bluuebunny/crossref_metadata_2025 huggingface dataset:
The danger of using narrow-band noise maskers to measure ‘‘suppression’’
Authors: Moore Brian C. J. , Glasberg Brian R.
Published: October 2005

These experiments investigated whether perceptual cueing plays a role in the ‘‘unmasking’’ effects which have been observed in forward masking for narrow-band noise maskers and brief signals. The forward masking produced by a 100-Hz-wide noise masker at a level of 60 dB SPL was measured for a 1-kHz sinusoidal signal with a raised-cosine envelope and a duration of 10 ms at the 6-dB-down points, both for the masker alone, and with various components added to the masker (and gated synchronously with the masker). Unmasking was found to occur even for components which were extremely unlikely to produce a significant supression of the masker: these included a 75-dB SPL 4-kHz sinusoid, a 50-dB SPL 1.4-kHz sinusoid, a noise low-pass filtered at 4 kHz with a spectrum level of 0 dB, and a noise low-pass filtered at 4 kHz with a spectrum level of 20 dB presented in the opposite ear to the masker-plus-signal. It is concluded that perceptual cueing can play a significant role in producing unmasking for brief signals following narrow-band noise maskers, and that it is unwise to interpret the unmasking solely in terms of suppression.
On the acoustic power radiated by line forces on elastic beams
Authors: Keltie R. F. , Peng H.
Published: October 2005

The importance of the spatial extent of applied forces in the topic of structural radiation is studied through formulation of the sound power radiated by a line force acting on an infinite elastic beam. The expression for sound power is integrated numerically and the results examined as a function of kL, the acoustic length of the force, and the wavenumber ratio. Below coincidence the power was found to be generally proportional to (kL)−2. Near and at coincidence, sufficiently large force scales have a significant effect on the power produced. In particular, when the length of the force is an integral multiple of the critical wavelength, the coincidence peak is completely suppressed. Above coincidence, minima in the second power occur when the force length is a multiple of the wavelength of the free bending wave. These minimal values of power are shown to be nearly equal to the power radiated far below coincidence. These results are discussed in terms of the coupled structural/acoustic wavenumber response function and the wavenumber spectrum of the applied force. In addition the relative effects of light fluid loading on the radiation at coincidence are presented.
Acoustic impedance of small, circular orifices in thin plates
Authors: Stinson Michael R. , Shaw E. A. G.
Published: October 2005

Measurements of acoustic impedance have been made on a series of small, circular orifices (0.1–0.3 mm radius) in thin plates (0.038 and 0.38 mm thickness). Both real and imaginary components, over the frequency range 0.6–3 kHz, were obtained using an impedance tube technique. The zero frequency limit of resistance was measured with a flow resistance device. Only small amplitude acoustic signals were considered. For the range of orifice radii and frequencies selected the boundary layer thickness is comparable to the radius, and the usual high-frequency expressions for orifice impedance do not apply. Within the limits of experimental error (approximately 12% for resistance and 6% for reactance) the measured values are in reasonable agreement with Thurston’s general but approximate theory [G. B. Thurston, J. Acoust. Soc. Am. 24, 653–656 (1952)]. The measurements support the simple idea that both real and imaginary components of orifice impedance can be calculated assuming an effective total end correction 16a/3π, where a is the orifice radius.
Nonlinear sound waves from a uniformly moving point source
Authors: Enflo B. O.
Published: October 2005

Nonlinear sound waves from a uniformly moving source with dimensions smaller than the wavelength of the emitted sound are investigated. They are described by spherical Burgers’ equations with parameters depending on the source velocity V and the direction angle θ from the source to the point of observation. It is seen that for certain V and θ values, both for V less than and greater than the sound velocity in the medium, shock waves occur, which do not occur in nonlinear waves from a fixed sound source.
Bubble interaction effects on waves in bubbly liquids
Authors: Rubinstein Jacob
Published: October 2005

We derive effective equations for wave propagation in bubbly liquids which include bubbles interactions effect. We homogenize both the linear and the nonlinear versions of the microscopic equations by two methods. The interaction between the pressure fields is found to increase the speed of sound relative to the Foldy approximation.
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Authors: Dooling Robert J. , Searcy Margaret H.
Published: October 2005

Avoidance conditioning and a modified method of limits psychophysical procedure were used to study temporal integration of tone and noise signals in the budgerigar (Melopsittacus undulatus). Integration of both tone and noise signals can be described by a negative exponential function with a time constant of about 200 ms. At very short durations there were differences in the integration of tone and noise signals. These data are similar to those reported for a number of other vertebrates, including man. Thresholds for two complex natural vocalizations of the budgerigar are similar to those of pure tones of equivalent duration.
Development of a method of determining the transverse wave structure in a rigid wall axisymmetric duct
Authors: Pasqualini J. P. , Ville J. M. , Belleval J. F. de
Published: October 2005

