bluuebunny/crossref_metadata_2025 huggingface dataset:
Group-vote rules for adaptive psychophysical testing
Authors: Kelly W. J. , Lippmann R. P.
Published: October 2005

A procedure is described that allows groups of subjects to be tested using adaptive psychophysical procedures when equipment limitations or experimental design requires each member of the group to be presented with the same stimuli. Group-vote rules are used to classify the group response on any trial as correct or incorrect, and this classification is used as input to standard, single-subject, adaptive procedures. The relationship between the probability of a correct group response and the probability of a correct individual response is derived by assuming members of the group respond independently and have identical psychometric functions. This relationship is used to choose a group-vote rule and an adaptive procedure that leads to a probability of correct individual response at convergence that is close to that which is desired. The usefulness of this procedure is limited to experiments where individual subjects have similar psychometric functions. It has, however, been used extensively for small groups of subjects to collect simple auditory discrimination data.
Dynamics of acoustic resonance scattering from spherical targets: Application to gas bubbles in fluids
Authors: Überall H. , George Jacob , Farhan Ameenah R. , Mezzorani G. , Nagl A. , Sage K. A. , Murphy J. Diarmuid
Published: October 2005

In this study we investigate the dynamics of surface motion of a penetrable spherical body subjected to an incident plane acoustic wave. The results should be valid for objects of rather general internal consistency, since they are based on quite basic physical considerations, but they are illustrated here by the example of a gas bubble in a fluid. It is shown that surface waves generated in the scattering process circumnavigate the target sphere and, by a process of in-phase ’’resonance reinforcement,’’ excite its multipole resonances at those eigenfrequencies at which n+1/2 wavelengths (n being an integer) span the circumference. Phase matching is achieved here due to the fact that the surface wave suffers a phase jump of π/2 at each of the two ’’caustic points’’ on the sphere at which the surface waves converge. Surface motions and circumferential waves on the bubble are graphically demonstrated, both on and off resonance. It is shown that the resonance manifests itself by a large-amplitude angular oscillation of the gas contained in the bubble.
Evaporation–condensation resonance frequency of oscillating vapor bubbles
Authors: Marston Philip L.
Published: October 2005

Approximations for the frequency of the new resonance of a vapor bubble associated with evaporation and condensation are derived from the equations of ’’Vapor bubble dynamics’’ [R. D. Finch and E. A. Neppiras, J. Acoust. Soc. Am. 53, 1402–1410 (1973)]. Previous predictions of the new resonance frequency ω were obtained by numerically solving a secular equation. The purpose of the approximations is to elucidate the significant parameters; for example, the surface tension σ is predicted to greatly influence ω. When the liquid’s thermal conductivity k is sufficiently large, ω∝σ2/3 R−8/3, where R is the equilibrium radius of the bubble; small k gives ω∝σ2 R−4. The approximations are substantiated by comparisons with numerical results for water, nitrogen, and helium. Criteria for their use are presented. Effects of evaporation–condensation resonance on radiation pressure and extinction of sound are suggested.
Real-time synthesis of optical lip shapes from vowel sounds
Authors: Erber Norman P.
Published: October 2005

An analog circuit has been constructed to convert speech (vowels) to Lissajous-type oscilloscope patterns in real time. The method is like that described by Boston [Brit. J. Audiol. 7, 95–101 (1973)], but includes circuit modifications to improve naturalness of lip outline and articulatory change. The speech signal receives preemphasis resembling ear canal resonance and is split into two channels. Two voltages, one proportional to 200–1000 Hz energy (F1) and the other proportional to 200–3000 Hz energy (F2 in front vowels, F1 in back vowels), are generated to control a multiplier and divider, respectively, which vary levels of sinusoidal signals to form the height and width of the lip outline. Resulting patterns resemble lip shapes of vowels in natural speech. Vowel-confusion matrices obtained by lipreading the oscilloscope display (with speech input) are similar to those obtained by lipreading the talker’s face directly.
Communicating through poster sessions
Authors: Burkhard Mahlon D.
Published: October 2005

The poster session as a means of communication at scientific society meetings is described, with emphasis on both strong and weak points. Advice is given presenters and attendees for the most effective use of such sessions.
Cavitation as a mechanism for the biological effects of ultrasound on plant roots
Authors: Carstensen E. L. , Child S. Z. , Law W. K. , Horowitz D. R. , Miller M. W.
Published: October 2005

The growth rate of roots is reduced by exposure to ultrasound at 10 W/cm2 for 1 min. The reduction is somewhat greater at 1 MHz than at 5 MHz. A hydrostatic pressure of 30 atm reduced, but did not eliminate, the effect of ultrasound on growth. The frequency and pressure dependence taken together with earlier observations support the postulate that a cavitationlike mechanism is at least partly responsible for the action of ultrasound on the growth of these developing plant tissues.
Speech synthesis by linear interpolation of spectral parameters between dyad boundaries
Authors: Shadle Christine H. , Atal Bishnu S.
Published: October 2005

