bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulations of multibeam sonar echos from schooling individual fish.
Authors: Holmin Arne Johannes , Handegard Nils Olav , Korneliussen Rolf , Tjo/stheim Dag
Published: July 2011

Echo sounders and sonars are important tools in fisheries research, and interpretation of fish school data can be used to extract information about fish behavior. For such interpretations to be reliable, accurate acoustic modeling of the targets and the acoustical instrument is needed. A simulation model for multibeam and multifrequency echo sounders and sonars is presented, in which synthetic echograms of fish schools are generated based on known individual dynamic and acoustical variables and beam configuration of the specific acoustical instrument. Using the simulation model, acoustic observations of fish school behavior patterns can be generated and analyzed along with observations of real fish schools. This provides a tool for validating both the interpretation of real data and the interpretation of behavior models based on individual interactions. Examples of the effect of local and global orientation fluctuations are presented and compared to data of real fish schools, specifically for the SIMRAD MS70 multibeam sonar.
Case study: Innovative acoustical design of central plant.
Authors: Holst Peter K. , Alvarado Robert P.
Published: July 2011

This presentation will provide insights from a successful project that included a central plant located at the ground floor of a new hospital tower in a residential neighborhood in Burlingame, California. Design considerations at the onset of the project included establishing acceptable noise criteria for nearby residences. Ambient noise surveys were conducted and appearances at public hearings ensured the noise levels of the equipment would not exceed the existing noise environment. Solutions for reducing equipment noise include the use of ultraquiet cooling towers, sound-absorbing concrete block, and an inventive acoustical silencer design at the intake and discharge of a generator room. Within the hospital, space planning would not afford a buffer floor separating the generator room from vibration-sensitive eye-surgery operating rooms directly above. A heavy-duty spring-isolated ceiling, built in sequence with an independent spring-isolated equipment-support grid, required significant levels of coordination between the acoustical consultant and construction team. This presentation will include a summary of project concerns, innovative design solutions to meet the applicable noise criteria, and postconstruction measurement results. This valuable information could be used in the design of future medical facilities in residential neighborhoods, and in the design of unavoidable juxtapositions at sensitive uses.
Effects of noise on emergency department staff.
Authors: Mahapatra Arun , Okcu Selen , Ryherd Erica , Ackerman Jeremy , Zimring Craig
Published: July 2011

The hospital sound environment is complex. The impact of a poor soundscape is becoming an increasing concern for both staff and patients, particularly in emergency departments (EDs). While there is growing evidence of the negative impacts of a poor soundscape, there is surprisingly little rigorous evidence about exactly what acoustic characteristics impact hospital staff. This paper presents a detailed acoustic study of two EDs in Atlanta, GA. Equivalent sound pressure levels (Leq), speech intelligibility index (SII), spectral distribution, and other acoustic metrics were calculated for four locations in each emergency department over 24 h. Results show Leq’s between 50–63 dBA, which severely exceeds the 30 dBA guideline level set by the World Health Organization. Additionally, no area observed held a “good” SII rating. These acoustic measurements will be compared to results of staff questionnaires focusing on staff stress and job satisfaction. Findings from this work will advance the understanding of how various characteristics of the ED soundscape impact occupants, how to best measure and quantify these characteristics, and how to improve the ED soundscape. [Work supported by Health Systems Institute (HSI).]
Measuring the effects of acoustical environments on nurses in health-care facilities: A pilot study.
Authors: Sbihi Hind , Hodgson Murray , Astrakianakis George , Ratner Pamela
Published: July 2011

This paper summarizes the methods and results of a pilot ecological study conducted in four health-care facilities (acute-care, community-care, and long-term-care). The objective was to consolidate and test tools for exposure assessment and the investigation of study outcomes, in particular, stress. Area and personal monitoring was performed. Nurse noise exposures were monitored. Full-shift monitoring of sound levels was performed, and conventional acoustical parameters derived; new acoustical descriptors including occurrence rate and peakiness were also determined. Two questionnaire scales were developed: a study questionnaire to assess perception of the acoustical environment and of work- and noise-related stresses, and a daily diary to capture variations in the perceived stress and document aggressive events. The study questionnaire was found to measure disturbance, impaired communication, and mental fatigue. Biological markers of noise-related stress (salivary cortisol and heart-rate variability) were collected. Exposure measures were correlated with outcomes; while the results were often not statistically significant due to small sample sizes, they identified interesting relationships and validated the measurement tools for future use. Long-term-care was identified as the most acoustically-critical environment both from a physical-acoustical perspective and from the perspective of workers.
In defense of sleep.
Authors: Solet Jo M.
Published: July 2011

