bluuebunny/crossref_metadata_2025 huggingface dataset:
On the analogy between the one-dimensional acoustic waveguide and the electrical transmission line
Authors: Russell G. A. , Hjerpe E. D.
Published: October 2005

Equations for the electrical transmission line provide an analogy to the one-dimensional acoustic waveguide equations. The equations allow for either a pressure to voltage or a pressure to current analogy to be employed. The appropriate analogy to use is shown to be that of pressure to voltage.
Polynomial expressions for the coefficient of nonlinearity β and β/(ρc5)1/2 for fresh water and seawater
Authors: Cotaras F. D. , Morfey C. L.
Published: October 2005

In this Letter, polynomial expressions are presented for the coefficient of nonlinearity β for both seawater and fresh water. The seawater relations are for salinities of 30–40 ppt, temperatures of 0–40 °C, and pressures of 1–800 bars absolute. The fresh water relations are for temperatures of 0–90 °C and pressures of 1–1000 bars absolute. Also presented are polynomial expressions for the term Λ≡β/(ρc5)1/2, which arises in nonlinear geometrical acoustics. The precision of the fits of the polynomials to the underlying data is better than 1 ppt in all cases. However, the uncertainty in the seawater β relation is ±3% for realistic ocean temperatures and pressures. An uncertainty estimate was not obtained for the fresh water β relation.
To absorb or not to absorb: Control source power output in active noise control systems
Authors: Snyder Scott D. , Tanaka Nobuo
Published: October 2005

This paper addresses the problem of finding a common link between actively attenuating noise in a variety of acoustic environments, such as in free space or in ducts, using vibration or acoustic control sources. It is shown that if acoustic reciprocity holds between each point on the primary source and each point on the control source, then the acoustic power output of the control source under optimal conditions will always be zero, with the converse also true. This concept is demonstrated for systems operating in free space, using both acoustic and vibration control sources, and for systems operating in a semi-infinite duct with a nonrigid termination. The physical meaning of this concept for the employment of vibration control sources, applied directly to a vibrating structure in an effort to attenuate the radiated sound field, is shown.
Propagation of shock waves in elastic solids caused by cavitation microjet impact. I: Theoretical formulation
Authors: Zhong P. , Chuong C. J.
Published: October 2005

To understand the physical process of the impingement of a cavitation microjet and the resultant shock wave propagation in an elastic solid, a theoretical model using geometrical acoustics was developed. Shock waves induced in both the jet head (water) and the solid were analyzed during a tri-supersonic impact configuration when the contact edge between the jet head and the elastic boundary expands faster than the longitudinal wave speed in the solid. Impact pressure at the boundary was solved using continuity conditions along the boundary normal. Reflection and refraction of shock waves from a solid–water interface were also included in the model. With this model, the impact pressure at the solid boundary and the stress, strain as well as velocity discontinuities at the propagating shock fronts were calculated. A comparison with results from previous studies shows that this model provides a more complete and general solution for the jet impact problem.
Optimal estimation of hearing-aid compression parameters
Authors: Kates James M.
Published: October 2005

A new procedure for measuring the attack and release time constants of a hearing-aid compression circuit is presented in this paper. The procedure is based on a mathematical model of the response of a compression system to sudden increments or decrements in the amplitude of a sinusoidal excitation. The parameters of the model, which include the attack and release time constants, are fitted to the measured hearing-aid test-signal response using a minimum mean-squared error criterion. A computer simulation of a compression hearing aid is used to illustrate the behavior of the compression amplifier and to assess the accuracy of the estimated attack and release time constants.
Frequencies of resonance of axisymmetric modes of open prolate spheroidal shells
Authors: Yahner Jack , Burroughs Courtney B.
Published: October 2005

Governing differential equations are derived for the axisymmetric motion of an open prolate spheroidal shell with inner and outer surfaces defined by prolate spheroidal coordinate surfaces. Transverse shear and rotary inertia terms are included in the shell equations. The open end of the shell, defined by a circumferential coordinate line, is assumed clamped. Approximate solutions for the axisymmetric frequencies of resonance of the in-vacuo and fluid-loaded shell are derived using the Galerkin method. For the in-vacuo shell, good agreement with published results for the exact frequencies of resonance of a spherical shell is obtained. Results are presented for the frequencies of resonance of open prolate spheroidal shells as a function of shell eccentricity, mode number, shell thickness, and opening angle, with and without fluid loading.
Variational formulation of acoustic radiation from submerged spheroidal shells
Authors: Chen Pei-Tai , Ginsberg Jerry H.
Published: October 2005

