bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic emission spectra due to leaks from circular holes and rectangular slits
Authors: Wassef W. A. , Bassim M. N. , Houssny-Emam M. , Tangri K.
Published: October 2005

Acoustic waves emitted during a leak are studied both theoretically and experimentally. Two geometries of the leak are considered: a circular hole and a rectangular slit. An expression for the dependence of the frequency of the emitted signal on the pressure difference of the fluid across the leak and the dimensions of the hole or slit is derived. The expression is found to agree with the experimental results obtained for the case of a circular hole over a wide range of pressure differences and hole diameters. It is concluded that a leak may be treated as a resonator that emits acoustic waves at a sharp resonant frequency, besides its well-known characteristics of producing low-frequency noise due to the increase of turbulence in the fluid around the area of the leak.
The use of multidimensional perceptual models in the selection of sonar echo features
Authors: Gorman R. Paul , Sawatari Takeo
Published: October 2005

The development of an accurate and efficient sonar–target classification system depends upon the identification of a set of signal features which may be used to discriminate important classes of signals. Feature selection can be facilitated through the identification of perceptual features used by human listeners in discriminating relevant sonar echoes. This study was conducted to establish a more reliable means of identifying perceptual features in terms of physical signal parameters as an initial step toward the development of an automatic sonar–target classification system. The results of an experiment involving eight subjects and six sonar echoes are presented. A model of the perceptual structure of these echoes was derived from subject similarity judgments using a multidimensional scaling (MDS) technique. It was found that three perceptual features accounted for the similarity judgments made by the human listeners. Echoes modified along candidate physical dimensions were employed to aid in the identification of perceptual dimensions in terms of physical signal parameters. The three perceptual features could be associated with signal parameters involving the amplitude envelope of the echoes.
A small pressurized vessel for measuring the acoustic properties of materials
Authors: Hagelberg M. Paul , Corsaro Robert D.
Published: October 2005

A laboratory system is described that measures the acoustic properties of materials in the frequency range from 10–100 kHz, at pressures to 150 psi (1000 kPa), and from 0°–40° C. By using transducer arrays and broadband pulses together with digital data acquisition and analysis techniques it is possible to contain this (essentially) free-field system in a vessel with a volume of only 0.42 m3. The system provides measurements of complex reflection and transmission coefficients as a continuous function of frequency. From the data one can obtain the following material parameters: sound speed, frequency-dependent sound attenuation coefficient, complex acoustic impedance, echo reduction, and insertion loss. Results are presented for a variety of samples to illustrate the capability of this system.
Gain and efficiency of a short traveling wave heat engine
Authors: Ceperley Peter H.
Published: October 2005

Gain and efficiency equations are derived for a traveling wave heat engine which has a regenerator that is SHORT compared to an acoustic wavelength. A traveling wave heat engine is a modified Stirling engine in which acoustical waves replace the usual pistons and energy is transformed from thermal to acoustical forms and vice-versa, depending on the wave direction. A previous paper examined the energy transformation process for isothermal wave propagation in an infinite regenerator having a temperature gradient [P. H. Ceperley, J. Acoust. Soc. Am. 72, 1688–1694 (1982)]. Similar to that paper, the present paper assumes: small amplitude waves, nonturbulent flow, a constant heat exchange coefficient, and no regenerator end effects. In contrast, the present paper assumes that the wave impedance is NOT determined by the regenerators’s properties but is instead set by the acoustical circuit exterior to the regenerator. In this paper, the normalized power gain and efficiency are calculated and graphed as functions of dimensionless variables. For acoustical impedances of freely propagating waves, and a Prandtl number of 0.7, the efficiency is limited to 10% of Carnot efficiency due to viscous losses in the regenerator. Higher efficiencies are possible with higher impedances, e.g., if the impedance is multiplied by 10, 79% of Carnot efficiencies are possible. Methods of achieving such impedances are discussed. Traveling wave heat pumps are similarly modeled and have comparable potential efficiencies.
Perceptual cues to the voiced–voiceless distinction of final fricatives for listeners with impaired or with normal hearing
Authors: Revoile Sally G. , Holden-Pitt L. , Pickett J. M.
Published: October 2005

Cues to the voicing distinction for final /f,s,v,z/ were assessed for 24 impaired- and 11 normal-hearing listeners. In base-line tests the listeners identified the consonants in recorded /dvC/ syllables. To assess the importance of various cues, tests were conducted of the syllables altered by deletion and/or temporal adjustment of segments containing acoustic patterns related to the voicing distinction for the fricatives. The results showed that decreasing the duration of /v/ preceding /v/ or /z/, and lengthening the /v/ preceding /f/ or /s/, considerably reduced the correctness of voicing perception for the hearing-impaired group, while showing no effect for the normal-hearing group. For the normals, voicing perception deteriorated for /f/ and /s/ when the frications were deleted from the syllables, and for /v/ and /z/ when the vowel offsets were removed from the syllables with duration-adjusted vowels and deleted frications. We conclude that some hearing-impaired listeners rely to a greater extent on vowel duration as a voicing cue than do normal-hearing listeners.
Magnetoelastic surface waves in elastic ferromagnets—I: Orthogonal setting of the bias field
Authors: Maugin G. A. , Hakmi A.
Published: October 2005

