bluuebunny/crossref_metadata_2025 huggingface dataset:
The contributions of David Weston to the acoustics of gas-filled bladders in fishes
Authors: Hastings Mardi C.
Published: October 2013

Thirty-five years ago David Weston published ‘‘Sound Propagation in the Presence of Bladder Fish’’ [in Underwater Acoustics, Vol. 2, edited by V. M. Albers, 1967, pp. 55–88], a seminal contribution that provided the foundation for future research pertaining not only to scattering by fish, but also swimbladder mechanics. In this paper he outlined the theory for the acoustic response of a single swimbladder and then extrapolated to estimate scattering of sound by large schools of fish in the ocean. He addressed the effects of swimbladder geometry, tissue surrounding the swimbladder, and ocean depth on its resonance and scattering characteristics. At that time he pointed out that his work was primarily theoretical because very few experiments had been reported. In the last two decades advances in instrumentation and continued interest in this subject have led to many experiments that have provided data that now confirm much of his original theory. A review of experimental studies inspired by his work and correlation of data with his creative theoretical predictions will be presented.
Fine-scale diel migration dynamics of an island-associated sound-scattering layer
Authors: Benoit-Bird Kelly , Au Whitlow
Published: October 2013

The Hawaiian mesopelagic boundary community, an island-associated, midwater sound-scattering layer, undergoes diel vertical and horizontal migrations. To understand the dynamics of the community’s migration at small temporal scales and large spatial scales, five bottom-mounted, 200-kHz active-acoustic mooring that transmitted ten signals every 15 min, from dusk until dawn for 5 days. Two layers within the boundary community were observed to undergo simultaneous diel vertical and horizontal migration. Vertical migration rates were measured at 0–1.7 m/min, while the horizontal rate averaged 1.67 km/h, swamping the vertical movement. The vertex of the migration pattern was observed 45 min before the midpoint between sunset and sunrise. Until the vertex, animal density increased relatively constantly as the animals migrated towards shore, with the highest animal densities found in the shallowest areas at midnight. Animal abundance estimates at the leading and trailing edge of the layer support the hypothesis that increased animal densities near shore are related to packing, as mesopelagic animals avoid the surface and the bottom. We observed high levels of biomass moving rapidly, over a great distance, into shallow waters very close to shore, providing insight into the significant link the mesopelagic boundary community provides between near-shore and oceanic systems.
Application of acoustic microscopy to assessment of cardiovascular biomechanics
Authors: Saijo Yoshifumi , Sasaki Hidehiko , Nitta Shin-ichi , Tanaka Motonao , Joergensen Claus S. , Falk Erling
Published: October 2013

Acoustic microscopy provides information on physical and mechanical properties of biological tissues, while optical microscopy with various staining techniques provides chemical properties. The biomechanics of tissues is especially important in cardiovascular system because its pathophysiology is closely related with mechanical stresses such as blood pressure or blood flow. A scanning acoustic microscope (SAM) system with tone-burst ultrasound in the frequency range of 100–200 MHz has been developed, and attenuation and sound speed of tissues have been measured. In human coronary arteries, attenuation and sound speed were high in calcification and collagen, while both values were low in smooth muscle and lipid. Another SAM system with 800-MHz–1.3-GHz ultrasound was applied for aortas of Apo-E deficient mouse, which is known to develop atherosclerosis. Attenuation of ultrasound was significantly higher in type 1 collagen compared to type 3 collagen. Recently, a new type FFT-SAM using a single-pulse, broadband frequency range ultrasound (20–150 MHz) has been developed. Cardiac allograft was observed by FFT-SAM and the acoustic properties were able to grade allograft rejection. SAM provides very useful information for assessing cardiovascular biomechanics and for understanding normal and abnormal images of clinical ultrasound.
The acoustics of the echo cornet
Authors: Pyle Robert W. , Klaus Sabine K.
Published: October 2013

The echo cornet was an instrument produced by a number of makers in several countries from about the middle of the nineteenth to the early twentieth centuries. It consists of an ordinary three-valve cornet to which a fourth valve has been added, downstream of the three normal valves. The extra valve diverts the airstream from the normal bell to an ‘‘echo’’ bell that gives a muted tone quality. Although the air column through the echo bell is typically 15 cm longer than the path through the normal bell, there is no appreciable change of playing pitch when the echo bell is in use. Acoustic input impedance and impulse response measurements and consideration of the standing-wave pattern within the echo bell show how this can be so. Acoustically, the echo bell is more closely related to hand-stopping on the French horn than to the mutes commonly used on the trumpet and cornet.
Significance of torsion modes in bowed-string dynamics
Authors: Inacio Octavio , Antunes Jose , Henrique Luis
Published: October 2013

