bluuebunny/crossref_metadata_2025 huggingface dataset:
Practical implementations of speech waveform coders for the present day and for the mid 1980s
Authors: Goldberg Aaron J.
Published: October 2005

This paper discusses practical implementations of low bit-rate speech waveform digitizers for the pre-1980 and post-1985 time periods. Based on requirements of expected mathematical complexity, accuracy, and redundance of these coders, the basic hardware speeds and amount of logic to implement them are given for today’s implementations. Issues important to the commercial and military users are examined to ascertain how they can radically alter the architectures and hardware chosen for implementation. Then assuming that the speech digitization algorithms remain at least as complex as today’s techniques, well-known procedures for forecasting LSI improvements and cost reductions are used in estimating the hardware needed to implement these systems in the mid 1980s.
On the application of modern control theory to improving the fidelity of an underwater projector
Authors: Mazzola Claude J. , Birdwell John D. , Athans Michael
Published: October 2005

The paper presents a technique for controlling the radiated sound pressure from an electroceramic projector in water. This technique involves the implementation of a state variable feedback tracking algorithm. The state variables of the system are estimated with a Kalman–Bucy filter from the measured radiated pressure. The state variables are then fed back to effect an appropriate compensation of the system, which results in a least-square minimization of the difference between the measured and desired pressure signatures. The algorithm has been tested with an actual projector. The results show that the measured pressure tracks the desired pressure reasonably well.
Total reflection of S
H waves in the presence of slip and friction
Authors: Comninou Maria , Dundurs J. , Chez Eugene L.
Published: October 2005

The paper examines the total reflection of SH waves by a contact interface that can locally slip when the incident wave is strong enough to break friction between the two solids. The solution is constructed by correcting the fields for the welded interface and takes advantage of known results for moving dislocations. The formulation leads to singular integral equations of the Cauchy type which must be treated numerically. Because of the number of independent variables, the problem cannot be exhausted through a parametric study, and only a specific combination of materials is worked out in detail. The results allow one to form some judgment, however, about the location of slip zones, their extent, the form of the slip velocity, and the interface shearing tractions.
Approximate dynamic analysis of Timoshenko beams and its application to tapered beams
Authors: Nagaya Kosuke
Published: October 2005

An approximate method of analysis for dynamic response problems of a Timoshenko beam is presented. The results for the beam are obtained by the addition of the solution for bending and rotatory motions and that for the shear motion by neglecting the inertia force of the shear motion. The result by this analysis compared with both exact results for Timoshenko and Euler–Bernoulli beams. As applications of this study, dynamic response problems of taper beams with moving load are solved by this method.
Scattering of sound in suspensions of spheroidally shaped particles
Authors: Ahuja Avtar S.
Published: October 2005

Particles are assumed to have oblate and prolate spheroidal, spherical, disklike, and needlelike shapes, with symmetry axes for oblate and prolate spheroids assumed to be either parallel or perpendicular to the acoustic field. The disk-shaped and needle-shaped particles are assumed to be either broadside or edgewise (or end on) to the acoustic field. Scattering cross section for sound propagation in particle suspensions prepared in viscous fluid media has been calculated. For large density differences (of about 150%) between suspension components, computations indicate substantial effects of particle shape and orientation on the scattering of sound in dilute suspensions. For an oblate spheroid oscillating broadside, the backscattered signal is significantly (up to 30%) greater than that for a sphere, or for an oblate spheroid oscillting edgewise. Departures from Rayleigh’s law of scattering (by about 10% over one frequency decade) occur for very dense particles suspended in a viscous fluid medium.
Attenuation and velocity of surface waves on a piezoelectric substrate coated with admittance films
Authors: Shimizu Y. , Terazaki A.
Published: October 2005

The effects of an admittance sheet upon the propagation of surface acoustic waves on a piezoelectric substrate are investigated. The quasistatic approximation and a very simple approximate formula are shown theoretically, and these are compared numerically with each other. It is found that the simple formula is in good agreement with the quasistatic approximation and with measured values. It is also shown that the attenuation constants become smaller when the capacitive susceptance of the sheet increases.
An algorithm for the design of transformerless broadband equalizers of ultrasonic transducers
Authors: Augustine L. J. , Andersen J.
Published: October 2005

A new design strategy for broadbanding ultrasonic transducers was recently presented, which generates a lossless equalizer, matching a resistive source to a piezoelectric transducer with power gain displaying a maximally flat (Butterworth) characteristic. However, three undesirable restrictions are part of the existing algorithm; (i) the center frequency of the design is fixed, limiting its usage to certain passbands, (ii) the design requires the use of an ideal transformer for all source resistance and tranducer combinations but one, and (iii) the resulting element values are often impractical. The purpose of this paper is to present a generalization of the algorithm which broadens its applicability. The main result is an algorithm for the design of a lossless transformerless broadband equalizer with maximally flat power gain, and a delineation of the exact latitude on passbands and source resistances.
A surface acoustic wave sonobuoy
Authors: Das P. , Lanzl C.
Published: October 2005

