bluuebunny/crossref_metadata_2025 huggingface dataset:
Technique for the perceptual investigation of F contours with application to French
Authors: Delgutte Bertrand
Published: October 2005

Two experimental techniques were used in this study: (1) an analysis of F0 contours of French sentences containing words likely to express the speaker’s attitude (modals, negative, adverbs, quantifiers) and (2) listener’s judgements of the naturalness of synthetic sentences in which the F0 contour was systematically manipulated. The F0 contours were characterized by schematic patterns [J. Vaissière Res.Lab.Electron., Q.Prog.Report No. 115, MIT, 251–262 (1975)]. For all the sentences that were studied, the configurations of patterns frequently observed in the analyzed corpus were judged most natural when synthethized. This result suggest that the features of the F0 contours most relevant to naturalness are preserved in the pattern representation. Three types of patterns were distinguished: (1) a prominent, demarcative pattern (P2); (2) a prominent, nondemarcative pattern (PE); (3) nonprominent, nondemarcative patterns. A P2 pattern often occurred at the end of a syntactic constituent. Listeners’ judgements showed that a P2 at the end of a syntactic constituent is rarely required for naturalness, but a P2 in contradiction to syntax causes unnaturalness. Prominent patterns (P2 or PE) often occurred on negatives, adverbs, and quantifiers. However, the presence or absence of a prominent pattern on these words does not affect naturalness.
Steady-state sound in an enclosure with diffusely reflecting boundary
Authors: Carroll M. M. , Miles R. N.
Published: October 2005

An expression is derived for the steady-state sound energy density in an enclosure containing a distribution of simple sources and having a diffusely reflecting absorbent boundary. Calculation of the reverberant sound energy density requires prior calculation of the wall intensity, which is found by solving an integral equation. Solutions are obtained for a simple source in a spherical enclosure.
Estimation of monopole power radiated in a reverberation chamber
Authors: Waterhouse Richard V.
Published: October 2005

A monopole source radiates a pure tone. It is desired to estimate the free-field value W0 of its power output from reverberation chamber measurements, in which both source and receiver positions are varied. From the known distribution of values when only the receiver position is varied, the statistics of estimates of W0 are derived.
On the scattering of sound by internal waves in the ocean
Authors: Desaubies Yves J. F.
Published: October 2005

The parabolic approximation to the wave equation is applied to the calculation of the spectral density of amplitude and phase fluctuations of a plane sound wave propagating through a random field of internal waves in the ocean. The dependence of the predicted spectra on wave number and frequency shows that the lowest-mode internal waves dominate the phase variance, while the amplitude fluctuations are controlled by intermediate scales. The results are compared with previous theories and available data. There is a discrepancy between observed amplitude spectra and predictions based on the internal wave models. It is concluded that internal waves are not solely responsible for the scattering of sound in the ocean and that other effects must contribute.
A plane wave reflection loss model based on numerical integration
Authors: Hawker Kenneth E. , Foreman Terry L.
Published: October 2005

A method is developed for computation of the complex plane-wave reflection coefficient for a class of geoacoustic models of the ocean bottom, consisting of an arbitarary number of inhomogeneous (fluid) sediment layers overlying a a semi-infinite homogeneous solid substrate (basement). Within the sediment layers the density, sound speed, and attenuation are permitted to vary arbitrarily with depth. An appropriate formulation of the problem permits the reflection coefficient to be constructed using the results obtained from the direct numerical integration of the depth separated wave equation. The entire computation is thus reduced to that of an initial value problem to which established methods can be applied. The Runge–Kutta method which was chosen permits user selected local error tolerances. Extensive application of the resulting computer code has shown that for a wide class of physically reasonable models global error is bounded, and accuracy far in excess of the minimum required is easily obtained. Requirements imposed on computer word size and available core are modest, and the model can be implemented on any modern general purpose computer and perhaps on a minicomputer.
Growth function for human response to large-amplitude impulse noise
Authors: Schomer Paul D.
Published: October 2005

