bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of environmental variables on truck noise emission and noise propagation to test microphones
Authors: Hemdal John F. , Baker Robert N. , Saha Pranab
Published: October 2005

If new vehicle noise levels cannot be predicted accurately, manufacturers must overdesign for quietness in order to be sure of meeting noise standards. To determine factors affecting sound levels, nine truck–tractor configurations were tested according to SAE Standard J366b, Exterior Sound Level for Heavy Trucks and Buses during a variety of weather conditions at three, 2-week intervals over a 6-month period. Tests made according to the standard produce reasonably repeatable results when a vehicle is tested repeatedly at the same test site (σ≤0.83 dB). There was a statistically significant but weak effect of temperature on the A-weighted sound level located 15 m from the center line of vehicle travel for three of nine truck test configurations, showing decreasing sound level with increasing temperature. The coefficient of this temperature effect averaged about −0.020 dB per degree Fahrenheit. Sound emission from truck–tractors was affected by temperature for eight of nine truck configurations. Humidity, barometric pressure, wind, and wind and temperature gradients have no consistent pattern of effect on J366b noise levels. The SAE J366b passby test sound levels cannot be practically corrected for environmental effects, and probably need not be if the requirements of the standard are carefully adhered to. Coastby and stationary tests were not notably more repeatable than the J366b passby test and one type of test cannot be used to predict the result of another.
Community response to noise: Is all noise the same?
Authors: Hall Fred L.
Published: October 2005

There have been nearly a dozen papers published in the last 5 years which compare community response to noise from several different sources such as road and rail traffic. This paper draws on those and other studies to address three questions. First, is the variation in results simply due to random sources or measurement error, such that use of an ‘‘average’’ dose-response curve is appropriate, or is there some identifiable systematic variation? Second, what characteristics of the noise or community might lead to systematic variation, if there is any? Third, under what conditions is it reasonable to use an average function, even if there are systematic variations? Both of the first two questions receive only tentative answers on the basis of available studies. Although the evidence shows different functions for different sources (e.g., rail and road noise), for different types of one source (e.g., air carrier airports and general aviation airports), and even for different studies at the same location (e.g., Heathrow), the evidence is not sufficiently strong to totally reject the idea that all of this is just random variation about an ‘‘average’’ response. As yet, there is no clear identification of what acoustical or community factors explain the differences in response, so it is sensible simply to use the type of source (i.e., road, rail, or air traffic noise) to categorize the differences. The answer to the third question, then, is that an ‘‘average’’ dose-response curve is useful in the face of limited information—that is, when we cannot specify precisely the conditions calling for different functions.
Group invariance in nonlinear motion of rods and strings
Authors: Seshadri R. , Singh M. C.
Published: October 2005

The role of group invariance in nonlinear motion of strings and rods is discussed. Problems relating to propagation of waves in rods with nonlinear elastic, elastoplastic, and viscoplastic materials are considered. A classification of linear and nonlinear equations of motion of rods and strings is given by the study of their invariance under inspectional groups, namely, dimensional, translational, and spiral groups of transformations.
Acoustic estimates of demersal fish using a dual-beam transducer in laboratory and field
Authors: Dickie L. M. , Dowd R. G. , Boudreau P. R.
Published: October 2005

The ECOLOG dual-beam echo-counting and sizing system is used in both a laboratory and a field situation with moderate densities of demersal fish. Free swimming fish in a large tank give estimates of backscattering cross section (σbs) with low variance. Application in field surveys confirms that dual-beam acoustic data provide information on both size composition and density distribution, which is different than single-beam estimates but similar to and at least as precise as that provided by trawl nets.
A theoretical study of the penetration of a water sediment interface by a parametric beam
Authors: Wingham Duncan J.
Published: October 2005

A theoretical investigation of the farfield secondary radiation present in sediment due to a parametric array incident on a water–sediment boundary is conducted, based on the assumption that the interface completely truncates the parametric array in the nearfield of its primary radiation. The field is found to be due to two apertures, one coincident with the transducer, the second with the truncation. At subcritical angles of primary beam incidence the field is similar to that produced by a conventional beam. At postcritical angles of primary beam incidence the presence of the truncation aperture results in a steeper and deeper penetration of the sediment than in the conventional case. It is concluded that the presence of virtual sources near the interface is responsible for the postcritical penetration of sediment by a parametric beam.
Nonlinear King integral for arbitrary axisymmetric sound beams at finite amplitudes. I. Asymptotic evaluation of the velocity potential
Authors: Ginsberg Jerry H.
Published: October 2005

This paper initiates the derivation of a general analytical model for nonlinear effects in sound beams driven at high source pressure levels. The excitation is generated by a planar transducer that is in harmonic motion in an arbitrary axisymmetric pattern. The analysis develops a perturbation solution of a nonlinear equation for the velocity potential. The first-order term, which is derived with the aid of a Hankel transform to represent the transverse dependence, is the King integral for a linear sound beam. Using this integral to form the source terms exciting the second-order potential leads to a dual Hankel transform. Reduction to a single integral is achieved with the aid of an asymptotic integration following Laplace’s method. The second-order term that is derived in this manner describes the tendency for the second harmonic to grow with increasing distance from the source. This result is an intermediate step in the overall development, because the integrand loses validity in the spectrum of transverse wavenumbers near the transition between evanescent and propagating wavelets, as well as for increasing distance from the transducer.
Surface fields in potential theory and acoustic scattering
Authors: Waterman P. C.
Published: October 2005

