bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved methods for determining eigenfunctions in multi-layered normal-mode problems
Authors: Hall Marshall , Gordon David F. , White DeWayne
Published: October 2005

This paper derives and illustrates the utility of the derivative of a determinant that arises from the solution of the wave equation in a multi-layered medium. The horizontal wavenumbers at which the determinant is zero are the eigenvalues of the solution. The derivative of the determinant with respect to the horizontal wavenumber therefore can be an aid in finding the roots (zeros). More importantly, the eigenfunction normalization constant is shown to be a function of this derivative. Two types of boundary are discussed, an impedance boundary and an infinite half-space. The normalization using the derivative of the determinant is shown to apply to both types. The derivative of the determinant is also useful in evaluating mode group velocities. An algorithm for the efficient determination of the derivative of a determinant is given. This algorithm includes a rapid computational technique that applies special properties of matrix operations and utilizes the sparseness of the determinant.
Effect of continuous traffic noise on percentage of deep sleep, waking, and sleep latency
Authors: Thiessen G. J. , Lapointe A. C.
Published: October 2005

When subjected to alternating quiet nights (32 dB) and noise nights (equivalent levels of 47 dB) a group of 14 subjects showed an average increase in the fraction of deep sleep of about 2.5% resulting from the traffic noise. Another group of 12 subjects whose noise nights were at 60 dB had an average of 4.6% increase in deep sleep during these nights. The number of wakings also increased for both groups but, as was found before, this adapted rapidly with the number of nights. The average latency of sleep onset does not appear to be affected by the traffice noise but individual differences are great and may be of opposite sign. Latency of sleep onset and waking both show appreciable ‘‘laboratory effect’’ which takes longer to disappear than the one or two nights usually assumed.
Hybrid adaptive filtration for seismic event location
Authors: Fletcher Donnie , Schnitta-Israel Bonnie , Dorman Jim
Published: October 2005

Certain techniques of adaptive filtration, time delay estimation, and minimum variance parameter estimation were synthesized into a hybrid adaptive filtration technique and applied to a problem in seismic event location. Processing seismic wave data generated by strong impulsive source and recorded by a geophone array, we succeeded in doubling the range of detection previously achieved by conventional beamforming methods. The degree of accuracy of bearing estimation was also improved significantly. Additionally a method of observing the nature of the roots of the AR process can replace the conventional power spectrum method for observing wave fronts. The root migration was found to be very sensitive to signal structure.
Pressure-flow relationships in two models of the larynx having rectangular glottal shapes
Authors: Scherer Ronald C. , Titze Ingo R. , Curtis James F.
Published: October 2005

The pressure-flow equations used in computer simulation studies of phonation lack experimental validation. Two polyester resin models of the laryngeal airway with rectangular glottal ducts were constructed in order to obtain the relationships between translaryngeal pressure drop and volume flow through the airway. The results are in disagreement with the early estimates of Wegel [Bell Syst. Tech. J. 9, 207–227 (1930)], but match the predictions given by Ishizaka and Matsudaira [SCRL Monograph No. 8 (1972)] to within approximately ±10% for typical translaryngeal pressures for speech, with larger discrepancies being found for the model with the larger glottal diameter. The equation given by van den Berg et al. [J. Acoust. Soc. Am. 29, 626–631 (1957)] may not be properly compared because their supraglottal pressure hole location may have been different from that used in the present study. The data from the two models also are compared to recent empirical studies using an enlarged model of the larynx [J. Gauffin et al., Conference on Vocal Fold Physiology, Madison (1981)].
Modeling of acoustic propagation across warm-core eddies
Authors: Lawrence Martin W.
Published: October 2005

A theoretical investigation has been made into the effect on acoustic propagation of oceanic fronts at the edge of warm-core eddies. The investigation utilized modeling of acoustic propagation using the parabolic approximation to the wave equation. Propagation was examined using typical parameters for a wintertime warm-core eddy in the Tasman Sea. Propagation across the eddy boundary (at a frequency of 100 Hz) is shown to create a second series of convergence zones, in addition to the normal series. This occurred for propagation both into and out of the eddy. For a source outside the eddy, energy is shown to strongly couple from deep refracted paths to mixed layer paths within the eddy. The eddy boundary was found to have significant effects on convergence zone properties. Acoustic propagation was also modeled using parameters from a particular realization of a summertime warm-core eddy in the Tasman Sea (for which realization there was environmental and acoustic data available). This eddy had a surface duct and a separate subsurface duct. Reasonable agreement between model and experiment was found for source and receiver both in the subsurface duct at frequencies from 50 to 1000 Hz; disagreement occurred at 25 Hz. However, for source in surface duct but receiver in subsurface duct, the agreement was poor at most frequencies. The effect of minor variations in oceanic and experimental parameters was examined to determine the experimental resolution required of these parameters.
Underwater acoustic sensor arrays using angle of arrival diversity to counteract fading in a multipath medium
Authors: Haber Fred , Yeh Chien-Chung
Published: October 2005

