bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurements of the pressure field and in vitro stone fragmentation of a Storz Modulith SLX lithotripter
Authors: Cleveland Robin O. , Chitnis Parag V. , Anglade Ronald , Babayan Richard K.
Published: February 2014

The Storz Modulith SLX electromagnetic lithotripter can produce peak pressures higher than most other clinical lithotripters. The pressure field of a clinical SLX was measured with a PVDF membrane hydrophone: the peak-positive pressure varied from 10–115 MPa and the peak-negative pressure from −5 to −15 MPa. The focal spot, based on peak positive pressure, was a cigar shaped volume 25 mm long by 5 mm in diameter. The fragmentation performance was determined by treating artificial kidney stones (cylinders, 9.5 mm long and 6.5 mm diameter, made from Ultracal-30 gypsum) with 400 SWs. After treatment, stone remnants greater than 2 mm in diameter were dried and weighed. We found that fragmentation was very sensitive to correct positioning of the stone. Displacement from the focus by 4 mm or more in the horizontal plane led to a statistically significant decrease in fragmentation (p<0.03). In the vertical direction a displacement of more than 10 mm was necessary to produce a statistically significant reduction in fragmentation. We also found that a slower firing rate of 1 Hz was more effective than 2 Hz (p<0.033) indicating that shock waves can be shielded by cavitation bubbles. [Work partially supported by NIH through P01-DK 43881.]
Compact piezoelectric transducers for lithotripsy
Authors: Dreyer Thomas , Riedlinger Rainer E. , Bauer Edgar , Krauss Werner
Published: February 2014

Self-focusing piezoelectric transducers are widely used in extracorporeal shockwave lithotripsy. This application demands high focal pressure pulse amplitudes, small focal beamwidths and large penetration depths, which results in large transducers with typical dimensions of 350-mm focal distance and 500-mm diameter. Against the background of the development of smaller and therefore more economical devices it is still desirable to reduce the transducer size but keep the acoustic properties. This can be achieved only by an increased initial pressure amplitude at the transducer surface. Since the single piezoelectric elements are driven close to their electrical limit, a different mechanical design is necessary. Piezoelectric elements placed in a layered manner on both sides of a spherical cap could provide a significant increase of the pressure pulse amplitude generated at the transducer surface. Three-dimensional FEM simulations of the transducer structure including all important design parameters, like the electrical drive for both sides, show the ability of generating higher amplitudes by keeping similar pulse shapes. Measurements made on a prototype transducer with a diameter of 270 mm and a focal distance of 200 mm show comparable results to the standard single-layered design regarding peak focal pressure amplitude and spatial amplitude distributions.
Regulating glottal airflow in singing: Application of the maximum power theorem
Authors: Titze Ingo R.
Published: February 2014

Two competing views of regulating glottal airflow for maximum vocal output are investigated. The maximum power transfer theorem is used as a guide. A wide epilarynx tube (laryngeal vestibule) matches well with low glottal resistance (the yawn-sigh approach), whereas a narrow epilarynx tube matches well with a higher glottal resistance (the twang-belt approach). A simulation model is used to calculate mean flows, peak flows, and oral radiated pressure ratio between the vocal tract (the load) and the glottis (the source). Results show that when the ratio approaches 1.0, maximum power is transferred and radiated from the mouth. [Work supported by NIH.]
Measuring residual stresses in a steelpan
Authors: Peekna Andres , Rossing Thomas D.
Published: February 2014

By bonding strain gage rosettes to a steelpan and drilling a small hole, it is possible to measure the residual stresses at selected locations on a steelpan. The accuracy of the method depends upon the extent to which the stresses and strains change with depth below the surface on which the strains are measured. The residual stresses in a tenor steelpan, ‘‘sunk’’ by hammering in the usual way, appear to be mostly compressive in the middle ring of notes, changing to tensile in the outer ring. The effect of heating on the residual stresses is discussed.
Active control and adaptive structures for a smart violin
Authors: Hanagud Sathya , Lu Xia
Published: February 2014

String instruments, like the violin, have been studied for the past 350 years. These studies have focused on the quality of the wood, dynamic characteristics of these instruments and structural acoustics and psychoacoustics. The emphasis of the previous research was to understand the secrets of great designers of these instruments. For example, one would like to explain reasons for the legendary quality of the sound radiated by a Stradivarius and the price that it commands today. Many researchers have also suggested passive techniques to improve the quality of these musical instruments. However, no attempts have been made to use active structural control and smart structures to modify the quality of the music radiated by these instruments like the violin. In this paper, we start with the assumption that the legendary quality of the sound radiated by a Stradivarius is due to its special structural dynamic or structural-acoustics characteristics. Our approach is to use the concepts of adaptive or smart structures and active structural control to improve the quality of the sound radiated by these musical instruments. Procedures are developed to change the structural dynamic characteristics, actively, to replicate the structural dynamic characteristics of musical instruments developed by great masters.
Improvement of the concert harp through the application of composites
Authors: Preissner Curt , Royston Thomas J.
Published: February 2014

