bluuebunny/crossref_metadata_2025 huggingface dataset:
Error bounds on ultrasonic scatterer size estimates
Authors: Chaturvedi Pawan , Insana Michael F.
Published: October 2005

Precision errors that occur in estimating the average scatterer size from pulse-echo ultrasound waveforms are examined in detail. The method-independent lower bound on estimation error is found from the Cramér–Rao inequality for comparison with the predicted error for the measurement technique currently used to estimate scatterer sizes in soft biological tissues. The probability density function for the estimate is also derived. From these statistical analyses, strategies for designing experiments that minimize the error are discussed. It is shown that compared with biological variability, measurement errors in scatterer size estimates are relatively large. Consequently, there is reason to continue searching for more efficient estimators. Although the analysis and results are derived for Gaussian correlation models that have been used to study the function and structure of kidneys, generalization to include correlation models for other tissues is straightforward.
The mean pressure and density in a strongly nonlinear plane acoustic wave
Authors: Yano Takeru
Published: October 2005

Exact expressions are presented for a time-averaged pressure and density at a fixed point in a strongly nonlinear plane acoustic wave radiated into an inviscid ideal gas of semi-infinite extent by a harmonic oscillation of an infinite plate. By making use of the exact solution of simple wave, the time averages of pressure and density are obtained up to the time of shock formation, in complete forms involving the hypergeometric functions.
Acoustic microscopy for spherical inclusion characterization
Authors: Maslov K. I. , Kundu T. , Lobkis O. I.
Published: October 2005

In this paper a new nondestructive ultrasonic technique is developed to distinguish small spherical voids from small spherical elastic and rigid inclusions. In many materials, such as light metal casting alloys, ultrasonic scattered echoes from void-type defects and heavy metal inclusions used for strengthening purposes can give the ultrasonic signal of the same order of magnitude. It is shown in this paper how one can extract the phase information of the reflected signal to distinguish the voids from solid inclusions. When phase–frequency curves are extended to the zero frequency, then voids and solid inclusions meet at two distinct points on the phase axis separated by a distance of approximately 180°. Thus voids and solid inclusions can be clearly distinguished. Experimental results are verified by theoretical predictions.
On the radiation pressure on small spheres
Authors: Doinikov Alexander A.
Published: October 2005

It is shown that theoretically, in most cases of interest, the acoustic radiation pressure exerted by plane traveling waves on small rigid and liquid spheres is determined by viscous and heat effects whereas the classical King [Proc. R. Soc. London, Ser. A 147, 212–240 (1934)] and Yosioka and Kawasima [Acustica 5, 167–173 (1955)] results are only negligible corrections.
Comments on ‘‘Overcoming ray chaos’’ [J. Acoust. Soc. Am. 95, 3167–3170 (1994)]
Authors: Brown Michael G. , Tappert Frederick D.
Published: October 2005

The paper ‘‘Overcoming ray chaos’’ [J. Acoust. Soc. Am. 95, 3167–3170 (1994)] by Collins and Kuperman incorrectly suggests that ray chaos can be overcome by a suitable choice of numerical techniques. Chaos, when present, is a property of the ray equations, and not the numerical techniques used to solve these equations.
Response to ‘‘Comments on ‘Overcoming ray chaos’ ’’ [J. Acoust. Soc. Am. 100, 1234–1239 (1996)]
Authors: Collins Michael D. , Kuperman W. A.
Published: October 2005

The comments by Brown and Tappert [J. Acoust. Soc. Am. 100, 1234–1239 (1996)] are discussed. Their claim that the paper [J. Acoust. Soc. Am. 95, 3167–3170 (1994)] contains ‘‘incorrect and/or unsubstantiated statements’’ is shown to be incorrect.
Ultrasonic pulsed beam interaction with a fluid-loaded elastic plate: Experimental validation
Authors: Zeroug Smaine , Stanke Fred E.
Published: October 2005

In this paper, the analytical model developed in the preceding paper [S. Zeroug and F. E. Stanke, ‘‘Ultrasonic pulsed beam interaction with a fluid-loaded elastic plate: Theory,’’ J. Acoust. Soc. Am. 100, xx–xx (1996)] is numerically implemented and experimentally validated for ultrasonic transducer-excited pulsed beams interacting with a fluid-loaded elastic plate. Using flat piston ultrasonic transducers, two modes of operation are considered: (1) a transmission mode using a pair of transducers and (2) a reflection mode at normal incidence with a single transducer (i.e., pulse echo). A first algorithm, based on real-axis integration (RAI) of the original beam integrals, is used to generate reference data in both modes of operation and is validated by comparison with experiments on various plates. A more computationally efficient algorithm, based on the multiply reflected asymptotic-beam (MRAB) approach, and compared with experiments and RAI data, works accurately for signals from thick plates (in terms of the plate compressional wavelength at the signal center frequency). In particular, it validates the higher-order asymptotic expansion for shear waves excited at normal incidence. However, the MRAB algorithm fails for thin plates mainly in the low-frequency range of the signal. The results attained in this study suggest a rule of thumb that scattered signals comprised of resolvable arrivals are amenable to modeling with the MRAB approach.
Numerical model for moderately nonlinear sound propagation in three-dimensional structures
Authors: Botteldooren Dick
Published: October 2005