In defense of sleep environments of care that deliver 24-h service to patients and residents ideally provide a level of quiet compatible with sleep. Yet, historically the noise levels in hospitals have been rising, leading the Facilities Guidelines Institute, for the first time, to include minimum acoustic standards in the 2010 cycle of the Guidelines for the Construction of Health Care Facilities. This presentation will provide the most recent information about the nature of sleep, the health risks associated with limited sleep, and the U.S. epidemiological evidence supporting the conclusion that sleep is a critical pillar of health, in parallel with nutrition and exercise. Listeners will be equipped with scientific evidence in defense of sleep, which will enable them to advocate for the critical role of acoustics expertise as part of the design process. In addition, practitioners will discover new incentives to better protect their own sleep, as part of effective self-care and to enhance performance.
Relationships between gray whale (Eschrichtius robustus) calling rates, group size, and ambient noise levels in Laguna San Ignacio, Mexico.
Authors: Ponce-Morado Diana , Thode Aaron M. , Guerra Melania , Urban Jorge , Swartz Steven
Published: July 2011

Determining relationships between calling activity and group size for marine mammal species is challenging, in part due to difficulties in obtaining reliable independent visual censuses of animals in open waters. In this study, acoustic calling rates of eastern Pacific gray whales were measured over a 4-week period during their 2008 breeding season in the sheltered lagoon of Laguna San Ignacio of Baja Mexico. Visual counts were conducted for 6 days during the deployment. It was found that the lagoon population more than doubled over the observational period, with much of the increase occurring over a 7-day period. Acoustic data collected during those 6 days were manually reviewed to yield counts of various gray whale call types during each day. All call rates showed peaks in early morning and evening, with minimum rates generally detected in the early afternoon, a time of low ambient noise but high tourist panga activity. The number of S1-type calls counted over 24 h increased roughly as the square of the number of the animals in the lagoon, when call counts were adjusted for variations in background ambient noise levels. An exception to this trend occurred during a time of rapid population increase in the lagoon.
Variations in the number of fin whale calls recorded at different locations in the Northeast Pacific Ocean.
Authors: Weirathmueller Michelle J. , Soule Dax C. , Wilcock William S. D.
Published: July 2011

A large number of fin whale calls have been observed in a 3-year ocean bottom seismometer dataset (2003–2006) over the Endeavor Ridge (48°N/129°W), a hydrothermally active area in the Northeast Pacific Ocean. Most of the vocalizations were detected during the winter months. Because zooplankton constitute an important part of fin whales’ diets, and enhanced populations of zooplankton have been observed at all depths above the Endeavor hydrothermal vents, it has been hypothesized that the fin whales could be near the vents specifically for feeding. As part of the analysis of the Endeavor vent field data set, algorithms have been developed, which utilize the absolute and relative spectral energy levels in the frequency band of the whale vocalizations. In order to test whether the concentrations of whale vocalizations are unusually high over the hydrothermally active area, the detection algorithm is being applied to data from individual ocean bottom seismometers at other nearby locations including the center of Explorer Plate (49.5°N, 129°W), and the base of the continental slope off Nootka Sound (49.3°N, 127.6°W).
Analyzing potential acoustic differences between different bowhead demographics in the Beaufort Sea.
Authors: Grebner Dawn M. , Thode Aaron M. , Blackwell Susanna B. , Greene Charles R. , Koski William R. , Funk Dale , Macrander Michael
Published: July 2011

Most bowhead whales from the Bering-Chukchi-Beaufort stock migrate westward from Arctic Canadian waters through the Alaskan Beaufort Sea each year from late August to late October. Since 2007 both aerial sighting and acoustic call data have been collected during these fall migrations, as part of a long-term monitoring effort to assess the potential impacts of North Slope oil industry activities on bowhead whales. The aerial sighting efforts recorded the position of bowhead individuals or groups, designating the animals as subadults or adults, and noted whether a calf was present. A five-site array of seven directional autonomous seafloor acoustic recorders (DASARs) each recorded the acoustic data. An automated detection algorithm was used to isolate individual bowhead whale calls and estimate their locations. Here simultaneous acoustic and visual data from 2007, 2008, and 2010 were merged to determine whether potential variations in calling behavior exist between subadults, adults, and adults with calves. Visual measurements of animal course and direction were used to place bounds on call times and locations that may be associated with that animal versus other animals sighted nearby. Potential differences in call rate and call type were statistically examined. [Work supported by the Shell Exploration and Production Company.]
Multi-year use of unique complex songs by western arctic bowhead whales: Evidence from three years of overwinter recordings in the Chukchi Sea.
Authors: Delarue Julien
Published: July 2011

The current understanding is that singing is part of bowhead whales’ breeding behavior and that songs change every year. The latter is based on the analysis of songs recorded in the springtime off Barrow, AK, but it is also accepted that spring songs may be somewhat degraded in comparison to those produced in winter when bowheads are most sexually active. A year-long passive acoustic monitoring program in place since July 2007 in the Chukchi Sea provided an opportunity to compare songs recorded during three consecutive fall migrations. One unique song was detected in 2007, 2008, and 2009 and another was detected in 2007 and 2008. Minor variations are likely the result of a difference in song maturity caused by bowheads’ different departure times from the instrumented area in all 3 years. This finding strongly suggests that, when starting to sing in the fall, western arctic bowheads display the same songs every year. Variations occurring throughout the winter could explain the previously observed differences in spring songs at Barrow. However, some songs we recorded during the spring migration in all 3 years showed striking similarities. Songs recorded in the Bering Sea in winter should be examined to fully validate this finding.
Seeing the species through the trees: Using Random Forest classification trees to identify species-specific whistle types.
Authors: Oswald Julie N. , Carretta Jim V. , Oswald Michael , Rankin Shannon , Au Whitlow W.L.
Published: July 2011