The statistical properties of the output of a sparse array of independently suspended acoustic sensors submerged in the sea and exposed to vertically dispersed multipath signal arrivals typical of deep underwater propagation, are studied here. Horizontal components of element positions are subject to drift and defusion and are not accessible to manipulation; vertical components are assumed nontime varying once element depth has been set. Element positions are assumed known having been obtained using an independent measurement procedure not dealt with in this paper. The mean power pattern of such arrays in two dimensions with all elements at one depth and in three dimensions with different distributions of vertical positions, are obtained assuming conventional beamforming. Conventional focusing is found to be inefficient for signal energy collection and the output obtained is subject to variation typical of fading environments. To overcome these effects, multiple vertical beams are formed using the three-dimensional array, the beams looking at different angles to resolve the multipath rays. The multiple beams, constituting a collection of angle-of-arrival diversity branches are combined in customary ways. Beam separation to minimize noise correlation between branches is determined. Simulation results for such a system using various diversity combining techniques are presented and the improvements obtained are discussed.
A model for wave propagation in gassy sediments
Authors: Bedford A. , Stern M.
Published: October 2005

A variational method of deriving equations of motion for mixtures is used to obtain a theory for a granular sediment saturated by a liquid which contains bubbles of gas. The theory is an extension of the Biot–Stoll model for wave propagation in saturated sediments. Wave velocity and attenuation are determined for a water-saturated model sediment containing a small volume of air bubbles. It is verified that the model predicts the qualitative features that have been observed experimentally in gassy sediments. At frequencies below the bubble resonance frequency (BRF), the phase velocity is substantially decreased by the presence of the bubbles. Near the BRF, the attenuation increases markedly. Above the BRF, the phase velocity and attenuation approach the values which they would have if no bubbles were present.
Back reflection of ultrasonic waves from a liquid–solid interface
Authors: Norris Andrew N.
Published: October 2005

A new acoustic phenomenon has recently been observed in experiments where a bounded beam of ultrasound is incident upon a smooth liquid–solid interface. A significant amount of coherent radiation is found to be backscattered in the general direction of incidence. The angle of back reflection is observed to be equal to the critical Rayleigh angle or leaky wave angle. Most of these observations were made during experiments on the Schoch displacement effect, and therefore it has been tacitly assumed that the back reflection is strongly dependent upon the angle of incidence, as is the case for the beam shifting in the Schoch effect. We present a theoretical basis for this new phenomenon. A two-dimensional incident beam of Gaussian profile is considered. By a careful analysis we isolate that part of the field on the interface which has Fourier components corresponding to backward propagating waves in the liquid. This subset of the total wave field is then considered separately and it is shown to display a maximum in a certain direction, close to the critical Rayleigh angle. This peak in the angular pattern of the scattered field corresponds to an evanescent reflection boundary. We discuss the dependence of the effect upon certain parameters. The amplitude is shown to decrease as the beam width is increased, and it increases with increasing Schoch displacement. This backscattering is present for all angles of incidence; there is nothing inherently special about the Rayleigh angle.
Weak and short waves in one-dimensional inhomogeneous materials with memory.II
Authors: Tokuoka Tatsuo
Published: October 2005

Wave propagation in a material with memory is investigated theoretically. The material is assumed to be one-dimensional and inhomogeneous and to possess effects due to memory. Geometrical acoustics is assumed to hold for a weak wave with short wavelength. Order of magnitude estimations are made via the equation of motion. By equating first-order terms, the propagation velocity is determined and in general found to depend upon waveform. When the material has weak memory the propagation velocity is independent of waveform. Likewise, by equating second-order terms, an amplitude equation is obtained for a material with weak memory and found to depend upon waveform. The propagation velocity on the wave front and the amplitude equation of acceleration on it are identical with those derived using the method of singular surface.
Steady-state oscillations of gas bubbles in liquids: Explicit formulas for frequency response curves
Authors: Francescutto Alberto , Nabergoj Radoslav
Published: October 2005

The steady-state nonlinear oscillations of a spherical gas bubble in an incompressible, viscous liquid subject to an acoustic pressure field are investigated by the multiscale perturbation method. As a result, simple formulas for the frequency response curves in the regions of the main resonance, first and second ultraharmonic and first and second subharmonic, are obtained to second order in the expansion.
A wake-scattering experiment in thermally stratified water
Authors: Pelech I. , Zipfel G. G. , Holford R. L.
Published: October 2005

