bluuebunny/crossref_metadata_2025 huggingface dataset:
Physclips: Multimedia, multi-level learning, and teaching resources
Authors: Wolfe Joe , Hatsidimitris George
Published: September 2012

Physclips provides multimedia resources to physics students and teachers at the levels of senior high school to introductory university. Completed volumes cover mechanics, waves and sound. Each chapter includes a rich multimedia lesson of about 10 minutes, including film clips, animations, sound files and images of key experiments and demonstrations. Contextually embedded links lead to html pages providing broader and deeper support and, where needed, to tools such as calculus and vectors. The ongoing development of the interface reflects learner feedback and our own experience and research. The architecture and presentation of Physclips is largely consistent with evidence-based guidelines in the field of educational multimedia. Often, animations and labeling are superimposed on film clips to indicate abstract quantities, thus providing the novice with the insight of the expert's 'mind's eye'. The scrollbar is indexed with keywords and images to assist learners to find and to relocate conceptually discrete segments, which facilitates revision and reference usage. Together with extensive cross-linking, this allows students to construct individual learning pathways. Teachers download animations singly or in compressed folders for inclusion in lessons, blogs etc. Physclips is supported by Australia's Office of Learning and Teaching and the University of New South Wales.
Hot topics in speech communication: Listening to foreign-accented speech
Authors: Bent Tessa
Published: September 2012

There are currently more non-native English speakers in the world than there are native speakers. Most of these second language users will speak with a detectable foreign accent. Foreign-accented speech differs from native language norms along many acoustic-phonetic dimensions including the realization of vowel, consonant, and prosodic features. An important question for researchers in the field of speech communication is how this type of language variation influences speech perception and perceptual processing. Numerous findings have shown that foreign-accented speech is generally less intelligible, receives lower comprehensibility ratings, and is processed more slowly than native-accented speech. Further, these negative perceptual effects can be exacerbated by noisy listening conditions or listener variables such as age or hearing loss. However, research over the past several years has shown the amazing flexibility of the speech perception mechanism in its ability to adapt to this form of variability. Through experience and training, listeners can improve their word identification skills with specific foreign-accented talkers, particular foreign accents, and foreign-accented speech in general. New directions in this research area include perception of foreign-accented speech by infants and children as well as how a foreign accent may influence memory.
Photoacoustic tomography: Ultrasonically breaking through the optical diffusion limit
Authors: Wang Lihong
Published: September 2012

Photoacoustic tomography (PAT), combining optical and ultrasonic waves via the photoacoustic effect, provides in vivo multiscale non-ionizing functional and molecular imaging. Light offers rich tissue 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 the optical diffusion limit (~1 mm in the skin). In PAT, pulsed laser light penetrates the tissue and generates a small but rapid temperature rise, which induces emission of ultrasonic waves due to thermoelastic expansion. The ultrasonic waves, ~1000 times less scattering than optical waves in tissue, are then detected to form high-resolution images at depths up to 7 cm, breaking through the optical diffusion limit. PAT is the only modality capable of imaging across the length scales of organelles, cells, tissues, and organs with consistent contrast. Such a technology has the potential to enable multiscale systems biology and accelerate translation from microscopic laboratory discoveries to macroscopic clinical practice. PAT may also hold the key to the earliest detection of cancer by in vivo label-free quantification of hypermetabolism, the quintessential hallmark of cancer. The technology is commercialized by several companies.
Development of an advanced hearing protection evaluation system
Authors: Shank Kevin , Oliver Josiah
Published: September 2012

Acoustic Test Fixtures (ATFs) are practical and often necessary tools for testing Hearing Protection Devices (HPDs) especially with extremely loud impulsive and/or continuous noise, for which the use of live subjects might not be advisable. Although there have been various standardized and laboratory ATFs from past research, there still exists large uncertainty in the correlation between the attenuation results obtained from ATFs and those obtained from actual human subject tests, particularly for intraaural HPDs. It is suspected that one of the main factors contributing to the discrepancy may be insufficient fidelity in the circumaural/intraaural flesh and bone. Human subject testing was performed to obtain median parameters of ear canal geometry and eardrum reflectance, which are considered to be critical parameters for circumaural/intraaural HPD attenuation performance. This presentation discusses the research methodologies and design implementation of these important subsystems in this advanced Hearing Protection Evaluation System (HPES).
Two case studies for fit testing hearing protector devices
Authors: Murphy William J. , Themann Christa L. , Stephenson Mark R. , Byrne David C.
Published: September 2012