The minimal conditions under which a surface mode of the Bleustein–Gulyaev type can be made to propagate in a ferromagnetic substrate are established within the framework of a fully nonlinear, rotationally invariant, and thermodynamically admissible continuum theory of deformable ferromagnets. It is sufficient that the nonlinear elastic body behave isotropically with respect to a field-free configuration and that an intense bias magnetic field set parallel to the limiting plane break this natural material symmetry, thus yielding biased piezomagnetism as also exhibiting the influence of initial fields (internal stresses, stiffening of elasticity coefficients). Then a predominantly Bleustein–Gulyaev (i.e., horizontally shear polarized) mode propagates at a right angle to the bias field, which is, however, bounded differently in frequency and wavenumber depending on whether the wave travels from left to right or right to left. Under the same conditions, due to the nonreciprocity of the Damon–Eshbach magnetostatic surface mode, the coupled upper branch behaves differently depending on the direction of propagation. This corroborates, with slight alterations, previous works by Parekh [Proceedings of the IEEE Ultrasonics Symposium (IEEE, New York, 1972)] and Scott and Mills [Phys. Rev. B 15, 3545–3557 (1977)] and which were performed on the basis of a more conventional approach. The accompanying magnetoelastic Rayleigh mode is discussed, as well as the influence of exchange forces and pinning of the magnetic spins in surface. The work is analytical and, like previous works of the authors on magnon–phonon couplings, relies on the use of small (coupling) parameters and asymptotics.
Statistical energy analysis, structural resonances, and beam networks
Authors: Sablik M. J. , Beissner R. E. , Silvus H. S. , Miller M. L.
Published: October 2005

The statistical energy analysis method is applied to a beam network in a building structure. A method of taking structural resonances into account is introduced into the analysis via the use of ‘‘discretized’’ modal densities. Transfer functions computed from the model beam network are compared over a wide frequency range to experimentally measured transfer functions from an equivalent beam network in an existing building structure in which one of the beams is vibrationally excited. Our results suggest that by taking resonance effects into account, the predictions of statistical energy analysis can be made to display the fine details found in the frequency dependence of transfer functions for real building structures.
Effect of sound-speed profile on differential time-delay estimation
Authors: Robinson E. Richard , Quazi Azizul H.
Published: October 2005

The sensitivity of correlograms to various sound-speed profiles is being studied in order to estimate the impact of refracted multipath acoustic energy on differential time-delay estimation (TDE). To do this, we utilize the generic sonar model to compute the crosscorrelation function for an array of two separated receivers in realistic ocean environments. The effects of the obtained correlogram peaks that show the differential time delays were compared with those predicted when assuming isovelocity profiles. The influence of a signal source’s range and bearing, as well as the vertical separation of the receivers on the correlograms, is demonstrated for each environment considered. Our results indicate that TDE may be significantly influenced by the processing of highly refracted rays of many different types due to the selected sound-speed profile. Also, the Cramer–Rao lower bounds to the standard deviation of time-delay errors at various signal-to-noise ratios are compared with the results that were derived using the generic sonar model and found to be in close agreement.
The relationship of the spiral turns of the cochlea and the length of the basilar membrane to the range of audible frequencies in ground dwelling mammals
Authors: West Christopher D.
Published: October 2005

The number of turns in the cochlear spiral and length of the basilar membrane in several mammalian species were compared with the octave range and the high-and low-frequency limits of hearing. Basilar membrane length and the number of spiral turns were not related. Among ground dwelling mammals, the number of turns in the cochlear spiral was more strongly related to octave range than was basilar membrane length. Basilar membrane length was inversely related to the high-and low-frequency limits of hearing. The best estimates of high-and low-frequency limits and octave range were derived from formulas which included both the number of turns in the cochlear spiral and the basilar membrane length as factors. The number of turns in the cochlear spiral was most highly correlated with the difference between the low-frequency limit of hearing and the lowest frequency mechanically analyzed by the traveling-wave envelope, peak-shift property of the basilar membrane [von Békésy, Experiments in Hearing (McGraw-Hill, New York, 1960)]. The coefficient of correlation for the number of spiral turns and the octave difference between the lowest audible frequency and the lowest frequency distributed as a unique point of maximum displacement along the basilar membrane was r=0.997 (P<.001) at 60 dB SPL. Mechanisms by which the spiral form of the cochlea may affect the motion of hair cells and the selective response of the tectorial membrane to differences among traveling-wave envelope slopes and peak locations were reviewed. It was proposed that in ground dwelling mammals, the spiral form of the cochlea extends the octave range of hearing and that through mechanisms such as these increases the sensitivity of the cochlea to frequencies below the low-frequency peak-shift limit of the basilar membrane.
Speechreading supplemented with formant-frequency information from voiced speech
Authors: Breeuwer M. , Plomp R.
Published: October 2005

