bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on the spatial variation of decaying sound fields
Authors: Bartel Thomas W. , Magrab Edward B.
Published: October 2005

The spatial variation of the reverberation time was measured in the NBS reverberation room in the 1/3-octave bands from 80 to 10 000 Hz to determine the following: (1) the effects on the precision of the spatially averaged reverberation time due to (i) vane speed and vane orientation, (ii) loudspeaker location, and (iii) the area and location of an absorbing panel and its absorption coefficient; (2) the selection of the parameters in (1) above such that the measurement uncertainty of the reverberation time is minimized; and (3) the overall measurement uncertainty for this optimum configuration as a function of the number of microphone locations and the number of decay curves recorded at each microphone location. For an 11-m2 panel with relatively little low frequency absorption and with the vanes oriented at 22.5° from the vertical and rotating at 7.5 rpm, an analysis of variance indicated that the total uncertainty of the measured average reverberation time (one standard deviation from the mean) was less than 0.5% from 160 to 4000 Hz and less than 1.5% from 80 to 10 000 Hz when 20 decays at each of six microphone locations were used.
Statistical estimation of percentage of overexposed workers
Authors: Ungar Eric E. , Cruikshank Donald B.
Published: October 2005

A method is outlined for estimating, from a statistical sample of exposure times and noise levels, the percentage of noise-impacted workers who are overexposed according to the OSHA regulation.
Responses of the cat’s collicular auditory neuron to human speech
Authors: Watanabe Takeshi , Sakai Hisao
Published: October 2005

Collicular auditory neurons in cats were exposed to human speech sounds, and responses to the vowel /a/ in isolation and in connected speech were compared. The fundamental frequency coded was found to be independent of CF, response type (’’on’’ type or slowly adapting), and directional sensitivity to frequency change. This suggests that the coding of speech sounds depends on the periodicity of the neural-response pattern. Responsiveness was generally greater to segmented vowels; it seems probable that a neuron’s response adapts to and is suppressed by preceeding speech stimuli. The context in which a message is embedded may be very important for the processing of speech sounds.
Motor unit correlates of stress: Preliminary observations
Authors: Sussman Harvey M. , MacNeilage Peter F.
Published: October 2005

Motor unit activity was measured during 20 repetitions of [aep ] and 20 repetitions of [aep ] with emphatic stress placed on the second syllable. A definite pattern of recruitment and discharge reorganization was observed during stressed productions characterized by (1) an increase in motor unit discharge rate, (2) recruitment of additional motor units, (3) a reduction in time intervals separating successively activated motor units, (4) an earlier onset of mandibular lowering for the open vowel in relation to initiation of motor unit activity, (5) fewer discharges of a given motor unit per utterance, and (6) sharply reduced variability in recruitment intervals. The shortened and highly stable latencies between motor unit events and motor unit-articulator events point to a more carefully orchestrated motor program for heavily stressed productions as a more forceful attainment of target specification is carried out.
New approach to a constant beamwidth transducer
Authors: Rogers Peter H. , Van Buren A. L.
Published: October 2005

The theory of a broadband constant beamwidth transducer which is to be used primarily as a projector is presented. The transducer is a spherical cap of arbitrary half angle α shaded so that the normal velocity is equal to U0Pν(cos ϑ), where Pν is the Legendre function whose root of smallest angle occurs at ϑ=α. The required value for ν, the order of the Legendre function (which is not, in general, an integer) can be obtained to within 1% for α?1 radian from the approximation ν?0.5[(4.81/α)−1]. The transducer is shown to have uniform acoustic loading, extremely low sidelobes, and an essentially constant beam pattern for all frequencies above a certain cutoff frequency. Under piezoelectric drive the transducer is shown to have a flat transmitting current response over a broad band.
Perceptibility of phonetic features in fluent speech
Authors: Cole Ronald A. , Jakimik Jola , Cooper William E.
Published: October 2005

A series of experiments examined listeners’ ability to detect mispronounced words in a short story. Mispronunciations were produced by changing a single consonant segment in a word to produce a (phonologically permissible) nonsense word. The results of six different experiments showed that prestressed word-initial stop consonants are more perceptible than other consonants. For example, mispronunciations produced by changing the voicing of a word-initial stop (e.g., ’’boy’’ to ’’poy’’) were detected about 70% of the time, while changes in voicing of a word-initial fricative (e.g., ’’voice’’ to ’’foice’’) were detected about 38% of the time. Mispronunciations produced by changing the place of articulation of a prestressed word-initial stop were most detectable of all (80% to 90% detection) for three different speakers. A change in place of articulation of a word-initial stop (e.g., ’’baby’’ to ’’daby’’) was detected as often as a change in both place of articulation and voicing (e.g., ’’baby to ’’taby’’). Finally, it was found that a mispronunciation was detected about twice as often in word-initial than in word-final position in one syllable words for both stops and nasals. The results suggest that listeners pay special attention to word-initial stop consonants in natural continuous speech.
Effects of transition length on the perception of stop consonants
Authors: Keating Patricia , Blumstein Sheila E.
Published: October 2005

