bluuebunny/crossref_metadata_2025 huggingface dataset:
The role of helicopter noise-induced vibration and rattle in human response
Authors: Schomer Paul D. , Neathammer Robert D.
Published: October 2005

Our understanding of community reaction to helicopter noise is incomplete and inadequate. While A-weighting appears to work outdoors and at modest noise levels, and the community response in terms of percentage of population highly annoyed can be correlated with respect to the day/night average sound level (DNL) descriptor, questions remain as to the role of perceived building vibrations and rattle in human response to helicopter noise. Does hearing windows, ceiling tiles, or objects in the room rattle or does the general perception of building vibration increase the public’s adverse response to helicopter noise? To answer these questions, this study examined the role of vibration and rattle in human response to helicopter noise. Results showed that the A-frequency-weighting is generally adequate to assess community response to helicopter noise when no vibration or rattle is induced by the noise. When rattle or vibrations are induced by the helicopter noise, however, A-weighting does not assess the community response adequately. In this study, slant distance (distance of closest approach between the helicopter and the location on the ground) offers the best correlation with high levels of rattle. High levels of rattle usually would not be induced for slant distances in excess of 1000 ft, but high levels of rattle would nearly always be produced for slant distances shorter than 500 ft. The result suggests a decibel offset on the order of 10 dB or more is required to assess helicopter noise properly when little vibration or rattle is produced. When no rattles are induced by the noise, there is no offset. No housing or noise-sensitive land uses should be located in zones where high levels of vibration or rattle are induced by helicopter noise; the offset is at least on the order of 20 dB. This high vibration and rattle zone potentially can be delineated by helicopter type and slant distance. For the Army Huey aircraft in level flyover, this zone boundary is at a slant distance between 500 and 1000 ft. The slant distance zone boundary is expected to differ with type of aircraft and operation.
An extrapolation procedure for transient reflection measurements made on thick acoustical panels composed of lossy, dispersive materials
Authors: Piquette Jean C.
Published: October 2005

The underwater acoustic behavior of an elastomeric coating material is frequently evaluated by performing a reflection experiment on a sample, e.g., a rectangular panel, of the coating material. Extrapolation of the transient portion of the reflected wave in such measurements is required when steady-state conditions do not occur prior to interference from extraneous reflections. This article describes a technique for the extrapolation of measurements made on thick acoustical panels (the interrogating wave is assumed to be normally incident). The technique involves fitting a multiple-layer model to the experimental data via a least-squares process. The model assumes homogeneous and isotropic panel layers. The technique can perform the extrapolation using a much shorter leading portion of the reflected wave than is possible with other existing techniques. Experiments on three sample panels were conducted to investigate the usefulness of the technique. The first panel consists of three simple homogeneous layers. The second and third samples are fabricated from viscoelastic layers including macrovoids. The experiment covered the frequency range 2–20 kHz. The measurements on the simple three-layer panel are in reasonably good agreement with theoretical calculations based on the known acoustical properties of the layers. The acoustical properties of the more complicated panels are unknown. However, the extrapolations based on the measurements obtained from these panels appear to have reasonable behavior.
Asymptotic modal analysis for dynamic stresses of a plate
Authors: Kubota Yuji , Dowell Earl H.
Published: October 2005

Asymptotic modal analysis has been applied to stress analysis of a uniform thin rectangular plate under point forces that are bandlimited white noise. The asymptotic limits of the temporal averages of the bending stresses and the distortion energy have been determined. It is shown that the dependence on the center frequency of the asymptotic limits of stresses is different from that of deflection. The concentration factors with respect to various locations on the plate are discussed.
Three-dimensional acoustic analysis of a circular expansion chamber with side inlet and end outlet
Authors: Yi Sung-Il , Lee Byung-Ho
Published: October 2005

Noise attenuation characteristics of a simple expansion chamber with a side inlet and an end outlet are studied. A theoretical method is derived to investigate the influences caused by higher-order modes, using a three-dimensional analysis in which the chamber is considered as a piston-driven circular cylinder. Also, quantitative estimation for the transmission loss can be performed, using the derived four-pole parameters. Accordingly, the characteristics of the chamber, as a result of the interactions between the plane wave and the transverse waves, can be investigated easily with respect to the relative locations of the inlet/outlet and chamber length. Experiments are performed for the verification of the theory. In the case of the chamber with a concentric end outlet, plane-wave theory agrees with the theoretical and experimental results below the rather high frequency range, but not for the case of the chamber with an offset end outlet. Experimental results are in good agreement with the theoretical results obtained.
An implicit least-square method for the inverse problem of acoustic radiation
Authors: Chao Yei-Chin
Published: October 2005