The benefit of supplementing speechreading with information about the frequencies of the first and second formants from the voiced sections of the speech signal was studied by presenting short sentences to 18 normal-hearing listeners under the following three conditions: (a) speechreading combined with listening to the formant-frequency information, (b) speechreading only, and (c) formant-frequency information only. The formant frequencies were presented either as pure tones or as a complex speechlike signal, obtained by filtering a periodic pulse sequence of 250 Hz by a cascade of four second-order bandpass filters (with constant bandwidth); the center frequencies of two of these filters followed the frequencies of the first and second formants, whereas the frequencies of the others remained constant. The percentage of correctly identified syllables increased from 22.8 in the case of speechreading only to 82.0 in the case of speechreading while listening to the complex speechlike signal. Listening to the formant information only scored 33.2% correct. However, comparison with the best-scoring condition of our previous study [Breeuwer and Plomp, J. Acoust. Soc. Am. 76, 686–691 (1984)] indicates that information about the sound-pressure levels in two one-octave filter bands with center frequencies of 500 and 3160 Hz is a more effective supplement to speechreading than the formant-frequency information.
Influence of monaural spectral cues on binaural localization
Authors: Musicant Alan D. , Butler Robert A.
Published: October 2005

Seven subjects located, monaurally and binaurally, narrow bands of noise originating in the horizontal plane. The stimuli were 1.0 kHz wide and centered at 4.0–14.0 kHz in steps of 0.5 kHz. The loudspeakers, 15 deg apart, were arranged in a semicircle (0–270–180 deg azimuth). In the first part of the experiment all sounds emanated from the loudspeaker at 270 deg, but their apparent locations varied widely as a function of their center frequency. For each subject, the pattern of location judgments under the binaural listening condition corresponded to that recorded for the monaural condition. In the second part of the experiment the loudspeaker from which each of the same narrow bands of noise emanated was varied in irregular order. Again, monaural location judgments were governed by the frequency content of the noise bands. Binaural location judgments were strongly influenced by the sounds’ frequency composition when the stimuli originated from 315–225 deg, notwithstanding the presence of interaural differences in time and intensity. For narrow bands of noise emanating off midline, monaural spectral cues significantly override binaural difference cues, and they also determine the resolution of front–back ambiguities.
A comparison of three speech coding strategies using an acoustic model of a cochlear implant
Authors: Blamey P. J. , Martin L. F. A. , Clark G. M.
Published: October 2005

Three alternative speech coding strategies suitable for use with cochlear implants were compared in a study of three normally hearing subjects using an acoustic model of a multiple-channel cochlear implant. The first strategy (F2) presented the amplitude envelope of the speech and the second formant frequency. The second strategy (F0 F2) included the voice fundamental frequency, and the third strategy (F0 F1 F2) presented the first formant frequency as well. Discourse level testing with the speech tracking method showed a clear superiority of theF0 F1 F2 strategy when the auditory information was used to supplement lipreading. Tracking rates averaged over three subjects for nine 10-min sessions were 40 wpm for F2, 52 wpm for F0 F2, and 66 wpm for F0 F1 F2. Vowel and consonant confusion studies and a test of prosodic information were carried out with auditory information only. The vowel test showed a significant difference between the strategies, but no differences were found for the other tests. It was concluded that the amplitude and duration cues common to all three strategies accounted for the levels of consonant and prosodic information received by the subjects, while the different tracking rates were a consequence of the better vowel recognition and the more natural quality of the F0 F1 F2 strategy.
Psychophysics of vibrotactile stimulation
Authors: Verrillo Ronald T.
Published: October 2005

The effects of a wide range of stimulus parameters upon the psychophysical responses of subjects are important to an understanding of the functional characteristics of neural systems that underlie responses to cutaneous mechanical stimulation and the interactions that may occur between these systems. This understanding may also be useful to design considerations in the development of devices for tactile communication. This paper begins with a brief description of the two major systems in terms of psychophysical measurements and then focuses on a more detailed examination of possible interactions between them. The effects of time and space variables, such as frequency, temporal and intensity relationships between stimuli, area of stimulation, and surface gradients on the skin, are considered.
A qualitative dynamic analysis of reiterant speech production: Phase portraits, kinematics, and dynamic modeling
Authors: Kelso J. A. S. , Vatikiotis-Bateson Eric , Saltzman Elliot L. , Kay Bruce
Published: October 2005