Exterior boundary-value problems are considered for the class of cylinders defined by r=r(ϑ), with 1/r expressible as a finite Fourier series, so that r(ϑ) is meromorphic in the complex ϑ plane. Upon transforming the extended boundary condition integrals into the complex plane, simple and apparently exact asymptotic behavior is determined for the surface field expansion coefficients bm; e.g., for a charged cylinder with no applied field one has bm∼2∑exp(imϑp), for m≫1, where the sum is over poles of r(ϑ) in the upper half-plane. These results are shown to have significant impact on convergence for solutions to the infinite systems of equations involved. We consider potential theory for Dirichlet and Neumann boundary conditions, and acoustic scattering in the Rayleigh limit.
Acoustic structure and propagation in highly porous, layered, fibrous materials
Authors: Lambert R. F. , Tesar J. S.
Published: October 2005

This work is concerned primarily with the acoustic structure and propagation of sound in highly porous, layered, fine fiber materials. Of particular interest is the utilization of the Kozeny number for determining the static flow resistance and the static structure factor based on flow permeability measurements. In this formulation the Kozeny number is a numerical constant independent of volume porosity at high porosities. The other essential parameters are then evaluated employing techniques developed earlier for open-cell foams. [J. Acoust. Soc. Am. 72, 879–887 (1982)]. The attenuation and progressive phase characteristics in bulk samples were measured and compared with predicted values. The agreements on the whole were very satisfactory.
Learning to detect auditory pattern components
Authors: Leek Marjorie R. , Watson Charles S.
Published: October 2005

Listeners’ abilities to learn to hear all the details of an initially unfamiliar sequence of ten 45-ms tones were studied by tracking detection thresholds for each tonal component over a prolonged period of training. After repeated listening to this sequence, the presence or absence of individual tones could be recognized, even though they were attenuated by 40–50 dB relative to the remainder of the pattern. Threshold-tracking histories suggest that listeners tend to employ two different learning strategies, one of which is considerably more efficient. Special training by reducing stimulus uncertainty and extending the duration of the target component was effective in increasing the rate of threshold improvement. Strategies acquired with the first pattern studied generalized to new sequences of tones. The possible implications of these results for the perceptual learning of speech or other auditory codes are discussed.
Predicting frequency selectivity in forward masking from simultaneous masking
Authors: Lutfi Robert A.
Published: October 2005

Measures of frequency selectivity from forward masking suggest sharper tuning than those from simultaneous masking. To account for this result, various interpretations involving additional tuning mechanisms have been proposed. In the present study, it is shown that a simple multiplicative relation between on-frequency forward and off-frequency simultaneous masking predicts this result quite well. The relation assumes that changes in masking produced by separating the masker from the signal in frequency, in time, and in both frequency and time are related to one another by Weber’s law. The accuracy of the predictions suggests that the limits of auditory frequency selectivity are already established in simultaneous masking and that special interpretations involving additional tuning mechanisms are not required to account for the difference between simultaneous and forward measures. Implications for a dB scale of masking are discussed.
The relations among critical ratios, critical bands, and intensity difference limens in man
Authors: Wier Craig C. , Schlauch Robert S. , Norton Susan J.
Published: October 2005

Band-narrowing estimates of the critical bandwidth (CB) are consistently larger than critical-ratio (CR) estimates for the same signal frequency. Bilger [in Hearing and Davis: Essays Honoring Hallowell Davis, edited by S. K. Hirsh et al. (Washington U. P., St. Louis, 1976), p. 191] proposed that this difference could be accounted for by reference to intensity-discrimination performance [CR(Hz)/CB(Hz)=ΔI/I]. To test this hypothesis, band-narrowing, critical-ratio, and intensity-discrimination data were collected for four normally hearing, well-trained listeners. Signal frequency was 2000 Hz and two noise levels were used: 20 and 50 dB N0. The relations proposed by Bilger among critical-bandwidth estimates from band-narrowing experiments, critical-ratio estimates from pure-tone detection in wideband noise, and intensity discrimination for a critical-band-wide noise in wideband noise are not supported by the results of individual listeners, or results averaged across listeners.
Rayleigh wave velocity and displacement in orthorhombic, tetragonal, hexagonal, and cubic crystals
Authors: Royer D. , Dieulesaint E.
Published: October 2005

