bluuebunny/crossref_metadata_2025 huggingface dataset:
The group velocity of normal modes
Authors: Chapman D. M. F. , Ellis Dale D.
Published: October 2005

A simple, general formula for normal mode group velocities provides an intuitive grasp of the factors influencing group velocity, especially for shallow water environments associated with strong seabed interaction. This is demonstrated using some hypothetical shallow water environments, and by comparing mode shapes at different frequencies. The formula is especially convenient to implement in normal mode computer codes which already perform similar calculations for mode normalization and attenuation coefficients. Using the WKB approximation to the normal mode functions, the formula is identified with the average horizontal speed of the ray equivalent to the mode. For a shallow water environment with bottom interaction, the group velocity formula is shown to include the beam and the time displacement effects of modified ray theory. This result strenghthens the ray/mode analogy which is used in analyzing ocean acoustics problems.
Foil electret transducer for blood pressure monitoring
Authors: West J. E. , Busch-Vishniac I. J. , Harshfield G. A. , Pickering T. G.
Published: October 2005

A foil electret microphone for use under the cuff of an automatic blood pressure monitoring system is described. The transducer is designed to operate with relatively flat sensitivity over a static pressure range of 40 to 250 mm Hg (5.33×104 to 3.33×105 dyn/cm2). The new electret microphone differs from conventional microphones used for airborne sound reception in two ways: (1) the diaphragm thickness is 50  μm rather than the typical 12.5 or 25  μm, and (2) the backplate contains a set of annular ridges spaced at 4 mm rather than the typical 7–10 mm. This microphone offers three advantages over the piezoelectric microphone now in use: (1) greater tolerance in positioning the microphone over the brachial artery, (2) nearly 20-dB higher sensitivity and signal-to-noise ratio, and (3) the ability to obtain measurements with the microphone placed midway between the elbow and shoulder. Tests of the new foil electret microphone in conjunction with the automatic blood pressure monitoring system indicate that the automatic and conventional measurements of systolic and diastolic blood pressure agree to within 5 mm Hg at least 90% of the time. In addition, the electret microphone is able to obtain automatic measurements on subjects with a wider range of ages and sizes.
Characteristics of the glottal turbulent noise source
Authors: Hillman Robert E. , Oesterle Elizabeth , Feth Lawrence L.
Published: October 2005

This investigation utilized a reflectionless tube technique to obtain direct estimates of turbulent noise produced at the glottis during whispered vowels. In the past, the glottal turbulent noise source has been described theoretically as a series pressure source having a spectrum that is relatively flat for 2 or 3 oct around a center frequency [K. N. Stevens, J. Acoust. Soc Am. 50, 1180–1192 (1971)]. Center frequency is determined primarily by the area of the constriction at which turbulence is produced with the volume velocity of air flowing through the constriction. The present results were shown to substantiate this theoretically based description of the glottal turbulent noise source. In addition, there was no significant difference between the glottal turbulent noise spectra of male and female speakers. The application of these findings to the synthesis of whispered vowels is discussed.
Effect of burst amplitude on the perception of stop consonant place of articulation
Authors: Ohde Ralph N. , Stevens Kenneth N.
Published: October 2005

We have examined the effects of the relative amplitude of the release burst on perception of the place of articulation of utterance-initial voiceless and voiced stop consonants. The amplitude of the burst, which occurs within the first 10–15 ms following consonant release, was systematically varied in 5-dB steps from −10 to +10 dB relative to a ‘‘normal’’ burst amplitude for two labial-to-alveolar synthetic speech continua—one comprising voiceless stops and the other, voiced stops. The distribution of spectral energy in the bursts for the labial and alveolar stops at the ends of the continuum was consistent with the spectrum shapes observed in natural utterances, and intermediate shapes were used for intermediate stimuli on the continuum. The results of identification tests with these stimuli showed that the relative amplitude of the burst significantly affected the perception of the place of articulation of both voiceless and voiced stops, but the effect was greater for the former than the latter. The results are consistent with a view that two basic properties contribute to the labial–alveolar distinction in English. One of these is determined by the time course of the change in amplitude in the high-frequency range (above 2500 Hz) in the few tens of ms following consonantal release, and the other is determined by the frequencies of spectral peaks associated with the second and third formants in relation to the first formant.
Suppression of auditory nerve responses. II. Suppression threshold and growth, iso-suppression contours
Authors: Javel Eric , McGee JoAnn , Walsh Edward J. , Farley Glenn R. , Gorga Michael P.
Published: October 2005