A three-dimensional numerical model is presented that is capable of handling moderately nonlinear sound propagation. The model is based on a finite-difference time-domain (FDTD) discretization of a set of equations that approximate the Navier–Stokes equations and that include molecular relaxation processes. The mathematical model and numerical discretization focus on compatibility with earlier linear FDTD models. In this way combining both models in a single simulation is trivial and optimum efficiency is obtained for acoustic propagation. A staggered grid is used for the discretization. Nonlinear effects, heat conduction, and damping are treated to a lower order of accuracy. Two examples illustrate the use of the model. The first example is the nonlinear resonance of a finite length duct. Typical waveform steepening and frequency shift, broadening, and skewing of the resonance peak that are also observed in experiments are found. The second example is a tuned reactive muffler installed on a duct. The decrease in insertion loss for high sound pressures is observed. Possibilities for future study are outlined.
Laboratory study of linear and nonlinear elastic pulse propagation in sandstone
Authors: TenCate James A. , Van Den Abeele Koen E. A. , Shankland Thomas J. , Johnson Paul A.
Published: October 2005

Linear and nonlinear elastic wave pulse propagation experiments were performed in sandstone rods, both at ambient conditions and in vacuum. The purpose of these experiments was to obtain a quantitative measure of the extremely large nonlinear response found in microcracked (i.e., micro-inhomogeneous) media like rock. Two rods were used, (1) a 2-m-long, 5-cm-diam rod of Berea sandstone (with embedded detectors) used in previously published experiments and (2) a somewhat smaller 1.8-m-long, 3.8-cm-diam rod. In the earlier experiments, wave scattering from the embedded detectors was a critical problem. In most of the experiments reported here, this problem was avoided by mounting accelerometers directly to the outside surface of the rod. Linear results show out of vacuum attenuations varied from 1.7 Np/m at 15 kHz (Q=10) for the large rod to 0.4 Np/m at 15 kHz (Q=55) for the small rod; attenuations for the small rod in vacuum were much less, typically about 0.15 Np/m at 15 kHz (Q=150). Wave velocities ranged from 1900 to 2600 m/s. The nonlinear results illustrate growth of the second and third harmonics and accompanying decay of the fundamental. These nonlinear results compare well with a numerical model. Although the results here were performed at peak strain amplitudes as low as 5×10−7, they still show the pronounced nonlinearity characteristic of rock, in agreement with static and resonance studies using the same rock type.
Acoustic streaming field structure: The influence of the radiator
Authors: Bradley C. E.
Published: October 2005

In this paper the general structure of acoustically driven flow is considered, with particular emphasis on the acoustic radiator and its influence on the flow. The exact statement of the boundary condition at the face of the acoustic radiator is included in the usual perturbation approach to streaming theory. The result is a mathematical system that incorporates the influence of the radiator in its description of streaming flow. It is found that flow is driven at the face of the radiator by a streaming mechanism that has not been investigated before. This ‘‘boundary-drive’’ mechanism and the other, well-known streaming mechanisms are each characterized in terms of physical origin and the qualitative features of the resultant flow.
A hybrid coupled wave-number integration approach to range-dependent seismoacoustic modeling
Authors: Goh Joo Thiam , Schmidt Henrik
Published: October 2005

Recently, a spectral super-element approach was developed for acoustic modeling in fluid waveguides [H. Schmidt, W. Seong, and J. T. Goh, J. Acoust. Soc. Am. 98, 465–472 (1995)]. The approach uses a hybridization of finite elements, boundary integrals, and wave-number integration to solve the Helmholtz equation in a range-dependent ocean environment. It provides accurate, full two-way solutions to the wave equation, using either a full, global multiple scattering solution technique, or an efficient single-scatter, marching solution. This paper extends that work to mixed fluid-elastic stratifications. SAFARI is used as the basic computational engine for generating the Green’s function in an ocean with arbitrary fluid-elastic stratifications. The hybrid model therefore directly provides the spectral decomposition of the wave field in terms of modal components, head waves as well as seismic interface waves. Extensive numerical experiments have shown that the method gives accurate results particularly in the forward scatter direction. For comparisons, we have used a finite element parabolic equation model, a boundary-element code, as well as the recently developed virtual source algorithm.
The effect of suspended particulate matter on sound attenuation in seawater
Authors: Richards S. D. , Heathershaw A. D. , Thorne P. D.
Published: October 2005