The replacement of a Sitka spruce grand concert harp soundboard with a fiber-reinforced plastic soundboard was considered for improved durability and long-term stability. First, a means of nondestructively identifying the structural acoustic properties of a conventional wooden soundboard was developed based on a multi-mode dynamic identification technique available in the literature. This was followed by the development of a design process to reproduce the same structural acoustic properties in the composite replacement. It was found that specific matching criteria must be met to achieve a dynamic response that closely approximates the wooden soundboard. Lay-up of the composite soundboard was guided by this matching criteria and Tsais orthotropic plate design procedure. Experimental verification was then performed utilizing the same system used to identify the wooden plate properties. The identification technique and composite replacement design process may be applicable to other musical instruments, as well as other nonmusical, orthotropic plate structures.
Acoustical measurements on carved Baltic psalteries
Authors: Peekna Andres , Rossing Thomas D.
Published: February 2014

Modes of vibration in several successful replicas of carved Estonian kannels, an outstanding Latvian–American kokle, and a reconstruction of a Novgorad gusli were determined by electronic TV holography. From the characteristics of the various resonances, as well as the sound of the instruments, we conclude that a successful Baltic psaltery should have: (1) a maximum number of resonances within the tuning range; (2) a strong resonance between the keynote and the note above; and (3) a strong resonance also at the low dominant. Not only the overall soundhole area but their locations can have significant effect on sound quality and volume.
Transposed stimuli reveal similar underlying sensitivity to interaural timing information at high and low frequencies
Authors: Bernstein Leslie R. , Trahiotis Constantine
Published: February 2014

Threshold interaural temporal disparities (ITDs) obtained at high frequencies are typically much larger than those obtained at low frequencies. Colburn and Esquissaud [J. Acoust. Soc. Am. Suppl. 1 59, S23 (1976)] attributed this to differences in the peripheral, monaural processing of the stimuli. They hypothesized that neural impulses synchronized to the waveform at low frequencies and to only the envelope at high frequencies serve as inputs to a binaural processor that functions similarly at low- and high-signal frequencies. This hypothesis was supported in ITD-discrimination experiments employing novel, high-frequency ‘‘transposed stimuli’’ designed to provide high-frequency channels with envelope-based information that mimics information that is normally available only in low-frequency channels. That is, when the inputs to the high-frequency binaural channels were provided with information like that normally available at low frequencies, sensitivity to ITD in the two spectral regions was found to be similar. The data at both low and high frequencies were well accounted for, quantitatively, in terms of a constant-criterion change in normalized interaural correlation computed subsequent to bandpass filtering. compression, rectification, and low-pass filtering. [Work supported by NIH.]
Temporal resolution in an interaural temporal difference discrimination task with distracter stimuli
Authors: Erpenbeck Eric A. , Grantham D. Wesley
Published: February 2014

Interaural temporal difference (ITD) thresholds were determined for brief (14-ms) 500-Hz tone bursts in a two-interval forced-choice paradigm in which the interstimulus interval was 36 ms. Preliminary data indicate that the ITD threshold can be affected by the presence of a third (distracter) burst temporally centered between the two primary bursts on each trial: When the distracter has the same ITD as the final burst of the pair, the ITD threshold is unchanged or decreases relative to in the no-distracter condition; when it has the same ITD as the first burst, the threshold increases. The results are consistent with the hypothesis that, when presented with a rapid three-burst triad, the binaural system processes the ITD of the first burst normally (i.e., as if presented in isolation), but confuses or averages the ITDs of the latter two bursts. Follow-up experiments will measure the effects of the discrete nature of the distracter (i.e., by removing the silent gap between the distracter and the burst that shares its ITD), and the frequency of the distracter on the magnitude of its effect. Results will be discussed in terms of binaural temporal resolution of onset versus post-onset information. [Supported by NIDCD.]
Detection of amplitude modulation and discrimination of interaural differences in modulation phase for high-frequency carriers
Authors: Stellmack Mark A. , Viemeister Neal F.
Published: February 2014

Using a 4-kHz pure-tone carrier and modulation frequencies (fm) of 2–512 Hz, thresholds for monaural detection of sinusoidal amplitude modulation (SAM) were measured, as were threshold modulation depths for the discrimination of interaurally in-phase and out-of-phase SAM envelopes. For one listener, interaural differences in envelope phase for fm up to 256 Hz were discriminable at modulation depths (m) for which the monaural modulation itself was just detectable, and all monaural and binaural thresholds were within a range of 5 dB (20 log m) across fm. For a second listener, binaural thresholds increased more rapidly with increasing fm than monaural thresholds. Another experiment examined the notion that interaurally delayed SAM envelopes are processed as time-varying interaural level differences. In this task, listeners discriminated interaurally in-phase SAM envelopes from SAM envelopes carrying a fixed interaural phase difference (IPD). Threshold m was measured for several fm and IPD combinations. For a given IPD, thresholds were either constant or decreased with increasing fm. The data suggest that dynamically varying interaural level differences are the cue to discrimination at low fm, while the fixed interaural time difference is the likely cue at high fm. [Work supported by NIDCD DC00683.]
Peripheral auditory processing and the precedence effect
Authors: Hartung Klaus , Trahiotis Constantine
Published: February 2014