In order to decompose an acoustic field in a circular duct into radial modes, a method based upon properties and calculation of Lommel’s integral is developed. To validate this method, results of amplitude and phase measurements of radial modes in a constant cross-section circular duct with hard walls are compared with results indirectly obtained by an experimental method of modal decomposition based on an axial measurement of the pressure. Finally, as an illustration, this technique is applied to the determination of pressure reflection coefficients of an unflanged duct.
Transverse vibrations of composite piezoelectric polymer plates
Authors: Ricketts Donald
Published: October 2005

Free transverse vibrations of the multilayered rectangular plate are considered. The composite plate consists of 2n orthotropic layers symmetrically located about the midplane, where the central (n and n+1) layers are piezoelectric polymer. Using the Rayleigh method, closed formulas are obtained for the frequencies of flexural vibration. A generalized frequency expression is presented in terms of definite integrals containing the characteristic functions. Formulas for evaluating these integrals for common types of boundary conditions are available in the literature. In particular, an expression is derived for the resonance frequencies of the completely free composite piezoelectric polymer plate.
Conference microphone with adjustable directivity
Authors: Flanagan J. L. , Kubli R. A.
Published: October 2005

A design technique is described in which a line array microphone is provided adjustable spatial directivity suitable to a variety of teleconference applications. The directivity of the system is controlled by acoustic insert elements, selected for the spatial coverage desired. By virtue of a modified end-fire directivity pattern, the array can be located above head level and out of line of sight of the conferees. The design technique utilizes acoustic summation and acoustic low-pass filtering to prevent spatial aliasing. Only a single inexpensive electret element is required for the transducer. A prototype model is fabricated and experimental measurements, made under free-field conditions, are shown to compare satisfactorily with calculated theoretical responses.
Some representations of the integrals of Cron and Sherman for surface-generated ocean noise
Authors: Bordelon Derrill J.
Published: October 2005

Two integrals of Cron and Sherman which arise in modeling of ocean-generated surface noise are given several representations, the most notable of which is obtained from the Laplace transformation of a mild generalization of the given integrals. It is also found that the complex sum, with weights 1 and i, of the integrals reduces to a sum of simpler integrals plus an expression which is representable as a multiple partial derivative of a spherical Hankel function of the first kind, with respect to the normalized vertically projected baseline length of the two relevant sensors. This latter expression is the homolog for the correlation function, of the pressure field of a distant vertical axial multipole of order m being proportional to the m-fold derivative, in a vertical direction, of the Green’s function of a monopole, which is proportional to a spherical Hankel function of the first kind of order zero.
Speed of sound in saturated pure water
Authors: Chávez Martín , Sosa Victor , Tsumura Ricardo
Published: October 2005

The speed of sound in saturated pure water has been measured between 273.16 and 534.69 K at 7.5 MHz using the pulse-echo-overlap method. An equation was fitted to our data within the experimental uncertainties of 0.05%. This equation predicts the values of speed of sound over the whole vapor pressure curve with an assigned zero value at the critical point. Our data were combined with available density data to obtain the isentropic compressibilities.
Applicability of the Biot theory. I. Low-porosity materials
Authors: Ogushwitz P. R.
Published: October 2005

The Biot theory of wave propagation in porous, saturated materials contains 13 parameters. We discuss empirical and theoretical ways to predict values of these parameters for natural materials. The self-consistent theory of composites is used to predict the elastic moduli of the skeletal frame assuming that the inclusions (pore fluid, sediment grains) are needle-shaped at low concentrations. The Biot theory is then used to predict compressional and shear wave speeds in consolidated materials. In a man-made material (porous sintered glass), the predictions agree with experimental data to within 3% (experimental uncertainty is also 3%); these samples were distilled-water-saturated. The predictions agree with data to within 1% for Berea sandstone, and to within 5% for Bedford limestone; all of these samples were brine-saturated. The predictions agree with data to within 8% for distilled-water-saturated Bedford limestone. In the natural sedimentary rocks, the experimental uncertainty in measured wave speeds is estimated at 5%, and the comparisons apply at high effective pressures (>0.3 kbar), where the experimentally determined wave speeds approach ‘‘limiting velocities.’’ In distilled-water-saturated Massilon sandstone, predicted shear wave speeds are about 25% to 35% higher than measured speeds; this may indicate a reduction of the frame shear modulus due to interaction of the pore fluid with the minerals of the rock.
High-frequency acoustic variability in the Arctic
Authors: Schulkin M. , Garrison G. R. , Wen T.
Published: October 2005