The surface variational principle (SVP) governing acoustic interaction between a vibrating surface and a surrounding fluid is combined with the dynamic equations governing response of a shell of revolution subjected to axisymmetric harmonic excitation. Ritz series representations are used to represent the spatial dependence of the surface pressure and shell displacement components. Two formulations are presented, with the difference being whether an intermediate computation of the in-vacuo modes is performed. The direct approach, in which the Ritz coefficients are determined directly from the coupled formulation, is used to validate the SVP approach for the case of a spherical shell, whose response is known analytically. For the case of a slender spheroidal shell, the direct approach is compared to the results obtained from the modal approach, in which a truncated set of in-vacuo modes forms the basis functions representing displacement. The aspect ratio and shell properties for this evaluation are selected to be in a range in which eigenvalue veering phenomena between two modes are encountered in the absence of fluid loading. The excitation is taken to be a uniform internal pressure having harmonic temporal variation. It is shown that truncations should include the modes involved in the eigenvalue veering process, even when the excitation frequency is sufficiently low to expect modal truncation to be reasonably accurate for predicting in-vacuo response.
Causality analysis of feedforward-controlled systems with broadband inputs
Authors: Burdisso R. A. , Vipperman J. S. , Fuller C. R.
Published: October 2005

In recent years adaptive feedforward control algorithms have been successfully implemented to attenuate the response of systems under persistent disturbances such as single and multiple tones as well as random inputs. System causality is not an issue when the excitation is sinusoidal because of its deterministic nature. However, causality is a very important factor in broadband control. Though significant deterioration in the performance of noncausal control systems have been reported in the literature, analytical tools are virtually nonexistent to predict the behavior of broadband controllers. The main objective of this research is to develop an approach to investigate system causality. A formulation is presented to address the effectiveness of a control configuration as a function of the filter size, delay time, and dynamic properties of the structure. The technique is illustrated in a simple numerical example and the results are also corroborated experimentally.
Vibrational relaxation in (1,1,1) chlorodifluoroethane–argon mixtures at 297 K
Authors: Olson John R. , Amme Robert C. , Brann Douglas B.
Published: October 2005

Molecules that undergo rapid vibration-translation (V-T) relaxation in the pure vapor state may relax more slowly when mixed with inert-gas species to the same pressure. If there remains sufficient vibrational specific heat in such mixtures, then ultrasonic dispersion may be employed over a range of concentrations of the relaxing species in the nonrelaxing medium, and the results linearly extrapolated to 0% additive to infer the much shorter relaxation time for the pure substance. This procedure is demonstrated for (1,1,1) C2H3ClF2 at room temperature (297 K), for which the vibrational relaxation time τ is 8.3 ns, while that for one molecule in otherwise pure argon τAB is 22 ns. These results are used to explore the applicability of the Schwartz–Slawsky–Herzfeld theory under two different scenarios, one in which the torsional mode of the chlorodifluoroethane is responsible for the V-T energy exchange and one in which the bending mode is the exchange mode. The derived ratios for the collision numbers (Z10)AB/(Z10)AA are found to closely match the observed ratios for either scenario if a 7:28 potential function is employed for the molecule.
Electromechanical coupling coefficients of ultrasonic Lamb waves
Authors: Joshi Shrinivas G. , Jin Yu
Published: October 2005

The electromechanical coupling coefficients of fundamental and higher-order ultrasonic Lamb wave modes propagating in a piezoelectric plate have been calculated using two different methods. The first approach calculates the coupling coefficient K from the well-known equation K2=2(Δv/v)=2(v0−vm)/v0, where v0 and vm are the wave velocities on a free and a metallized surface, respectively. The second approach, which involves considerably more calculations, is based on the Green’s function method of analysis. In the case of surface acoustic waves, it has been shown that the two approaches give nearly identical results. It is found that, in most cases, this is also true for Lamb waves. The only exception occurs for the lowest-order symmetric (S0) and antisymmetric (A0) modes, if the ratio h/λ (h=plate thickness, λ=acoustic wavelength) is greater than 1. In this case the Δv/v method gives erroneous results. This occurs because, in this case, the surface metallization causes strong perturbation of the mechanical displacements associated with the waves. In all other cases, the surface metallization produces a weak perturbation of the acoustic wave, and the simple Δv/v method can be used to calculate the coupling coefficient.
Role of the absorption distribution and generalization of exponential reverberation law in chaotic rooms
Authors: Mortessagne Fabrice , Legrand Olivier , Sornette Didier
Published: October 2005

The theoretical validity of the classical law of reverberation in the true geometrical acoustic limit (TGAL) with mirror reflection relies solely on the conditions that almost all rays are chaotic and that absorption is ‘‘sufficiently weak,’’ as demonstrated by Joyce [J. Acoust. Soc. Am. 58, 643 (1975)]. Recently it was shown that ‘‘sufficiently weak’’ may imply unrealistically large reverberation times [J. Acoust. Soc. Am. 88, 865 (1990)]. Here, this negative result is mitigated by showing that an exponential decay law may still hold in the TGAL for realistic absorptions, depending on the spatial distribution of the absorption within the chaotic room (for instance, in the case of uniform absorption on the walls). The dependence of the sound energy decay on the spatial distribution of absorption stems from the role of special ray trajectories which are analyzed. Also demonstrated theoretically and numerically is that the reverberation time is modified at large absorptions due to fluctuations in the number of encounters with the absorbing walls.
Influence of electroacoustic parameters on the performance of reverberation enhancement systems
Authors: Svensson Peter U.
Published: October 2005