Two-tone ‘‘synchrony suppression’’ was studied in responses of single auditory nerve fibers recorded from anesthetized cats. Suppression thresholds for suppressor tones set to a fiber’s characteristic frequency (CF) were approximately equal to discharge rate thresholds for CF tones. Suppression thresholds above and below CF were usually lower than the corresponding discharge rate thresholds. However, at all frequencies studied (including CF), suppression thresholds were higher than the corresponding thresholds for discharge synchronization. Across fibers, rates of suppression growth for suppressors at CF were greatest in low-CF fibers and least in high-CF fibers, and there was a systematic decrease in suppression growth rate at CF as CF increased. Within fibers, rates of suppression growth above CF were typically less than at CF, and slopes were monotonically decreasing functions of frequency. Within-fiber rates of suppression growth below CF were variable, but they usually were greater than rates of growth at CF. Iso-suppression contours (frequencies and intensities producing criterion amounts of suppression) indicated that tones near CF are the most potent suppressors at near-threshold intensities, and that the frequency producing the most suppression usually shifts downward as the amount of suppression increases. These data support the notion that synchrony suppression arises primarily as a passive consequence of hair cell activation.
Side-lobe reduction in the ring array pattern for synthetic aperture imaging of coherent sources
Authors: Luthra Ajay K. , Kassam Saleem A.
Published: October 2005

A new technique is described for image formation using a circular array of transducer elements in which each element acts as both a transmitter and receiver. By processing the amplitude and phase measurements acquired in such a system in a particular way, it is shown that it is possible to approach the performance of a transmit–receive filled circular aperture of the same dimension. The technique combines a synthetic aperture scheme with an earlier approach for array pattern synthesis ( J2 synthesis). The proposed technique does not require spatial incoherence of reflections from the object plane, which was a severe limitation in earlier use of J2 synthesis. The effect of array sampling with a finite number of transducer elements is also examined.
Calculation of subjective preference at each seat in a concert hall
Authors: Ando Yoichi
Published: October 2005

This paper represents a method of calculating the subjective preference of sound fields in concert halls before construction. Subjective preference judgments (paired comparison tests) were systematically performed using fully independent objective parameters of acoustic information which describe the signals to the two ears. The sound fields with various combinations of listening level, delay of early multiple reflections, subsequent reverberation time, and magnitude of the interaural cross correlation were simulated with the aid of a digital computer. The optimal conditions maximizing the subjective preference could be found for each objective parameter, because the parameters had an almost independent effect on the subjective preference judgments. Based on the linear scale value, which is obtained by applying the law of comparative judgment, we can calculate a total preference value according to the ‘‘principle of superposition.’’ Examples of calculating the preference values by use of the plan and the cross section of a concert hall are described.
Community response to blasting
Authors: Fidell Sanford , Horonjeff Richard , Schultz Theodore , Teffeteller Sherri
Published: October 2005

Annoyance due to chronic exposure to blast noise and vibration was assessed in residential areas near two surface mines and a quarry. It was found possible to base useful prediction of the prevalence of high annoyance on a metric of outdoor ground vibration related to high centiles of the long term distribution of exposure levels.
Temporal peak intensity
Authors: Carstensen E. L. , Parker K. J. , Barbee D. B.
Published: October 2005

Two methods for measurement of the maximum intensity Im as defined by the National Council for Radiation Protection are compared. One uses a calibrated broadband hydrophone; the other uses a spherical radiometer. A suggestion is made for measurement of a spatial average, temporal maximum intensity to be used in the nearfield of a transducer.
Reflection from a boundary with periodic roughness: Theory and experiment
Authors: Jungman Alain , Adler Laszlo , Achenbach Jan D. , Roberts Ronald
Published: October 2005

Reflection of elastic waves from a traction-free solid–air boundary of periodic sawtooth profile is investigated experimentally and analytically. For an incident plane wave the surface displacements on the profile are computed as the solution of a singular integral equation. The reflected field is subsequently obtained by using an integral representation for the reflected field. Experimental results are presented for the relative amplitude spectrum for reflection from brass–air, perspex–air, and steel–air boundaries. Both the theoretical and the experimental results show that surface resonances of the profile significantly affect the frequency spectrum of the reflected waves. It is shown that the existence of sharp dips in the amplitude spectra of reflected waves can be attributed to destructive interference between direct reflections and reradiation from surface-resonance motions. Good agreement is obtained between calculated results and experimental data.
Acoustic coupling between a pulsating and an oscillating sphere
Authors: Thompson William , Reese J. Mark
Published: October 2005

The modification of the radiation impedance load on each of two equal-sized spherical-shaped sources, one vibrating in the pulsating or n=0 mode and the other in the oscillating or n=1 mode has been calculated. Plots of the normalized resistive and reactive components of the modified radiation impedance are presented as a function of the wavelength size and separation of the two spheres.
Comments on ‘‘Kramers–Kronig relationships and wave propagation in composites’’ by A. I. Beltzer [J. Acoust Soc. Am. 7
3, 355 (1983)]
Authors: Sayers C. M.
Published: October 2005

It will be shown that local approximations to the Kramers–Kronig relations are not applicable to scattering systems.
Comments on ‘‘Dynamics of composites and the K–K relations,’’ A reply to C. M. Sayers
Authors: Beltzer A. I.
Published: October 2005

It is shown that the original formulas [J. Acoust. Soc. Am. 73, 355–356 (1983)] are correct.
Comments on ‘‘Precise model measurements versus theoretical prediction of barrier insertion loss in presence of the ground’’ [J. Acoust. Soc. Am. 7
3, 44–54 (1983)]
Authors: Rasmussen Karsten B.
Published: October 2005