The U. S. Environmental Protection Agency has proposed the use of C-weighted day/night level for the assessment of impulse noise such as the noise resulting from sonic boom, blast noise (artillery, armor, demolition, etc.) and other large-amplitude impulse sources. One remaining question pertaining to the use of C-weighting has been the growth function for human response to impulse noise. This question arises because work by Kryter and by Young using peak values and/or small amplitudes exhibited growth functions of 6−7dB for a doubling of annoyance, while the growth function for human response to common sources (planes, vehicles, etc.) increases by about 10 dB for a doubling of annoyance. Kyter’s and Young’s data are reanalyzed herein by using C-weighting and by including only large-amplitude data. This reanalysis results in a growth function for human response to impulse noise which increases by about 10 dB for a doubling of annoyance. This equality of growth function between common A-weighted noise and C-weighted impulse noise further supports the use of C-weighted day/night level for assessment of sonic boom, blast noise, or other large-amplitude impulse noises having similar spectral content.
Laser-generated stress waves in liquids
Authors: Sigrist Markus W. , Kneubühl Fritz K.
Published: October 2005

The generation of laser-induced stress waves in liquids by the vaporization process and the thermoelastic effect was studied experimentally. A high-speed camera and special high-sensitivity stress transducers with a response time of a few nanoseconds have been used for these investigations. The experimental results obtained for water, n-heptane, and carbon tetrachloride are discussed. For the first time, the individual contributions of vaporization and the thermoelastic effect on stress generation are separated. In addition, tunable high-frequency acoustic waves, with frequencies up to 60 MHz, have been generated in water by the impact of a laser pulse exhibiting longitudinal mode beating. Since existing theories on the thermoelastic generation of acoustic waves do not yield satisfactory agreement with our experimental data, a new spherical model is proposed, where the transient heating caused by the laser impact, is represented by the three-dimensional heat pole. This solution of the equation of heat conduction corresponds to a Gaussian distribution of the excessive temperature in space, and thus to the TEM00 mode of the incident laser beam. An analytical solution of the thermoelastic pressure wave is derived for this case of temperature distribution. Its good agreement with the experiment is discussed for various liquids and for two different laser characteristics.
The interaction of sound with noise in water
Authors: Stanton T. K. , Beyer R. T.
Published: October 2005

The nonlinear interaction of a monochromatic ultrasonic signal with audio-frequency noise has been measured in water. The scattered signal lies in sidebands corresponding to the sum and difference components of the frequencies involved. The intensity of the scattered signal increases linearly with interaction distance and quadratically with the signal frequency in the range 1–5 MHz, in agreement with the theory of Westervelt.
Propagation of nonlinear acoustic waves induced by a vibrating cylinder. I. The two-dimensional case
Authors: Ginsberg Jerry H.
Published: October 2005

This study details the first successful uniformly valid expansion for a multidimensional nonlinear wave in a system described by curvilinear coordinates. The problem of interest is the steady-state wave motion induced within an inviscid compressible fluid by an infinite circular cylinder executing a harmonic planar vibration in its nth circumferential mode. The solution is achieved by employing a regular perturbation series to obtain an outer expansion for the velocity potential. Then outer expansions for the pressure and the velocity components are derived by the method of renormalization. Finally, uniformly valid expansions for the response are determined by matching the outer solutions with the results of a linearized analysis, which represent the inner solutions. Examples considering the effect of the nondimensional parameters are treated by presenting pressure and velocity profiles, as well as nodal and antinodal lines of radial velocity. The range of validity for farfield approximations is discussed.
Nonlinear and thermal acoustic sources
Authors: Merklinger Harold M.
Published: October 2005

Certain nonlinear acoustic phenomena may be explained in terms of virtual or secondary sources. The parametric array is one classic example [P. J. Westervelt, J. Acoust. Soc. Am. 35, 535–537 (1963)]. It is argued here that there must also exist formally similar sources due to the thermoviscous heating of a fluid by a modulated sound wave. At moderate to high modulation frequencies the nonlinear mechanism dominates, but at sufficiently low modulation frequencies, the thermal phenomenon must become the more significant effect.
Some experiments with the bass drum
Authors: Fletcher Harvey , Bassett Irvin G.
Published: October 2005