The analysis of Rayleigh wave propagation in crystals is carried out in the cases for which, on the one hand, Christoffel equations split into two parts providing a Rayleigh wave polarized in the sagittal plane, and on the other hand, boundary conditions simplify under the conditions that some elastic constants vanish. It is shown that these requirements are satisfied by 16 configurations in crystals belonging to the orthorhombic, tetragonal, cubic, and hexagonal symmetry systems. The three particular cases solved by Stoneley [R. Stoneley, Proc. R. Soc. London, Ser. A 232, 447–458 (1955)] are included. The equations giving the velocity and the mechanical displacement are established. The influence of the anisotropy factor on the decay constant is emphasized for crystals belonging to the cubic or tetragonal systems. Curves showing the decrease of the longitudinal and transverse components of the mechanical displacement are given for YAG, Si, GaAs, TiO2, and TeO2. Oscillations and a very slow decrease versus depth of the mechanical displacement components were observed for TeO2. These are ascribed to the strong anisotropy of this crystal.
Parametric acoustic array formation in dispersive fluids
Authors: Hamilton Mark F. , Fenlon Francis H.
Published: October 2005

The effect of dispersion on parametric arrays formed by Gaussian beams is investigated via solutions of the nonlinear paraxial wave equation. Analytical solutions are obtained by employing the quasilinear approximation; the results are thus restricted to weak nonlinear interactions. Axial field curves, farfield directivity patterns, and three-dimensional field plots are presented for the difference-frequency signal. The combined effects of dispersion, dissipation, and diffraction are considered in detail. Discrepancies with previous work are discussed. Solutions for the sum-frequency and second-harmonic components are also presented. A transformation is given to make the various solutions apply to arrays formed by primaries from a circular piston.
Minimum target size in radiation force measurements
Authors: Beissner K.
Published: October 2005

The necessary target size in acoustic radiation force measurements has not, up to now, been discussed in the literature in a systematic and quantitative manner. Making use of recent progress in the theoretical treatment of the radiation force of three-dimensional sound fields, this paper gives an assessment formula involving the target’s radius and distance from the source which is valid for the field of a baffled, circular, continuously vibrating piston source.
A microscopic investigation of bubble formation nuclei
Authors: Yount D. E. , Gillary E. W. , Hoffman D. C.
Published: October 2005

Numerous experiments suggest that bubble formation in aqueous media is initiated by stable gas nuclei. Although attempts have been made both to detect and to describe these entities, their very existence is still controversial. This paper reports a detailed investigation using light and electron microscopes. The objects identified as nuclei are found in both distilled water and gelatin, and they resemble ordinary gas bubbles. Radii are on the order of 1 μm or less and can be three orders of magnitude smaller. The number density decreases exponentially with increasing radius. A gas filling is implied by the observation that nuclei expand when the pressure decreases and contract when it rises. The occurrence of nuclear clusters and of binary or osculating nuclei suggests that stabilization is achieved via surfactant films. The monolayer thickness of these films, estimated from the thicknesses of bilayer septa, is (20±7) Å. Many nuclei are embedded in reservoirs of surface-active material made visible by osmium–tetroxide staining. Electron microscope sections are hardened by infiltrating gelatin with epoxy. Reservoirs, encased in epoxy, form microbubble chambers in which the coalescence and bursting of nuclei can be studied during extended exposures to the electron beam.
Harmonic and transient scattering from time varying obstacles
Authors: Censor Dan
Published: October 2005

Transient scattering as a tool for identification of objects and their physical properties through their natural (resonance) complex frequencies is now under intensive investigation by mathematicians and engineers. This promising method of inverse scattering is pertinent to mechanical as well as electromagnetic waves. Presently this problem is considered in the context of acoustics for time varying objects, such as pulsating cylinders and spheres. Together with a choice of a reasonably simple physical model and boundary conditions, this provides a framework for discussing a few canonical problems. Mathematically, the method employed here is essentially a perturbation technique. The representation in terms of compact symbolic differential operators which are manipulated algebraically helps to avoid a lot of cumbersome detail. The results display the creation of new spectral components and the associated new poles (i.e., new resonance frequencies) due to the time variation of the objects. The additional new features, when compared to the presumably known signature of the original object at rest, facilitate the identification of the details of the motion.
Acoustic injury and the physiology of hearing
Authors: Schmiedt Richard A.
Published: October 2005

A critical bibliography of published articles concerning the effects of noise exposure on hearing has been compiled for the NIH. The review concentrated on articles published over the last 14 years; however, historical highlights of the past 50 years or so were included for continuity. This paper attempts to summarize in tutorial fashion the results of that review with regard to auditory physiology in general and explores some of the current issues with specific reference to acoustic injury. To date, most of the effort toward understanding acoustic injury has been focused on the auditory periphery; the emphasis is clear simply from the number of papers published in that area. On the other hand, the response of the central nervous system to noise exposure or to any type of damage in the periphery is essentially unknown. It would seem that it is now time to assume a more balanced approach and recognize the importance of the CNS with regard to understanding the overall consequences of acoustic injury.
Auditory filter asymmetry in the hearing impaired
Authors: Tyler Richard S. , Hall Joseph W. , Glasberg Brian R. , Moore Brian C. J. , Patterson Roy D.
Published: October 2005