Some of the theoretical curves in the article by J. Nicolas et al. [J. Acoust. soc. Am. 73, 44–54 (1983)] appear to be erroneous.
The effect of random intensity fluctuation on monaural and binaural detection
Authors: Hall Joseph W. , Fernandes Mariano A.
Published: October 2005

Two experiments were performed to determine the effects of random intensity fluctuation on NoSo and NoSπ performance. Noise was used as both signal and masker, and stimuli were bands of noise from either 0–2.0 or 2.0–4.0 kHz. Signal and masker were either coherent (from the same source) or noncoherent (from independent sources). In the first experiment, noise fluctuation was achieved by modulating a wide band of noise. In the second experiment, fluctuation was achieved by narrowing the noise bandwidth. Results from both experiments indicated that NoSo performance was adversely affected by fluctuation and by noncoherent relation between signal and masker. NoSπ detection was not adversely affected by fluctuation at low frequency, and was affected less adversely than was NoSo detection at high frequency. This difference between NoSo and NoSπ performance is an important consideration when making inferences about monaural and binaural processing when the stimuli are fluctuating rather than temporally steady.
The effect of broadband noise on the human brainstem auditory evoked response. I. Rate and intensity effects
Authors: Burkard Robert , Hecox Kurt
Published: October 2005

A series of experiments investigated the effects of continuous broadband noise (ipsilateral) on wave V of the click-evoked brainstem auditory evoked response (BAER). In general, a broadband noise masker increases the latency and decreases the amplitude of wave V. Varying both click and noise intensity, it was found that noise levels above about 40 dB SPL increase the latency and decrease the amplitude of wave V, regardless of click intensity. The effects of noise on wave V amplitude appear constant across click intensity, whereas the effects of a constant noise level on wave V latency decrease at higher click intensities. Both masking and adaptation increase wave V latency, but their combined effects are occlusive: rate-induced wave V latency shift decreases in the presence of continuous broadband noise. The clinical and theoretical implications of these findings are discussed.
The effect of broadband noise on the human brainstem auditory evoked response. II. Frequency specificity
Authors: Burkard Robert , Hecox Kurt
Published: October 2005

A series of experiments evaluated the effects of broadband noise (ipsilateral) on wave V of the brainstem auditory evoked response (BAER) elicited by tone bursts or clicks in the presence of high-pass masking noise. Experiment 1 used 1000- and 4000-Hz, 60-dB nHL tone bursts in the presence of broadband noise. With increasing noise level, wave V latency shift was greater for the 1000-Hz tone bursts, while amplitude decrements were similar for both tone-burst frequencies. Experiment 2 varied high-pass masker cutoff frequency and the level of subtotal masking in the presence of 50-dB nHL clicks. The effects of subtotal masking on wave V (increase in latency and decrease in amplitude) increased with increasing derived-band frequency. Experiment 3 covaried high-pass masker cutoff frequency and subtotal masking level for 1000- and 4000-Hz tone-burst stimuli. The effect of subtotal masking on wave V latency was reduced for both tone-burst frequencies when the response-generating region of the cochlear partition was limited by high-pass maskers. The results of these three experiments suggest that most of the wave V latency shift associated with increasing levels of broadband noise is mediated by a place mechanism when the stimulus is a moderate intensity (60 dB nHL), low-frequency (1000 Hz) tone burst. However, the interpretation of the latency shifts produced by broadband noise for 4000-Hz tone-burst stimuli is made more complex by multiple technical factors discussed herein.
Effective flow resistivity of ground surfaces determined by acoustical measurements
Authors: Embleton T. F. W. , Piercy J. E. , Daigle G. A.
Published: October 2005

Following earlier work by Chessell [J. Acoust. Soc. Am. 62, 825–834 (1977)] it is shown that his single-parameter theory can be used to predict the measured transmission spectra between a source and receiver located above ground surfaces having a wide range of acoustic impedance—or effective flow resistivity. Surfaces behaving essentially as locally reacting range from new-fallen snow, effective flow resistivity σ=10–30 cgs rayls, through grass-covered ground, σ=150–300 rayls, to mature asphalt, σ=30 000 rayls. The thermal-conduction and viscous boundary layer of the surface limits the effective flow resistivity of even the hardest and most impervious surface to the range 105–106 rayls, depending on frequency: this value is appropriate to evaluate the complex reflection coefficient of the paint-sealed surface of a thick slab of reinforced concrete.
Comparison of thermodynamic and finite amplitude methods of B/A measurement in biological materials
Authors: Law W. K. , Frizzell L. A. , Dunn F.
Published: October 2005

The nonlinearity parameter B/A has been determined for various biological solutions and soft tissues using both the thermodynamic and finite amplitude methods. This letter is to show that agreement achieved between the two methods is within a fraction of a percent for liquid samples and within 10% for the soft tissues studied.
Comparison of three methods for measuring acoustic properties of bulk materials
Authors: Smith Charles D. , Parrott Tony L.
Published: October 2005