A recent study [Olive and Spickenagel, J. Acoust. Soc. Am. 59, 993–996 (1976)] has shown that area parameters derived from linear prediction analysis can be linearly interpolated between dyad boundaries with very little distortion in the resultant synthesized speech. The success of area parameter interpolation raises a question: can other acoustic parameters, such as the power spectrum of the speech waveform, be similarly interpolated? The spectrum is of special interest because speech can be synthesized in real time from spectral parameters on a programmable digital filter. To study this question a speech analysis–synthesis system using spectral parameters (samples of power spectra at different frequencies) was simulated. These parameters were determined from the speech signal at every dyad boundary, and interpolated for intermediate values. Dyad boundaries (representing the limits of transition regions between phonemes) were determined manually. Informal listening tests comparing synthetic speech with and without linear interpolation showed slight degradation in the interpolated speech. This degradation is significantly reduced by using an additional point within the dyad boundaries for interpolation.
Acoustic reflection from a sea bottom with linearly increasing sound speed
Authors: Williams A. O. , MacAyeal Douglas R.
Published: October 2005

We calculate the acoustic reflection coefficient for plane waves, in a homogeneous fluid half-space, incident at arbitrary angle upon an underlying half-space of unconsolidated bottom sediments. The lower half-space, treated here as a fluid, has constant density and a sound speed that increases linearly with depth. An exact formal expression is found for the complex reflection coefficient R, in terms of a modified Bessel function. With no absorption, ‖ R ‖ is unity for all angles except at normal incidence, as would also be expected from ray theory. Assuming bottom absorption, we derive an analytical approximation for R, valid for incident angles ϑ (measured from the interface normal) in the range 10°≲ϑ≲70°, for acoustic frequencies f≳10 Hz, and to about 80° for f≳70 Hz. A high-frequency limit and a small-angle approximation are found. Use of a pseudolinear gradient, suitable at large angles, could extend ϑ to 90°. A more realistic model having layers in the upper part of the bottom is discussed briefly.
Resonance theory of acoustic waves interacting with an elastic plate
Authors: Fiorito Ralph , Madigosky Walter , Überall Herbert
Published: October 2005

Sound transmission and reflection properties of an elastic layer immersed in a fluid are analyzed by extending the resonance formalism, previously developed by us for the case of a fluid layer [J. Acoust. Soc. Am. 65, 9–14 (1979)]. Resonance expressions for the transmission and reflection coefficients have been obtained both in terms of the frequency-thickness variable and of the angle-of-incidence variable. The resonance positions and widths are explicitly obtained from real equations in terms of given material quantities. Comparison of the resonance theory and exact calculations are given for a steel plate immersed in water. The resonance formalism results show excellent agreement with exact theory in all cases. Interferences between overlapping resonances are clearly identified and analyzed. An examination of the limiting form of the y resonances confirms previous empirical findings of other researchers concerning the frequency-thickness behavior of the poles and zeroes of the Rayleigh and Lamb resonances, and in particular the disappearance of Lamb modes and survival of one Rayleigh mode as the plate tends towards a half-space.
On the analysis of the doubly connected problem of vibrating polygonal plates
Authors: Nagaya Kosuke
Published: October 2005

In this paper a method for solving vibration problems of thin polygonal plates, with circular inside edges, is presented. The frequency equations of the polygonal plates are given for various combinations of outer and inner boundary conditions. Numerical calculations are carried out for cases of triangular, square, pentagonal, and hexagonal plates.
Acoustic shadowing by seamounts
Authors: Nutile David A. , Guthrie Albert N.
Published: October 2005

Explosive acoustic sources were dropped from a ship traversing a course approximately perpendicular to a line from the ship to a hydrophone of the Pacific Missile Impact Locating System (P-MILS) near Midway Island. The rectified shot signatures recorded from the hydrophone were aligned for identification of arrivals and assignment to ray paths. The alignment revealed that some arrivals predicted by ray-trace calculations were missing from some signatures. The signals traveled across an area of seamounts located north of the Hawaiian Ridge and the missing arrivals are related to ray-path blocking. The blocked ray paths, and the specific seamounts responsible for the blockages, are identified for three selected shot signatures. The shadowing of the hydrophone by identifiable seamounts for CW signals from a towed, 14.65-Hz source is correlated with the blockage of propagation paths for the shot signals.
Some voicing adjustments of flue organ pipes
Authors: Nolle A. W.
Published: October 2005