An underwater object moving through a stable thermocline leaves a trail of fluctuations in pressure, velocity, and temperature; the attendant nonuniformities in the index of refraction scatter acoustic waves. An acoustic scattering experiment was performed in a flooded quarry, which has a stable thermocline with a typical gradient of 1.0 to 1.5 °C/ft and a Brunt–Väissälä period of about 70 s. The experiment used a self-propelled, slender model about 9 in. in diameter and 48 in. long. The speed was 3 ft/s, the Froude number was 300, and the Reynolds number was 1.5×105 based on the body diameter. A 75-kHz directional sonar, driven with 0.1-ms pulses at a rate of 10/s, insonified the wake; the scattered return was received by a directional hydrophone. The transducer-wake geometries included vertical, horizontal, and 45° backscatter. A strong backscattered signal was received for several Brunt–Väissälä periods; in one instance, for ten periods. The amplitude of the scattered return compares favorably with theory.
Site and frequency dependence of ambient noise in the Northeastern Pacific Ocean
Authors: Wilson James H.
Published: October 2005

One-hour averages of omidirectional ambient noise measurements at 60 and 165 Hz are analyzed for two nearby, deep ocean sites in the Northeastern Pacific during February and March 1981. Site A is a high noise site and is located near major east–west shipping lanes and near major Pacific storm paths. Site B is a lower noise site and is located approximately 450 nm from site A away from major shipping lanes and near major Pacific storm paths. The site and frequency dependence of ambient noise is found to be highly variable with shipping noise being totally dominant at 60 Hz at site A and storm noise being totally dominant at 165 Hz at site B. Both shipping and storm noise can dominate the 165-Hz site A or 60-Hz site B noise levels depending on weather conditions. Storms have a possible indirect effect on shipping noise, since very low noise periods occur in between storms, especially when the storm passes nearby the site. A limited number of WMO ships sampled indicate that ships slow down or stay in port during storms. Average omnidirectinal noise levels at 60 Hz at both sites and at 165 Hz at site A were 3 to 4 dB lower during a stormy week than they were during a relatively calm week. Array noise gain measurements at site B indicate that the coherence of noise during stormy periods is much less than it is during calm periods. Generally, this implies that the increase in beam level at 165 Hz, caused by storm noise, will be significantly less than corresponding increase in omnidirectional noise levels.
On active and passive cochlear models—Toward a generalized analysis
Authors: de Boer E.
Published: October 2005

Simple cochlear models can show a peak in their response but only of a limited magnitude. The constraints limiting the size of this peak are studied in this note, for the short-wave as well as the long-wave case. It is found that a sharply rising response is impossible in a model in which the basilar membrane can only absorb acoustical energy. To attain a model response that is comparable to the response found in the most recent experiments, the basilar membrane must be assumed to be capable of adding acoustic energy to the fluid waves.
Relation between discharges in auditory nerve fibers and the whole-nerve response shown by forward masking: An empirical model for the AP
Authors: Dolan D. F. , Teas D. C. , Walton J. P.
Published: October 2005

Whole-nerve action potentials evoked by a standard click were recorded from a gross electrode on the RW and the discharges of auditory nerve fibers to the same standard click were recorded from micropipette electrodes in the auditory nerve. The effect of a preceding tone burst (2, 4, or 8 kHz) upon the responses was measured for forward-masker intensities from 20 to 80 dB SPL. All forward maskers reduced the discharges of auditory nerve fibers to the standard click with the greatest reduction occurring for fibers with characteristic frequencies (CFs) near the masker frequency. The 4- and 8-kHz forward maskers produced similar effects on N1, P1, and N2 of the RW response. However, the 2-kHz foward masker produced enhancement at P1 and N2 in the RW response to the standard click. An empirical summation model of estimated elemental waveforms at latencies dependent on CF produces synthesized AP response waveforms which are similar to the observed RW response. The model permits the exclusion of discharges from segments along the cochlear partition in a manner similar to the effect of a forward masker. Alterations in the synthesized waveforms due to the exclusion of segments are similar in direction to the alterations observed in the RW responses for forward masking.
Responses of auditory-nerve fibers to consonant–vowel syllables
Authors: Sinex Donal G. , Geisler C. Daniel
Published: October 2005

The discharge patterns elicited by a set of synthesized consonant–vowel (CV) syllables were studied in the auditory nerve of the cat. The syllables, heard as /ba/, /da/, or /ga/, included a 25-, 50-, or 75-ms formant transition followed by a segment of steady-state vowel. The data were analyzed in terms of average discharge rate and in terms of the synchrony of discharges with respect to various spectral components of the stimuli. The results differ slightly from those of previous reports of the responses to vowels [Sachs and Young, J. Acoust. Soc. Am. 66, 470–479 (1979); Young and Sachs, J. Acoust. Soc. Am. 66, 1381–1403 (1979)], in that average discharge rates appear to provide more information about the spectra of formant transitions than they do about the spectra of steady-state vowels. This difference reflects changes in the spectrum of the syllable produced by movements of the formants. The synchrony of discharges, however, may provide more detailed information about the spectra of CVs than does average discharge rate. Each fiber’s response at a particular peristimulus time may be characterized by the ‘‘dominant response component,’’ the largest peak in the Fourier transform of the period histogram. The trajectories of the first three formants can be inferred from changes in the ‘‘dominant components’’ in a sample of fibers.
Successive versus simultaneous comparison in auditory intensity discrimination
Authors: Green David M. , Kidd Gerald , Picardi Maria C.
Published: October 2005