Acoustic identification of delphinid species is hampered by high variability in whistle characteristics. It is possible that not every whistle contains species-specific information and that there are “species-specific” whistle types. Random forest analysis was used to examine whistles of 8 species recorded in the eastern tropical Pacific Ocean (Delphinus species, Globicephala macrorhynchus, Pseudorca crassidens, Stenella attenuata, S. coeruleoalba, S. longirostris, Steno bredanensis, Tursiops truncatus). Fifty-one variables were measured from 2176 whistles. The number of trees within a random forest that “voted” for the predicted species was used as a measure of the strength of classification. A whistle was considered strongly classified if the predicted species received at least 40% of the votes, even if the prediction was incorrect. The percent of whistles that were strongly classified ranged from 33% (S. longirostris) to 73% (G. macrorhynchus). Overall, 62% of strong whistles were correctly classified, ranging from 22% (S. longirostris) to 87% (P. crassidens). Overall correct classification for weakly classified whistles was 33% and ranged from 17% (Delphinus spp. and G. macrorhynchus) to 55% (S. bredanensis). Results suggest that while there may be “species-specific” whistle types, the distinctiveness of these whistles and the frequency with which they are produced varies among species.
Photoacoustic tomography: Ultrasonically breaking through the optical diffusion limit.
Authors: Wang Lihong V.
Published: July 2011

Photoacoustic tomography (PAT) has been developed for functional and molecular imaging by physically combining optical and ultrasonic waves via energy transduction. Key applications include early-cancer and functional imaging. Light provides rich contrast but does not penetrate biological tissue in straight paths as x-rays do. Consequently, high-resolution pure optical imaging (e.g., confocal microscopy, two-photon microscopy, and optical coherence tomography) is limited to depths within one optical transport mean free path (∼1 mm in the skin). Ultrasonic imaging, on the contrary, provides good image resolution but suffers from poor contrast in early-stage tumors as well as strong speckle artifacts. PAT—embodied in the forms of computed tomography and focused scanning—overcomes the above problems because ultrasonic scattering is ∼1000 times weaker than optical scattering. In PAT, a pulsed laser beam illuminates the tissue and generates a small but rapid temperature rise, which induces emission of ultrasonic waves due to thermoelastic expansion. The short-wavelength ultrasonic waves are then detected to form high-resolution tomographic images. PAT broke through the diffusion limit for penetration and achieved high-resolution images at depths up to 7 cm in tissue. Further depths can be reached by thermoacoustic tomography using microwaves or rf waves instead of light for excitation.
Noninvasive optoacoustic platform for multiparameter patient monitoring.
Authors: Esenaliev Rinat O. , Petrov Yuriy , Petrov Irene Y. , Prough Donald S.
Published: July 2011

Our objective is to improve patient care by developing a noninvasive, optoacoustic diagnostic platform for accurate and continuous monitoring of important physiological parameters including total hemoglobin concentration, venous oxyhemoglobin saturation (both cerebral and mixed), cardiac output, circulating blood volume, cardiac index, systemic oxygen delivery, and hepatic function. Currently, invasive measurements of these parameters are routinely used in the care of large populations of patients. We built optoacoustic systems for monitoring of these parameters and tested them in animal and clinical studies. The systems include portable, light-weight, inexpensive, pulsed laser diodes, or tunable OPOs operating in the near infrared spectral range. We developed patient interfaces with highly sensitive, wide-band optoacoustic probes designed and built in our laboratory for these diagnostic applications. In some studies, ultrasound imaging systems were used for accurate optoacoustic probing of specific blood vessels. A software package was developed for automatic, real-time, continuous monitoring using measurements at different wavelengths. We will report results of the animal and clinical tests performed by our group to study the capabilities of the optoacoustic platform for noninvasive monitoring of these physiological parameters. [Dr. Esenaliev and Dr. Prough are co-owners of Noninvasix, Inc., a UTMB-based startup that has licensed the rights to optoacoustic monitoring technology.]
Combined application of photoacoustic and acousto-optic imaging for model-free quantitative optical absorption mapping.
Authors: Steenbergen Wiendelt , Molenaar Robert , Daoudi Khalid
Published: July 2011

