bluuebunny/crossref_metadata_2025 huggingface dataset:
Transition of steady air flow into an anharmonic acoustic pulsed flow in a prototype reactor column: Experimental results and mathematical modeling
Authors: Tavossi Hasson M.
Published: October 2014

A prototype experimental setup is designed to convert steady air flow into an oscillatory anharmonic acoustic pulsed flow, under special experimental conditions. The steady flow in a cylindrical reactor column of 3 m height and 15 cm in diameter with a porous layer, transforms itself abruptly into an oscillatory acoustic pulsed flow. Experimental results show the existence of a threshold for flow-rate, beyond which this transformation into anharmonic oscillatory flow takes place. This change in flow regime is analogous to the phenomenon of bifurcation in a chaotic system, with abrupt change from one energy state into another. Experimental results show that the acoustic oscillations amplitude depends on system size. Preliminary mathematical model will be presented that includes; relaxation oscillations, non-equilibrium thermodynamics, and Joule-Thomson effect. The frequencies at peak amplitude for the acoustic vibrations in the reactor column are expressed in terms of flow-rate, pressure-drop, viscosity, and dimensionless characteristic numbers of the air flow in the system.
Design of an experiment to measure unsteady shear stress and wall pressure transmitted through an elastomer in a turbulent boundary layer
Authors: Smith Cory J. , Capone Dean E. , Brungart Timothy A.
Published: October 2014

A flat plate that is exposed to a turbulent boundary layer (TBL) experiences unsteady velocity fluctuations which result in fluctuating wall pressures and shear stresses on the surface of the plate. There is an interest in understanding how fluctuating shear stresses and normal pressures generated on the surface of an elastomer layer exposed to a TBL in water are transmitted through the layer onto a rigid backing plate. Analytic models exist which predict these shear stress and normal pressure spectra on the surface of the elastomer as well as those transmitted through the elastomer. The design of a novel experiment is proposed which will utilize Surface Stress Sensitive Films (S3F) to measure the fluctuating shear stress and hydrophones to measure fluctuating normal pressure at the elastomer-plate interface. These experimental measurements would then be compared to models of unsteady shear and unsteady pressure spectra within a TBL for purposes of model validation. This work will present the design of an experiment to measure the unsteady pressure and unsteady shear at the elastomer-plate interface and the methodology for comparing the measured results to the analytic model predictions.
Exploration into the sources of error in the two-microphone transfer function impedance tube method
Authors: Hall Hubert S. , Vignola Joseph , Judge John , Turo Diego
Published: October 2014

The two-microphone transfer function method has become the most widely used method of impedance tube testing. Due to its measurement speed and ease of implementation, it has surpassed the standing-wave ratio method in popularity despite inherent frequency limitations due to tube geometry. Currently, the two-microphone technique is described in test standards ASTM E1050 and ISO 10534-2 to ensure accurate measurement. However, while detailed for correct test execution, the standards contain vague recommendations for a variety of measurement parameters. For instance, it is only stated in ASTM E1050 that “tube construction shall be massive so sound transmission through the tube wall is negligible.” To quantify this requirement, damping of the tube was varied to determine how different loss factor values effect measured absorption coefficient values. Additional sources of error explored are the amount of required absorbing material within the tube for reflective material measurements, additional calibration methods needed for test of excessive reflective materials, and alternate methods of combating microphone phase error and tube attenuation.
The impact of CrossFit training—Weight drops on floating floors
Authors: Sherren Richard S.
Published: October 2014

CrossFit training is a popular fitness training method. Some facilities install lightweight plywood floating floor systems as a quick, inexpensive method to mitigate impact generated noise and vibration into adjoining spaces. Part of the CrossFit training regimen involves lifting significant weight overhead, and then dropping the weight on the floor. The energy transferred to the floor system can cause severe damage to floor surfaces and structures; and, when using a lightweight floating floor system, even the isolators can be damaged. This paper describes a spreadsheet based analytical model being used to study the effects of such impacts on various floor systems. This study is a prelude to experiments that will be performed on a full scale model test floor. The results of those experiments will be used to verify the model so that it can be used as a design tool for recommending solutions for mitigating the noise and vibration in adjoining spaces due to floor impact problems. Also discussed in this paper are the qualitative results of some preliminary tests performed in order to better understand the mechanics of impacts on floating floor assemblies.
Stethoscope-based detection of detorqued bolts using impact-induced acoustic emissions
Authors: Guarino Joe , Hamilton Robert
Published: October 2014