This work addresses how a consideration of peripheral auditory processing can help one to understand the relative salience of binaural information conveyed by successive binaural transients in precedence experiments. It appears that much of the variability in the data is amenable to an explanation based on peripheral interactions that result from auditory filtering and the functioning of hair cells in combination with a binaural model based on cross correlation. This approach does not include inhibitory mechanisms that are commonly considered as being necessary in order to account for the precedence effect. [Work supported by NIH.]
Modeling the effect of torso on the head-related transfer function via the boundary-element method
Authors: Gumerov Nail A. , Tang Zhihui , Duraiswami Ramani , Duda Richard O. , Algazi V. Ralph , Raveendra S. T.
Published: February 2014

The head-related transfer function (HRTF) depends on many parameters including the parameters of torso. The goal of this study is to understand and evaluate the influence of torso on the HRTF. For this purpose a simplified model consisting of a spherical head and an ellipsoidal torso was investigated using a boundary-element method. The use of this simplified model for modeling of the human body is justified for relatively low frequencies (frequencies below 1500 Hz). Solutions of a 3-D Helmholtz equation for monopole source and various positions and orientations of the body relative to the source of sound are obtained using the boundary-element method. The results are compared with analytical results of Duda and Martens [J. Acoust. Soc. Am. 104, 3048–3058 (1998)] and computations in the absence of torso and results of Avendano et al. [IEEE Workshop on Applications of Signal Processing to Audio and Acoustics, New Paltz, NY, 1999] in the presence of torso. The influence of the torso on the angular and frequency dependencies of the HRTF is then identified, evaluated, and discussed. Also discussed is the influence of the torso in modifying the HRTF with the pose of the head. [Work supported by NSF.]
Effects of visual-feedback training in 3-D sound displays
Authors: Zahorik Pavel , Tam Clement , Wang Kenneth , Bangayan Philbert , Sundareswaran V.
Published: February 2014

Current low-cost 3-D sound displays do not use individualized head-related transfer functions (HRTFs) to render acoustic space. As a result, sound source localization accuracy is often degraded when compared to the accuracy using real sources, or to higher quality displays using individualized HRTFs. Here, a way to improve accuracy was examined in which listeners were provided with paired auditory and visual feedback as to the correct sound source location. Sound localization accuracy was assessed for six listeners, using a large number of virtual sound sources sampled from a spherical grid surrounding the listener, before, during, and after feedback training. Feedback training markedly improved localization accuracy compared to a control group of five listeners that did not receive training. The largest improvements in accuracy resulted from listeners’ enhanced abilities to distinguish sources in front from sources behind. Further, these improvements were not transient short-term effects, but lasted at least 4 days between training and testing sessions. These results suggest that simple and relatively short periods of feedback training (two 45-min sessions) can effectively facilitate perceptual re-mapping to modified spatial cues, and therefore mitigate technical deficiencies in 3-D sound systems due to nonindividualized HRTFs. [Work supported by ARL-FedLab.]
David Crighton and structural acoustics with mean flow
Authors: Peake Nigel
Published: February 2014

David Crighton wrote a number of significant papers on structural acoustics, but the one which has provoked the most discussion is concerned with the causal response of an elastic plate to unsteady forcing in the presence of mean flow [Crighton and Oswell, Philos. Trans. R. Soc. London, Ser. A 335, 557–592 (1991)]. A number of exceedingly unusual features arise in this problem, including absolute instability at high flow speeds, negative energy waves and the existence of neutral modes which violate the usual Rayleigh–Lighthill condition of out-going group velocity. A number of developments have been made since 1991, by Crighton himself and by Peake, and some of these will be described in this presentation. These include the effects of plate curvature and the presence of a boundary layer, both of which act to push the absolute instability to unrealistically high flow speeds; the dynamics of composite plates which allow shear deformation; and the effects of nonlinearity. In the latter regard it will be shown how negative energy waves are saturated at finite amplitude, and how solitary waves can develop over a wide parameter range.
Approximate factorization of Wiener–Hopf kernels
Authors: Abrahams I. David
Published: February 2014