Quantitative absorption mapping is a major challenge in photoacoustic tissue imaging due to the unknown local fluence inside the tissue. We present a photoacoustic method that is inherently quantitative and does not rely on a model for light transport. It is a well-designed combination of photoacoustic imaging and acousto-optic modulation, where the latter provides information regarding the fluence if certain rules are followed. In our method, photoacoustic (PA) imaging is performed with successive light injection in the tissue at two different positions on the tissue surface. Next an acousto-optic (AO) scan is performed with light injection in the first position, and detection of modulated light at the second position. We will show how the resulting two PA scans and the AO scan can be combined to yield the local absorption coefficient. Here we invoke the principle that in turbid media, light trajectories can be traveled in both directions with equal probability. We will give a brief outline of the theory, leading to an expression for the local absorption coefficient in terms of PA and AO measurements and geometrical parameters of the instrument. We will show results of a validation with the Monte Carlo simulation model and of experiments on phantoms.
Coupled contrast for photoacoustic imaging and detection.
Authors: O'Donnell Matthew
Published: July 2011

Nanoparticle agents with high optical absorption in the near infrared have been used to target diseased cells and increase specific contrast in photoacoustic (PA) imaging. However, background signals from tissue can severely limit the specificity of these agents. This is especially problematic for detecting targeted cells circulating in the vasculature where the large PA signal from blood can completely mask the contrast agent signal. For sensitive detection of targeted cells in the vasculature, their PA signal must be greatly enhanced compared to the blood background. Using a new class of contrast agents called coupled particles, we have developed technologies that can potentially accumulate and concentrate targeted cells while simultaneously enhancing their specific contrast compared to background signals. This approach leverages the high optical absorption and magnetic properties of Au-shell-encapsulated magnetic nanoparticles. By manipulating these coupled particles with an applied magnetic field, targets can be accumulated within the flow field and differentiated photoacoustically through motion processing algorithms providing high contrast specificity. In this talk we will discuss the basic coupled agent technology, procedures for manipulating these agents for cellular accumulation and differentiation, and challenges remaining to translate this technology into clinical use.
Acoustical method of cleaning lungs.
Authors: Hawkins Sanford , Morrison Andrew
Published: July 2011

The muco-ciliary system in the lungs uses cilia asymmetrically beating at 16 Hz to remove lung secretions. As lung secretions are non-Newtonian fluids with a critical frequency between 16Hz and 20HZ, vibrating the lung at 16 thins the secretions. A unique 16 Hz user-powered sound generator, which recently received FDA approval for diagnosis and treatment of respiratory diseases, will be described. The device provides a simple and effective means of acoustically driving the muco-ciliary system in the appropriate frequency range and may possibly synchronize the cilia for improved efficiency. The device may be the first effective way to treat the third leading cause of death. Additionally, a new and more efficient way to cough will be demonstrated.
Optical multiplexed operation of nanomechanical systems.
Authors: Sampathkumar A. , Ekinci K. L. , Murray T. W.
Published: July 2011

An emerging application area for nanoelectromechanical systems (NEMS) is in the next generation of biological and chemical sensors. One of the key technological challenges in the development of sensors using large-scale arrays of NEMS beams lies in designing a measurement system with multiplexing capability to detect simultaneously the flexural motion of a large number of nanomechanical beams. In the latest work, a full-field optical interferometry system making use of a photorefractive crystal is developed to obtain the displacements of the NEMS array. In this system, a coherent imaging approach using an adaptive photorefractive holography technique and a parallel detection scheme employing a charge-coupled device is used to obtain full-field displacement images of the entire NEMS array. Full-field out-of-plane displacement images of an array of 60 nanomechanical beams excited using an optical transduction scheme are presented. The full-field system is characterized in terms of both efficiency of excitation of nanomechanical vibration and sensitivity of the interferometric displacement detection and is found to be well suited for the measurement of vibrations in large-scale NEMS array.
Investigating new photoacoustic contrast agents.
Authors: Firouzi Kamyar , Stride Eleanor , Saffari Nader
Published: July 2011

Numerical studies on the detection of tumors using photoacoustic imaging have shown that relying on optical energy absorption by blood hemoglobin as the contrast mechanism leads to poor image quality. This provides a strong incentive for seeking suitable manufactured photoacoustic contrast agents (PACAs). We present a theoretical comparison of three different photoacoustic contrast agents, all incorporating dye particles with suitable optical absorption characteristics. The three different designs are as follows: (1) stabilized droplet: a droplet of dye; (2) stabilized bubble: a bubble filled with gas and coated by dye as the shell; and (3) phase shift droplet: a droplet of volatile dye, all pulsating in a homogenous incompressible fluid. For each case, the governing equations describing the dynamics of a single PACA and the radiated pressure are derived. Each case is expressed in terms of four coupled sets of equations as the pressure radiated from the bubble, equation of motion, photoacoustic energy equation and equation of state, by virtue of simplifying assumptions. The derived equations are numerically solved by the Runge–Kutta method, using appropriate photoacoustic properties. The numerical results predict a much stronger radiated acoustic signal for the same optical source energy in the case of the stabilized bubble (case 2).
Design and applications of photoacoustic nanodroplets in imaging and therapy.
Authors: Wilson Katheryne , Hannah Alexander , Homan Kimberly , Emelianov Stanislav
Published: July 2011