Hearing protection devices (HPDs) are typically selected based upon the Noise Reduction Rating (NRR) and, until recently, were rarely tested for attenuation in real-world environments. The National Institute for Occupational Safety and Health has developed a fit-testing system (HPD Well-Fit™) that performs attenuation tests with a large circumaural earmuff, a portable computer and a computer mouse with a scroll wheel. HPD Well-Fit was used to estimate the attenuation of employees working in two different settings: inspectors for off-shore drilling rigs and sandblasters at a hydroelectric facility. The highest exposure levels for the inspectors and sandblasters were estimated to be 110 and 130 dBA, respectively. Fit testing and training were used to achieve a 25-dB Personal Attenuation Rating (PAR) for the inspectors. Fit testing before and after the sandblaster work shift demonstrated PARs of 30 to 42 dB using HPD Well-Fit. The average time to complete the fit tests was 10 minutes. If retraining was necessary, then an additional 3 to 6 minutes were required.
Active average intensity based on single vector sensor
Authors: Du Pengyu , Zhang Xiao , Yin Jingwei , Han Xiao
Published: September 2012

Code divided multiple access underwater communication based on single vector sensor is studied in this paper. The most common methods to estimate azimuth with self-directivity of single vector sensor are average sound intensity method and complex sound intensity method, however, for the same frequency band multi-users, theoretical limitation for these methods is only two users.Spread spectrum communication is featured with strong anti-multipath, anti-interference, secret-keeping and communication web composing ability. Active average intensity method, which measures azimuths of multi-users simultaneously with the excellent correlative characteristics of pseudo-random code in spread spectrum communication, is proposed in this paper. Simulation and experiment for same frequency band spread spectrum multi-user communication testify the feasibility and utility of active average sound intensity method. With the estimated azimuth, vector combination can be generated to adjust the directivity of vector sensor, achieve multi-user beam communication, inhibit multi-path interference, and enhance processing gain and lower error rate. Key words: underwater acoustic communication; CDMA; single vector sensor; active acoustic intensity average
Research on multilevel differential amplitude and phase-shift keying in convolution-coded orthogonal frequency division multiplexing underwater communication system
Authors: Zhang Yuheng , Wang Chi , Yin Jingwei , Sheng Xueli
Published: September 2012

With the increasing demands of underwater source development and the increase of users, underwater transfer information has also greatly increased and high-bit-rate underwater acoustic communication has become a hot topic in underwater acoustic communication research. MDAPSK (Multilevel Differential Amplitude and Phase-shift Keying) is a modulation technique having high efficiency in spectrum utilization, which transfers information by using differential amplitude and phase code, demodulates information by adopting coherent demodulation. It reduces the difficulty of system, and improves the speed of transmission. While OFDM (Orthogonal Frequency Division Multiplexing) has advantages including high efficiency in spectrum and faster communication speed. After describing the schemes of the two technologies, a design scheme which concerns application of MDAPSK in the OFDM based underwater communication was given. The convolutional codes are also used in this system to realize the effectiveness and reliability in high-bit-rate underwater wireless communication. The computer simulation and the channel pool experimentation show that the system has a better performance. Key words: MDAPSK; OFDM; convolution coding; high-bit-rate communication
Application of orthogonal frequency division multiplexing in cognitive underwater communication
Authors: Wang Chi , Yin Jingwei , Du Pengyu , Guo Longxiang
Published: September 2012

With the development of underwater acoustic communication in military and commercial field and the urgent need for underwater wireless Ad Hoc networks, developing an intelligent and high-bit-rate underwater communication system is imminent. OFDM(Orthogonal Frequency Division Multiplexing) technology could be a good platform for cognitive underwater communication, which has advantages including high efficiency in spectrum utilization, faster communication speed and flexibility in choosing frequencies. A design scheme of the OFDM based cognitive underwater communication and block diagram are given. The system can intelligently choose NC-OFDM (Non-Contiguous OFDM), DOFDM (Differential OFDM) or Pilot-added OFDM communication schemes in order to meet different channel conditions and different rate requirements and to overcome the problem of data conflict and the waste of spectrum resources in multi-users’ competitive communication. Meanwhile, the system also can intelligently choose parameters in each scheme, such as sub-channel, pilot interval and error-correcting codes. The simulation results prove the feasibility and effectiveness of the OFDM based cognitive underwater communication.
Shallow water acoustic channel modeling with adaptive communications
Authors: Huang Xiaopeng
Published: September 2012

The underwater acoustic channel is known to be severely bandwidth limited due to sound attenuation by sea water, and interaction with the ocean surface and bottom. Yet, shallow water acoustic channels at high frequencies are little understood, particularly in shallow water environments, and hence the quest for achieving a viable adaptive communication solution has been a challenge that perplexed scientists for a long time. In this abstract, we first take Hodson River estuary as an example to investigate the characterizations of shallow water environments, which mainly comprises the evaluation of key channel parameters such as the scattering function, Doppler shift, coherent bandwidth, coherent time, 2D (i.e., Time-Frequency) time-variant channel impulse response (CIR). The study will also cover channel fading statistics, and water conditions that affect the CIR (e.g., bubble plumes and mddium inhomogeneities). Finally, the models developed will be used to evaluate the achievable performance of channel estimation and adaptive communication systems in shallow water acoustic media.
Hands-on demonstrations for Project Listen Up: Education outreach Part IV
Authors: Blackburn Jacqueline A. , Korman Murray S.
Published: September 2012