Several aspects of bowed-string dynamics are still inadequately clarified. The importance of torsion modes on the motion regimes is one such issue. Experiments involving torsion are difficult and most of the results available pertain to numerical simulations. The authors’ approach differs from previous efforts in two main aspects: (1) the development of a computational method distinct from the wave-propagation approach pioneered by McIntyre, Schumacher, and Woodhouse and (2) an extensive and systematic analysis of the coupling between torsion and transverse motions is performed. The numerical simulations are based on a modal representation of the unconstrained string and a computational approach for friction that enables accurate representations of the stick-slip forces and of the string dynamics, in both time and space. Many relevant aspects of the bowed-string can be readily implemented, including string inharmonic behavior, finite bow-width, and torsion effects. Concerning the later aspect, a realistic range of the torsional to transverse wave-speed ratio is investigated, for several values of the bow velocity and normal force. Results suggest that torsion modes can effect both transient durations and steady state regimes, in particular when the above-mentioned ratio is <4. Gut strings should then be particularly prone to torsion effects.
The potential application of auditory neuroscience to improving the quality of environmental noise standards
Authors: Luz George A. , Neuhoff John G.
Published: October 2013

In the Public Policy for Noise session at ASA’s last meeting, Fidell stated that U.S. environmental noise regulations are hampered by (1) treating people as if they had a sound level meter in their brain and (2) over-reliance on the Schultz curve. This paper looks at four stages in replacing the SLM in the brain: (1) Pre-1980 when knowledge of psychoacoustics exceeded the capability of instruments (Case study: U.S. Environmental Protection Agency’s 1974 decision to use A-weighting instead of a loudness-based measure). (2) The 1980s when instrumentation could imitate psychoacoustics (Case study: Development of the loudness meter). (3) The 1990s when psychoacoustic research had relatively little influence on American noise standards (Case study: The decision of ANSI S12.9 to reject a Japanese proposal for assessing the annoyance of impulsive sounds [Ogura et al., J. Noise Control Eng. 40, 231–240 (1993)] in favor of a subjective ‘‘impulsive’’ and ‘‘highly impulsive’’ dichotomy). (4) Present opportunities for creative teamwork between equipment developers, standards writers, psychoacousticians, and neuroscientists (Case study: Explaining the U.S. Air Force’s correction to the Sound Exposure Level for the added annoyance of low level, fast moving jet aircraft by ‘‘auditory looming’’).
Effects of meteorology on predicted levels of aircraft noise
Authors: Plotkin Kenneth , Ikelheimer Bruce , Huber Jerome , Clarke John-Paul
Published: October 2013

Calculation of average noise (e.g., Ldn) around airports generally ignores the effects of atmospheric gradients as these effects are assumed to average out over the course of a year. The validity of this assumption was tested through a numerical study using the aircraft noise simulation model NMSIM. Specifically, NMSIM was extended to account for three-dimensional refraction by wind and temperature gradients, plus refraction and scattering into shadow zones, as well as ground impedance effect. Five years of meteorological data at a number of airport locations was obtained, and divided into hourly conditions. A nominal airport, based on a major air carrier airport, was defined. NMSIM was run for hourly operations and weather conditions at each airport location. The resultant Ldn contours were compared to each other by season and location, and also to contours computed for the baseline assumption of no gradients. [Work supported by NASA Langley Research Center.]
Effects of nonlinearity on the propagation of acoustic pulses in random media
Authors: Cleveland Robin , Dallois Laurent , Blanc-Benon Philippe
Published: October 2013

We conducted a numerical investigation into the propagation of finite-amplitude pulses in media with inhomogeneous random sound speed. An N wave (idealized sonic boom) was used as the pulse shape. Initial simulations considered a medium with a single spherical scattering object with a slow sound speed. This object acted as a focusing lens. As the amplitude of the N wave was increased nonlinear effects initially led to enhancement of focusing, reduction in shock risetime, and a shift of the peak away from the object. However, for high amplitude, energy loss at the shock led to a dramatic reduction in the amplitude of the focus and a shift towards the object. Simulations were then carried out in a two-dimensional random media. The sound speed in the random media was constructed using a Fourier mode decomposition with parameters appropriate for turbulence in the atmospheric boundary layer. For low amplitude waves the N wave was focused and defocused by regions of low and high sound speed, respectively. However, the presence of multiple paths means that the wave form no longer resembled an N-wave after propagating about 10 wavelengths. As the amplitude was increased the focusing was enhanced and more localized.
Narrow-band pulse propagation in a one-dimensional stratified random medium
Authors: Frankenthal Shimshon , Beran Mark J.
Published: October 2013

In the stratified random medium considered here, the spatially fluctuating wave speed and refractivity vary only in the range direction, which is normal to the planes of stratification. To treat backscattering in such a medium, it is convenient to split the field into forward- and backward-propagating components, and derive coupled equations that govern the range evolution of the statistical moments of these components. The derivation entails an ensemble-averaging operation, which is here predicated on the key assumption that the two components, which are incident from opposite directions on a differential range slab, are statistically independent of the refractivity fluctuations within that slab. The assumption is justifiable when the fluctuations exhibit a sufficiently rapid time dependence. This procedure is used to derive equations for the bichromatic coherence of the two field components, which are then solved to determine the evolution of the power flux associated with the propagation of a signal due to a planar narrow-band pulse incident on a semi-infinite scattering slab. It is shown that the pulse signal is attenuated exponentially in the range direction, on the so-called ‘‘localization’’ scale, while the scattered power forms echo pulses which are gradually attenuated until all the incident pulse energy is reflected back out of the slab.
A high-order on-surface radiation condition for computing scattering from concave objects and extended surfaces
Authors: Calvo David C.
Published: October 2013