This study investigated the effects of lengthened transitions on the perception of stop consonants. In experiment I, three continua representing the phonetic categories [da] and [ga] containing transitions of 45, 95, or 145 ms were presented to 20 subjects for both labeling and discrimination. Results indicated that although there was a significant change in identification performance from 95 to 145 ms, the shape of the functions, and the locus and slope of the phonetic boundary did not significantly vary across transition lengths. In addition, discrimination of within-category stimulus comparisons was significantly better at the 95-ms transition length than at 45 or 145 ms. In experiment II, the availability of acoustic information was investigated further with the adaptation paradigm. Eight subjects labeled the 45-ms series before and after adaptation with 45-, 95-, and 145-ms [da] stimuli. No effect of transition length was found. These results suggest that the slope and duration of formant transitions seem to contribute minimally to the perception of place of articulation in stop consonants.
Indirect assessment of the contribution of subglottal air pressure and vocal-fold tension to changes of fundamental frequency in English
Authors: Monsen Randall B. , Engebretson A. Maynard , Vemula N. Rao
Published: October 2005

The contributions of vocal-fold tension and of subglottal air pressure to changing fundamental frequency F0 are indirectly assessed by comparing human glottal-source data with synthetic glottal waveforms generated by the Ishizaka–Flanagan two-mass model of vocal-fold vibration. In this model, synthetic male and female glottal waves may be generated with known values of subglottal air pressure and vocal-fold tension. Human glottal waves were recorded with a reflectionless tube into which ten male and female adults phonated. The subjects produced interrogative (rising F0) and declarative (falling F0) glides and trisyllabic words with primary stress on the initial, medial, or final syllable. Two types of change in the glottal wave over time are possible, depending on whether F0 is changed primarily by vocal-fold tension or by subglottal air pressure. Comparison of the natural and synthetic glottal waves indicates that (1) the rise of frequency in interrogative words is due principally to increasing vocal-fold tension, while (2) the fall of frequency in declarative words is due principally to decreasing subglottal air pressure; (3) in the polysyllabic words, the change of frequency within syllables resembles that of the declarative monosyllables and appears due primarily to changes of subglottal air pressure; and (4) the heightened f0 of the stressed syllable is due to an increase in the vocal-fold tension, typically accompanied by increased subglottal air pressure.
Elastic waves in rods and clad rods
Authors: Thurston R. N.
Published: October 2005

Clad rods have been investigated for use as long delay lines because they offer isolation of the signal from the surface and low dispersion. In addition, single-mode propagation is achieved with a larger (and hence more conveniently transduced) cross section than is possible with a homogeneous rod at the same frequency. This paper describes the modes that have a steady-state sin(ωt−βz) dependence on (t,z), with emphasis on the modes and ranges of parameters that are of interest for delay lines. Only rods of circular cross section, and isotropic, linear elastic materials are considered. Attention is drawn to correspondences with homogeneous rods and with the hypothetical case of infinite thickness cladding, which is most useful as a model for understanding the behavior of corresponding modes in an actual clad rod. Written for the nonspecialist, the paper includes a tutorial review of the concepts and results needed to understand wave propagation in rods and clad rods. In addition, the following new results are reported: (1) for homogeneous rods, a representation of the lowest flexural mode dispersion curve that is for practical purposes independent of Poisson’s ratio; (2) for homogeneous rods, displacement distributions of the first three high-frequency shear modes, i.e., the ’’flexural’’ modes that are asymptotic to the shear velocity (it was found that the distribution previously attributed to the lowest such mode actually belongs to the next); (3) for clad rods, the first demonstration of interface modes of the Stoneley type for nonaxially symmetric waves; (4) classification of clad rods according to the nature and ordering of their asymptotic velocities showing that there are eight types of clad rod, rather than four as stated in the previous literature; (5) for infinitely clad rods having the same shear modulus, proof that the dispersion of torsional waves and their penetration into cladding are universal functions of f/fc∞. The ratio of the shear velocities of the two materials affects the cutoff frequency fc∞, but not the universal penetration and dispersion functions. Subjects on which significant tutorial or descriptive material is given include typical waveguide dispersion, characteristic velocities of an isotropic elastic material, the effect of coupling of dilatational and shear waves at a boundary, waves in homogeneous rods, the connection of isolation to total internal reflection (with Love waves and SH waves in a clad plate as an example), Stoneley waves at a plane interface, and previous results on the clad rod.
Subharmonic vibrations of order 1/3 in stretched strings
Authors: Raghunandan C. R. , Anand G. V.
Published: October 2005