Thresholds for 2-kHz sinusoidal signals were determined in the presence of a notched-noise masker, for six normal-hearing listeners and 12 listeners with cochlear hearing losses. Following Patterson and Nimmo Smith [J. Acoust. Soc. Am. 67, 229–245 (1980)], conditions were used where the notch was placed both symmetrically and asymmetrically about the signal frequency. The auditory filter shape for both the low- and high-frequency side of the filter was calculated using the rounded-exponential form of the filter. In six hearing-impaired listeners, the auditory filter shape showed a shallow low-frequency skirt indicating pronounced susceptibility to the upward spread of masking. In two hearing-impaired listeners, the filter shape showed a shallow high-frequency skirt, indicating pronounced susceptibility to the downward spread of masking. Two other listeners with mild threshold losses had steeper and more symmetric filters than normal, suggesting either a small conductive loss or an attenuation factor of sensorineural origin not associated with a degradation of frequency resolution. In the remaining two listeners, the auditory filter had too little selectivity for its shape to be reliably determined.
The vertebrate ear as an exquisite seismic sensor
Authors: Narins Peter M. , Lewis Edwin R.
Published: October 2005

The neotropical frog Leptodactylus albilabris exhibits the greatest sensitivity to substrate-borne vibrations (seismic stimuli) reported to date for any terrestrial animal. Nerve fibers from the source of this extraordinary sensitivity in the ear show clear stimulus-evoked modulations of their resting discharge rates in response to sinusoidal seismic stimuli with peak accelerations less than 0.001 cm/s2 (10−6 g). Evidence indicates that its source is the saccule, an organ of hearing in fish and of balance in man. We report that single vibration-sensitive fibers in the white-lipped frog saturate at (whole animal) displacements of 10 Å peak to peak [Fig. 1(b)]. Assuming a conservative 20-dB dynamic range for these fibers, the in vivo frog saccule and the mammalian cochlea exhibit roughly equal sensitivities to displacement.
Group delay measurement from spiral ganglion cells in the basal turn of the guinea pig cochlea
Authors: Gummer Anthony W. , Johnstone Brian M.
Published: October 2005

Measurements of group delay were made extracellularly from spiral ganglion cells in the 3.7 to 5.0-mm region of the guinea pig cochlea, using sinusoidally amplitude modulated tones with constant modulating frequency (100 Hz) and depth of modulation (0.19). Threshold cochlear tuning was accompanied by frequency-dependent group delays. The group delay on the low-frequency tail was independent of carrier frequency; the interunit variation was 0.28–1.28 ms. The difference in group delay between CF and the low-frequency tail decreased as the CF threshold increased (−0.09±0.02 ms per 10 dB, beginning at 0.62±0.07 ms at 0 dB SPL). The group delay decreased above CF; at the units’ maximum frequency it was less than the low-frequency tail value, and was sometimes negative. Following arterial injections of furosemide the CF threshold increased and the group delay peak decreased; the low-frequency tail was unaffected. The group delay decreased with increasing intensity; the reduction near and above CF was not only larger than that on the low-frequency tail, but also the change at 5–10 dB above threshold was far greater than expected from the Q10 dB of the suprathreshold iso-rate tuning curves. A minimum-phase analysis suggested that the group delay response above CF, together with its nonlinear behavior, can be accounted for by a high-frequency, level-independent, amplitude plateau, in combination with the single unit, amplitude nonlinearity which is known to exist above CF.
Mixed-mode acoustical glory scattering from a large elastic sphere: Model and experimental verification
Authors: Williams Kevin L. , Marston Philip L.
Published: October 2005

Scattering from large elastic or fluid spheres is enhanced along the backward axis due to a weak focusing. The effect of diffraction on this axial focusing was shown [J. Acoust. Soc. Am. 73, 1464–1475 (1983)] to remove an unphysical divergence of scattered pressure predicted by elementary ray acoustics. Our previous model of this ‘‘acoustic glory’’ of elastic spheres was complete only for transmitted waves within the sphere which were either all longitudinal (L) or all shear (S). These contributions were separated by measuring the backscattering of short tone bursts from a glass sphere in water having ka≊457 [J. Acoust. Soc. Am. 74, 605–618 (1983)]. In the present paper, we complete the theory for the case of mixed-mode echoes in which there is at least one L to S or S to L mode conversion due to reflection. A novel calculation shows that the focal parameters are independent of permutations of the mode sequence; however, the contributions to the scattering depend on sequence. The model is tested by measuring the amplitudes of the two distinct mixed-mode echoes having the large signal-to-noise ratios for the aforementioned sphere and ka. Measured amplitudes are within 4% of predictions. The Appendix models the plane-surface reflection and transmission phase and magnitude factors used in the theory.
Calculation of the loss tangent for viscoelastic materials using the triple-bar composite resonance technique
Authors: Ferguson Brian G.
Published: October 2005