A transmitting hydrophone which remotely senses both absolute pressure and changes in pressure has been developed using a surface acoustic wave (SAW) oscillator. This oscillator is formed by placing a SAW delay line or resonator in the feedback loop of an amplifier. The pressure applied to the hydrophone is converted to a flexural loading of the piezoelectric plate which alters the surface wave velocity on the plate, consequently shifting the oscillator frequency. This frequency modulated signal is easily transmitted to a remote location for signal recovery. The piezoelectric plate thickness and length can be chosen to optimize the sensitivity of the SAW hydrophone. The surface wave element of the oscillator is a planar structure, therefore, it is simple and inexpensive to manufacture. Furthermore, the size and power requirements of the SAW hydrophone are small, typically less than 50 cm3 and 300 mW. This paper presents performance data of two SAW hydrophones using SAW oscillators at 44 and 77 MHz in conjunction with a versatile signal demodulation system. Measurements of sensitivity and frequency response were made for both delay line and resonator hydrophones manufactured on lithium niobate and S-T quartz substrates, respectively, and compared with measurements obtained from conventional hydrophones in the identical set-up.
Distribution of sonic plesio-velocity in a compact bone sample
Authors: Lees Sidney , Cleary Paul F. , Heeley John D. , Gariepy Ernest L.
Published: October 2005

Since compact bone is demonstrably anisotropic and inhomogeneous, the measured quantities yield a plesio-velocity rather than a true sonic velocity, which makes it difficult to compare velocity measurements among several bone samples. Distribution of the plesio-velocity for 11 pairs of 2 mm thick specimens from a single mature bovine compact bone sample using 100-ns well-damped sonic pulses emitted by a 10-mHz transducer show that anisotropy exists in both axial and transverse directions and must be associated with the local structure and composition. Changes in the same specimens when wet, dry, and rehydrated show an increase in velocity and anisotropy of the dry over the wet state. The plesio-velocity is greater in the axial direction, along the bone axis, than in the transverse plane. The change in plesio-velocity from wet to dry bone is greatest along the bone axis and least in the transverse plane. Changes in dimension, when the bone specimens were dried, show the bone sample to be anisotropic in this parameter also, but in the reverse order from that for the plesio-velocity. Shrinkage is least along the osteons and a maximum in the transverse plane.
Cavitation-induced capillary waves in ultrasonic atomization
Authors: Mir Jose M.
Published: October 2005

A mathematical analysis of surface capillary waves on an incompressible liquid is presented. Periodic excitations in the form of hydraulic shocks due to cavitation are assumed in order to derive threshold conditions for ultrasonic atomization. Atomization threshold is found to be approximately linear with fluid viscosity for capillary waves oscillating at one-half the driving frequency. Another result of the analysis is a nondiscrete dispersion relation which allows a continuum of solutions within certain specified ranges of capillary wavelengths. Such a dispersion relation could partly account for the decrease in monodispersity of atomized droplets observed at high cavitation fields.
Ear dominance and sequential interactions
Authors: Deutsch Diana
Published: October 2005

When two tones of different frequency are simultaneously presented, one to each ear, a single pitch may be heard that corresponds to the frequency delivered to one ear rather than to the other. That is, the frequency information delivered to one ear may be followed and to the other ear suppressed. The present study explored the sequential conditions under which this effect occurs. Clear ear dominance was obtained in sequences where the two ears received the same frequency in succession. However, ear dominance was absent in sequences where successive dichotic chords were composed of different frequencies. From these and other findings a basis for ear dominance is proposed.
Discrimination of relative onset time of two-component tones by infants
Authors: Jusczyk Peter W. , Pisoni David B. , Walley Amanda , Murray Janice
Published: October 2005

A great deal of research has focused on the perception of voice onset time (VOT) differences in stop consonants. Yet, the nature of the mechanisms responsible for the perception of these differences is still the subject of much debate. Recently Pisoni [J. Acoust. Soc. Am. 61, 1352–1361 (1977)] has presented evidence which suggested that the perception of VOT differences by adult listeners may reflect a basic limitation on processing temporal order information by the auditory system. For adults, stimuli with onset differences approximately greater than 20 ms are perceived as successive events (either leading or lagging), while stimuli with onset differences less than about 20 ms are perceived as simultaneous events. Thus, differences in voicing may have an underlying perceptual basis in terms of three well-defined temporal attributes corresponding to leading, lagging, or simultaneous events at onset. The present experiment was carried out to determine whether young infants can discriminate differences in temporal order information in nonspeech signals and whether their discrimination performance parallels the earlier data obtained with adults. Discrimination was measured with the high-amplitude sucking (HAS) procedure. The results indicated that infants can discriminate differences in the relative onset of two events; the pattern of discrimination also suggested the presence of three perceptual categories along this temporal continuum although the precise alignment of these categories differed somewhat from the values found in the earlier study with adults.
Stimulus dominance in fused dichotic syllables: Trouble for the category goodness hypothesis
Authors: Repp Bruno H.
Published: October 2005