Non-invasive impact analysis can be used to detect loosened bolts in a steel structure composed of construction-grade I beams. An electronically enhanced stethoscope was used to acquire signals from a moderate to light impact of a hammer on a horizontal steel I beam. Signals were recorded by placing the diaphragm of the stethoscope on the flange of either the horizontal beam or the vertical column proximal to a bolted connection connecting the two members. Data were taken using a simple open-loop method; the input signal was not recorded, nor was it used to reference the output signal. The bolted connection had eight bolts arranged in a standard configuration. Using the “turn of the nut” standard outlined by the Research Council on Structural Connections (RCSC, TDS-012 2-18-08), the bolted joint was tested in three conditions: turn of the nut tight, finger tight, and loose. We acquired time-based data from each of 52 patterns of the eight bolts in three conditions of tightness. Results of both time and frequency-based analyses show that open-loop responses associated with detorqued bolts vary in both amplitude decay and frequency content. We conclude that a basic mechanism can be developed to assess the structural health of bolted joints. Results from this project will provide a framework for further research, including the analysis of welded joints using the same approach.
Investigation of damping in the polymer concrete sleeper for use in reduction of rolling noise from railway
Authors: Ahn SangKeun , Jeon Eunbeom , Park Junhong , Kim Hak-sung , Kho Hyo-in
Published: October 2014

The purpose of this study was to measure damping of various polymer concretes to be used as sleepers for railway. The polymer concretes consisted of epoxy monomer, hardener and aggregates. Various polymer concrete specimens were made by changing epoxy resin weight ratio and curing temperature. The dynamic properties of the polymer concrete specimens were measured by using beam-transfer function method. To predict reduction performance of the polymer concrete sleepers, an infinite Timoshenko beam model was investigated after applying measured concrete properties. The moving loads from rotating wheels on railway due to different roughness were utilized in railway vibration analysis. The vibration response was predicted from which the effects of supporting stiffness and loss factor of sleeper were investigated. The radiated sound power was predicted using calculated rail vibration response. Consequently, the sound power levels were compared for rails supported by different polymer concrete sleepers. The result of this study assists constructing low noise railway.
Study on impulsive noise radiation from of gasoline direct injector
Authors: Kwak Yunsang , Park Junhong
Published: October 2014

A gasoline direct injection (GDI) engine uses its own injectors for high pressure fuel supply to the combustion chamber. High frequency impact sound during the injection process is one of the main contributors to engine combustion noise. This impact noise is generated during opening and closing by an injector rod operated by a solenoid. For design of an injector with reduced noise generation, it is necessary to analyze its sound radiation mechanism and propose consequent evaluation method. Spectral and modal characteristics of the injectors were measured through vibration induced by external hammer excitation. The injector modal characteristics were analyzed using a simple beam after analyzing its boundaries by complex transverse and rotational springs. To evaluate impulsive sounds more effectively, Prony analysis of sounds was used for verifying influence of injector modal characteristics.
Vowel intelligibility and the second-language learner
Authors: Rogers Catherine L.
Published: October 2014

Diane Kewley-Port’s work has contributed to our understanding of vowel perception and production in a wide variety of ways, from mapping the discriminability of vowel formants in conditions of minimal uncertainty to vowel processing in challenging conditions, such as increased presentation rate and noise. From the results of these studies, we have learned much about the limits of vowel perception for normal-hearing listeners and the robustness of vowels in speech perception. Continuously intertwined with this basic research has been its application to our understanding of vowel perception and vowel acoustics across various challenges, such as hearing impairment and second-language learning. Diane’s work on vowel perception and production by second-language learners and ongoing research stemming from her influence will be considered in light of several factors affecting communicative success and challenge for second-language learners. In particular, we will compare the influence of speaking style, noise, and syllable disruption on the intelligibility of vowels perceived and produced by native and non-native English-speaking listeners.
Vowel formant discrimination: Effects of listeners’ hearing status and language background
Authors: Liu Chang
Published: October 2014

The goal of this study was to examine effects of listeners’ hearing status (e.g., normal and impaired hearing) and language background (e.g., native and non-native) on vowel formant discrimination. Thresholds of formant discrimination were measured for F1 and F2 of English vowels at 70 dB SPL for normal- (NH) and impaired-hearing (HI) listeners using a three-interval, two-alternative forced-choice procedure with a two-down, one-up tracking algorithm. Formant thresholds of HI listeners were comparable to those of NH listeners for F1, but significantly higher than NH listeners for F2. Results of a further experiment indicated that an amplification of the F2 peak could markedly improve formant discrimination for HI listeners, but a simple amplification of the sound level did not provide any benefit to them. On the other hand, another experiment showed that vowel density of listeners’ native language appeared to affect vowel formant discrimination, i.e., more crowded vowel space of listeners’ native language, better their vowel formant discrimination. For example, English-native listeners showed significantly lower thresholds of formant discrimination for both English and Chinese vowels than Chinese-native listeners. However, the two groups of listeners had similar psychophysical capacity to discriminate formant frequency changes in non-speech sounds.
Distributions of confusions for the 109 syllable constituents that make up the majority of spoken English
Authors: Miller James D. , Watson Charles S. , Sillings Roy
Published: October 2014