Subharmonic vibrations of order 1/3 in stretched strings driven by a single-mode planar simple harmonic force are investigated. It is shown that both planar and nonplanar subharmonic resonances can occur. Subharmonic vibrations are possible only if the amplitude of the force exceeds a certain critical value which depends upon the magnitude of the damping coefficient. The stability of the solution is analyzed, and it is shown that the region of stable nonplanar vibrations is wider than that of stable planar vibrations. It is also observed in the case of nonplanar vibrations that the amplitude of the subharmonic in the plane normal to the plane of the driving force is larger than that in the plane of the driving force.
Generation of ultrasound at metal–electrolyte interfaces
Authors: Borsay Frank , Yeager Ernest
Published: October 2005

When a radiofrequency potential is applied to an electrode such as gold in an electrolyte, ultrasound is generated at the interface. This effect is attributed to changes in the volume of the solution adjacent to the metal and can be used to study the structure of the interface. Preliminary measurements are reported as a function of the dc electrode potential.
Parametric receiving array and the scattering of sound by sound
Authors: Truchard J. J.
Published: October 2005

The scattering of interaction-frequency components from two sound waves interacting at a nonzero angle has been the subject of controversy for the last two decades. This paper attempts to provide better understanding of the problem by discussing the relationship found between the scattering of sound by sound and the parametric receiving array. First, the solution for a high-frequency plane wave interacting with a low-frequency plane wave over a half space is discussed. The high-frequency sound wave is assumed to originate at a planar boundary and to propagate away from it. Then the interaction-frequency components at some distance from this planar boundary are found. When this solution is related to a solution for a parametric receiving array with a low-frequency plane signal wave and a high-frequency narrowbeam pump wave, the two solutions are found to have very similar properties. Some experiments, as well as solutions, for various configurations of the parametric receiving array are discussed in light of the problem of scattering of sound by sound. Finally, some of the foibles associated with measurements of two interacting waves are described with the aid of the theoretical model for the parametric receiving array. In this paper interaction components are found to exist even when the two sound waves do not propagate in the same direction. It will also be shown that points exist along the nulls of the pump beam patterns where the one primary sound wave is zero and the interaction components are nonzero.
Impulsive discharge noise: Balloon burst problem and engine exhaust pulses
Authors: Kulkarny V. A.
Published: October 2005

Two cases of impulsive discharge, balloon burst and engine exhaust, are experimentally investigated to find scaling laws for the discharge time τ and the pressure amplitude A of the acoustic pulse. Observations show that the flow may be modeled as a pressure reservoir of dimension D and overpressure Δp suddenly discharging through an aperture growing with time. If W is a characteristic aperture velocity, the aperture area varies as (Wτ)2 for the balloon burst and as Wτ for the engine exhaust. The flow is driven by a complex, unsymmetric wave field within the volume. It is shown that D/τ∝ (CiW2)1/3 and A/Δp∝ (Ci/W)4/3 for the balloon burst, where Ci is the sound speed in the reservoir. The corresponding quantities for the engine exhaust pulses are (CiW)1/2 and Ci/W.
Theory of binaural interaction based on auditory-nerve data. IV. A model for subjective lateral position
Authors: Stern Richard M. , Colburn H. Steven
Published: October 2005

A model for the subjective lateral position of 500-Hz tones is presented and compared with experimental lateralization data. Previous papers in this series have explicitly described the auditory-nerve response to these stimuli and proposed a binaural displayer that interaurally compares the auditory-nerve firing times. The outputs of the displayer are postulated to represent the only information about detailed firing times that is available to the brain. In the present paper, lateral-position predictions are obtained by a central nonoptimal weighting of these outputs that depends on the interaural intensity difference of the tone. These predictions describe the results of lateralization-matching experiments more accurately and over a wider range of stimulus conditions than previous theories, except for those results which suggest that low-frequency binaural tones can generate multiple perceptual images. The predictions of our model are also consistent with the results of centering and laterality-comparison experiments. It is argued that the data discussed in this paper are generally incompatible with theories that propose a peripheral interaction of interaural timing and intensity information such as the latency hypothesis.
Behavioral, compound action potential, and single unit thresholds: Relationship in normal and abnormal ears
Authors: Dallos P. , Harris D. , Özdamar Ö. , Ryan A.
Published: October 2005

Comparisons were made for two species (chinchilla and mongolian gerbil) among mean behavioral audiogram, mean just detectable action potential (AP) responses to tone bursts, and single-fiber response thresholds at the characteristic frequency, averaged in one-octave bands. In normal animals and in a group of Kanamycin-treated chinchillas, these mean measures appear to have a well-ordered relationship. Unit and AP thresholds are within 10 dB from one another throughout the frequency range. Behavioral thresholds are usually 15–20 dB more sensitive, but the three curves are roughly parallel except at the highest frequencies, where the behavioral threshold begins to increase approximately one-half octave above the physiological ones. Individual examples for four gerbils and four chinchillas having hair cell losses due to Kanamycin intoxication reinforce the notion based on mean data that in most cases AP thresholds can serve to predict the behavioral threshold configuration.
Detection of LPM signals with estimation of their velocity and time of arrival
Authors: Hodgkiss W. S.
Published: October 2005

