bluuebunny/crossref_metadata_2025 huggingface dataset:
Study and Analysis of Anti Vibratory Passive and Active Methods Applied to Complex Mechanical System
Authors: Lopez Cédric , Malburet François , Barraco André
Published: January 2012

This paper studies problematic of a mechanical system composed of different coupled parts submitted to a high speed shock and proposes analysis of anti vibratory passive and active methods based on an experimental and theoretical coupled approach. After a shock, different parts of the system oscillate. If one of them is excited at a particular frequency, such as its proper frequency, important oscillations appear and can lead to the deterioration of the system by introducing important stresses. In this paper, we propose an analysis in order to understand this kind of problem and what we can do to avoid it. Firstly, we discuss problematic and we expose the studied system. In a second time, we develop two approaches of modeling that allow us to understand the phenomenon by carrying out numerical simulations. Then cross checking of model is completed via experimental study on drop test bench. Passive minimization method of vibrations based on experimental and theoretical coupled approach is exposed. Finally, a comparative analysis of different methods of control and experimental results of controlled system are presented.
The tones of the kalimba (African thumb piano)
Authors: Chapman David M. F.
Published: January 2012

The acoustic spectrum of the kalimba (African thumb piano) is measured and analyzed for tonal structure. The frequency f1 of the fundamental tone of each tine (key) is investigated in relation to the frequencies of its two dominant overtones, f2 and f3. These frequencies are identified as the first three modes of transverse vibration of a beam of rectangular cross section. As is typical for vibrating-beam instruments, the overtone sequence is inharmonic, that is, the sequence f1, f2, f3,… is unevenly spaced and the frequency ratios f2/f1 and f3/f1 are not integers. The kalimba tines are modeled by applying the Euler–Bernoulli beam equation with one end clamped, the other end free, and an intermediate point (the bridge) simply supported. Unlike the cases of free-free and clamped-free beams, it is found that the clamped-supported-free frequency ratios f2/f1 and f3/f1 are not fixed values, but depend uniquely upon where the bridge supports and subdivides the tine. The model solution is more thoroughly investigated analytically for the special case in which the beam segment ratio is unity, which has some analytic solutions. Numerically computed mode frequencies agree well with acoustic measurements, validating the model. Mode shapes are computed for the first three modes of a typical tine.
Feedback control of acoustic musical instruments: Collocated control using physical analogs
Authors: Berdahl Edgar , Smith Julius O. , Niemeyer Günter
Published: January 2012

Traditionally, the average professional musician has owned numerous acoustic musical instruments, many of them having distinctive acoustic qualities. However, a modern musician could prefer to have a single musical instrument whose acoustics are programmable by feedback control, where acoustic variables are estimated from sensor measurements in real time and then fed back in order to influence the controlled variables. In this paper, theory is presented that describes stable feedback control of an acoustic musical instrument. The presentation should be accessible to members of the musical acoustics community who may have limited or no experience with feedback control. First, the only control strategy guaranteed to be stable subject to any musical instrument mobility is described: the sensors and actuators must be collocated, and the controller must emulate a physical analog system. Next, the most fundamental feedback controllers and the corresponding physical analog systems are presented. The effects that these controllers have on acoustic musical instruments are described. Finally, practical design challenges are discussed. A proof explains why changing the resonance frequency of a musical resonance requires much more control power than changing the decay time of the resonance.
Perceptually informed synthesis of bandlimited classical waveforms using integrated polynomial interpolation
Authors: Välimäki Vesa , Pekonen Jussi , Nam Juhan
Published: January 2012

Digital subtractive synthesis is a popular music synthesis method, which requires oscillators that are aliasing-free in a perceptual sense. It is a research challenge to find computationally efficient waveform generation algorithms that produce similar-sounding signals to analog music synthesizers but which are free from audible aliasing. A technique for approximately bandlimited waveform generation is considered that is based on a polynomial correction function, which is defined as the difference of a non-bandlimited step function and a polynomial approximation of the ideal bandlimited step function. It is shown that the ideal bandlimited step function is equivalent to the sine integral, and that integrated polynomial interpolation methods can successfully approximate it. Integrated Lagrange interpolation and B-spline basis functions are considered for polynomial approximation. The polynomial correction function can be added onto samples around each discontinuity in a non-bandlimited waveform to suppress aliasing. Comparison against previously known methods shows that the proposed technique yields the best tradeoff between computational cost and sound quality. The superior method amongst those considered in this study is the integrated third-order B-spline correction function, which offers perceptually aliasing-free sawtooth emulation up to the fundamental frequency of 7.8 kHz at the sample rate of 44.1 kHz.
Musical acoustics of orchestral water crotales
Authors: Worland Randy
Published: January 2012