Among the interests of Kewley-Port have been the perception and production of English Speech Sounds by native speakers of other languages. ESL students from four language backgrounds (Arabic, Chinese, Korean, and Spanish) were enrolled in a speech perception training program. Similarities and differences between these L1 groups in their primary confusions were determined for onsets, nuclei and codas utilized in spoken English. An analysis in terms of syllable constituents is more meaningful than analyses in terms of phonemes as individual phonemes have differing articulatory and acoustic structures depending on their roles in the syllable and their phonetic environments. An important observation is that only a few of all the possible confusions that might occur do occur. Another interesting characteristic of confusions among syllable constituents is that many more confusions are observed than those popularly cited, e.g., the /r/ v /l/ for Japanese speakers. As noted by many, the perceptual problems encountered by learners of English are conditioned on the relations between the sound-structures of English with each talker’s L1. These data suggest that the intrinsic similarities within of the sounds of English also play an important role.
Identification and response latencies for Mandarin-accented isolated words in quiet and in noise
Authors: Dalby Jonathan , Barcenas Teresa , August Tanya
Published: October 2014

This study compared the intelligibility of native and foreign-accented American English speech presented in quiet and mixed with two different levels of background noise. Two native American English speakers and two native Mandarin Chinese speakers for whom English is a second language read three 50-word lists of phonetically balanced words (Stuart, 2004). The words were mixed with noise at three different signal-to-noise levels—no noise (quiet), SNR + 10 dB (signal 10 dB louder than noise) and SNR 0 (signal and noise at equal loudness). These stimuli were presented to ten native American English listeners who were simply asked to repeat the words they heard the speakers say. Listener response latencies were measured. The results showed that for both native and accented speech, response latencies increased as the noise level increased. For words identified correctly, response times to accented speech were longer than for native speech but the noise conditions affected both types equally. For words judged incorrectly, however, the noise conditions increased latencies for accented speech more than for native speech. Overall, these results support the notion that processing accented speech requires more cognitive effort than processing native speech.
Individual differences in the perception of nonnative speech
Authors: Bent Tessa
Published: October 2014

As a mentor, Diane Kewley-Port was attentive to each student’s needs and took a highly hands-on, individualized approach. In many of her collaborative research endeavors, she has also taken a fine-grained approach toward both discovering individual differences in speech perception and production as well as explaining the causes and consequences of this range of variation. I will present research investigating several cognitive-linguistic factors that may contribute to individual differences in the perception of nonnative speech. Recognizing words from nonnative talkers can be particularly difficult when combined with environmental degradation (e.g., background noise) or listener limitations (e.g., child listener). Under these conditions, the range of performance across listeners is substantially wider than observed under more optimal conditions. My work has investigated these issues in monolingual and bilingual adults and children. Results have indicated that age, receptive vocabulary, and phonological awareness are predictive of nonnative word recognition. Factors supporting native word recognition, such as phonological memory, were less strongly associated with nonnative word recognition. Together, these results suggest that the ability to accurately perceive nonnative speech may rely, at least partially, on different underlying cognitive-linguistic abilities than those recruited for native word recognition. [Work supported by NIH-R21DC010027.]
An intuitive look at the unscented Kalman filter
Authors: Sullivan Edmund
Published: October 2014

The Unscented Kalman Filter or UKF is a powerful and easily used modification to the Kalman filter that permits it use in the case of a nonlinear process or measurement model. Its power lies in its ability to allow the mean and covariance of the data to be correctly passed through a nonlinearity, regardless of the form of the nonlinearity. There is a great deal of literature on the UKF that describes the method and gives instruction on its use, but there are no clear descriptions on why it works. In this paper, we show that by computing the mean and covariance as the expectations of a Gaussian process, passing the results through a nonlinearity and solving the resulting integrals using Gauss-Hermite quadrature, the reason for the ability of the UKF to maintain the correct mean and covariance is explained by the fact that the Gauss-Hermite quadrature uses the same abscissas and weights regardless of the form of the integrand.
Experimental investigations on coprime microphone arrays for direction-of-arrival estimation
Authors: Bush Dane R. , Xiang Ning , Summers Jason E.
Published: October 2014

Linear microphone arrays are powerful tools for determining the direction of a sound source. Traditionally, uniform linear arrays (ULA) have inter-element spacing of half of the wavelength in question. This produces the narrowest possible beam without introducing grating lobes—a form of aliasing governed by the spatial Nyquist theorem. Grating lobes are often undesirable because they make direction of arrival indistinguishable among their passband angles. Exploiting coprime number theory, however, an array can be arranged sparsely with fewer total elements, exceeding the aforementioned spatial sampling limit separation. Two sparse ULA sub-arrays with coprime number of elements, when nested properly, each produce narrow grating lobes that overlap with one another exactly in just one direction. By combining the sub-array outputs it is possible to retain the shared beam while mostly canceling the other superfluous grating lobes. This work implements two coprime microphone arrays with different lengths and sub-array spacings. Experimental beam patterns are shown to correspond with simulated results even at frequencies above and below the array’s design frequency. Side lobes in the directional pattern are inversely correlated with bandwidth of analyzed signals.
Shallow-water waveguide invariant parameter estimation and source ranging using narrowband signals
Authors: Harms Andrew , Odom Jonathan , Krolik Jeffrey
Published: October 2014