A unique contrast agent, termed photoacoustic nanodroplet (PAnD), has been developed for several biomedical and clinical applications. A PAnD consists of several plasmonic nanoparticles encapsulated within a nano-sized perfluorocarbon droplet. PAnDs act as contrast agents for ultrasound and photoacoustic imaging through different mechanisms. Optical absorption by plasmonic nanoparticles triggers vaporization of the perfluorocarbon droplet, yielding two effects: first, strong photoacoustic transients are generated, and second, a gas microbubble is formed. Furthermore, subsequent laser pulses interacting with expelled plasmonic nanoparticles result in photoacoustic transients due to thermoelastic expansion of tissue. To demonstrate these contrast enhancement mechanisms, a homogenously laden polyacrylamide phantom (108 PAnD/ml) underwent pulsed laser irradiation (5 mJ/cm2, 10 Hz PRF, 5–7 ns pulse duration), while photoacoustic and ultrasound images were captured with a 40 MHz linear array transducer. Photoacoustic signal from vaporization was one to two orders of magnitude stronger than that from thermoelastic expansion, and ultrasound contrast due to presence of gas microbubbles was significantly increased. In addition to serving as contrast agents, PAnDs with applied ultrasound irradiation cause temporary disruptions of the cell membrane and increase intracellular uptake of nanoparticles, thus improving accumulation and retention of nanoparticles within targeted tissue. A sevenfold increase in cellular uptake of nanoparticles has been demonstrated.
Design of an ideal spherical hydrophone using a plasmonic acoustic cloak.
Authors: Guild Matthew D. , Haberman Michael R. , Alu Andrea
Published: July 2011

An ideal acoustic sensor provides an electrical output that is proportional to and in phase with an incident acoustic pressure field, without significantly altering the impinging field. The common approach to producing such a sensor is simply to minimize the size of the sensing elements relative to the wavelength of the measured field. Unfortunately, this approach has the drawback of reducing sensitivity. Recent work on plasmonic acoustic cloaking [Guild et al., J. Acoust. Soc. Am. 128, 2374 (2010)], however, suggests the possibility of creating an ideal acoustic sensor with dimensions on the same length scale as the incident wavelength, obtained by drastically suppressing its scattering without affecting its ability to measure the impinging signal. Unlike other cloaking methods that reroute the incident field around the cloaked object, plasmonic cloaks allow the cloak interior to interact with the incident field, thereby permitting the realization of highly noninvasive acoustic sensors. This work presents an investigation on the application of a plasmonic acoustic cloak for spherical ceramic hydrophone shells. The resulting scattering reduction and the effects on hydrophone sensitivity and bandwidth due to presence of the cloak are analyzed and discussed.
Experimental analysis of multimicrophone probes for measurement of rocket noise.
Authors: Giraud Jarom H. , Gee Kent L. , Sommerfeldt Scott D. , Blotter Jonathan D.
Published: July 2011

Although the use of multimicrophone acoustic probes can be useful in characterizing rocket noise source regions, one challenge is that both high-bandwidth pressure and intensity data are desirable. The high-frequency bandwidth limitations arise from the microphone size, type, orientation, spacing, and the design of preamplifier holders. To explore their broadband responses, various tetrahedral four-microphone probes were placed in the far field of a loudspeaker and rotated in an anechoic chamber to determine their pressure magnitude and intensity magnitude/angle errors as a function of orientation and frequency. Results are presented comparing the advantages and limitations of each design, particularly as they apply to obtaining rocket noise data. One probe design considered consists of microphones flush-mounted on a hard sphere. Other designs consist of sets of microphones arranged in tetrahedral configurations with their preamplifiers set at different angles.
Broadband versus narrowband experimental methods in acoustics.
Authors: Gladden Joseph
Published: July 2011

Active acoustic measurements (those requiring the input of acoustic energy) can be broadly classified as either broadband or narrowband. In a broadband technique, the acoustic energy introduced into the system is highly localized in time (i.e., a sharp pulse). When transformed into the frequency domain using Fourier analysis, it becomes clear that this energy is spread over a wide frequency range. In a narrowband technique, the acoustic energy is introduced over a longer time period and occupies a much more localized region in the frequency domain. The limit being a single tone excitation signal. Benefits and drawbacks for each of these methods will be discussed as they are applied to several experimental systems including resonance and pulse-echo measurements.
The song of the singing rod.
Authors: Anderson Brian E. , Peterson Wayne D.
Published: July 2011