Three methods for measuring the acoustic properties of bulk materials have been evaluated. The methods differ from one another in their practical implementation and reliability. The two more convenient methods exploit changes in surface impedance of test samples resulting from a change in the test sample geometry or boundary conditions. The results from these surface methods are compared with that obtained using Scott’s method. In Scott’s method the propagation constant is obtained by a ‘‘direct’’ measurement inside the test material by means of a probe tube. The comparisons suggest that the surface methods will provide reliable and accurate results when the test sample behaves as a rigid porous structure.
Discrete-time detection modeling for unsaturated ocean acoustic propagation
Authors: Perakis Anastassios N. , Psaraftis Harilaos N.
Published: October 2005

The basic problem in ocean acoustic detection is formulated under the assumption of unsaturated sound propagation. The latter essentially amounts to a constant signal plus Gaussian noise. Detection is defined as occurring whenever ρ, the root mean square pressure at the receiver, exceeds a specified threshold level ρ0. A two-state, discrete-time Markov model is derived, and closed-form expressions for the probability mass functions of the number of time steps separating two successive detections (interarrival time) or one detection and the first subsequent ‘‘downcrossing’’ (holding time) are presented. Expressions for the joint probability density function of ρ at two different points in time are obtained and used to determine the relevant one-step transition probabilities of the Markov model. Sample results using the model are finally presented.
Vibration of a thick polygonal ring in its plane
Authors: Nagaya Kosuke
Published: October 2005

This paper is concerned with a method for solving vibration problems of polygonal rings. In the analysis, the equation of motion based on the two-dimensional theory of elasticity is applied under the plane strain assumption. The exact solution for the equation of motion is obtained. The boundary conditions along both the outer and the inner surfaces of the polygonal ring are satisfied directly by means of the Fourier expansion collocation method. Numerical calculations are carried out for general triangular, square, pentagonal, and hexagonal rings with sides of equal thicknesses. A rectangular ring with sides of unequal thickness is also investigated to clarify the effects of the difference of the thicknesses.
Determination of the acoustic nonlinearity parameter B/A from phase measurements
Authors: Zhu Zheming , Roos Mark S. , Cobb Wesley N. , Jensen Kurt
Published: October 2005

A technique for measurement of the acoustic nonlinearity parameter B/A in liquids is presented, along with results for several liquids. The nonlinearity parameter is determined by measuring changes in the travel time of ultrasonic tone bursts which are caused by prescribed changes in the ambient pressure. The travel time differences are measured by comparing the phase of the tone burst with that of a reference signal. The measurement is simpler to perform than those previously reported in the literature.
On the oscillations of musical instruments
Authors: McIntyre M. E. , Schumacher R. T. , Woodhouse J.
Published: October 2005

The time-domain description of musical and other nonlinear oscillators complements the more commonly used frequency-domain description, and is advantageous for some purposes. It is especially advantageous when studying large-amplitude oscillations, for which nonlinearity may be severe. It gives direct insight into the physical reasons for the variation of waveform as playing conditions vary, and into certain phenomena which may seem counter-intuitive from the frequency-domain viewpoint, such as the musically undesirable flattening in the pitch of a bowed string when the bow is pressed too hard onto the string. It is easy to set up efficient time-domain simulations on a small computer, a fact that has been surprisingly little exploited in musical acoustics. The simplest relevant model is described here. It demonstrates some of the basic nonlinear behavior of the clarinet, violin, and flute families with very little programming effort. Remarkably, a single set of model equations has relevance to all three cases, at a certain level of idealization, with appropriate choices of parameter values and of linear and nonlinear characteristics. For the flute family, this simplest model gives waveforms and phase relations closely resembling those observed at resonance in the organ-pipe experiments of Coltman [J. Acoust. Soc. Am. 60, 725–733 (1976)], including the triangular pressure and velocity waveforms. It can be shown (again using a time-domain approach) that the triangular waveform is a universal limiting form, independent of detailed acoustic loss mechanisms provided losses are small.
Ultrasonic shear wave properties of soft tissues and tissuelike materials
Authors: Madsen Ernest L. , Sathoff H. John , Zagzebski James A.
Published: October 2005

Determinations of shear wave speeds of sound and attenuation coefficients are reported for soft tissues, a silicone rubber reference material, and a gel used in manufacturing ultrasonically tissue-mimicking materials. Fresh bovine tissues were investigated, including calfskin, liver, cardiac muscle, and striated muscle. Because of the very large shear wave attenuation coefficients, reasonably accurate determinations of shear wave properties are difficult to make. The quantity measured directly was the complex reflection coefficient for shear waves at a planar interface between the sample and fused silica. Measurements were made at frequencies spanning the range 2–14 MHz. The shear wave attenuation coefficients increase with frequency and are of the order of 104 times the longitudinal wave attenuation coefficients. The shear wave speeds of sound also increase with frequency but are only a few percent of the longitudinal wave speeds of sound. The results are accurate enough to allow frequency dependencies to be proposed.
The thermal pulse decay technique for measuring ultrasonic absorption coefficients
Authors: Parker Kevin J.
Published: October 2005