Repp [J. Acoust. Soc. Am. 60, 456–469 (1976)] hypothesized that dichotic stimulus dominance relationships between fused speech sounds reflect the relative category goodness of the competing stimuli, i.e., their relative perceptual distances from the listener’s linguistic category prototypes. In experiment I, 15 synthetic syllables from a /b/–/d/–/g/ continuum were dichotically fused with three selected stimuli from the same continuum and presented to listeners for identification. Stimuli in the vicinity of phonetic category boundaries were found to make weaker dichotic competitors than stimuli from well within a phonetic category, as predicted. However, some systematic deviations from the predictions and large individual differences were noted. In experiment II, synthetic syllables from a /ba/–/da/–/ga/ continuum were paired with either of the two endpoint stimuli (/ba/,/ga/) in dichotic or mixed presentation. The resulting fused hybrid stimuli were presented in identification and AXB discrimination tests. The hybrids were perceived quite categorically, and there was little difference between dichotic and mixed modes of presentation. These results did not replicate earlier data [Repp, Haskins SR-45/46, 123–139 (1976)] that had suggested that discrimination of dichotic hybrid stimuli might be based on a level of representation preceding phonetic categorization. The category goodness hypothesis, which implies such a level, was neither supported nor contradicted. In experiment III, the prediction was tested that increasing the aspiration amplitude of a /ta/ syllable, and thus its category goodness, would increase the perceptual dominance of this stimulus over a /da/ simultaneously presented to the other ear. This hypothesis was not supported by the data. Rather, the response pattern suggested that a listener’s success in perceptually integrating the aspiration noise (of /ta/) with the fused vocalic portion (of /da/ and /ta/) into a single phonetic percept depended on the perceived spatial locations of these stimulus portions. Taken together, the results of the three experiments cast doubt on the category goodness hypothesis and suggest that dichotic stimulus dominance in fused speech sounds is determined by psychoacoustic factors, some as yet undefined.
On the use of a three-words-per-item format in tests for the hearing of speech
Authors: Harris J. Donald
Published: October 2005

Single-word lists and sentence lists each have their own advantages and disadvantages for testing hearing for speech. A short history is offered of the attempts since 1941 to achieve the advantages of sentential material by presenting strings of grammatically unrelated words. Such material retains the several advantages of single-word tests. At least two recent tests using a three-monosyllables-per-item format with closed-response sets are seen to make significant advances over earlier tests in maximizing advantages and minimizing disadvantages of material presented.
Nonlinearities in the coding of intensity within the context of a temporal summation model
Authors: Penner M. J. , Shiffrin R. M.
Published: October 2005

A model of temporal summation and intensity coding relates the subject’s internal percept y (t) to the stimulus input x (t) by the equation y (t) =g{ℱt−∞ f[x (τ)]h[t,τ,x (τ)] dτ}. In words, some transformation f[x (t)] of the stimulus intensity is weighted by a function h and integrated; the result is transformed into the internal percept by a function g. This system postulates a linear integral operator preceded and followed by transformations which may be nonlinear. Based on forward masking of clicks by white noise, we (1) show that the above characterization of the model is appropriate (which involves showing that there is a linear temporal summation stage), and (2) derive certain characteristics of the system’s nonlinearities. In particular, the integral of h times f is shown to be a nonlinear function of the input intensity exhibiting more compression than a power function. It is also shown that h must depend upon the intensity of the stimulus.
Danger of auditory impairment from impulse noise: A comparative study of the CHABA damage-risk criteria and those of the Federal Republic of Germany
Authors: Pfander F. , Bongartz H. , Brinkmann H. , Kietz H.
Published: October 2005

On the basis of the impulse diagrams of various weapons and many audiometric tests, the CHABA impulse-noise damage-risk criteria (DRC) are compared with those of the Federal Republic of Germany. Both DRC indicate maximum permissible exposures in terms of peak-pressure level and of effective duration. Both DRC aim to protect 95% of the exposed population from permanent auditory damage. The computation of the effective duration differs between the CHABA DRC and the German DRC, and it generally results in a longer effective duration for CHABA. The current study is based on the results for more than 10 000 soldiers, who were audiometrically tested in a mobile monitoring station before firing practice and beginning 2 min after exposure until complete recovery. In a special study, it was possible to compare the results for 478 German soldiers and to evaluate the relative value of the CHABA DRC and the German DRC. This comparison showed that the CHABA DRC are too restrictive, permitting unnecessary ’’less maximum permissible load’’ than the German DRC. Moreover, owing to the large variability in TTS2, measurement of the whole recovery time beginning 2 min after exposure has a greater predictive value. Therefore, recovery time should be used in the evaluation of the DRC.
Intensity perception. X. Effect of preceding stimulus on identification performance
Authors: Purks S. R. , Callahan D. J. , Braida L. D. , Durlach N. I.
Published: October 2005