This paper concerns waveguide invariant parameter estimation using narrowband underwater acoustic signals from multiple sources at known range, or alternatively, the ranges of multiple sources assuming known waveguide invariant parameters. Previously, the waveguide invariant has been applied to estimate the range or bottom properties from intensity striations observed from a single broadband signal. The difficulty in separating striations from multiple broadband sources, however, motivates the use of narrowband components, which generally have higher signal-to-noise ratios and are non-overlapping in frequency. In this paper, intensity fluctuations of narrowband components are shown to be related across frequency by a time-warping (i.e., stretching or contracting) of the intensity profile, assuming constant radial source velocity and the waveguide invariant β. A maximum likelihood estimator for the range with β known or for the invariant parameter β with known source range is derived, as well as Cramer-Rao bounds on estimation accuracy assuming a Gaussian noise model. Simulations demonstrate algorithm performance for constant radial velocity sources in a representative shallow-water ocean waveguide. [Work supported by ONR.]
Multiple pitch estimation using comb filters considering overlap of frequency components
Authors: Tabata Kyohei , Tanaka Ryo , Tanji Hiroki , Murakami Takahiro , Ishida Yoshihisa
Published: October 2014

We propose a method of the multiple pitch estimation using the comb filters for transcript. We can know the pitches of a musical sound by detecting the bigger outputs in comb filters connected in parallel. Each comb filter has peak corresponding to each pitch and its harmonic frequencies. The outputs of the comb filters corresponding to input pitch frequencies have bigger frequency components, and show bigger outputs than other comb filter’s ones. However, when there is the fundamental frequency of higher tone near harmonics of lower tones, the pitch estimation often fails. Therefore, the estimation is assigned to a wrong note when frequency components are shared. The proposed method estimates the correct pitch by correcting the outputs using the matrix, which is defined as the power ratio of the harmonic frequencies to the fundamental frequency. The effectiveness of our proposed method is confirmed by simulations. The proposed method enables more accurate pitch estimation than other conventional methods.
Acoustical materials and sustainability analyses
Authors: Azad Hassan
Published: October 2014

Acoustical materials can perform a variety of functions from absorption and diffusion to the insulation and noise control. They may have similar acoustical performance but very different characteristics in terms of sustainability. It is important to evaluate the environmental effects of materials which exhibit the same acoustical performance in order to wisely choose the best alternative available. This study is intended to introduce and compare the different tools and methods which are commonly used in environmental sustainability analysis of materials including Eco-profile, Eco-indicator, Eco-invent, and also software packages like IMPACT. Also, a specific kind of computer model is proposed in which one can run process of calculation of both acoustics properties and sustainability assessment of a given material through computer aided techniques. The model consists of a simple cubic room with a given set of materials for its elements like walls, floor, ceiling, and windows or doors (if any). The acoustics properties which can be calculated are reverberation time with the help of either Odeon or Catt-Acoustics Software and Air borne/impact sound insulation with the help of recently developed software, SonArchitect. For the sustainability assessment both LCA method and software packages like IMPACT are the main tools.
High intensity therapeutic ultrasound research in the former USSR in the 1950s–1970s
Authors: Khokhlova Vera , Burov Valentin , Gavrilov Leonid
Published: October 2014

A historical overview of therapeutic ultrasound research performed in the former USSR in the 1950s–1970s is presented. In the 1950s, the team of A.K.Burov in Moscow proposed the use of non-thermal, non-cavitational mechanisms of high intensity unfocused ultrasound to induce specific immune responses in treating Brown Pearce tumors in an animal model and melanoma tumors in a number of patients. Later, in the early 1970s, new studies began at the Acoustics Institute in Moscow jointly with several medical institutions. Significant results included first measurements of cavitation thresholds in animal brain tissues in vivo and demonstration of the feasibility to apply high intensity focused ultrasound (HIFU) for local ablation of brain structures through the intact skull. Another direction was ultrasound stimulation of superficial and deep receptors in humans and animals using short HIFU pulses; these studies became the basis for ultrasound stimulation of different neural structures and have found useful clinical applications for diagnostics of skin, neurological, and hearing disorders. Initial studies on the synergism between ultrasound in therapeutic doses combined with consecutive application of ionizing radiation were carried out. Later, hyperthermia research was also performed for brain tissues and for ophthalmology. [Work supported by the grant RSF 14-12-00974.]
Online education: From classrooms to outreach, the internet is changing the way we teach and learn
Authors: Wilson Michael B.
Published: October 2014