The Bayes optimal detector is derived for a class of linear-period-modulated (LPM) signals whose velocities and times of arrival are uncertain. All terms necessary for claculating the a posteriori probability-density function of the uncertain parameters are shown to be available as a natural by-product of the optimal detector computations. The processor structure derived is general in that a priori knowledge of velocity and time of arrival other than complete uncertainty can be taken into account.
Reverberation time, absorption, and impedance
Authors: Dowell E. H.
Published: October 2005

A rigorous theoretical model is derived and used to calculate reverberation time of a room in terms of impedance of absorption materials on the wall and geometrical factors associated with such materials and the room. In addition, the reverberation time also depends upon the initial state of the pressure field before decay begins as well as on the single measure of pressure, for example spatial root mean square, used to characterize the decay-time history. The theoretical model, which consists of a system of harmonic oscillators with damping provided through the wall impedance, is sufficiently general to take into acount all of these factors. Numerical examples are given to illustrate the procedure. A brief review of other methods for calculation of reverberation time is given, including a discussion of random and normal absorption coefficients.
Phase locking in monaural and binaural medullary neurons: Implications for binaural phenomena
Authors: Crow Glenn , Rupert Allen L. , Moushegian George
Published: October 2005

The synchrony of neural impulses in response to low-frequency sinusoids is described for auditory medullary neurons. The results are summarized as follows: (1) In general, neural synchrony is found to improve with increases in intensity and frequency of stimulation for both monaural and binaural neurons when measurements are made in absolute time. (2) An analysis of our population of neurons implies that two separate mechanisms are responsible for the decrease in synchrony found in many neurons as compared to primary-like neurons with high-locking ability. The two mechanisms are convergence of mistimed impulses and electrontonic changes which occur in dendrites. (3) An analysis of binaural vector strength data provides an explanation for physiological differences between cyclic and noncyclic vector strengths as a function of interaural time and reveals the effects of mistimed convergence upon neural synchrony. (4) In contrast to the inferior colliculus, where the neurons discharge best with contralateral leads in time, superior olivary neurons exhibited no such preference. Some discharge best to ipsilateral while others to contralateral leads. This comparison reveals a striking difference in the coding characteristics of medullary and inferior colliculus neurons. (5) Finally, the results are compared with the psychophysically determined difference limens.
Dispersive effects in wave propagationin thin-walled elastic tubes
Authors: Moodie T. Bryant , Haddow J. B.
Published: October 2005

A simple procedure, based on Love’s approximate theory [The Mathematical Theory of Elasticity (Cambridge U. P., Cambridge, England, 1927), 4th ed.] for wave propagation in a bar, is proposed in order to consider dispersive effects in wave propagation in a thin-walled, fluid-filled, elastomer tube. It is assumed that the perturbation from steady flow in the tube is small enough that a linearized theory is valid, and that the elastic modulus of the tube is small compared with the bulk modulus of the fluid so that compressibility of the fluid can be neglected. The flexural rigidity of the tube wall, the inertia of the tube wall, and the radial inertia of the fluid are taken into account, and an approximate expression for the dispersion relation for the fundamental mode is obtained. In order to investigate the dispersive effects, resulting from inclusion of the inertia and flexural rigidity of the tube wall and the radial inertia of the fluid in the model, an initial value problem is considered in detail. The fast Fourier transform is used to obtain numerical solutions for small and intermediate times. Numerical results are presented in graphical form.
Statistics of normal mode amplitudes in a random ocean. II. Computations
Authors: Dozier L. B. , Tappert F. D.
Published: October 2005

In an earlier article [J. Acoust. Soc. Am. 63, 353–365 (1978)], the authors presented a statistical theory of acoustic propagation in a canonical-model random ocean, valid in the limit of low acoustic frequency. Here, numerical predictions of the theory are evaluated and compared to the results of a large-scale Monte Carlo computer simulation. At each of the acoustic frequencies 50, 100, 200, 500, and 1000 Hz, 100 independent realizations of the random acoustic model are obtained. Sample statistical moments indicate that, at least up to 200 Hz, the theoretical predictions are quite accurate. For 500 Hz and above the theory breaks down, as expected for sufficiently high acoustic frequency.
Depth dependence of ambient noise in the northeastern Pacific Ocean
Authors: Morris Gerald B.
Published: October 2005

Omnidirectional ambient noise levels were measured at two deep-water locations in the northeastern Pacific Ocean. Hydrophones were positioned throughout the water column at depths ranging from about 200 m below the surface to about 150 m above the sea bottom. Analyses of the data over the frequencies from 15 to 800 Hz show that at low frequencies the noise levels decrease with increasing depth. The decrease with depth is greater below the critical depth than it is in the sound channel. These low-frequency noise levels, and their depth dependence, are independent of the wind speed. At higher frequencies the noise levels and the depth dependence are controlled by the wind-generated noise. At low wind speeds there is a decrease in levels below the critical depth, but above this depth both increases and decreases in levels with depth were noted. At these high frequencies during high wind speeds the noise levels not only rise, but also fill the water column to the extent that there is little decrease in level with increasing depth, even for the region below the critical depth.
Low-frequency sound propagation in the marginal ice zone of the Greenland Sea
Authors: Numrich S. K.
Published: October 2005