The triple-bar composite resonance technique involves the forced resonance of a sample that has been cemented between two matched aluminum buffer bars. This technique enables the dynamic mechanical properties of the sample to be studied at frequencies well below the fundamental longitudinal resonant frequency of the sample alone. The viscoelastic properties of the sample determine the magnitude of the loss tangent, i.e., the ratio of the viscous to the elastic component of the sample’s complex modulus. Using a ‘‘perturbation’’ approach in which the length of the sample is small with respect to the overall length of the composite, Anderson and Harris [J. Phys. E 6, 746–748 (1973)] derived a formula that enabled the loss tangent of the sample to be calculated from triple-bar composite resonace measurements. However, they failed to satisfy the boundary conditions at the sample/buffer bar junction and made approximations that are not valid in practice. Using an alternate approach we derive a formula for calculating the loss tangent that has general application; we then transform this formula so that a direct comparison can be made with the Anderson–Harris formula.
The rational approximation to the acoustic wave equation with bottom interaction
Authors: Greene Robert R.
Published: October 2005

The rational-linear approximation to the wave equation is a full-wave approach to modeling range-dependent ocean acoustic propagation with bottom interaction. It is a one-way wave equation which gives an accurate treatment of high-angle propagation to angles of about 40° with respect to the horizontal. Reflection from sound speed and density discontinuities is treated using the natural wave equation matching conditions. Bathymetry is allowed to vary in range. A tridiagonal implicit finite-difference solution of this equation has been implemented. It has several advantages over the tridiagonal Crank–Nicholson solution of the parabolic equation. It more accurately models high angles of propagation, treats attenuation as a function of path length rather than range, and models range-dependent bathymetry in a way that suits the form of the one-way wave equation. The numerical methods are fourth-order accurate in depth. The resulting implicit range step is still in the simple tridiagonal form.
Perception of temporal differences in speech by ‘‘normal-hearing’’ adults: Effects of age and intensity
Authors: Price P. J. , Simon H. J.
Published: October 2005

Many older people have greater difficulty processing speech at suprathreshold levels than can be explained by standard audiometric configurations. Some of the difficulty may involve the processing of temporal information. Temporal information can signal linguistic distinctions. The voicing distinction, for example, that separates pairs of words such as ‘‘rapid’’ and ‘‘rabid’’ can be signaled by temporal information: longer first vowel and shorter closure characterize ‘‘rabid’’; shorter vowel and longer closure characterize ‘‘rapid.’’ In this study, naturally produced tokens of ‘‘rabid’’ were low-pass filtered at 3500 Hz and edited to create vowel and (silent) closure duration continua. Pure-tone audiograms and speech recognition scores were used to select the ten best-hearing subjects among 50 volunteers over age 55. Randomizations of the stimuli were presented for labeling at intensity levels of 60 and 80 dB HL to this group and to ten normal-hearing volunteers under age 25. Results showed highly significant interactions of age with the temporal factors and with intensity: the older subjects required longer silence durations before reporting ‘‘rapid,’’ especially for the shorter vowel durations and for the higher intensity level. These data suggest that age may affect the relative salience of different acoustic cues in speech perception, and that age-related hearing loss may involve deficits in the processing of temporal information, deficits that are not measured by standard audiometry.
Detection of interaural phase shift between a subaudible and an audible tone
Authors: Ayres Thomas J. , Clack T. Dean
Published: October 2005

Can a shift in interaural phase between a subthreshold signal and an audible contralateral probe tone affect perception of the probe? To obtain an answer, an 800-Hz tone was presented to both ears. The tone was presented continuously to one ear (−25 to + 10 dB SL) and in a sequence of four bursts per trial to the other ear (+10 dB SL). Interaural phase was reversed for either the second or the fourth burst in a 2 AFC task. Interaural phase-shift detection threshold (65% correct) varied with the intensity of the continuous signal; across subjects, this threshold varied from −21 to +1 dB SL. When a 300-or 500-Hz masking tone was added to the ear with the continuous signal, phase-shift detection accuracy depended primarily upon the sensation level of the signal rather than its sound pressure level. These findings demonstrate temporal encoding at signal levels well below hearing threshold.
Interaural octave phase-shift detection and aural harmonic distortion
Authors: Ayres Thomas J. , Clack T. Dean
Published: October 2005

A continuous 400-Hz tone (60–75 dB SPL) and 250-msec bursts of an 800-Hz tone (10 dB SL) were delivered dichotically. Four out of nine listeners were able to detect a 180° interaural phase shift. When a subaudible continuous 800-Hz tone was added to the ear with the 400-Hz tone, interaural phase-shift detection depended on the phase relation of the added tone to the 400-Hz tone. These results are shown to be consistent with the hypothesis of aural harmonic distortion.
Dynamic range and asymmetry of the auditory filter
Authors: Glasberg Brian R. , Moore Brian C. J. , Patterson Roy D. , Nimmo-Smith Ian
Published: October 2005