Measurements were made of bass drum tones to determine the characteristic properties of the sound. The analysis was performed with computer-modeled band-pass filters with 3-Hz bandwidth. Frequency, peak sound pressure level, and decay rate were determined for each of the major components from 40 Hz up to 1000 Hz. The frequencies of the components were found to change with time, decreasing as amplitude of vibration decreases. Observed frequencies agreed with theoretical values to within 5% in some cases and less than 1% in most. It was found that a blow near the center of the drum puts more energy into the lower-frequency components, while a blow near the edge emphasizes those of higher-frequencies. Drum tones were synthesized by summing the contributions of each of the important components. Recordings of synthesized and real tones were presented randomly in listening tests. Synthesis was viewed as successful when the synthetic tones were judged to be real as often as they were judged to be synthetic. In the listening tests, a jury of 31 people correctly identified the synthetic tones only 51% of the times those tones were presented.
Optimum estimation of signal parameters in non-Gaussian noise
Authors: Sheehy Jerome J.
Published: October 2005

The purpose of this paper is to derive optimum estimators for the estimation of signal parameters when the signal is emersed in an additive, not necessarily Gaussian noise field. Also, expressions for evaluating their performance are derived and, for the nonrandom signal case, the results compared with the familiar Cramer–Rao equation which provides a lower bound for the variance of an unbiased estimate. A new lower bound is derived for the variance of an unbiased estimate of the signal power for the case where the signal is a zero mean, random process and again the performance of the estimator, which is optimum for this type of signal, is compared with this new bound. In general it is found that the performance of the optimum estimator when operated in a non-Gaussian noise field is superior to that which can be obtained when the noise is Gaussian.
Subjective loudness of N-wave sonic booms
Authors: Niedzwiecki A. , Ribner H. S.
Published: October 2005

A loudspeaker-driven simulation booth with extended rise-time capability (down to 0.22 ms) has been used for subjective loudness tests of N-wave sonic booms. The test series compared signatures over a range of 0.22–10 ms in rise time, 100–250 ms in duration and 0.5–2.5 psf (24–120 Pa) in peak overpressure. In one sequence, the tradeoff between rise time and overpressure was measured for equal loudness; in another, the tradeoff between duration and overpressure. For equal loudness 10-ms rise time required 8-dB higher overpressure than for 1-ms rise time. Duration had little effect in the range 100–200 ms, but at 250 ms noticeably enhanced the loudness. These results confirm those measured by Shepherd and Sutherland made at 1-ms rise time and above (except for the anomalous enhancement at 250-ms duration), and extend the measurements down to 0.22 ms. There is also good agreement with theoretical predictions (Johnson–Robinson, Zepler–Harel methods) except for the 10-ms rise time and 250-ms duration cases.
Diffraction of elastic waves by cylindrical cavity in a half-space
Authors: Datta S. K. , El-Akily Nabil
Published: October 2005

Diffraction of two dimensional elastic waves by a cylindrical cavity in a half-space is considered in this paper. The paper is divided into two parts. In the first part we use an integral representation for the scattered displacement field to derive its asymptotic behavior at large distances from the cavity. We also give a formal derivation of the representation of the displacement field in terms of multipolar potentials. In the second part we use a method of matched asymptotic expansions to calculate the scattered field. Numerical results are presented for the surface displacements due to Rayleigh waves scattered by a circular cylindrical cavity.
On an extended parabolic-coherence function propagation model
Authors: McCoy John J.
Published: October 2005

A parabolic wave theory is considered in which the energy flux through an elemental aperture is required to lie in directions measured relative to a ’’local’’ principal propagation direction that can be termed narrow angled. This can be compared to the more commonly encountered theory, in which a ’’global’’ principal propagation direction is used. A propagation model is then developed which is formulated in terms of an acoustic field measure termed the acoustic intensity angular spectral density. The relationship between this propagation model and the geometric theory is considered, with the latter being recovered in the appropriate limit. A sample calculation is carried out for the behavior of a beamed signal in the vicinity of a point caustic.
Moulded piezoelectric transducers using polar polymers
Authors: Micheron F. , Lemonon C.
Published: October 2005