Approximate solutions to scattering problems can be obtained efficiently using on-surface radiation conditions (OSRCs). An OSRC may be viewed as an approximation of the exact nonlocal (integral) Dirichlet-to-Neumann operator, and therefore requires less effort to compute surface quantities and far-field patterns in comparison with other methods. In a previous study [Calvo et al., IEEE Trans. Antennas Propag. (in press)], a higher-order OSRC was developed for two-dimensional convex scatterers that was accurate for large scattering angles relative to the surface normal and moderate surface curvatures. A remarkable result was the exceptional accuracy obtained for end-on incidence with hard scatterers—a challenging case in which creeping waves arise and past OSRCs have had difficulty treating. In this talk, improvements to the OSRC are discussed by relaxing the convexity restriction to allow for compact objects with moderately deep concavity with favorable results. The OSRC is then applied to scattering by extended pressure-release surfaces featuring moderately deep corrugations. Results are favorable in comparison with other more costly numerical techniques. A particular advantage of the high-order OSRC occurs for grazing angles of incidence where the effects of shadowing come into play. Possible applications to ocean acoustics and microwave remote sensing of the sea surface will be addressed.
Analysis of variable-thickness, streamlined transducer array windowing concepts for high speed underwater vehicles
Authors: Koch Robert M.
Published: October 2013

Recent research in very high speed underwater vehicles shows they require a much more streamlined vehicle nose than the present rather flat tactical scale vehicle nose. It has been found that the common forward-facing transducer array with a constant thickness array window utilized on current lower speed vehicles is inadequate. Two newer alternate front-end array concepts suitable for lower drag, higher speed vehicles being investigated are (a) a variable thickness, streamlined array window on a flat forward facing array and (b) a streamlined vehicle nose structure consisting of a built-in distributed, conformal array. While these highly streamlined concepts are attractive from the standpoint of reducing vehicle drag at higher speeds, both require reexamination of the effects of high curvature on front-end sonar array performance. In the present paper, both above streamlined array concepts are numerically examined using the sara2d dynamic structural-acoustic Finite Element Analysis (FEA) code. First, the acoustic performance of a hemispherical array window is compared to a common equal aperture flat window in both transmit (outgoing acoustic wave) and receive (incident acoustic wave) modes. Second, a dynamic simulation of acoustic array beam-forming and beam-steering is performed for a conical shaped conformal array to assess the feasibility of the concept.
Petrov–Galerkin’s method hybrid with finite element into the Helmholtz equation solution. Part I
Authors: Rabadan Malda Itzala , Salazar Cordero Emigdio , Ortega Herrera Jose Angel
Published: October 2013

In this first part, this paper’s purpose is to determine a numerical algorithm according to certain advantages that both Petrov–Galerkins and finite element method offer to resolve the wave equation completely, for simple geometry domains like circular and rectangular membranes, cones and cylinders, and parabolic and spherical volumes. It will permit to contemplate the Helmholtz equations reduced case. Then it can consider real domains like membranes, cones, cylinders, pipes, and parabolic and spherical volumes, polymaterial or discontinuous (with holes will be treated in a second part). This will allow determination of important design parameters for different acoustic devices.
Use of the Spanish adaptation of the phonetic and phonologic Ling tests to evaluate progress in children with cochlear implants and hearing aids
Authors: Corvera Gonzalo , Manrique Maria Cristina , Manrique Juan Pablo , Lapilover Valeria
Published: October 2013

The decision of when to implant a prelingually deafened child is based on his or her progress with hearing aids. It comes down to a subjective decision regarding whether the child could do better with an implant or not, is heavily influenced by the therapists’ experience with cochlear implants, and is difficult to transmit objectively to new teams. The speech discrimination tests usually used tend to use words or phrases in and out of context scenario. Dr. Daniel Ling’s phonetic and phonologic tests (1990) include aspects on auditory abilities, language comprehension, and articulation, and are evaluated in the course of therapy and not in a special evaluatory session. The Spanish adaptation of these tests (adapted by Dr. Ling in collaboration with Santiago Manrique and Cristina de Manrique, 1996) were used for this study, analyzing the results in children with cochlear implants and with hearing aids, to explore their use (or lack of it) as an adjunct for the prescription of a cochlear implant.
Characteristics of small boat acoustic signatures
Authors: Barlett Martin L. , Wilson Gary R.
Published: October 2013