An experimental investigation of orchestral crotale vibrational modes in water is presented, along with a qualitative virtual mass model describing the observed effects. Changes in frequency, overtone ratio, and mode splitting as a function of water depth are reported for a C6 crotale using electronic speckle-pattern interferometry. These data are related to perceived changes in pitch and timbre, along with the creation of audible beats at particular water depths. It is also shown that the suspension method used by musicians when dipping crotales into water leads to the creation of additional acoustically significant modes that are not excited when the crotales are mounted in the standard manner.
Estimation of harpsichord inharmonicity and temperament from musical recordings
Authors: Dixon Simon , Mauch Matthias , Tidhar Dan
Published: January 2012

The inharmonicity of vibrating strings can easily be estimated from recordings of isolated tones. Likewise, the tuning system (temperament) of a keyboard instrument can be ascertained from isolated tones by estimating the fundamental frequencies corresponding to each key of the instrument. This paper addresses a more difficult problem: the automatic estimation of the inharmonicity and temperament of a harpsichord given only a recording of an unknown musical work. An initial conservative transcription is used to generate a list of note candidates, and high-precision frequency estimation techniques and robust statistics are employed to estimate the inharmonicity and fundamental frequency of each note. These estimates are then matched to a set of known keyboard temperaments, allowing for variation in the tuning reference frequency, in order to obtain the temperament used in the recording. Results indicate that it is possible to obtain inharmonicity estimates and to classify keyboard temperament automatically from audio recordings of standard musical works, to the extent of accurately (96%) distinguishing between six different temperaments commonly used in harpsichord recordings. Although there is an interaction between inharmonicity and temperament, this is shown to be minor relative to the tuning accuracy.
Do trumpet players tune resonances of the vocal tract?
Authors: Chen Jer-Ming , Smith John , Wolfe Joe
Published: January 2012

The acoustic impedance spectrum was measured in the mouths of seven trumpeters while they played normal notes and while they practiced “bending” the pitch below or above the normal value. The peaks in vocal tract impedance usually had magnitudes rather smaller than those of the bore of the trumpet. Over the range measured, none of the trumpeters showed systematic tuning of the resonances of the vocal tract. However, all players commented that the presence of the impedance head in the mouth prevented them from playing the very highest notes of which they were normally capable. It is therefore possible that these players might use either resonance tuning or perhaps very high impedance magnitudes for some notes beyond the measured range. The observed lack of tuning contrasts with measurements for the saxophone which, like the trumpet, has weak resonances in the third and fourth octaves. Saxophonists are only able to play the highest range by tuning resonances of the vocal tract, so that the series impedance has a very strong peak at a frequency near that of the desired note. This difference is explained by the greater control that the trumpet player has over the natural frequency of the vibrating valve.
Bowed-string multiphonics analyzed by use of impulse response and the Poisson summation formula
Authors: Guettler Knut , Thelin Håkon
Published: January 2012

By carefully positioning the bow and a lightly touching finger on the string, the string spectrum can be conditioned to provide narrow bands of pronounced energy. This leaves the impression of multiple complex tones with the normal (Helmholtz) fundamental as the lowest pitch. The phenomenon is seen to be caused by two additional signal loops, one on each side of the finger, which through the repeating slip pattern get phase locked to the full loop of the fundamental. Within the nominal period, however, the slip pulses will not be uniform like they are during the production of a normal “harmonic” or “flageolet” but may vary considerably in shape, size, and timing. For each string, there is a large number of bow/finger combinations that bear the potential of producing such tones. There are also two classes, depending on whether the bow or the finger is situated closest to the bridge. Touching the string with the finger closest to the bridge will somewhat emphasize the (Helmholtz) fundamental. The technique is applicable to double bass and cello, while less practical on shorter-stringed instruments. Analyses based on impulse responses and the Poisson summation formula provide an explanation to the underlying system properties.
Double basses on the stage floor: Tuning fork–tabletop effect, or not?
Authors: Guettler Knut , Askenfelt Anders , Buen Anders
Published: January 2012

The question whether or not double basses can benefit from a compliant and radiating stage floor in the low end of their tonal register, similar to the well-known tuning fork–tabletop effect, was examined through field experiments in five concert halls. The topic comprises several aspects: (1) How well the mechanical impedances of double basses and the stage floor match, (2) amount of vibration velocity transmitted to the floor through the end pin of the bass, and (3) radiation efficiency of point-excited bending waves in the stage floor far below the coincidence frequency. Each aspect represents a prerequisite for the tuning fork–tabletop effect to take place. The input impedance at the end pin was measured for three representative double basses. The stage floors of five orchestra halls were measured with respect input impedance and damping, while sound radiation to the audience area was measured for two of them. In Lindeman Hall, Oslo, all conditions for the tuning fork–tabletop effect to take place were clearly met. The contribution from the stage-floor radiation to the sound pressure level in the audience area was found to be about 5 dB between 40 and 60 Hz, and even higher between 30 and 40 Hz.
Vibro-acoustics of organ pipes—Revisiting the Miller experiment (L)
Authors: Gautier F. , Nief G. , Gilbert J. , Dalmont J. P.
Published: January 2012