The internet is changing the face of education in the world today. More people have access to more information than ever before, and new programs are organizing and providing educational content for free to millions of internet users worldwide. This content ranges from interesting facts and demonstrations that introduce a topic to entire university courses. Some of these programs look familiar and draw from the media and education of the past, building off the groundwork laid by television programs like Watch Mr. Wizard, Bill Nye the Science Guy, and Reading Rainbow, with others more reminiscent of traditional classroom lectures. Some programs, on the other hand, are truly a product of modern internet culture and fan communities. While styles and target audiences vary greatly, the focus is education, clarifying misconceptions, and sparking an interest in learning. Presented will be a survey of current online education, resources, and outreach, as well as the state of acoustics in online education.
Hot topics in fish acoustics (active)
Authors: Stanton Timothy K.
Published: October 2014

It is important to quantify the spatial distribution of fish in their natural environment (ocean, lake, and river) and how the distribution evolves in time for a variety of applications including (1) management of fish stocks to maintain a sustainable source of food and (2) to improve our understanding of the ecosystem (such as how climate change impacts fish) through quantifying predator–prey relationships and other behavior. Active fish acoustics provides an attractive complement to nets given the great distances sound travels in the water and its ability to rapidly survey a large region at high resolution. This method involves studying distributions of fish in the water through analyzing their echoes through various means. While this field has enjoyed development for decades, there remain a number of “hot topics” receiving attention from researchers today. These include: (1) broadband acoustics as an emerging tool for advanced classification of, and discrimination between, species, (2) multi-beam imaging systems used to classify fish schools by size and shape, (3) long-range (km to 10's km) detection of fish, and (4) using transmission loss to classify fish on one-way propagation paths. Recent advances in these and other topics will be presented.
Source parameters for the numerical simulation of lightning as a nonlinear acoustic source
Authors: Marshall Andrew , Evans Neal , Hackert Chris , Oelschlaeger Karl
Published: October 2014

Researchers have proposed using acoustic data to obtain additional insight into aspects of lightning physics. However, it is unclear how much information is retained in the nonlinear acoustic waveform as it propagates and evolves away from the lightning channel. Prior research in tortuous lightning has used simple N-waves as the initial acoustic emission. It is not clear if more complex properties of the lightning channel physics are also transmitted in the far-field acoustic signal, or if simple N-waves are a sufficient source term to predict far-field propagation. To investigate this, the authors have conducted a numerical study of acoustic emissions from a linear lightning channel. Using a hybrid strong-shock/weak-shock code, the authors compare the propagation of a simple N-wave and emissions from a source derived from simulated strong shock waves from the lightning channel. The implications of these results on the measurement of sound from nearby lightning sources will be discussed.
The significance of edge diffraction in sonic boom propagation within urban environments
Authors: Rouse Jerry W.
Published: October 2014

Advances in aircraft design, computational fluid dynamics, and sonic boom propagation modeling suggest that commercial supersonic aircraft can be designed to produce quiet sonic booms. Driven by these advances the decades-long government ban on overland supersonic commercial air transportation may be lifted. The ban would be replaced with a noise-based certification standard, the development of which requires knowledge of community response to quiet sonic booms. For inner city environments the estimation of community exposure to sonic booms is challenging due to the complex topography created by buildings, the large spatial extent and the required frequency range. Such analyses are currently intractable for traditional wave-based numerical methods such as the Boundary Element Method. Numerical methods based upon geometrical acoustics show promise, however edge diffraction is not inherent in geometrical acoustics and may be significant. This presentation shall discuss an initial investigation into the relative importance of edge diffraction in inner city sound fields caused by sonic booms. Results will provide insight on the degree to which edge diffraction effects are necessary for accurate predictions of inner city community exposure.
Comparison of signal coherence for continuous active and pulsed active sonar measurements in littoral waters
Authors: Hines Paul C. , Murphy Stefan M. , Hicks Keaton T.
Published: October 2014

Military sonars must detect, localize, classify, and track submarine threats from distances safely outside their circle of attack. However, conventional pulsed active sonars (PAS) have duty cycles on the order of 1% which means that 99% of the time, the track is out of date. In contrast, continuous active sonars (CAS) have a 100% duty cycle, which enables continuous updates to the track. This should significantly improve tracking performance. However, one would typically want to maintain the same bandwidth for a CAS system as for the PAS system it might replace. This will provide a significant increase in the time-bandwidth product, but may not produce the increase in gain anticipated if there are coherence limitations associated with the acoustic channel. To examine the impact of the acoustic channel on the gain for the two pulse types, an experiment was conducted as part of the Target and Reverberation Experiment (TREX) in May 2013 using a moored active sonar and three passive acoustic targets, moored at ranges from 2 to 6 km away from the sonar. In this paper, preliminary results from the experiment will be presented. [Work supported by the U.S. Office of Naval Research.]
Reverberation and biological clutter in continental shelf waveguides
Authors: Jain Ankita D. , Ignisca Anamaria , Andrews Mark , Gong Zheng , Yi Dong Hoon , Ratilal Purnima , Makris Nicholas C.
Published: October 2014