This article describes some results on the effect of the preceding stimulus on performance in an intensity-identification experiment with feedback. Based on previous research and our own subjective experiences as listeners, we had expected that sensitivity would increase when the intensities of the preceding and current stimuli were close together. The results of our experiments show, however, that this is not the case: sensitivity is independent of the preceding stimulus. The fact that the response variance tends to decrease when the intensities of the preceding and current stimuli are close together is found to be caused solely by sequential effects in response bias. These findings create an interesting puzzle concerning the mechanism by which feedback improves sensitivity in identification. Apparently, the most obvious hypothesis—namely, that the feedback enables the previous stimulus to be used as a standard for judging the current stimulus—is false.
Auditory cortex and the pitch of complex tones
Authors: Whitfield I. C.
Published: October 2005

Two cats were trained to discriminate between rising and falling pitch sequences generated by complex tones. The finding of Heffner and Whitfield [J. Acoust. Soc. Am. 59, 915–919 (1976)], that the intact animals respond to the fundamental pitch rather than to the harmonic content, was confirmed. After bilateral ablation of auditory cortex this was no longer the case. The animals lost their initial training, but could be retrained to respond to the complex tone sequences; however, they now required to be separately trained to each complex tone and did not exhibit transfer between tone pairs that had similar pitch shift but different harmonic composition. The results suggest that cats without auditory cortex respond only to the individual frequencies of the complex and are unable to detect the overall pitch to which those complexes normally give rise.
A reciprocity technique for estimating the diffuse-field sensitivity of piezoelectric transducers
Authors: Hill Eric v. K. , Egle Davis M.
Published: October 2005

A technique for estimating the diffuse-field response of piezoelectric transducers on a solid is developed. The procedure is based on a reciprocity principle and is analogous to the technique used for calibrating transducers in a fluid medium. Both ultrasonic and acoustic emission transducers have been calibrated and the results compared to the diffuse-field response calculated from transducer face-to-face response characteristics.
A theory for optimization in the use of acoustic emission transducers
Authors: Hill Roger , El-Dardiry Samir M. A.
Published: October 2005

We postulate that measurement precision and the magnitude of acoustic emission signals will be affected by the type and thickness of the couplant used to couple the transducer to a structure. A theoretical solution is provided to determine the transmission coefficient of a multilayer system of n layers. A longitudinal wave is assumed to be normally incident on the system. Theoretical transmission coefficients are obtained for waves transmitted through three, four, and five layers. Specific calculations are carried out for a particular five-layer system which is applicable to an acoustic emission transducer. Conclusions are drawn concerning the measurement precision likely to be obtained from this type of transducer used in this configuration.
The design and test results for an acoustic lens with elliptic surfaces
Authors: Schlussler Larry
Published: October 2005

A design of a nonspherical acoustic lens and its test results are presented. The lens has elliptic surfaces to eliminate on-axis spherical aberration. The lens was designed with the aid of third-order aberration theory. Acoustic lenses with nonspherical surfaces are easily manufactured and should prove to be a valuable addition to single or multiple element lens systems.
Systematic errors in indirect estimates of basilar membrane travel times
Authors: Ruggero Mario A.
Published: October 2005

There exist in the literature three attempts to derive basilar membrane travel times from the phase versus frequency characteristics of responses to tones in the auditory nerve [Anderson et al., J. Acoust. Soc. Am. 49, 1131–1139 (1971)], cochlear nucleus [Gibson et al., in Psychophysics and Physiology of Hearing, edited by Evans and Wilson (Academic, New York, 1977), pp. 57–68], and basilar membrane [Robles et al., J. Acoust. Soc. Am. 59, 926–939 (1976)]. It is argued in this paper that these derivations probably have overestimated the actual mechanical travel times. Travel time was originally defined by von Békésy as the latency between the onset of a click stimulus and the onset of basilar membrane vibration. For a linear bandpass system, the frequency-domain equivalent of this latency is the high-frequency asymptotic slope of the phase lag versus frequency characteristic, which is not generally a linear function. In the neural studies (auditory nerve and cochlear nucleus) it was assumed that the phase versus frequency characteristic was a straight line. Slopes derived under a linear assumption are probably closer to the weighted average group delay (i.e., the center of gravity of the click response) than they are to travel time. In the Mössbauer study of basilar membrane mechanics the latency of the response to clicks was compared with the low-frequency slope of the phase characteristic. The comparison should have been made with the high-frequency slope.
A numerical simulation of the effects of oceanic finestructure on acoustic transmission
Authors: Ewart Terry E.
Published: October 2005