A century ago, Science published a spectacular experimental study on the physics of organ pipes. Dayton C. Miller observed experimentally that the sound produced by an organ pipe can depend on the vibration of its walls, in addition to its internal geometry and the interaction between the air jet and the labium. The Miller experiment has been repeated and an interpretation is now proposed in terms of vibroacoustic coupling mechanisms between walls and internal fluid, which can lead to “pathological” behavior.
On the accuracy of bore reconstruction from input impedance measurements: Application to bassoon crook measurements
Authors: Dalmont Jean-Pierre , Curtit Marthe , Yahaya Ahmad Fazli
Published: January 2012

The determination of a pipe bore from the measured reflection function is a technique that has reached a certain maturity. However, the measurement of the reflection function in the time domain (pulse reflectometry) requires equipment that is rather difficult to operate. On the other hand, the techniques for measuring the input impedance have reached an unquestionable maturity with respect to measurement setup and to calibration. It is thus likely that impedance measurements might be able to give the same information. By doing simulations, it is first shown that the reflection function deduced from the input impedance gives access to the bore with a precision comparable with that obtained with pulse reflectometry. It is then shown that the accuracy obtained with measurements is of the same order as that obtained from simulations. The technique is then used for the dimensional inspection of bassoon crooks.
Source implementation to eliminate low-frequency artifacts in finite difference time domain room acoustic simulation
Authors: Jeong Hyok , Lam Yiu Wai
Published: January 2012

The finite difference time domain (FDTD) method is a numerical technique that is straight forward to implement for the simulation of acoustic propagation. For room acoustics applications, the implementation of efficient source excitation and frequency dependent boundary conditions on arbitrary geometry can be seen as two of the most significant problems. This paper deals with the source implementation problem. Among existing source implementation methods, the hard source implementation is the simplest and computationally most efficient. Unfortunately, it generates a large low-frequency modulation in the measured time response. This paper presents a detailed investigation into these side effects. Surprisingly, some of these side effects are found to exist even if a transparent source implementation is used. By combing a time limited approach with a class of more natural source pulse function, this paper develops a source implementation method in FDTD that is as simple and computationally as efficient as a hard source implementation and yet capable of producing results that are virtually the same as a true transparent source. It is believed that the source implementation method developed in this paper will provide an improvement to the practical usability of the FDTD method for room acoustic simulation.
Mode locking effects on the playing frequency for fork fingerings on the clarinet
Authors: Nederveen C. J. , Dalmont J.-P.
Published: January 2012

The non-linear excitation of wind instruments generates higher harmonics of the playing frequency. These higher harmonics are coupled to resonances in the pipe. This is called mode locking. When the pipe modes are not harmonic, the playing frequency shifts away from the fundamental in order to maximize the output. It may go up or down, depending on the position of the modes and the amplitude. The effect is especially manifest for fork fingerings. Three fork fingerings on a clarinet were investigated. They were artificially blown between the threshold and extinction pressure. A time domain simulation was carried out based on a lumped model of the excitation coupled to an input impedance calculated from the instrument dimensions. At low amplitudes the fundamental frequency dominates and the playing frequency is governed by the position of the first peak in the input impedance spectra. At higher blowing pressures the playing frequency shifts. For both blowing and simulation this follows the same pattern. The frequencies predicted by the calculations are higher than the values found by blowing, which may be due to inadequacies in the model description, to uncertainties of the various parameters, as reed stiffness, moving reed area, and the properties of the slit flow.
Superspheroidal modeling of resonance scattering from elongated air bubbles and fish swim bladders
Authors: Feuillade C.
Published: January 2012

The extended boundary condition technique of Waterman [J. Acoust. Soc. Am. 45, 1417–1429 (1969)] has been used to make accurate studies of the frequency and azimuthal scattering distributions from extended axisymmetric acoustic objects. These objects are formed using the mathematical function for a “superellipse” [i.e., (x/a)s + (z/b)s = 1, where s = 2n, n = 1,2,…], and revolving around the z-axis. For s = 2, the object is a spheroid with aspect ratio α = b/a. As s increases, the shape of the object approaches a right circular cylinder of diameter 2a and length 2b. The method is applied to the case of prolate (i.e., α > 1) air-filled objects in water, which has importance for the interpretation of acoustic scattering from oceanic objects such as air-bubbles, the swim bladders of some fish, and zooplankton. It is found that the resonance frequency increases with α, essentially as predicted using a different method by Weston, and increases in a relatively minor way with s. The resonance peak amplitude, and Q, are also more sensitive to changes in α, than s. The method shows that the monopole resonance continues to dominate low frequency scattering, leading to an almost spherically symmetric azimuthal scattering distribution, even for elongated, cylindrical, air-filled, objects with an aspect ratio up to α = 20, and s = 32.
Modeling of thermal effects in antivascular ultrasound therapy
Authors: Levenback Benjamin J. , Sehgal Chandra M. , Wood Andrew K. W.
Published: January 2012