Acoustical demonstrations geared to promote a hands-on learning experience for middle- and high-school age Girl Scouts are setup. The participants will be free to explore, control the apparatus and make their own scientific discoveries. The hands-on demonstrations will include (1) a home-made electric slide guitar using easy to find parts, (2) a safe smoke ring generator and (3) a portable ripple tank with plastic eyedroppers for simple excitation of waves.
Hospital noise and staff performance
Authors: Messingher Gabriel , Ryherd Erica , Ackerman Jeremy
Published: September 2012

Hospitals are often noisy and not conducive to staff performance. Indeed, many staff believe that noise negatively affects their professional performance, quality of work, and ability to concentrate and communicate. Research shows that increased stress and annoyance, increased rates of burnout, and reduced occupational health are a few of the possible effects of hospital noise on staff. However, only a few hospital studies have directly linked noise to job performance. Results show that noise and distractions can potentially deteriorate mental efficiency and short-term memory and increase errors, but other studies have shown no significant effects. Alarm fatigue is also of concern, as staff may tune out, silence, or disable alarms because they are desensitized or exhausted by them. This paper will discuss what is currently known about hospital noise and staff performance and what questions remain. On-going studies relating the sound environment to staff performance in medical simulations will also be highlighted.
Designing quiet, healthy ductwork
Authors: Ayers Stephanie , Chusid Michael
Published: September 2012

Acoustical duct liners promote a healthier interior environment by suppressing mechanical noise from heating, ventilating, and air conditioning (HVAC) systems. However the materials used to reduce or control noise may, themselves, have health implications. Fibrous acoustical insulation, for example, can release fibers into the air stream during installation or maintenance and when subjected to high velocity air or vibration. Recent studies have determined that glass fiber - the most prevalent duct liner material - should not be listed as a carcinogen. However, glass fiber is an acknowledged irritant. Moreover, long-term effects on sensitive populations - including children and individuals with compromised immune systems - have not been studied. Fibrous insulation can collect dust, thereby providing a site for mold and microbial growth. And dislodged particles can disturb sensitive electronics and clean room conditions. Some owners of facilities such as hospitals, schools, and laboratories have, therefore, prohibited use of fibrous acoustical liners in ductwork. This paper discusses the application of acoustical duct liners, and the performance and use of alternatives to glass fiber in situations where non-fibrous liners are required.
On the Mach wave effect in impact pile driving, its observation, and its influence on transmission loss
Authors: Dahl Peter H. , Reinhall Per G.
Published: September 2012

Pile driving in water produces extremely high sound pressure levels in the surrounding underwater environment of order 10 kPa at ranges of order 10 m from the pile that can result in deleterious effects on both fish and marine mammals. In Reinhall and Dahl [J. Acoust. Soc. Am. 130, 1209-1216, Sep. 2011] it is shown that the dominant underwater noise from impact driving is from the Mach wave associated with the radial expansion of the pile that propagates down the pile at speeds in excess of Mach 3 with respect to the underwater sound speed. In this talk we focus on observations of the Mach wave effect made with a 5.6 m-length vertical line array, at ranges 8-15 m in waters of depth ~12.5 m. The key observation is the dominant vertical arrival angle associated with the Mach wave, ~17 deg., but other observations include: its frequency dependence, the ratio of purely waterborne energy compared with that which emerges from the sediment, and results of a mode filtering operation which also points to the same dominant angle. Finally, these observations suggest a model for transmission loss which will also be discussed. [Research supported by the Washington State Department of Transportation.]
Underwater sound from pile driving and protected marine species issues
Authors: Scholik-Schlomer Amy R. , Gedamke Jason
Published: September 2012

With current, wide-spread coastal construction projects and the predicted development of offshore wind energy, there are concerns regarding the potential impacts of underwater sound associated with pile driving activities on protected marine species. The National Marine Fisheries Service (NMFS) works to conserve, protect, and recover a variety of marine species, including marine mammals, marine and anadromous fishes, and sea turtles, protected under the Marine Mammal Protection Act (MMPA) and/or Endangered Species Act (ESA). In order to make management decisions for these protected species, we rely on scientific data to inform our policy. However, there are many challenges, including determining appropriate acoustic criteria and metrics for injury and behavioral harassment for impact and vibratory pile driving activities; understanding acoustic propagation in complex environments, especially shallow, coastal areas and throughout sediments; establishing appropriate protocols to mitigate and monitor impacts; and managing uncertainty for the broad number of species under our jurisdiction, who use and depend on sound (pressure and particle motion) in a variety of ways. Thus, we work collaboratively with other federal, state, and local government agencies, academia, nongovernmental agencies, and industry to best assess and manage risk from these activities.
Acoustical monitoring of resource conditions in U.S. National Parks
Authors: Fristrup Kurt M. , Lynch Emma , Joyce Damon
Published: September 2012