The key step in the solution of a Wiener–Hopf equation is the factorization of the Fourier transform of the kernel, K(α) (here, α is the Fourier variable). Exact factorizations are seldom useful, either because they do not exist or because they are too cumbersome to evaluate accurately. It is desirable, therefore, to construct approximations of K(α) which are both easy to factorize and simple to evaluate. Recently, Crighton examined the case that K depends on a small parameter, ε; i.e., K=K(α;ε). Crighton showed that matched asymptotic expansions (MAE) can be used to construct a composite asymptotic approximation to K for ε→0, valid uniformly over the full required range of α. The composite approximation comprises several relatively simple factors in typical applications, and these factors are then decomposed into their Wiener–Hopf factors by standard techniques. Abrahams has introduced an alternative approximation method for Wiener–Hopf kernels based on Padé approximants. Padé approximants give explicit uniform approximations to K valid in the full relevant range of α, do not require a small expansion parameter, and can be computed with relatively little effort. Although Crighton’s and Abrahams’s approaches seem at first glance unrelated, this talk will show that under certain circumstances, they are closely related.
Asymptotic theory of propeller noise
Authors: Parry Anthony B.
Published: February 2014

This paper describes noise radiation from open rotors. The starting point is the expression for noise radiation due to either the blade loading distribution or the blade thickness distribution. These expressions, involving integrals over the blade surface, are themselves obtained from the Ffowcs WIlliams-Hawkings equation. Using the assumption that the number of blades is large, it is possible to evaluate the integrals asymptotically and to show precisely how the farfield radiation is dominated by contributions from a few regions of the blade. At subsonic conditions, the noise is, of course, completely tip generated. At supersonic conditions the radiation is, to leading order, dominated by the Mach radius: the radius that approaches the observer at precisely sonic speed. At supersonic conditions there is also a significant lower order term, originating at the blade tip. The results for all cases show the explicit dependence on tip Mach number, harmonic number and radiation angle. Excellent agreement is obtained between the asymptotic results and full numerical evaluation of the acoustic field. The formulas are also extended to predict the acoustic benefit of sweep.
Acoustic backscattering and coupling processes for elastic and plastic circular disks in water: Direct and holographic observations
Authors: Marston Philip L. , Hefner Brian T.
Published: February 2014

Coupling and mode conversion processes can cause significant backscattering enhancements for scattering by tilted circular disks in water. These were investigated by direct observation of the backscattering as a function of the tilt of the disk and, in the case of elastic disks, using acoustic holography. The coupling of symmetric Lamb waves onto the elastic disk and an associated made conversion to (and from) in-plane shear waves was important for the tilted elastic disk [B. T. Hefner and P. L. Marston, Acoust. Res. Lett. Online 2, 55–60 (2001)]. In a different range of tilts and at a sufficiently high frequency, a (higher-order) antisymmetric edge wave that propagated around the perimeter of the elastic plate was important. Tilted plastic disks displayed anomalous enhancements for tilts near (but beyond) a critical angle associated with the internal total reflection of a shear wave from the edge of the plate. Other enhancements are also present for tilted plastic plates. [Work supported by ONR.]
Visibility of David Crighton and ultrasonic waves
Authors: Breazeale M. A.
Published: February 2014

Visibility of David Crighton is assured through his many useful publications. He was able to make his theoretical results seem simple and understandable. Visibility of ultrasonic waves is another matter. In our understanding we are aided by another Fellow of the Royal Society. Lord Rayleigh used collimated light incident on a grating. He showed that behind the grating there is a series of real images with an optical periodicity of magnitude (2b2)/l where b is the grating spacing and l is the optical wavelength. For the ultrasonic analog we substitute a standing ultrasonic wave for the grating, then we superimpose a scale on the images of the ultrasonic wave-fronts. This becomes a simple but sensitive means of measuring ultrasonic wave velocity in transparent media.
Scattering of sound by laminar wake of symmetric moving body
Authors: Semenov Andrew G. , Rybak Samuel A. , Alekseev Vadim N.
Published: February 2014

The report is based on analysis of sound propagation in the vicinity of a rather general class of localized flows induced by the motion of symmetric structures of the type of solid spheres and droplets or vortices in the liquid. Acoustic scattering on such inhomogeneities, situated inside various flows, was performed with the aid of boundary value problem solution for the M. Lighthill equation. The role of a moving body which generates an inhomogeneity as well as a role of surface at which the tangential component of flow velocity could suffer a discontinuity are demonstrated in a rather general form. Comparison of body and flow contribution to observed scattered field is presented. Flow presumable yield in the forward scattering direction situation of the type encountered in conventional underwater or biomedical tomography system, comprising the source–receiver observation line, is underlined. Details and specific features are demonstrated for well-known (classical) hydrodynamic flow types, such as potential and viscose flows around moving sphere, and especially for symmetric laminar wake. Scattered sound angular structure and frequency dependencies are derived. The influence of flow Mach and Reynolds number value ranges on sound scattering intensity are discussed.
Practical considerations in evaluating directional hearing devices
Authors: Dai Huanping , Petrovic Srdjan , Michael Nick , Olson Laurel , Pavlovic Chaslav
Published: February 2014