The departure point of the present paper is our effort to characterize and understand the spatiotemporal structure of articulatory patterns in speech. To do so, we removed segmental variation as much as possible while retaining the spoken act’s stress and prosodic structure. Subjects produced two sentences from the ‘‘rainbow passage’’ using reiterant speech in which normal syllables were replaced by /ba/ or /ma/. This task was performed at two self-selected rates, conversational and fast. Infrared LEDs were placed on the jaw and lips and monitored using a modified SELSPOT optical tracking system. As expected, when pauses marking major syntactic boundaries were removed, a high degree of rhythmicity within rate was observed, characterized by well-defined periodicities and small coefficients of variation. When articulatory gestures were examined geometrically on the phase plane, the trajectories revealed a scaling relation between a gesture’s peak velocity and displacement. Further quantitative analysis of articulator movement as a function of stress and speaking rate was indicative of a language-modulated dynamical system with linear stiffness and equilibrium (or rest) position as key control parameters. Preliminary modeling was consonant with this dynamical perspective which, importantly, does not require that time per se be a controlled variable.
The contribution of fundamental frequency, amplitude envelope, and voicing duration cues to speechreading in normal-hearing subjects
Authors: Grant Ken W. , Ardell LeeAnn H. , Kuhl Patricia K. , Sparks David W.
Published: October 2005

The ability to combine speechreading (i.e., lipreading) with prosodic information extracted from the low-frequency regions of speech was evaluated with three normally hearing subjects. The subjects were tested in a connected discourse tracking procedure which measures the rate at which spoken text can be repeated back without any errors. Receptive conditions included speechreading alone (SA), speechreading plus amplitude envelope cues (AM), speechreading plus fundamental frequency cues (FM), and speechreading plus intensity-modulated fundamental frequency cues (AM+FM). In a second experiment, one subject was further tested in a speechreading plus voicing duration cue condition (DUR). Speechreading performance was best in the AM+FM condition (83.6 words per minute,) and worst in the SA condition (41.1 words per minute). Tracking levels in the AM, FM, and DUR conditions were 73.7, 73.6, and 65.4 words per minute, respectively. The average tracking rate obtained when subjects were allowed to listen to the talker’s normal (unfiltered) speech (NS condition) was 108.3 words per minute. These results demonstrate that speechreaders can use information related to the rhythm, stress, and intonation patterns of speech to improve their speechreading performance.
Modal analysis of a violin
Authors: Marshall Kenneth D.
Published: October 2005

The vibrational behavior of a violin is studied using modal analysis techniques. The violin was considered to be an input–output system, and impact testing was used to measure the frequency response functions for the instrument over the frequency range of 0–1300 Hz. Both the input force and the response acceleration were recorded and analyzed. The results provide a complete modal data base for this violin, information which may be used to characterize the instrument in subsequent analytical studies. It was concluded that the violin, exclusive of the strings, can be modeled as a linear second-order system, and its vibrational behavior can be expressed as a summation of real normal modes. The neck fingerboard of the violin undergoes large amplitude motions at many frequencies, and the ‘‘feel’’ of a violin is related to these lower order modes of the instrument. The A1 air mode and the ‘‘main wood’’ resonance of the top plate are intimately interrelated and both contribute to the radiated sound of the instrument.
Sound hole sum rule and the dipole moment of the violin
Authors: Weinreich Gabriel
Published: October 2005

It is shown both theoretically and experimentally that at long enough wavelengths the radiation pattern of a violin, or of any similar instrument with a sound hole in its shell, becomes that of a dipole. The transition from this region to the one in which the monopole dominates is traced in detail. The experimental method used to measure the ‘‘radiativities’’ of the violin, that is, the amplitudes of the various multipole moments developed per unit force applied to the bridge by the vibrating string, utilizes an extension of the reciprocity principle in which the multipole fields play the rôle of generalized coordinates. Absolute measurements of the radiativity are obtained, and their phases and amplitudes explained in terms of the mechanical motions of the violin shell and the enclosed air.
Effects of heat conduction and sample size on ultrasonic absorption measurements
Authors: Parker Kevin J.
Published: October 2005

The absorption coefficient of a material can be determined by measuring the heating which occurs as a result of ultrasonic irradiation. When narrow focused beams are used to heat a sample, or when the available volume of a material is restricted to small dimensions, then the effect of heat conduction to surrounding unheated regions becomes significant, complicating the relation between measured temperatures and acoustic parameters. In this paper new analytical expressions, which account for radial and axial heat flow in a medium, are derived for the case of Gaussian-shaped ultrasonic beam patterns in thin or semi-infinite absorbing materials. Solutions are given for temperature histories resulting from an ultrasonic impulse (pulse decay method) or a step input (rate of heating method). The use of these equations in absorption measurements is discussed, and experimental results are given. These expressions provide flexibility in choice of laboratory ultrasonic parameters, and the results are especially useful for many biomedical measurements where the volume of tissue available is restricted.
A biological chorus in deep water northwest of Australia
Authors: Kelly L. J. , Kewley D. J. , Burgess A. S.
Published: October 2005