This paper discusses basic and advanced aspects of the sound radiated by the singing rod demonstration commonly used in physics courses to depict an example of longitudinal waves. Analysis of the sound radiated by various rods with small-signal and large-signal excitations is presented for four different rods. The small-signal sound radiation consists of a fundamental frequency and odd harmonics (each corresponding to a longitudinal mode) when the rod is held at its midpoint. Large-signal sound radiation is highly dependent on the rod’s geometry. The large-signal sound can possess strong even harmonics and/or beating tones resulting from modal coupling of transverse bending modes and either subharmonic longitudinal modes or torsional modes. A detailed analysis of the sound radiation from a singing rod can provide excellent laboratory exercises or classroom demonstrations for advanced undergraduate or graduate level acoustics courses whose scope includes resonances of a bar.
Graduate and undergraduate laboratory courses in acoustics and vibration.
Authors: Glean Aldo A. J. , Judge John A. , Vignola Joseph F. , O’Malley Patrick F. , Woods Teresa J.
Published: July 2011

Two laboratory courses covering acoustics and vibration measurements have recently been developed in the Mechanical Engineering Department at the Catholic University of America. The first course, a junior-level dynamics laboratory, is the first mechanical engineering laboratory course taken by undergraduates. We use acoustics and vibration experiments to illustrate measurement principles broadly applicable to a variety of engineering disciplines. The second course, aimed at first year graduate students, gives a more in-depth coverage of similar topics with an emphasis on automated collection and processing of large data sets. The latter course is intended for students interested in pursuing graduate research in vibration and acoustics, but neither course assumes previous acoustics and vibration background. We describe several of the experiments conducted in these courses and relate them to specific learning objectives.
The Lagrangian method and generalized coordinates used in graduate teaching of electromechanics and electroacoustics.
Authors: Brown David A.
Published: July 2011

While many problems of mechanics may be treated by the Newtonian method involving the analysis of the laws of motion in response to applied forces in inertial reference coordinates, it is helpful to realize that some problems may be treated more directly and with more physical insight using Hamiltonian or Lagrangian (energy based) methods and the application of generalized coordinates. This is particularly useful for electromechanics and electroacoustics where the conversion of electrical, mechanical, and acoustical energy is paramount. The number of coordinates needed is equal to the number of degrees of freedom of the mechanical system (transducer). The Lagrange equations may then be transformed from one system to another (electrical to mechanical to acoustical or vice versa) and each part of the problem may be solved separately and then synthesis in the form a multicontour equivalent electrical network. The Lagrangian based approach [J. Acoust. Soc. Am. 118(2), 2005)] is taught with examples of piezoceramic spheres, cylinders, bars, plates, and disks in a graduate course on Electroacoustics at the University of Massachusetts Dartmouth.
Experiments with heat- and vortex-driven acoustic instabilities in tube resonators.
Authors: Matveev Konstantin , Hernandez Rafael
Published: July 2011

Self-excited tonal sound often appears in engineering systems with mean flow and heat release. To assist students in learning about acoustic instabilities in resonators, a modular low-cost system was constructed and a series of experiments was developed. The experimental setup consists of pipe sections with baffles, damping chamber, air blower, nichrome-wire heater, and piezoelements. The system can operate as a Rijke tube, thermoacoustic engine, vortex-excited resonator, and harvester of acoustic power. Tests carried out with this system include (i) identification of instability domains in the controllable parametric space of the system geometry, mean flow rates, and supplied heat; (ii) investigation of transient phenomena, such as growth and attenuation of sound amplitude; (iii) demonstration of nonlinear effects, such as hysteresis in the system behavior and frequency locking; and (iv) harvesting of energy of self-excited sound using piezoelements. The observed phenomena are interpreted with help of simplified theoretical models. [Work supported by the NSF Grant No. 0853171.]
Selling a quiet workplace through “buy quiet” programs.
Authors: Hayden Charles S. , Hudson Heidi
Published: July 2011

By implementing within the procurement process a program coined as “buy quiet,” an employer can most effectively reduce hazardous levels of noise at their worksites. The process also shifts some of the responsibility for “quiet” onto the groups most capable of reducing noise emission at its source, the manufacturers of the machinery, and equipment being purchased. Controlling noise at its source is best accomplished by those manufacturers, as they are the technical experts on the operating parameters and therefore best suited to make the necessary design changes to reduce noise emissions without adversely affecting the quality or effectiveness of the operation. The process requires a purchaser to compare published noise emission levels of differing models of equipment being purchased and, whenever possible, purchasing the quieter model. Within the process are tradeoff analysis worksheets to weigh the cost of reduced noise emission with other standard purchasing requirements. Buy quiet provides an easy and effective method for an employer to demonstrate a commitment to the use of best available technology to reduce the number of worker’s suffering occupational noise induced hearing loss.
Improving the accuracy of noise exposure estimates for workers with highly variable exposures.
Authors: Neitzel Richard L , Daniell William E , Sheppard Lianne , Davies Hugh W. , Seixas Noah S
Published: July 2011