The investigation uses a flue organ pipe designed so that mouth height Y, position of the upper lip in the air stream X, and width of the air passage are adjustable. Other dimensions can be altered with interchangeable parts. Rectangular and circular resonators of several lengths, open and stopped, are used. Speaking frequencies are 125 to 500 Hz. Speech for a supply pressure of 55-mm water is described for the useful X,Y range in qualitative terms, and also in terms of sound-pressure level and harmonic content. Behavior is related to resonance frequencies. Stable oscillation of longer pipes occurs in a limited X,Y range unless the first resonance frequency is some 2% lower, relative to harmonic relationship with the next few modes of vibration. As X is varied, for the speaking pipe, the second harmonic has an amplitude minimum, where the phase relative to the fundamental reverses. The acoustic pressure is proportional to mass flow rate over a range of at least 4:1 in tests involving reduction of air pressure or narrowing the passage. Threshold operating pressure for 7-mm mouth height is 5-mm water, in good agreement with Coltman’s flute data. Air supply energy is converted to radiation with about 0.5% efficiency for the stopped pipe.
A finite-element analysis of sound propagation in a nonuniform moving medium
Authors: Dong S. B. , Liu C. Y.
Published: October 2005

The problem of sound propagation in shear flow with temperature gradient in a rectangular duct is studied by a finite-element method. The formulation leads to an eigensystem containing both symmetric and nonsymmetric matrices. A subset of eigenvalues and their corresponding eigenvectors is extracted from this eigensystem by means of a very efficient Block–Stodola iterative technique. Applications of this methodology to various flow problems are presented and comparison of the present results with those of other investigators are made. The present methodology is shown to be computationally economical, accurate, and sufficiently versatile to treat a wide range of duct flow problems.
A method for modeling perforated tube muffler components. I. Theory
Authors: Sullivan Joseph W.
Published: October 2005

A simple method is presented for modeling perforated muffler components such as concentric resonators with perforated flow tube, and expansion chambers and reverse flow chambers with perforated inlet and outlet tubes. The theory includes mean flow, but is confined to those configurations having one acoustically long dimension. It is based on a segmentation procedure in which each segment is described by a transmission matrix. The four-pole parameters of a component are then found from the product of the transmission matrices. The four-pole parameters for configurations having through flow, cross flow, and reverse flow are presented. Because the product matrices are dimensionally small and because no inversion is needed, computational time is much lower than other methods such as finite element or finite difference. This allows rapid and economical modeling to be performed where iterative solutions are required because of dominating finite amplitude effects, for example.
Coupled mode analysis of multiple rough surface scattering
Authors: Beilis A. , Tappert F. D.
Published: October 2005

The range dependent boundary condition imposed by a rough surface serves to couple the normal modes of an underwater acoustic field. Beginning with the parabolic wave equation, the solution is expanded in terms of normal mode depth functions modulated by random amplitudes having a quasistatic time dependence. A system of master equations for the quantities 〈an(r,t) a*n(r,t+τ) 〉 is derived, where the an(r,t) are the normal mode amplitudes. It is found that for τ≠0, the sideband spectra (analytically obtained by Fourier transformation of the temporal coherence function with respect to τ) has information with regard to the directionality of the wind driving the rough surface. For τ=0 we obtain a system of equations for the mean power in each mode describing the transfer of energy between modes. Explicit formulas for the coupling coefficients (transition probabilities) are obtained in terms of the spectrum of the rough surface. The formalism is applied to multiple ocean surface scattering to long ranges. Transmission loss, intensity redistribution, and the approach to equipartition of energy as a function of range and depth are obtained numerically. Relaxation ranges characterizing equipartition are predicted for various physical conditions.
Harmonic properties of the annular membrane
Authors: Gottlieb H. P. W.
Published: October 2005

Properties of a vibrating annular membrane are analyzed mathematically and numerically to investigate the relative harmonicity of the higher-order modes compared with the fundamental mode. The harmonicity depends on the zeros of a cross-product of Bessel functions. For a ratio of external-to-internal diameter up to about 1.2, the higher modes have frequencies which are very nearly exact integer multiples of the fundamental frequency. For circularly symmetric modes, the ratio of all higher radial mode frequencies to exact harmonic values is less than 1.0006 (a logarithmic cent), a ratio imperceptible to a listener. Angle-dependent modes also give good harmonicity, especially if some lower radial modes are suppressed. Thus the modes of an annular membrane whose external-to-internal diameter ratio is less than 1.2 are much more harmonic than those of the full circular membrane of a conventional drum. The theoretical harmonicity is at least as good as reported for stringed melodic instruments (piano, violin). The analysis suggests characteristics for construction of an annular drum-head which is supported on concentric rims of two cylinders; to sound the drum, a braced hoop might be used to excite radial modes, or strikers with grooved faces might be used to excite angular modes without exciting lower radial modes.
Relation between voice-onset time and vowel duration
Authors: Port Robert F. , Rotunno Rosemarie
Published: October 2005

As part of an investigation of the temporal implementation rules of English, measurements were made of voice-onset time for initial English stops and the duration of the following voiced vowel in monosyllabic words for New York City speakers. It was found that the VOT of a word-initial consonant was longer before a voiceless final cluster than before a single nasal, and longer before tense vowels than lax vowels. The vowels were also longer in environments where VOT was longer, but VOT did not maintain a constant ratio with the vowel duration, even for a single place of articulation. VOT was changed by a smaller proportion than the following voiced vowel in both cases. VOT changes associated with the vowel were consistent across place of articulation of the stop. In the final experiment, when vowel tensity and final consonant effects were combined, it was found that the proportion of vowel duration change that carried over to the preceding VOT is different for the two phonetic changes. These results imply that temporal implementation rules simultaneously influence several acoustic intervals including both VOT and the ’’inherent’’ interval corresponding to a segment, either by independent control of the relevant articulatory variables or by some unknown common mechanism.
Considerations in applying clustering techniques to speaker-independent word recognition
Authors: Rabiner L. R. , Wilpon J. G.
Published: October 2005