This paper is a summary of observations of a biological chorus in deep waters northwest of Australia. The data were collected from underwater noise recordings made in the course of sonar performance trials at sites in the eastern Indian Ocean. Measurements are made for frequencies between 20 and 800 Hz. Chorus noise at 500 Hz, consisting of continual drumming sounds, was evident for 9–10 h in the evening, with the peak noise level occurring soon after sunset. The noise spectrum level at this peak frequency rose to 72 dB re: 1 μPa2/Hz, approximately 12 dB above the background noise level. Typical spectra and time waveforms for individual noise bursts are presented. The source of the noise is believed to be fish of the family Sciaenidae, commonly known as croakers.
Acoustical aspects of contrastive stress in question–answer contexts
Authors: Cooper William E. , Eady Stephen J. , Mueller Pamela R.
Published: October 2005

A series of experiments was conducted to examine the influence of contrastive stress on intonational patterns of duration and fundamental voice frequency (F0). In a preliminary study, intonational patterns in spontaneous speech were compared with the patterns in oral reading of the transcribed spontaneous material. In both circumstances, a general declination of F0 peaks throughout the course of a sentence was not regularly observed, contrary to earlier findings with oral reading of isolated sentences. Two experiments were then conducted to examine the possibility that the general absence of declination observed here might be due to the influence of sentence focus, following previous results from Swedish showing that declination was not observed consistently in isolated sentences until after the site of focus. In experiment 1, we found no evidence of this restriction on declination in the oral reading of English declaratives. Declination was observed both before and after the focused item in a sentence. Furthermore, our analyses revealed that focus (as manifested by contrastive stress) is generally accompanied by an increase in duration on the focused word and by a sharp drop in F0 following the focused item. In experiment 2, these effects were replicated and extended using longer sentences. In both experiments, the influence of focus was strictly localized to the site of focus in the case of duration, but not F0. The results for both duration and F0 indicate that the influence of focus assignment on these attributes varies systematically as a function of the focus location in the sentence. Finally, the combined elongation effects for focus and utterance-final lengthening were less than would be predicted by an additive model, suggesting the operation of an expandability constraint on segmental lengthening in speech production.
Speech perception ability and psychophysical tuning curves in hearing-impaired listeners
Authors: Stelmachowicz Patricia G. , Jesteadt Walt , Gorga Michael P. , Mott John
Published: October 2005

Performance-intensity functions for monosyllabic words were obtained as a function of signal-to-noise ratio for broadband and low-pass filtered noise. Subjects were 11 normal-hearing listeners and 13 hearing-impaired listeners with flat, moderate sensorineural hearing losses and good speech-discrimination ability (at least 86%) in quiet. In the broadband-noise condition, only small differences in speech perception were noted between the two groups. In low-pass noise, however, large differences in performance were observed. These findings were correlated with various aspects of psychophysical tuning curves (PTCs) obtained from the same individuals. Results of a multivariate analysis suggest that performance in broadband noise is correlated with filter bandwidth (Q10), while performance in low-pass noise is correlated with changes on the low-frequency side of the PTC.
On the resolution of organized spurious pressure fluctuations in wind–wave facilities
Authors: Papadimitrakis Yiannis Alex. , Hsu En Yun , Street Robert L.
Published: October 2005

The structure of the fluctuating wall pressure beneath a turbulent boundary layer influenced by the presence of progressive, mechanically generated water waves of fixed frequency is examined. This pressure was measured by an array of five piezocrystal pressure transducers mounted on the roof of a wind–wave research facility at Stanford University. Experimental results are given for seven wind speeds in the range 1.4–4.0 m/s, with 1-Hz, 2.54-cm nominal amplitude, sinusoidal water waves. The organized component of the wall pressure was found to be contaminated by an acoustic plane and other pressure waves associated with the traveling upstream-reflected water wave. The spurious pressure components are an order of magnitude greater than, and comparable to the traveling downstream wave-induced pressure at the channel roof. The turbulent static pressure fluctuations contain sound contributions in the form of narrow-band noise. The resolution of the various components of the organized wall pressure was achieved by a method utilizing their characteristic dependence upon the streamwise position in the channel, and their traveling wave properties.
Linguistic and acoustic correlates of the perceptual structure found in an individual differences scaling study of vowels
Authors: Rakerd Brad , Verbrugge Robert R.
Published: October 2005