A simple and natural method, called the implicit least-square method, is developed to solve the inverse problem, especially for first-kind Fredholm integral equations of acoustic radiation. Unlike most previous methods, there are no artificial constraints or parameters to be specified. This method is proven to be equivalent to the pseudoinverse method and is tested in three examples: (i) inversion of Poisson’s formula of harmonic continuation, (ii) inversion of the free-space turbulent flame noise radiation for the heat release rate source, and (iii) inversion of the ducted combustion system noise radiation for the heat release rate source. Comparisons performed using the results of the present prediction, the exact solution, and the experimental data in these examples are satisfactory.
Surface admittance of highly porous foams with finite stiffness
Authors: Lambert Robert F.
Published: October 2005

This work responds to some comments on the surface admittance of highly porous foams with finite stiffness by Allard et al. [J. Acoust. Soc. Am. 79, 1734–1740 (1986)]. The analysis, based on a more exact theory of sound propagation in flexible foams with finite stiffness, shows that stiffness effects should not be ignored even at frequencies well above the so-called decoupling frequency, and also that they can contribute significantly to the admittance (conductance and susceptance) at lower frequencies. The conductance is increased somewhat while the susceptance is decreased at low frequencies. The predictions are compared with experimental data available at high frequencies on an open-cell, fully reticulated foam with finite stiffness, and the agreement is much improved.
Absorption of sound in water fog composed of submicron droplets
Authors: Wei Rong-jue , Tian Yu-ren , Lu Qiu-jiang
Published: October 2005

A previous review [J. Acoust. Soc. Am. 70, 1213–1219 (1981)] emphasized sound absorption in water fog of droplets within sizes near 10 μ. This supplemental article presents results for the core where droplet size is much smaller, ≂0.01 μ. Theoretical formulation for these small droplets is shown to be basically the same as for the larger droplets. The attenuation coefficient due to mass transfer, which some authors claimed to be two (or three) orders of magnitude larger for small drops than for large ones, is accompanied by an increase in the frequency of maximum absorption by the same orders of magnitude. A correction factor is also introduced for the relaxation times from the viewpoint of modern fog kinetics. The result predicts a counter effect or a drastic decrease in the absorption abnormality due to submicron droplets, but the effect is less, the larger the droplet, which, therefore, may lead to a theoretical generalization of the problem applicable to droplets of all sizes.
Factorization and path integration of the Helmholtz equation: Numerical algorithms
Authors: Fishman Louis , McCoy John J. , Wales Stephen C.
Published: October 2005

The propagator for the reduced scalar Helmholtz equation plays a significant role in both analytical and computational studies of acoustic direct wave propagation. Path (functional) integrals are taken to provide the principal representation of the propagator and are computed directly. The path integral is the primary tool in extending the classical Fourier methods, so appropriate for wave propagation in homogeneous media, to inhomogeneous media. For transversely inhomogeneous environments, the n-dimensional Helmholtz equation can be exactly factored into separate forward and backward one-way wave equations. A parabolic-based (one-way) phase space path integral construction provides the generalization of the Tappert/Hardin split-step FFT algorithm to the full one-way (factored Helmholtz) wave equation. These extended marching algorithms can readily accommodate density profiles and range updating, and further, in conjunction with imbedding methods, provide the basis for incorporating backscatter effects. In a complementary manner, for general range-dependent environments, elliptic-based (two-way) path integral constructions lead to an approximate representation of the propagator (Feynman/Garrod) and a natural statistical (Monte Carlo) means of evaluation. Taken together, the path integrals provide the basis for a global analysis in addition to providing a unifying framework for dynamical approximations, resolution of the square root operator, and the concept of an underlying stochastic process. The one-way marching algorithms are applied to ocean acoustic environments, seismological environments, and extreme model environments designed to establish their range of validity and manner of breakdown.
Scintillations of partially coherent signals in nonscattering channels
Authors: Frankenthal Shimshon
Published: October 2005

The quadratic approximation is used to derive a procedure for computing the mean-square intensity in a channel excited by a partially coherent source, using the characteristics (rays of geometrical acoustics) of the four-point coherence equation, and their properties. The procedure is employed to obtain exactly the scintillation field of a partially coherent Gaussian beam emerging from a weak phase screen into a quadratic channel. A simple approximate formula for the mean-square intensity in the farfield of a localized source is derived and tested: It is found to closely reproduce the aforementioned exact result for a quadratic channel, except for the immediate vicinity of focal planes. Various modes of application of the approximate formula are discussed.
Complex study of critical n-amyl alcohol–nitromethane mixture by acoustic-optical methods
Authors: L/abowski Mikol/aj , Hornowski Tomasz
Published: October 2005

Complex results, obtained in the investigation of the critical mixture n-amyl alcohol–nitromethane by acoustic spectroscopy and light scattering are reported. The experimental results are applied to evaluate the lifetimes, concentration fluctuation correlation length, mean concentration wavelength, and intermolecular interaction length. Acoustic measurements were performed for various concentrations, two temperatures, and a wide range of frequencies. The quantity α/ f2 was found to be dependent on the frequency, temperature, and concentration, and to exhibit a maximum for the critical composition of the mixture; the maximum decreases with increasing frequency of the acoustic wave. Dispersion of α/ f2 is not accompanied by measurable changes in the propagation velocity of the wave as a function of frequency. The theories of Chaban and Fixman are used to determine the intermolecular interaction length and concentration fluctuation correlation length. They were found to be in satisfactory agreement with the respective values obtained from our light scattering measurements.
Focal shift of convergent ultrasonic beams reflected from a liquid–solid interface
Authors: Nagy Peter B. , Cho Kangra , Adler Laszlo , Chimenti D. E.
Published: October 2005