A simple numerical simulation model is presented which includes the effects of oceanic finestructure together with previously developed theoretical treatments of the effects of internal waves on acoustic transmission. The wave equation solution to particular layer geometries developed by Brekhovskikh [Waves in Layered Media (Academic, New York, 1960)] is combined with the theoretical model of acoustic scattering based on internal waves developed by Desaubies [J. Acoust. Soc. Am. 64, 1460–1469 (1978)]. In this treatment it is assumed that a single finestructure layer is passively advected by internal waves. The layer modulates the effects of internal waves. Experiments carried out at Cobb Seamount over a fixed, horizontal, wholly refracted path indicate that the power spectrum of the phase fluctuations is fit almost exactly by models based on internal waves only, while the power spectrum of the log amplitude fluctuations is not. In the present treatment the predictions of the phase fluctuations remain unaffected by the presence of finestructure, and the predicted power spectrum of the log amplitude is in considerably better agreement with observation.
Averaging of fish target strength functions
Authors: Foote Kenneth G.
Published: October 2005

A general model for averaging the acoustic target strength functions of fish is stated in calculable form. It accounts for the influences of the distribution of generally coupled spatial and orientation states of fish, geometric perspective, and beam patterns on observations of target strength. The model is developed and applied to observation of fish by directional, downward-looking sonars. A particular example is considered in which the sonar is represented by an ideal circular piston, the spatial distribution of fish is homogeneous, and the orientation distribution is spatially homogeneous and characterized by a uniformily distributed azimuthal variable and an independent, essentially normally distributed tilt angle variable. Averaged and averaged-squared backscattering cross sections are computed from high quality gadoid target strength functions measured at two ultrasonic frequencies. Results for a sonar half-beamwidth of 2.5 deg for three different realizations of the tilt angle distribution are expressed in the logarithmic domain and regressed linearly on fish length. The significance of species, frequency, and orientation distribution differences among the regressions is noted. Estimates of the mean ratio of averaged-squared backscattering cross section and squared-averaged backscattering cross section are presented.
Source level model for propeller blade rate radiation for the world’s merchant fleet
Authors: Gray Leslie M. , Greeley David S.
Published: October 2005

A model is developed for the acoustic source strength of blade rate line energy produced by single-screw merchant vessels. These source strengths are based on observed cavitation time histories on merchant vessels and on limitations imposed by considerations of propeller design procedures and ship vibration criteria. Relationships are presented for the expected value of the blade rate source strength for ships of different lengths, expressed both as a monopole source strength located at a known depth below a free surface and as a dipole source strength that describes the pressure radiated to the farfield. These relationships are based on a small sample of merchant ship characteristics and are exercised for the estimated population of ships at sea. This calculation yields a statistical description of the distribution of source level and frequency of propeller blade rate acoustic energy for the fleet of single-screw merchant vessels.
An experimental investigation of the parabolic reflector as a nearfield calibration device for underwater sound transducers
Authors: McKemie M. Jean , McKinney Chester M.
Published: October 2005

Results are presented of an experimental investigation of the use of thin metal parabolic reflectors to form underwater quasiplane wave regions in the nearfield of the reflector. This quasiplane wave volume is then used to calibrate underwater sound transducers in terms of directivity and sensitivity. Such reflectors, mass produced for use with electromagnetic wave devices, are readily available, inexpensive, and rugged. Experiments were conducted with reflectors ranging from 45 to 122 cm in diameter at frequencies from 30 to 300 kHz. It might be noted that at the higher frequencies the acoustic wavelength is approximately an order of magnitude shorter than that for which the reflectors were designed. Test transducers, typically half the size of the reflectors, were calibrated both in the nearfield of the reflector and in the farfield (using conventional techniques) and the results were compared. It was found that for the major lobe there was excellent agreement and that the levels of the minor lobes were in acceptable agreement but that the fine detail of the minor lobe structure differed for the two types of measurements. Sensitivity measurements differed by about ±1.0 dB. For low-frequency operation the metal reflector needs to be backed by air or other pressure release material in order to be an efficient reflector. It is concluded that the parabolic reflector technique has useful accuracy for many applications.
Ambient noise depth-dependence models and their relation to low-frequency attenuation
Authors: Weston David E.
Published: October 2005

Both a deterministic dipole model and the law of conjugate depths are applied to study the depth dependence of the low-frequency ambient noise in the main sound channel and, when used together, a reasonable agreement with experiment is obtained. Scattering or diffusion models for the region below critical depth agree well with experiment. Complete area and line source models for the ambient level are derived. Three approximate predictions of the low-frequency attenuation come from the deep ambient depth dependence, ambient differences with site position, and ambient differences with site and depth, respectively. All three are consistent with conventional measurements and with the scattering diffusion and bottom loss mechanism.
Resonance theory of elastic shear-wave scattering from spherical fluid obstacles in solids
Authors: Brill D. , Gaunaurd G. , Überall H.
Published: October 2005