Recent work at Bell Laboratories has demonstrated the utility of applying sophisticated pattern recognition techniques to obtain a set of speaker-independent word templates for an isolated word recognition system [Levinson et al., IEEE Trans. Acoust. Speech Signal Process. ASSP-27 (2), 134–141 (1979); Rabiner et al., IEEE Trans. Acoust. Speech Signal Process.(in press)]. In these studies, it was shown that a careful experimenter could guide the clustering algorithms to choose a small set of templates that were representative of a large number of replications for each word in the vocabulary. Subsequent word recognition tests verified that the templates chosen were indeed representative of a fairly large population of talkers. Given the success of this approach, the next important step is to investigate fully automatic techniques for clustering multiple versions of a single word into a set of speaker-independent word templates. Two such techniques are described in this paper. The first method uses distance data (between replications of a word) to segment the population into stable clusters. The word template is obtained as either the cluster minimax, or as an averaged version of all the elements in the cluster. The second method is a variation of the one described by Rabiner [IEEE Trans. Acoust. Speech Signal Process. ASSP-26 (3), 34–42 (1978)] in which averaging techniques are directly combined with the nearest neighbor rule to simultaneously define both the word template (i.e., the cluster center) and the elements in the cluster. Experimental data show the first method to be superior to the second method when three or more clusters per word are used in the recognition task.
Mode coupling of guided elastic waves in wire with weak surface corrugation
Authors: Hirao Masahiko
Published: October 2005

This analytical study aims to explain the experimental result of the mode coupling of elastic waves in a long circular wire by means of the surface corrugations of the wire. It is assumed herein that the wire is made of ideally homogeneous, isotropic, linearly elastic material and its free surface is subjected to weak and continuous corrugation. On the basis of the weakness of corrugation, the multiple scales are introduced to formulate the problem in a perturbation scheme. It is found, as expected, that the mode coupling does occur as the result of scattering from the corrugated surface at a certain frequency where the two modes have the same phase velocity. Coupled-mode equations which govern the amplitude variation in the coupling are then derived systematically from the compatibility condition. The coupling coefficients depend on the modes involved, the geometrical characteristics of the surface corrugation, and the material constant of the wire. The resultant variation of amplitudes well characterizes the pulse distortion observed in the experiments.
The pitch of vibrato tones
Authors: Shonle John I. , Horan Kathryn E.
Published: October 2005

A review of previous experiments on the pitch of vibrato tones and the reasons why a new measurement was needed are given. A method of adjustment was used to find the pitch for tones with center frequencies of 220, 440, 880, and 1500 Hz, with total nominal vibrato widths of 50, 100, and 200 cents, and vibrato rates of 4, 6, and 8 Hz. In one case a complex (square) wave was used as the carrier. The pitch is close to the geometric mean of the two extreme frequencies. Another experiment, using an asymmetrical vibrato waveform, shows an averaging of all frequencies present and not just the extreme frequencies.
Evaluation of vowel normalization procedures
Authors: Disner Sandra Ferrari
Published: October 2005

Vowel normalization procedures are commonly evaluated on the basis of how effectively they separate the vowels of a single test data set into distinct groups corresponding to the phonetic categories of that language. A quantifiable method of evaluation is proposed here, based on how much of the overall variance is removed from the data. This evaluation method is applied to the vowels of six different Germanic languages which have been normalized according to four different procedures. It is shown that no one normalization procedure is the most effective for all languages. Furthermore, some of the most successful of these normalizations introduce procedural artifacts into the data, and as a result the relative quality of vowels across languages or dialects is altered. In such cases, it is shown that comparisons of the normalized vowels of one language with the (separately) normalized vowels of another language are not valid if the vowel systems are different. Some reasons for the appearance of these procedural artifacts are discussed.
Thermal effect on acoustoelasticity of isotropic elastic materials
Authors: Tokuoka Tatsuo
Published: October 2005

The thermal effect on the propagation velocities in deformed isotropic thermoelastic material are investigated theoretically. First, isotropic thermoelastic materials in which the strain, the temperature or the entropy density, and the temperature gradient are adopted as the independent state variables, are defined. Then, homothermal and homentropic waves, which are purely mechanical waves, are defined. The propagation velocities of the principal longitudinal and transverse waves are determined. The transverse waves of two types have the same velocities, while the longitudinal waves of two types have different velocities, and the difference is the second order of the strain or stress.
A mobility analogy equivalent circuit of a magnetostrictive transducer in the presence of eddy currents
Authors: Meeks Steven W.
Published: October 2005