It is shown by schlieren photography that a convergent acoustic beam reflected from a liquid–solid interface can exhibit a focal shift in the axial direction when the angle of incidence deviates slightly from the critical angle. The results confirm the recent predictions of Bertoni et al. [Trait. Sign. 2, 201–205 (1985)] about this interesting detail of the general Rayleigh angle phenomenon.
The effect of snow on vehicle-generated seismic signatures
Authors: Albert Donald G.
Published: October 2005

Vehicle-generated seismograms recorded under summer and winter conditions at Fort Devens, MA are analyzed and compared. The appearance and frequency content of the recorded ground motion change dramatically from summer to winter when a 0.7-m-thick snow layer is present. The snow layer causes a 10-dB reduction in the amplitude of the acoustically coupled signal relative to the signal generated where the vehicle contacted the ground. A magnitude squared coherence analysis and a simple Wiener prediction model of the acoustic transmission near the observation point reinforce this conclusion.
The use of meteorological profiles to predict the peak sound-pressure level at distance from small explosions
Authors: Kerry Geoff , Saunders David J. , Sills Alan G.
Published: October 2005

The peak sound levels from 117 charges of gelignite, with weights ranging from 1 to 17 kg, were monitored over a 4-day period at 17 locations, whose distances from the source varied from 100 m to over 10 km. A total of 1639 measurements was recorded. Detailed meteorological data were collected using ground-level monitors and radar-tracked radio sonde ascents enabling wind velocity and temperature profiles to be established from the surface to a height of 3000 m, for each half-hour period throughout the trial. The data set has been used to test and modify an empirical equation relating the peak sound level to the density of sound rays returning to the surface.
Adiabatic transforms for spectral analysis and synthesis of weakly range-dependent shallow ocean Green’s functions
Authors: Lu I. T. , Felsen L. B.
Published: October 2005

Range-independent (separable) ocean waveguide Green’s functions can be synthesized by applying exact transform theorems to the range variables and thereby reducing the two- or three-dimensional problem to a one-dimensional problem for the depth-dependent portion. The resulting spectral integral representations are useful for determining alternative forms of the total direct Green’s function and also, by inversion applied to given data, for recovery of spectral plane-wave reflection coefficients that contain information about the bottom structure [G. V. Frisk, J. F. Lynch, and J. A. Doutt, in Ocean Seismo-Acoustics, edited by T. Akal and J. M. Berkson (Plenum, New York, 1986)]. Exact transform theory fails in the presence of range dependence (nonseparability). When such dependence is weak, adiabatic spectral invariants deduced from the properties of the adiabatic modes may be invoked to adapt the spectral integrals approximately to these generalized conditions [A. Kamel and L. B. Felsen, J. Acoust. Soc. Am. 73, 1120–1130 (1983)]. These considerations are now applied to construction of approximate adiabatic transforms that accomplish for weakly range-dependent two- and three-dimensional guiding environments what the rigorous transforms do exactly for the range-independent case. Availability of such approximate transform relations is relevant for the direct problem and also for the data inversion procedure that recovers spectral reflection coefficients which vary with range. The theory so far is in its formative stage, without tight asymptotic estimates, but its presentation should serve to introduce general concepts that are relevant for incorporating the effects of range dependence within the spectral wave constituents that characterize guided propagation.
High-frequency coherence functions propagated along ray paths in the inhomogeneous background of a weakly random medium: I—Formulation and evaluation of the second moment
Authors: Mazar R. , Felsen L. B.
Published: October 2005

Ray trajectories have previously been shown to play an important role in determining the transport properties of high-frequency coherence functions constructed from parabolically approximated wave fields. In a weakly fluctuating medium with inhomogeneous refracting background, the parabolic approximation has conventionally been made around a straight propagation direction, thereby restricting its validity to a narrow angular domain with respect to this direction. This limitation is now removed by implementing the parabolic approximation in local coordinates around the curved ray paths connecting a source with an arbitrarily located observer in the background medium. The corresponding partial differential equation for the two-point coherence function is solved by a multiscale expansion method. Solution strategies are distinguished according to whether the observer is reached by a single ray, by two or more rays with vastly differing trajectories, or by two or more closely adjacent rays. In the first instance and also in the second (because the fluctuations decorrelate the separate ray fields), the coherence function can be synthesized by contributions from each individual path. In the third instance, which represents observations near caustics or foci, the adjacent ray fields must be treated collectively. The resulting integral expressions for the intensities can be simplified when the excitation is due to a line source and fluctuations are omitted. The reduced explicit forms are found to agree with the ray acoustically computed deterministic intensities at regular observation points and near simple caustics, thereby lending confidence in the validity of our approach and the quality of our approximations. These asymptotic ray acoustic studies of coherence functions have also been extended to phenomena involving reflection, refraction, and diffraction at interfaces and boundaries.
A new shallow-ocean technique for determining the critical angle of the seabed from the vertical directionality of the ambient noise in the water column
Authors: Buckingham Michael J. , Jones Stephen A. S.
Published: October 2005