Seafloor reverberation in continental shelf waveguides is the primary limiting factor in active sensing of biological clutter in the ocean for noise unlimited scenarios. The detection range of clutter is determined by the ratio of the intensity of scattered returns from clutter versus the seafloor in a resolution cell of an active sensing system. We have developed a Rayleigh-Born volume scattering model for seafloor scattering in an ocean waveguide. The model has been tested with data collected from a number of Ocean Acoustic Waveguide Remote Sensing (OAWRS) experiments in distinct US Northeast coast continental shelf environments, and has shown to provide accurate estimates of seafloor reverberation over wide areas for various source frequencies. We estimate scattered returns from fish clutter by combining ocean-acoustic waveguide propagation modeling that has been calibrated in a variety of continental shelf environments for OAWRS applications with a model for fish target strength. Our modeling of seafloor reverberation and scattered returns from fish clutter is able to explain and elucidate OAWRS measurements along the US Northeast coast.
Transmission loss and direction of arrival observations from a source in shallow water
Authors: Dall'Osto David R. , Dahl Peter H.
Published: October 2014

Signals generated by the source used in the reverberation studies of the Targets and Reverberation Experiment (TREX) were recorded by a receiving array located 4.7 km downrange. The bathymetry over this range is relatively flat, with water depth 20 m. The receiving system consists of a 7-channel vertical line array, a 4-channel horizontal line array, oriented perpendicular to the propagation direction, and a 4-channel vector sensor (3-component vector and one pressure), with all channels recorded coherently recorded Transmissions were made once every 30 seconds and over a two hour recording period, changes in the frequency content, amplitude and direction were observed. As both the source and receiving array are at a fixed position in the water column, these observations are assumed to be due to changes in the environment. Interpretation of the data is given in terms of the evolving sea-surface conditions, the presence of nearby scatterers such as fish, and reflection/refraction due to the sloping shoreline.
Release from masking in simulated reverberant environments
Authors: Srinivasan Nirmal Kumar , Gallun Frederick J. , Kampel Sean D. , Jakien Kasey M. , Gordon Samuel , Stansell Megan
Published: October 2014

It is well documented that older listeners have more difficulty in understanding speech in complex listening environments. In two separate experiments, speech intelligibility enhancement due to prior exposure to listening environment and spatial release from masking (SRM) for small spatial separations were measured in simulated reverberant listening environments. Release from masking was measured by comparing threshold target-to-masker ratios (TMR) obtained with a speech target presented directly ahead of the listener and two speech maskers presented from the same location or in symmetrically displaced spatial configurations in an anechoic chamber. The results indicated that older listeners required much higher TMR at threshold and obtained decreased benefit from prior exposure to listening environments compared to younger listeners. For the small separation experiment, speech stimuli were presented over headphones and virtual acoustic techniques were used to simulate very small spatial separations (approx. 2 degrees) between target and maskers. Results reveal, for the first time, the minimum separation required between target and masker to achieve release from speech-on-speech masking in anechoic and reverberant conditions. The advantages of including small separations for understanding the functions relating spatial separation to release from masking will be discussed, as well as the value of including older listeners. [Work supported by NIH R01 DC011828.]
Speech-on-speech masking for children and adults
Authors: Calandruccio Lauren , Leibold Lori J. , Buss Emily
Published: October 2014

Children experience greater difficulty understanding speech in noise compared to adults. This age effect is pronounced when the noise causes both energetic and informational masking, for example, when listening to speech while other people are talking. As children acquire speech and language, they are faced with multi-speech environments all the time, for example, in the classroom. For adults, speech perception tends to be worse when the target and masker are matched in terms of talker sex and language, with mismatches improving performance. It is unknown, however, whether children are able to benefit from these (sex or language) target/masker mismatches. The goal of this project is to further our understanding of the speech-on-speech masking deficit children demonstrate throughout childhood, while specifically investigating whether children’s speech recognition improves when the target and masker are spoken by talkers of the opposite sex, or when the target and masker speech are spoken in different languages. Normal-hearing children and adults were tested on word identification and sentence recognition tasks. Differences in SNR needed to equate performance between the two groups will be reported, as well as data reporting whether children are able to benefit from these target/masker mismatch cues.
Effect of installed diffusers on sound field diffusivity in a real-world classroom
Authors: Sharma Ariana , Bradley David T. , Abdelaziz Mohammed
Published: October 2014