Fluctuations in acoustic intensity have been studied for two locations in the Arctic—the Chukchi Sea (1974) and the Kane Basin (1979)—using the same measurement and analysis techniques. A five-frequency transducer covering the range 10–75 kHz was moved continuously in the vertical direction from 10–70 m. The results were used to determine the vertical correlation length and the coefficient of variation (rms variance) for the intensity at the five frequencies simultaneously. Conductivity and temperature versus depth were measured continuously before and after each set of acoustic runs. These profiles were used to construct sound ray diagrams and to compute the refractive index variance. For direct-path propagation in both locations, it was found that when the acoustic intensity variance at low spatial wavenumbers is filtered out, remaining variance depends on the first power of the frequency and approximately the square of the range. This internal-wavelike behavior is supported by additional evidence. The vertical correlation lengths observed for the direct-path intensity indicate that the scattering features have lifetimes longer than a few seconds and less than a few minutes. The study suggests that the scattering structures are related to anisotropic eddies that tend toward isotropy as they cascade to smaller sizes. Plots of a strength parameter versus a diffraction parameter show that after deterministic variations are removed from the measurements, the remaining variations lie in the unsaturated direct-path region.
Assessment of community response to impulsive noise
Authors: Schomer Paul D.
Published: October 2005

The U.S. Army Construction Engineering Research Laboratory has completed community attitudinal surveys at two major Army installations. The main purpose of these surveys was to better understand community response to the impulsive noise generated by large Army weapons such as tanks, artillery, or demolition. The results show that an energy type of model such as the C-weighted day/night average sound level (CDNL) is the best available descriptor for community response for these types of impulsive sound. Growth in annoyance to all noises increases monotonically with both sound amplitude and frequency of occurrence. This descriptor should incorporate a nighttime adjustment on the order of 10 decibels (dB). The exact function for relating the percentage of a community highly annoyed to CDNL remains in question. It appears that the present National Academy of Science Committee on Hearing, Bioacoustics and Biomechanics (CHABA) recommendation may underestimate actual annoyance, and that the functional relation between annoyance and CDNL should be shifted by 3–4 dB. However, more research on (a) the percentage of a community highly annoyed versus CDNL and (b) the existence and value of community rise- and decay-time constants is required to clarify this issue.
Sound fields near exterior building surfaces
Authors: Quirt J. D.
Published: October 2005

Measurement of sound transmission through a building facade requires determination of the incident sound power. Interpretation of sound pressure level measurements near a facade is, however, complicated by interference between the incident sound waves and those reflected from the facade. Experimental data and a simple mathematical model are used to examine systematic effects associated with reflections from a large flat facade and, subsequently, to investigate deviations from this simple situation. Although the original motivation for the work was the investigation of problems pertinent to measurements of facade sound transmission, many of the results are relevant for other applications involving measurement of noise near a highly reflective surface.
Specification of the acoustical input to the ear at high frequencies
Authors: Khanna S. M. , Stinson Michael R.
Published: October 2005

The sound fields that arise in the auditory canals of cats have been examined both experimentally and theoretically. Of particular interest was the spatial variation of sound pressure near the eardrum, where reference probes are typically located. Using a computer controlled data acquisition system, sound pressure was measured between 100 Hz and 33 kHz for constant driver input at 14 different locations in the ear canal of a cat, and the standing wave patterns formed. The shape of the patterns could be predicted quite well above 12 kHz using a theory that requires specification of only the geometry of the ear canal. This theory, an extension of the one-dimensional horn equation, applies to three-dimensional, rigid-walled tubes that have both variable cross section and curvature along their lengths. Large variations of sound pressure along the ear canal and over the surface of the eardrum are found above about 10 kHz. As a consequence it is not possible to define the acoustical input to the ear from sound pressure level measured at any single location. Even in comparative experiments, in which only the constancy of the acoustical input is important, any uncertainty in reference probe location would lead to an uncertainty in sound pressure level when different sets of measurements are compared. This error, calculated for various probe locations and frequencies, is especially large when the probe is near a minimum of the sound field. Spatial variations in pressure can also introduce anomalous features into the measured frequency response of other auditory quantities when eardrum sound pressure is used as a reference. This is illustrated with measurements of the round window cochlear microphonic.
Extension of a temporal model of frequency discrimination: Intensity effects in normal and hearing-impaired listeners
Authors: Wakefield Gregory H. , Nelson David A.
Published: October 2005

The effects of intensity on the difference limen for frequency (DLF) in normal-hearing and in hearing-impaired listeners are incorporated into the temporal model of frequency discrimination proposed by Goldstein and Srulovicz [Psychophysics and Physiology of Hearing, edited by E. F. Evans and J. P. Wilson (Academic, New York, 1977)]. A simple extension of the temporal mode, which includes the dependence of phase locking on intensity, is sufficient to predict the effects of intensity on the DLF in normal-hearing listeners. To account for elevated DLFs in hearing-impaired listeners the impairment is modeled as a reduction in the synchrony of the discharge from VIIIth-nerve fibers that innervate the region of hearing loss. Constraints on the optimal processor and the validity of the temporal model at high frequencies are discussed.
Detection of temporal gaps in bandlimited noise: Effects of variations in bandwidth and signal-to-masker ratio
Authors: Shailer Michael J. , Moore Brian C. J.
Published: October 2005