Several laws and derived policy direct the National Park Service to conserve and restore acoustic resources unimpaired for the enjoyment of future generations. The Natural Sounds and Night Skies Division has collected acoustical and related meteorological data at more than 300 sites in over 60 park units spanning the coterminous U. S., with additional sites in Alaska, Hawaii, and American Samoa. Analyses of these data reveal that background sound levels in many park units approach or fall below the human threshold of hearing, and that noise intrusions are ubiquitous. An emergent challenge is to develop efficient tools to reprocess these data to document bioacoustical activity. Generic indices of wildlife activity would be useful for examining responses to climate change, other anthropogenic disturbance, and changes in park unit management. Documentation of individual species occupancy and calling density would inform identification of habitat characteristics and management of species of special concern.
An auditory approach to understanding the effects of noise on communication in natural environments
Authors: Dooling Robert , Blumenrath Sandra , Smith Ed , Simmons Ryan , Fristrup Kurt
Published: September 2012

Animals, like humans, frequently communicate using long-range acoustic signals in networks of several individuals. In socially and acoustically complex environments, however, communication is characterized by a variety of perceptual challenges that animals strive to overcome in order to interact successfully with conspecifics. Species differences in auditory sensitivity and the characteristics of the environment are major factors in predicting whether environmental noise limits communication between animals or interferes with detection of other biologically important sounds. Working with both birds and humans and using both synthetic and natural noises in both laboratory and field tests, we have developed a model for predicting the effects of particular masking noises on animal communication. Moreover, by comparing birds listening to bird vocalizations in noise with humans listening to speech in noise, we gain a novel intuitive feel for the challenges facing animals in noisy environments. This approach of considering communication from the standpoint of the receiver provides a better approach for understanding the effects of anthropogenic noises that exceed ambient levels. For instance, in determining risk to a particular species, effective communication distances derived from this model might be compared to other aspects of the species biology such as territory size.
Echogenicity and release characteristics of folate-conjugated echogenic liposomes for cytosolic delivery of cancer drugs
Authors: Paul Shirshendu , Nahire Rahul , Mallik Sanku , Sarkar Kausik
Published: September 2012

Echogenic liposomes (ELIPs) are specially prepared liposomes that encapsulate both aqueous and gaseous phases. The presence of gas makes them echogenic. Since, ELIPs retain all the favorable properties of normal liposomes they can be used for simultaneous ultrasonic imaging and drug delivery applications. These liposomes are polymerized on the external leaflet using a disulphide linker. Disulphide bonds are reversibly broken in presence of thiol above a critical concentration. Therefore, the liposomes are stable in the plasma (thiol concentration 10 μM) but release its content inside the cell (thiol concentration 10 mM). The liposome also expresses folate group on its surface which allows its entry into the cancer cells. The release can be controlled by diagnostic frequency ultrasound. Therefore, these ELIPs hold promises for ultrasound image-guided cytosolic delivery for cancer drugs. We will report on their acoustic properties and ultrasound-mediated release characteristics. Their implications on design and development of these novel contrast agents will be discussed. [Supported by NSF CBET-0651912, CBET-1033256, DMR-1005283.]
High-frequency harmonic imaging with coded excitation: Implications for the assessment of coronary atherosclerosis
Authors: Shekhar Himanshu , Doyley Marvin M.
Published: September 2012

The adventitial vasa vasorum grows abnormally in life-threatening atherosclerotic plaques. Harmonic intravascular ultrasound (H-IVUS) could help assess the vasa vasorum by nonlinear imaging of microbubble contrast agents. However, the harmonics generated in tissue at high acoustic pressures compromise the specificity of H-IVUS - a trait that has hampered its clinical use. Therefore, H-IVUS should be conducted at low pressure amplitudes; but the resulting decrease in signal-to-noise ratio (SNR) could limit the sensitive detection of the vasa vasorum. In this study, we investigated the feasibility of improving the SNR of H-IVUS imaging with chirp-coded excitation. Numerical simulations and experiments were conducted to assess the harmonic response of the commercial contrast agent Targestar-p™, to sine-burst and chirp-coded excitation (center frequencies 10 and 13 MHz, peak-pressures 100 to 300 kPa). We employed 1) a single-element transducer pair, and 2) a dual-peak frequency transducer for our studies. Our experimental results demonstrated that exciting the agent with chirp-coded pulses can improve the harmonic SNR by 7 to 14 dB. Further, the axial resolution obtained with chirp-coded excitation was within 10% of that expected for sine-burst excitation. Therefore, we envisage that chirp-coded excitation may be a viable strategy to visualize the vasa vasorum with H-IVUS imaging.
Cavitation mechanisms in ultrasound-enhanced permeability of ex vivo porcine skin
Authors: Rich Kyle T. , Hoerig Cameron L. , Mast T. Douglas
Published: September 2012