This experiment was designed to measure the shape and asymmetry of the auditory filter over a wider dynamic range than has been measured previously. Thresholds were measured for 2-kHz sinusoidal signals in the presence of two 800-Hz-wide noise bands, one above and one below the signal frequency. The spectrum level of the noise was 45 dB (re: 20 μPa), and the noise bands were placed both symmetrically and asymmetrically about the signal frequency. The deviation of the signal frequency from the nearer edge of each noise band varied from 0 to 0.8 times the signal frequency. Each ear of six subjects was tested, and the subjects’ ages ranged from 22 to 74 years. The auditory filters derived from the data were somewhat asymmetric, with steeper slopes on the high-frequency side; the degree of asymmetry varied across subjects. The asymmetry could be characterized as a uniform stretching of the (linear) frequency scale on one side of the filter. The dynamic range of the auditory filter exceeded 60 dB in the younger listeners, but the dynamic range and sharpness of the filter tended to decrease with increasing age.
Aspirin abolishes spontaneous oto-acoustic emissions
Authors: McFadden Dennis , Plattsmier H. S.
Published: October 2005

Spontaneous oto-acoustic emissions (OAEs) were measured prior to, during, and following administration of aspirin. The dose schedule was three 325-mg tablets every 6 h for a total of 16 doses (3.75 days). In every subject studied, all spontaneous OAEs gradually diminished and then disappeared during the drug regimen. Emissions that were initially small disappeared within 14–20 h of beginning the drug regimen (3–4 doses), while initially large emissions took 40–70 h (7–12 doses) to disappear completely. In contrast, the initial size of an emission appeared unrelated to the time required for it to recover to full strength once drug administration ceased. The recovery process was highly idiosyncratic, with the emissions of some subjects returning to full strength within 24 h, while for other subjects, full recovery required several days. In two subjects having multiple emissions in the same ear, the relative sizes of the different emissions often changed greatly during the disappearance and recovery phases. When small frequency shifts appeared for these subjects, they appeared—and were in the same direction—for each of the multiple emissions. In a related experiment, the spontaneous emission was unchanged in one subject who took a drug that inhibits the intracellular entry of calcium ions (verapamil).
On the influence of unequal sub-array spacing configurations on source localization and the similarity with multipath ranging
Authors: Hassab J. C.
Published: October 2005

The influence of varied linear array configurations on passive ranging is determined when imperfect measurements of the time delays between the sub-arrays are available. The exact bias and farfield bias and variance relations on the source range estimates are derived as a function on unequal sub-array separation. The results are contrasted with those found in the literature on equally separated sub-arrays to highlight the sensitivity and resulting degradation in performance. It is found, for instance, that the range bias more than doubles when the internal sub-array is moved from the midpoint to the quarter-point from either end sub-arrays and more than quadruples when it is moved from the quarter-point to the one-eighth-point. Since the range variance is related to the true range and to the incurred bias, it degrades much more rapidly. The commonality between array ranging and multipath ranging is also developed for various channels of interests. The optimal placement for the receiving sensor in multipath channels is derived. Though it turns out that the same relations apply to both ranging problems, the existence of a multipath channel will support a longer ranging capability with the baseline now effectively determined by such large parameters as water depth, receiver, and source depths. Such results enable the merger of multisensor data according to their individual merits and the provision for a credence estimate of the source range choice.
Measurement of attenuation and dispersion using an ultrasonic spectroscopy technique
Authors: Kline Ronald A.
Published: October 2005

An ultrasonic spectroscopy technique for the simultaneous, wideband measurement of attenuation and dispersion in solids is described. The technique is based on Fourier analysis of digitized ultrasonic waveforms. Results are compared with discrete frequency measurements of these properties with good agreement observed.
A mechanism for the generation of cavitation maxima by pulsed ultrasound
Authors: Flynn H. G. , Church Charles C.
Published: October 2005

A train of 1-MHz pulses can generate maxima of cavitation activity [V. Ciaravino, H. G. Flynn, and M. W. Miller, Ultrasound Med. Biol. 7, 159–166 (1981)] at pulse lengths of 6 and 60 ms and at pressure amplitudes, PA, between 5.4 and 9.4 bars (or intensities between 10 and 30 W/cm2). Generation of maxima at PA between these limits on pressure amplitude implies that the increase in cavitation activity originates from gas nuclei with radii lying in a critical size range centered at about 0.08 μm. The mechanism proposed for this phenomenon suggests that nuclei in this critical range are unstabilized nuclei generated in one pulse and surviving to the next with an appreciable fraction of the survivors lying in the critical range. Transient cavities that grow from such small nuclei are shown to behave as isolated mechanical systems that on reaching maximum size collapse as imploding spheres. The maximum pressures reached in such imploding cavities would then approximate those calculated for the spherical collapse of cavities. The occurrence of the observed maxima is ascribed to the spherical collapse of transient cavities.
Using ultrasonic S
H waves to estimate the quality of adhesive bonds: A preliminary study
Authors: Yew Ching H.
Published: October 2005