The computer simulation of electroacoustic reverberation enhancement systems for variable acoustics is presented. All involved room impulse responses are predicted using the image source model, complemented by a diffuse field extension for the late part. The electronic units included in the reverberation enhancement system are also specified by their impulse responses. The corresponding frequency responses are processed using a matrix formulation which yields the total room impulse response of the hall with the reverberation enhancement system installed. From this, measures which describe the system performance can be calculated. In the simulation study presented, a typical medium-sized hall which seats 450 persons has been modeled and nine different two-channel configurations have been simulated. The current simulation approach proves more flexible than previous methods since also the early part of the total impulse response can be predicted. Transducer directivities and electronic reverberation can be included and it is shown that these, along with the system delay, to a large extent influence the early part of the total impulse response. The risk of feedback is also discussed.
Transient elastic waves in finite layered media: One-dimensional analysis
Authors: El-Raheb Michael
Published: October 2005

Transient waves induced by a trapezoidal pulse are studied for a class of finite periodic elastic media using a modal method. For weakly coupled systems, approximate relations are derived for peak compressive stress and group velocity. Peak stress behind the wave front is proportional to transmissibility: the product of frequency interval of the first propagating zone and time interval of the equivalent rectangular pulse which conserves impulse. Along the stack, stress is attenuated or magnified exponentially depending on transmissibility. Finally, the effect on peak stress of disorder in the stack is investigated.
High-frequency forward scattering in the Arctic
Authors: Sammelmann Gary Steven
Published: October 2005

This article describes a simple ray theoretic model of scattering in the Arctic which couples ray theory to the scattering strength formalism of scattering from a rough surface. This model has one free parameter in it, the root-mean-square (rms) slope of the rough surface. A comparison between model predictions and experimental data is made, where the rms slope is adjusted to fit the data. At short ranges, agreement between theory and experiment is of the order 3 dB. At longer ranges, agreement between theory and experiment deteriorates to 6 dB. This deterioration is thought to be due to the effects of shadowing due to large scale ice features, which are neglected in the present model.
Low-frequency scattering from intermediate bubble plumes: Theory and computational parameter study
Authors: Gragg Robert F. , Wurmser Daniel
Published: October 2005

The acoustic field scattered from a bubble plume near the ocean surface is evaluated. It is assumed that the total field obeys the wave equation below a flat pressure-release air/sea interface, and that the interior of the plume can be represented by an effective sound-speed function. Green’s function techniques are used to recast the problem so that the scattering amplitude, including resonance effects, is expressed in terms of equivalent source distributions that must satisfy a boundary integral equation on the surface of the plume. This equation is solved numerically. A wide range of choice is admitted for the various parameters of the problem. The dependence of the far-field scattering amplitude (or, equivalently, the target strength) on the plume’s depth, shape, and interior sound-speed function is examined in the 50- to 500-Hz band for intermediate plumes (i.e., those with air void fractions between 0.01% and 1% and lifetimes as long as 10 s).
A model/data comparison for low-frequency bottom backscatter
Authors: Mourad Pierre D. , Jackson Darrell R.
Published: October 2005

This article describes a model for bottom backscattering strength applicable over the frequency range 100–1000 Hz. The model includes backscatter due to both a rough water/sediment interface and internal sediment inhomogeneities—i.e., sediment-volume scattering within an upward-refracting sediment. The net result is predictions for bottom backscattering strength that depend on the following: frequency, sound speed of the water near the water/sediment interface, density ratio, sound absorption within the sediment, near-surface sound-speed gradient within the sediment, two interfacial roughness parameters, and a parameter proportional to the scattering cross section of a unit volume of sediment. The sediment sound-speed profile is specified in terms of near-surface values for the sound-speed ratio and gradient. Salient features of the modeled backscatter strength include marked departures from Lambert’s law for sediments with sound speed ratios greater than 1; 1–5-dB oscillations as a function of grazing angle, due to the complex structure of the sound field in the sediment; the dominance of sediment-volume scattering over rough surface scattering for most of the grazing angles, frequencies, and sediment types considered; and, for soft sediments, a decrease by about 8–10 dB in the overall level of backscatter as frequency increases from 100 Hz to almost 1000 Hz.
Interaction of two spherical elastic waves in a nonlinear five-constant medium
Authors: Beresnev Igor A.
Published: October 2005

The interaction of two spherical longitudinal waves produced by noncoincident sources with the generation of a transverse difference-frequency wave is studied theoretically. The equation of motion from five-constant elasticity theory to the second order in the displacement is used as a mathematical model. The general solution for the difference-frequency field outside the wave interaction region is obtained in the form of a scattering integral. An analytical solution for plane intersecting beams is derived as a limit case of small interaction volumes. For the general case, the solution is analyzed numerically, and the effect of the sphericity of interacting waves is compared with the results of plane-wave resonance interaction. In the limit of large interaction volumes, backscattering at the difference frequency is formed. This effect suggests the use of this type of nonlinear interaction for remote sensing of the nonlinear properties of the Earth’s crust.
Ray representation of sound scattering by weakly scattering deformed fluid cylinders: Simple physics and application to zooplankton
Authors: Stanton Timothy K. , Clay Clarence S. , Chu Dezhang
Published: October 2005