Ultrasound-induced cavitation is known to enhance transdermal transport of drugs for local and systemic delivery. However, the specific cavitation mechanisms responsible are not well understood, and the physical location of permeability-enhancing cavitation is also unknown. The experiments reported here investigated the role of stable and inertial cavitation, both within the skin and at the dorsal skin surface, in ultrasound enhancement of skin permeability. Full-thickness porcine skin was hydrated with either air-saturated phosphate buffered saline (PBS) or vacuum-degassed PBS to localize cavitation activity within or outside the skin, respectively. Skin samples were sonicated for 30 minutes over a range of frequencies (0.41 and 2.0 MHz) and peak rarefactional pressure amplitudes (0-750 kPa) with a 20% duty cycle (1 s on, 4 s off). Cavitation activity was monitored using a 1.0 MHz unfocused, wideband passive cavitation detector (PCD). Changes in skin permeability were quantified by measuring the electrical resistance of skin every 10 seconds during insonation. Subharmonic acoustic emissions revealed a strong correlation with decreasing electrical resistance of skin when cavitation was isolated within the tissue, suggesting that stable cavitation within the skin plays a primary role in ultrasound-enhanced permeability over the frequencies investigated.
Laser-induced-cavitation enhanced ultrasound thrombolysis
Authors: Cui Huizhong , Yang Xinmai
Published: September 2012

Application of ultrasound (US) is considered as an effective way to dissolve thrombus. Cavitation has been demonstrated to be significant to enhance thrombolytic efficacy. In this study, to improve the efficacy of this thrombolytic therapy, 764-nm laser light was used to induce cavitation in the US thrombolysis. Porcine clots were cut into small pieces and inserted into small tubes, then placed in the focal zone of a 1-MHz high-intensity focused ultrasound (HIFU) transducer in a water tank. At the same time, a 10-Hz laser system, which is confocal with the HIFU transducer, was used to illuminate on the focal area of the model during thrombolysis. After thrombolysis, the debris of clots was weighed to calculate the weight loss. Both US thrombolysis with and without laser illumination were performed in the experiment. Different combinations of peak-to-peak ultrasound pressure amplitude, duty cycle and duration were used. It is shown that the clot mass loss increased significantly when the laser illumination presented during the US thrombolysis process. The preliminary experimental results indicated that laser induced cavitation may play an important role in the enhancement of US thrombolysis.
Elasto-acoustic response of a rib-stiffened multi-layer Hull system
Authors: Lucifredi Irena , Nagem Raymond J. , Lucifredi Federico
Published: September 2012

The analysis of hull vibrations has been a long-standing topic of interest in the US Navy for both surface and underwater vehicles. Understanding of the physics controlling acoustic scattering and radiation from coated, fluid-loaded structures is important as it can provide the required knowledge of the self-noise modeling of hull arrays and of the acoustic target strength of the submersibles. Currently, models are typically limited to low frequency regime of operation, not being able to consider a broad mid-high frequency range, commonly rich in physical phenomena that characterize sound fields in underwater vehicle environments. The goal of this effort is to provide a robust, innovative, and computationally efficient tool for analytical modeling of a fluid-loaded acoustic coating affixed to a rib-stiffened backing plate, capable of representing high frequency acoustic environments not suitable for conventional finite element approaches.The approach taken in this effort is based on the A.J. Hull’s derivation of the elastic response of a layered sonar system on a rib-stiffened plate, and it is centered on the reformulation of the layered system response problem using displacement and stress variables.The new approach produces a significant improvement in the stability, efficiency, and accuracy of the computational method.
Vibro-acoustic response of an infinite, rib-stiffened, thick-plate assembly using finite-element analysis
Authors: Remillieux Marcel C.
Published: September 2012

The vibration of and sound radiation from an infinite, fluid-loaded, thick-plate assembly stiffened periodically with ribs are investigated numerically using finite element (FE) analysis. The analysis is conducted in two-dimensions using plane-strain deformation to model the dynamics of the structure. Advantage is taken of the periodicity of the system to deal with the infinite dimensions of the model through the use of periodic boundary conditions. Firstly, numerical simulations are used to validate the analytical solutions derived recently for this particular problem by Hull and Welch [Elastic response of an acoustic coating on a rib-stiffened plate, Journal of Sound and Vibration 329 (2010) 4192-4211]. Numerical and analytical solutions are in excellent agreement, provided that the number of modes in the analytical model is chosen correctly. Through this validation effort it is also demonstrated that the analytical model is sensitive to the number of modes used to formulate the solution, which may result in some instabilities related to mode count. Subsequently, the numerical model is used to study the effect of repeated and equally spaced void inclusions on the vibro-acoustic response of the system.
Damping of flexural vibrations in glass fiber composite plates and honeycomb sandwich panels containing indentations of power-law profile
Authors: Bowyer Elizabeth P. , Nash Peter , Krylov Victor V.
Published: September 2012