Thresholds were measured for the detection of a temporal gap in a bandlimited noise signal presented in a continuous wideband masker, using an adaptive forced-choice procedure. In experiment I the ratio of signal spectrum level to masker spectrum level (the SMR) was fixed at 10 dB and gap thresholds were measured as a function of signal bandwidth at three center frequencies: 0.4, 1.0, and 6.5 kHz. Performance improved with increasing bandwidth and increasing center frequency. For a subset of conditions, gap threshold was also measured as bandwidth was varied keeping the upper cutoff frequency of the signal constant. In this case the variation of gap threshold with bandwidth was more gradual, suggesting that subjects detect the gap using primarily the highest frequency region available in the signal. At low center frequencies, however, subjects may have a limited ability to combine information in different frequency regions. In experiment II gap thresholds were measured as a function of SMR for several signal bandwidths at each of three center frequencies: 0.5, 1.0, and 6.5 kHz. Gap thresholds improved with increasing SMR, but the improvement was minimal for SMRs greater than 12–15 dB. The results are used to evaluate the relative importance of factors influencing gap threshold.
Identification of known voices as a function of familiarity and narrow-band coding
Authors: Schmidt-Nielsen A. , Stern Karen R.
Published: October 2005

Tape recordings of 24 speakers conversing over an unprocessed channel and over an LPC voice processing system were subjected to listening tests. The listeners were 24 co-workers who attempted to identify each speaker from a group of about 40 people working in the same branch. Prior to the recognition test, each of the listeners also rated his or her familiarity with each of the speakers and the distinctiveness of each speaker’s voice. There was some loss in voice recognition over LPC, but the recognition accuracy was still quite high (69% vs 88% for unprocessed voices), suggesting that frequently voiced concerns about speaker recognition over narrow-band voice communication systems may not be justified. Talker familiarity was significantly correlated with correct identifications. There was no significant correlation between the rated distinctiveness of the speaker and correct identifications. However, familiarity and distinctiveness ratings were highly correlated. This suggests that people consider a familiar voice to be distinctive regardless of whatever characteristics might make that particular voice stand out in a crowd.
Spectral analysis of echoes for backscattering coefficient measurement
Authors: Ueda Mitsuhiro , Ozawa Yasuhiko
Published: October 2005

This paper describes spectral analyses of echoes scattered by a random medium and a plane reflector by using mathematical expressions of echoes which have been proposed by us before [M. Ueda and H. Ichikawa, J. Acoust. Soc. Am. 70, 1768–1775 (1981): 75, 1012 (1984)]. It becomes possible to express the spectrum of echoes scattered by the random medium in terms of a backscattering coefficient of the random medium and a velocity potential of an ultrasonic transducer. The expressions hold for any sound field if a correlation length of the random medium is much smaller than a beamwidth and a radius of the transducer. Then the spectrum of the echo scattered by the plane reflector is expressed in terms of a directivity of the transducer. By using a ratio of the two spectrums an expression which gives the backscattering coefficient of the random medium is formulated. It works in a farfield of a flat circular transducer and at a focal plane of a concave one. It is shown that our formula contains those cases which have been proposed so far as the extreme cases of the conditions. Finally, the backscattering coefficients of sponges are measured with several transducers. The results show that our formula gives the coefficients regardless of the transducer geometry.
Comparison of the T-matrix and Helmholtz integral equation methods for wave scattering calculations
Authors: Tobocman W.
Published: October 2005

Calculations of the scattering of acoustic waves by rigid prolate spheroids of various aspect ratios were performed with both the T-matrix method (TMM) and the Helmholtz integral equation method (HIEM) on the same computer to compare the numerical stability of the two methods. For spherical targets the TMM converged more rapidly than the HIEM, but with increasing aspect ratio the rate of convergence of the TMM deteriorated rapidly while that of the HIEM was only slightly reduced. Moreover, roundoff error quickly became a serious problem for the TMM with increasing aspect ratio while for the HIEM it posed no problem at all in the cases considered. The numerical difficulties of the TMM were exacerbated by the fact that the matrices which had to be inverted became increasingly more ill conditioned as the number of partial waves was increased. For the HIEM, on the other hand, the matrices to be inverted became increasingly better-conditioned as their dimension increased with the order of the calculation.
A slow-waveguide filter as an acoustic interference controlling device
Authors: Amram Maurice , Chvojka Vick J.
Published: October 2005