The vector potential for an arbitrarily polarized shear wave in an elastic (lossless) medium incident on, and scattered by, a spherical fluid occlusion is expanded in vector spherical harmonics. The boundary conditions are dealt with for this incident vector potential in terms of two (scalar) Debye shear potentials ψ and χ giving rise to what we have termed ’’s and t waves,’’ respectively. The s wave scatters into both another s wave and also mode-converts into a compressional p wave. The t wave scatters only into another t wave with no mode conversion. Scattering amplitudes are cast in a series of resonance terms. The scattered p and s waves exhibit resonances; however, the t wave does not. We exhibit monostatic and bistatic plots of the first few partial-wave amplitudes (n=1,2,3,...) for the sp, ss, and tt scattering modes. When the background amplitude corresponding to scattering from an evacuated spherical cavity is removed from each partial-wave contribution, the remaining portion of the amplitudes is a clear series of liquid-sphere resonances. We display these resonances as functions of the acoustic size kda of the cavity, and of the order n of each mode. This work completes the determination of the scattering matrix elements for a fluid sphere in an elastic medium which was commenced by us earlier with the study of resonance effects in pp and ps scattering.
Evaluation and integration of acoustic features in speech perception
Authors: Massaro Dominic W. , Oden Gregg C.
Published: October 2005

Identification of synthetic stop consonants as either /bae/, /pae/, /dae/, or /tae/ was examined in two experiments in which the stimuli varied independently on voice onset time (VOT), the consonantal second and third formant (F2–F3) transitions and, in experiment 2, the intensity of the aspiration noise during the VOT period. In both experiments, the patterns of the resulting identification probabilities were complex, but systematic, functions of each of the independent variables. Of most interest was the fact that the likelihood of identifying a stimulus to be /bae/ or /pae/, rather than /dae/ or /tae/, was strongly influenced by the VOT as well as by the F2–F3 transitions. Analogously, the likelihood of identifying a stimulus to be /bae/ or /dae/, rather than /pae/ or /tae/, depended on the F2–F3 transitions as well as on VOT. Three explanations of these results were considered within a fuzzy logical model of speech perception: (1) that there is interaction in the evaluation of acoustic features, (2) that the listener requires more extreme values of acoustic features for some speech sounds than for that of other speech sounds, and (3) that the aspiration noise during the VOT period serves as an independent acoustic feature to distinguish /pae/ and /bae/ from /tae/ and /dae/.
Rigorous asymptotic theory of evanescent waves for guided propagation
Authors: Arnold J. M. , Felsen L. B.
Published: October 2005

Choudhary and Felsen proposed a high-frequency asymptotic theory of ducted propagation based on the tracking of local evanescent plane waves. In their construction of the asymptotic expansions for the modal fields and eigenvalues they observed that the true modal fields must be analytic on the waveguide axis, and they imposed that condition on the modal amplitude coefficients, although the axis is not included in the domain of uniformity of the asymptotic expansion. Yet, the procedure yielded asymptotic solutions that agree completely with rigorously derived results for special refractive index profiles. The problem is examined here within the framework of the theory of the ordinary differential equation that describes the modal field. It is shown that the asymptotic modal expansion coefficients must be single valued within a strip of the complex coordinate plane, and that this condition yields the same results as the procedure of Choudhary and Felsen. These authors also sought to remedy the nonuniformity of the expansion near the axis by extracting the known exact modal solution for a parabolic refractive index. By constructing a uniform asymptotic representation, this local parabolic approximation is shown here to be valid near the axis, but its domain does not extend far enough to permit overlap with the above-noted asymptotic expansion away from the axis.
Acoustic radiation pressure on a rigid sphere in a spherical wave field
Authors: Hasegawa Takahi , Ochi Masayuki , Matsuzawa Kiichiro
Published: October 2005

An analysis has been made of the acoustic radiation pressure acting on a rigid sphere in a spherical sound field for the purpose of completing the work of Embleton [J. Acoust. Soc. Am. 26, 40–45 (1954)] from the angle of practical application. His presentation has been simplified mathematically and improved into a more general form. Numerical calculations have been made with particular emphasis on the difference from the results for incident plane progressive waves as a function of the density of the sphere, the size parameter, and the distance of the sphere from the sound source.
Backscattering cross sections of live fish: PDF and aspect
Authors: Huang Kung , Clay Clarence S.
Published: October 2005