Data indicate that certain important types of marine organisms behave acoustically like weakly scattering fluid bodies (i.e., their material properties appear fluidlike and similar to those of the surrounding fluid medium). Use of this boundary condition, along with certain assumptions, allows reduction of what is a very complex scattering problem to a relatively simple, approximate ray-based solution. Because of the diversity of this problem, the formulation is presented in two articles: this first one in which the basic physics of the scattering process is described where the incident sound wave is nearly normally incident upon a single target (i.e., the region in which the scattering amplitude is typically at or near a maximum value for the individual) and the second one [Stanton et al., J. Acoust. Soc. Am. 94, 3463–3472 (1993)] where the formulation is heuristically extended to all angles of incidence and then statistically averaged over a range of angles and target sizes to produce a collective echo involving an aggregation of randomly oriented different sized scatterers. In this article, a simple ray model is employed in the deformed cylinder formulation [Stanton, J. Acoust. Soc. Am. 86, 691–705 (1989)] to describe the scattering by finite length deformed fluid bodies in the general shape of elongated organisms. The work involves single realizations of the length and angle of orientation. Straight and bent finite cylinders and prolate spheroids are treated in separate examples. There is reasonable qualitative comparison between the structure of the data collected by Chu et al. [ICES J. Mar. Sci. 49, 97–106 (1992)] involving two decapod shrimp and this single-target normal-incidence theory. This analysis forms the basis for successful comparison (presented in the companion article) between the extended formulation that is averaged over an ensemble of realizations of length and angle of orientation and scattering data involving aggregations of up to 100’s of animals.
A unique coupled boundary element/finite element method for the elastoacoustic analysis of fluid-filled thin shells
Authors: Jeans R. , Mathews I. C.
Published: October 2005

A coupled boundary element/finite element technique originally developed for the analysis of open thin-shell problems, such as propeller blades, is used in this paper for the analysis of the fluid-filled elastic structures. For open thin-shell problems the question of nonuniqueness does not arise, however, it was thought at the time that such a formulation would prove to be nonunique for the analysis of closed fluid-filled submerged bodies. The work presented in this paper will demonstrate that, for submerged fluid-filled closed elastic bodies, this coupled formulation is unique throughout the entire frequency range. An advantage in implementing the variational form of the acoustic integral operator is that the resulting fluid matrix is symmetric. As such, the fluid/structural coupling is simplified, and the computational efficiency enhanced.
Response to ‘‘Comment on ‘Two-tone suppression of inner hair cell and basilar membrane responses in the guinea pig’ ’’ [J. Acoust. Soc. Am. 94, 3509–3510 (1993)]
Authors: Nuttall A. L. , Dolan D. F.
Published: October 2005

This letter provides additional data concerning the nature of two-tone suppression when an above characteristic frequency (CF) tone suppresses the responses of hair cells (in the basal turn of the cochlea) stimulated by lower than characteristic frequency tones. It is shown that the phase of the ac receptor potential of the below CF probe tone undergoes a phase lag during suppression. This is the opposite direction from that which would occur during attenuation of the probe. These data are consistent with the changes that have been reported [Cheatham and Dallos, J. Acoust. Soc. Am. 94 (1993)] in turns two and three of the guinea pig cochlea. Other additional data are provided showing that the phase change of a probe tone having a frequency higher than CF is a function of whether the high-side supressor is excitatory or nonexcitatory for the hair cell. Nonexcitatory high-side suppression is attenuation-like, whereas the mutual suppression of two (close in frequency) excitatory tones are not like attenuation.
Acoustic source levels associated with the nonlinear interactions of ocean waves
Authors: Kibblewhite A. C. , Wu C. Y.
Published: October 2005

Spectra of wave-induced microseismic noise are calculated as a function of the distance from the center of an active wave region of finite size, to examine the influence of the inhomogeneous component of the pressure field arising from nonlinear wave interactions in a shallow water environment. The contribution of this component is shown to be very dependent on the properties of the bottom structure, especially the rigidity of the top sedimentary layer and the shear-wave velocities of the sublayers. Calculations for a typical six-layered bottom with an overlying unconsolidated sediment in a shallow water environment (100-m water layer) confirms that the inclusion of the inhomogeneous component of the pressure field can raise the total seismic spectral level up to 30–40 dB, as indicated recently by Schmidt and Kuperman [J. Acoust. Soc. Am. 84, 2153–2162 (1988)] in an analysis of ‘‘bottom magnification.’’ When the bottom is composed of a solid half-space, however, this contribution is found to drop to only a few dB. It is also demonstrated that for the multilayered model being discussed the contribution from the inhomogeneous component drops quickly and by as much as 30 dB, when the observation point is moved outside the active region. These results confirm the interpretation of the ULF noise-source levels, reported earlier by Kibblewhite and Ewans [J. Acoust. Soc. Am. 78, 981–994 (1985)] on the basis of onshore microseismic spectra, and show why they are reasonably representative of the wind-dependent ULF noise spectra observed in deep water.
Auditory filter shapes of normal-hearing and hearing-impaired listeners in continuous broadband noisea)
Authors: Leek Marjorie R. , Summers Van
Published: October 2005