Subjects judged the similarities among a set of American English vowels (/i,I,q,1,v,a,c,o,0,u/) presented in isolation or in a /dVd/ consonantal frame. Individual differences scaling was employed to analyze these similarities data for each of the conditions separately and for the two conditions combined. In all cases, perceptual dimensions corresponding to the advancement, height, and tenseness vowel features were recovered. Given the determinacy of individual differences scaling, this finding is taken to provide strong evidence for the perceptual significance of those features. The perceptual dimensions are considered in relation to various acoustic parameters of the stimuli employed in this study. They are also considered in relation to perceptual dimensions that have been observed in other vowel scaling studies.
The visco-elastic properties of ‘‘weathered’’ crude oil from the Beaufort Sea
Authors: Jones H. W. , Yeatman E.
Published: October 2005

The real and imaginary parts of the shear modulus of samples of crude oil obtained from the Canadian Arctic are reported. These measurements were made over a limited range of temperatures and frequencies. The method used employed measurements of phase change and attenuation at an interface between a quartz bar and the liquid in question, at a grazing angle of incidence. The crude was obtained in a drill test on an Esso Drilling island about 80 miles offshore from Tuktoyaktuk in the Northwest Territories.
Sound wave propagation in fluids with coupled chemical reactions
Authors: Margulies Timothy S. , Schwarz W. H.
Published: October 2005

A hydroacoustic theory is presented which accounts for sound absorption and dispersion in a multicomponent mixture of reacting fluids. A set of first-order acoustic equations without diffusion is assumed for the case where several coupled reactions can occur simultaneously. General results are obtained in the form of a biquadratic characteristic equation (called the Kirchhoff–Langevin equation) for the complex propagation variable χ=−(α+iω/c) in which α is the attenuation coefficient, c is the phase speed of the progressive wave, and ω is the angular frequency. Computer simulations of sound absorption spectra have been made for three different chemical systems, each comprised of two-step chemical reactions using physicochemical data available in the literature. The chemical systems studied include (1) water–dioxane, (2) aqueous solutions of glycine, and (3) cobalt polyphosphate mixtures. Explicit comparisons are made between the exact biquadratic characteristic solution and the approximate equation (sometimes referred to as a Debye equation), previously applied to interpret the experimental data for the chemical reaction contribution to the absorption versus frequency. The relative chemical reaction and classical viscothermal contributions to the sound absorption are also presented. Several discrepancies are discussed that can arise when estimating thermodynamic data (chemical reaction heats or volume changes) for multistep chemical reaction systems when making dilute solution or constant density assumptions.
Geometric considerations in determining the optimum frequency of acoustic propagation in a shallow water waveguide
Authors: Gershfeld David A. , Eller Anthony I.
Published: October 2005

The effect of various basic physical and environmental parameters that determine the optimum frequency of acoustic propagation in shallow water is investigated through the use of a wave-theoretic analytical model which is computationally simple to evaluate. The model is expressed in two alternative forms, the first consisting of a sum over the allowed normal modes in the duct and the second being the Poisson sum transform of the first. The primary objective of the paper is to demonstrate that the optimum frequency is strongly dependent upon the respective depths and separation distance of the source–receiver pair. The high spatial variability in the optimum frequency of propagation results from the competing mechanisms of the preferential excitation and detection of certain modes as a function of source and receiver depths, and the modal attenuation rates as a function of range, mode number, sediment type, and frequency.
The dependence of bottom backscattering on the structure of a layered scattering medium
Authors: Wyber R. J.
Published: October 2005

The classical treatment of backscattering assumes that the signal is returned from a number of point scatterers. The contribution of each scatterer to the total backscattered power is then assumed to add incoherently. This allows the effect of the backscattering to be modeled by simply determining a backscattering coefficient per unit area or per unit volume. This classical model neglects the effects of structure in the scattering media which may arise from layering or schooling of biological scatterers or from layering and structure in the bottom sediment. This paper develops a model for bottom backscattering which takes account of the structure, of the layering and the characteristics of the measurement system. Parameters are identified which should be measured to allow the backscattering to be predicted for any incident angle and any arbitrary signal and transducer configuration.
Ray, mode, and hybrid options for source excited propagation in an elastic plate
Authors: Lu I. T. , Felsen L. B.
Published: October 2005

Impact excited vibrations in a multiwave layer can be represented in terms of ray fields or of normal mode fields. At early observation times, multiply reflected ray fields can be distinguished by their different arrivals whereas at later times, their collective effect is best expressed by the normal modes. Instead of utilizing rays or modes separately, as has been customary, a recently developed hybrid theory for multiwave layered media permits both to be combined self-consistently, and in convenient proportions [Lu et al., Wave Motion 6, 435–467 (1984)]. The hybrid formulation is based on a ray-mode equivalent whereby a given slowness spectral interval can be filled either with rays or with modes subject to a spectral remainder. Moreover, the ray proliferation due to wave coupling at each encounter with a boundary is avoided by introduction of ‘‘eigenrays,’’ which are composed of self-similar combinations of the various wave fields. The general theory is applied to the dilatational and shear waves in an elastic plate. High-frequency motion at given range is calculated in terms of ray fields, normal mode fields, eigenrays, and hybrid combinations, using exact generating spectral integrals and also simplified asymptotic approximations. The numerical results confirm the validity of the ray-mode equivalent and establish conditions where the hybrid scheme offers an attractive option.
Axially focused (glory) scattering due to surface waves generated on spheres: Model and experimental confirmation using tungsten carbide spheres
Authors: Williams Kevin L. , Marston Philip L.
Published: October 2005