Small boats are often a dominant noise source in harbors, coastal regions, and lakes. However, detailed information about acoustic characteristics is not generally available. To remedy this deficiency, measurements of underwater acoustic signatures from various small boats have been conducted under controlled conditions. Boats used in the measurements were powered by a variety of gasoline and diesel motors in outboard, inboard–outboard, and inboard drive configurations. Measurements were made using a bottom mounted hydrophone in about 100 feet of water. In many instances, the boats were instrumented with a system that recorded the GPS position and engine RPM permitting accurate determinations of platform operating parameters. Measured small boat signatures contain both narrowband and broadband acoustic components. Narrowband components are generally associated with sources from the engine or drive. Narrowband levels in the observed spectra were found to exhibit significant variations and are believed to originate from fluctuations in the load on the engine and drive. Broadband energy was observed to be a dominant noise source at frequencies above several hundred Hertz and is a characteristic feature in all small boat signatures. Examples of small boat signatures will be presented and representative acoustic characteristics of this type of watercraft will be discussed.
Autonomous underwater vehicle adaptive path planning for target classification
Authors: Edwards Joseph R. , Schmidt Henrik
Published: October 2013

Autonomous underwater vehicles (AUVs) are being rapidly developed to carry sensors into the sea in ways that have previously not been possible. The full use of the vehicles, however, is still not near realization due to lack of the true vehicle autonomy that is promised in the label (AUV). AUVs today primarily attempt to follow as closely as possible a preplanned trajectory. The key to increasing the autonomy of the AUV is to provide the vehicle with a means to make decisions based on its sensor receptions. The current work examines the use of active sonar returns from mine-like objects (MLOs) as a basis for sensor-based adaptive path planning, where the path planning objective is to discriminate between real mines and rocks. Once a target is detected in the mine hunting phase, the mine classification phase is initialized with a derivative cost function to emphasize signal differences and enhance classification capability. The AUV moves adaptively to minimize the cost function. The algorithm is verified using at-sea data derived from the joint MIT/SACLANTCEN GOATS experiments and advanced acoustic simulation using SEALAB. The mission oriented operating system (MOOS) real-time simulator is then used to test the onboard implementation of the algorithm.
Concurrent detection and localization of buried targets using track-before-detect processing
Authors: Liu Te-Chih , Schmidt Henrik
Published: October 2013

The GOATS (Generic Oceanographic Array Technology Systems) Joint Research Program explores the development of environmentally adaptive autonomous underwater vehicle (AUV) technology for Rapid Environment Assessment and Mine Counter Measurement (MCM) in coastal environments. MIT is developing the GOATS multistatic sonar concept which uses a low-frequency source on one AUV to subcritically insonify the seabed over a wide area, while a formation of multiple AUVs are used for mapping the associated 3-D scattered acoustic field in the water column. Exploring the different characteristics of the scattering from various buried targets, an algorithm has been developed for autonomous, concurrent detection and localization of buried targets. At the subcritical isonification angles necessary to sustain high coverage rate, the buried target detection depends on the measurement of very weak signals, in general undetectable by traditional detect-before-track algorithms. The method developed here applies a Track-Before-Detect (TBD) approach to solve this problem. This technique tracks the AUV trajectory first using the slowly changing environment information, and then the weak signal detection is declared after the AUV track is estimated at sufficient level of confidence. This new algorithm has been applied on the GOATS-2000 bistatic data. The result shows the successful navigation results by confident detection of three buried targets, two of which are particularly weak scatterers. A real-time, autonomous implementation of the algorithm was recently demonstrated in the GOATS-2002 experiment, and the result for both experiments will be discussed. [Work supported by ONR.]
Source motion effects on matched field processing
Authors: Kim Katherine H. , Hodgkiss William S.
Published: October 2013

Past matched field processing (MFP) analyses have typically overlooked the effects of source motion. However, in real-world applications of MFP, especially those involving the use of large arrays or in the highly dynamic shipping environments common to littoral waters, source motion can exacerbate the conflicting requirements of sufficient samples for adequate data covariance estimation and short-term stationarity assumptions. In the context of MFP, short-term stationarity can be assumed provided that the source does not traverse more than one beamwidth of the matched field processor. Thus, theoretically derived estimates of MFP resolution for a vertical line array are compared to those determined empirically from a shallow water acoustics experiment off the coast of San Diego. Predictions of the eigenvalue spreading that arises from source motion, based upon the work of Baggeroer and Cox [Baggeroer and Cox, Proc. of 1999 Asilomar Conference 1, 103–108 (1999)], are then compared to experimental eigenspectra. Finally, the impact of interferer motion on adaptive MFP processor performance is presented.
Sound from a light aircraft for underwater acoustic inversions
Authors: Giddens Eric M. , Simonet Fernando , Hahn Thomas R. , Buckingham Michael J.
Published: October 2013