Acoustic propagation measurements were made within the boundary region which separates the open water of the Greenland Sea from consolidated Arctic pack ice. A shallow 29-Hz cw source was towed through the boundary region and into the pack ice while a second ship positioned just outside the ice received the signals on shallow hydrophones. Sound originating under heavy pack ice and propagating across the ice boundary was received at the edge of the open water. The received signals sustained relatively low transmission losses. This indicates that the sound traveled primarily through a shallow surface duct. Somewhat higher losses were recorded for signals propagating between the boundary region and open water. The overall results attest to favorable propagation conditions for low-frequency sound in the cold- water environment particularly when both source and receiver are near the surface. The effect of a changing ice environment and consequent limitations to surface duct propagation are considered.
Timbre discrimination in musical patterns
Authors: Grey John M.
Published: October 2005

Most research on timbre perception has studied isolated tones. This study compares timbre discrimination of isolated tones with discrimination in various musical contexts, both single-voiced and multivoiced. Twelve different contexts were used (four isolated tonal comparisons, four single-voice musical patterns, and four multivoice patterns). Listeners judged whether the timbre remained the same or changed during the trial. Two possible versions of any instrumental timbre differed in the physical information used in thier synthesis. Three instrumental timbres were tested in all contexts: clarinet, trumpet, and bassoon. The effects of context upon discrimination varied across instruments. The clarinet and trumpet versions were best discriminated in isolated contexts, with discrimination progressively worse in single-voice and multivoice patterns. The bassoon versions were best discriminated in the single-voice patterns, with equal discrimination in the isolated and multivoice cases. It is suggested that these results were due to pronounced physical differences observed between the spectra of the two versions of the bassoon that were not apparent between the versions of the clarinet or trumpet.
Dynamic stability of annular plates under periodic radial loads
Authors: Tani J. , Nakamura T.
Published: October 2005

The dynamic stability of clamped annular plates of which both the edges are subjected to the same periodic radial loads is studied theoretically. The Galerkin procedure is used to reduce the problem to that for a finite degree-of-freedom system, the stability boundaries of which are determined by utilizing Hsu’s result for coupled Hill’s equations. For three typical annular plates, the instability regions of both principal and combination resonances are determined for a wide range of exciting frequencies with the effect of static compressive forces taken into consideration. It is found that the principal resonance is of most practical importance, but that of combination cannot be neglected when the static compressive force is applied.
Perturbation theory for linear electroelastic equations for small fields superposed on a bias
Authors: Tiersten H. F.
Published: October 2005

A perturbation formulation of the equations of linear piezoelectricity for small fields superposed on a bias is obtained from a Green’s function representation. It is shown that the resulting equation for the first perturbation of the eigenvalue may be obtained without the use of a Green’s tensor or a complete set of orthogonal eigensolutions. Since the bias enters the constitutive equations, the boundary conditions contain perturbation terms as well as the differential equations. The linear electroelastic equations for small fields superposed on a bias differ from the equations of linear piezoelectricity because the effective material constants of linear electroelasticity have less symmetry than the constants of linear piezoelectricity. Consequently, a perturbation formulation of the linear electroelastic equations for small fields superposed on a bias is presented. It is shown that the effective constants of linear electroelasticity have just the symmetry required for the condition of the orthogonality of linear electroelastic vibrations to hold.
Rayleigh wave dispersion in the cold-worked layer of used railroad rail
Authors: Bray Don E. , Egle Davis M. , Reiter Leon
Published: October 2005

The first shear mode (Sezawa mode) and the fundamental Rayleigh mode have been identified as they propagated through the work-hardened layer on the top surface of used, steel railroad rail. Longitudinal wave velocities and densities are very nearly equal for the work-hardened layer and the subadjacent layer. The ratio of shear wave velocity in the upper layer to that in the subadjacent layer is near to 0.95. Experimental data obtained at several frequencies (0.5–2.0 MHz) showed good agreement with expected velocities for a layer thickness ranging from 3 to 5 mm.
On the use of comfortable listening levels in speech experiments
Authors: Simon Claude
Published: October 2005

In order to investigate the effect of level of presentation on subjects’ labeling of speechlike sound patterns, synthetic stimuli were constructed, varying systematically F0 contours, VOT, and F2 transitions. These stimuli were presented in random sequences at levels between 15 and 105 dB SPL to subjects with normal hearing. No significant response variation was observed in the range 40–100 dB SPL. Subjects’ labeling behavior suddenly breaks down below levels of around 35 dB SPL. The secondary findings of the study are also discussed in terms of different specific processing strategies for different specific speech features.
Processing spatially aliased arrays
Authors: Hinich Melvin J.
Published: October 2005