When a short tone burst is incident on a tungsten carbide sphere in water, the backscattering response shows a decaying pulse train [L. R. Dragonette, S. K. Numrich, and L. J. Frank, J. Acoust. Soc. Am. 69, 1186–1189 (1981)] which can be attributed to a specular reflection and repeated circumnavigations of other waves. We experimentally investigate the angular dependence of Rayleigh wave contributions as the receiver is moved away from the backscattering axis. It is found that this angular dependence can be approximately described by J0(β γ), where β depends on the frequency of the sinusoidal tone burst used (or equivalently the ka of the sphere) and γ measures the angle relative to the backscattering axis. We show how this form of angular dependence may be attributed to a weak axial focusing along the backward direction. This form is consistent with properties derived from Sommerfeld–Watson transforms for scattering from spheres. Our model includes a prediction of how β will vary with ka. The model is given in a general sense and then specialized to tungsten carbide for experimental confirmation. Experimental results in the range 30<ka<100 are compared with theory. Some implications concerning the backscattering from nonspherical objects are also discussed.
A fast algorithm solution of the inverse problem for a layered acoustic medium probed by spherical harmonic waves
Authors: Yagle Andrew E. , Levy Bernard C.
Published: October 2005

A continuous layered medium is probed by sinusoidal spherical waves from a point harmonic source, and the reflection response of the medium is measured. By performing this experiment at two different source frequencies, the separate density and sound-speed profiles ρ(z) and c(z) are recovered. Two experimental configurations are considered: the case in which the inhomogeneous medium is confined between two infinite homogeneous half-spaces and is probed from the upper half-space, and the case in which the inhomogeneous medium is bounded above by a free-surface, at which the source is located. Layer-stripping fast algorithm solutions to both of these inverse problems are obtained and illustrated with examples. The algorithms are interpreted physically as constructing distributions of image sources that simulate the medium response at each depth.
Energy streamlines of a sound source
Authors: Waterhouse R. V. , Yates T. W. , Feit D. , Liu Y. N.
Published: October 2005

A method is presented for computing the energy streamlines of a sound source. This enables charts to be plotted showing, as continuous lines, the flow paths of the sound energy from the vibrating surface to the nearfield and beyond. Energy streamlines appear to be a new construct; they have some similarities to the velocity streamlines used in fluid dynamics. Examples of the energy streamlines are given for the point-driven plate in water.
Theory and calculations for an intrinsically irreversible acoustic prime mover using liquid sodium as primary working fluid
Authors: Swift G. W. , Migliori A. , Hofler T. , Wheatley John
Published: October 2005

A theory describing a thermoacoustic heat engine using a liquid as primary working substance is developed and applied to the design of a high-power prime mover using liquid sodium. After an introduction that explains the physical principles of this type of engine in a heuristic way, we derive expressions for the acoustic variables and consequent energy flows in the engine. These expressions are easily understandable only in special limiting cases; to discuss practical applications we resort to numerical computations. We find that a reasonably designed thermoacoustic prime mover using liquid sodium and operating between thermal reservoirs at 1000 and 400 K can generate about 60 W/cm2 of acoustic power at about (1)/(3) of Carnot’s efficiency. We also discuss the relative importance of various sources of inefficiency, such as viscosity, that are not essential to the production of power in this type of engine but are unavoidable in practice because of the thermophysical properties of real substances.
Nearfield acoustical holography using an underwater, automated scanner
Authors: Williams Earl G. , Dardy Henry D. , Fink Richard G.
Published: October 2005

A computer-controlled, three-axis Cartesian scanning facility has been constructed in a large water tank to provide accurate preprogrammed contouring with hydrophone probes. As the scanner moves on the preprogrammed contours, usually located very close to a radiating object, the pressure field is sampled at discrete points until a two-dimensional (2D) pressure map is obtained. This pressure map is essentially a hologram containing amplitude and phase information which can be processed with a computer using a technique called nearfield acoustical holography (NAH). This processing provides the pressure, vector velocity, and vector intensity anywhere in the space from the surface of the source to the farfield. Backward projection (reconstructing the field at the source surface) provides surface velocity and pressure (fluid loading) on the actual source and thus, through the continuity of the normal velocity, provides both the amplitude and phase of the structural vibration of the source. Through a series of experiments and theoretical modeling, the accuracy of NAH as applied to underwater acoustic sources is shown to be excellent.
Acoustic characteristics of perceived versus actual vocal age in controlled phonation by adult females
Authors: Linville Sue Ellen , Fisher Hilda B.
Published: October 2005