A preliminary study using horizontal shear waves (SH waves) in a bonded plate to estimate the bonding strength of adhesive is presented in this paper. The essence of the method is based on the observation that the characteristics of SH waves in a bonded plate are dependent upon the bonding stiffness of the adhesive; thus, an estimation of the adhering strength can be made by observing the behavior change of these wave motions. An adhesive can, in general, by modeled as a viscoelastic material. The mechanical properties determined by subjecting the material to a pure shear deformation are therefore the most pertinent properties that characterize the cohesive strength of the adhesive. An SH wave produces a pure shear deformation in the adhesive layer in a direct manner. In this study, a long aluminum strip is bonded to the surface of a large aluminum block. An SH wave is imparted to one end of the strip. The shear wave motions in the strip are periodically monitored at sequential times as the adhesive cures. The results indicate that (1) there are two measurable modes of SH waves in the strip during the early stage of adhesive curing and (2) the amplitude of the second mode SH wave decreases as the adhesive cures, finally disappearing after the adhesive curing process is completed. This study has successfully shown that the bonding stiffness of adhesives can be estimated by observing the amplitude change of the second mode SH-wave motions in the adhered plate.
Variation of specific heats and of specific heat ratio in air with humidity
Authors: Wong George S. K. , Embleton Tony F. W.
Published: October 2005

This paper described a theoretical investigation into the variations of the specific heats of air Cp and Cv, and their ratio γ, with relative humidity. The investigation is based on published equations for Cp, and the predicted values are derived from theoretical and experimental thermodynamic data on the constituents of humid air. For acoustical applications, such as the determination of the variation of the speed of sound in humid air, the perturbation of the term γ/M̄ with relative humidity is also presented.
Performance on frequency-discrimination tasks by musicians and nonmusicians
Authors: Spiegel Murray F. , Watson Charles S.
Published: October 2005

Auditory discrimination abilities of professional musicians were compared with those of nonmusicians. The stimuli for the frequency-discrimination tasks were 300-msec sinusoidal tones, 300-msec square waves, and tone patterns consisting of ten 40-msec tones played sequentially. The musicians’ difference thresholds for single tones were between Δf /f=0.001 and 0.0045. One-half of the nonmusicians attained thresholds almost as low; the rest attained larger thresholds, up to Δf /f=0.017. The results for the pattern stimuli show a clearer separation between the nonmusicians and musicians, whose median difference thresholds were about three times smaller. However, nonmusician listeners who had previously trained with patterns not in the test set had different thresholds, substantially smaller than those obtained by the musicians. The appropriateness of preferential recruitment of musicians for psychoacoustic research is discussed. The responses to a musical background survey and correlations between the survey items and discrimination performance are contained in a supplement to this paper [PAPS JASMA 76, xxx-xx].
A new approach to transducer design applied to a foil electret acoustic antenna
Authors: Busch-Vishniac Ilene J. , West James E. , Wallace R. L.
Published: October 2005

A new approach to transducer design is introduced in which a transducer is viewed as a continuum of infinitesimal, locally reacting elements. The transducer response is the coherent sum of the responses of the infinitesimal elements. Hence variations in transducer response characteristics will be produced by variations in the relative contribution of each element. It is thus possible to produce designed transducer characteristics through selection of a suitable local sensitivity shading function. This new approach is used to design a foil electret acoustic antenna which achieves with a single transducer direction characteristics similar to these of a linear microphone array. Five methods for accomplishing sensitivity variation in the electret microphone have been identified: variation of active width, variation of charge density, variation of actual airgap, variation of foil thickness, and variation of effective airgap. It is shown that compared to a linear microphone array, the single transducer acoustic antenna offers advantages of lower sensitivity to small construction errors, directional behavior over a wider frequency range, easier construction, and potentially higher signal to noise ratio.
The effect of correcting fundamental frequency on the intelligibility of deaf speech and its interaction with temporal aspects
Authors: Maassen Ben , Povel Dirk-Jan
Published: October 2005

This study investigates the role of intonation for the intelligibility of deaf speech. The intonation contours of Dutch sentences spoken by deaf children were manipulated using digital signal processing techniques, including LPC analysis. Sentence intonation was corrected by replacing the original F0 contour of the deaf utterance with an artificial contour derived from a formalized intonation grammar. Three types of intonation corrections were produced, differing with respect to the underlying accent structure and the type of F0 movements used. The overall results show that intonation correction yields a small but significant improvement in intelligibility of 7% (from 20% to 27% words correctly identified). The largest gain is obtained after removal of over-accentuations. To evaluate the interaction with temporal aspects, intonation corrections were also implemented on temporally corrected sentences. Total growth in intelligibility due to these combined corrections amounts to 13%. Thus it is concluded that no dramatic gain in intelligibility may be expected if speech pathologists succeed in teaching their deaf pupils to have better control over the suprasegmental aspects of their speech.
NoSo and NoSπ thresholds as a function of masker level for narrow-band and wideband masking noise
Authors: Hall Joseph W. , Harvey Antony D. G.
Published: October 2005