The ability to discriminate between two brief sounds having identical frequency components, but differing in the intensity of one or more of the components, is studied. The stimulus manipulations include randomizing the overall intensity of the sounds, varying the number and spacing of the components, and varying the interval of time between the sounds. The results from the experiment in which interstimulus interval is manipulated clearly support a profile analysis mechanism that computes two rough spectral analyses, stores a classification of these spectra in memory, and compares the two stores. This profile mechanism involves a simultaneous comparison of different components of the complex, some remote from the signal frequency, rather than a successive comparison of the difference in intensity at the signal frequency. The simultaneous comparison process is more sensitive when the profile is composed of many components spaced over a wide frequency range.
Sleep disturbance before and after traffic noise attenuation in an apartment building
Authors: Öhrström Evy , Björkman Martin
Published: October 2005

A study on traffic noise sleep disturbance was made in an apartment building before and after the installation of noise insulating windows. Three tenants completed a questionnaire each morning one week before and one week after the insulation of windows, and body movements during sleep were recorded during these periods. All persons demonstrated a decrease in the number of body movements after the windows had been insulated and two reported improved sleep quality. The results suggest that subjectively judged sleep quality as well as recordings of bed movements are useful tools for evaluating actions to reduce noise.
Do off-frequency simultaneous maskers suppress the signal?
Authors: Weber Daniel L.
Published: October 2005

Psychophysical tuning curves obtained in forward masking show greater tuning than those obtained in simultaneous masking. This difference is often attributed to the contribution of suppression to the masking produced by off-frequency simultaneous maskers. In this experiment, simultaneous-masking tuning curves were obtained using a 195-ms, 1-kHz sinusoidal signal presented at 40 dB SPL. If the maskers identified in this procedure reduce signal detectability by suppressing the response to the signal, then it should be possible to demonstrate suppression effects between stimuli with the parameters of the masker and signal. One conventional method for demonstrating suppression is to show a reduction in the amount of forward masking produced by one stimulus when a second stimulus is added to it. When used to test the effect of the masker upon the signal, this procedure does not show the suppression supposedly produced by the off-frequency maskers. These data are consistent with an alternative explanation involving only excitatory interactions between masker and signal.
Pitch of components of complex tones
Authors: Peters Robert W. , Moore Brian C. J. , Glasberg Brian R.
Published: October 2005

Subjects made pitch matches to individual components in complex tones consisting of either the 4th to 7th or the 1st to 7th harmonics of a 200-Hz fundamental. All components were at equal levels (either 31-, 51-, or 71-dB SPL per component) and the matching pure tone was equal in level to the component being matched. Attention was drawn to the component to be matched either by giving the matching tone an initial frequency close to that of the component (standard condition) or by suppressing and then introducing the component (emergent condition). The pitch matches did not differ significantly for the two conditions, and did not change with overall level. For two subjects, matches to components in the context of the complexes were very close to matches obtained for the components presented in isolation. For a third subject, matches in context were shifted slightly upwards for the lowest component, and downwards for the highest component. A control condition showed that subjects were able accurately to match a small shift in frequency of one component in a four-tone complex. An adapative forced-choice method described by Jesteadt [Percept. Psychophys. 28, 85–88 (1980)] was also used to estimate the pitches of the components. A very slight bias was apparent in the results, but the pitches of components in context were again found to be very close to those of components in isolation.
Propagation of finite-amplitude ultrasonic waves in air—II. Plane waves in a tube
Authors: Gaete-Garretón Luis , Gallego-Juárez Juan A.
Published: October 2005

This paper is concerned with an investigation of the nonlinear behavior of sinusoidal plane progressive acoustic waves of finite amplitude in air at a frequency of about 21 kHz. The various stages in the distortion of the wave have been experimentally studied and the results compared with theoretical models. The experiments were done in a tube 5.5 m long and 8-mm internal diameter with an absorbing termination. The acoustic source used was a prestressed piezoelectric sandwich transducer with a titanium stepped mechanical amplifier, the small end of which was the piston that produced the high-amplitude motion inside the tube. This source was capable of generating a nearly pure sinusoidal wave at sound pressure levels up to about 155 dB (re: 0.0002 μbar). Interestingly, as compared to previous reports on this field, the use of a high frequency has allowed the study of all the propagation regions (including the old age region) of the wave using a short length tube.
Acoustical characteristics of rigid fibrous absorbents and granular materials
Authors: Attenborough Keith
Published: October 2005