In theory, a directional hearing device could apply large attenuation to a single noise source and achieve great enhancement of signal-to-noise ratio relative to an omni-directional device. However, as observed in many clinic studies, the actual benefit of a directional device measured in typical rooms rarely exceeds 6 dB, even in conditions with a single noise source located in the direction of maximum attenuation of the device. This dramatic reduction from the theoretical benefit is a manifestation of many factors, including mismatch in the microphone responses, misalignment of the device relative to the target source, head movement, head shadow, room reverberation, and so on. In the present study, we examine the relative contributions of these factors using computer simulations and electroacoustical measurements. The results provide a basis for setting realistic expectations of the benefit of directional devices for specific listening environments.
A mathematical theory of comodulation
Authors: Jacobson Barry D. , Cauwenberghs Gert , Litvak Leonid M.
Published: February 2014

Amplitude comodulation is the phenomenon that for many types of sound sources, all of the individual frequency components emitted will be amplitude modulated in a related manner, i.e., they will all start/stop and rise/fall together. It is known from various psychophysical studies that comodulation plays an important role in perceptual grouping of sound components. In this work, amplitude comodulation is examined for possible use as a basis for auditory source separation. A derivation is presented of the equations governing a comodulated system for the case of constant frequency sources. A theorem is proved giving necessary and sufficient conditions for uniquely decomposing a sound mixture into its constituent sources. A by-product of these conditions is an understanding of the importance of common onsets and offsets in source separation. An algorithm is presented for computing the unique solution in those cases where one exists. Finally, possible future extensions to the case of frequency varying sources are discussed. [Work supported by NIH Training Grant No. 5T32 DC00038.]
Eyes and ears: Attentive teleconferencing utilizing audio and video cues
Authors: Kapralos Bill , Jenkin Michael , Tsotsos John , Milios Evangelos
Published: February 2014

The multiple speaker teleconferencing systems currently available typically focus on a single speaker and provide limited, if any, automatic speaker tracking technologies. However, in a multiple-speaker setting, speakers must be localized and tracked in both the video and audio domains. Although many fast and portable video trackers capable of locating and tracking humans exist, they employ conventional cameras thereby providing a narrow field of view. In addition, audio localization systems are expensive, nonportable, and computationally intensive. Furthermore, there have been very few attempts to combine both audio and visual systems. This work investigates the development of a simple, economical, and compact teleconferencing system utilizing both audio and video cues. An omni-directional video sensor is used to provide a view of the entire visual hemisphere thereby providing multiple dynamic views of all participants. Using a statistical color model and simple geometrical properties, the location of each participant’s face is determined and provided to the audio system as a possible direction to a sound source. Beam forming with a small, compact microphone array allows the audio system to detect and focus on the speech of each participant. The results of experiments conducted in normal, reverberant environments indicate the effectiveness of the system.
Shallow water performance of a time-reversing array with a moving source
Authors: Sabra Karim G. , Dowling David R.
Published: February 2014

Future active sonar systems may be developed from the automatic spatial and temporal focusing properties of time-reversing arrays (TRAs) in unknown environments. In the case of source and/or array motion, both the forward and backward propagation necessary for TRA operations may be influenced by the Doppler effect. Predictions for TRA focusing performance for a single source emitting broadband or narrowband Doppler-shifted signals in a shallow-water waveguide can be obtained from a Fourier superposition of stationary but spatially distributed time-harmonic sources. This approach is illustrated for a Pekeris waveguide and extended to range-dependent environments with the wide-angle parabolic equation code RAM (by Collins). Results for the characteristics of the retrofocused field will be presented for different combinations of source-array motion and geometry for acoustic center frequencies of several hundred Hertz and nominal ranges of up to 20 km in a range-independent sound channel. Results from fully range-dependent sound channels may also be presented. [Work sponsored by ONR.]
Optimal array design and sensitivity for mode filtering
Authors: Shiao Tsung-Jieh , Buck John R.
Published: February 2014

The Cramer–Rao lower bound (CRLB) gives the smallest possible variance of any unbiased estimator. Buck, Preisig, and Wage [J. Acoust. Soc. Am. 103 (1998)] derived this bound for the variance of unbiased mode filters and observed that the array geometry is the only factor controlling performance under scientists’ control. The difficulty lies in designing an appropriate array for variable ocean environments. This research includes two parts. First, the minimax optimization criteria and the gradient descent method are applied to find optimal arrays over a range of possible deployment environments. In several simple prototype problems, it is possible to design nonuniform arrays whose worst case CRLB is significantly lower than a uniformly spaced array. This contradicts conventional wisdom that uniformly spaced arrays provide the most flexibility for multiple or extended deployments. Moreover, the gradient descent method is more computationally efficient than exhaustive search methods of optimizing arrays. Second, the sensitivity of the optimal array’s performance to environmental mismatch is studied and the perturbation of this performance is analytically bounded. This bound works well in the preliminary results and predicts the deterioration of mode filter performance due to mismatch. [Work supported by ONR Young Investigator Program.]
Generalized optical theorem for two-dimensional scattering: Applications to backscattering and arbitrary scattering angles
Authors: Marston Philip L.
Published: February 2014

