in good agreement with destructive measurements. The combined results reveal a surprisingly fine but strong nano-composite for the lignocellulosic biomass.
Mutual validation of muffler performance evaluation methods using field measurements and finite element analysis
Authors: Mang Scott , Vipperman Jeffrey S.
Published: November 2013

The design of large industrial mufflers poses a problem to many companies involved in their fabrication. Most of the design and evaluation theory has been developed using one dimensional acoustics. However, it is well known that in large ducts, the one dimensional propagation assumption breaks down at much lower frequencies. The three dimensional propagation of acoustic waves in complex geometries is a very difficult problem to solve analytically. For this reason, numerical methods are employed. In this study, a finite element analysis (FEA) program is validated using field measurements. Three well known muffler performance criteria and three different large sized mufflers are considered. The three performance metrics are noise reduction (NR), insertion loss (IL), and transmission loss (TL). During the study, sufficient agreement for validation of the performance evaluation methods was found. A method for reconciling idealistic FEA simulations and in situ measurements by accounting for significantly high ambient noise is developed.
Study of micro-perforated tube mufflers with adjustable transmission loss
Authors: Xiang Longyang , Zuo Shuguang , Zhang Menghao , Hu Jiajie , Long Guo
Published: November 2013

Micro-perforated tube muffler has the advantages of both the reactive and dissipative mufflers. The paper proposed that the change of micro-perforated tube length could change the transmission loss behaviors of the micro-perforated tube mufflers. The acoustic impedance of micro-perforated plate was derived in this paper, which was used in the finite element method to calculate the transmission loss of mufflers with various micro-perforated tube lengths. Then, a relation formula of the maximum muffling frequency and the micro-perforated tube length was fitted. This kind of adjustable mufflers could be used efficiently to control the noise of the rotating machines, whose main noises are always proportional to the rotating speed.
Evaluation of a collocation method for the analysis of multi-segmented waveguides at high-frequencies
Authors: Ginsberg Jerry H.
Published: November 2013

A method for analyzing high-frequency signal propagation in rectilinear waveguides consisting of interconnected segments has been proposed [Ginsberg, POMA 19, 030104 (2013)]. The signal within each segment is represented as a series of modes that either propagate or evanesce in the forward and backward directions. The state variables are the modal amplitudes. Equations for these parameters are obtained by satisfying continuity and boundary conditions on pressure and axial particle velocity at preselected points on transitional cross-sections. This leads to a sequential evaluation of transfer functions for the modal amplitudes. The present work will examine the convergence and accuracy properties of the formulation by comparing its results to those obtained from a classical orthogonality analysis. The system consists of a pair of coaxial circular hard-walled cylinders axisymmetrically excited by a piston covering half the radius at one end, and the other end is rigidly closed. The frequency for the evaluation is slightly greater than the cutoff value for the sixth mode in the narrower segment. Aspects that are examined are computer code verification, metrics for comparing analyses, the influence of the number and placement of the collocation points, and the influence of evanescent modes.
Validation of two-port temperature models for heat dissipation in exhaust systems
Authors: Elsahar Weam S. , Elnady Tamer M. , Åbom Mats
Published: November 2013

The acoustic performance of exhaust systems is affected by the flow speed and temperature of the exhaust gases. The flow speed affects the convective wave speed and changes the acoustic properties of some acoustic elements such as perforates. The temperature of the exhaust gas affects its density and the speed of sound. It is important to model the flow and temperature distribution within the exhaust system in order to perform an accurate acoustic simulation. The acoustic propagation along an exhaust system can be modeled by dividing the exhaust system into a number of two-port elements. It has been previously shown that flow distribution and pressure drop calculation can be done using the same two-port elements but using a different set of transfer matrices. A similar approach was previously proposed to calculate the temperature drop using the same two-port elements but using a new set of transfer matrices. This technique has the advantage to solve all physics by defining only one network. An improved version of this formulation is presented in this paper. Several cases were tested and the thermal and acoustic results were compared to finite element simulations and measurements. The two port results matched well with the other techniques.
A wearable real-time vocal biofeedback device
Authors: VanDam Mark , Clemetson Bradley C. , Hurson Marshall , Pacheco Tyler , Jakubowski Shirley , Jakubowski Walter , Nicholas Doreen
Published: November 2013