The purpose of this investigation was to obtain information on the acoustic characteristics of women’s voices as a function of perceived versus actual age. Tape recordings of whispered and normally phonated /æ/ vowels were obtained from 75 women in three age groups (25–35, 45–55, and 70–80 years). One-second segments of phonemically representative /æ/ vowels were played to 23 listeners for relative age judgments. Phonated vowel productions were analyzed in terms of mean fundamental frequency, fundamental frequency standard deviation, and jitter ratio, as well as  F1 and  F2 frequencies. Whispered vowels were analyzed only in terms of  F1 and  F2 frequencies. Multiple regression analysis revealed that older age judgments based on phonated vowels were significantly associated with higher fundamental frequency standard deviation values and lower mean fundamental frequency values. Older age judgments based on whispered vowels were significantly associated with lower F1 frequencies. Results of this investigation suggest that both phonatory and resonance features play a role in defining age characteristics of women’s voices. Acoustic cues associated with perceived age generally agreed with acoustic findings as a function of actual age.
Constancy of (acoustic) relative timing measures in phrase-level utterances
Authors: Weismer Gary , Fennell Ann M.
Published: October 2005

The hypothesis that acoustic measures of relative speech timing remain constant across large changes in speaking rate was tested for fluent utterances produced by normal and neurogenically disordered speakers. For all speakers, relative timing tended to be statistically invariable across conversational and fast speaking rates. This finding was considered especially interesting in the case of speakers with dysarthria and apraxia of speech, because absolute measures of speech timing associated with these disorders are typically aberrant. A post hoc analysis of relative variability across speakers showed the ratio measures to be consistently less variable than measures of absolute interval duration. The greater similarity across speakers of ratio measures, as compared to interval measures, was taken to mean that characterizing the temporal structure of articulatory sequences in terms of relative timing is an appropriate way to capture an important aspect of the biological constraints associated with speech production.
Influence of carbon black fillers on acoustic properties of polychloroprene (neoprene) elastomers
Authors: Capps Rodger N.
Published: October 2005

The effects of carbon black type and loading, and variation of base polymer, on a series of polychloroprene rubbers (neoprenes) have been investigated. Two common types of neoprenes, each with a lead oxide cure system, were used. The acoustic responses of these materials were characterized for extensional wave propagation in air by a resonance technique and longitudinal wave propagation in water through the use of a high-frequency sing-around device and an underwater acoustic impedance tube. The viscoelastic properties of neoprene elastomers were found to be strongly influenced by both the degree of loading and average particle size of the carbon black used. The results are discussed in terms of mechanisms of interaction between the carbon black filler and the gum phase of the elastomer.
Precision of active sound intensity measurements in a progressive and a nonprogressive field
Authors: Nicolas Jean , Lemire G.
Published: October 2005

The estimated sound intensity is compared to the exact intensity in order to study the precision of active sound intensity measurement, for the cases of a simple progressive field and any sort of nonprogressive fields. The progressive field is produced by an harmonic monopole, whereas the nonprogressive field is produced by two harmonic monopoles of variable strength ratio and geometric conditions. The analysis is performed in the time domain. In the progressive field case, a general formulation of the error is obtained which simplifies in limiting cases to forms already published in the literature. In the nonprogressive field case, emphasis is put on the formulation of the exact phase gradient and of the total pressure field resulting from the two sources. The formulation of the uncertainty points out considerable errors at low frequencies due to instrumental phase mismatch and at high frequencies due to finite approximation of amplitude and of the phase gradient. Finally, the ratio of the sound intensity to the pressure as an indicator of the accuracy of sound intensity measurement is discussed.
Influence of following context on perception of the voiced–voiceless distinction in syllable-final stop consonants
Authors: Repp Bruno H. , Williams David R.
Published: October 2005

This paper reports acoustic measurements and results from a series of perceptual experiments on the voiced–voiceless distinction for syllable-final stop consonants in absolute final position and in the context of a following syllable beginning with a different stop consonant. The focus is on temporal cues to the distinction, with vowel duration and silent closure duration as the primary and secondary dimensions, respectively. The main results are that adding a second syllable to a monosyllable increases the number of voiced stop consonant responses, as does shortening of the closure duration in disyllables. Both of these effects are consistent with temporal regularities in speech production: Vowel durations are shorter in the first syllable of disyllables than in monosyllables, and closure durations are shorter for voiced than for voiceless stops in disyllabic utterances of this type. While the perceptual effects thus may derive from two separate sources of tacit phonetic knowledge available to listeners, the data are also consistent with an interpretation in terms of a single effect; one of temporal proximity of following context.