In this paper, the results of the experimental investigation into the addition of indentations of power-law profile into composite plates and panels and their subsequent inclusion into composite honeycomb sandwich panels are reported. The composite plates in question are sheets of composite with visible indentations of power-law profile. A panel is a sheet of composite with the indentations encased within the sample. This makes a panel similar in surface texture to an un-machined composite sheet (reference plate) or conventional honeycomb sandwich panel. In the case of quadratic or higher-order profiles, the above-mentioned indentations act as two-dimensional acoustic black holes for flexural waves that can absorb a large proportion of the incident wave energy. For all the composite samples tested in this investigation, the addition of two-dimensional acoustic black holes resulted in further increase in damping of resonant vibrations, in addition to the already substantial inherent damping due to large values of the loss factor for composites. Due to large values of the loss factor for composite materials used, no increase in damping was seen with the addition of a small amount of absorbing material to the indentations, as expected.
Sound radiation of rectangular plates containing tapered indentations of power-law profile
Authors: Bowyer Elizabeth P. , Krylov Victor V.
Published: September 2012

In this paper, the results of the experimental investigations into the sound of rectangular plates containing tapered indentations of power-law profile are reported. Such tapered indentations materialise two-dimensional acoustic black holes for flexural waves that result in absorption of a large proportion of the incident wave energy. A multi-indentation plate was compared to a plain reference plate of the same dimensions, and the radiated sound power was determined (ISO 3744). It was demonstrated that not only do such multiple indentations provide substantial reduction in the damping of flexural vibrations within the plates, but also cause a substantial reduction in the radiated sound power. As the amplitudes of the flexural vibrations of a plate are directly linked to the amplitude of radiated sound from the same plate, this paper also considers the effect of distribution of the amplitude of the plate’s response on the amplitudes of the radiated sound. This investigation concludes that, despite an increase in the amplitude of the displacement at the indentation tip, the overall reduction in the constant thickness of the plate is large enough to result in substantial reductions in the overall vibration response and in the resulting sound radiation of plates containing indentations of power-law profile.
The nature and perception of human musical rhythms
Authors: Hennig Holger , Fleischmann Ragnar , Fredebohm Anneke , Hagmayer York , Nagler Jan , Witt Annette , Theis Fabian J. , Geisel Theo
Published: September 2012

Although human musical performances represent one of the most valuable achievements of mankind, the best musicians perform imperfectly. Musical rhythms are not entirely accurate and thus inevitably deviate from the ideal beat pattern. Nevertheless, computer generated perfect beat patterns are frequently devalued by listeners due to a perceived lack of human touch. Professional audio editing software therefore offers a humanizing feature which artificially generates rhythmic fluctuations. However, the built-in humanizing units are essentially random number generators producing only simple uncorrelated fluctuations. Here, for the first time, we establish long-range fluctuations as an inevitable natural companion of both simple and complex human rhythmic performances [1,2]. Moreover, we demonstrate that listeners strongly prefer long-range correlated fluctuations in musical rhythms. Thus, the favorable fluctuation type for humanizing interbeat intervals coincides with the one generically inherent in human musical performances. [1] HH et al., PLoS ONE,6,e26457 (2011). [2] Physics Today, invited article, submitted (2012).
Heartbeat and ornaments: More technical secrets of swing rhythm
Authors: Lindsay Ken , Nordquist Pete
Published: September 2012

We previously demonstrated technically precise methods characterizing various types of Swing style in music. Our primary tool is “diffdot” notation showing, in graphical form, the exact timing relationships between various musical notes that create a specific musical phrase. We have shown several common and obvious details of Swing, all based on time variations from a uniform square grid (Classical Mozart/Bach). Micro-timing variations are generally recognized as being essential to Swing. There may be other elements which define Swing feeling but we have focused on micro-timing details. These are a fruitful source for technical analysis of Swing styles.Triplet subdivision is often associated with Swing -- Jazz, Blues -- but triplets are neither necessary nor sufficient to distinguish a performance as “Swing” versus “Straight” time. One seemingly universal detail of Swing is an asymmetrical “pulse” or basic beat, e.g. on the downbeat of every measure, or the one and three beat in a 4/4 piece. The time between the two heartbeat notes as they repeat their cycle is not equal. This gives rise to unmistaken Swing. Other non-uniform but precisely repeated timing patterns characterize Swing at hierarchical levels different from pulse. These we call “ornaments” in keeping with common musical jargon.
Rhythm and meter in 21st century music theory
Authors: London Justin
Published: September 2012

Theories of rhythm in western music go back to Aristoxenus (335 BC) and have continued unabated to the present day. Yet while music theoretic discussions of melody and harmony since Pythagoras have often looked to mathematics and acoustics, only recently has music theory availed itself of research in acoustics, psychoacoustics, and auditory psychology. The central question for a theory of musical rhythm is “what makes something regular enough to be considered a rhythm?” Answering this question requires not only a knowledge of music in a range of musical styles and cultures, but also understanding of our basic psychological capacities for temporal perception and discrimination, as well as our perceptual biases and habits. A brief outline of recent theories of rhythm and meter that draw upon these domains will be presented, with an emphasis on musical meter as kind of entrainment, that is, a synchronization of our attending and/or sensorimotor behaviors to external periodicities in a particular temporal range.
Impact and revision of UK legislation on school acoustics
Authors: Shield Bridget M. , Conetta Robert
Published: September 2012