A body-worn, real-time speech and voice biofeedback device is described. Data from an acoustic microphone and piezoelectric sensor worn comfortably in a neckband are streamed to a digital signal processor and a small, mobile computer, altogether able to fit into a pocket for extended use. User laryngeal and spectral characteristics are determined from the combination of sensor inputs. Selected vocal characteristics (e.g., vocal intensity, shimmer, jitter, spectral output, and fundamental frequency) are analyzed in real-time to provide immediate user feedback via tactile or visual response to indicate speech production pathologies including reduced loudness, pitch instability, or other features. With minimal training, this feedback can be immediately acted upon by the wearer to adjust speech and voice production characteristics accordingly. In addition, all data from input sensors are collected and stored in the computer's memory for offline analyses of speech and voice production characteristics. Extended-use, large-sample data collection addresses issues in the extant literature including ecological validity, reactivity (e.g., the Hawthorne effect), small sample sizes, and unaccounted for individual differences. This work offers a realistic description of voice use and assesses a wide range of functional and organic clinical conditions that are known to affect speech production (e.g., Parkinson's disease).
Computational simulation of clarinet-like models
Authors: Strong William J.
Published: November 2013

The presentation will review the computational simulation of two clarinet-like models. The Stewart and Strong model (J. Acoust. Soc. Am. 68, July 1980) consisted of a uniform cylindrical tube with an attached clarinet mouthpiece and reed. The tube was represented by 0.25-cm sections of lumped element transmission line. The tapered mouthpiece was similarly represented with 0.1-cm sections. The reed was represented as a non-uniform bar clamped at one end. The simulation was carried out on a DEC PDP-15 computer and had a running time of roughly 250,000 times real time. The Sommerfeldt and Strong model (J. Acoust. Soc. Am. 83, May 1988) was similar to the Stewart model, but included seven toneholes. The impedance of the tube with mouthpiece was calculated and used to calculate the impulse response. This was used to determine the interaction between pressure and flow at the reed opening. A player's airway was also included in the model because, at the time, there was some interest in its effect on tone production. Computational and experimental results will be presented. The two examples will illustrate some limits to simulation of models when computational power is inadequate as was true at the time.
Laboratory study of outdoor and indoor annoyance caused by sonic booms from sub-scale aircraft
Authors: Loubeau Alexandra , Rathsam Jonathan , Klos Jacob
Published: November 2013

Advances in integrated system design tools and technologies have enabled the development of supersonic aircraft concepts that are predicted to produce sonic booms with lower loudness levels while maintaining aerodynamic performance. Interest in the development of a low-boom flight demonstration vehicle for validating design and prediction tools and for conducting community response studies has led to the concept of a sub-scale test aircraft. Due to the smaller size and weight of the sub-scale vehicle, the resulting sonic boom is expected to contain spectral characteristics that differ from that of a full-scale vehicle. In order to justify the use of sub-scale aircraft for community annoyance studies, it is necessary to verify that these spectral differences do not significantly affect human response. The goal of the current study is to evaluate both outdoor and indoor annoyance caused by sonic booms predicted for these two classes of vehicles. The laboratory study is conducted in two sonic boom simulators that provide a realistic reproduction of the outdoor and indoor sonic booms. The indoor facility also provides a realistic listening environment to address the effect on human annoyance of interior rattle noises predicted to be induced by the structural excitation from the sonic boom.
Limitations of predictions of noise-induced awakenings
Authors: Fidell Sanford , Mestre Vincent , Tabachnick Barbara , Fidell Linda
Published: November 2013