A model is developed that predicts the acoustical characteristics of rigid fibrous absorbents soils and sands from five parameters. These parameters are porosity, flow resistivity, tortuosity, steady flow shape factor, and dynamic shape factor. Tortuosity is shown to be related simply to porosity and a simple relationship between the shape factors is postulated. In practice, therefore, only two measurable parameters (porosity and flow resistivity) are required together with a third shape factor parameter, appropriate values of which are deduced for the media of interest by comparison with appropriate measurements. The model is shown to give superior predictions to those of empirical formulae that use flow resistivity only, particularly when applied to high flow resistivity soils and sands at low frequencies such that the stated range of validity of the empirical formulae is exceeded.
Coupled mode solution for a cylindrically symmetric oceanic waveguide with a range and depth dependent refractive index and a time varying rough sea surface
Authors: Boyles C. Allan
Published: October 2005

This paper uses the technique of coupled, local normal modes to obtain an exact numerical solution of the Helmholtz equation for the case of a two-dimensional, oceanic waveguide which can possess both horizontal and vertical sound-speed gradients as well as a time varying rough sea surface. By a two-dimensional waveguide, we mean one that can be described by two coordinates; viz., a radial coordinate r to describe variations with horizontal range and a depth coordinate z to describe variations with depth below the sea surface. The speed of sound in the waveguide c(r, z) can then be a function of both range and depth.
Geometric dispersion of acoustic signals propagated in a deep ocean channel
Authors: Flowers Kenneth D.
Published: October 2005

In this paper we consider two sinusoidal signals generated in such a way as to have a constant frequency ratio. Then, except for dispersive effects of the propagation channel, the two signal frequencies should remain correspondingly related at a distant receiver. As a measure of this relationship a correlation function is defined for signals of different frequencies. The signals are assumed to have a frequency relationship ω2=qω1, where q is a real number. As an illustration of the use of this correlation function, model calculations are made of signals propagated over long ranges through the deep ocean. It is determined that geometric dispersion in a deep ocean channel degrades the correlation slightly but limits the precision to which q may be evaluated. The variations in q are directly proportional to q. It is found that the correlation function degrades with signal-to-noise ratio, q, and frequency. In general, it is concluded that the dispersive effects of the ocean channel at long range can be significant for broadband signals when signal coherence is an important consideration.
A cautionary note on the use of range-dependent propagation models in underwater acoustics
Authors: Henrick R. F.
Published: October 2005

A caution is given to the users of range-dependent models that utilize single ocean sound-speed profiles for discrete range intervals. It is shown that, if new profiles are not input every few kilometers, the effect of the discontinuities in the ocean may produce erroneous results. An example illustrates potential errors of as much as 18 dB using the Parabolic Equation Method (PE) to compute propagation through a Gulf Stream ring. It is argued that range interpolation routines should be used to produce closely spaced profiles as a standard part of applying these acoustic propagation codes.
Vibration of a plate of arbitrary shape with free and simply supported mixed edges
Authors: Nagaya Kosuke
Published: October 2005

This paper is concerned with a method for solving vibration problems of a plate of arbitrary shape with free and simply supported mixed edges. In the analysis the exact solution of the equation of motion which includes terms representing the reaction forces of the simply supported edges is applied. The boundary conditions along the edges of arbitrary shape have been satisfied directly by making use of the Fourier expansion collocation method which has been developed by the author on vibration, dynamic response, and wave propagation problems of membranes, plates, and rods with arbitrarily shaped boundaries. The equation for finding the eigenfrequencies of plates of arbitrary shape with free and simply supported mixed edges has been obtained. As applications of the present result, numerical calculations have been carried out for polygonal plates, trapezoidal plates, truncated elliptical plates, and parabolic plates with the mixed edges.
Onset spectra and formant transitions in the adult’s and child’s perception of place of articulation in stop consonants
Authors: Walley Amanda C. , Carrell Thomas D.
Published: October 2005

Stevens and Blumstein [Perspectives on the Study of Speech (Erlbaum, Hillsdale, NJ, 1981)] have proposed that the global shape of the CV syllable onset spectrum provides the listener with a primary and contextually invariant cue for place of stop consonant articulation. Contextually variable formant transitions are, in contrast, claimed to constitute secondary cues to place of articulation that, during development, are learned through their co-occurrence with the primary spectral ones. In the two experiments reported here, these claims about the relative importance of the onset spectrum and formant transition information were assessed by obtaining adults’ and young children’s identifications of synthetic stimuli in which these two potential cues specified different places of articulation. In general, the responses of both adults and children appeared to be determined by the formant transitions of the stimuli. These results provide little support for the claim that sensitivity to the global properties of the onset spectrum (as described by Stevens and Blumstein) underlie place of articulation perception or for Stevens and Blumstein’s primary versus secondary cue distinction. Rather, these findings are consistent with the view that dynamic, time-varying information is important in the perception of place of articulation.
The scattering of ultrasonic waves by polycrystals. II. Shear waves
Authors: Hirsekorn Sigrun
Published: October 2005