Polar polymer such as PVC, PVF and PVF2 show strong piezoelectric activity after being stretched and poled. They were used up to now in plane or cylindrical configurations. We show that such polymers can be moulded and poled, which constitutes a new generation of piezoelectric transducers. Example is given of a high range loudspeaker using a moulded PVC film.
Perceptual origins of the phoneme boundary effect and selective adaptation to speech: A signal detection theory analysis
Authors: Elman Jeffrey L.
Published: October 2005

Differences in discriminability of stimuli near phoneme boundaries and findings from selective adaptation have been used to argue for the existence of neurophysiological mechanisms—feature detectors—which mediate the perception of speech and speechlike sounds. A detection theory model was used in order to discover whether or not the phoneme boundary effect and the shift in phoneme boundary after adaptation might rather be attributable to changes in response bias. This model was applied in the analysis of phoneme identifications of three sets of stimuli (/áp--áb-/, /b-d/, /b-p/) before and after adaptation. While the origins for the phoneme boundary effect appear to lie below the level of response bias, findings suggest that identification changes after adaptation may be due solely to shifts in criterion, rather than changes at the sensory level.
Wave propagation in liquid-saturated open-cell foam
Authors: Chase David M.
Published: October 2005

The coupled equations of motion for linearly interacting elastic foam and saturating fluid are formulated and solved for excitation at fixed frequency and wave number. As known from previous work on porous media, the longitudinal waves in the foam and fluid are coupled, and the shear wave in the foam is modified while imparting rotational motion to the fluid. Resulting fields are expressed suitably for use in situations of axisymmetry. The characteristic equation for free waves and relations between field coefficients are given explicitly for propagation within a rigid tube. Acoustically, a characteristic feature of the application to liquid-saturated foam is the high mass porosity and compressibility of the empty foam, commending a corresponding limiting approximation. Applied to propagation in a rigid tube, this yields a modification of of the acoustic wave speed and impedance due to foam that is measured by (sQ)1/2(ωa/ct)−1, where Q=iΔ/(1+iΔ), Δ is a drag-interaction coefficient, s the ratio of the mass of foam to that of fluid, a the tube radius, and ct the shear-wave speed of empty foam. The interaction effect thus exhibits saturation, since Q becomes independent of Δ for sufficiently strong interaction. In a contrary limit where the foam is nearly stationary, the effect of foam is measured rather by Δ. Poiseuille flow in the presence of foam is also treated. The hydrodynamic determination of Δ is carried through for idealized foam geometries. In the viscous domain where the viscous depth exceeds the filament diameter, Δ is real and varies as ν/ωD2, where D is pore size, with coefficient weakly dependent on porosity. At high frequencies Δ becomes negative imaginary on account of the induced-mass effect.
Developmental study of vowel formant frequencies in an imitation task
Authors: Kent R. D. , Forner L. L.
Published: October 2005

Imitations of ten synthesized vowels were recorded from 33 speakers including men, women, and children. The first three formant frequencies of the imitations were estimated from spectrograms and considered with respect to developmental patterns in vowel formant structure, uniform scale factors for vowel normalization, and formant variability. Strong linear effects were observed in the group data for imitations of most of the English vowels studied, and straight lines passing through the origin provided a satisfactory fit to linear F1−F2 plots of the English vowel data. Logarithmic transformations of the formant frequencies helped substantially to equalize the dispersion of the group data for different vowels, but formant scale factors were observed to vary somewhat with both formant number and vowel identity. Variability of formant frequency was least for F1 (s.d. of 60 Hz or less for English vowels of adult males) and about equal for F2 and F3 (s.d. of 100 Hz or less for English vowels of adult males).
Pitch extraction from corrupted harmonics of the power spectrum
Authors: Sreenivas T. V. , Rao P. V. S.
Published: October 2005

Unlike most frequency domain methods for pitch extraction, here the pitch is computed from a few selected high quality peaks in the spectrum, achieving greater reliability. A new approximate greatest common devisor (AGCD) algorithm is proposed to compute the fundamental frequency of a given set of corrupted harmonics. Authentic harmonic peaks ar4e obtained by logical filtering of the spectrum and the computed fundamental frequency is subjected to an error test using the best of the harmonic peaks. Thus the algorithm provides a voiced–unvoiced decision, as well as the pitch for voiced regions. The results are uniformly good for male and female voices, and error rates are comparable to those for the best algorithms reported in the literature.
Mechanism of sound production and air recycling in delphinids: Cineradiographic evidence
Authors: Dormer Kenneth J.
Published: October 2005