Many shallow-water acoustic applications (e.g., naval mine-hunting sonars, acoustic Doppler current profilers) involve devices operating in the frequency range 50–300 kHz over path lengths up to several hundred meters. At these ranges and frequencies the thermoviscous absorption of sound energy in the boundary layers of suspended particles leads to a significant acoustic attenuation. Although the viscous absorption mechanism is well known, little appears to have been done to quantify its effects over the longer path lengths now of operational interest. Additionally, scattering effects, although dominant at much higher frequencies, contribute to the total acoustic energy loss. Preliminary calculations of the acoustic attenuation due to scattering and viscous absorption by suspended particulates are presented here for particle concentrations typically encountered and at sonar frequencies of interest. This attenuation is compared with calculations of the attenuation due to seawater alone and found to be a significant contribution to the total attenuation, possibly giving an additional attenuation of 3 dB over a total path length of 100 m at 100 kHz for a particle concentration of 0.2 kg m−3. Concentrations of this order or even greater are common in coastal and estuarine waters. The effect of distributions of particle sizes on the acoustic attenuation are also investigated. Plans for future work are briefly described.
Acoustic scattering from a thermally driven buoyant plume
Authors: Oeschger J. , Goodman L.
Published: October 2005

An examination is made of the use of broad bandwidth high-frequency acoustic scattering to infer remotely the spatial structure of the temperature field of a thermally driven buoyant plume. Application of the far-field Born approximation results in a linear relationship between the transfer function of the scattering process, Γ, the ratio of received to transmitted pressure, to the spatial Fourier transform of the temperature field, φ(K), where K=ks−ki is the Bragg wave-number vector. A series of experiments are devised to test this hypothesis. These experiments involve a geometry of scattering in which pairs of sources and receivers are placed on opposite sides and equidistant from the scattering volume, a buoyant plume generated by a small circular heating element at the base of a water tank. It is shown that the far-field approximation assuming incident plane waves breaks down when the scales of temperature variability of the plume are of order the Fresnel radius. These results are discussed for both an unstable and turbulent plume. Conditions for the recovery of the Bragg scattering condition are established.
Matched-field inversion for source location and optimal equivalent bathymetry
Authors: Zakarauskas Pierre , Dosso Stanley E. , Fawcett John A.
Published: October 2005

Matched-field processing (MFP) for source localization can be highly sensitive to mismatch between the true bathymetry and the bathymetry model used to compute the replica fields. This paper presents an efficient algorithm to invert for source location and an optimal representation of the (range-dependent) bathymetry which is applicable whenever the adiabatic normal-mode model applies. In the adiabatic mode formulation, the range dependence of the bathymetry between source and receiver is completely contained in range integrals of the wave numbers. Parametrizing these integrals by a single-pole expansion maps all bathymetries which have an equivalent effect on the propagation into as little as a single parameter, resulting in a tremendous reduction in the dimensionality of the inverse problem. The resulting parameter space can then be searched for the bathymetry parameters which provide the best match with the measured acoustic fields. This search can be carried out very efficiently, and applied to optimize the bathymetry for each grid point of an ambiguity surface. The optimization procedure has the effect of broadening the peaks of the ambiguity surface. This results in a loss in resolution, but allows the use of a coarser search grid.
Viscosity-induced attenuation of longitudinal guided waves in fluid-loaded rods
Authors: Nagy Peter B. , Nayfeh Adnan H.
Published: October 2005

The main goal of this paper is to extend the analytical treatment of longitudinal wave propagation along the fiber direction of multilayered coaxial fibers to immersion in a viscous fluid. The viscous fluid is modeled as a hypothetical isotropic solid having rigidity c44=−iωη, where η denotes the viscosity of the fluid and ω is the angular frequency, i.e., the vorticity mode associated with the viscosity of the fluid is formally described as the shear mode in the hypothetical solid. Among other interesting phenomena, the analytical results revealed the presence of a sharp minimum in the viscosity-induced attenuation of the lowest-order longitudinal mode of thin rods. This minimum occurs at a particular frequency when the otherwise elliptical polarization of the surface vibration becomes linearly polarized in the radial direction. Generally, the experimental results on immersed and fluid-covered wires and fibers showed good agreement with the analytical predictions. In particular, the existence of the theoretically predicted minimum in the attenuation spectrum of the lowest-order longitudinal mode was verified.
Reduced frequency selectivity and the preservation of spectral contrast in noise
Authors: Leek Marjorie R. , Summers Van
Published: October 2005

Reduced frequency selectivity associated with sensorineural hearing loss may pose particular problems for hearing-impaired listeners in noisy environments. In these situations, broader-than-normal auditory filters may affect the perception of speech by reducing the contrast between spectral peaks and valleys in at least two ways. First, the peaks and valleys in the internal representation of the speech spectrum become smeared, resulting in less precise frequency analysis. Second, there may be a reduction in the signal-to-noise ratio (S/N) at the output of each auditory filter. In order to examine the relationship between frequency selectivity and identification of speechlike stimuli in noise, hearing-impaired and normal-hearing listeners were trained to assign vowel labels to four harmonic complexes which differed in the frequency locations of four elevated (‘‘peak’’) harmonics. Peak harmonics were chosen to approximate first- and second-formant frequencies in four English vowels. Listeners were then tested to determine the spectral contrast necessary between peak and background components in order to maintain identification accuracy in the presence of various levels of broadband noise. Results indicated that for these stimuli, normal-hearing listeners required about 1 dB of additional spectral contrast for every doubling of the intensity of noise. The required increase in spectral contrast was generally greater for listeners with broader-than-normal auditory filters at 2000 Hz. This finding suggests indirectly that in the internal representations of speech sounds embedded in noise, the signal-to-noise ratio for listeners with abnormal frequency selectivity is poorer than for listeners with normal frequency selectivity. A poorer-than-normal internal S/N may be one factor underlying the common observation that noise often is more degrading to speech understanding by hearing-impaired listeners than by normal-hearing listeners.
Acoustic normal modes below 4 kHz for a rigid, closed violin-shaped cavity
Authors: Bissinger George
Published: October 2005