In the absence of interference from local shipping, the vertical directionality of ambient noise in the shallow ocean overlying a fast, fluid sediment is a stable feature of the noise field. It is controlled primarily by the bottom reflectivity, which is a time invariant property of the channel. The noise field shows a peak symmetrically placed around the horizontal whose angular width is 2αc, where αc is the critical grazing angle of the bottom. By measuring the noise power distribution in the vertical, αc can be determined and hence the compressional sound speed in the bottom sediment deduced. Measurements of the vertical directionality of ambient noise in shallow water have been made at six sites around the coast of the United Kingdom, using specially designed vertical-line-array sonobuoys. Estimates for the critical grazing angle and the sound speed in the bottom have been derived from the noise data for all six areas. Similar data from independent seismic surveys are available for only one of these sites, the Celtic Sea South. For this area the independent survey yielded a value of αc =28°, which compares closely with the value of αc =26.2° obtained using the new noise technique.
A new simple method of ultrasonic velocity and attenuation measurement in a high absorption liquid
Authors: Matsuzawa Kiichiro , Inoue Naoki , Hasegawa Takahi
Published: October 2005

A special technique is developed to find the cycle-for-cycle matching between the two pulses using two transducers. The one-way travel time of ultrasound is determined with an accuracy of several percent of the period of quartz transducer resonance. The results of the technique show the accuracy of the absolute sound velocity of about 1 m/s, in a highly attenuating liquid using 3-MHz transducers separated by 65 mm.
Spectral and level effects in noise-on-tone suppression
Authors: Sidwell Andrew
Published: October 2005

The effective internal level of a 1-kHz tone at 50 dB SPL was estimated by measuring the forward masking produced on a 10-ms signal tone of the same frequency. Noise containing a spectral notch was then added to the masker tone, and its influence on the effective level of the tone was measured with a variety of noise levels, notch widths, and notch shapes. In experiment 1, the masker tone was centered in the spectral notch, itself centered in a 2-kHz band of noise. As the spectrum level in the noise passbands increased from 6 dB/Hz to 36 dB/Hz, signal threshold decreased, indicating a decrease in masking by the masker tone. This ‘‘unmasking’’ effect of the noise was attributed to suppression of the masker tone by the components in the noise. Unmasking was greatest with the narrowest spectral notch (250 Hz), and decreased to zero as the notch widened to 1500 Hz. Compared to its level when presented alone, the effective internal level of the masker tone could be reduced by up to 30 dB (250-Hz notch, 36 dB/Hz). The relative suppressive strength of individual noise components was estimated in experiment 2, in which the 1-kHz masker tone was located at one edge of a spectral notch, rather than in the center. Noise spectrum level was fixed at 16 dB/Hz. As notch width decreased to zero, on either the high-frequency or low-frequency side of the masker tone, its effective internal level was again reduced by approximately 30 dB. In a tentative analysis, the first derivative of the smoothed threshold function was taken, to provide an estimate of the relative contributions to suppression at 1 kHz of noise components between 250 and 1740 Hz. While this suggested that the suppression region centered on 1 kHz may be extremely wide, possibly as great as 3 oct, the analysis also revealed some possible violations of the assumption of linear summation of effects on which it was based.
Spectral-shape discrimination. I. Results from normal-hearing listeners for stationary broadband noises
Authors: Farrar Catherine L. , Reed Charlotte M. , Ito Yoshiko , Durlach Nathaniel I. , Delhorne Lorraine A. , Zurek Patrick M. , Braida Louis D.
Published: October 2005

This research is concerned with the ability of normal-hearing listeners to discriminate broadband signals on the basis of spectral shape. The signals were six broadband noises whose spectral shapes were modeled after the spectra of unvoiced fricative and plosive consonants. The difficulty of the discriminations was controlled by the addition of noise filtered to match the long-term speech spectrum. Two-interval discrimination measurements were made in which loudness cues were eliminated by randomizing (roving) the overall stimulus level between presentation intervals. Experimental results, examined as a function of intensity rove width, stimulus duration, and stimulus pair, were related to the predictions of a simple filter-bank model whose fitting parameter provides an estimate of internal noise. Most results, with the notable exception of duration effects, were predicted by the model. Estimates of internal noise in each frequency channel averaged roughly 7 dB for long-duration stimuli and 13 dB for short-duration stimuli. Results and predictions are compared to results of other studies concerned with the discrimination of spectral shape.
Attenuation and protection provided by ossicular removal
Authors: Clark William W. , Bohne Barbara A.
Published: October 2005