Experiments are being conducted in shallow (30 m) water off La Jolla, CA, to investigate the potential usefulness of the sound from a single-engine, propeller-driven, light aircraft for performing underwater acoustic inversions. The sound signature of the aircraft contains harmonics between 50 Hz and 1 kHz, which return the low-frequency geoacoustic properties of the seabed. A microphone approximately 1 m above the surface monitors the sound in air, a seven-element vertical array detects the acoustic arrivals underwater and a single, buried hydrophone receives the signals in the sediment. Aircraft overflights have been made at altitudes between 33 m and 330 m, yielding the altitude-dependence of the peak levels received underwater. Using the vertical array, the reflection coefficient of the seabed is being measured as a function of grazing angle. From the reflection coefficient, the critical angle of the sea floor and hence the sound speed in the sediment are inferred. The sound speed in the sediment should also be available directly from the Doppler shift on the buried hydrophone. These techniques and the available data sets will be discussed in the presentation. [Work supported by ONR.]
Tabu optimization for matched field inversion
Authors: Michalopoulou Zoi-Heleni , Ghosh-Dastidar Urmi
Published: October 2013

Matched field processing is a powerful tool for source localization and geoacoustic inversion. Because of significant environmental and geometry uncertainties, however, matched field processing usually involves multiparameter searches. To facilitate these searches, global optimization techniques such as genetic algorithms and simulated annealing have been successfully employed. In this work, a different approach, tabu, is implemented for optimization in matched field inversion. Tabu is a technique relying on the use of memory; it searches for the global maximum of the objective function through a navigation process that avoids already revisited models, also making use of aspiration criteria and diversification for faster convergence. The tabu performance in localization and geoacoustic inversion is demonstrated through experimentation with both synthetic and real (SWellEX 96) data. The approach is shown to provide reliable estimates in an efficient manner. [Work supported by ONR.]
Determining low-frequency source location from acoustic phase measurements
Authors: Poole Travis L. , Frisk George V.
Published: October 2013

For low-frequency cw sound sources in shallow water, the time rate-of-change of the measured acoustic phase is well approximated by the time rate-of-change of the source-receiver separation distance. An algorithm for determining a locus of possible source locations based on this idea has been developed. The locus has the general form of a hyperbola, which can be used to provide a bearing estimation at long ranges, and an estimate of source location at short ranges. The algorithm uses only acoustic phase data and receiver geometry as input, and can be used even when the source frequency is slightly unstable and/or imprecisely known. The algorithm has been applied to data from low-frequency experiments (20–300 Hz), both for stable and unstable source frequencies, and shown to perform well. [Work supported by ONR and WHOI Academic Programs Office.]
The rediscovery of diffuse reflection in room acoustics prediction
Authors: Dalenbäck Bengt-Inge
Published: October 2013

Around 1986 ‘‘hybrid methods’’ appeared where specular ray tracing was used to speed up image source validation and were implemented in a range of software (sometimes in the form of specular cone tracing). Unfortunately, these methods neglected diffuse reflection and room acoustics prediction suffered. Consequently, most software that started out with such methods have today either changed their algorithms to incorporate diffuse reflection or use them only to predict the early part of the echogram. A possible reason for the popularity of these methods was the more detailed point-receiver echogram, but already in 1980, Kuttruff published an Acustica paper clearly indicating the importance of handling diffuse reflection. Nevertheless, software exist today, and are presented in journals and doctoral theses, that neglect diffuse reflection. One reason could be that diffuse reflection does not always need to be taken into account since when rooms act geometrically mixing or have an even absorption distribution a specular-only prediction may suffice. However, if none of these conditions are met the RT may be severely overestimated while, on the other hand, Sabine/Eyring formulas will severely underestimate the RT. This paper presents examples where neglecting diffuse reflection leads to large prediction errors, especially regarding the RT.
Perceptibility of double-slope reverberation decays
Authors: Knight Derrick P. , Shimizu Yasushi , Torres Rendell R.
Published: October 2013

No concert hall has a perfectly diffuse field, although many are close enough that their decay is perceived as linear. In recent years, concert hall acousticians have taken steps to ensure more exaggerated double-sloped (nonlinear) decays in their concert halls by using coupled volumes. Some acousticians feel that a coupled volume gives a hall a balance between clarity (subjectively speaking) and reverberance. However, there have been no studies done to determine when a nonlinear decay becomes perceptibly different from a linear decay. This work seeks to identify the threshold of perception for nonlinear decays. Nonlinear impulse responses of different lengths are generated by first computing uncoupled impulse responses of a concert hall and a coupled volume in CATT-Acoustic. The two linear impulse responses are convolved in matlab. These convolved impulse responses are manipulated to systematically vary the degree of nonlinear decay. The various nonlinear impulse responses are then convolved with anechoic signals with different temporal characteristics and presented to listeners for evaluation. From these evaluations, a criteria is derived to determine when a nonlinear decay becomes audibly different from a linear decay to a listener for various representative signals.
Scattering and/or diffusing elements in a variety of recently completed music auditoria
Authors: McKay Ronald L.
Published: October 2013

Architectural elements which provide effective acoustic scattering and/or diffusion in a variety of recently completed auditoria for music performance will be presented. Color slides depicting the various elements will be shown. Each will be discussed with respect to its acoustic performance and architectural logic. Measured time-energy reflection patterns will be presented in many cases.
Prospects for a test procedure for rating floor toppings on joist floors
Authors: Warnock Alf
Published: October 2013