The probability density function (PDF) of the peaks of the envelopes of sonar echo from live fish were measured at beam aspect. The measurements were made at 220 kHz and in a waveguide. The fish was the common shiner (Notropis cornutus) and was about 120 mm (about 18 acoustic wavelengths) long. The PDF of the echoes was approximately Rayleigh when the fish was moving gently. The backscattering cross section equaled 4.2×10−5 m2. Transformation of the PDF’s to a target strength display in decibels displaced the maximum of the PDF to the target strength equaling 10 log10 (σbs/A0)+3 dB where σbs is the mean backscattering cross section and A0=1 m2. The target strengths of the common shiner (120 mm) and the mummechog (Fundulus heteroclitus, 100 mm) were measured as a function of aspect angle. Comparison of the experimental measurements and Love’s empirical target strengths for any aspect showed that the measured target strengths at broadside aspect were about the same and the target strengths at other aspect angles were several decibels less than Love’s values. Linear arrays of point scatterers were chosen to match the gross aspect dependence of the target strengths of the fish. The lengths of the arrays were 6.5 mm for the common shiner and 16.5 mm for the mummechog. These lengths were less than the lengths of the corresponding fish’s swim bladders.
Differential electrical excitation of the auditory nerve
Authors: Black R. C. , Clark G. M.
Published: October 2005

The multichannel cochlear prosthesis requires an electrode stimulus configuration which produces a stimulus field spatially localized to each electrode. In this paper, a three-dimensional discrete resistance model of the cochlea was developed which exhibits electrical response properties similar to those observed during electrical stimulation of the cochlea. The model results suggest that the spatial attenuation of current within the cochlea varies greatly in magnitude, depending on the stimulus configuration. In addition, the model suggests that the spatial attenuation of current in both the auditory nerve fiber endings in the organ of Corti and in the myelinated fibers within the cochlear ground paths is different from the voltage attenuation in the scalar fluids. Therefore the efficacy with which a particular stimulus configuration differentially excites local terminal auditory nerve fiber populations cannot be deduced from scalar voltage measurements which have previously been recorded in the literature. Consequently physiological experiments were performed in the cat to measure the current distributions in the terminal nerve fiber region for monopolar and bipolar stimulation of the scala tympani, and also for stimulation between the scala tympani and the scala vestibuli. The mean length constants measured in the basal turn for these stimuli were found to be 12, 3, and 7.5 mm, respectively.
Auditory-nerve fiber encoding of two-tone approximations to steady-state vowels
Authors: Reale Richard A. , Geisler C. Daniel
Published: October 2005

Responses to two harmonically related tones, approximating the lowest formants of nine American English vowels, were recorded from single auditory-nerve fibers. Data were compiled as period histograms for tones presented singly and in combination using the fundamental frequency of the two-tone complex as the time base. The amplitudes of the primary frequency components present in a histogram were estimated by least squares fitting a half-wave rectified sum of the stimulating sinusoids plus a constant. Nonlinear interactions resulted for most two-tone stimuli: one tone dominated the response. When one tone was equal to best frequency, that tone always controlled discharge timing, usually suppressing the response to the second tone. Complicated interactions took place when the stimulating frequencies bracketed best frequency. The tone nearest best frequency was most effective near threshold, while higher stimulus levels usually favored the low-frequency tone. Nevertheless, the suppression mechanisms appear to provide an effective spatial separation in the cochlea for the response components to each vowel approximation. Fourier analysis of the period histograms yielded qualitatively similar results.
A study of the perception of sentence intonation—Evidence from Danish
Authors: Thorsen Nina G.
Published: October 2005

Ten subjects identified 15 Danish utterances by a human speaker, differing only in their fundamental frequency (F0) course, as being either declarative, nonfinal, or interrogative (forced choice). Responses are closely correlated with F0: the most steeply falling intonation contours are identified as being declarative, the least falling ones as being interrogative, and contours in the middle of the continuum as being nonfinal. Several mutually interdependent parameters in the F0 course may account for the results, the two most powerful ones, however, being the levels of the last stressed and the succeeding unstressed syllable, respectively, in the utterance. In a subsequent experiment, seven subjects identified the same utterances as being either declarative or nondeclarative. The majority of the (formerly) nonfinal sentences were now labeled nondeclarative, rather than being equally distributed among the declarative and nondeclarative categories. When a subset of the same utterances were mutilated, identification deteriorated almost progressively with the number of syllables being cut away from the end of the utterance, but only slightly so until nothing but the first stress group remained; whereas, syllables cut away from the beginning hardly affected identification at all.
Dependence of the ultrasonic properties of biological tissue on constituent proteins
Authors: Goss S. A. , Frizzell L. A. , Dunn F. , Dines K. A.
Published: October 2005

The absorption and speed of ultrasound in mammalian tissues are discussed in relation to the fractional protein content. To a first approximation, biological tissues are shown to correspond to composite materials whose ultrasonic propagation properties are determined by the individual ultrasound properties of their globular and structural protein contents.
Intracellular temperature distribution produced by ultrasound
Authors: Love L. A. , Kremkau F. W.
Published: October 2005