The classic method for measuring absorption coefficients of materials requires a determination of the temperature rise within a medium during ultrasonic irradiation. Serious errors may result from a viscous heating effect around the required thermocouple probe, and from heat lost by conduction to surrounding, cooler regions. A thermal pulse-decay technique is proposed and evaluated which allows for the separation, in time and space, of the viscous heating artifact and the true absorptive heating of a medium. In addition, the pulse-decay method explicitly accounts for heat conduction and the ultrasonic beam patterns used in experiments. The inherent advantages of the new technique allow for an extension of absorption measurements to smaller beamwidths and higher frequencies and intensities than were previously possible.
Response of cochlear nerve fibers to brief acoustic stimuli: Role of discharge-history effects
Authors: Gaumond Roger P. , Kim D. O. , Molnar Charles E.
Published: October 2005

The probability that a cochlear nerve fiber spike discharge occurs during a time interval Δt depends on both the acoustic stimulus and on aftereffects from earlier spike discharges. We have examined the influence of discharge-history on post-stimulus time (PST) histogram responses to acoustic click and tone-burst stimuli. Discharge-history effects were found to include the modification of observed interpeak times of PST responses to clicks, a loss of distinct peaks in the click response of high characteristic frequency (CF > 5 kHz) fibers, and changes in the ratio of initial to steady-state response portions of tone-burst responses. The method used to separate discharge-history from stimulus-related factors is based on a model developed in Gaumond et al. [J. Neurophysiol. 48, 856–873 (1982)]. The results are in general agreement with those obtained by the method of Peter Gray [Biophys. J. 7, 759–777 (1967)], which discards from consideration those portions of the response record not preceded by a silent interval of 20 or 25 ms or more. Our method requires more assumptions about the spike train, but produces less variable results by utilizing more of the spike train data.
Direct and inverse scattering in the time domain via invariant imbedding equations
Authors: Corones J. P. , Davison M. E. , Krueger R. J.
Published: October 2005

This paper examines the implementation of a new approach to direct and inverse scattering problems in the time domain, which is applied here to the case of a one-dimensional lossless medium. The method is based on an integro-differential equation which is satisfied by the reflection kernel and has been derived elsewhere using invariant imbedding techniques. An example of an exact solution to this equation is given. Numerical schemes for solving the direct and inverse problems are derived by discretizing this equation. The behavior of the resulting algorithms is then tested on several examples. The results suggest that the inversion method is stable in the presence of additive noise.
The extreme nearfield of an acoustic diffraction grating
Authors: Ochs R. L. , Maynard J. D. , Williams Earl G. , Hughes W. Jack
Published: October 2005

An expression for the transmitted sound field near (within a fraction of a wavelength) an array of slits is derived under the assumption that the normal component of the particle velocity is the same, in the slits, as if no grating were present and zero everywhere else in the plane of the grating. The expression is in the form of an inverse Fourier transform and can be evaluated quickly using a standard fast-Fourier-transform (FFT) alogrithm. Using this technique, the sound pressure on the axis of symmetry normal to the grating was evaluated for a plane-wave incident at various angles with respect to the normal to the grating, and the results were found to provide an excellent qualitative (and to a significant degree quantitative) description of some experimental measurements. Extensions of the method to oscillating pistons of arbitrary (but planar) configuration in a rigid baffle are indicated.
Acoustic propagation in wall shear flows and the formation of caustics
Authors: Kriegsmann Gregory A. , Reiss Edward L.
Published: October 2005

The propagation of acoustic waves from a high-frequency line source in a two-dimensional parallel shear flow adjacent to a rigid wall is analyzed by a ray method. The leading term in the resulting expansion is equivalent to the geometrical acoustics theory of classical wave propagation. It is shown that energy from the source is radiated either directly to the farfield, or by first reflecting from the wall. In addition, energy is trapped in a channel adjacent to the wall and downstream from the source. The rays in this channel form an infinite sequence of caustics progressing downstream. Since the geometrical acoustics approximation is invalid on and near caustics, a boundary layer method is employed to determine the acoustic fields near the caustics. It is shown that the amplitude of the fields on and near the caustics is k2/3 larger than the geometrical acoustics field for large k. Here k is a dimensionless wavenumber of the source. Moreover, the vorticity of the acoustic fields in the caustic regions is k7/6 larger than the geometrical acoustics field. The possible significance of these results for vehicle self-noise and the formation of turbulent spots in the sublayer of a turbulent boundary layer is discussed.
Reflection, scattering, and absorption of acoustic waves by rough surfaces
Authors: Watson John G. , Keller Joseph B.
Published: October 2005

The first and second moments, i.e., the coherent field and the two-point, two-time correlation function, are calculated for the acoustic fields scattered from various rough surfaces. For each surface they yield the reflection, absorption, and differential scattering coefficients, as well as an equivalent boundary condition for the coherent field. Renormalized coefficients are constructed to eliminate divergences at grazing incidence. The results are specialized to surfaces which are statistically homogeneous in both space and time, and to surfaces consisting of randomly placed bosses on a smooth surface. The surfaces considered are slightly rough, moving, soft or hard boundaries, and flat surfaces with random admittances or impedances. The analysis is based on the regular perturbation method or Born approximation. Comparisons with previous results are made.
Ocean flow measurements using acoustic scintillation
Authors: Clifford Steven F. , Farmer David M.
Published: October 2005