Listeners with sensorineural hearing impairment typically exhibit auditory processing deficits such as reduced frequency and/or temporal resolution. Such deficits may represent separate sequela of auditory pathology or may result directly from the sensitivity loss and the requirement to listen at high levels. To assess the impact of increased thresholds on frequency resolution, auditory filter characteristics were determined for hearing-impaired and normal-hearing listeners at 500 and 2000 Hz in the presence of continuous broadband noise meant as a rough simulation of hearing loss. In the fitting procedure, the low-frequency skirt of the derived auditory filter was allowed to vary as a function of signal level, permitting different filter shapes to be estimated at high versus low signal levels. Listeners with moderate hearing losses at 2000 Hz demonstrated near-normal auditory filter shapes for lower signal levels, but increasingly broad and asymmetric filters as signal level was raised. At 500 Hz, where hearing losses were mild, filter bandwidths increased little at the higher signal levels. The presence of broadband noise had essentially no effect on filter shapes of either listener group. The filter shape abnormalities demonstrated by listeners with moderate hearing loss, which were not observed in normal-hearing listeners at the same signal levels, indicate that poor frequency resolution in these patients for high-intensity stimuli does not follow directly from decreased sensitivity, but instead reflects an independent pathology.
Effects of modulation rate and rate of envelope change on modulation discrimination interference
Authors: Shailer Michael J. , Moore Brian C. J.
Published: October 2005

Modulation discrimination interference (MDI) refers to a reduced ability to detect a change in modulation depth of a target carrier frequency in the presence of other modulated carriers with frequencies remote from that of the target. These experiments examined whether the tuning of MDI in the modulation domain depends primarily on the similarity in modulation periodicity of the target and masking sounds or on the similarity in rate of change of envelope of the target and masking sounds. This question was addressed by manipulating the ac component of the modulation waveform of the target and masker along part of a continuum that ranged from a sinusoid at one end to a square wave at the other; the transition time (rise/fall time) of the modulator was 6.25, 12.5, 25, or 50 ms. When the target and masker carriers were modulated at the same rate [10 periods per second (pps)], MDI decreased with decreasing rise/fall time of the target and with increasing rise/fall time of the masker. Maximum MDI did not occur when the rise/fall times of the target and masker were equal, as might be expected if MDI were caused by perceptual grouping of the target and masker. This pattern of results is consistent with the idea that, for a given carrier, shorter rise/fall times lead to greater salience. When the target and masker had the same rise/fall times, MDI was strongly affected by a difference in modulation rate of the target and masker and slightly affected by the common rise/fall time of the target and masker. Taken together, these results indicate that both modulation periodicity and rate of change of envelope influence MDI.
Spectral pattern and the perceptual fusion of harmonics. I. The role of temporal factors
Authors: Roberts Brian , Bailey Peter J.
Published: October 2005

A single even harmonic can be segregated from an odd-harmonic complex more easily than its odd neighbors for a fundamental frequency of 100 or 200 Hz, but not 400 Hz [Roberts and Bregman, J. Acoust. Soc. Am. 90, 3050–3060 (1991)]. It has been proposed that these findings reflect a cross-channel comparison with limited temporal resolution of amplitude-modulation (AM) rates at the outputs of the auditory filterbank. If this ‘‘temporal-pattern’’ hypothesis is correct, then the even–odd difference should be reduced or abolished by a manipulation that degrades information about AM rate, either by minimizing the depth or changing the pattern of AM. This was achieved by changing the phase relations between the components of the complex (experiment 1) and by adding noise to the complex (experiment 2). Subjects were presented with complex tones consisting exclusively of odd harmonics or containing one additional even harmonic. They were required to hear out one of the components and to rate its clarity. The results did not provide support for the temporal-pattern hypothesis. First, the phase manipulation predicted to minimize AM depth did not reduce the even–odd difference. Second, the reduction in the even–odd difference resulting from the addition of noise did not appear to result from a degradation of information about AM rate.
Spectral pattern and the perceptual fusion of harmonics. II. A special status for added components?
Authors: Roberts Brian , Bailey Peter J.
Published: October 2005