Recently ASTM issued a new test method, E2179, for rating the reduction in impact noise when a floor topping is placed on a concrete slab. E2179 is essentially the same as ISO140-8. Measurements have shown that the reduction in impact noise obtained when a floor topping is placed on a concrete slab is not the same as when the topping is placed on a wooden subfloor supported on joists. To complicate matters, the improvement obtained for a given topping changes when the construction of the joist floor on which it is placed changes. Thus a standard test method with a rigorous definition of a reference joist floor might be created but the measured improvements would not necessarily be applicable to joist floors of different construction. The ISO and ASTM single number ratings for some joist floor systems with toppings do not always give good agreement because of the 8 dB rule that exists in ASTM E989 but is absent in ISO 717-2. This paper will review some of the activities in ASTM and ISO and present some measurement resuts obtained in several laboratories.
The acoustical performance of building façades designed for warm and humid climates
Authors: Lobato de Moraes Elcione Maria
Published: October 2013

The effects of noise on man are known to range from simple nuisances to illnesses and trauma. Studies of acoustic isolation provided by buildings in urban centers assume that external openings such as windows and doors remain closed. However, this paper presents results of a study of the acoustic isolation of airborne noise for different types of façade construction in the city of Belén, Brazil. The study recognizes that windows and doors are opened as a function of the local climatic conditions since the city is located in a warm and humid tropical area. The purpose of the investigation is to provide information to planners so that they can better control acoustic contamination of buildings located in these kinds of climates. It is concluded that acoustic isolation is affected by the façade construction and by openings in the façade.
Eighth-nerve regeneration, 20 years later
Authors: Simmons Andrea M. , Chapman Judith A. , Barnstable Alison
Published: October 2013

Over 20 years ago, Harold Zakon and Bob Capranica began a series of studies tracing the anatomical and physiological sequelae of damage to the eighth cranial nerve in ranid frogs. Their results indicated that the severed nerve could regenerate back into the brain, that proper anatomical connectivity was re-established, and that appropriate neural responses in target nuclei re-emerge. In an extension of these studies, patterns of gene expression in the crushed nerve and in target brainstem nuclei are being examined at various time points after damage. These molecular changes are correlated with the time course of recovery of normal vestibular function. Passive (head tilt) and active (response to rotation) vestibular function recover at different rates, with response to rotation still abnormal at 12 weeks after damage. This delayed recovery indicates a process of regeneration, rather than behavioral compensation. Differential display, a PCR-based technique, is used to elucidate which mRNAs are expressed at different time points following nerve crush. At periods less than 1 week after damage, mRNAs, both novel and previously identified, are differentially expressed in crushed versus sham-operated tissue. One gene product, expressed at 24 h post-crush, exhibits 91% coding region homology to human brain-specific protein, CGI-38.
Observations of internal tide variability in the far field of the Hawaiian Ridge: The far field component of the Hawaii Ocean Mixing Experiment (HOME)
Authors: Dushaw Brian , Worcester Peter , Dzieciuch Matthew , Luther Doug
Published: October 2013

As part of the Hawaii Ocean Mixing Experiment (HOME), observations of internal tides in two regions on either side of the Hawaiian Ridge were obtained by tomography, thermistors, and CTD casts from FLIP. The tomographic observations detect radiation of low internal-tide modes in broad areas, while the thermistors and CTD casts measure the ‘‘local’’ internal-tide variability. These observations are used to estimate the amount of energy carried away from the Ridge by the internal tides, to estimate the relative energies of low- and high-mode internal tides, and to test numerical models of internal-tide generation. Barotropic currents and pressure were also measured by tomography, electromagnetic, and pressure sensors so that, with careful modeling, the energy lost from the barotropic tides at the Ridge can be determined. Thermistor data obtained on one mooring showed that the M2, mode-1 internal tide was mainly phase-locked and carried 1.3 kW/m of energy. Modes 2 and 3 had amplitudes comparable to mode-1, but they were not phase locked. Energy fluxes at three other moorings were 1.2, 2.0, and 6.7 kW/m. Energy fluxes obtained by tomography were 0 (1 kW/m) or less; the line-integral data are less susceptible to the interference effects in the outgoing internal waves.
Propagation of sound through a spicy ocean: A numerical experiment
Authors: Dzieciuch Matthew , Munk Walter , Rudnick Daniel
Published: October 2013

Using a closely sampled 1000 km hydrographic section in the eastern North Pacific, we separate the sound-speed finestructure into 2 component fields: (i) isopycnal tilt dominated by internal waves; and (ii) ‘‘spicy’’ (hot and salty) millifronts associated with upper ocean stirring. Scattering by the spicy millifronts is of the same order as internal wave scattering (the traditional view), and they both contribute to the penetration of sound into the shadow zone.
Long range nonlinear propagation in an ocean acoustic waveguide
Authors: Castor Kaelig , Gerstoft Peter , Roux Philippe , Kuperman W. A. , McDonald B. E.
Published: October 2013