Antivascular ultrasound consisting of low-intensity sonication in the presence of circulating microbubbles of an ultrasound contrast agent has been demonstrated to disrupt blood flow in solid cancers. In this study a mathematical framework is described for the microbubble-induced heating that occurs during antivascular ultrasound. Biological tissues are modeled as a continuum of microbubble-filled vasculature, cells, and interstitial fluids with compressibility equal to the sum of the compressibility of each component. The mathematical simulations show that the absorption of ultrasound waves by viscous damping of the microbubble oscillations induced significant local heating of the tissue vasculature. The extent and the rate of temperature increase not only depends on the properties of the microbubbles and the sonication parameters but is also influenced markedly by the blood flow. Slow flow conditions lead to higher tissue temperatures due to a stronger interaction between microbubbles and ultrasound and reduced heat dissipation. Because tumors have slower blood flow than healthy tissue, the microbubble-induced ultrasound antivascular therapy is likely to affect cancerous tissue more extensively than healthy tissue, providing a way to selectively target the vasculature of cancers.
Three-dimensional analysis of scattering by pressure-release plane surfaces and the validity of the image solution
Authors: Welton P. J.
Published: January 2012

Because of the complexity of the scattering integrals in three dimensions, numerous approximations are used to obtain closed-form solutions. By considering the scattering by an infinite, pressure-release plane surface, the effects of various phase approximations and source directivity approximations can be examined independently of the surface roughness. Calculations are carried out using the Fraunhofer and Fresnel phase approximations, and two directivity approximations. It has been shown experimentally that the image solution is valid for the reflection of an acoustic beam by an infinite, pressure-release plane surface if the plane is in the farfield of the source. Consequently, the image solution is used to compare analytical solutions obtained using various phase and directivity approximations, and it is found that both the Fresnel phase approximation and a realistic directivity approximation are required to achieve a good fit. The solution produced by the Fraunhofer phase approximation is obtained as an asymptotic limit of the modified Fresnel solution. Criteria for the validity of the Fraunhofer and Fresnel phase approximations are developed. The Fresnel phase approximation is valid under fairly broad conditions, but the Fraunhofer phase approximation is never valid for an infinite plane surface that must be in the farfield of the source.
Direct formulation of the supersonic acoustic intensity in space domain
Authors: Fernandez-Grande Efren , Jacobsen Finn , Leclère Quentin
Published: January 2012

This paper proposes and examines a direct formulation in space domain of the so-called supersonic acoustic intensity. This quantity differs from the usual (active) intensity by excluding the circulating energy in the near-field of the source, providing a map of the acoustic energy that is radiated into the far field. To date, its calculation has been formulated in the wave number domain, filtering out the evanescent waves outside the radiation circle and reconstructing the acoustic field with only the propagating waves. In this study, the supersonic intensity is calculated directly in space domain by means of a two-dimensional convolution between the acoustic field and a spatial filter mask that corresponds to the space domain representation of the radiation circle. Therefore, the acoustic field that propagates effectively to the far field is calculated via direct filtering in space domain. This paper presents the theory, as well as a numerical example to illustrate some fundamental principles. An experimental study on planar radiators was conducted to verify the validity of the technique. The experimental results are presented, and serve to illustrate the usefulness of the analysis, its strengths and limitations.
Comparing perceived auditory width to the visual image of a performing ensemble in contrasting bi-modal environments
Authors: Valente Daniel L. , Braasch Jonas , Myrbeck Shane A.
Published: January 2012

Despite many studies investigating auditory spatial impressions in rooms, few have addressed the impact of simultaneous visual cues on localization and the perception of spaciousness. The current research presents an immersive audiovisual environment in which participants were instructed to make auditory width judgments in dynamic bi-modal settings. The results of these psychophysical tests suggest the importance of congruent audio visual presentation to the ecological interpretation of an auditory scene. Supporting data were accumulated in five rooms of ascending volumes and varying reverberation times. Participants were given an audiovisual matching test in which they were instructed to pan the auditory width of a performing ensemble to a varying set of audio and visual cues in rooms. Results show that both auditory and visual factors affect the collected responses and that the two sensory modalities coincide in distinct interactions. The greatest differences between the panned audio stimuli given a fixed visual width were found in the physical space with the largest volume and the greatest source distance. These results suggest, in this specific instance, a predominance of auditory cues in the spatial analysis of the bi-modal scene.
From echolocation clicks to animal density—Acoustic sampling of harbor porpoises with static dataloggers
Authors: Kyhn Line A. , Tougaard Jakob , Thomas Len , Duve Linda Rosager , Stenback Joanna , Amundin Mats , Desportes Geneviève , Teilmann Jonas
Published: January 2012