NoSo and NoSπ thresholds for a 500-Hz signal were determined as a function of masker level for masking noises having 600- and 50-Hz bandwidths centered on 500 Hz. Noise levels of 0, 10, 20, 30, 40, 50, and 60 dB/Hz were used for the 600-Hz bandwidth, and noise levels of 0, 10, 20, 30, 40, 50, 60, and 70 dB/Hz were used for the 50-Hz bandwidth. The So thresholds increased as a function of increasing noise level with a slope close to 1.0, for both the 50- and 600-Hz masker bandwidths. For the 600-Hz-wide masker, the Sπ thresholds increased with a slope less than 1.0 for masker levels from 0 dB/Hz to approximately 20 dB/Hz, but increased with a slope close to 1.0 for masker levels above approximately 20 dB/Hz. For the 50-Hz-wide masker, the Sπ thresholds increased with a slope less than 1.0 for masker levels from 0 dB/Hz to approximately 40 dB/Hz, but increased with a slope close to 1.0 for masker levels above approximately 40 dB/Hz. The results are discussed in terms of different binaural processes involving interaction between monaural critical bands centered on the signal frequency, and interaction involving monaural critical bands outside the monaural critical band centered on the signal. It was suggested that the narrow-band noise results are probably more appropriate than the wideband noise results when considering binaural interaction involving monaural critical bands centered on the signal frequency.
A performance comparison of four noise background normalization schemes proposed for signal detection systems
Authors: Struzinski William A. , Lowe Edward D.
Published: October 2005

This article presents the results of a simulation experiment comparing the behavior of four noise background normalization schemes. The four schemes are the two-pass mean, the split three-pass mean, the split average exclude average, and the order truncate average normalizers.
Free vibration of a cantilever folded plate
Authors: Irie Toshihiro , Yamada Gen , Kobayashi Yukinori
Published: October 2005

An analysis is presented for the free vibration of a cantilever folded plate. For this purpose, the deflection displacements of the plate are written in a series of the products of the eigenfunctions of a cantilever beam and a cranked free–free beam parallel to the clamped edge of the plate. The kinetic and strain energies of the plate are evaluated analytically, and the frequency equations are derived by the Ritz method. The method is applied to cantilever folded plates with and without structural symmetry, and the natural frequencies and the mode shapes of vibration are calculated numerically giving the results.
Asymptotic analysis of a viscous cochlear model
Authors: Keller Joseph B. , Neu John C.
Published: October 2005

A model of cochlear macromechanics, involving a viscous cochlear fluid, is analyzed asymptotically for slowly varying membranes. The results exhibit the effect of viscosity on the amplitude, wavelength, and damping rate, and confirm the conclusion that viscosity is not important. However the method can be used on other models, such as those of cochlear micromechanics, where viscosity is more important.
Cochlear nucleus, inferior colliculus, and medial geniculate responses during the behavioral detection of threshold-level auditory stimuli in the rabbit
Authors: Kettner Ronald E. , Thompson Richard F.
Published: October 2005

Rabbits were conditioned to respond behaviorally to auditory stimuli by pairing a white-noise conditioned stimulus (CS) with a corneal airpuff unconditioned stimulus (US). The conditioned response (CR) was movement of the nictitating membrane (NM). After the subjects were responding at better than the 90% correct level, the intensity of the auditory stimulus was reduced to behavioral threshold using a staircase procedure. Simultaneous measurements of neural unit activity and behavioral NM responses were then made in rabbits performing at behavioral threshold. After the experiment was completed neural unit responses during behavioral detection trials were compared to neural responses made during nondetection trials. Neural unit responses to a constant intensity, white-noise stimulus at behavioral threshold were well defined and essentially identical on behavioral detection and nondetection trials in the ventral cochlear nucleus, the ventrolateral division of the central nucleus of the inferior colliculus, and the ventral division of the medial geniculate body. This suggests that an auditory stimulus can be neuronally ‘‘detected’’ without being behaviorally detected, and that the neural ‘‘decision’’ to respond behaviorally is not made in these nuclei. Responses recorded from the dorsomedial division of the central nucleus of the inferior colliculus, the pericentral nucleus of the inferior colliculus, and less commonly in the medial division of the medial geniculate body were also clearly present and nearly identical during the onset of the auditory stimulus, but were sometimes consistently different for detection and nondetection conditions during the latter part of the auditory stimulus. These brain regions appear to receive both auditory and nonauditory inputs, and show responses which are more highly correlated with detection behavior.
A power-law transformation predicting masking by sounds with complex spectra
Authors: Lutfi Robert A.
Published: October 2005

In a previous paper [R. Lutfi, J. Acoust. Soc. Am. 73, 262–267 (1983)], the following rule was proposed for predicting masking by pairs of simultaneous maskers; Xab =[XPa+XPb]1/P, where in units of power, Xa and Xb are the individual masking effects of the maskers, Xab is the combined effect, and 0.20≤p≤0.33. In this paper, the rule is used to predict the results of studies in the literature that have measured masking by sounds with various other complex spectra. In most of these studies, the individual maskers comprising the complex have nominally nonoverlapping power spectra. A single value of p=0.33 yields predictions in good agreement with the data of these studies. For a study in which the component maskers overlap more appreciably, a larger value of p=0.50 produces equally accurate predictions. The rule also predicts some general features of the results of studies in which the individual effects of the maskers in the complex are not known but can be estimated. It is suggested that the general applicability of the rule reflects a conjoint analysis by the auditory system of two or more waveform statistics.