Since 2003 new school buildings in England and Wales have been subject to Building Regulations which impose a legal requirement for spaces in schools to meet acoustic performance criteria for ambient noise levels, reverberation times and sound insulation. The criteria are specified in the Department of Education publication ‘Building Bulletin 93’ (BB93). In 2008 it was agreed that BB93 would be updated. The Labour government endorsed the need for good acoustic design of schools and agreed to a minor revision of the legislation. However, the new government elected in 2010 recommended the removal of legislation on school acoustics, in order to reduce the cost of new school buildings. The acoustics community in the UK successfully lobbied the government to keep the legislation and it has been agreed that the acoustic regulations relating to the performance of a building in use will be retained. BB93 is currently (June 2012) being redrafted and the acoustic performance specifications revised. This paper will use the results of a recent large scale survey of the acoustics of secondary schools in the UK to examine the impact of BB93 on school design over the past 10 years, and will discuss the current revision of the legislation.
Acoustic design of a new elementary school to meet high performance prerequisites using a school districts base design: Predictions and results from commissioning
Authors: Pettyjohn Steve
Published: September 2012

An architectural firm was selected to design a new elementary school using the school district’s standard building, but with modifications to meet the prerequisites of the Collaborative for Performance Schools (CHPS). Two acoustic prerequisites are a part of the CHPS programs including a background limit of 45 dB(A) and a reverberation time of 0.6 seconds. A 2-story design forms the basis of design. First tests were done at an existing elementary school with the same design. Acoustical recommendations for wall designs, room finishes and HVAC design were incorporated into the design and construction of the new school. The school was not near significant transportation noise sources. After construction was mostly complete, tests were done to learn the sound transmission loss of walls and floor/ceiling systems. Reverberation time tests and background sound levels were measured after construction was complete. Background sound met design goals in all but one space except for the sound generated by a wind turbine mounted on one end of the buildings. This was added by the schools Principal during the latter part of construction without consulting everyone. This proved to be a significant source that had to be removed.
Modeling the generation of infrasound from earthquakes
Authors: Arrowsmith Stephen , Burlacu Relu , Pankow Kristine , Stump Brian , Stead Richard , Whitaker Rod , Hayward Chris
Published: September 2012

Earthquakes can generate complex seismo-acoustic wavefields, consisting of seismic waves, epicenter-coupled infrasound, and secondary infrasound. We report on the development of a numerical seismo-acoustic model for the generation of infrasound from earthquakes. We model the generation of seismic waves using a 3D finite difference algorithm that accounts for the earthquake moment tensor, source time function, depth, and local geology. The resultant acceleration-time histories (on a 2D grid at the surface) provide the initial conditions for modeling the near-field infrasonic pressure wave using the Rayleigh integral. Finally, we propagate the near-field source pressure through the Ground-to-Space atmospheric model using a time-domain parabolic equation technique. The modeling is applied to an earthquake of MW 4.6, that occurred on January 3, 2011 in Circleville, Utah; the ensuing predictions are in good agreement with observations made at the Utah network of infrasonic arrays, which are unique and indicate that the signals recorded at 6 arrays are from the epicentral region. These results suggest that measured infrasound from the Circleville earthquake is consistent with the generation of infrasound from body waves in the epicentral region.
Observation of the Young-Bedard Effect during the 2010 and 2011 Atlantic Hurricane Seasons
Authors: Blom Philp , Waxler Roger , Frazier William Garth , Talmadge Carrick
Published: September 2012

Infrasonic acoustic energy is known to be generated during the collision of counter propagating ocean surface waves of like periods. The acoustic signals produced by such collisions are known as microbaroms. One significant source of microbarom radiation is the interaction of waves produced by large maritime storms with the background ocean swell. The region in which the microbaroms associated with a large storm are produced tends to be hundreds of kilometers from the eye of the storm. It was suggested by Young and Bedard that, when observed along propagation paths that pass through the storm, the microbarom signal can be severely refracted by the storm itself. Such refraction has been observed in data from the 2010 and 2011 Atlantic hurricane seasons. A data processing algorithm has been developed and implemented using the Multiple Signal Classification (MUSIC) spatial spectra and Akaike Information Criterion. The results of this analysis will be presented and compared with predictions of the refraction using a geometric acoustics propagation model.
Validating infrasound sensor performance: Requirements, specifications, and calibration
Authors: Hart Darren M. , Whitaker Rod , Parks Harold
Published: September 2012