A wave propagating in a medium having random fluctuations in refractive index will suffer phase and amplitude perturbations. In the receiving plane, a random interference pattern will appear and this so-called scintillation pattern will vary in time for two reasons: (1) the decay of the refractive-index fluctuations producing the amplitude perturbation (eddy decay) and (2) advection of the eddies by the flow. In the case where eddy lifetimes are long compared with the scintillation period, we can derive estimates of flow from a statistical analysis of the scintillation pattern. In this paper, we discuss the propagation theory and report measurements of oceanic flows by analysis of the acoustic scintillation pattern produced by the density fluctuations in the ocean. By mounting a 214-kHz source and two receivers on opposite sides of a barge such that the axis of propagation is perpendicular to the direction of travel, we induce a known flow rate equal to the barge velocity. We compute the slope of the time-lagged covariance function of the logarithm of the amplitude at the two detectors. The slope is proportional to the path-averaged flow transverse to the propagation path. Simultaneous measurements with a current meter provide sea truth. We have shown that such a technique will measure flow velocity with reasonable accuracy. An interesting result of the measurements is the demonstration that sound speed fluctuations in the spatial window 15–30 cm satisfy the Kolmogorov spectral slope for an inertial subrange, at the shallow depth (2.1 m) of the observation.
Augmented adiabatic mode theory for upslope propagation from a point source in variable-depth shallow water overlying a fluid bottom
Authors: Pierce Allan D.
Published: October 2005

A uniform asymptotic solution is presented for sound propagation from a constant frequency point source in shallow water whose depth H(r) decreases monotonically with cylindrical distance r. The water has constant sound speed c1 and density ρ1; the bottom fluid extends indefinitely in depth and has sound speed c2 and density ρ2, where c2>c1. The interface depth has constant value H0 up to range r0 and thereafter decreases linearly to zero. The solution appears as a sum of modal terms, each such mode eventually encountering a critical depth Hc(n) (at which modal phase velocity equals c2) at a critical range rc(n). A previously derived local solution for a modal term near its critical range is modified such that it automatically reduces to the adiabatic mode solution at nearer ranges and such that it is valid at arbitrary distances beyond the critical range. Bulk attenuation is incorporated into the model using an appropriate modal average over depth. Numerical results are compared with four parabolic equation computations supplied by Jensen. In these four cases only single mode propagation is considered and r0 is 0. The two theories agree well, with discrepancies typically less than 1 dB. Additional comparisons with parabolic equation computations (simultaneous propagation of three and two modes) presented by Jensen and Kuperman [J. Acoust. Soc. Am. 67, 1564–1566 (1980)] show comparable agreement, but for the higher modes there are marked discrepancies in the directions at which sound is beamed into the bottom fluid from regions encompassing those mode’s critical ranges. This is attributed to the progressive deterioration of the present theory with increasing mode number.
Discrimination of envelope frequency
Authors: Buus So/ren
Published: October 2005

Discrimination of envelope frequency was measured as the just noticeable increase in envelope frequency of monotic, 60-dB two-tone complexes at geometric center frequencies (CFs) of 500, 1000, 2000, and 4000 Hz. (The envelope frequency is equal to the frequency separation ΔF, between the two components.) At a given CF the jnds were approximately constant up to a critical envelope frequency between 10% and 20% of the CF, roughly equivalent to the critical band, beyond which they increased to a maximum at about 40% of the CF. Below the critical envelope frequency, the jnd increased with CF. Measurements at 40 dB SPL with and without masking of the aural distortion products showed that the influence of aural distortion is minimal. Additional measurements showed that at narrow frequency separations, discrimination was better for monotic two-tone complexes than for pure tones, three-tone complexes, and dichotic two-tone complexes. The results indicate that envelope frequency may serve as a cue for discrimination up to a frequency between 30% and 40% of the CF, although its effectiveness at high enevelope frequencies is severely diminished by the auditory filter. A comparison with other data on envelope frequency discrimination indicates that the jnds’ dependence on the envelope frequency may depend on how the slope of the temporal envelope varies with envelope frequency.
Simulation of auditory analysis of pitch: An elaboration on the DWS pitch meter
Authors: Scheffers Michael T. M.
Published: October 2005