A linear array can detect a plane wave signai at a wrong bearing if the signal wavelengths are shorter than twice the distance between the closest adjacent sensors. This penomenon, called spatial aliasing, is most pronounced when the bearing is near endfire. This paper presents a method for correcting spatial aliasing of broadband signals using the frequency-wavenumber approach to array processing. Also presented is a method for averaging the ω–κ Fourier coefficients that will give a more accurate bearing estimator than the method presented by Clay, Hinich, and Shaman [J. Acoust. Soc. Am. 53, 1161–1166 (1973)]. The methods discussed in this paper can be used for a sparse unequally spaced array which is detecting a dispersive signal.
Reflection from a variable-index half space: Uniform and nonuniform representations
Authors: Stickler D. C.
Published: October 2005

Consider the problem of a point harmonic source in a homogeneous half space over a second half space in which the sound speed is larger than that in the source half space and for which the speed in the second half space decreases as a function of distance along the interface. The usual geometrical acoustics ansatz is used to obtain the reflected and transmitted field as well as the lateral wave field. The lateral wave field displays some new properties not present in the case when the higher-speed medium is homogeneous. It shows modifications to both the phase function and the 3/2 range decay law for the portion of the lateral wave path along the interface. In addition, it shows that the square-root decay with range is modified by an additional decay which is proportional to the range multiplied by the derivative of the index. This is a consequence of the divergence of the lateral wave rays as they leave the interface. As in the case of the homogeneous higher-speed medium, the lateral wave expansion derived by the usual geometrical acoustic ansatz becomes singular on the critical ray. It is shown how the reflected and lateral waves can be used to obtain a uniform expansion for the scattered field which is valid for all observation points beyond the so-called critical ray. The ansatz for the uniform expansion is provided by the uniform expression for the scattered field for the case when the higher speed medium is isospeed and it involves the parabolic cylinder functions. The ansatz does not require that the source medium be homogeneous, nor does it require that the interface be planar. Away from the critical ray this expansion reduces to the usual results of geometrical acoustics.
Self-excited depth-mode resonance for a wall-mounted cavity in turbulent flow
Authors: Elder S. A.
Published: October 2005

Experimental and theoretical results are presented for a wall-mounted cavity in turbulent flow, oscillating at Helmholtz or depth-mode resonance, where the mouth dimensions are small compared with acoustic wavelength. A new, computerized, hot-wire method was employed to investigate the oscillating flow field in the cavity mouth. Measured wavelength of the interface wave agrees well with predictions of Michalke, using an equivalent laminar flow model based on the oscillating mean velocity profile. By means of a forward transfer function derived from the theoretical interface wave model and a backward transfer function derived from organ-pipe theory, a root locus solution of the frequency lock-in problem has been obtained. Predicted frequencies and sound pressure amplitudes are in good agreement with experimental values at the lower modes. Both resonant and off-resonant oscillation was investigated. For resonant oscillation, the streamwise slot width is required to be M−1/4 times the disturbance wavelength, where M is an integer. For situations in which the equations are applicable, the method can be used to predict design parameters for nonoscillating wall cavities in moving vessels.
Scattering from buried inhomogeneities—a general three-dimensional formalism
Authors: Kristensson Gerhard , Ström Staffan
Published: October 2005

In the present article we give a general three-dimensional formalism for scattering in two half spaces, one of which contains a bounded inhomogeneity. Our formalism consists of an extension of the transition matrix method which has been given by Waterman, a method which applies equally well to acoustic, electromagnetic, and elastic scattering. The formalism is here developed in detail for the case when the source and inhomogeneity are situated in different half-spaces. However, the same method works for other source positions as well, and the basic equations are given also for the case when the source and the inhomogeneity lie in the same half space. In the final expression for the total scattered field, that part (the so-called anomalous scattered field) which depends on the presence of the inhomogeneity, can be separated, and the physical meaning of the various quantities which determine this anomalous scattered field can be identified. The inhomogeneity enters through its T matrix, and previous results on various bounded configurations of scatterers can therefore be inserted and used in the present formalism. Numerical results are given for inhomogeneities consisting of one or two spheres.
Modification of bubble oscillations by nearby objects
Authors: Keller Joseph B.
Published: October 2005

The effect of a wave scattered back to an oscillating bubble from a nearby object is studied. It is shown that this wave alters the decay rate of the bubble oscillation, but hardly changes its frequency. These results agree with the observations of S. Ayyash.
A comment on unrealistic resonance curves
Authors: Backus John
Published: October 2005

Some published examples of resonance curves of vibrating systems exhibit errors that should be corrected before they become firmly established in the literature.
Voice/mouth synthesis and tactual/visual perception of /pa, ba, ma/
Authors: Erber Norman P. , De Filippo Carol Lee
Published: October 2005