Numerical calculations of standing wave patterns ≤4 kHz in a closed (no f-holes), rigid, violin-shaped cavity excited by a movable point source were used to investigate internal resonant pressure mode shapes. Approximate normal mode shapes were extracted by appropriate choice of excitation point and tested for orthogonality. Excellent agreement was found with published experimental mode shapes and frequencies below 2 kHz, and with mode frequencies up to 4 kHz when no mode shapes were available. Calculations performed without the end and corner blocks (interior outline same as exterior) from 0.4–4 kHz showed little sensitivity of mode frequency and shape to this cavity shape change. The frequency f(A1) of the lowest closed cavity mode A1 at ∼490 Hz was observed to decrease by 24 Hz when the arch was reduced to zero (flat top and back plate) with rib height held constant. On the other hand when the rib height was reduced (arch still zero), f(A1) increased, but more slowly. The effects of arch and rib height changes are consistent with experimental data from actual instruments for the A1 mode.
Frequency dependence of acoustic backscatter from 5 to 65 MHz (0.06<ka<4.0) of polystyrene beads in agarose
Authors: Bridal S. Lori , Wallace Kirk D. , Trousil Rebecca L. , Wickline Samuel A. , Miller James G.
Published: October 2005

Attenuation and compensated backscatter from suspensions of random distributions of polystyrene beads in agarose are reported across a broad, continuous range of frequencies including frequencies which are currently of interest in the emerging fields of acoustic backscatter microscopy and intravascular imaging. Data are reported over the range of ka from 0.06 to 4, where k is the magnitude of the ultrasonic wave vector and a is the radius of the beads. The attenuation coefficient exhibits a linear dependence on frequency for ka≪1 and more complex behavior at larger values of ka. The measured frequency dependence of the compensated backscatter was consistent with the frequency dependence of the differential backscatter cross section for a single polystyrene sphere throughout the range of ka investigated.
Biologically motivated adaptive sonar system
Authors: Kuc Roman
Published: October 2005

An active sonar system is described that adaptively changes its configuration in response to the echoes it observes. The system mimics biological sonar systems in that there is a movable center transmitter flanked by two adjustable receivers and the interrogation pulse rate is adaptive. When echoes are received, the sonar rotates to point the transmitter at the echo-producing object to maximize the incident acoustic intensity. The receivers rotate and point toward the object to maximize the echo amplitude and bandwidth and to minimize the echo-producing region. This adaptation in configuration standardizes the location of the object within the beam patterns making object recognition from echo waveforms feasible. A change in elevation of the object produces a systematic attenuation in the high-frequency components in the echoes that may prove useful for elevation determination. The sonar is controlled with three stepper motors that define a discrete-state system that points to a finite number of locations in its field. Microscopic perturbations of the object position at the boundaries between these locations cause macroscopic transitions to occur. Making an analogy with the discrete nature of neurons in biological systems provides a possible explanation of the hyperacuity reported in bat ranging experiments.
CMR and factors influencing grouping: Masker bands overlapping in frequency
Authors: Buss Emily , Richards Virginia M.
Published: October 2005

The experiment described here addressed (a) whether a comodulation masking release (CMR) could be obtained using maskers overlapping in frequency, and (b) whether manipulations known to influence grouping would influence the magnitude of the CMR. Observers detected a tone added to a masker consisting of partially overlapping bands of amplitude-modulated noise. Different portions of the masker were modulated with the same or different modulation patterns. Increasing the number of modulators from one to more than one consistently led to an increase in threshold, but increasing the number from two to four did not. In contrast with previous findings using nonoverlapping masker bands, grouping manipulations did not alter the magnitude of the CMR.
Design and tone in the mechanoacoustic piano. Part III. Piano strings and scale design
Authors: Conklin Harold A.
Published: October 2005

Editorial note: This invited and tutorial article has been published in three parts. The abstract for the series was published in Part I—Piano hammers and tonal effects [J. Acoust. Soc. Am. 99, 3286–3296 (1996)]. The article continued with Part II—Piano structure [J. Acoust. Soc. Am. 100, 695–708 (1996)].
Theory of Scholte, leaky Rayleigh, and lateral wave excitation via the laser-induced thermoelastic effect
Authors: Gusev V. , Desmet C. , Lauriks W. , Glorieux C. , Thoen J.
Published: October 2005