The equivalent circuit in the mobility analogy of a magnetostrictive transducer in the presence of eddy currents is derived. This equivalent circuit is used to predict the effect of eddy currents on the efficiency, the electrical impedance, the transmitting responses, and the receiving sensitivity of a magnetostrictive transducer. Lumped-parameter equivalent circuits are also presented which use approximations to the exact theory to simply and accurately predict the efficiency and electrical impedance of a transducer with eddy currents within a frequency range of practical interest near the clamped characteristic frequency. It was found that the eddy current theory predicted a sharp drop in the eddy current loss in a narrow frequency range just past resonance. This effect was experimentally observed by Savage and Abbundi [IEEE Trans. Magn. 14, 545 (1978)].
Profile transformation of a propagating explosive wave
Authors: Fridman V. E. , Petukhov Yu. V.
Published: October 2005

The explosive signal time constant is derived as a function of distance.
A coupled system for subharmonics of any order
Authors: El-Mokadem Ferial T. , Seriki Omotayo A. , Newcomb Robert W.
Published: October 2005

A set of two coupled differential equations with square law nonlinearities is shown to have dominant and stable subharmonic solutions. Mathematical expressions characterizing the subharmonic solutions and their regions of stability are obtained. It is further shown that under appropriate choice of system parameters a resulting system described through these coupled differential equations possesses an exact stable subharmonic of any real order. From this, a design theory is obtained for a system which yields an arbitrary dominant subharmonic. The theory is also directly applicable to the creation of arbitrary stable harmonics.
Experiments on the transmission paths and dynamic behavior of engine structure vibrations. I. Background and static tests
Authors: Okamura Hideo
Published: October 2005

In order to establish a method of estimating the engine structure surface responses, a series of experiments was made on a four-cylinder (bore: 86 mm, stroke: 84 mm), in-line, water-cooled high-speed diesel engine. The results obtained in static conditions are summarized with the necessary background. The propagation behavior of excitation forces in the engine structure, the vibration behavior of the vibration transmission paths, and the transfer functions of the transmission paths were examined in static conditions. The distribution of the damping in the engine structure, the influence of cooling water, the lubrication oil, the oil pressure, and the crank position on the transfer functions were also examined. After the experiments, we found that (a) a different excitation force induces different responses on the engine structure surfaces because of its different transmission paths and their transmission behavior; (b) the forces applied on the cylinder head can be transmitted along the cylinder head bolts, and the engine structure can be excited by this force just as strongly as by the identical force applied on the piston top; and (c) most of the damping in the engine structure is induced by the oil film existing around the main moving parts such as the pistons, the connecting rods, and the crankshaft.
Asymptotic analysis for dispersive fluid filled tubes
Authors: Moodie T. Bryant , Haddow J. B.
Published: October 2005

In a previous paper [J. Acoust. Soc. Am. 64, 522 (1978)] we obtained a new approximate equation governing the propagation of small perturbations to the pressure in a thin-walled fluid filled elastomer tube. There, the spatial fluctuations in the pressure perturbation for fixed time were evaluated numerically by a procedure based on the Fast Fourier Transform (FFT) algorithm. Here, by means of an asymptotic analysis, based on a modified steepest descent method, we explain an apparent anomaly in the numerical results by exhibiting the existence of a forerunner wave and investigate the accuracy of the large time asymptotic results, for times which may be regarded as small or intermediate, by comparing them with the results from the FFT algorithm. It is found that the results obtained from the asymptotic analysis are in close agreement with those obtained from the FFT for moderate times and in qualitative agreement for relatively small times. For nondimensional times greater than 100 the positions of the zeros of the pressure perturbation agreed with those obtained from the FFT to better than four significant figures for the main part of the disturbance.
The coding of intensity and the interaction of forward and backward masking
Authors: Penner M. J.
Published: October 2005

In general, the detectability of a signal preceded and followed by noise maskers is less than the prediction based on a simple addition of the effects of the maskers (i.e., an intensity sum). Data verifying and extending this finding were collected in a variety of conditions in which the two maskers either surrounded the signal in time or preceded it. These data are used to support two related claims. First, the failure of the intensity-sum argument is likely to be due to nonlinearities in the coding of intensity. Second, the signal threshold is a monotonic measure of the internal percept at essentially the same time relative to the signal for different masking conditions. This latter result negates the integrator-movement hypothesis (which holds that the time varies) and provides important support for the chain of derivations obtained by Penner and Shiffrin [J. Acoust. Soc. Am. 67, 617–627 (1980)].
How are syllables used to recognize words?
Authors: Cole Ronald A. , Jakimik Jola
Published: October 2005