The Nonlinear Progressive Wave Equation (NPE) [McDonald and Kuperman, J. Acoust. Soc. Am. 81, 1406–1417 (1987)] is an approximation of the Euler equations for nonlinear compressional waves in an inviscid fluid and, actually, is the nonlinear time domain counterpart of the frequency domain linear parabolic wave equation (PE) for small angle propagation. Simulations using a npe code were used to study both harmonic (high frequency) and parametric (low frequency) generation. This code was coupled with a linear adiabatic normal mode program which allows range-dependent cases treatment to study propagation in shallow or deep water with longer range propagation paths. Included in the modeling are both shock dissipation and linear attenuation in the sediment layer. The results of these studies are presented.
NPAL horizontal refraction: RAKE correlator estimates
Authors: Dzieciuch Matthew
Published: October 2013

A purpose of the NPAL billboard array data set was to measure the horizontal refraction of low-frequency (75 Hz), long-range (4000 km) timefronts. Simple beamforming yields time series that are too noisy for an accurate estimate of horizontal refraction variability. Since the data show partial horizontal coherence, a RAKE correlator is designed to account for the signal variance across the array and to improve the performance of the linear beamformer. a)J. A. Colosi, B. D. Cornuelle, B. D. Dushaw, M. A. Dzieciuch, B. M. Howe, J. A. Mercer, R. C. Spindel, and P. F. Worcester.
Vibration balanced miniature loudspeaker
Authors: Schafer David E. , Jiles Mekell , Miller Thomas E. , Thompson Stephen C.
Published: October 2013

The vibration that is generated by the receiver (loudspeaker) in a hearing aid can be a cause of feedback oscillation. Oscillation can occur if the microphone senses the receiver vibration at sufficient amplitude and appropriate phase. Feedback oscillation from this and other causes is a major problem for those who manufacture, prescribe, and use hearing aids. The receivers normally used in hearing aids are of the balanced armature-type that has a significant moving mass. The reaction force from this moving mass is the source of the vibration. A modification of the balanced armature transducer has been developed that balances the vibration of its internal parts in a way that significantly reduces the vibration force transmitted outside of the receiver case. This transducer design concept, and some of its early prototype test data will be shown. The data indicate that it should be possible to manufacture transducers that generate less vibration than equivalent present models by 15–30 dB.
PC interface for a stepped filter octave band analyzer
Authors: Horta Miguel A. , Vazquez Marco A.
Published: October 2013

Spectrum analyzers are a basic tool for an acoustic engineer. Since almost anyone in a classroom has access to a PC or notebook computer, a low cost alternative for measuring many different parameters with a spectrum analyzer (such as reverberation time, transmission loss, or equivalent noise level) is a digital interface that processes the signal combined with the proper software for the computer. This is a design of a spectrum analyzer that does such a task. The external interface sequentially processes the signal in an octave band filter bank and converts it to data for the computer to display. Depending on the software, the data can be used to measure any of the signal’s desired parameters.
Broadband self-calibrating micromachined microphones with integrated optical displacement detection
Authors: Hall Neal A. , Lee Wook , Degertekin F. Levent
Published: October 2013

An optical displacement detection method for micromachined microphones is described and experimental results are presented. The microphone membrane is fabricated on a transparent substrate and the back electrode is patterned in the form of diffraction fingers. This structure forms a phase sensitive diffraction grating, providing the displacement sensitivity of an optical interferometer. The diffraction fingers are also used for electrostatic actuation, providing sensitivity adjustment and self-calibration capabilities. Optically semitransparent coatings are also employed to create Fabry–Perot resonant cavities that enhance the optical detection sensitivity by an order of 10 dB. The high electrical sensitivity provided by optical displacement detection relaxes requirements on mechanical sensitivity, and small microphone membranes on the order of 200 μm with vacuum-sealed and air-sealed cavities are used to fabricate microphones with a flat response from dc to over 200 kHz. The optical detection and electrostatic actuation capabilities are demonstrated on fully integrated devices with aluminum microphone membranes micromachined on quartz substrates and bonded to microfabricated silicon photodiodes. [Work supported by DARPA.]
Low-power, cylindrical, air-coupled acoustic levitation/concentration devices: Symmetry breaking of the levitation volume
Authors: Kaduchak Gregory , Kogan Aleksandr S. , Kwiatkowski Christopher S. , Sinha Dipen N.
Published: October 2013

A cylindrical acoustic device for levitation and/or concentration of aerosols and small liquid/solid samples (up to several millimeters in diameter) in air has been developed [Kaduchak et al., Rev. Sci. Instrum. 73, 1332–1336]. It is inexpensive, low-power, and, in its simplest embodiment, does not require accurate alignment of a resonant cavity. It is constructed from a cylindrical PZT tube with thickness-to-radius ratio h/a∼0.03. The novelty of the device is that the lowest-order breathing mode of the tube is tuned to match a resonant mode of the interior air-filled cylindrical cavity. A high-Q cavity results that is driven very efficiently; drops of water in excess of 1-mm diameter are levitated for approximately 100 mW of input electrical power. The present research addresses modifying the different spatial configurations of the standing wave field within the cavity. By breaking the cylindrical symmetry, it is shown that pressure nodes can be localized for collection or separation of aerosolds or other particulate matter. Several different symmetry-breaking configurations are demonstrated. It is shown that experimental observations of the nodal arrangements agree with theoretical predictions.
Low frequency cavitation erosion
Authors: Pardue Sally J. , Chandekar Gautam
Published: October 2013