The theory of ultrasonic propagation in polycrystals presented in a previous paper is used to calculate the scattering coefficient and the phase and group velocities of plane shear waves in polycrystals of cubic symmetry with randomly orientated grains. The calculation was done in second-order perturbation theory using the assumption that the changes in the elastic constants and in the density from grain to grain are small. The asymptotic values at low κa (Rayleigh scattering) are exactly the same as the well-known results from Bhatia and Moore. Numerical calculations are carried out for some examples.
Relationships between vocal intensity and noninvasively obtained aerodynamic parameters in normal subjects
Authors: Tanaka Shinzo , Gould Wilbur J.
Published: October 2005

The relationships between vocal intensity (sound pressure level) and intrapulmonic pressure, mean flow rate, and aerodynamic powere were investigated in ten normal subjects. The intrapulmonic pressure was measured noninvasively and simultaneously with sound pressure level and mean flow rate during sustained phonation of the vowel /a/ by means of plethysmographic and pneumotachographic methods. The aerodynamic power was calculated as intrapulmonic pressure times mean flow rate. The averaged values for the normal subjects represented (sound power)∝(intrapulmonic pressure)3.18, (sound power)∝(mean flow rate)9.62, and (sound power)∝(aerodynamic power)2.44, where sound power at the open end of the pneumotachograph was estimted from sound pressure level. Vocal efficiency was defined as the ratio of sound power to aerodynamic power. Individual variation of vocal efficiency (in dB) was satisfactorily small in the normal subjects, and was determined by the simple addition of individual variations of intrapulmonic pressure and mean flow rate (in dB) from the averaged values. These findings strongly suggested that the comparison of those three measurements against normative data for normal subjects such as provided by this study is useful in evaluating and clarifying the ineffective voice production of the pathological larynx.
Longitudinal vibrations in violin strings
Authors: Lee A. R. , Rafferty M. P.
Published: October 2005

We report the observation of longitudinal vibrations in violin strings excited by bowing. These vibrations are detected from the rocking motion of the top of the bridge in the direction longitudinal to the strings, with the aid of a photoelectric device. The frequencies of these waves are approximately three octaves above the respective fundamental frequencies of the transverse string vibrations, in line with expectation. It is found that stable oscillations are difficult to sustain in which both the transverse and longitudinal motions can coexist in comparable strength. Essentially pure longitudinal oscillations can be excited by bowing at a forward angle. These modes are difficult to identify in the normal bowing spectrum, and are substantially absent in pizzicato tones, except in the initial transients.
Variational analysis of a model for a piezoelectric polymer flexural plate hydrophone
Authors: Laura Patricio A. A. , Avalos Daniel
Published: October 2005

An approximate solution for the mathematical model of the piezoelectric polymer flexural plate hydrophone is presented. The case where sheets of polymer are attached to air-backed rectangular flexural plates is treated. This study constitutes an extension of Ricketts’ recent treatment in the sense that (a) dynamic effects are now taken into account and (b) simply supported, clamped, or elastically restrained edges are now considered.
An alternative approach for formulating the backscattering equation in Sigelmann and Reid’s method
Authors: Shung K. Kirk
Published: October 2005

The theoretical expression derived by Sigelmann and Reid for calculating backscattering coefficient from an ensemble of scatterers using a substitution technique can also be obtained directly by considering the intensity of the wave and existing scattering theorems. This approach is much simpler and clearly demonstrates the physical meaning of the experimentally determined backscattering coefficient.
Low-frequency propagation in almost fluid sediments: Role of gravity and other stresses
Authors: Tolstoy I.
Published: October 2005

Relatively unconsolidated sediments of low rigidity μ are common in oceans. Shear modes of low velocity cs(cs≲100 ms−1) then exist in sea floor sediments, as well as slow boundary waves of velocity v<cs at the water–sediment interface (Stoneley modes). Both have been observed in shallow water experiments at frequencies in the 1–5 Hz band [Rauch, Bottom-Interacti ng Acoustics (Plenum, New York, 1980)]. In poorly consolidated sediments of this kind ( μ<109 dyn cm−2) gravity and other stresses introduce small corrections to the propagation velocities. The role of gravity is of two sorts. On the one hand it introduces buoyancy forces and internal gravity waves—these are negligible for frequencies above 10−1 Hz; on the other, it introduces hydrostatic stresses which primarily affect the velocity of shear modes in the sediment—leading to corrections of order ρgz/μ (for an overburden of height z in a sediment or sediment+water column of mean density ρ). While the latter measurably affects propagation speeds in sediments, it is an isotropic effect which, in practice, finds itself lumped with other mechanisms of velocity stratification. Interesting and in principle more easily diagnosed in experiments are the effects of anisotropic stress fields—e.g., tensions and compressions associated with gravity slumping mechanisms on slopes and, for deeper and somewhat more consolidated sediments, with forces of local origin such as island loading or tectonic stresses. These can introduce measurable anisotropies into the propagation of various low-frequency bottom associated modes.
Acoustic emission measurements of a shape-memory alloy
Authors: Geng Rong S. , Britton Bryan , Stephens Raymond W. B.
Published: October 2005