A single even-numbered harmonic can be segregated from an odd-harmonic complex more easily than its odd-numbered neighbors, for low fundamentals [Roberts and Bregman, J. Acoust. Soc. Am. 90, 3050–3060 (1991)]. It has been proposed that this effect occurs because the even harmonic is inconsistent with the regular spectral pattern formed by the odd harmonics. However, in this study we evaluate some alternative accounts of the effect. The stimuli were harmonic complex tones for which one of the components was cued by a preceding pure tone. Subjects were required to listen for the cued component and either to rate its clarity (experiments 1 and 3) or to judge its pitch in relation to the preceding tone (experiment 2). It is argued that the weaker fusion of an added even harmonic depends on its status as an added component rather than as an even harmonic (experiment 1), and on its immediate perceptual salience rather than on auditory learning. An even–odd difference was also found when even and odd harmonics were tested in an identical spectral context (experiment 2), and when one of the neighboring odd harmonics was removed (experiment 3). These results are consistent with the proposal that it is easier to segregate a harmonic from a periodic complex tone when it does not form part of the regular pattern of spectral spacing defined by the other harmonics.
Auditory brain-stem response correlates of resistance to noise-induced hearing loss in Mongolian gerbils
Authors: Boettcher Flint A.
Published: October 2005

The auditory brain-stem response (ABR) was recorded from young adult Mongolian gerbils exposed to noise (octave band of noise centered at 4 kHz, 80 dB SPL, 6 h on, 18 h off) for 12 days. Temporary threshold shift (TTS) of 20–50 dB was measured at 4–8 kHz and TTS of 10 dB or less was measured at 1–2 and 16 kHz immediately after the initial exposure. Immediately following the final (12th) exposure, each animal had 10 dB or less threshold shift at all frequencies, demonstrating as much as 40-dB resistance to TTS. Because significant TTS was limited to the high frequencies, the apical portion of the cochlea was left relatively unaffected by the exposure. Amplitudes of waves ii–iii and iv of the ABR were unaffected at low frequencies and reduced at all stimulus levels for 8 kHz on the first day of exposure; the amplitudes recovered to near-baseline levels by the 12th day of exposure. ABR latencies of waves ii and iv were prolonged at low stimulus levels on days one and six of exposure, but recovered to baseline levels by the 12th day of exposure. Because resistance to noise exposure was observed in all subjects and resistance was limited in spectrum, the results suggest that the gerbil is an excellent model for examining mechanisms of resistance to noise-induced hearing loss.
The envelope following response (EFR) in the Mongolian gerbil to sinusoidally amplitude-modulated signals in the presence of simultaneously gated pure tones
Authors: Dolphin William Ford , Mountain David C.
Published: October 2005

The envelope following response (EFR) is an auditory-evoked potential recorded from the scalp which is elicited by long duration, amplitude-modulated stimuli. In this paper, the results of a series of experiments exploring the behavior of the EFR elicited with sinusoidally amplitude modulated (SAM) tones in the presence of simultaneously gated, continuous, pure-tone interfering signals of varying intensity are reported. Probe stimuli consisted of SAM tones with carriers ranging in frequency from 800 Hz–4 kHz, modulated at frequencies between 30–150 Hz. Probe signals were presented at intensities between 50 and 75 dB pSPL. Pure-tone interfering signals consisted of frequencies between 100 Hz and 10 kHz and ranged in intensity from −10 to +20 dB re: the probe. In these experiments a maximum reduction in the response to the probe tone, measured at the probe modulation frequency, appeared as a sharp peak within a narrow frequency band above the frequency of the probe carrier and a broader region of reduced response extending to higher frequencies. This reduction in response was asymmetrical, spreading more to high than to low frequencies. With an increase in the intensity of the interfering signal the maximum reduction of the response increased in a saturating, monotonic fashion with a concomitant broadening of the frequency region affected. The obtained interference response pattern may be attributable to both ‘‘synchrony capture’’ (i.e., capture of the EFR of the system by envelope components arising due to the interaction of probe and interfering signals) and ‘‘synchrony suppression’’ (i.e., a reduction in the synchronized response from neurons excited by the probe in the presence of the added interfering tone). It appears that the EFR to SAM stimuli of low to moderate intensity arose primarily from neuronal populations tuned to frequencies at or above the probe fc. The results of the present study suggest that at low intensity levels SAM signals are indeed relatively frequency specific and warrant further study for audiometric applications.
Acoustic scattering from fluid-filled, concentric, submerged, cylindrical, elastic shells
Authors: Akay Adnan , Sener Sedat , Gaunaurd Guillermo C.
Published: October 2005