A generalized optical theorem has been demonstrated for scattering by three-dimensional targets having no energy dissipation as well as inversion symmetry [P. L. Marston, J. Acoust. Soc. Am. (accepted for publication)]. A component of the complex scattering amplitude in an arbitrary direction is expressed in terms of a two-dimensional angular integration involving scattering amplitudes. The integral may be reduced to a one-dimensional integration only in special cases such as backscattering along a symmetry axis. In new research an analogous theorem for two-dimensional scattering is found. The theorem for two-dimensional scattering allows (for an arbitrary direction) a projection of the complex scattering amplitude to be expressed as a one-dimensional integral. The integral is a circular-autocorrelation of complex scattering amplitudes from −180 deg to +180 deg. This was numerically evaluated for simple targets to confirm the theorem. Potential applications of generalized optical theorems include the verification of the consistency of scattering approximations and investigations of multiple-scattering by inversion-symmetric sets of scatterers. [Work supported by ONR.]
Characterization of underwater explosions by cepstral analysis, modeling and inversion
Authors: Baumgardt Douglas R. , Freeman Angelina M.
Published: February 2014

This paper describes a cepstral simulation and inversion algorithm for characterizing regional seismic recordings of underwater explosions to determine the yield and depth of the explosions. The spectra of seismic recordings of underwater blasts have strong time-independent spectral scalloping, produced by the correlated bubble pulses and echoes of acoustic reflections between the water surface and the sea bottom. Signed cepstra, computed from the Fourier transform of the log-amplitude spectra of regional seismic phases (Ph, Pg, Sn, and Lg), contain positive peaks produced by the bubble pulse correlation, and negative peaks from the water-surface reflection. Theoretical cepstra of underwater explosions with assumed depths and yields are computed from simulated time sequences of bubble pressure pulses and water column reflections. The prototyped inversion algorithm determines explosion depth and yield by matching the synthetic model cepstra to data cepstra, using exhaustive and optimized search methods. This algorithm has been applied to presumed underwater explosions in the North Sea, tested successfully on three calibration explosions in the Dead Sea, and utilized for the analysis of the Kursk submarine event, a presumed underwater explosion. [Work supported by DTRA.]
An approach to array element localization using a far-field source
Authors: MacInnes Craig S. , Knobles David P.
Published: February 2014

An approach is introduced for the towed array element localization problem. The method uses a dominant acoustic far-field source to obtain the true array shape. Constraints are introduced that significantly reduce the dimensionality of the problem. The array shape is expanded in terms of Chebyshev type II polynomials. The array elements are constrained to be in sequential order, and the arc length between elements is conserved as the array transforms from a straight to a curved configuration. A simulated annealing (SA) algorithm is used to find the expansion coefficients that minimize the inverse of the magnitude of the plane-wave beamformer response evaluated at the bearing to the source. The minimum of the cost function is obtained when the array elements are in their correct positions. Simulated studies are made for several array shapes. In all cases examined the expansion method with SA is able to find an accurate solution, independent of the initial array configuration. The analysis suggests that the use of broadband as opposed to single-frequency cost functions has the effect of reducing the number of local minima in the cost function that have values near the global minimum. [Research supported by the U.S. Navy.]
The crack-of-the-bat: The acoustics of the bat hitting the ball
Authors: Adair Robert K.
Published: February 2014

When a baseball is hit straight at an outfielder he cannot quickly judge the angle of ascent and the distance the ball will travel. If his first step is wrong (in for a long fly ball or back for a short fly ball) the turnaround time reduces his range and he will miss catchable balls. To help his judgment the professional ball player listens to the sound of the wooden bat hitting the ball. If he hears a ‘‘crack’’ he runs out, if he hears a ‘‘clunk’’ he runs in. The crack occurs if the ball is hit near the sweet spot, little collision energy is lost to bat vibration but is returned to the ball which then sails a long distance. The collision time is then near 0.5 ms generating a singular acoustic disturbance of about that time duration—thus a ‘‘crack.’’ If the ball is hit off of the sweet spot, much of the collision energy will be expended in bit vibrations near 170, 560, and 1100 Hz. With that energy diverted to the collision energy, the ball will not go very far and the vibrations generate persistent sound waves that add to a diminished singularity to sound a ‘‘clunk.’’
The sounds of baseball: The bat–ball collision and the crack of the bat
Authors: Collier Robert D.
Published: February 2014