Using the fact that low-frequency sound waves are diffracted by any kind of obstacle, a ‘‘sound velocity reducer’’ waveguide has been designed so as to create a 180° phase lag between the diffracted part of the incident noise and that transmitted through the duct of the guide. Further, this waveguide, being a low-pass filter, insures that the acoustic pressure amplitudes diffracted and transmitted are of the same order of magnitude. For a low-frequency band of noise, this results in the formation of coherent dipole line sources and, thus, of destructive interferences, at a distance from the acoustically transparent obstacle. The goal of this paper is to show how we can calculate this phase lag and the relative amplitudes of the components, and how they compare to the actual measurements. The results for the model investigated show good agreement between calculation and measurement, within the precision expected.
Sensitivity of total field and array performance to profile-model selection in the deep ocean
Authors: Bilazarian P. , Siegmann W. L. , Jacobson M. J.
Published: October 2005

The sensitivity of total-field receptions to sound-speed profile choice is analyzed using ray theory. The profiles are depth dependent, and may be used to describe a deep-ocean sound channel. A variety of locations of a fixed source and receiver, separated by less than about 50 km, is considered. Given a specified profile and a second, simpler profile constructed by procedures previously described [J. Acoust. Soc. Am. 75, 112–124 (1984)], it is demonstrated that the acoustic fields associated with the profiles are negligibly different. Approximations for total-field phase and amplitude differences are presented, which facilitate the determination of those ranges where the total fields match closely. In addition, the sensitivity of performance measures for horizontal linear receiving arrays to profile selection is studied. Expressions for normalized power pattern are developed which incorporate certain nonplane-wave effects associated with an assumed dominant ray arrival. Conditions are presented for which a simpler profile may replace a specified profile and still maintain nearly equivalent array performance.
Path-integral treatment of acoustic mutual coherence functions for rays in a sound channel
Authors: Dashen Roger , Flatté Stanley M. , Reynolds Stephen A.
Published: October 2005

The mutual coherence function (MCF) of the acoustic wavefunction from a point source is derived by the path-integral technique for transmission in the presence of a sound channel. Separations in time, transverse horizontal position, vertical position, and acoustic frequency are treated. Approximate coherence times, lengths, and bandwidths due to internal-wave fluctuations are derived. The MCF of frequency is explicitly evaluated for fluctuations due to internal waves. The shape of an ensemble-averaged pulse is derived from the MCF of frequency.
AFAR measurements of acoustic mutual coherence functions of time and frequency
Authors: Reynolds Stephen A. , Flatté Stanley M. , Dashen Roger , Buehler Barry , Maciejewski Pat
Published: October 2005

A joint acoustic–oceanographic experiment was performed near the Azores in 1975. Frequencies from 400–4670 Hz were transmitted over a 35-km wholly refracted path. In addition, a separate data set was gathered over a 3-km path in 1973. Measurements of the mutual coherence function of time and frequency, and measurements of the acoustic phase structure function are presented and compared with predictions of fluctuations due to internal waves.
A stochastic parabolic wave equation and field-moment equations for random media having spatial variation of mean refractive index
Authors: Hill R. J.
Published: October 2005

The wave equation for propagation through random inhomogeneities is expressed in a special coordinate system which follows the ray path of the deterministic wave that would propagate in the absence of randomness. The ratio of the full wave field in the presence of random inhomogeneities to the determinstic wave field is shown to satisfy the parabolic wave equation, with acoustic wavelength depending on position along the ray. This approximation requires that the local sound speed be only slightly perturbed from its local deterministic value, although it may be very different from the sound speed at a distant point on the deterministic ray. No matter how tortuous the path of the deterministic field, this parabolic equation holds provided that the angles between the rays of the full and determinstic fields are small. The equations for moments of the field (mean field, mutual coherence function, and fourth moment) have a form very similar to the case of uniform background.
A numerical method for bottom interacting ocean acoustic normal modes
Authors: Porter Michael B. , Reiss Edward L.
Published: October 2005

In this paper we present a finite-difference method to numerically determine the normal modes for the sound propagation in a stratified ocean resting on a stratified elastic bottom. The compound matrix method is used for computing an impedance condition at the ocean–elastic bottom interface. The impedance condition is then incorporated as a boundary condition into the finite difference equations in the ocean, yielding an algebraic eigenvalue problem. For each fixed mesh size this eigenvalue problem is solved by a combination of efficient numerical methods. The Richardson mesh extrapolation procedure is then used to substantially increase the accuracy of the computation. Two applications are given to demonstrate the speed, accuracy, and efficiency of the method.
Mean-flow effects on the low-wavenumber wall-pressure spectrum of a turbulent boundary layer over a compliant surface
Authors: Hariri H. Haj , Akylas T. R.
Published: October 2005

An analytical study is made of mean-flow effects on the low-wavenumber wall-pressure spectrum of a turbulent boundary layer over a plane flexible surface, in the small-Mach-number limit. The boundary-layer mean flow is modeled by a continuous velocity profile and an analytical expression for the wall-pressure fluctuations is derived on the basis of Lighthill’s acoustic analogy. The appropriate Green function, which incorporates the influence of the boundary-layer mean flow and the surface properties, is calculated in the low-wavenumber regime, using the method of matched asymptotic expansions. It is shown that the effect of the mean flow on the spectrum singularities is identical to that of a uniform-velocity profile. The case of a turbulent boundary layer over a bending plate is discussed.
Effect of coiling in a cochlear model
Authors: Steele Charles R. , Zais Jeffrey G.
Published: October 2005