Noise exposure assessment is difficult, and particularly so for workers with variable noise levels. We evaluated exposure estimates created using three different techniques: trade-mean, task-based, and subjective rating. We created trade-mean, task-based, and subjective rating estimates for a group of 68 construction workers using information collected on three workshifts over 4 months. This information included their trade, the tasks performed on each workshift, their subjective ratings of their noise exposures, as well as a full-shift exposure measurement on each of the three workshifts. We then created hybrid exposure assessment techniques using various combinations of the trade-mean, task-based, and subjective rating estimates, and compared these hybrid estimates to subjects’ measured exposures and to estimates from the single techniques. Hybrid techniques generally resulted in substantial improvements in accuracy compared to the single techniques. A linear regression-based hybrid approach had the best performance, but two much simpler hybrid techniques did nearly as well. Adding trade-mean information did not improve the accuracy of hybrid estimates. These results suggest that a hybrid regression technique combining task-based and subjective rating estimates may produce the most accurate estimates of exposure for workers with highly variable noise exposures.
Acoustic test fixture for insertion loss measurements of hearing protector devices.
Authors: Nilsson Mikkel Bo Bergholt , Sondergaard Jacob
Published: July 2011

According to ANSI standard S12.42 new aspects have to be considered when measuring the Insertion Loss of Hearing Protectors at an Acoustic Test Fixture. First, the ear simulator has to be able to measure up to 170 dB SPL, so a 1/4 in. microphone is needed. The ear canal extension is also longer than the standard extension known from KEMAR and is fitted with flesh simulation. The circumaural pinna has a larger diameter to ensure a perfect seal for all kinds of hearing protection devices (HPD). Furthermore, the total system consisting of ear simulator, ear canal extension, and pinna is heated to body temperature. All the effects of these new aspects have been measured to assess their influence compared to previous ATF types like the ISO 4869-3.
The effects of windscreen flow on noise in motorcycle helmets.
Authors: Kennedy John , Carley Michael , Holt Nigel , Walker Ian
Published: July 2011

Vortex shedding from a motorcycle windscreen results in three flow regions into which the helmet of the rider may be immersed. First, the helmet may be fully in the free stream. Second, the helmet may be directly in the path of vortex shedding from the windscreen. Third, the helmet may be beneath the vortex shedding and shielded from the free stream by the windscreen. On-track tests were conducted and show a difference in sound pressure level of over 10 dB and a change in spectral content for different riding positions and helmet angle. Similar tests were then conducted in a wind tunnel, where simultaneous microphone and flow visualisation measurements allowed the identification and investigation of each flow region under controlled conditions. The contribution of vortex shedding to the noise was assessed using a combination of wavelet analysis and conditional averaging to identify intermittent structures.
Acoustic resonators, quantum mechanics, and gas metrology.
Authors: Moldover Michael R. , Mehl James B.
Published: July 2011

Gas-filled, quasi-spherical cavity resonators were invented to accurately measure the thermodynamic temperature. They have been used with success from 7 to 550 K. Within a few years, the Boltzmann constant kB will become a defined constant. Prior to the definition, groups in several countries plan to re-determine kB using quasi-spherical resonators. In doing so, they expect to measure the speed of sound in argon and helium with sub-part-per-million uncertainties. This work has stimulated several branches of physics and gas metrology. For example, quantum-mechanical calculations of the properties of helium (second and third virial coefficients, viscosity, and thermal conductivity) are more accurate than these properties can be measured. Thus the calculated properties have become standards. Other examples include calculating of microwave resonance frequencies (including coupling effects) of quasi-spherical cavities at the sub-part-per-million level, improved understanding of ducts to conduct gas and sound into and out of cavities, and improved understanding of the interactions of gas modes with the shell surrounding the cavity.
Utility of categorical loudness scaling to estimate the outer- and inner-hair-cell-loss-related components of hearing impairment.
Authors: Tim Jürgens , Stephan Ewert , Thomas Brand , Birger Kollmeier
Published: July 2011

Sensorineural hearing loss is mainly accompanied by a reduction or dysfunction of outer hair cells (OHCs) and inner hair cells (IHCs) in the cochlea. A dysfunction of OHCs is often assumed to correspond to an expansive component and a dysfunction of IHCs to an attenuating component of hearing loss. This study presents a method for assessing OHC and IHC losses from categorical loudness curves using adaptive categorical loudness scaling (ACALOS). A loudness model was used to fit modeled loudness curves to measured loudness curves by adjusting a model parameter HLOHC that quantifies the amount of hearing loss related to the dysfunction of OHCs relative to total hearing loss. This parameter HLOHC was compared to corresponding parameters extracted using temporal masking curves (TMCs) in 16 listeners with different audiometric thresholds. The results showed that both ACALOS and TMCs estimated HLOHC consistently, whereas ACALOS offers much more time-efficiency and about the same accuracy as TMCs. Since ACALOS is an easy and natural task for inexperienced listeners and because of the high time-efficiency, ACALOS appears to be a good candidate for the assessment of this part of the suprathreshold processing of sensorineural hearing-impaired listeners in clinical practice. [Work supported by the DFG (Grant No. SFB TRR31).]
Filter characteristics derived from auditory-nerve fiber responses following noise-induced hearing loss.
Authors: Kale Sushrut S. , Heinz Michael G.
Published: July 2011