Awakenings attributable to transportation noise intrusions into residential sleeping quarters are surprisingly rare events. Current methods for estimating such awakenings from indoor sound exposure levels are problematic for several reasons. They are based on sparse evidence and limited understandings; they fail to account for appreciable amounts of variance in dosage-response relationships; they are not freely generalizable from airport to airport; and predicted awakening rates do not differ significantly from zero over a wide range of sound exposure levels. Even in conjunction with additional predictors, such as time of night and assumed individual differences in “sensitivity to awakening,” nominally SEL-based predictions of awakening rates remain of limited utility, and are easily mis-applied and mis-interpreted. Probabilities of awakening are more closely related to SELs scaled in units of standard deviates of local distributions of aircraft SELs, than to absolute sound levels. Self-selection of residential populations for tolerance of nighttime noise and habituation to airport noise environments offer more parsimonious and useful explanations for differences in awakening rates at disparate airports than assumed individual differences in sensitivity to awakening.
Application of assorted tonality metrics to human annoyance thresholds of tones in noise
Authors: Lee Joonhee , Francis Jennifer M. , Steinbach Adam , Wang Lily M.
Published: November 2013

Audible tones in background noise as produced by mechanical equipment in buildings can lead to complaints from occupants. A number of metrics including prominence ratio, tone to noise ratio, tonal audibility, and Aures’ tonality have been developed to quantify the perception of tonalness, but it is not clear how these measures correlate with subjective annoyance response from listeners. This research investigates the relationship between tonality metrics and subjects’ annoyance. As reported in another paper, two tests were conducted to determine annoyance thresholds for tones in noise. One involved having subjects rate their annoyance after being exposed to background noises with differing levels of tones while working on a given task. In the second test, subjects were asked to select the minimum tone level above a set background noise condition at which they began to feel annoyed. The thresholds according to assorted tonality metrics are calculated based on the subjective results and compared to previous research.
Listening as your neighbors: Simulation and evaluation of building structural transmission
Authors: Ke Fangyu , Shu Cheng , Zhou Xiang , Yang Xuchen , Ren Gang , Bocko Mark
Published: November 2013

The enjoyment of music can be jeopardized by the knockings on the door and your furious neighbor shows up. Building structural transmission passes annoying sound to neighbors even when the audio is at low volume. In this paper, we implement a computational model for the simulation and evaluation of building structural transmission based on field measurements of structural transmission profiles and subjective listening tests. This model is intended to serve as a signal analysis tool that allows the audio engineers to evaluate the interference level using computer software and monitor system, so they can assess and mitigate these interferences without the need of conducting tedious subjective evaluation experiments in real acoustical environments. Our proposed transmission models are summarized from multiple acoustical measurements conducted in real room pairs to ensure its authenticity. Essentially we build “virtual” room pairs so we can simulate the interferences reaching the neighbors. We also implement a computational auditory model based on audio content analysis and subjective evaluation experiments to automatically evaluate the interference level caused by the transmitted sound. The proposed simulation and evaluation tool finds extensive applications in various areas of audio engineering such as audio content production, noise control, and audio system design.
Background noise levels on the fireground
Authors: Suits Joelle I. , Wilson Preston S. , Ezekoye Ofodike A.
Published: November 2013

An important part of signal detection and distinction is the strength of the signal compared to the levels of the background noise. On a fire scene, firefighters use a Personal Alert Safety System (PASS) device to locate trapped or injured personnel. When a firefighter becomes incapacitated, the device emits an audible alarm to help rescue teams locate the downed firefighter. This device has proven to be an invaluable part of a firefighter’s equipment. However, there are cases in which the signal was not heard or localizable. It has become apparent that scientific research is necessary to improve this signal. The approach taken to investigating this environment is to use the passive sonar equation as a template. An important piece of this research is the background noise levels that are routinely found on an active fire scene. Much of the equipment used by firefighters acts as high intensity broadband noise sources. Measurements were taken to investigate the frequency, level content, and directionality of the equipment used on the fireground. The A-weighted spectrum of the equipment has then been compared to the signal emitted by a PASS device. [Work supported by U.S. Department of Homeland Security Assistance to Firefighters Grants Program.]
Prediction of wind induced noise over bodies and small cavity
Authors: Yow Huoy Thyng , Hii Dominic , Saw Anderson , Tan Cheah Heng , Fisol Ummi Masyitah Mohd , Ripin Zaidi Mohd , Ismail Norilmi Amilia , Saad Abdullah Aziz , Hashim Mohd Khairul Rabani , Yi Chan Ping
Published: November 2013