Behavioral studies of hearing loss produced by exposure to ototraumatic agents in experimental animals, combined with the anatomical evaluation of end-organ pathology, have provided useful information about the relation between dysfunction and pathology. However, in order to attribute a given hearing loss to some pattern of cochlear damage, it is necessary to test each ear independently. The objective of the present study was to evaluate attenuation measured behaviorally and protection to the cochlea provided by removal of the malleus and incus in noise-exposed chinchillas. Results from one behaviorally trained chinchilla with ossicular removal indicated a conductive hearing loss that varied from 41 dB at 0.125 kHz to 81 dB at 4.8 kHz and averaged 60 dB. Counts of missing sensory cells in ears of seven chinchillas with unilateral ossicular removal and exposure to noise (octave band centered at 0.5 kHz, 95 dB SPL, for durations up to 216 days, or centered at 4.0 kHz, 108 dB SPL, for 1.75 h) showed no more cell loss on the protected side than in age-matched control ears. From these data it is concluded that ossicular removal provides enough attenuation to protect the chinchilla cochlea from damage during these noise exposures, and that it will insure monaural responses behaviorally as long as the hearing loss in the test ear does not exceed that in the ear with ossicular removal by approximately 50 dB at any frequency.
A frequency importance function for continuous discourse
Authors: Studebaker Gerald A. , Pavlovic Chaslav V. , Sherbecoe Robert L.
Published: October 2005

Normal hearing subjects estimated the intelligibility of continuous discourse (CD) passages spoken by three talkers (two male and one female) under 135 conditions of filtering and signal-to-noise ratio. The relationship between the intelligibility of CD and the articulation index (the transfer function) was different from any found in ANSI S3.5-1969. Also, the lower frequencies were found to be relatively more important for the intelligibility of CD than for identification of nonsense syllables and other types of speech for which data are available except for synthetic sentences [Speaks, J. Speech Hear. Res. 10, 289–298 (1967)]. The frequency which divides the auditory spectrum into two equally important halves (the crossover frequency) was found to be about 0.5 oct lower for the CD used in this study than the crossover frequency for male talkers of nonsense syllables found in ANSI S3.5-1969 and about 0.7 oct lower than the one for combined male and female talkers of nonsense syllables reported by French and Steinberg [J. Acoust. Soc. Am. 19, 90–119 (1947)].
Response of an edge-supported, annular, foil electret earphone
Authors: Busch-Vishniac Ilene J.
Published: October 2005

The behavior of an annular, edge-supported, foil electret earphone is examined in a two-step procedure. First, the electret static deformation is found using a perturbation series approach. A criterion for static stability is developed and shown to establish an upper limit to the maximum stable static deflection. Second, the dynamic foil electret motion is determined. The dynamic motion is divided into two parts: a linear response and a nonlinear response. Experimental measurements of capacitance and the sound pressure generated in a 6-cm3 cavity compare favorably to the analytical predictions.
Numerical solution for the dynamic moduli of a viscoelastic bar
Authors: Buchanan James L.
Published: October 2005

The dynamic Young’s modulus and loss factor of a viscoelastic material may be calculated as functions of frequency from data on the relative motions of the two ends of a bar of the material that is in harmonic oscillation at that frequency. Most investigators using this technique have confined their measurements to resonant frequencies, but it would be useful to find the moduli of the material at regular, narrowly spaced intervals of frequency. The characteristic equation, from which the moduli of the material are calculated, is investigated with respect to numerical solvability and stability. It is shown that this equation has infinitely many solutions. An apparently effective method of choosing the physically relevant solution is developed. It is found in the case of low-loss materials that at certain frequencies solutions to the characteristic equation lie near zeros of the Jacobian, which are the solutions in the limiting case of a perfectly elastic material. Consequently, low-loss viscoelastic materials will exhibit great sensitivity to errors in measurement at these frequencies. An error analysis is developed in order to estimate the magnitude of this instability. A microcomputer program written to solve these equations is applied to various simulated samples to illustrate the effects of this instability.
Temporal changes in a complex spectral profile
Authors: Yost William A. , Moore M. J.
Published: October 2005

The spectral properties of a complex stimulus (rippled noise) were varied over time, and listeners were asked to discriminate between this stimulus and a flat-spectrum, stationary noise. The spacing between the spectral peaks of rippled noise was changed sinusoidally as a function of time, or the location of the spectral peaks of rippled noise was moved up and down the spectrum as a sinusoidal function of time. In most conditions, listeners were able to make the discriminations up to rates of temporal modulation of 5–10 cycles per second. Beyond 5–10 cps the rippled noise with the temporally varying peaks was indiscriminable from a flat (nonrippled) noise. The results suggest that for temporal changes in the spectral peaks of rippled noise, listeners cannot monitor the output of a single (or small number of) auditory channel(s) (critical bands), or that the mechanism used to extract the perceptual information from these stimuli is slow. Temporal variations in the spectral properties of rippled noise may relate to temporal changes in the repetition pitch of complex sounds, the temporal properties of the coloration added to sound in a reverberant environment, and the nature of spectral peak changes such as those that occur in speech-formant transitions. The results are relevant to the general issue of the auditory system’s ability to extract information from a complex spectral profile.
A device for measuring tactile spatiotemporal sensitivity
Authors: Van Doren Clayton L. , Pelli Denis G. , Verrillo Ronald T.
Published: October 2005