Sensorineural hearing loss (SNHL) produces a loss of frequency selectivity and elevated thresholds in the auditory periphery. Broadened cochlear tuning significantly affects magnitude and phase responses of auditory filters and thus can change cochlear-response timing. The present study compared auditory-filter characteristics in normal-hearing and noise-exposed anesthetized chinchillas. Impulse responses of auditory filters were derived from responses of auditory-nerve fibers to broadband noise using spike-triggered averaging techniques. Frequency modulations (or frequency glides) in impulse responses were quantified by computing instantaneous frequencies from impulse-response zero crossings. Group delays for individual auditory filters were computed from phase-frequency responses. Cochlear traveling-wave delays were estimated from shuffled cross-correlograms. Preliminary results suggest that auditory-filter best frequency shifts apically following SNHL. Latencies of impulse responses and traveling-wave delays were much shorter following noise exposure. For normal-hearing fibers, frequency glides in impulse responses increased as a function of time for high characteristic-frequency (CF) fibers and decreased for low-CF fibers, consistent with previous studies. SNHL significantly affected frequency glides of noise-exposed fibers in a manner consistent with the loss of tonotopicity. These characterizations of impaired auditory filters have important implications for SNHL effects on temporal and spatiotemporal coding of complex sounds, such as speech. [Work supported by NIH Grant No. R01DC009838.]
Relationship between amplitude modulation in psychophysical tasks and speech in listeners with normal and impaired hearing.
Authors: Hoover Eric , Souza Pamela , Gallun Frederick
Published: July 2011

Previous work suggests that listeners with hearing loss may be unable to discriminate high-rate amplitude modulations, even when the modulation depth is above the modulation detection threshold [Grant et al., J. Acoust. Soc. Am. (1998)] 104, 1051–60. For listeners with normal hearing, high-rate amplitude modulations contribute to speech understanding when spectral information is degraded [Xu et al., 117, 3255–3267 (2005)]. In listeners with hearing loss, the ability to use amplitude modulation in speech may be limited to frequencies at which modulation frequency discrimination is possible. To test this, amplitude modulation detection and discrimination thresholds were measured in listeners with normal hearing and mild-to-moderate sensorineural loss. The signal was a broadband noise carrier sinusoidally amplitude modulated at rates of 10–640 Hz. Sentence and nonsense syllable recognition was measured for the same listeners. To restrict spectral information, speech was vocoded with a sinusoidal carrier modulated with three or six channels of envelope information. Envelope filter cutoff frequency was varied from 10–640 Hz. Compared to listeners with normal hearing, the listeners with hearing loss had more variable modulation frequency discrimination and that discrimination was related to their ability to use high-rate modulation information in speech recognition. [Work supported by NIH.]
Analysis of hearing aid acoustical feedback by means of fast multipole method-boundary element method and the transfer matrix method.
Authors: Cordioli Julio A. , Araujo Douglas C. , Lenzi Arcanjo , Masson Zargos
Published: July 2011

A numerical procedure is investigated for the analysis of hearing aid feedback. The receiver, connecting tubes, ear channel, and vent are considered by means of the standard transfer matrix method. The receiver transfer matrix is obtained experimentally through the two load method, while the transfer matrices representing the other components are obtained by assuming plane waves and taking in account viscous-thermal effects. The radiation impedance of the vent and the transfer function between the vent outlet and the microphone are calculated using the boundary element method and the fast multipole method (FMM-BEM). The use of FMM-BEM solver allows the solution of considerably larger models than standard BEM solvers, which means that finer details of the pinna, vent outlet, and hearing aid microphone may be included in the analysis. Numerical results are compared with experimental data obtained using a hearing aid mounted on the pinna of a manikin, and good agreement is observed.
Cochlear implant channels with high thresholds degrade medial vowel perception.
Authors: Bierer Julie Arenberg , Bierer Steven M. , Maloff Erin S. , Lin Ann
Published: July 2011

There is considerable evidence that the functional interface between cochlear implant electrodes and the auditory nerve varies from channel to channel within individual patients. Recently a method was proposed to gauge the status of a channel’s interface on the basis of its threshold to focused stimulation using tripolar electrode configuration. This approach showed that channels with high tripolar thresholds have broader psychophysical tuning curves. In this study, the relationship between the number and distribution of high threshold channels with medial vowel identification in a bvt paradigm was examined. Tripolar thresholds were measured for all channels in seven listeners. Vowel identification was tested in the sound field with six repetitions. On the basis of each listener’s electrodogram (the sound processor output of current amplitude as a function of time and channel), the similarity of the vowels using a principle component analysis was examined. We then related the vowel confusions based on the electrodogram of different subsets of channels, based on basal to apical location or tripolar threshold. Preliminary results suggest that the channels with high tripolar thresholds, or in regions of high variability in tripolar threshold, can account for a significant amount of the variance in subject performance. [Work supported by NIH Grant No. DC8883.]