Our subjects were instructed to push a response button as quickly as possible whenever they detected a mispronounced word in a story. Mispronunciations were produced by changing a syllable-initial /p/ or /k/ to its voiced counterpart (/b/ or /g/). The syllable stress and syllable position (first versus second) of the mispronunciation were varied in a 2×2 design. As expected on acoustic grounds, mispronunciations were detected more often in stressed than unstressed syllables. However, reaction times to mispronunciations in both stressed and unstressed syllables were about 200-ms faster in the second syllable of a word. The finding of faster reaction times to second syllables is consistent with the assumption that words are accessed from the sounds which begin them.
Single mode transmission and acoustic backscattering measurements in a laboratory waveguide
Authors: Clay Clarence S. , Huang Kung
Published: October 2005

Our purpose was to make ’’farfield’’ sound scattering measurements in a limited space. We used a thick waveguide, about 35 acoustic wavelengths deep, and excited it in the first mode. The waveguide had pressure release surfaces on the top and bottom. To excite and receive in the first mode, we used a vertical array that was amplitude shaded to match the eigenfunction of the first mode. Experimental measurements verified that 90% of the energy was in the first mode. A pair of omnidirectional transducers were used as a probe transmitter and receiver to calibrate the system for scattering measurements. At 220 kHz, 24-cm depth, and 100-cm range, the cross section of the scattering region was about 6 cm high. At this range the first Fresnel zone was 10 cm wide. Scattering measurements of the target strength of a steel sphere, diameter 0.8 cm, gave −54±1 dB compared to −54 dB theoretical target strength.
Surface-duct propagation: An evaluation of models of the effects of surface roughness
Authors: Hall Marshall
Published: October 2005

The results of 25 measurements of acoustic propagation to a range of 6 km in the ocean mixed layer, at frequencies of 4, 8, and 16 kHz, are summarized and compared with a number of propagation models. Within the mixed layer , the acoustic energies have considerable variability and are usually 10 to 20 dB less than the prediction of normal-mode theory for a perfectly reflecting surface (the shortfall increases with frequency). At 8 kHz, the (negative) correlation of acoustic energy with surface roughness (χ) is highly significant. The frequency dependence of the average data is similar to that predicted by the long-range version of the AMOS model but different to that predicted by the Baker model. At 16 kHz, the average energy is about 7 dB less than spherical spreading minus absoption; the cause of this attenuation is unexplained. Below the mixed layer (in the ’’shadow zone’’), the measured energies also have considerable variability. They are usually 10 to 15 dB greater than the predictions of normal-mode theory and decrease with frequency less rapidly than does the AMOS model. The measured ratios of below-duct to in-duct energies tend to increase with χ/λ; whereas, the Helmholtz–Kirchhoff theory of surface scattering predicts that, for values of χ/λ that correspond to the experimental values, the ratio should be a constant.
Estimation of source motion from time delay and time compression measurements
Authors: Carter G. Clifford , Abraham Phillip B.
Published: October 2005

Expressions are derived for estimating the cross line-of-sight speed (CLSS) component of velocity from relative time compressions (RTC’s) and time delays. Theoretical expressions for the rms error in radial speed and CLSS are given and have been corroborated by simulation experiments. These expressions show the relative difficulty of estimating radial speed information as compared with CLSS.
A comparison of three schemes for filtering signals which have propagated through a random multipath medium
Authors: Mangano D. T.
Published: October 2005

Three filtering techniques that can be employed in the recovery of a signal after it has propagated through a nonrandom, distortionless, multipath channel have been studied. The generalization of these studies to the random medium situation is the objective of this paper. A fixed, omnidirectional source emits a signal which propagates through a multipath medium and is detected by an array of point receiving elements located at some arbitrary distance from the source. The medium is characterized by a set of attenuation and delay random variables associated with each of the multiple paths. In addition, the additive noise contributed by the medium is assumed to be negligible. The detected signals are then processed by delay filtering, matched filtering, or frequency-inverse filtering. The criterion for comparison of these three schemes is the ratio of the standard deviation of the filtering scheme’s output time-average power to the expected value of this power. It is found that under certain constraints this ratio is approximately independent of the delay statistics of the medium, and the duration and frequency of the input for the three filtering schemes. In addition, this ratio is approximately equal for delay and matched filtering and is √2 times greater for frequency-inverse filtering.
Noise correlation functions for arbitrary receiver orientation and steering direction in vertically anisotropic, azimuthally isotropic noise fields
Authors: Oelkers C. I.
Published: October 2005

A first approximation of array signal-to-noise gain for linear or planar arrays is obtained by assuming ideal sound transmission from source to receivers having zero time delay (unsteered elements) in the presence of two-dimensional or three-dimensional isotropic noise. The resulting noise correlation functions are the familiar J0  (x) and sin x/x. These functions are usually extended for computing the noise correlation functions for arbitrary receiver orientation steered to any direction and receiving any grade of signal transmission. A more general form of the noise correlation functions is available for any orientation of a pair of receivers with zero time delay in the presence of a vertically anisotropic, azimuthally isotropic noise field. The present paper treats noise correlation for an array of arbitrarily oriented receivers in the same environment. Furthermore, the generalized functions accommodate beamforming in any direction. Methods for simplifying noise gain computations are presented.
Anomalous damping of the pulsation noise from small air bubbles in water
Authors: McComb W. D. , Ayyash S.
Published: October 2005