Soft tissue silicone-casting techniques, spot-film radiography and cineradiography were combined to examine the in situ anatomy and movement of the upper airway structures in live-phonating and dead delphinid porpoises. Three species, Tursiops truncatus, Tursiops gilli, and Stenella longirostris were studied under high-speed x-ray motion picture cameras to observe the movements in the laryngeal and nasal regions associated with sound production. Accurate reconstructions of the nasal sac anatomy were made by associating castings of silicone rubber, with various x-ray photographs using radiocontrast materials. Sounds produced during the video recordings were simultaneously recorded through a contact piezoelectric hydrophone and stored on magnetic tape. Movement of the left nasal plug was found to be precisely associated with internal whistle production, and the right nasal plug was speculated to be the source of internal click production. Externally produced sounds were generated at the blowhole and the air supply control mechanism was found to be the same for all three types of phonation. The nasopharyngeal air space in the anteroventral portions of the skull and in the bony nares controlled the outward movement of air into the upper passages. The nasopharyngeal muscular ’’pump’’ also functioned in withdrawing spent air back down from the upper passages.
Geographic variation of low frequency sound absorption in the Pacific Ocean
Authors: Lovett Jack R.
Published: October 2005

A contour chart of the Pacific Ocean shows the variation in the boric acid sound absorption term as determined by the pH value at the SOFAR axis.
Influence of earphone-cushion center-hole diameter on the acoustic output of audiometric earphones
Authors: Richards W. D. , Frank T. A. , Prout J. H.
Published: October 2005

Although the dimensions of the MX-41/AR earphone cushion are specified in ANSI S3.6−1969, nonstandard MX−41/AR cushions are still found on some audiometers. Variations in the diameter of the cushion’s center hole are shown to affect the coupler calibration of the earphone and also hearing threshold measurements at high audiometric frequencies.
Production and propagation of sound in a duct
Authors: Keller Jakob J.
Published: October 2005

The problem of sound propagation in a duct is investigated. Several results which have been deduced for isentropic duct flow by previous authors are extended to the case where entropy convection is included. For this more general case, a concept is developed to guide the solution of wave-propagation problems in an optimal manner. Furthermore, it is shown that some new aspects of isentropic wave propagation emerge. To illustrate the methods, the stability of waves behind a shock wave is considered.
Sound radiation from an elastically supported circular plate
Authors: Suzuki Hideo , Tichy Jiri
Published: October 2005

In order to discuss the sound radiation from a direct-radiator loudspeaker in the high-frequency region, an elastically supported circular plate in an infinite baffle is used. The normal modes of this plate is consistently treated from the free boundary to the simply supported boundary, which are the limiting cases of the elastically supported boundary, by defining a dimensionless parameter representing the ratio of the edge stiffness to the bending stiffness of the plate. It is found that the frequency response curve is determined by the resonance between the plate and the acoustic fluid for heavy loading, and between the plate and the mechanical impedance of the voicecoil for light loading, both with different shapes of response curves around the resonance frequencies.
Effect of orthotropy on the sound transmission through plywood panels
Authors: Ordubadi Afarin , Lyon Richard H.
Published: October 2005

The peak in sound transmission through a single isotropic panel at the critical frequency causes a drop in transmission loss (TL) of that panel and of composite walls constructed with such a panel as a face sheet. In investigations on a composite wall with plywood face sheets and Styrofoam core, such a coincidence dip was not observed. The aim of this study is to investigate the disappearance of coincidence notch and the probable causes for such a phenomena. The bending stiffness of a single ply of plywood changes gradually from the softest direction to the stiffest direction. Therefore, the bending wave phase velocity and sound transmissibility change with direction. It is hypothesized that for a group of sound waves randomly incident on the panel, this change in transmissibility eliminates or lowers the peak and, therefore, the coincidence notch smoothens. A plywood panel consists of plies laminated with their grains in different directions. These laminations of the plys may reduce orthotropy in thick plywood panels. A comparison of theoretically redeicted and experimentally observed TL of plywood sheets supports the hypothesis that antisotropy is the reason for a lack of coincidence transmission for some plywood sheets.
Effects of stimulus frequency on adaptation in auditory-nerve fibers
Authors: Abbas Paul J.
Published: October 2005