An ideal diffuse sound field is both homogeneous (acoustic quantities are independent of position) and isotropic (acoustic quantities are invariant with respect to direction). Predicting and characterizing sound field diffusivity is essential to acousticians when designing and using acoustically sensitive spaces. Surfaces with a non-planar geometry, referred to as diffusers, can be installed in these spaces as a means of increasing and/or controlling the field diffusivity. Although some theoretical and computational modeling work has been carried out to better understand the relationship between these installed diffusers and the resulting field diffusivity, the current state-of-the-art does not include a systematic understanding of this relationship. Furthermore, very little work has been done to characterize this relationship in full scale and in the real world. In the current project, the effect of diffusers on field diffusivity has been studied in a full scale, real-world classroom. Field diffusivity has been measured for various configurations of the diffusers using two measurement techniques. The first technique uses a three-dimensional grid of receivers to characterize the field homogeneity. To characterize field isotropy, a spherical microphone array has also been used. Results and analysis will be presented and discussed.
Effect of measurement conditions on sound scattered from a pyramid diffuser in a free field
Authors: Riegel Kimberly A. , Bradley David T. , Morgan Mallory , Kowalok Ian
Published: October 2014

A surface with a non-planar geometry, referred to as a diffuser, can be used in acoustically sensitive spaces to help control or eliminate unwanted effects from strong reflections by scattering the reflected sound. The scattering behavior of a diffuser can be measured in a free field, according to the standard ISO 17497-2. Many of the measurement conditions discussed in this standard can have an effect on the measured data; however, these conditions are often not well-specified and/or have not been substantiated. In the current study, a simple pyramid diffuser has been measured while varying several measurement conditions: surface material, orientation of the surface geometry, perimeter shape of the surface, and mounting depth of the surface. Reflected polar response and diffusion coefficient data have been collected and compared for each condition. Data have also been contrasted with those obtained by numerical simulation using boundary element method (BEM) techniques for an idealized pyramid diffuser. Results and analysis will be presented and discussed.
Sound field diffusion by number of peak by continuous wavelet transform
Authors: Cha Yongwon , Imran Muhammad , Jeon Jin Yong
Published: October 2014

The number of peak (Np) in the impulse response signal (IRs) captured for the real hall have been investigated and measured by using continuous wavelet transform (CWT). Np has a relationship with perceptual diffusion as an objective characteristic that is influenced by walls scattering elements. In addition, as measuring diffuse sound fields, the CWT coefficients are used for detecting the diffusive sound. Based on the absolute coefficient values calculated from CWT analysis, a practical method of counting reflections is considered. These reflections are specified as diffusive or specular base on their similarity with the mother wavelet. Temporal and spatial representation of absolute values of CWT is presented. Auditory experiments using a paired comparison method were conducted to gauge the relationship between the Np and perceptual sound field diffusion. It is revealed that a dominant factor influencing the subjective preference in the hall was the Np that varied with different wall surface treatments.
Fin whale vocalization classification and abundance estimation
Authors: Huang Wei , Wang Delin , Makris Nicholas C. , Ratilal Purnima
Published: October 2014

Several thousand fin whale vocalizations from multiple fin individuals were passively recorded by a high-resolution coherent hydrophone array system in the Gulf of Maine in Fall 2006. The recorded fin whale vocalizations have relatively short durations roughly 0.4 s and frequencies ranging from 15 to 40 Hz. Here we classify the fin whale vocalizations and apply the results to estimate the minimum number of vocalizing fin individuals detected by our hydrophone array. The horizontal azimuth or bearing of each fin whale vocalization is first determined by beamforming. Each beamformed fin whale vocalization spectrogram is next characterized by several features such as center frequency, upper and lower frequency limits, as well as amplitude-weighted mean frequency. The vocalizations are then classified using k-mean clustering into several distinct vocal types. The vocalization clustering result is then combined with the bearing-time trajectory information for a consecutive sequence of vocalizations to provide an estimate of the minimum number of vocalizing fin individuals detected.
Neglect of bandwidth of odontocetes echolocation clicks biases propagation loss and single hydrophone population estimates
Authors: Ainslie Michael A. , von Benda-Beckmann Alexander M. , Thomas Len , Tyack Tyack L.
Published: October 2014

Passive acoustic monitoring with a single hydrophone has been suggested as a cost-effective method to monitor population density of echolocating marine mammals, by estimating the distance at which the hydrophone is able to distinguish the echolocation clicks from the background. To avoid a bias in the estimated population density, this method relies on an unbiased estimate of the propagation loss (PL). It is common practice to estimate PL at the center frequency of a broadband echolocation click and to assume this narrowband PL applies also to the broadband click. For a typical situation this narrowband approximation overestimates PL, underestimates the detection range and consequently overestimates the population density by an amount that for fixed center frequency increases with increasing pulse bandwidth and sonar figure of merit. We investigate the detection process for different marine mammal species and assess the magnitude of error on the estimated density due to various simplifying assumptions. Our main purposes are to quantify and, where possible and needed, correct the bias in the population density estimate for selected species and detectors due to use of the narrowband approximation, and to understand the factors affecting the magnitude of this bias to enable extrapolation to other species and detectors.
Histotripsy: An overview
Authors: Cain Charles A.
Published: October 2014