A model was developed for estimating the pitch of complex sounds that are partially masked by background sound. Our ultimate aim is to obtain a model that can separate two simultaneous sounds on the basis of the harmonic structure of at least one of the sounds. The MDWS model is an extension of the Duifhuis, Willems, and Sluyter pitch meter (DWS) [J. Acoust. Soc. Am. 71 1568–1580 (1982)] which is a practical implementation of Goldstein’s optimum processor theory of pitch perception [J. Acoust. Soc. Am. 54, 1496–1516 (1973)]. The main modifications incorporated in MDWS consist of a more faithful modeling of auditory frequency analysis and of an alteration to the criterion used to decide which fundamental best fits a set of resolved components. Effects of the latter modification were investigated in a comparison between model estimates of the pitch of inharmonic complex signals and results obtained for humans. Furthermore, the accuracy of model estimates of the pitch of periodic signals (among which were synthesized vowel sounds), partially masked by noise, was compared with the just noticeable difference of fundamental frequency of these sounds for human observers. The results of these two tests show that the model estimates come close to human perception.
The relationship between the cross-correlation coefficient of two-channel acoustic signals and sound image quality
Authors: Kurozumi Kohichi , Ohgushi Kengo
Published: October 2005

In order to investigate sound image quality, white and bandlimited noises with various cross-correlation coefficients are reproduced from two loudspeakers placed in anechoic or echoic chambers. Subjects are asked to make similarity judgments and some subjective evaluations of pairs of the noises. The experimental data are analyzed by Kruskal’s multidimensional scaling (MDS) program. The analysis of the experimental data shows the following: (1) sound image quality depends mostly on the width and the distance of the sound image, (2) the width of the sound image depends on the absolute value of the cross-correlation coefficient, (3) the distance of the sound image depends on the cross-correlation coefficient itself, (4) with respect to physical and psychological factors governing sound image quality, there is no fundamental difference between anechoic and echoic chambers.
The effective nonlinearity parameter for immiscible liquid mixtures
Authors: Apfel Robert E.
Published: October 2005

A relation has been derived which gives the effective nonlinearity parameter of a system of immiscible liquids, given the individual nonlinearity parameters as well as the respective densities, compressibilities, and volume fractions in the mixture.
Theoretical prediction of a backscattering maximum at Rayleigh angle incidence for a smooth liquid–solid interface
Authors: Ngoc Tran D. K. , Mayer Walter G.
Published: October 2005

A numerical integration method for the description of acoustic bounded beams is used to calculate possible backscattering strength from a smooth liquid–solid interface. It is shown that the backscattering strength is maximum for Rayleigh angle incidence. The influence of beam shape and beamwidth on the backscattering strength near the maximum is demonstrated.
Growth rate of loudness, annoyance, and noisiness as a function of tone location within the noise spectrum
Authors: Hellman Rhona P.
Published: October 2005

The relation between overall perceived magnitude (loudness, annoyance, and noisiness) of noise-tone complexes and the location of the tone within the spectrum was investigated by absolute magnitude estimation (AME). Single tones at 250, 1000, 2000, and 3000 Hz were added to low- and high-pass noises. In contrast to noisiness, loudness and annoyance growth behavior depends on the relationship between the frequency of the added tone and the spectral shape of the noise. Tones centered in noise produce nonmonotonic loudness and annoyance growth functions; those added to the skirt produce power functions. The measured exponents are invariant across tone-to-noise ratio when the tones are positioned within the spectrum, but not when they are added to the skirt. Moreover, for complexes at approximately the same overall SPL, the tone’s position determines the functional relationship between loudness (or annoyance) and tone-to-noise ratio. Although a tone correction for annoyance is warranted for certain noise-tone configurations, none of the proposed calculation procedures considers all the variables relevant to perceived annoyance of tonal components. To a large extent, complex auditory interactions generated by the simultaneous presentation of noise and tone can account for the observed effects.
Perception of sine-wave analogs of voice onset time stimuli
Authors: Hillenbrand James
Published: October 2005

It has been argued that perception of stop consonant voicing contrasts is based on auditory mechanisms responsible for the resolution of temporal order. As one source of evidence, category boundaries for nonspeech stimuli whose components vary in relative onset time are reasonably close to the labeling boundary for a labial stop voiced–voiceless continuum. However, voicing boundaries change considerably when the onset frequency of the first formant ( F1) is varied—either directly or as a side effect of a change in F1 transition duration. Stimuli consisted of a midfrequency sinusoid that was initiated 0–50 ms prior to the onset of a low-frequency sinusoid. Results showed that the labeling boundary for relative onset time increased for longer durations of a low-frequency tone sweep. This effect is analogous to the F1 transition duration effect with synthetic speech. Further, the discrimination of differences in relative onset time was poorer for stimuli with longer frequency sweeps. However, unlike synthetic speech, there were no systematic effects when the frequency of a transitionless lower sinusoid was varied. These findings are discussed in relation to the potential contributions of auditory mechanisms and speech-specific processes in the perception of the voicing contrast.
Comments on ‘‘Acoustic radiation pressure produced by a beam of sound’’ [J. Acoust. Soc. Am. 7
2, 1673–1687 (1982)]
Authors: Nyborg Wesley L. , Rooney James A.
Published: October 2005

Chu and Apfel discuss the radiation-pressure theory for one-dimensional fields and the confusion that presently exists. The ‘‘Rayleigh’’ situation involving a laterally confined beam is one presenting doubt and in need of clarification.
Profile of laser-produced acoustic pulse in a liquid
Authors: Sullivan B. , Tam A. C.
Published: October 2005