The analysis of the laser-induced thermoelastic excitation of acoustic waves propagating along a plane interface between two elastic media is presented. The general solution for the interface motion is derived. The detailed description of the liquid–solid interface motion caused by the photoexcited leaky Rayleigh, Scholte and lateral wave in the liquid is given both in frequency and time domain. The presented theory predicts that laser-induced thermoelastic stresses in the liquid and the solid can contribute in phase to the excitation of a Scholte wave and that the lateral wave excitation is suppressed when the light penetration depth and Scholte wave penetration depth in the liquid are equal. The obtained analytical solutions provide necessary theoretical background for the optimization of the laser-induced generation of interface waves in experiments.
Modeling variations of Rayleigh wave velocity due to distributions of one-dimensional surface-breaking cracks
Authors: Pecorari Claudio
Published: October 2005

A model describing changes of Rayleigh wave velocity caused by distributions of one-dimensional, surface-breaking cracks is presented. The concept of effective medium and the assumption of noninteracting cracks are used in the model. This approach is developed in the low-frequency limit. A real cracked surface is modeled by a homogeneous, anisotropic layer on top of an isotropic substrate. The substrate’s elastic properties are those of the original isotropic half-space, whereas those of the layer are modified by the presence of the crack distribution. Distributions are considered where parameters such as crack density, crack depth, crack depth distribution, and crack orientation are varied. Variations of surface acoustic wave (SAW) velocity are reported for all these cases. SAW velocity is shown to be most sensitive to changes in crack density and crack depth. Negative variations of Rayleigh wave velocity are predicted to be up to 3% even for distributions of rather shallow cracks. These results show that variations of SAW velocity caused by crack distributions are much larger than those due to other forms of surface damage such as surface roughness or residual stresses.
Influence of the curvature on the dispersion curves of a submerged cylindrical shell
Authors: Metsaveer Jaan , Klauson Aleksander
Published: October 2005

The free vibration of a thin-walled fluid-loaded cylindrical shell is discussed. The Timoshenko–Mindlin-type theory of thin plates and shells that includes the effects of shear deformation and rotatory inertia is used to describe the motion of the structure. A classical approach of the Watson transformation applied to the normal mode solution makes it possible to solve the problem in a series of different circumferential waves. The coordinates of the poles in a complex wave number plane provide the phase velocities and attenuation of different wave field components, and the study of the corresponding dispersion curves helps to classify the circumferential waves. However, it is not always straightforward to associate propagation types in a fluid-loaded shell with those of a ‘‘dry’’ shell, since additional roots appear. In the case of a fluid-loaded aluminum shell, the phase velocity curve that asymptotically approaches the Rayleigh wave velocity for the elastic half-space at high frequencies, is attributed to the A0 Lamb-type wave in a submerged shell. This wave is considerably influenced by the curvature of the structure surface at low frequencies where strong interaction with the Franz waves takes place. As a result of this interaction, the A0 wave characteristics become very close to those of the Franz family waves. The position of the A0 wave dispersion curve between the Franz curves depends on the radius of curvature of the shell.
Shallow-water receptions from the transarctic acoustic propagation experiment
Authors: Pawlowicz Richard , Farmer David , Sotirin Barbara , Ozard Siobhan
Published: October 2005

In April 1994 a long-range, low-frequency acoustic propagation experiment took place in the Arctic to test the feasibility of using acoustic methods to observe large-scale thermal variability. Here the characteristics of the received signals at a vertical hydrophone array and a horizontal geophone array located at the edge of the continental shelf in the Lincoln Sea, about 1 Mm from the source, are discussed with respect to the ‘‘forward’’ problem of understanding and correctly modeling propagation. Both cw (tonal) and tomographic M-sequence transmissions are analyzed. It is found that phase stability is very good, and that phase changes are almost entirely due to source/receiver motions. Travel times are not quite as stable, but are consistent with the phase observations, showing that phase can be used to measure travel time changes very accurately. Modal decomposition of M-sequence transmissions received by the vertical array shows an arrival structure in rough agreement with predictions from a coupled-mode calculation. Predictions using an adiabatic approximation appear to work fairly well for modes 1 and 2, but not for higher-order modes which have significant bottom interaction, implying that accurate knowledge of the bathymetry is important in understanding and modeling the signals. Overall, it appears that the forward problem in the water column is known well enough to make an acoustic monitoring program feasible. The acoustic signals were also sensed by geophones placed on the surface of the ice, but it appears that absolute phase and its spatial coherence across the geophone array (although not time stability at any particular geophone) is greatly degraded by the large inhomogeneities present in older ice.
V(z) measurement of multiple leaky wave velocities for elastic constant determination
Authors: Li Wei , Achenbach Jan D.
Published: October 2005