The present study addresses the scattering of plane (cw) sound waveforms by concentric, fluid-filled, elastic shells in water from the viewpoint of an impedance-based formulation. For a single fluid-filled shell, this impedance formulation is shown to agree with (the exact form of) the earlier resonance scattering theory (RST) which used elastic potentials and matches various stresses and displacements at the boundaries. The comparison cannot be established for more than one (concentric) shell, since there is no RST formulation for such cases. However, the present formulation is used to generate predictions for double shells with various fillers. A number of conclusions emerge from the present analysis and calculations, particularly for the case of two concentric fluid-filled shells. In this instance, if the filler of the annular region in between the shells is air, then the structural components inside that region do not contribute to the scattered field, and can be safely ignored. For a water-filled annular region, the total backscattering form function (at θ=π) will automatically display the isolated shell resonances, without any need for any ‘‘background’’ subtraction. Furthermore, the total angular form functions, evaluated at resonance, will exhibit the typical shape of rhodonea patterns, again without subtracting any type of background. These cases in which background subtraction is not needed are contrasted with various others in which it is needed, and how resonance isolation is achieved in all cases considered is shown. Many computer generated graphs for single and double shells illustrate all these points.
Behavioral measures of auditory thresholds in developing tree shrews (Tupaia belangeri)
Authors: Zimmermann Elke
Published: October 2005

The development of hearing in tree shrews (Tupaia belangeri) was tested through behavioral measures in the range of 0.3–60 kHz from the first postnatal thresholds detectable through to those of weanlings. The onset of hearing was defined using unconditioned startle responses, while, later on, pinna reflexes and head movements were used as behavioral indicators of sound perception. Startle responses could be evoked from day 16 after birth (DAB) onwards, indicating that the hearing system is capable of transferring airborne sound, although no reactions to tones were recorded at this age. The first unconditioned reactions to tones were found at DAB 18 in the range of 1–5 kHz (range of mother–infant call). Responses were restricted to the range of greatest sensitivity in adults (1–10 kHz). An increase in sensitivity was detected from DAB 18–38. The lowest tested frequency (0.3 kHz) reached adult levels earlier than higher frequencies. No further improvement of auditory thresholds could be observed from DAB 38 (end of nutritional weaning) to DAB 42. Results were related to recent findings on the development of acoustical behavior and of the peripheral and central auditory system of tree shrews and other mammals.
Acoustic scattering by submerged elastic cylindrical shells: Uniform ray asymptotics
Authors: Ho Jin-Meng
Published: October 2005

In a uniform ray acoustic formulation, the pressure field scattered by a submerged thin elastic cylindrical shell is comprised of a specular reflected wave field, a phase-matched leaky wave field, and a reflected–leaky wave interacting field. They correspond to the contribution from a saddle point, the residue from spectral poles, and the effect due to their proximity in the spectral ray integral generating the reflected field. Using plane wave far-field scattering as an example, this paper presents an improved uniform algorithm that expresses the third component in terms of the first and second, which have been developed earlier, plus a complementary error function. In addition, the creeping wave contribution is also considered. Numerical implementation is carried out, showing extensively the scattered field data, in particular, their dependence on frequency as well as on aspect and azimuthal angles; the ray constituents and interacting fields are identified individually, thereby clarifying the relevant wave processes at various parameter regimes. It is observed that the uniform ray scheme improves considerably over simple ray asymptotics, especially at lower frequencies, and that its prediction agrees very well with the exact solution for ka≥3.
Acoustic pulse propagation in elastically inhomogeneous media
Authors: Oberle Robert , Cammarata R. C.
Published: October 2005

The equation of motion for a one-dimensional inhomogeneous medium is derived using the Lagrangian description of a continuous medium. The equations of motion are determined from the Euler–Lagrange equations derived from the Lagrangian density. A general form of the solution is obtained and the specific solution for the special case of a medium whose elastic stiffness changes linearly with distance in the propagation direction is determined. The displacement field is calculated for this case showing the effects of the inhomogeneity on shape and signal velocity of elastic pulses.
Comment on ‘‘Patterns of expressive timing in performances of a Beethoven minuet by nineteen famous pianists’’ [J. Acoust. Soc. Am. 88, 622–641 (1990)]
Authors: Nettheim Nigel
Published: October 2005

Repp [J. Acoust. Soc. Am. 88, 622–641 (1990)] analyzed pianists’ timings with respect to Clynes’ notion of ‘‘composer’s pulse,’’ and to score structure and listeners’ evaluations. This letter discusses the definition and location of the pulse, directing attention to the importance of the nuances in accompaniment figures. Repp may have underestimated the limiting effect of measuring only one performance variable, timing. The standard psychological methods adopted by Repp seem not fully convincing in the present artistic context.
Response to ‘‘Comments on ‘Patterns of expressive timing in performances of a Beethoven minuet by nineteen famous pianists’ ’’ [J. Acoust. Soc. Am. 94, 3001–3003 (1993)]
Authors: Repp Bruno H.
Published: October 2005

In this brief reply to Nettheim’s comments [J. Acoust. Soc. Am. 94, 000–000 (1993)] on the author’s ‘‘Beethoven minuet’’ paper [J. Acoust. Soc. Am. 88, 622–641 (1990)], the following points are addressed: the possible perceptual interdependence of microstructural dimensions, the unsuitability of the music chosen for assessing the ‘‘primary’’ pulse, the relation between composer-specific pulse and composer-specific structure, the notion of ‘‘depth’’ in interpretation, the underlying continuous dimensions of performance quality, and the irrelevance of small deviations in playback speed (if any) to relative performance evaluation.
Broadband matched-field processing
Authors: Brienzo Richard K. , Hodgkiss William S.
Published: October 2005