A tactile stimulator array constructed from 88 piezoelectric ceramic plates is described. The array can produce sinusoidal traveling waves with arbitrary temporal frequency, spatial wavelength, and amplitude. Detection thresholds were measured for five temporal frequencies (1, 4, 16, 64, and 256 Hz) and five spatial wavelengths (1.81, 3.62, 7.23, 14.5, and ∞ mm), and were plotted as a three-dimensional, spatiotemporal threshold surface. Detection thresholds were also measured using a conventional vibrator and a large circular contactor simulating the infinite wavelength stimulus produced by the array. The results describe the spatial and temporal frequency sensitivity of the P and NP I cutaneous receptor populations.
Acoustic properties for place of articulation in nasal consonants
Authors: Kurowski Kathleen , Blumstein Sheila E.
Published: October 2005

The goal of this study was to determine whether acoustic properties could be derived for English labial and alveolar nasal consonants that remain stable across vowel contexts, speakers, and syllable positions. In experiment I, critical band analyses were conducted of five tokens each of [m] and [n] followed by the vowels [i e a o u] spoken by three speakers. Comparison of the nature of the changes in the spectral patterns from the murmur to the release showed that, for labials, there was a greater change in energy in the region of Bark 5–7 relative to that of Bark 11–14, whereas, for alveolars, there was a greater change in energy from the murmur to the release in the region of Bark 11–14 relative to that of Bark 5–7. Quantitative analyses of each token indicated that over 89% of the utterances could be appropriately classified for place of articulation by comparing the proportion of energy change in these spectral regions. In experiment II, the spectral patterns of labial and alveolar nasals produced in the context of [s]+nasal ([m n])+vowel ([i e a o u]) by two speakers were explored. The same analysis procedures were used as in experiment I. Eighty-four percent of the utterances were appropriately classified, although labial consonants were less consistently classified than in experiment I. The properties associated with nasal place of articulation found in this study are discussed in relation to those associated with place of articulation in stop consonants and are considered from the viewpoint of a more general theory of acoustic invariance.
English verification of the STI method for estimating speech intelligibility of a communications channel
Authors: Anderson B. Wayne , Kalb Joel T.
Published: October 2005

An objective measure of the quality of speech communications channels was developed and described by Steeneken and Houtgast [J. Acoust. Soc. Am. 67, 318–326 (1980)]. By calculating the speech transmission index (STI), this method provides an estimate of speech intelligibility for a variety of communication distortions, but the method has been validated only for the Dutch language. For this reason, questions arise about its applicability for use with English. Using the standard Harvard PB-word test for speech intelligibility, it was shown that the STI method is a valid method for testing the speech transmission of communications channels intended for use with the English language. New STI curves were generated for both the English PB-word test and the Modified Rhyme Test.
Sum and difference frequency generation due to noncollinear wave interaction in a rectangular duct
Authors: Hamilton Mark F. , TenCate James A.
Published: October 2005

Noncollinear wave interaction in a rectangular duct is investigated both theoretically and experimentally. An inhomogeneous wave equation, exact to second order in the field variables, is derived for the sum and difference frequency pressure waves generated by noncollinear interaction of two finite amplitude plane waves in a lossless fluid. This equation is extended to the interaction of waves in higher-order modes of a rectangular duct. Quasilinear solutions are obtained, and tube wall attenuation is included ad hoc. Experimental results are reported for the interaction of waves in the (0,0) and (1,0) modes of an air-filled rectangular duct. Theory and experiment are in excellent agreement with regard to oscillatory structure of the sum and difference frequency wave fields. Although overall agreement between theory and experiment is reasonable (±2 dB), it is not within estimated experimental error (±1 dB). It is shown that because local rather than cumulative nonlinear effects dominate the interaction, knowledge of the proper second-order source condition is of crucial importance. Discrepancies between the predicted and measured amplitudes are attributed to an inadequate description of the source condition.
Variation of the strain spectra of random waves in nonlinear elastic materials
Authors: Matsumoto Eiji
Published: October 2005