Several experimental methods of depressing the response of auditory-nerve fibers to tonal stimuli have been shown to reduce the response to signal frequencies at or near fiber CF (characteristic frequency) more than to frequencies greater or less than CF. In this study we have used a short adapting tone presented before each test-tone burst to reduce the fiber’s response to the test tone. We observed the effects of changing test frequency when the adapting frequency was held constant at fiber CF. The depression in discharge rate was found to be approximately constant across test frequency.
Acoustic radiation force on a sphere in a quasistationary wave field—experiment
Authors: Hasegawa Takahi
Published: October 2005

The acoustic radiation force on a sphere in quasistationary waves has been investigated experimentally. The radiation forces measured with fused silica spheres have been compared with a previous theory by the present author which takes into account the elasticity of the sphere material. Good agreement has been found. It has been demonstrated that the acoustic radiation forces on fused silica spheres show much deviation from the conventional theory for rigid spheres for ka larger than approximately four.
Effects of atmospheric turbulence on the interference of sound waves above a finite impedance boundary
Authors: Daigle G. A.
Published: October 2005

The interference spectrum between direct and ground-reflected sound waves is strongly influenced by fluctuations in their phase and amplitude induced by propagation through turbulence. Measurements of the interference spectrum at distances up to 45 m over a flat asphalt surface were shown previously to be in satisfactory agreement with a spherical wave theory that allowed for partial covariance between the phases of the interfering waves. The amount of covariance was claculated from simultaneous measurements of wind and temperature fluctuations in the atmosphere. This theory has now been extended to include propagation over ground of finite acoustic impedance and provides an explanation for measurements of jet noise over grass to a distance of 1100 m. Above 300 Hz the sound levels are up to 10 dB higher than predicted by coherent acoustic theory. The meteorological parameters were used as constants adjusted for best fit and agreement is obtained by assuming standard deviations in phase velocity of about 1 in 1000, and a correlation length of about 1 m—typical of values measured in Ottawa. Covariance of sound amplitude, being relatively more important at long distances, is now also included—at short distances its effect is negligible compared with that of phase convariance. Phase-amplitude convariance is negligible at all distances.
Propagation paths to Midway Island
Authors: Nutile David A. , Guthrie Albert N.
Published: October 2005

The propagation paths from shallow explosive sources to a SOFAR axial receiver located near Midway Island were determined by examination of the arrival pattern making up each received shot signature. The sources were detonated at shallow depths (200 m) along a 1650 km track NE of the hydrophone. Shot signatures were aligned by computer on the basis of travel time and range. The identification of arrivals was based upon a comparison of this signature alignment with one produced by computed signatures using TRIMAIN, a mathematical ray trace model. The principal ray paths are RR, deep cycling rays which can be classified by the number of times they have turned under below the SOFAR axis. Large scale oceanographic features determine the arrival structure and serve to identify the ray paths producing it.
The observation of pulsed ultrasonic gratings in the optical farfield
Authors: Riley Ward A.
Published: October 2005

An optical method is described for studying acoustical pulses as short as two or three cycles in duration in the low-megahertz frequency range. A collimated light beam having a width of one ultrasound wavelength is observed in the optical farfield of the ultrasonic grating midway between the maxima of the central and first diffraction orders. A close approximation to both the amplitude and phase of the acoustical pressure along the light path is obtained. This method is proposed as a simple calibration procedure for recording the transmit pulse characteristics of medical ultrasound systems.
Vibrational double relaxation in liquid pyridine
Authors: Takagi Kenshiro , Negishi Katsuo
Published: October 2005