The Ground-Based Nuclear Explosion Monitoring Research and Development (GNEM R&D) program at Sandia National Laboratories (SNL) is regarded as a primary center for unbiased expertise in testing and evaluation of geophysical sensors and instrumentation for nuclear explosion monitoring. In the area of Infrasound sensor evaluation, Sandia relies on the “comparison calibration” technique to derive the characteristics of a new sensor under evaluation relative to a standard reference infrasound sensor. The traceability of our technique to a primary standard is partially dependent on the infrasound calibration chamber operated by a similar program group at Los Alamos National Laboratory (LANL). Previous work by LANL and the SNL Primary Standards Laboratory was able to determine the LANL chamber pistonphone output pressure level to within 5% uncertainty including dimensional measurements and careful analysis of the error budget. Over the past several years, the staff at LANL and the SNL Facility for Acceptance, Calibration and Testing (FACT) site has been developing a methodology for the systematic evaluation of infrasound sensors. That evaluation involves making a set of measurements that follow a prescribed set of procedures, allowing traceability to a primary standard for amplitude. Examples of evaluation tests will be shown for monitoring quality infrasound sensors.
Noise reduction optimization of wind fences
Authors: Abbott JohnPaul R. , Raspet Richard , Webster Jeremy
Published: September 2012

An earlier paper [J. Acoust. Soc. Am. 129, 2445 (2011)] described an investigation on the optimization of a large wind screen for infrasonic noise reduction. This wind screen is a circular variable porous enclosure 3 m high and 5 m in diameter consisting of ten chain link fence panels about 3 m high and 1.5 m wide, with removable vinyl privacy slats, an open top, and a 0.1 m bottom gap. That paper reported on the noise reduction for a microphone set at the center of the enclosure relative to another set outside the enclosure as the screen’s porosity was varied. Both microphones were mounted under porous foam flush to the ground. It was shown that the best reductions occurred at intermediate porosities, with reductions of 6 dB or greater between 0.6 -10 Hz, with max reductions about 13-15 dB. The current paper will report on the effect of further optimization techniques—sealing off the bottom gap, adding a roof, and placing a small porous dome over the enclosed field microphone. Of these techniques the addition of the dome was most effective, with noise reductions of 6 dB or greater between 0.3-10 Hz, with max reductions about 20-23 dB.
Direct measurement of the acoustical impedance of wind-noise-reduction pipe systems
Authors: Gabrielson Thomas B. , Poese Matthew
Published: September 2012

Wind-noise-reduction systems for infrasound monitoring stations often take the form of networks of pipes and cavities. The acoustical response of these wind-noise-reduction systems can be determined using ambient noise and comparison to a reference sensor. Faults in these systems can sometimes be detected by such response measurements; however, identification and localization of a fault is more challenging. Another approach for performance assessment is to measure the acoustical impedance at accessible points in the pipe network. This approach has the potential for high signal-to-noise ratio, less dependence on atmospheric conditions, and the ability to isolate sub-sections of the network. A portable apparatus has been designed for field measurement of acoustical impedance. The impedance apparatus generates a controlled volume velocity and measures acoustic pressure at the driving point.
Auditory brainstem responses evoked by chirp and click stimuli in children
Authors: Bargen Gabriel A.
Published: September 2012

The chirp-evoked auditory brainstem response (ABR) has been found to be a more synchronous response in adults than the click-evoked ABR with more areas of the cochlea contributing to the compound ABR. ABRs evoked using delayed-model chirp stimuli have shown to compensate for the temporal dispersion of the cochlea and result in larger wave V amplitudes and better overall morphology when compared to click-evoked ABRs. To date, published research has only included adult subjects with the majority of studies completed on subjects with normal hearing. This study compares the chirp-evoked ABR to the click-evoked ABR in children to determine if the chirp-evoked stimulus is more efficient than the click-stimulus which is currently used in most newborn hearing screening protocols and pediatric diagnostic ABR evaluations. Subjects from birth to eight years of age, with normal and abnormal hearing, participated in this study. This presentation will include preliminary study findings.
Improving the discriminability of simultaneous auditory alarms using principles of voice-leading found in music
Authors: Davis Matthew J. , Klyn Nial
Published: September 2012

Predicting the ability of listeners to discriminate between simultaneous auditory streams is a longstanding challenge in the design of auditory displays. The creation of an efficacious artificial auditory scene can require an immense amount of knowledge about how sounds are heard and interpreted; what is commonly called auditory scene analysis. Fortunately, musicians have been constructing novel auditory scenes with multiple simultaneous streams for many centuries, and the rules governing the composition of Western polyphonic music have even been explicitly codified in a range of techniques referred to as “voice-leading”. These relatively simple but effective rules have the potential to help guide designers of auditory displays by maximizing the distinctions between concurrent signals. An experiment was conducted to measure the discriminability of alarms designed with musical “voice-leading” features as compared with existing alarms from Learjet 31a and Learjet 35 aircraft. Signals designed with the auditory scene synthesis techniques embedded in musical “voice-leading” were found to significantly improve discriminability for up to five simultaneous alarms. By applying these principles to warning signals, this study has sought to implement a system for creating new auditory warnings that contain more efficient differentiating properties and furthermore conform to a more unified stylistic identity.