Monitoring abundance and population trends of small odontocetes is notoriously difficult and labor intensive. There is a need to develop alternative methods to the traditional visual line transect surveys, especially for low density areas. Here, the prospect of obtaining robust density estimates for porpoises by passive acoustic monitoring (PAM) is demonstrated by combining rigorous application of methods adapted from distance sampling to PAM. Acoustic dataloggers (T-PODs) were deployed in an area where harbor porpoises concurrently were tracked visually. Probability of detection was estimated in a mark–recapture approach, where a visual sighting constituted a “mark” and a simultaneous acoustic detection a “recapture.” As a distance could be assigned to each visual observation, a detection function was estimated. Effective detection radius of T-PODs ranged from 22 to 104 m depending on T-POD type, T-POD sensitivity, train classification settings, and snapshot duration. The T-POD density estimates corresponded to the visual densities derived concurrently for the same period. With more dataloggers, located according to a systematic design, density estimates would be obtainable for a larger area. This provides a method suitable for monitoring in areas with densities too low for visual surveys to be practically feasible, e.g., the endangered harbor porpoise population in the Baltic.
Lateralization based on interaural differences in the second-order amplitude modulator
Authors: Dietz Mathias , Ewert Stephan D. , Hohmann Volker
Published: January 2012

Second-order amplitude modulation is a relatively slow variation of the modulation depth of a first-order amplitude modulation with higher frequency. In contrast to first-order modulation, which appears as a physical component in the stimulus spectrum after half-wave rectification, second-order modulation is not necessarily demodulated by the auditory periphery. For binaural processing of second-order amplitude modulated stimuli it is unknown whether interaural time differences (ITDs) in the second-order modulation result in a lateralized percept. Thus, second-order modulation can serve as a tool to investigate whether demodulation of interaurally delayed components is a prerequisite for lateralization. In most of the psychoacoustic experiments presented here, a 25 Hz sinusoidally amplitude-modulated (SAM) 160 Hz tone was either transposed to 4 kHz by half-wave rectifying this SAM waveform before multiplication with a 4 kHz tone (TSAM), or by adding an offset before multiplication (SAMAM). The experiments revealed an inability to lateralize the SAMAM based on ITDs in the 25 Hz component, whereas subjects could lateralize the TSAM. Given that only the TSAM results in a demodulated 25 Hz component after peripheral auditory processing, this result supports the hypothesis that demodulation is a prerequisite for lateralization, which has consequences for temporal modulation processing in models of binaural interaction.
Giant strain-sensitivity of acoustic energy dissipation in solids containing dry and saturated cracks with wavy interfaces
Authors: Zaitsev V. Yu. , Matveev L. A.
Published: January 2012

Mechanisms of acoustic energy dissipation in heterogeneous solids attract much attention in view of their importance for material characterization, nondestructive testing, and geophysics. Due to the progress in measurement techniques in recent years, it has been revealed that rocks can demonstrate extremely high strain sensitivity of seismoacoustic loss. In particular, it has been found that strains of order 10-8 produced by lunar and solar tides are capable of causing variations in the seismoacoustic decrement on the order of several percent. Some laboratory data (although obtained for higher frequencies) also indicate the presence of very high dissipative nonlinearity. Conventionally discussed dissipation mechanisms (thermoelastic loss in dry solids, Biot and squirt-type loss in fluid-saturated ones) do not suffice to interpret such data. Here the dissipation at individual cracks is revised taking into account the influence of wavy asperities of their surfaces quite typical of real cracks, which can drastically change the values of the relaxation frequencies and can result in giant strain sensitivity of the dissipation without the necessity of assuming the presence of unrealistically thin (and, therefore, unrealistically soft) cracks. In particular, these mechanisms suggest interpretation for observations of pronounced amplitude modulation of seismo-acoustic waves by tidal strains.
Spectral processing of two concurrent harmonic complexes
Authors: Shen Yi , Richards Virginia M.
Published: January 2012

In a concurrent profile analysis task, each of the two observation intervals was the sum of two harmonic complexes. In the first interval one of the harmonic complexes had a flat spectrum and the other had a broad spectral peak at 1 kHz. In the second interval, the association between the spectral profiles and the complexes was either consistent with the first interval, or inconsistent so that profile changes (flat versus peaked) could be created in both of the complexes. In two experiments, thresholds and psychometric functions for detecting the profile change were measured in terms of the spectral peak’s magnitude as functions of three types of segregation cues: Difference in fundamental frequency, onset asynchrony, and difference in interaural time difference between the two complexes. Decreasing the magnitude of each cue led to higher thresholds, and shallower psychometric functions whose upper asymptotes often failed to reach 100% correct. The patterns of the threshold and psychometric functions varied across cue types and across individual listeners. The results suggest that informational masking is present in the concurrent profile analysis task. Segregation cues appear to contribute to the release from informational masking, but the process depends on listening strategies adopted by individual listeners.
Effects of mid-frequency active sonar on hearing in fish
Authors: Halvorsen Michele B. , Zeddies David G. , Ellison William T. , Chicoine David R. , Popper Arthur N.
Published: January 2012