The onset of voicing relative to onset of visible articulation is a potential cue for lipreaders to recognize nasal/stop consonants. The bilabial consonants /p, b, m/ were selected for study because of their high visibility and ease of optical synthesis. A phototransistor behind the teeth and an external microphone indicated mouth opening and voice onset, respectively, to measure relative timing of the two cues in natural speech. Average voicing leads for ten adults were the following: /ma/, +66 ms; /ba/, −1 ms; /pa/, −58 ms (/ma–ba/ articulatory boundary, +28 ms; /ba–pa/ articulatory boundary, −18 ms). To test relative timing of voice onset and mouth opening as a potential perceptual cue, we produced synthetic ’’syllables’’: The face substitute was an oscilloscope pattern, forming a mouth shape for 250, 400, or 550 ms; the voice substitute was a vowel-like buzz delivered through a hand-held vibrator. Buzz accompanied mouth opening with lead times of from +200 to −200 ms (40-ms steps), and ended simultaneously with mouth closure. Normal-hearing observers labeled each combination ’’ma,’’ ’’ba,’’ or ’’pa.’’ Practiced lipreaders with knowledge of the onset cue subdivided the continuum with mean boundaries at +82 ms (/ma–ba/) and −87 ms (/ba–pa/). Individual differences occurred in sharpness and location of labeling boundaries. Because articulatory and perceptual boundaries are not coincident, this combined-mode cue appears insufficient for consonant recognition unless performance can be improved through extensive training.
Regression interpretation of differences in time-intensity trading ratios obtained in studies of laterality using the method of adjustment
Authors: Trahiotis Constantine , Kappauf William E.
Published: October 2005

This paper proposes a regression interpretation of the laterality matching data recently reported by Young and Levine [J. Acoust. Soc. Am. 61, 607–609 (1977)]. Under this interpretation, the difference between the trading function obtained when Δt is adjusted and that when ΔI is adjusted is ascribed to a judgmental bias associated with the method of adjustment. Arguments against associating the results of Young and Levine with the issue of dual images are presented.
Temporal factors and suppression effects in backward and forward masking
Authors: Weber Daniel L. , Green David M.
Published: October 2005

We discuss several experiments examining the influence of temporal parameters on suppression effects in backward and forward masking. The signal is always a brief 10-ms 2-kHz sinusoid; the masker a narrow band of noise of 40-dB spectrum level, 200-Hz wide, centered at the signal frequency. In some conditions, the presence of a second band of noise of the same spectral level in the region of 2300−3700 Hz appears to suppress the effects of the masker. Changes in the amount of suppression are examined as functions of the delay and duration of the suppressor (experiments 1 and 2). Adding the suppressor during the 50-ms interval nearest the signal produces changes in the signal threshold that are similar to those produced by reducing the level of the masker during this interval for both backward and forward masking (experiment 4). The similarity of these results suggests the operation of peripheral processes common to both backward and forward masking. However, if one increases the duration of the suppressor beyond this 50-ms interval there is no effect on forward masking, but large additional reductions in backward masking. This difference, in conjunction with other recent experiments, suggests the operation of additional central processes in backward masking. For some observers, these additional processes appear to operate over fairly long periods of time (250–500 ms). Such long durations are inconsistent with the estimates of integration time (?200 ms) obtained for these same observers (experiment 3).
Nearfield performance of passive correlation processing sonars
Authors: Patzewitsch J. T. , Srinath M. D. , Black C. I.
Published: October 2005

Passive correlation processing sonars in which the distance of a moving source from the receivers is not appreciably greater than the inter-receiver spacing are considered. In the simplified case, where two receivers are employed, the processor chooses one of the received signals as a reference and adds a corrective time delay and Doppler shift to the other signal before the correlation operation is performed. When the processor selects a time delay and Doppler shift corresponding to that present in the signals, the correlation function has a peak. The degree of correlation between the two signals is measured with the use of a passive uncertainty function. An approximation is made for narrow-band signals which is computationally advantageous. The effects of time delay and constant Doppler shift are discussed, and the degradation resulting from time varying Doppler shift is derived and plotted. Results are presented for both sinusoidal and narrow-band type signals. A technique of plotting contours of maximum data integration time is developed and shown to significantly reduce the complex problem of studying scenario geometries.
Simplified method for determining piezoelectric constants for thickness mode transducers
Authors: Fox Martin D. , Donnelly Judith F.
Published: October 2005

A procedure is described for obtaining the stress constant e33 for an arbitrary piezoelectric transducer operating in the thickness mode. A closed-form solution is is developed which uses measurements of the electrical impedance of the transducer as input. Verification of the calculated parameters is accomplished by incorporating them into a computer model of the transducer. A discussion of various methods of obtaining the clamped capacitance C0 is included as well as a calculation of an equivalent resistance to represent losses in the ceramic. Numerical examples are presented.
Improved design of spherical multimode hydrophone
Authors: Ko Sung-Hwan , Pond Hartley L.
Published: October 2005