A multiple leaky acoustic wave method to determine elastic constants from a single V(z) measurement is presented. The V(z) curves which include contributions from different leaky acoustic waves, measured using the line-focus acoustic microscope at 225 MHz, have been compared with theoretical results predicted by a V(z) measurement model. The determination of elastic constants has been achieved numerically by seeking a set of elastic constants that leads to the best fit, in the least square sense, of the theoretical results to the experimental ones. The method has been applied to isotropic materials in bulk, and plate and thin-film configurations. Elastic constants for each of these cases have been determined. The consistency, convergence, sensitivity, and accuracy of the procedure have been investigated.
Local sound field reproduction using digital signal processing
Authors: Kirkeby Ole , Nelson Philip A. , Orduna-Bustamante Felipe , Hamada Hareo
Published: October 2005

This work shows how an acoustic wavefront can be reconstructed locally by using only a few loudspeakers. The loudspeaker inputs are calculated by passing a set of signals recorded by only a few microphones through a matrix of causal digital filters having finite impulse responses. These filters, referred to as the inverse filters, are calculated by inverting (in the least-squares sense) a matrix which contains the electroacoustic transfer functions from the loudspeakers to the microphones. In practice, it is crucial to use a modeling delay and a regularization factor in order to achieve an accurate inversion. The technique is illustrated with an example that shows how well four loudspeakers can reproduce a sound field that has been recorded with three microphones. When the recorded field does not contain energy at frequencies whose acoustical wavelengths are shorter than the distance between adjacent microphones, the original field is reproduced remarkably accurately in the vicinity of the microphones regardless of the positions of the loudspeakers.
Multicomponent acoustic distortion product otoacoustic emission phase in humans. I. General characteristics
Authors: Moulin Annie , Kemp David T.
Published: October 2005

Phase characteristics and latency of 2 f1−f2, 3f1−2 f2, and 2 f2−f1 acoustic distortion product otoacoustic emissions (DPOAEs) have been analyzed in 12 adults with normal hearing. Phase-versus-frequency functions (PFF) have been recorded at each of ten pairs of primary frequencies, by two methods, depending on which one of the primary frequencies f1 or f2 was swept in frequency. Whichever sweep method was used, local phase irregularities were found in the PFF and were shown to be independent of the phase variability due to the measured noise, to be reproducible and frequency specific. Phase irregularities were significantly greater in subjects exhibiting spontaneous otoacoustic emissions. The latency calculation was unaffected by phase irregularities provided that a suitably large range of f2/f1 ratio was used. The DPOAE latencies that were obtained at low ratios of primaries were significantly longer than those obtained at higher ratios. For all DPOAE components and sweep methods used, the latency decreased as frequency increased from 750 Hz to 6 kHz. Substantial intersubject differences were found. They might be due to two main factors: differences in middle ear acoustic properties and in cochlea mechanical characteristics. The influence of pressure in the outer ear canal increased the DPOAE latencies recorded with both the f1 and f2 sweep methods at low frequencies. Men showed significantly longer 2 f2−f1 DPOAE latencies than women, especially at low frequencies, which can be attributed to the difference in length of the cochlea according to gender. Lastly, the latencies measured using the f2 sweep were consistently longer than the latencies obtained using an f1 sweep for lower sideband DPOAEs, but no difference was observed for upper sideband DPOAEs.
Multicomponent acoustic distortion product otoacoustic emission phase in humans. II. Implications for distortion product otoacoustic emissions generation
Authors: Moulin Annie , Kemp David T.
Published: October 2005

Phase characteristics and latency of 2 f1−f2, 3f1−2 f2, and 2 f2−f1 acoustic distortion product otoacoustic emissions (DPOAEs) recorded in normally hearing adults have been described in a companion paper [Moulin and Kemp, ‘‘Multicomponent acoustic distortion product otoacoustic emission phase in humans. I. General characteristics,’’ J. Acoust. Soc. Am. 100, 1617–1639 (1996)]. Phase-versus-frequency functions (PFF) have been recorded using two methods, depending whether f1 or f2 was swept in frequency, defining, respectively, an ‘‘f1 sweep’’ and an ‘‘f2 sweep’’ method. The present study compares 2 f1−f2, 3f1−2 f2, 4f1−3f2, and 2 f2−f1 DPOAEs phase characteristics, and latencies obtained by these two methods. For lower sideband DPOAEs, the f2 sweep gave consistently longer latencies than the f1 sweep method, whereas no difference was obtained for the 2 f2−f1 DPOAE. This suggests that the lower sideband DPOAEs and the 2 f2−f1 DPOAE do not come from the same aspect of the traveling wave. The longer delay obtained with an f2 sweep is suggested to be due to an additional delay added by the proximity of the peak of the f2 traveling wave. The place-fixed and the wave-fixed models of DPOAE generation are discussed, and an ‘‘intermediate’’ model of DPOAE generation is introduced to explain such additional delay and the existence of phase irregularities which were observed in the PFF. The ratio of the latencies obtained by the two sweep methods is frequency dependent and a relation to cochlear frequency selectivity is suggested. Finally, analysis of the differences in latency of the different lower sideband DPOAE components allowed an estimation of the return latency of DPOAEs.
Rapid inhibition in the cochlear nuclear complex of the chinchilla
Authors: Wickesberg Robert E.
Published: October 2005