Caged fish were exposed to sound from mid-frequency active (MFA) transducers in a 5 × 5 planar array which simulated MFA sounds at received sound pressure levels of 210 dB SPL(re 1 μPa). The exposure sound consisted of a 2 s frequency sweep from 2.8 to 3.8 kHz followed by a 1 s tone at 3.3 kHz. The sound sequence was repeated every 25 s for five repetitions resulting in a cumulative sound exposure level (SELcum) of 220 dB re 1 μPa2 s. The cumulative exposure level did not affect the hearing sensitivity of rainbow trout, a species whose hearing range is lower than the frequencies in the presented MFA sound. In contrast, one cohort of channel catfish showed a statistically significant temporary threshold shift of 4–6 dB at 2300 Hz, but not at lower tested frequencies, whereas a second cohort showed no change. It is likely that this threshold shift resulted from the frequency spectrum of the MFA sound overlapping with the upper end of the hearing frequency range of the channel catfish. The observed threshold shifts in channel catfish recovered within 24 h. There was no mortality associated with the MFA sound exposure used in this test.
Time reversal multiple-input/multiple-output acoustic communication enhanced by parallel interference cancellation
Authors: Song Aijun , Badiey Mohsen
Published: January 2012

Multiple-input/multiple-output (MIMO) techniques can lead to significant improvements of underwater acoustic communication capabilities. In this paper, receivers based on time reversal processing are developed for high frequency underwater MIMO channels. Time reversal followed by a single channel decision feedback equalizer, aided by frequent channel updates, is used to compensate for the time-varying inter-symbol interference. A parallel interference cancellation method is incorporated to suppress the co-channel interference in the MIMO system. The receiver performance is demonstrated by a 2008 shallow water experiment in Kauai, Hawaii. In the experiment, high frequency MIMO signals centered at 16 kHz were transmitted every hour during a 35 h period from an 8-element source array to a wide aperture 16-element vertical receiving array at 4 km range. The interference cancellation method is shown to generate significant performance enhancement, on average 2–4 dB in the output signal-to-noise ratio per data stream, throughout the 35 h MIMO transmissions. Further, communication performance and achieved data rates exhibit significant changes over the 35 h period as a result of stratification of the water column.
Measurement and prediction of voice support and room gain in school classrooms
Authors: Pelegrín-García David , Brunskog Jonas , Lyberg-Åhlander Viveka , Löfqvist Anders
Published: January 2012

Objective acoustic parameters have been measured in 30 school classrooms. These parameters include usual descriptors of the acoustic quality from the listeners’ standpoint, such as reverberation time, speech transmission index, and background noise level, and two descriptors of the acoustic properties for a speaker: Voice support and room gain. This paper describes the measurement method for these two parameters and presents a prediction model for voice support and room gain derived from the diffuse field theory. The voice support for medium-sized classrooms with volumes between 100 and 250 m3 and good acoustical quality lies in the range between −14 and −9 dB, whereas the room gain is in the range between 0.2 and 0.5 dB. The prediction model for voice support describes the measurements in the classrooms with a coefficient of determination of 0.84 and a standard deviation of 1.2 dB.
Perceptual effects of plosive feature modification
Authors: Kapoor Abhinauv , Allen Jont B.
Published: January 2012

In the 1970–1980’s, a number of papers explored the role of the transitional and burst features in consonant-vowel context. These papers left unresolved the relative importance of these two acoustic cues. This research takes advantage of refined signal processing methods, allowing for the visualization and modification of acoustic details. This experiment explores the impact of modifying the strength of the acoustic burst feature on the recognition scores Pc(SNR) (function of the signal-to-noise ratio), for four plosive sounds /ta, ka, da, ga/. These results show high correlations between the relative burst intensity and the scores Pc(SNR). Based on this correlation, one must conclude that these bursts are the primary acoustic cues used for the identification of these four consonants. This is in contrast to previous experiments, which used less precise methods to manipulate speech, and observe complex relationships between the scores, bursts and transition cues. In cases where the burst feature is removed entirely, it is shown that naturally existing conflicting acoustic features dominate the score. These observations seem directly inconsistent with transition cues playing a role: if the transition cues were important, they would dominate over low-level conflicting burst cues. These limited results arguably rule out the concept of redundant cues.
Stability analysis of ultrasound thick-shell contrast agents
Authors: Lu Xiaozhen , Chahine Georges L. , Hsiao Chao-Tsung
Published: January 2012