Transformation of the three-dimensional equations of fluid motion into cylindrical coordinates allowed analysis of a coiled cochlear model by the WKB technique. The model includes a single transverse mode of basilar membrane deflection and inviscid fluid. The results calculated using realistic parameters for the guinea pig show no significant difference in the basilar membrane amplitude and phase between the straight and coiled models. Some differences exist in the fluid pressure found in the scala. The conclusion is that the macromechanical response is not significantly affected by coiling.
Relative dominance of individual partials in determining the pitch of complex tones
Authors: Moore Brian C. J. , Glasberg Brian R. , Peters Robert W.
Published: October 2005

These experiments were conducted to determine the dominance of each partial in determining the residue pitch of a complex tone. Subjects were required to make pitch matches to a complex tone which had one partial slightly mistuned from its ‘‘correct’’ harmonic value. The shift in residue pitch was measured as a function of the frequency shift of the harmonic, for each harmonic in turn. For mistunings up to ±2%–3% the shift in residue pitch was approximately a linear function of the shift in the harmonic, but for greater mistunings the shift in residue pitch was reduced. The degree to which a given harmonic can influence residue pitch gives a measure of the dominance of that harmonic. The dominant harmonics were always contained within the lowest six harmonics (for fundamental frequencies of 100, 200, and 400 Hz), but there were marked individual differences in the exact distribution of dominance across harmonics. The level of a harmonic relative to adjacent harmonics can have a significant effect on its dominance. The implications of the results for theories of pitch perception are discussed.
Absolute identification of electric pulse rates and electrode positions by cochlear implant patients
Authors: Tong Y. C. , Clark G. M.
Published: October 2005

In a single interval task, multichannel cochlear implant patients were asked to identify the members of a set of seven electric stimuli differing in electric pulse rate or electrode position. The perceptual sensitivity index (d′) between successive stimuli in a stimulus set was calculated from the confusions among the seven stimuli. The results showed that the pulse rate above which the identification task became difficult varied from 200 to 600 pps from patient to patient. For the identification of the positions of seven bipolar electrode pairs, d′ measures for stimulus sets differing in spatial separation or spatial extent were compared. Spatial separation is defined as the fixed distance between the two basal (or apical) electrodes of two successive bipolar electrode pairs in a stimulus set, while spatial extent is defined as the fixed distance between the apical and basal electrodes of each bipolar electrode pair in a stimulus set. The results showed that perceptual performance improved in an orderly way with spatial separation, but was not significantly affected by spatial extent.
Dynamics of porous saturated media, checking of the generalized law of Darcy
Authors: Auriault Jean-Louis , Borne Lionel , Chambon René
Published: October 2005

The homogenization process applied to fine periodic deformable saturated porous medium under dynamic solicitations leads to the macroscopic description. This method enables us to perform a complete calculation of the effective parameters. The main fact is that the formulation so obtained—similar to Biot’s results—exhibits a generalized example of Darcy’s law which contains all the dynamic couplings between the two phases. After recalling the main facts of the subject this work presents some properties of the generalized Darcy coefficient and an experimental checking. An agreement between experimental and numerical results using the homogenization process is obtained.
Elastic moduli of two-dimensional composite continua with elliptical inclusions
Authors: Thorpe M. F. , Sen P. N.
Published: October 2005

The elastic field around an elliptical inclusion in two dimensions is obtained. This result is then used to compute the effective moduli of a composite medium containing many randomly positioned and oriented elliptical objects. Two different self-consistent methods are described and the special cases of voids and rigid reinforcement are considered in detail. The asymmetric self-consistent method shows that the Young’s modulus E goes to zero as E=E1(p−pc)/(1−pc), where 1−p is the concentration of the voids and subscript one denotes the void free material. The Poisson ratio σ is also linear in p and goes to a value σc at pc that is independent of the initial value of Poisson’s ratio σ1. Unlike the corresponding three-dimensional case, the two elastic moduli decouple in this special case. The corresponding elastic threshold is pc=[1+ab/(a2+b2)], where a and b are the major semiaxes. The symmetric self-consistent method yields a different pc =2[1+(2(a+b)2/(a2+b1))1/2]−1 and a different concentration dependence of the effective moduli. Both methods give the same result for circular inclusions and both methods give pc+σc=1 for all aspect ratios. Similar results are presented for the case of rigid reinforcements.
Temporal interactions between pure tones and amplitude-modulated noise
Authors: Wakefield Gregory H. , Viemeister Neal F.
Published: October 2005