The crack of the bat is one of the most exciting aspects of the game of baseball. This sound provides significant information to both player and spectator. The impact force between a fast ball pitch and a rotating bat provides the energy for the exit velocity of the ball. The relative efficiency of the energy transfer to the batted ball is related to the location of the impact area on the bat, e.g., the sweet spot, and the duration of the period in which the ball is in contact with the bat. Energy losses in the bat involve the vibratory modal response of the bat and its associated sound radiation. This paper discusses the modal response functions of both solid wood and tubular metal in relation to the location and nature of the impact forces generated by collisions with baseballs. Differences in amplitude, spectral characteristics and decay rates of the resulting radiated sound fields are analyzed for a range of bat–ball collision scenarios. Experimental results from both controlled laboratory and field hitting tests illustrate the relationships between measured bat radiated sounds and the subjective evaluation by players of batted ball trajectories.
Acoustics sound systems for baseball
Authors: Brown Jim
Published: February 2014

Acoustic considerations impact the design of sound systems for baseball stadiums in several important ways. Intrusion by the sound system into adjacent residential communities must often be minimized. Excess attenuation greatly increases the required high frequency component of acoustic power for sound travelling long distances, while wind and temperature gradients modify the effective coverage patterns of loudspeaker systems, and exacerbate community noise problems. These atmospheric effects can vary radically from moment to moment. These considerations tend to favor use of distributed systems, at the same time architectural considerations make them more difficult to implement. And especially with distributed systems, the timing of sound arrivals at each listener’s ear is often more important than the overall amplitude of the sound field. In modern stadiums, other auxiliary systems are required. Crowd mics fed to distributed loudspeakers must bring the crack of the bat and the ‘‘smell of the crowd’’ into private suites which are often enclosed. That crowd noise, along with the public address announcer, must also be fed to broadcast media for their use. Timing is also an issue with these systems. This paper addresses both design challenges and practical solutions.
Renal vasoconstriction following shock wave lithotripsy (swl) is mediated by renal nerves
Authors: Connors Bret , Evan Andrew , Willis Lynn , Simon Jay , Shalav Arieh , Paterson Ryan , Lingeman James
Published: February 2014

High-energy shock waves (SWs) to one kidney (2000 SWs at 24 kV) reduces blood flow in both kidneys (65% in shocked kidneys, 33% in contralateral unshocked kidneys). We determined if unilateral renal denervation of the unshocked kidney alters renal blood vessel constriction after SWL. Six-week-old pigs underwent unilateral kidney denervation. Visible renal nerves along the renal artery of one kidney were isolated, cut, and painted with 10% phenol. Two weeks later, the pigs were anesthetized and kidney function was followed with inulin and PAH clearance. 2000 SWs (at 24 kV, Dornier HM3) were applied to the lower pole of the innervated kidney. Bilateral glomerular filtration rate (inulin clearance) and renal plasma flow (PAH clearance and extraction) were measured 1 h before and 1 h after SWL. Both kidneys were then removed to determine norepinephrine (NE) content in the tissue. Denervation reduced NE levels to 8.7% of innervated kidneys. While blood flow fell as expected in the innervated shocked kidney, there was no change in blood flow in the denervated kidney. Results suggest that renal nerves mediate part of the vasoconstrictor response of unshocked kidneys to SWL. [Work supported by NIH P01 DK43881.]
Sound interaction with moving vortices
Authors: Rybak Samuel A. , Semenov Andrew G. , Alekseev Vadim N.
Published: February 2014

This report is devoted to the nonlinear acoustic pressure of sound waves propagating in the vicinity of a rather general class of localized flows induced by the motion of spherically symmetric structures of the type of vortices in the liquid, say, biological, atmosphere, or ocean inhomogeneous environment. As a result expressions for cyclic and mean forces exerted on a vortex are derived. Conventional general expression for transport cross section derived in nonlinear theory of interaction of sound with rigid particles is proven to be incorrect for the vortex-sound interaction case. The absence of mean force is demonstrated for specific case of Hills vortex both in the traveling and standing sound wave fields. It is underlined, however, that the force could be observable if the distribution of mean sound energy in the incident sound field in the frames of vortex dimensions could be characterized by a nonzero spatial gradient. Instead of the previously used expression for mean radiation force exerted on a moving inhomogeneity valid for a solid particle based on its transport cross section, the correct generalized expression for force exerted on vortex structure is derived.
Waves in fluid and solid media
Authors: Domański Wl/odzimierz
Published: February 2014

‘‘Waves in Fluid and Solid Media’’ is the title of the last unpublished lecture notes of David G. Crighton. The lectures were given at the University of Cambridge and have the date Lent 1998. In these notes Crighton introduces basic notions connected with wave motion, analyzing in particular propagation of sound waves in a compressible fluid as well as dilatational and shear waves in an elastic solid. A part of these lectures is devoted to nonlinear acoustics including the discussion of wave steepening, formation of shocks, Rankine–Hugoniot conditions, Hugoniot adiabatic etc. In my talk the above mentioned ideas will be extended and recent developments in the theory of propagation and interaction of weakly nonlinear waves both in fluid and solid media will be presented [W. Domański, Contemp. Math. 255, 45–61 (2000)].
Learning to recognize spectrally reduced speech: A cochlear implant simulation study
Authors: Chiu C.-Y. Peter , Strange Bethany , Brockman James
Published: February 2014