Acoustic energy in the ocean propagates from a source to an array of sensors via multiple pathways. Conventional time-delay-and-sum beamforming does not utilize energy contained in the multipath arrivals. In this paper, a generalized beamformer is presented which coherently recombines the multipaths to provide enhanced detectability of broadband transients as well as range and depth localization of the source. Modeling of the wave field at the array due to a broadband source is accomplished with a normal mode model using 1.0-Hz increments across the 1- to 100-Hz band. These results are combined to yield the impulse response from a specified source location to each of the array elements. The set of calculated impulse responses is used in the generalized beamformer to coherently recombine energy arriving along multipaths that exist from that source range and depth to the array. The location of a source is determined by examining the beamformer output at a number of candidate range/depth cells; a peak in the output gives the location of the source. Experimental data, consisting of multiple arrivals at a hydrophone array from an explosive source at mid-depth in 2800 m of water, are processed using the generalized beamformer.
Array surveying using matched-field processing
Authors: Tran Jean-Marie Q. D. , Hodgkiss W. S.
Published: October 2005

In this paper, the problem of localizing a vertical line array of sensors is studied in the context of matched-field processing. A broadcasting source is assumed deployed in a known environment at a known location from a vertical line array. Array surveying is discussed and a simple procedure using a correlation measure and a standard multidimensional optimization algorithm is proposed to resolve the array shape. First, this procedure is used on simulated data and convergence is demonstrated. Then, the method is used on data collected at sea in September 1987 with a 900-m-long array with 120 sensors. The derived array sensor positions are found consistent with previous analysis results. The positions found by the optimization procedure have a noisy character which is thought to be due to deviations of the individual array element gain and phase characteristics from their nominal calibrations.
Function-based modeling of binaural processing: Level and time cues
Authors: Dabak Anand G. , Johnson Don H.
Published: October 2005

From theoretical considerations, function-based modeling predicts the input–output characteristics of a neural system intended to perform a signal processing task within a sensory system. The sensory task under study here is the time- and level-based localization of a high-frequency, possibly amplitude-modulated, sound source in the horizontal plane. The stimulus is assumed to be represented by each ear’s primarylike discharge pattern. An optimal system that extracts azimuthal angle from these discharge patterns, which represent acoustic time and level localization cues, has been derived. This system can be described as the maximization of a sum of three subsystems’ outputs. The stimulus cues employed by these systems are interaural level difference for the level-based subsystem, the interaural onset-time difference for the time-based subsystem, and the interaural envelope-phase difference for the phase-based subsystem. The system encompassing all these cues is shown to trade-off the level, time, and envelope-phase cues depending upon the time since stimulus onset, the observation time, and the incident signal’s level. How this system might correspond to known structures in the lower auditory pathway is described.
Ear-canal impedance and reflection coefficient in human infants and adults
Authors: Keefe Douglas H. , Bulen Jay C. , Arehart Kathy Hoberg , Burns Edward M.
Published: October 2005

The ear-canal impedance and reflection coefficient were measured in an adult group and in groups of infants of age 1, 3, 6, 12, and 24 months over frequency range 125–10 700 Hz. The development of the external ear canal and middle ear strongly affect input impedance and reflection coefficient responses, and this development is not yet complete at age 24 months. Contributing factors include growth of the area and length of the ear canal, a resonance in the ear-canal walls of younger infants, and a probable influence of growth of the middle-ear cavities. The middle-ear compliance is lower in infants than adults, and the middle-ear resistance is higher. The power transfer into the middle ear of the infant is much less than into that of the adult. Such differences in power transfer directly influence both behavioral and physiological measurements of hearing. The difficulties of interpretation of neonatal tympanograms are shown to be a consequence of ear-canal wall vibration. Impedance and reflectance measurements in the 2–4-kHz range are recommended as a potentially useful clinical tool for circumventing these difficulties.
Effects of contralateral acoustic stimulation on spontaneous otoacoustic emissionsa)
Authors: Harrison Wendy A. , Burns Edward M.
Published: October 2005

Spontaneous otoacoustic emissions (SOAEs) were measured in the ear canal of adult humans prior to, during, and following presentation of tonal and broadband stimuli to the contralateral ear. Tones were presented at a fixed level at ten frequencies relative to the SOAE. Broadband noise was presented at eight levels, from 6 to 76 dB SPL. Shifts in SOAE frequency and amplitude were observed for some subjects, for some tone conditions. Frequency shifts were always positive, whereas amplitude shifts were variable. No apparent pattern of tuning was seen, such that tones with a particular frequency relationship to the SOAEs induced greater changes in the SOAEs. Systematic changes in frequency and amplitude of SOAEs were observed for increasing level of broadband noise for all subjects. Results are discussed with respect to possible mechanism(s) responsible for the alterations in SOAEs: Transcranial conduction; the olivocochlear system; and/or the middle-ear reflex arc.