Random waves in one-dimensional nonlinear elastic materials are considered. An integrodifferential equation is derived that governs the variation of the strain spectrum during propagation. By discretizing the spectrum with respect to the frequency, the spectral equation reduces to a system of ordinary differential equations for the discrete values of the spectrum. Numerical results are given for plane random longitudinal waves in an aluminum alloy. It is found that harmonic sound waves are generated for a narrow-band spectrum, the power spectrum grows faster for higher frequencies for a wideband spectrum, and secondary waves are generated due to the interaction of two bands of spectra.
Compressional waves in a layered fluid medium pierced by a right circular cylinder
Authors: Rice J. A. , Willen D. E.
Published: October 2005

There are very few exact solutions available for wave propagation in plane-layered materials that are pierced by a cylindrical hole. This is unfortunate since these problems occupy a central role in geophysics. Exact solutions for the cases of an empty hole and an infinitely rigid hole, where the geometry is separable so that the classical transform method is applicable, are presented. It is hoped that the exact solutions presented herein will provide a check on more general numerical methods.
Image reconstruction and range distance estimation for planar holographic systems using symmetry properties
Authors: Lee Hua
Published: October 2005

In a recent paper by Narasimhan et al. [J. Acoust. Soc. Am. 79, 382–385 (1986)] a method is proposed for the determination of object range distance for planar holographic systems by phase unwrapping the spectral distribution along the major axes. In this letter, an alternative approach is introduced to improve the range distance estimation process. This technique simplifies the procedure by utilizing the Fourier transformation symmetry properties associated with the real object distribution and propagation transfer function. The computation complexity can be significantly reduced because of the elimination of the complicated computing and phase unwrapping steps. In addition, the accuracy of the distance estimation is improved by using the complete two-dimensional spectral distribution instead of only the variation along the axes.
Instructional laboratory experiment on the effect of sound reflection on the driving-point impedance loop of a small sonar transducer
Authors: Nahar N. , Stumpf Folden B.
Published: October 2005

This letter presents an experiment in acoustics to be used in a laboratory course for advanced undergraduate or beginning graduate students in physics or engineering. It describes the equipment used and the effect of reflection from a plate immersed in water on the driving-point impedance of a small sonar transducer placed at the air–water surface above the plate.
Reflection of an obliquely incident S
H plane wave at a plane interface between an elastic solid and a viscoelastic liquid
Authors: Kiel/czyński P. , Pajewski W.
Published: October 2005

The results of numerical calculations are presented for the reflection coefficient of the shear horizontal (SH) plane waves incident on an elastic solid–viscoelastic liquid interface. The linear viscoelastic Maxwell liquid with one relaxation time is considered. The modulus and phase of the reflection coefficient as a function of incidence angle and frequency are determined numerically for typical parameters of the considered media. The validity of an approximate expression for the reflection coefficient is analyzed. Some new properties of the reflected SH wave are considered and discussed.
On the reflection of acoustic waves from a slightly curved interface
Authors: Lerche I.
Published: October 2005

It is shown that the effect of a slightly curved surface on the behavior of acoustic ‘‘head waves’’ is: (a) to make the head-wave arrival time weakly dispersive with frequency; (b) to cause a curvature in the head-wave arrival time with offset, roughly as (offset)3/2; (c) to cause the head wave to arrive earlier (later) than that corresponding to a flat surface for a synclinal (anticlinal) shape. The amplitude behavior of the head wave is also found to be distorted with (d) a lower (higher) high-frequency/low-frequency ratio for reflection from a syncline (anticline) and (e) an enhancement (diminution) relative to that for a head wave from a flat surface for a synclinal (anticlinal) surface with the enhancement (diminution) exponentially dependent on offset, roughly as (offset)3/2 in the exponent. These calculations have been done in order to point out that it may be possible to use these features of head waves in order to unravel subtle structural traps in the subsurface, which vary slowly and would not be noticed in conventional seismic processing.
Active suppression of acoustic resonance
Authors: Curtis A. R. D. , Nelson P. A. , Elliott S. J. , Bullmore A. J.
Published: October 2005

The minimization of acoustic potential energy has been proposed as a method of actively controlling a harmonic reverberant sound field. In this paper an analysis of plane waves in a finite length duct provides insight into the physical mechanisms of this method and allows comparison with two other methods, the acoustical virtual earth and the absorbing termination. A practical technique of achieving the reduction of acoustic potential energy is presented and discussed.
A turbulence model for sound propagation from an elevated source above level ground
Authors: Johnson Mark A. , Raspet Richard , Bobak Michael T.
Published: October 2005

Measurements of the variance and scale of the index of refraction fluctuations in the turbulent atmosphere performed in conjunction with a sound propagation study are described. The theory of turbulence generation in the atmosphere is examined and used to develop a model for the functional dependence of variance and scale with altitude from the data. This model is used to calculate the expected turbulence effects for a nonrefracting atmosphere and the results are compared with data from the sound propagation study. This study demonstrates that turbulence effects are smaller for elevated sources than for sources close to the ground. The calculations necessary for a complete description of the turbulence effects are described.
Effect of random velocity fluctuations on underwater scattering
Authors: Beran Mark J. , Whitman Alan M.
Published: October 2005