Damping constants of the sound pulses emitted by air bubbles formed at nozzles submerged in water were measured for nozzle diameters ranging from 2 to 5 mm. The measured values of the damping constants were found to depend systematically on the length by which the horizontal nozzle protruded from a supporting structure. Values ranged from 25% greater than to 50% less than the expected theoretical value for the damping constant. Certain features suggested that acoustic interference might be responsible for this effect, but oscilloscope traces of the pressure pulse did not support this idea.
Comprehensive comparison of multiplicative and additive processing in acoustical imaging
Authors: Sato Takuso , Ikeda Osamu
Published: October 2005

First, a generalized construction of an acoustical imaging system which consists of both multiplicative and additive signal processing parts is shown. Then, conventional imaging systems are explained and classified as special cases of the generalized form, and their special features are compared comprehensively from the viewpoint of the goodness of the reconstructed images. It is shown that, in general, multiplicative processing is effective for resolution improvement and imaging under phase turbulence, while additive processing is effective for imaging under additive noises.
Influence of auditory fatigue on masked speech intelligibility
Authors: Parker Donald E. , Martens William L. , Johnston Peggy A.
Published: October 2005

Intelligibility of PB word lists embedded in simultaneous masking noise was evaluated before and after fatiguing-noise exposure. Intelligibility was determined by observing the number of words correctly repeated during a shadowing task. Both the speech signal and the masking noise were filtered to a 2825–3185-Hz band. Masking-noise levels were varied from 0- to 90-dB SL. Fatigue was produced by a 1500–3000-Hz octave band of noise at 115 dB (re 20 μPa) presented continuously for 5 min. The results of three experiments indicated that speech intelligibility was reduced when the speech was presented against a background of silence but that the fatiguing-noise exposure had no effect on intelligibility when the speech was made more intense and embedded in masking noise of 40–90-dB SL. These observations are interpreted by considering the recruitment produced by fatigue and masking noise.
One-dimensional velocity inversion for acoustic waves: Numerical results
Authors: Gray Samuel H. , Bleistein Norman
Published: October 2005

We consider the inverse problem of determining small variations in propagation speed from remote observations of signals which pass through an inhomogeneous medium. Under the conditions (1) that the variations can be written as a small perturbation from a known reference value and (2) that the medium of interest varies in one direction only, an integral equation has been developed for the variations which can be solved in closed form. Here, a technique is presented to obtain and process synthetic data from a scattering profile of arbitrary shape. The results of numerical testing show that, as long as a velocity variation is indeed ’’small,’’ both its size and its shape can be reproduced with negligible error by this method.
Caustics and the spreading of adjacent acoustic rays
Authors: Kinney Wayne A. , Pierce Allan D.
Published: October 2005

Some previous discussions of phase shifts at caustics have employed the WKBJ method of solution to the wave equation for a point source in a vertically stratified medium where a single sound-speed minimum exists. Geometrical acoustic techniques are used in this paper to show for the same problem that a ray encounters only one caustic between turning points (starting with the first and second points), and that turning points and points of encounter with caustics approach one another with increasing range from the source.
Flow-induced tones in side-branch pipe resonators
Authors: Pollack M. L.
Published: October 2005

Acoustic tones generated by turbulent flows and shear-layer-instability interactions with side-branch resonator pipes were investigated experimentally using fast Fourier transform techniques. The experimental values of resonant frequencies and instability frequencies were compared with predictions for two stages of shear-layer interaction. Relative tonal amplitudes are shown to demonstrate cut-in and cut-out phenomena. The qualitative differences between turbulent-flow-generated tones and instability-generated tones are also noted.
Response properties of spiral ganglion neurons in cochleas damaged by direct mechanical trauma
Authors: Robertson D. , Cody A. R. , Bredberg G. , Johnstone B. M.
Published: October 2005

Electrical activity of single neurons in the spiral ganglion of the guinea pig cochlea was correlated with receptor hair cell damage produced by local mechanical lesions of the organ of Corti. Damage to or loss of hair cells was assessed using scanning electronmicroscopy. Principal finds were (1) neurons emanating from damaged regions showed changes in their tuning curves such as loss of sensitivity, broadening of tuning curves; (2) in some cases, the loss of sharp tuning tip resulted in an apparent shift of the tuning curve to lower frequencies; and (3) apparently pure outer hair cell lesions, of limited spatial extent, could result in the same effects as mixed inner and outer hair cell lesions.
On the transition between the sounding modes of a flute
Authors: Sawada Yasuji , Sakaba Shigeo
Published: October 2005

Mode transitions between the sounding modes of a flute were studied experimentally with an artificial mouth. This consisted of a nitrogen beam blown through a nozzle onto the embouchure of a real flute head pipe connected to a single open pipe. The nature of the transition depends sensitively on the angle of attack, the transverse displacement, and the length of the nitrogen beam. A qualitative model is discussed to understand the nature of the mode transition.
Some observations on simultaneous and nonsimultaneous masking
Authors: Gorga Michael P. , Stelmachowicz Patricia G. , Abbas Paul J. , Small Arnold M.
Published: October 2005