An improved design is made for a spherical multimode hydrophone by dividing each hemisphere into two zones and selecting the position of the line of division between them, so that the resonances associated with higher modes of the spherical shell vibrations, specifically n=3 and n=5 modes in the present case, are eliminated. The elimination of these resonances has led to the provision of a frequency-independent dipole pattern over a wide range of frequencies. The present theory includes the effect of spherical shell bending, since it is important at higher modes. Accordingly, the resonant frequencies are clearly identified by the associated mode numbers. In both theory and experiment, these resonant effects were eliminated by employing the newly designed hydrophone.
On fiber-optic hydrophone sensitivity
Authors: Shajenko Peter , Flatley James P. , Moffett Mark B.
Published: October 2005

Previous treatments of fiber-optic hydrophone sensitivity have neglected the effect of dimensional changes of the fiber in response to acoustic pressure. It is shown here that the changes in length actually contribute more to hydrophone sensitivity than do the refractive index changes; the two contributions are of opposite sign. An experiment verifying the sensitivity calculation was performed using 60-kHz pulses from a spherical source.
Factors contributing to the multiple rate of piano tone decay
Authors: Hundley T. Chase , Benioff Hugo , Martin Daniel W.
Published: October 2005

Causes for the decrease in rate of piano tone decay with time of tone duration were investigated, including the following: different rates for different vibration modes or groups of modes, nonlinear transformation of mechanical energy to acoustical energy, storage of mechanical energy for subsequent acoustical radiation, transfer of energy between string modes perpendicular and parallel to the bridge, interference among strings that are almost exactly in tune, and change in rate of energy transfer from the multiple-string source to the bridge during the transition from an initial in-phase condition to a later out-of-phase condition. The last two closely related factors were found to control the rate change in most cases.
Acoustical conditions preferred for ensemble
Authors: Marshall A. H. , Gottlob D. , Alrutz H.
Published: October 2005

Observations on the acoustical conditions preferred by musicians when performing lead to the following hypotheses: (a) Ease of ensemble depends upon the audibility of musical transient in the early reflection sequence, and (b) reverberation plays only a minor part in ensemble, though it is the most preferred acoustical condition for soloists. These proposals were tested experimentally. Reflection-free recordings of the individual instruments in a string trio were made simultaneously. Each musician then played his/her part again in ensemble with recordings of the other two instruments, while sound fields were synthesized from the recordings to simulate stage conditions. High- and low-pass filtering of the reflections with cutoff frequencies between 0.25 and 2 kHz were used in successive trials. The musicians were asked to judge the ease of ensemble relative to the preceding trial. High-pass reflections were generally preferred to low-pass filtered reflections. In subsequent trials the effects of increasing the simulated stage size and of imbalance between reflections of different instruments were included. Some design guides for stages for orchestral music are proposed.
New optical probe for local elastic study in transparent media
Authors: Michard F. , Perrin B.
Published: October 2005

A new optical probe to measure the local elastic properties in transparent media has been investigated. The device we describe here performs an acousto-optic interaction (Bragg diffraction) in the frequency range 200 MHz–1 GHz. The phase of the ultrasonic wave is then extracted by optical heterodyning. The spatial resolution which is reached (10 μm), points out the fact that accurate measurement of the absolute ultrasonic velocity requires a careful correlation to the sample homogeneity, so a statistical treatment of the results is given. By means of this device, local ultrasonic velocity fluctuations of the order of 10−4 can be detected. Thus, we can anticipate applications such as control of material doping (homogeneity, impurity gradient, etc.) and fundamental studies of phonon propagation in thermal or strain gradients.
Performance of a Bragg-diffraction imaging system with partially coherent light illumination
Authors: Saiga N. , Suzuki T.
Published: October 2005

A technique of reducing the zero-order coherently generated noise in an ordinary Bragg-diffraction imaging system by means of partially coherent light illumination (both temporal and spatial coherence) is described. The reduction is due to the decrease of both types of coherence in the illumination, because the noise generation depends on coherent light illumination in the ordinary imaging system. The experimental results demonstrate that the noise has been decreased dramatically without great sacrifice of the image quality. Moreover, by investigating the imaging characteristics with various types of illumination, the illumination with lower temporal and higher spatial coherence was found to be most effective in noise reduction and image formation.
Subjective loudness of ’minimized’ sonic boom waveforms
Authors: Niedzwiecki A. , Ribner H. S.
Published: October 2005

For very long supersonic aircraft the ’’midfield’’ sonic boom signature may not have evolved fully into an N wave at ground level. Thus in current boom minimization techniques the shape of the aircraft may be tailored to optimize this midfield wave form for reduced subjective loudness. The present investigation tests a family of ’’flat-top’’ waveforms cited by Darden: all but one have a front shock height (-pSH) less than the peak amplitude (-pMAX). For equal subjective loudness, ’’flat top’’ vs N wave (peak overpressure -pN), the peak amplitude of the ’’flat top’’ signature was found to be substantially higher than that of the N wave; thus for equal peak amplitude the ’’flat-top’’ signature was quieter. The results for equal loudness were well fitted by an empirical law -pSH+0.11-pMAX =-pN; the equivalence shows how the front shock amplitude (-pSH) dominates the loudness. All this was found compatible with predictions by the method of Johnson and Robinson.