The stability of thick shell encapsulated bubbles is studied analytically. 3-D small perturbations are introduced to the spherical oscillations of a contrast agent bubble in response to a sinusoidal acoustic field with different amplitudes of excitation. The equations of the perturbation amplitudes are derived using asymptotic expansions and linear stability analysis is then applied to the resulting differential equations. The stability of the encapsulated microbubbles to nonspherical small perturbations is examined by solving an eigenvalue problem. The approach then identifies the fastest growing perturbations which could lead to the breakup of the encapsulated microbubble or contrast agent.
Objective estimation of loudness growth in hearing-impaired listeners
Authors: Silva Ikaro , Epstein Michael
Published: January 2012

A methodology for the estimation of individual loudness growth functions using tone-burst otoacoustic emissions (TBOAEs) and tone-burst auditory brainstem responses (TBABRs) was proposed by Silva and Epstein [J. Acoust. Soc. Am. 127, 3629–3642 (2010)]. This work attempted to investigate the application of such technique to the more challenging cases of hearing-impaired listeners. The specific aims of this study were to (1) verify the accuracy of this technique with eight hearing-impaired listeners for 1- and 4-kHz tone-burst stimuli, (2) investigate the effect of residual noise levels from the TBABRs on the quality of the loudness growth estimation, and (3) provide a public dataset of physiological and psychoacoustical responses to a wide range of stimuli intensity. The results show that some of the physiological loudness growth estimates were within the mean-square-error range for standard psychoacoustical procedures, with closer agreement at 1 kHz. The median residual noise in the TBABRs was found to be related to the performance of the estimation, with some listeners showing strong improvements in the estimated loudness growth function when controlling for noise levels. This suggests that future studies using evoked potentials to estimate loudness growth should control for the estimated averaged residual noise levels of the TBABRs.
Isolating scattering resonances of an air-filled spherical shell using iterative, single-channel time reversal
Authors: Waters Zachary J. , Dzikowicz Benjamin R. , Simpson Harry J.
Published: January 2012

Iterative, single-channel time reversal is employed to isolate backscattering resonances of an air-filled spherical shell in a frequency range of 0.5–20 kHz. Numerical simulations of free-field target scattering suggest improved isolation of the dominant target response frequency in the presence of varying levels of stochastic noise, compared to processing returns from a single transmission and also coherent averaging. To test the efficacy of the technique in a realistic littoral environment, monostatic scattering experiments are conducted in the Gulf of Mexico near Panama City, Florida. The time reversal technique is applied to returns from a hollow spherical shell target sitting proud on a sandy bottom in 14 m deep water. Distinct resonances in the scattering response of the target are isolated, depending upon the bandwidth of the sonar system utilized.
Spatial release from speech-on-speech masking in the median sagittal plane
Authors: Martin Russell L. , McAnally Ken I. , Bolia Robert S. , Eberle Geoff , Brungart Douglas S.
Published: January 2012

Several studies have described a release from speech-on-speech masking associated with separation of target and masker sources in the median sagittal plane. Some have excluded the possibility that small differences between target and masker interaural time disparities can fully account for this release. This study explored the mechanisms underlying the spatial release from speech-on-speech masking that can be obtained in the absence of such differences. In one condition, interaural time disparities were removed from the nominal median-sagittal-plane, head-related impulse responses used to generate the virtual auditory space within which competing sentences were presented. In other conditions, interaural level and spectral disparities also were manipulated by presenting competing sentences monaurally or diotically after convolution with one ear’s head-related impulse responses. It was found that substantial spatial release from masking can be obtained in the absence of any interaural disparities and that such disparities probably make a relatively minor contribution to spatial release from speech-on-speech masking in the median sagittal plane. It is argued that this release from masking is driven primarily by a reduction in informational masking that occurs when monaural information at one, or both, of the listener’s ears facilitates differentiation of competing sentences that emanate from spatially separated sources.
Standards Meetings Calendar–National
Authors: Blaeser Susan B. , Schomer Paul D.
Published: January 2012

American National Standards (ANSI Standards) developed by Accredited Standards Committees S1, S2, S3, and S12 in the areas of acoustics, mechanical vibration and shock, bioacoustics, and noise, respectively, are published by the Acoustical Society of America (ASA). In addition to these standards, ASA publishes catalogs of Acoustical Standards, both National and International. To receive copies of the latest Standards catalogs, please contact Susan B. Blaeser.

Comments are welcomed on all material in Acoustical Standards News.