The interactions between phase, signal level, and interstimulus interval (Δt) were examined in the transition region between simultaneous and nonsimultaneous masking. Phase effects as large as 22 dB were observed in forward masking. These trends can be explained by considering the effects of phase upon the stimulus envelope.
The threshold for binaural interaction
Authors: Hafter E. R. , Kimball P.
Published: October 2005

The absolute sensitivity of the binaural auditory system was studied by asking subjects to discriminate tones that were truly monaural from dichotic tones that sounded monaural because of an extremely large interaural difference of intensity. Thresholds for this discrimination across the range of frequencies from 250 to 4000 Hz were achieved when the tones in the weaker channel were in the region from −45 to −50 dB relative to tones in the stronger channel. Since the monaural reference tones, as well as the stronger signals in the dichotic conditions, were chosen to be 61 dB sensation level (SL), the weakest levels for which binaural interaction could be measured appear to have been on the order of 10 to 15 dB SL.
Cryogenic acoustic microscopy
Authors: Heiserman J. , Rugar D. , Quate C. F.
Published: October 2005

Resolution in the scanning acoustic microscope is determined by wavelength which is in turn limited by attenuation in the acoustic medium. In order to make use of the low attenuation found in cryogenic liquids we have developed an acoustic microscope suited for use at low temperatures. In this paper we present images taken in liquid argon held at 85°K and in superfluid helium at 1.95°K. In liquid argon, wavelengths as short as 0.43 μm were achieved while in preliminary work with superfluid helium a wavelength of 0.36 μm was used. In order to operate in liquid helium, it was necessary to improve the power transfer from the acoustic lens to liquid helium by using double quarter-wave matching layers. Techniques of fabricating and testing these layers are described. Finally, prospects for operating at still shorter wavelengths in superfluid helium held at temperatures below 0.5°K are discussed.
Signal characterization using spectral microanalysis
Authors: Robertson G. H.
Published: October 2005

The dynamic history of narrow band ’’line’’ components in spectrograms has customarily been characterized by bandwidth variations and changes in the center frequency of the ’’line.’’ Analysis techniques are described that enable ’’instantaneous’’ amplitude and frequency estimates to be obtained. Characterization by the new techniques describes significant spectral features in terms more closely related intuitively to the mechanisms causing them and helps visual identification of correlated effects in a frequency versus time spectrogram display. Spectrograms obtained with the new techniques are shown to illustrate the improvements obtainable. The term ’’microanalysis’’ is suggested here to describe the new techniques, since they allow feature resolution to be improved in the time and frequency domains simultaneously for sufficiently strong signals.
Psychophysical tuning curves for combination tones 2f1−f2 and f2−f1
Authors: Formby C. , Sachs R. M.
Published: October 2005

A simultaneous masking paradigm was employed to demonstrate that combination tones are ’’stimulus-like’’ in nature. Three musically sophisticated listeners adjusted the level of pure tones at various frequencies to just mask a pulsing signal corresponding to a tone at 1200 Hz and 20 dB SPL. The signal was produced by four stimulus conditions: (1) a pulsing tone at 1200 Hz; (2) a combination tone at 2f1−f2=1200 Hz produced by a continuous f1 at 1650 Hz and a pulsing f2 at 2100 Hz; (3) a control for condition 2 with a pulsing tone at 1200 Hz and a continuous f1 at 1650 Hz; and (4) a combination tone at f2−f1=1200 Hz produced by a continuous f1 at 1900 Hz and a pulsing f2 at 3100 Hz. Across subjects and stimulus conditions the shapes of the tuning curves were similar; whether for an externally presented single tone or a combination tone, minimum masker level (which corresponds to the tuning-curve ’’tip,’’ the frequency at which masking is most effective) was always at frequencies near 1200 Hz. These findings are consistent with previous psychophysical as well as recent physiological evidence which indicates that, regardless of how generated, each of the combination tones 2f1−f2 and f2−f1 is present in the motion of the basilar membrane in the cochlear region around the characteristic place of the combination-tone frequency.
Psychophysical two-tone suppression as a function of input level for f2/f1≳1.0
Authors: Humes Larry E.
Published: October 2005

Psychophysical two-tone suppression was measured in three normal-hearing young adults using the pulsation-threshold technique. The primary objective was to study the effect of L1 on psychophysical two-tone suppression for f2/f1≳1.0. Measurements were obtained at low and mid frequencies and for input levels ranging from 40 through 85 dB SPL. For f1=1000 or 2000 Hz, suppression increased initially with L1 and then decreased for L1?55 to 70 dB SPL. For f1=500 Hz, however, suppression increased monotonically throughout the range of L1 values examined. These findings are explained by assuming that for f1?1000 Hz the nonlinear mechanism responsible for two-tone suppression is very susceptible to reversible dysfunction produced by the presentation of high-intensity stimuli.