This study examined responses to pairs of clicks recorded extracellularly from single units in ventral cochlear nuclei (VCN) of ketamine-anesthetized chinchillas. The response to the trailing click was suppressed for interclick intervals of 1 and 2 ms, but little suppression was observed for an interclick interval of 4 ms. To determine whether any suppression originated in the dorsal cochlear nucleus (DCN), responses to click pairs were recorded before and after injecting lidocaine in the deep layer of the DCN. For 19% of the neurons (7/37), the response to the trailing click increased following the injection, which is consistent with lidocaine reducing delayed inhibition from the DCN. Unexpectedly, for 62% of the units (23/37) the response to the initial click decreased after lidocaine administration. Three units (3/37 or 8%) showed a combination of both responses. For 52% of the units with a decreased response (12/23), the reduction occurred only for loud clicks (≥30 dB above threshold), while at intensities 20 dB lower, responses to pairs of clicks were unchanged. No changes in spontaneous rate were observed. Following lidocaine injections, the tuning curves of 7/12 neurons tested had increased thresholds, but only around the characteristic frequency. These results indicate the presence of two rapid inhibitory inputs onto VCN neurons.
Pitch center of stringed instrument vibrato tones
Authors: Brown Judith C. , Vaughn Kathryn V.
Published: October 2005

The determination of the pitch center of frequency-modulated sounds has been the focus of a number of previous studies. The sources have usually been pure tones or synthetic complex sounds with a well-defined spectral composition. These synthetic sounds differ in temporal and spectral properties from the sounds produced by musical instruments; and it is these acoustic sounds which performers are trained to produce and to perceive in order to make intonation choices. Thus samples chosen for this study consist of approximately 1 s of acoustic sounds produced by a virtuoso violist playing the notes D4, C5♯, A5, and G6 with and without vibrato. The sounds without vibrato were then resampled to give frequencies from −15 to +21 cents with respect to the mean of the sound with vibrato. Two-interval two-alternative forced choice (2I2AFC) experiments were carried out comparing the sounds with vibrato to those without vibrato using two sets of musically experienced listeners as subjects. A control set consisting of the comparison of pitch levels of the unmodulated sounds was carried out simultaneously. Results are consistent with the finding that the pitch perceived is that of the mean. The difference limen inferred from the control set was 2.8 cents for the first group and 2.5 cents for the second group with an upper bound on the error of 1 cent.
The role of auditory beats induced by frequency modulation and polyperiodicity in the perception of spectrally embedded complex target sounds
Authors: Marin Cécile M. H. , McAdams Stephen
Published: October 2005

The contribution of auditory beats to the perception of target sounds differing from an interfering background by their frequency modulation (FM) pattern or by a difference in fundamental frequency (F0) was investigated. On each trial, test sounds composed of a single, second-order formant were embedded in harmonic backgrounds and presented in successive intervals. The center frequencies of these ‘‘normal’’ formants differed across intervals. Subjects were to decide which interval contained the test formant with a center frequency matching that of an isolated target formant presented before each test stimulus. Matching thresholds were measured in terms of the width of modulation for FM stimuli or the mistuning of the F0’s of unmodulated test formants relative to that of the background. Beats may have allowed the identification of the spectral region of the target in both experiments. To reduce interactions between test and background components, matching thresholds were measured for ‘‘flat’’ formants composed of two or three equal-amplitude components embedded in a harmonic background in which components corresponding to those of test formants were absent. These measures were repeated with the addition of a pink noise floor. Matching was still possible in all cases, though at higher thresholds than for normal formants. Computer simulations suggested that the modulation depth of envelope fluctuations within auditory channels played a significant role in the matching of target sounds when their components were mixed in the same frequency region with those of an interfering sound, but not when the target and background components were separated by as much as 250 Hz, the F0 of the stimulus.
Sound source elevation and external ear cues influence the discrimination of spectral notches by the big brown bat, Eptesicus fuscus
Authors: Wotton Janine M. , Haresign Tim , Ferragamo Michael J. , Simmons James A.
Published: October 2005

Measurements of external ear transfer functions in the echolocating bat Eptesicus fuscus have revealed a prominent spectral notch that decreases in center frequency (50 to 30–35 kHz) as elevation decreases [Wotton et al., J. Acoust. Soc. Am. 98, 1423–1445 (1995)]. To examine the influence of this notch, four Eptesicus were trained to discriminate between two sets of electronically generated artificial echoes. The negative (unrewarded) stimulus contained a test spectral notch at a specific frequency that varied from 30 to 50 kHz, while the positive (rewarded) stimulus contained no test notch. The vertical position of the loudspeakers delivering these simulated echoes was changed daily. When echoes were returned from an elevation at which the external ear introduced a spectral notch at the same frequency as the test notch, then the discrimination should have been difficult. The bats’ performance conformed to this prediction: All bats discriminated the presence of a 35-kHz notch at all elevations except −10°. As the frequency of the synthesized notch increased, the elevation at which bats could not perform the discrimination also increased. The movement of the bat’s ‘‘blind spot’’ for the test notch of different frequencies followed the movement of the external ear notch at different elevations.
The perceptual structure of pathologic voice quality
Authors: Kreiman Jody , Gerratt Bruce R.
Published: October 2005