Damage of diesel engine piston sleeve liners due to cavitation of the coolant fluid can be severe. Coolant fluid additives are used to inhibit cavitation damage, and are evaluated by industry suppliers using ASTM G32-98 Standard Test Method for Cavitation Erosion Using Vibratory Apparatus. The ASTM G32-98 test procedure uses an ultrasonic horn at 20 kHz to vibrate a test button in the coolant. The test button mass loss and surface appearance are studied to sort the performance of new coolant additives. Mismatch between good lab performers and actual engine test runs has raised concerns over the current lab test. The frequency range of the current test has been targeted for investigation. A low frequency, less than 2000 Hz, test rig was built to explore the cavitation damage. The test system did produce cavitation on the surface of the test button for a period of 36 h, with minimal mass loss. The test rig experienced cyclic fatigue when test times were extended. The work is now focusing on designing a better test rig for long duration tests and on developing numerical models in order to explore the effects of cavitation excitation frequency on surface erosion.
Distinguishing sound from noise—The significance of attention and noise sensitivity
Authors: Dodd George
Published: October 2013

There is often a large discrepancy between the accuracies of physical measurements and the precision ascribed to subjective responses to sound. Consequently the criteria by which sound and noise are assessed can appear somewhat loose. In previous work it was proposed that there is a need to formalize definitions for noise and non-noise sounds in order to render subjective reactions more readily quantifiable. This is necessary to give greater recognition to the significance of differences in individuals responses, and also to put criteria for environmental sound on a more scientific basis. This presentation reviews our research looking for physiological responses which correlate with a person’s attention to sound, and presents results from our study of noise sensitivity. In this work noise sensitivity is defined as being a tendency to be distracted by sound and is viewed as a stable characteristic of people differing between individuals and distinct from noise annoyance experienced at a particular time. The results of assessing noise sensitivity by self-assessment questionaires and other measures are presented and how they relate to individual listening habits.
Sound localization: Effects of gender, aging, head related transfer function, and auditory performance
Authors: Menezes Pedro , Soares Ilka , Caldas Neto Silvio , Motta Mauricy
Published: October 2013

The sound localization resolution in 80 normal hearing subjects of both sexes will be compared to audiometric parameters, audiometry, timpanometry, and stapedian reflexes. Moreover, the pinna and concha length and width so as the interaural distance, ear–head angle, sex, and age were compared too, in a reverberating room. Three tones of square waves with 1, 2, and 3 kHz, were present with an intensity of 70-dB SPL in order of the speakers and sequence of frequencies randomized. The subjects were trained to indicate the origin of the sound in a control console with push-buttons representing the space disposition of the speakers, being 8 in the horizontal plane, 5 in the medial sagital plane, and 5 in the medial frontal plane. The identification of each speaker is done by pressing the respective push-button. The angle between the speaker’s axis in the same plane is of 45, and the distance of 1 meter from the analyzed subject. The preliminary results from 50 subjects showed a better localization precision at 1 kHz frequency, without sex or age predominance. The medial sagital plane presented more errors, in all the frequencies, according to the specialized literature. More subjects are actually being and soon they will be available. (To be presented in Portuguese.)
Active control of noise radiated through rectangular plates using piezeletric patches
Authors: Santana Danuza Cristina , Duarte Marcus Antonio Viana , Rade Domingos Alves
Published: October 2013

Due to problems caused by noise in industrial environment and in human daily life, techniques of noise control have received increasing attention from engineers and researchers lately. More recently, the use of piezeletric elements as sensors and/or actuators in noise and vibration control systems has been extensively investigated. The main advantage of the use of such devices is that they can be easily integrated to the mechanical system with little added mass and relatively high control authority. The present paper addresses a technique of active control of sound transmitted through a rectangular, thin, simply supported plate by employing multiple piezeletric patches bonded to the plate’s surface. A harmonic plane wave incident on one side of the plate is considered to be the primary noise source. Aiming at minimizing the noise transmitted to the other side of the plate, bending motion is induced through the piezeletric patches so that the plate behaves as a secondary sound source. The paper brings the development of the system mathematical model which enables to obtain the spatial distribution of sound pressure radiated through the plate in the far field. An optimal control technique providing the voltage control signals for the activation of the piezoelectric patches is presented, based on the minimization of a cost function representing the mean square integral of the sound pressure radiated in a semi-sphere in far field. It is also proposed a methodology for the optimal placement on the piezelectric patches using Genetic Algorithms. (To be presented in Portuguese.)