There is a well-developed theory to account for the effect of random fluctuations in the sound speed on the underwater scattering of acoustic radiation. Here it is shown that the theory may be readily extended to include the effect of random fluctuations in fluid velocity. It is assumed that the characteristic time and length scales associated with the velocity correlation functions are long when compared to the corresponding scales (period and wavelength) of the acoustic radiation. The application of the theory to ocean studies is discussed with emphasis on the utility of using an inverse method to find the lateral correlation function.
Strategies for the representation of a tone in background noise in the temporal aspects of the discharge patterns of auditory-nerve fibers
Authors: Miller Michael I. , Barta Patrick E. , Sachs Murray B.
Published: October 2005

The responses of populations of auditory-nerve fibers to both a 1.0-kHz tone, and 1.0-kHz tone in broadband noise, have been measured. Period histograms were generated from fiber spike trains and discrete Fourier transforms (DFTs) with a resolution of 125 Hz were computed from each histogram. Sample mean and sample variance statistics were generated for period histograms of response and for temporal response measures derived from discrete Fourier transforms. It is demonstrated how the statistical properties of auditory-nerve fiber response determine the strategy for the estimation and discrimination of particular stimulus components. When the tone is presented alone, the entire population of auditory-nerve fibers provides statistically reliable estimates of the 1.0-kHz tone. Upon addition of the broadband noise stimulus only those units with characteristic frequencies which are close in frequency to the 1.0-kHz stimulus provide spectral estimates which have high signal-to-noise ratios (mean-squared-to-variance ratios). Estimates of the 1.0-kHz-tone stimulus derived from auditory-nerve fibers with characteristic frequencies which are far from the 1.0-kHz stimulus are statistically unreliable. Based on the responses of the population of auditory-nerve fibers, the strategy for estimating the 1.0-kHz-tone stimulus is to derive estimates of the 1.0-kHz stimulus from the subpopulation of neurons with characteristic frequencies close to the 1.0-kHz stimulus. It is concluded that neurons which are tuned close to 1.0 kHz provide the central nervous system (CNS) with the most salient information about the 1.0-kHz stimulus in the presence of the broadband background.
Conservation of adapting components in auditory-nerve responses
Authors: Westerman Larry A. , Smith Robert L.
Published: October 2005

The responses of single auditory-nerve fibers of Mongolian gerbil were studied using tonal stimuli. The peristimulatory adaptation of firing rate in response to tone bursts presented in quiet and during a background stimulus is described quantitatively. The total transient response which can be produced to the onset of a tone burst, whether presented in quiet or as an intensity increment, is limited and appears to demonstrate a form of conservation. Specifically, the total numbers of spikes produced by the rapidly adapting component, and the slower short-term adaptation component, are proportional at all intensities, and are limited for each fiber. Furthermore, when an incremental stimulus is presented on a background, the total transient response to the background and to the increment is limited and depends upon the final intensity, not the background intensity. When the presumed underlying synaptic drive is derived by removing the effects of refractoriness from the spike train, the same conservation of the transient response components, and proportionality between rapid and short-term components, are observed.
Measurement of the attenuation characteristics of nonlinear hearing protective devices using the auditory brain stem response
Authors: Wilde Graham L. , Humes Larry E.
Published: October 2005

The purpose of this study was to determine the feasibility of using the auditory brain stem response (ABR) as a method of measuring the attenuation characteristics of nonlinear hearing protective devices. Sound field ABRs were recorded from seven normal hearing subjects with and without hearing protection. Three hearing protectors (two nonlinear and one linear) were evaluated. Test stimuli, consisting of 4000-Hz tone pips, were presented in a sound field. Linearity and the amount of attenuation for each hearing protector were derived by comparing the protected and unprotected latency-intensity functions for wave I of the ABR. Results indicate that the ABR may be used effectively to measure the attenuation characteristics of linear and nonlinear hearing protectors for high-frequency impulse-type stimuli.
Recognition of nonsense syllables by hearing-impaired listeners and by noise-masked normal hearers
Authors: Humes Larry E. , Dirks Donald D. , Bell Theodore S. , Kincaid Gail E.
Published: October 2005

In the present study, speech-recognition performance was measured in four hearing-impaired subjects and twelve normal hearers. The normal hearers were divided into four groups of three subjects each. Speech-recognition testing for the normal hearers was accomplished in a background of spectrally shaped noise in which the noise was shaped to produce masked thresholds identical to the quiet thresholds of one of the hearing-impaired subjects. The question addressed in this study is whether normal hearers with a hearing loss simulated through a shaped masking noise demonstrate speech-recognition difficulties similar to those of listeners with actual hearing impairment. Regarding overall percent-correct scores, the results indicated that two of the four hearing-impaired subjects performed better than their corresponding subgroup of noise-masked normal hearers, whereas the other two impaired listeners performed like the noise-masked normal listeners. A gross analysis of the types of errors made suggested that subjects with actual and simulated losses frequently made different types of errors.