A description is given of a systematic study of the acoustic emission (AE) characteristics of a specific shape-memory alloy, a copper-based Betalloy. Using a narrow-band AE measuring system, a considerable change in AE signals was observed in the different phase states of the Betalloy, the changes being particularly significant in the slope changes of the amplitude-distribution curves. By careful correlation of AE signals with the stress-induced martensitic transformation, it was found, in repetition cycles, that a reversible AE energy release accompanied the austenite–martensite transition process, which is in direct conflict with the ‘‘Kaiser effect.’’ This observation implies that caution is necessary in applying the AE technique for evaluating failure in shape-memory alloys. The values derived from the AE data for the stress required to induce martensitic transformation and for the temperature at which the transformation is initiated are in good agreement with those obtained from stress–strain measurements.
Frequency-domain investigations of cochlear stability in the presence of active elements
Authors: Koshigoe Shozo , Tubis Arnold
Published: October 2005

For a linear, time-invariant cochlear response function, the requirements of causality and stability imply the absence of poles of the spectral response function g(ω) for Im ω>0, with e−iωt as the time-dependence factor. The existence of such poles invalidate conventional Hilbert transform (dispersion) relations. The testing of these dispersion relations provides a frequency-domain check of system stability for cochlear models which contain active elements such as negative resistance. The stability of several one- and two-dimensional cochlear models with active elements is checked using these dispersion relations. A simple circuit analog of the cochlea, which contains active elements, is used to illustrate the relationship between the pole locations of g(ω) and the strength of active elements.
The ear effect as a function of age and hearing loss
Authors: Chung David Y. , Mason Keith , Gannon R. Patrick , Willson Glenn N.
Published: October 2005

Many studies have shown that the right ear statistically is slightly more sensitive than the left ear, particularly in the male adult population. In this study, we examined the lateral difference in hearing sensitivity, termed the ear effect here, in an industrial noise-exposed, nonshooting population, by sex, age, and hearing level. It was found that the male population had a larger ear effect (right ear being more sensitive) than the female population. The magnitude of the ear effect was found to be significantly related to the hearing threshold level. The ear effect was highest when the threshold was between 30- and 40-dB HL. Several possible causes for the ear effect are discussed.
Intensity discrimination with cochlear implants
Authors: Pfingst Bryan E. , Burnett Patricia A. , Sutton Dwight
Published: October 2005

Intensity difference limens were measured for various frequencies and intensities of sinusoidal and pulsatile electrical stimulation in monkeys with electrodes implanted in the scala tympani, scala vestibuli, modiolus, or middle ear. Difference limens decreased, as a function of initial stimulus intensity, from values of 1.5–3 dB near threshold to as low as 0.5 dB near the upper limit of the dynamic range. If sensation level was held constant, difference limens decreased as a function of frequency up to about 500 Hz, and then remained constant. They were similar across a variety of electrode placements and separations if differences in threshold and dynamic range were taken into account. However, difference limens measured in severely damaged ears were slightly smaller than those in moderatly damaged ears. The near miss to Weber’s law, characteristic of acoustic difference limens, was not seen with electrical stimuli. Difference limens for electrical stimuli were roughly one-half those for acoustic stimuli; thus, part of the deficit in dynamic range for electrical stimulation compared with acoustic stimulation is countered by the smaller intensity difference limens for electrical stimuli.
Laryngeal vibrations: A comparison between high-speed filming and glottographic techniques
Authors: Baer Thomas , Löfqvist Anders , McGarr Nancy S.
Published: October 2005

This study was designed to compare information on laryngeal vibrations obtained by high-speed filming, photoglottography (PGG), and electroglottography (EGG). Simultaneous glottographic signals and high-speed films were obtained from two subjects producing steady phonation. Measurements of glottal width were made at three points along the glottis in the anterior–posterior dimension and aligned with the other records. Results indicate that PGG and film measurements give essentially the same information for peak glottal opening and glottal closure. The EGG signal appears to reliably indicate vocal-fold contact. Together, PGG and EGG may provide much of the information obtained from high-speed filming as well as potentially detect horizontal phase differences during opening and closing.
Propagation of sound in highly porous open-cell elastic foams
Authors: Lambert Robert F.
Published: October 2005

This work presents both theoretical predictions and experimental measurements of attenuation and progressive phase constants of sound in open-cell, highly porous, elastic polyurethane foams. The foams are available commercially in graded pore sizes for which information about the static flow resistance, thermal time constant, volume porosity, dynamic structure factor, and speed of sound is known. The analysis is specialized to highly porous foams which can be efficient sound absorbers at audio frequencies. Negligible effect of internal wave coupling on attenuation and phase shift for the frequency range 16–6000 Hz was predicted and no experimentally significant effects were observed in the bulk samples studied. The agreement between predictions and measurements in bulk materials is excellent. The analysis is applicable to both the regular and compressed elastic open-cell foams.
Signal detection and localization using the Fourier series method (FSM) and cross-sensor data
Authors: Wilson James H.
Published: October 2005