The steady-state temperature profile of a biological cell exposed to ultrasound was calculated by solving the time-independent driven heat flow equation. Three concentric spheres with different thermal conductivities and acoustic absorption coefficients, immersed in a nonabsorbing infinite medium, were used to represent each cell in a dilute aqueous suspension exposed to ultrasound. The inner sphere represented the nucleus, the middle shell the cytoplasm, and the outer shell the plasma membrane. Using representative radii, absorption coefficients, and thermal conductivities, a steady-state temperature rise of 0.13 mK at the cell center was calculated for frequency 1 MHz and intensity 1 W/cm2. Two forms of temperature (T) dependence on distance (r) from sphere center were calculated: (1) T=D−Er2 and (2) T=G+(F/r), where D, E, F, and G are constants which are determined by the intensity, sphere radii, thermal conductivities, and absorption coefficients. The inner sphere had form (1) dependence, the shells had both types of dependence, and the outside medium had form (2) dependence. Variation of the absorption and conductivity parameters indicated a stronger dependence of temperature on absorption coefficients than on thermal conductivities. Temperature rises greater than one degree were not obtained unless the intensity, absorption coefficient, or the inverse of the conductivity was increased by four orders-of-magnitude above the representative values used to calculate the 0.13-mK temperature rise.
Microphones with rigidly supported piezopolymer membranes
Authors: Lerch R. , Sessler G. M.
Published: October 2005

Piezoelectric microphones are described which utilize a rigidly supported, curved polyvinylidene fluoride membrane. The microphones can be designed with a resonance frequency of about 5 kHz and a sensitivity of −55 to −60 dBV per N/m2. The harmonic distortion is typically below 1% for sound-pressure levels up to 100 dB. Advantages of these microphone structures are the well-defined geometry of the membrane, good mechanical and thermal stability, and the possibility of varying the membrane tension and introducing damping by the membrane support.
Optical determination of low ultrasonic powers
Authors: Riley Ward A.
Published: October 2005

An optical nearfield measurement technique is described for determining the ultrasonic powers radiated by circular piston transducers under continuous wave and narrow-band pulsed excitation. The experimental apparatus is simple, relatively inexpensive, and also provides information concerning the acoustic pressure waveform and duty cycle. Continuous wave powers as low as 25 μW can be measured. For narrow-band pulsed excitation, using duty cycles common to some medical diagnostic systems, temporal average powers as low as 25 nW should be detectable.
A theoretical model of ambient noise in a low-loss, shallow water channel
Authors: Buckingham M. J.
Published: October 2005

A theoretical model of ambient noise in an isovelocity, shallow water channel with independent, randomly distributed surface sources is presented. Bottom losses in the channel are assumed to be sufficiently small for the modal energy from distant sources to predominate over the continuous radiation from nearfield sources. For frequencies at which the channel can support about ten or more modes the predicted noise field is essentially homogeneous over a large proportion of the water column away from the boundaries. This allows the vertical spatial coherence of the noise to be expressed in terms of a plane-wave directional density function. The properties of this function are shown to be characteristic of the modal structure of the noise field.
Detection, estimation, and classification with spectrograms
Authors: Altes Richard A.
Published: October 2005

A locally optimum detector correlates the data spectrogram with a reference spectrogram in order to detect (i) a known signal with unknown delay and Doppler parameters, (ii) a random signal with known covariance function, or (iii) the output of a random, time-varying channel with known scattering function. Spectrogram correlation can also be used for maximum likelihood parameter estimation, e.g., estimation of delay or center frequency of a signal. To estimate an analog input signal from its spectrogram, a modified deconvolution operation can be used together with a predictive noise canceler. If no noise is added to the spectrogram, the mean-square error of this signal estimate is independent of the window function that is used to construct the spectrogram. When estimates of specific signal parameters are obtained directly from the spectrogram, these estimates have mean-square errors that depend upon both signal and window waveforms. Spectrogram correlation can be used for classification as well as for estimation and detection. Parameter estimators and detectors are, in fact, specialized kinds of classifiers.
Reconstruction of a two-dimensional reflecting medium over a circular domain: Exact solution
Authors: Norton Stephen J.
Published: October 2005

If a two-dimensional acoustic reflectivity function is defined within the interior of a circle, reflectivity data may be acquired by transmitting acoustic pulses from isotropic elements distributed around the circumference of the circle and recording the resulting backscattered sound as a function of time. If the reflectivity function fulfills the conditions of an ’’idealized’’ weakly reflecting medium, the resulting pulse–echo data may be regarded as the line integrals of this function defined over circular arcs centered at points lying on the circumference of the enclosing circle. In this paper we show that on the basis of these line integrals the unknown reflectivity in the interior of the circle can be expressed explicitly in terms of its line integrals defined over the set of paths consisting of all circular arcs whose centers lie on the circumference of the enclosing circle. We propose that the resulting reconstruction equations could provide the foundation for a new approach to reflectivity tomography. A numerical example is also given.