This study investigated training-related improvement in open-set identification of sentences that were spectrally reduced to four channels using the CIS processing strategy [Shannon et al., J. Acoust. Soc. Am. 104, 2467–2476 (1998)]. Over the course of 11 training blocks, listeners with normal hearing identified Harvard IEEE [IEEE Trans. Audio Electroacoust. 17, 225–246 (1969)] sentences with feedback. Half of the listeners listened to a male talker during training; the other half to a female talker. Listeners were tested at different points with blocks of IEEE sentences spoken by the familiar talker, blocks of IEEE sentences by the novel talker, blocks of IEEE sentences by the two talkers randomly intermixed, and blocks of HINT sentences [Nilsson et al., J. Acoust. Soc. Am. 95, 1085–1099 (1994)]. Preliminary data showed an improvement in sentence identification over the course of training. The data also showed a trend of talker specificity for such improvement, in that sentences produced by the novel speaker were harder to identify. In some instances, random intermixing of talkers led to poorer performance than having just one talker within a testing block. Implications for theories of auditory memory and for practical aspects of training will be discussed. [Work supported by URC, Univ. of Cincinnati.]
Quick SIN and BKB-SIN, two new speech-in-noise tests permitting SNR-50 estimates in 1 to 2 min
Authors: Killion Mead C. , Niquette Patricia A. , Revit Lawrence J. , Skinner Margaret W.
Published: February 2014

The evolution of two new speech-in-noise tests is described, with particular emphasis on obtaining equivalency across lists. The Quick SIN Test uses IEEE sentences with female talker (L. Braida, personal communication on Harvard Phonetically Balanced Sentences developed at Harvard University during WWII, 2000); the BKB Test uses British Childrens sentences with male talker (Jon Shallop) [J. Bench and J. Bamford (eds.), Speech-Hearing Tests and the Spoken Language of Hearing-Impaired Children (Academic, London, 1979)]. In both cases, the Auditec of St. Louis four-talker babble recording was used to provide competing noise, and SNR-50 (signal-to-noise ratio for 50% correct key words in sentences) was estimated using the Tillman–Olsen recommendation [T. W. Tillman and W. O. Olsen, Modern Developments in Audiology, 2nd ed. (Academic, New York, 1973), pp. 37–74]. Normal-subject testing as well as hearing-impaired and cochlear-implant subject testing was used to check for equivalency across a range of signal-to-noise ratio performances. The standard deviation for single and multiple lists will be reported.
Case study: Speech production following cochlear implantation in a postlingually deafened adult
Authors: Shadle Christine H. , Brinton Julie , Verschuur Carl , Blacklock Oliver S.
Published: February 2014

While cochlear implants are designed primarily to aid speech perception, some aspects of speech production may improve post-implant in postlingually deafened speakers. Postural parameters such as average SPL may change immediately; phonemic parameters such as place changes allowing [s, ∫] to be distinguished may continue to change for two years or more post-implant [Matthies et al., J. Acoust. Soc. Am. 96, 1367–1373 (1994)]. In this paper we describe a female subject who received a cochlear implant following a progressive hearing loss from age 5. She became profoundly deaf at age 34, and was implanted at age 35 with a Nucleus CI24M. She was recorded saying an extensive speech corpus pre-implant and at intervals post-implant. Pre-implant, she had a very weak and creaky voice quality, and /s,z/ were consistently produced as silence, or one of [t, d, θ, ð, t∫]. Defining parameters to characterize the errors in manner is not straightforward, however. She received some speech therapy post-implant; her voice quality gradually improved, but the /s,z/ errors persisted. Her aided hearing levels and sentence perception results at 18 months are excellent. However, her Speech Perception Audiometry and consonant confusion results demonstrate difficulties and may help explain the continued [s,z] production problems. [Research funded in part by EPSRC.]
Speech processing and memory throughout the lifespan
Authors: Surprenant Aimee M.
Published: February 2014

Research on cognitive aging has converged on the concept of speed of processing to explain certain age-related declines in cognitive capabilities. According to this explanation, older adults perform worse on a variety of tasks because they process information at a slower rate than younger adults. This view, however, does not address the question of why older adults might process information more slowly. This study investigated the hypothesis that noise and/or mild hearing loss can cause difficulty in perceptual processing which, in turn, affects cognitive processing. The extra effort required to identify each stimulus draws resources normally devoted to higher-level processes. Forty normal or near-normal hearing subjects, ranging in age from 30–75 years participated in a variety of hearing and cognitive tasks. The main finding was that performance on a memory for syllables in noise task was predicted by performance on an identification of words in noise task, regardless of the age of the listener. These results suggest that one possible factor underlying slower cognitive processing as we age is more effortful sensory processing. [Work supported by a Gerontology Pilot Grant from Purdue University.]