An auditory interaction between the temporal fine structure of a low-frequency tone and the envelope of a high-frequency waveform was observed at very large frequency separations. Thresholds for detection of sinusoidal amplitude modulation of a high-frequency, narrow-band noise were measured as a function of the relative phase between the modulator and a pure tone with the same frequency as the modulator. These ‘‘phase functions’’ were determined at various intensities of the noise and tone for three different modulation frequencies. In general, the phase functions show that low-frequency stimulation has a cyclic effect on the sensitivity to amplitude modulation; over a limited range of relative phases, the modulation threshold is lower than that measured without low-frequency stimulation whereas over a broader range of relative phases, the modulation threshold is much higher. The difference between minimum and maximum modulation thresholds was observed to be as great as 23 dB. Despite this substantial degree of temporal interaction, little, if any, masking by the low-frequency tone of the high-frequency noise was observed.
Pressure measurements during speech production using semiconductor miniature pressure transducers: Impact on models for speech production
Authors: Cranen Bert , Boves Louis
Published: October 2005

It appears that temperature instabilities are a major obstacle hindering the use of semiconductor strain gauge pressure transducers in speech research, especially when absolute pressure data are mandatory. In this paper a simple and reliable method for an in vivo calibration of this kind of transducer is described. The most important error source, the drift of the zero pressure level due to temperature changes, is discussed, and an estimation of the measurement accuracy which can be obtained is given. Moreover, some registrations of subglottal, supraglottal, and transglottal pressure are presented. It is shown that the pressure recordings allow us to obtain estimates of the volume flow in the trachea and pharynx. Analysis of those waveforms appears to lead to new insights into the physical processes underlying voice production. Specifically, an independent glottal contribution to the skewing of the glottal flow pulses is identified.
Auditory contrast and speaker quality variation in vowel perception
Authors: Fox Robert Allen
Published: October 2005

Selective adaption and anchoring effects in speech perception have generated several different hypotheses regarding the nature of contextual contrast, including auditory/phonetic feature detector fatigue, response bias, and auditory contrast. In the present study three different seven-step [hId]-[hqd] continua were constructed to represent a low F0 (long vocal tract source), a high F0 (long vocal tract source), and a high F0 (short vocal tract source), respectively. Subjects identified the tokens from each of the stimulus continua under two conditions: an equiprobable control and an anchoring condition which included an endpoint stimulus from one of the three continua occurring at least three times more often than any other single stimulus. Differential contrast effects were found depending on whether the anchor differed from the test stimuli in terms of F0, absolute formant frequencies, or both. Results were inconsistent with both the feature detector fatigue and response bias hypothesis. Rather, the obtained data suggest that vowel contrast occurs on the basis of normalized formant values, thus supporting a version of the auditory-contrast theory.
Short-term effects of sound exposure on the 2f1-f2 acoustic emission
Authors: Dolan Thomas G. , Abbas Paul J.
Published: October 2005

The 2f1-f2 acoustic emission (AE) was recorded in the ear canals of cats following exposure to tone bursts of 200-ms duration. Exposures known to result in short-term adaptation (i.e., adaptation lasting under 1 s) at the level of the auditory nerve failed to produce significant post-exposure changes in AE amplitude. Given the apparent cochlear origin of the 2f1-f2 AE, this result is consistent with the view that short-term adaptation in the auditory periphery does not involve substantial changes in cochlear mechanics.
Reminiscing—The stereophonic record
Authors: Roys H. E.
Published: October 2005

The author became active in the sound recording field in the early 1930s and remained active in that field until retirement in 1967. When, in 1957, two slightly different systems of recording stereophonic records were introduced for standardization he was a member of the engineering committee of the Record Industry Association of America and Chairman of the Phonograph Committee of the Electronic Industries Association. The situation was unique in that stereophonic recorders and pickups were not readily available and the choice for standardization had to be based largely upon theoretical considerations. The difference between the two was slight. The V-L system recorded one channel vertically and the other laterally. The 45–45 system recorded both channels vertically, but at a 45° angle with respect to the surface of the disk. Record engineers in Europe gathered and decided in favor of the 45–45 system. Engineers in this country did likewise. Thus for the first time in the history of records a common agreement with respect to standardization was reached prior to mass production.
Analysis of elastic wave signals from an extended source in a plate
Authors: Chang Chung , Sachse Wolfgang
Published: October 2005

This paper considers the forward and inverse problems of an extended, finite source of elastic waves in a thick plate. The signals received at a point in the nearfield of a source are computed by a superposition of the signals found with a generalized ray algorithm from point sources of variable strength arranged along a straight line. Synthetic waveforms corresponding to several source types and spatial distributions on the surface and in the interior of the plate are shown. A processing algorithm is also developed which utilizes the signals detected at just one receiver point to obtain the solution to the inverse source problem. Examples are shown in which the time dependence and the spatial distribution of a source are recovered from synthetic waveforms.
Limited aperture effects on ultrasonic image reconstruction
Authors: Kogan Vladimir G. , Rose James H.
Published: October 2005