The problem with wind induced noise exists in any electronic device used in the outdoor that incorporates microphone components mounted underneath small opened cavities within its body. Due to the complexity nature of the problem, efforts in trying to experimentally understand the flow induced noise problem has lengthened product development cycle time. In this paper, a CFD approach using the SST k-omega turbulence model were utilized as an initial model to assist in understanding the phenomenon. Several instances of experimentation using actual prototype models were conducted for the correlation study. The experimentally perceived noise from the output of the microphone was found to be fundamentally correlated to the numerical analysis as evidenced from the flow velocity vectors, profiles, and vortex core inside the cavity region. It is also shown that by following the principle of nonlinear theory of cavity resonances and Rossiter’s Theory, the understanding of the phenomenon can be further strengthened. Some inaccuracies in the numerical results stems largely from the choice of turbulence model and meshing configurations. Future work and activities required to extend and improve the current work were suggested at the end of this document.
Impedance assessment of an acoustic metamaterial-inspired acoustic liner
Authors: Beck Benjamin , Schiller Noah , Jones Michael
Published: November 2013

Acoustic liners are commonly used to reduce noise from commercial aircraft engines. Engine liners are placed in the nacelle inlet and aft bypass duct to attenuate the radiated noise from the fan, turbine, combustor, and other sources within the engine. Current engine liners are constructed of a metal perforate facesheet over a honeycomb structure. With this design, the low frequency performance of the liner is limited by the depth of the honeycomb. However, with advances in engine design, lower frequency performance is becoming more critical. Acoustic metamaterials can exhibit unique acoustic behavior using periodically arranged sub-wavelength resonators. Researchers have shown that metamaterials can effectively block the propagation of low-frequency acoustic waves. Therefore, acoustic metamaterial-inspired concepts are being investigated to improve the low frequency performance of engine liners. By combining the idea of a split-ring resonator metamaterial with a traditional quarter-wave acoustic liner, the low frequency acoustic absorption of the device can be significantly increased. The normal incident absorption coefficient of a metamaterial-inspired liner shows an increase from 0.05 to 0.8 at 600 Hz relative to a conventional honeycomb liner with the same depth while retaining the same 0.5 absorption coefficient at 1550 Hz.
Application of generalized autoregressive conditionally heteroskedastic modeling to wind noise for enhancing detection of transient infrasound
Authors: Frazier William G. , Lyons Greg
Published: November 2013

Autoregressive moving average (ARMA) process models are often used to represent stationary random processes. In applications where the process of interest is not stationary or has samples from a heavy-tailed distribution, extension to a generalized autoregressive conditionally heteroskedastic (GARCH) model can be used to improve the process representation. This modeling approach was developed by the financial industry and is frequently used in econometrics to represent financial time series possessing volatility clustering and to improve return forecasts. Recently, ARMA/GARCH models have been used to improve surface-to-surface radar detector performance where the clutter due to sea state possesses a heavy-tailed distribution. In this presentation, we will demonstrate the application of vector ARMA/GARCH models to the modeling of wind noise measured on infrasound arrays and to detection of transient infrasound in the presence of this noise.
Beamforming methods in infrasonic array processing—Continuous signals
Authors: Blom Philp , Waxler Roger , Frazier William Garth
Published: November 2013

It is often the case in analyzing infrasonic data that coherent “noise” due to natural and anthropomorphic sources obscures the phenomena of interest. Beamforming methods have been studied as a means of identifying continuous infrasonic signals and spatially removing them from a data record. An historical overview of frequency based array processing methods with be presented along with discussion of eigen-decomposition representations of various spatial spectral formulae. An application using spatial filtering to identify and extract microbaroms from an infrasonic data record will be demonstrated and discussed. Additionally, the framework for a robust, data-adaptive array processing method and the challenges associated with its implementation will be presented.
Processing international monitoring system infrasound data to detect and locate global events using probabilistic algorithms
Authors: Arrowsmith Stephen , Marcillo Omar , Randall George
Published: November 2013

Automating the detection and location of events using the International Monitoring (IMS) System infrasound network is a significant challenge. Any algorithm must reliably detect nuclear tests in the atmosphere with a minimum number of false alarms. Here, we report on the application of probabilistic techniques for detection, association, and location of infrasound events to data from the IMS network. We compare our results with the SEL3 automatic event detections obtained by the CTBTO.