Recently, Lai and Young [J. Acoust. Soc. Am. 72, 2000 (1982)] and Heritier [Opt. Commun. 44, 267 (1983)] have independently calculated the profile of a thermo-elastically generated opto-acoustic pulse due to the passage of an excitation laser pulse of certain spatial and temporal intensity distributions in a weakly absorbing medium. We have found that their results are essentially equivalent for Gaussian intensity distribution of the excitation laser. We report the first experimental verification of such theoretical opto-acoustic profiles excited by laser pulses of various pulse widths τFWHM (8 ns and 1.3 μs) focused to different beam waists w0. Our observation of the profile is performed with a probe beam deflection technique instead of using conventional acoustic transducers which have limited rise times and nonflat frequency response. Our results are in reasonable agreement with theory, and clearly indicate that sharp opto-acoustic pulses can be generated by laser pulses of short τFWHM and small w0.
Effects of traffic noise on quality of sleep: Assessment by EEG, subjective report, or performance the next day
Authors: Wilkinson Robert T. , Campbell Ken B.
Published: October 2005

Twelve people living in areas of high traffic noise were studied to assess its effect on their sleep. During 3 weeks, their sleep was monitored physiologically in the natural setting of their own bedrooms. Their performance and subjective report of sleep were recorded each day. For the middle week, the bedroom windows were double glazed to reduce the prevailing level of traffic noise at the bedside (Leq 46.6 dB(A) over the whole night) by an average of 5.8 dB(A). Most physiological measures were unaffected by the noise reduction, but stage 4 sleep and low-frequency, high-amplitude delta waves in the EEG, both thought to be signs of deep sleep, were increased. Also unprepared simple reaction time, a test sensitive to drowsiness, was improved the next day, whereas a more stimulating short term memory test was not. Subjects also reported sleeping better. These improvements with double glazing were all modest in degree, but as they occurred in three independent and predicted measures of sleep quality, the view is supported that the prevailing level of traffic noise does indeed impair sleep.
Reflection and transmission of obliquely incident Rayleigh waves by a surface-breaking crack
Authors: Angel Y. C. , Achenbach J. D.
Published: October 2005

Reflection, transmission, and scattering of Rayleigh waves that are obliquely incident on a surface-breaking crack are investigated. The formulation of the problem has been reduced to two systems of singular integral equations of the first kind for the dislocation densities across the crack faces. The systems of integral equations are solved numerically. Substitution of the dislocation densities into appropriate representation integrals yields the reflected and transmitted surface waves. Reflection and transmission coefficients are plotted versus the angle of incidence for various values of the frequency and versus the frequency for various values of the angle of incidence. A critical angle of incidence, which depends on the material properties of the solid, has been observed. Beyond this angle no mechanical energy is radiated into the solid by body waves.
Acoustic radiation from vibrating surfaces at characteristic frequencies
Authors: Piaszczyk Christopher M. , Klosner Jerome M.
Published: October 2005

The application of boundary integral methods to the problem of acoustic radiation suffers from nonexistence or nonuniqueness problems at the characteristic frequencies of the associated interior Dirichlet problem. To overcome this difficulty, an iterative overdetermination scheme is developed. First, the surface integral Helmholtz equation is discretized, and at noncharacteristic frequencies, the resulting system of linear algebraic equations can be solved directly, yielding the values of the acoustic pressure at the boundary nodal points. At characteristic frequencies, the system matrix becomes ill-conditioned and the direct solution is not possible. An approximate surface impedance function is then assumed to serve as a basis for the computation of approximate farfield pressures. These are then utilized to form an overdetermined system, which is solved with the least-squares procedure. This solution can be used to compute the next-order approximation, and the process is continued. The method is applied to the cylindrical transducer problem and proves to yield good results at characteristic frequencies. It is also used to solve a structural radiation problem, for which no characteristic frequencies are found. Nonexistence of such frequencies for problems of this type is conjectured, although no general proof is given.
Diffraction effects in surface acoustic wave harmonic generation
Authors: Palma F. , Socino G.
Published: October 2005

Fourier analysis method has been applied to model the diffraction integral of the second harmonic field nonlinearly generated by a surface acoustic wave beam. Cross-section profiles of the second harmonic field have been calculated at different longitudinal positions along an acoustic beam propagating on a yz-LINbO3 crystal. Theoretical curves are reported together with experimental results relative to the case of a fundamental wave emitted by a 24-wavelengths-wide transducer at the frequency of 35 MHz. A theoretical determination of the energy loss produced by diffraction effects in second harmonic generation is performed by evaluating the acoustic energy of the second harmonic wave over cross sections of the acoustic beam and by normalizing these quantities to the ones relative to plane wave propagation. Diffraction loss in isotropic and anisotropic materials has been calculated as a function of the longitudinal position along the beam axis for different directivities of the source. A generalized diffraction loss curve is reported, which takes different beam directivities and different anisotropy parameters into account for the case of isotropic media and of anisotropic media with parabolic velocity surfaces.