In the inverse Born approximation the shape of a weak scatterer can be determined from a knowledge of the backscattered ultrasonic amplitude for all directions of incidence and all frequencies. Two questions are considered. First, what information on the scatterer shape is preserved and what is degraded if the scattering data are available only within a limited set of incident directions (limited aperture)? This problem is addressed for a spherical weakly scattering uniform flaw. It is shown that the problem of a general uniform ellipsoidal flaw can be reduced to the spherical case by a scale transformation; however, the apertures in these two cases must be related by the same transformation. Second, limited aperture and finite bandwidth Born inversions were performed for strongly scattering flaws (voids and cracks) using numerically generated scattering amplitudes. These inversions were then compared with the weak scattering analytic results, which show many common features.
Analysis of higher-order mode effects in the circular expansion chamber with mean flow
Authors: Ih Jeong-Guon , Lee Byung-Ho
Published: October 2005

The effects of higher-order acoustic modes produced by the areal discontinuities of the simple expansion chamber with mean flow on the acoustic performance are studied. The chamber is modeled as a piston-driven circular rigid tube with no losses and, by using the Fourier–Bessel expansion, a general expression of the output pressure to the given input uniform volume velocity is obtained for a whole chamber. Quantitative estimation for the transmission loss can be performed using the derived four-pole parameters, whereas the characteristics of the chamber, as a result of the interactions between the plane wave and the transverse waves, can be easily investigated with respect to the relative locations of the inlet/outlet, the chamber length, and the mean flow. The expression as a form of C in four-pole parameters is adopted to describe the chamber characteristics for computational convenience. All the parameters involved in the experimental works by Eriksson [L. J. Eriksson, J. Acoust. Soc. Am. 72, 1208–1211 (1982)] are taken in the examples. Using the derived four-pole parameters, the transmission losses for both the concentric and offset inlet/outlet configurations are predicted and compared with the experimental results. The theoretical results of the present study are in good agreement with the experiments of the authors and the previous works.
Asymptotic fluid–structure interaction theories for acoustic radiation prediction
Authors: Huang H. , Wang Y. F.
Published: October 2005

It is well known that at extremely high or low frequencies, the fluid–structure interaction effects can be represented asymptotically by simple equations. Thus, it appears that an optimum computation scheme for predicting acoustic pressure field radiated from a submerged elastic structure could be a combination of various asymptotic theories and the exact formulation. This paper explores the ranges of applicability of some asymptotic theories, using the problem of radiation from a spherical elastic shell as the bench mark. It is found that the ‘‘added mass’’ and ‘‘plane-wave’’ approximations are quite adequate, respectively, for ka<1.0 and ka>5, where ka is the ratio of the circumference of the spherical shell to the acoustic wavelength. For the intermediate frequency range, a theory termed second-order Doubly Asymptotic Approximation (DAA2) is suitable. At intermediate frequencies near resonances, however, the exact formulation is needed.
Close range scintillations in anisotropic scattering media
Authors: Frankenthal Shimshon
Published: October 2005

Using the Rytov approximation, an expression is derived for the log-amplitude correlation function of weak fluctuations induced in a plane wave propagating in a forward-scattering medium. The expression is valid at any range where weak fluctuations exist, including ranges which are shorter than the correlation length. For ranges well in excess of the correlation length, we derive a general expression for the scintillation index, which applies also in nonisotropic media, for moderate and high frequencies. The behavior of the scintillation index at very short ranges in isotropic media characterized by one or two scales is examined, and its dependence on frequency (k) and range (z) is listed for several regimes. Propagation is also studied in a nonisotropic medium, where the refractivity fluctuations are governed by the Garrett–Munk internal-wave spectrum. Here, the frequency–range dependence of the scintillation index changes from k3/2z5/2 at near ranges to kz2 at more distant ones.
The azimuthal dependence of bistatic surface scattering: A comparison between theory and experiment
Authors: Kinney Wayne A. , Zornig John G.
Published: October 2005

Scattering strength values computed using a time-domain version of the facet-ensemble method [W. A. Kinney and C. S. Clay (to be published)] are compared with some values measured by J. G. Zornig [J. Acoust. Soc. Am. 63, 758–767 (1978)] in an experiment on the azimuthal dependence of bistatic surface scattering. Results are presented for a waterborne 1.3-MHz pulse impinging on a wind-generated surface at a 30° grazing angle. In the experiment, the surface wavelets were mostly long-crested within the ensonified region. Their direction of propagation varied and they were slightly crescent shaped. The wavelets scattered strongly in all azimuthal directions. Agreement between theoretical and experimental data was achieved by approximating the scattered response from a portion of a wavelet by the response of an ensemble of facets oriented tangentially to the portion. Surface scattering experiments that involve complex surface features of large roughness require a complete deterministic description of the surface to help in explaining results.