Although perceptual assessment is included in most protocols for evaluating pathologic voices, a standard set of valid scales for measuring voice quality has never been established. Standardization is important for theory and for clinical acceptance, and also because validation of objective measures of voice depends on valid perceptual measures. The present study used large sets (n=80) of male and female voices, representing a broad range of diagnoses and vocal severities. Eight experts judged the dissimilarity of each pair of voices, and responses were analyzed using nonmetric individual differences multidimensional scaling. Results indicate that differences between listeners in perceptual strategy are so great that the fundamental assumption of a common perceptual space must be questioned. Because standardization depends on the assumption that listeners are similar, it is concluded that efforts to standardize perceptual labels for voice quality are unlikely to succeed. However, analysis by synthesis may provide an alternate means of modeling quality as a function of both voices and listeners, thus avoiding this problem.
Coherent localization of an unknown cw source
Authors: Frazer L. Neil
Published: October 2005

Let D j =D j (f) be the data spectrum from thej th element of a hydrophone array of any shape, all of whose phones have the same unknown transfer function with unknown gains. ThenD j =B dG j ( m ¯ d ), where B d is the product of the unknown source spectrum and the unknown hydrophone response, G j is the Green’s function for thej th hydrophone location, and m ¯ d is the unknown true value of the vector m ¯ ̄ containing source location and environmental parameters. Similarly, let S j =B sG j ( m ¯ s ) be a candidate synthetic spectrum for comparison with D j ; here B s is a guess at B d and m ¯ s is a candidate parameter vector. Conventional coherent localization searches for an m ¯ s that maximizes the agreement of D j and S j , an agreement clearly dependent on the guess B s . To remove the problem of the unknown source define F ij =D iG j ( m ¯ s ) and search for the m ¯ s that maximizes agreement of F ij with F ji . To see why this works note that F ij =B dG i ( m ¯ d )G j ( m ¯ s ), whereasF ji =B dG j ( m ¯ d )G i ( m ¯ s ). Thus F ij and F ji have the same source function B d , and F ij equals F ji only if m̄ s =m̄ d . Note that knowledge of the source is not required; in particular it need not be compact in time, hence cw data can be used to localize with ≥ two hydrophones. The localizer for hydrophones with equal gains is φ1=|∑ i≠j ξ i ξ j ∑ f ζ fF ij F ji *|2/(∑ i≠j ξ i ξ j ∑ f ζ f F ij F ij *)2, in which optional real ξ i give array shading, and optional real ζ f give spectral shading. A localizer allowing hydrophones to have different unknown gains is φ2=|∑ i≠j ξ i ξ j ∑ f ζ f F ̂ ij F ̂ F̂ ji *|2/(∑ i≠j ξ i ξ j )2, where F̂ ij =F ij / ∑ f ζ f F i j F i j * .
An acoustical design criterion for balcony configuration in auditoria. I. Acoustical characteristics measured under the balcony and the effects on auditory envelopment
Authors: Fujimoto Kazutoshi , Furuya Hiroshi
Published: October 2005

The object of this study is to make clear the relation between the shape of balcony and acoustical properties under the overhang, and to derive a design criterion for balcony configuration in auditoria. On the assumption that a physical change of the sound field caused by building a balcony would be primarily a reduction of the energy of early reflections from upside, directional characteristics of early reflections were measured in auditoria both with and without a balcony, and the subjective effect of reflections arriving from upside on auditory envelopment was psycho- acoustically examined. First, the results of measurement showed that the ratio of the vertical component to total early reflection energy ERV was very small under the overhang. That is a peculiarity of the sound field under the balcony. Next, the results of a series of psychoacoustical experiments showed that auditory envelopment became weaker as ERV decreased when lateral energy fraction was constant. They suggested that the lack of early reflections from the ceiling above the main orchestra causes the peculiarity of directional distribution of early reflections, and consequently disturbs auditory envelopment under the balcony.
Acoustics of mosques: An overview of current design practices in Saudi Arabia
Authors: Khaiyat Sami A. , Elbashir Abdalla
Published: October 2005

This paper discusses the implications of current practices in the design of contemporary mosques in Saudi Arabia on their acoustical performance. Different functions of the mosque are described along with the unique modes of worships reflected in the changing relative speaker to listener positions during prayers. Different postures of a speaker and listeners in the mosque and how they influence the listening conditions are also discussed. The physical characteristics of the mosque, which have been generally retained from the past despite the giant developments and social changes in the country, are introduced and their respective acoustical impacts are evaluated. Acoustical parameters describing the special aural requirements and prevailing listening conditions in the mosque are highlighted. Such parameters include speech intelligibility, loudness, and the uniformity of the sound distribution. In addition, the use of sound reinforcement systems in the mosque is evaluated. Conclusions are drawn on the unique nature of the problem. It follows that the architectural design of the mosque in Saudi Arabia should be governed by the acoustical performance which should be responsive to the special hearing requirements in the space.