A significant amount of acoustic information that is available in the individual hydrophone or cross-sensor measurements of line array systems may be irrevocably lost in the conventional beamforming (CBF) process. The Fourier series method (FSM) solution is presented for individual hydrophone pairs or cross-sensor measurements and compared to the CBF output for simulated deterministic acoustic fields consisting of signals embedded in directional noise background. By using the acoustic information lost in CBF, potentially significant improvements in the detection and localization of signals are realized by using FSM. For near broadside, design frequency conditions, FSM gives significant peak signal to background noise enhancement over CBF for a 64-element equally spaced line array. FSM can also resolve two signals in azimuth separated by less than a conventional beamwidth. These array performance improvements result from the accurate estimation of the high order spatial Fourier coefficients of the acoustic field. It is emphasized that FSM requires no a priori assumptions about the unknown acoustic fields required by adaptive beamforming methods and the FSM solution has no mathematical ill conditioning associated with many of the inverse beamforming methods.
On the undamped natural frequencies and mode shapes of a finite-element model of the cat eardrum
Authors: Funnell W. Robert J.
Published: October 2005

This paper presents a three-dimensional finite-element model of the cat eardrum which includes inertial effects. The model is implemented using a hierarchical modeling scheme which permits the mesh resolution to be varied. The static behavior of the model is calculated as a function of mesh resolution in order to check the validity of an earlier model. The first six undamped natural frequencies, and the corresponding modal vibration patterns, are then calculated. They are found to lie between about 1.8 and 3.2 kHz for the standard values chosen for the model parameters. The effects on the natural frequencies of varying seven parameters of the model are described.
Forward masking patterns for harmonic complex tones
Authors: Moore Brian C. J. , Glasberg Brian R.
Published: October 2005

Complex tones containing the first ten harmonics at equal amplitude, and with fundamental frequencies of 100, 200, or 400 Hz, served as maskers for brief sinusoidal signals (10-, 20-, or 40-ms duration) presented immediately following the maskers. Threshold was measured as a function of signal frequency, using an adaptive, two-alternative forced-choice procedure. The starting phase of the signal relative to the masker had no significant effect on threshold. The masking patterns showed clear peaks corresponding to the first 3 or 4 harmonics, but no peaks were visible for higher harmonics. It is concluded that the ‘‘ripple’’ in the internal spectra of the maskers amounts to 3 dB or less for harmonics above the fifth.
Reflex inhibition procedures for animal audiometry: A technique for assessing ototoxicity
Authors: Young John S. , Fechter Laurence D.
Published: October 2005

A procedure for making rapid audiometric assessments of animal subjects, based on the ability of weak stimuli to modify the strength of reflexes elicited by subsequently presented strong stimuli, is described. Pure-tone detection thresholds for rats and guinea pigs determined by this procedure are quite comparable to those determined by operant techniques, and are similarly sensitive to ototoxic insult. The procedure is also applicable to the assessment of suprathreshold sensory function, and offers advantages over commonly used procedures for assessing ototoxicity.
Detection of interaural differences of intensity in trains of high-frequency clicks as a function of interclick interval and number
Authors: Hafter E. R. , Dye R. H. , Wenzel E.
Published: October 2005

Listeners were asked to detect interaural differences of intensity in trains of 4000-Hz clicks as the interclick interval (ICI) was varied from 10 to 1 ms and the number of clicks in a train (n) was varied from 1 to 32. As has previously been shown for differences of time [Hafter and Dye, J. Acoust. Soc. Am. 73, 644–651 (1983)], plots of log interaural threshold versus log n produced slopes that decrease with ICI. These results are explained in terms of a saturation model which argues that as the click rate increases, the evoked neural activity changes from what is essentially a tonic response toward one that is more phasic.
Interaural time and amplitude discrimination in noise
Authors: Stern Richard M. , Slocum Janet E. , Phillips Michael S.
Published: October 2005

Just-noticeable differences (jnds) of both interaural time delay (ITD) and interaural intensity difference (IID) were measured for binaural tones in the presence of broadband maskers. The tones were presented at 50 dB SPL, the target frequency was 500 Hz, and the masker frequency was 100–1000 Hz, with various combinations of ITD and IID. The time and amplitude jnds exhibit similar dependencies on target-to-masker ratio and masker type. At a given target-to-masker ratio, discrimination was generally best in the presence of diotic maskers and worst in the presence of the interaurally out-of-phase maskers. Results for the other masker types examined tended to fall in between these two extremes. Many of these data trends are consistent with predictions of the lateralization model and the position-variable model based on auditory-nerve activity.