This Acoustical Standards News section in JASA, as well as the National and International Catalogs of Acoustical Standards, and other information on the Standards Program of the Acoustical Society of America, are available via the ASA home page: http://acousticalsociety.org.
Parasite Invasion Strategy
Authors: Hurtley Stella M.
Published: January 2012

An evolutionarily conserved Ca
2+
-binding protein promotes parasite invasion.
Cocaine Controls Nuclear Import
Authors: Foley John F.
Published: January 2012

Cocaine promotes the nuclear accumulation of histone deacetylase 5, which limits the rewarding effect of the drug.
Headphone use and pedestrian injury and death in the United States: 2004–2011
Authors: Lichenstein Richard , Smith Daniel Clarence , Ambrose Jordan Lynne , Moody Laurel Anne
Published: January 2012

Background

The association between distraction caused by cell phone use while driving and driver/passenger fatalities has been documented, but the safety risks associated with headphone use by pedestrians remains unknown.

Objective

To identify and describe pedestrian–vehicle crashes in which the pedestrian was using headphones.

Methods

A retrospective case series was conducted by searching the National Electronic Injury Surveillance System, US Consumer Product Safety Commission, Google News Archives and Westlaw Campus Research databases for reports published between 2004 and 2011 of pedestrian injuries or fatalities from crashes involving trains or motor vehicles. Cases involving headphones were extracted and summarised. The likelihood of headphone involvement was graded on a three-tier scale based on the information found in the article or report.

Results

There were 116 reports of death or injury of pedestrians wearing headphones. The majority of victims were male (68%) and under the age of 30 (67%). The majority of vehicles involved in the crashes were trains (55%), and 89% of cases occurred in urban counties. 74% of case reports stated that the victim was wearing headphones at the time of the crash. Many cases (29%) mentioned that a warning was sounded before the crash.

Conclusions

The use of headphones with handheld devices may pose a safety risk to pedestrians, especially in environments with moving vehicles. Further research is needed to determine if and how headphone use compromises pedestrian safety.
Using a simulated patient to assess referral for abortion services in the USA: Table 1
Authors: Dodge Laura E , Haider Sadia , Hacker Michele R
Published: January 2012

Background

Women seeking abortion services need to access services in a timely fashion. Quick and appropriate referrals to abortion providers are critical to this process.

Methods

The objective of this study was to determine the quality and quantity of referrals for abortion services from reproductive health care facilities that do not provide abortion services. USA states were ranked by restrictiveness of abortion, and a simulated patient made calls to the five most and six least restrictive states. Referrals were considered direct if the name or telephone number of a facility that provided abortion services was given; indirect when Planned Parenthood was suggested without additional details; and inappropriate if the referral did not provide abortion services.

Results

Of 142 calls, 77 (52.4%) were made to least restrictive states and 62 (45.8%) were made to most restrictive states. Among all calls, even after prompting staff members for a referral, 45.8% resulted in a direct referral, 19.0% resulted in an indirect referral, 8.5% resulted in an inappropriate referral and 26.8% resulted in no referral. Facilities in least restrictive states were significantly more likely to provide unprompted direct referrals (p=0.006) and significantly less likely to provide no referral (p<0.001) than facilities in most restrictive states, though these differences disappeared after prompting the staff member to provide a referral.

Conclusions

A simulated patient received a direct referral for abortion services less than half the time, even after prompting a staff member to provide one. All facilities providing women's health care should have appropriate referrals readily available for patients seeking abortion services.
SPIN AND POLARIZATION WAVES IN A SYSTEM OF PARAMAGNETIC PARTICLES WITH AN INTRINSIC DIPOLE MOMENT
Authors: TRUKHANOVA M. I.
Published: January 2012

We explicate a derivation of a general system of quantum hydrodynamics (QHD) equations for the study of the non-equilibrium processes. Fundamental QHD equations for neutral paramagnetic particles with the own electric dipole moment (EDM) were derived from the many-particle Schrodinger equation. The fact that the influence of spin–spin, dipole–dipole and spin–orbital interaction between particles was taken into account. The problem of definition of spin-waves and polarization waves spectrum in 2D system for the molecules with intrinsic magnetic moments (IMM) and EDM were theoretically investigated and solved for the system of nitric oxide gas in the external electromagnetic fields. The polarization dynamics in system of neutral magnetic and polarized particles is shown to cause formation of a new type of waves as well as changes in the dispersion characteristics of already known waves. Moreover we found the contribution of spin–orbital interaction between gas particles to the elementary excitations and shown that spin–orbital interaction leads to the emergence of magnetization and polarization waves.
RECENT ADVANCES IN FIN-AND-TUBE HEAT EXCHANGER
Authors: WANG CHI-CHUAN
Published: January 2012

The objective of this paper is to summarize the recent progress of fin pattern designs. Some of the designs are from the applied patents and some are from the recent literatures. The fin patterns include interrupted surfaces, enhanced wavy and the vortex generators. Benefits and the associated constraints of these designs are discussed. To effectively improve the heat transfer performance, asymmetric designs offer some promising features in the advanced fin patterns. Moreover, concave depression such as cavity design show significant advantages over conventional interrupted fin surfaces. It is recommended that further detailed examinations on the relevant concepts either via numerical simulation or experimental implementation are carried out in the future to gain further insight into the designs.