Histotripsy produces non-thermal lesions by generating dense highly confined energetic bubble clouds that mechanically fractionate tissue. This nonlinear thresholding phenomenon has useful consequences. If only the tip of the waveform (P-) exceeds the intrinsic threshold*, small lesions less than the diffraction limit can be generated. This is called microtripsy (other presentations in this session). Moreover, side lobes from distorting aberrations can be “thresholded-out” wherein part of the main lobe exceeds the intrinsic threshold producing a clean bubble cloud (and lesion) conferring significant immunity to aberrations. If a high frequency probe (imaging) waveform intersects a low frequency pump waveform, the compounded waveform can momentarily exceed the intrinsic threshold producing a lesion with an imaging transducer. Multi-beam histotripsy (other presentations in this session) allows flexible placement of both pump and probe transducers. Very broadband P- “monopolar” pulses*, ideal for histotripsy, can be synthesized in a generalization of the multi-beam histotripsy (other presentations in this session) case wherein very short pulses from transducer elements of many different frequencies are added at the focus of what is called a frequency compounding transducer (other presentations in this session). Ultrasound image guidance works well with histotripsy. Bubble clouds are easily seen simplifying both lesion targeting and continuous validation of the ongoing process. Hypoechoic homogenized tissue allows real-time quantification of lesion formation.
Boiling histotripsy: A noninvasive method for mechanical tissue disintegration
Authors: Maxwell Adam D. , Khokhlova Tatiana D. , Schade George R. , Wang Yak-Nam , Kreider Wayne , Yuldashev Petr , Simon Julianna C. , Sapozhnikov Oleg A. , Farr Navid , Partanen Ari , Bailey Michael R. , Hwang Joo Ha , Crum Lawrence A. , Khokhlova Vera A.
Published: October 2014

Boiling histotripsy is an experimental noninvasive focused ultrasound therapy that applies shocked ms-length pulses to achieve mechanical disintegration of a targeted tissue. Localized delivery of high-amplitude shocks causes rapid heating, resulting in boiling of the tissue. The interaction of incident shocks with the boiling bubble results in tissue disruption and liquefaction without significant thermal injury. Simulations are utilized to design and characterize therapy sources, predicting focal waveforms, shock amplitudes, and boiling times. Transducers have been developed to generate focal shock amplitudes >70 MPa and achieve rapid boiling at depth in tissue. Therapy systems including ultrasound-guided single-element sources and clinical MRI-guided phased arrays have been successfully used to create ex vivo and in vivo lesions at ultrasound frequencies in the 1–3 MHz range. Histological and biochemical analyses show mechanical disruption of tissue architecture with minimal thermal effect, similar to cavitation-based histotripsy. Atomization as observed with acoustic fountains has been proposed as an underlying mechanism of tissue disintegration. This promising technology is being explored for several applications in tissue ablation, as well as new areas such as tissue engineering and biomarker detection. [Work supported by NIH 2T32DK007779-11A1, R01EB007643-05, 1K01EB015745, and NSBRI through NASA NCC 9-58.]
Benefits and challenges of employing elevated acoustic output in diagnostic imaging
Authors: Nightingale Kathryn , Church Charles C.
Published: October 2014

The acoustic output levels used in diagnostic ultrasonic imaging in the US have been subject to a de facto limitation by guidelines established by the USFDA in 1976, for which no known bioeffects had been reported. These track-3 guidelines link the Mechanical Index (MI) and the Thermal Index (TI) to the maximum outputs as of May 28, 1976, through a linear derating process. Subsequently, new imaging technologies have been developed that employ unique beam sequences (e.g., harmonic imaging and ARFI imaging) which were not well developed when the current regulatory scheme was put in place, so neither the MI nor the TI takes them into account in an optimal manner. Additionally, there appears to be a large separation between the maxima in the track-3 guidelines and the acoustic output levels for which cavitation-based bioeffects are observed in tissues not known to contain gas bodies. In this presentation, we summarize the history of and the scientific basis for the MI, define an output regime and specify clinical applications under consideration for conditionally increased output (CIO), review the potential risks of CIO in this regime based upon existing scientific evidence, and summarize the evidence for the potential clinical benefits of CIO.
Cavitation characteristics in High Intensity Focused Ultrasound lesions
Authors: ter Haar Gail , Rivens Ian
Published: October 2014

The acoustic emissions recorded during HIFU lesions fall into three broad categories: those associated with non-inertial cavitation, those associated with inertial cavitation, and those linked with tissue water boiling. These three mechanisms can be linked with different lesion shapes, and with characteristic histological appearance. By careful choice of acoustic driving parameters, these effects may be studied individually.