Ultrasonic and hypersonic property of liquid pyridine has been studied at 20° and 30°C with three techniques: pulse-echo-overlap, high-resolution Bragg reflection, and Brillouin scattering. The sound velocity observed over the frequency range from 3 MHz to 7 GHz suggests two relaxation regions, one centered at 762 MHz and the other at 3.9 GHz at 20°C. The velocity-dispersions in the UHF and in the hypersonic ranges are 94 m/s and 65 m/s, respectively. The same type of vibrational double relaxation as observed in liquid benzene is hypothesized. Quantitative analysis of the relaxation strength indicates that the vibrational specific heat associated with both the lowest and the second lowest modes relaxes in the hypersonic range and all the rest, in the UHF range.
Resonance theory of acoustic reflection and transmission through a fluid layer
Authors: Fiorito Ralph , Überall Herbert
Published: October 2005

Sound transmission and reflection properties of a lossless fluid layer imbedded in another fluid are analyzed in terms of a resonance formalism similar to one that has been used in nuclear scattering theory, and more recently in acoustic scattering theory. Expressions for the transmission and reflection coefficients have been obtained which manifestly exhibit the resonance character of these functions. The formalism provides an explicit determination of the position, width, and strength of each individual resonance contribution, and links these resonance quantities to the material constants of the layer and its surroundings, thus indicating a novel way to determine these constants by a measurement of the acoustic transmission and/or reflection coefficients. Within the limits of the resonance approximation, the resonance positions may be obtained by solving a purely real characteristic equation, which constitutes a distinct computational advantage over the solution of the complex eigenvalue equation thought to be necessary for a loaded layer.
High-amplitude/low-frequency impulse calibration of microphones; a new method
Authors: Hunt Alan , Schomer Paul D.
Published: October 2005

This paper describes a new method to measure the peak amplitude response and the step-function decay (low-frequency response) of a microphone and its associated amplifiers. The requirements for the new method were that it be simple, inexpensive, and accurate. An acoustic ’’step function’’ would be an ideal source for testing the large-amplitude and low-frequency response of microphones, especially for measurements of impulsive noise. Unfortunately, a positive going acoustical step-function source is difficult to obtain. This method involves the use of a negative step-function input which is applied by enclosing a microphone inside a thin membrane which is inflated and then burst. The sudden decrease in pressure represents a negative going step-function input to the microphone. The peak output voltage produced by the microphone must be proportional to the initial static pressure within the membrane, and the return (decay) of the voltage output of the the microphone to zero directly represents the decay of the microphone and system. The low-frequency cutoff of the system is easily calculated from the time constant of the decay curve.
Auditory detection of a single gap in noise
Authors: Buunen T. J. F. , van Valkenburg D. A.
Published: October 2005

The detection threshold of a single gap in white noise was measured as a function of the gap duration. The result can be described with an auditory integration time of about 25 ms. This value is much larger than the 3–4 ms usually found in experiments on auditory temporal integration. The descrepancy shows that a system theoretical description of the detection of arbitrary amplitude changes in noise in terms of a modulation transfer function fails to explain the detection of a single gap.
Supplement to ’’How does a mynah bird imitate human speech?’’ [J. Acoust. Soc. Am. 55, 822–832 (1974)]
Authors: Klingholz F.
Published: October 2005

The first formant resonance (<1 kHz) in the imitation of human speech by birds seems not to be a tube resonance because the vocal tract length in a speaking parakeet is 3 cm and the resonant frequency of this tube would exceed 2 kHz and not remain under 1 kHz.
Attenuation of sound in highly concentrated suspensions and emulsions
Authors: Davis M. C.
Published: October 2005

The absorption of sound in emulsions and suspensions is due to viscous and thermal transport processes occurring at the interface of the nonhomogeneities, as well as to the intrinsic absorption in the materials comprising the system. For highly concentrated mixtures, multiple scattering is shown to play an important role. Following the arguments of Waterman and Truell [J. Math. Phys. 2, 512 (1961)], the behavior of the scattering medium may be specified explicitly in terms of the number of scatterers per unit volume, and the farfield amplitude f (ϑ) obtained for a single scatterer. The coefficients of f (ϑ) for a single scatterer have been calculated by Allegra and Hawley [J. Acoust. Soc. Am. 51, 1545 (1972)] for systems of solid and fluid particles suspended in a fluid media.
Simulation of space-random fields for solution of stochastic boundary-value problems
Authors: Elishakoff I.
Published: October 2005

The technique of digital simulation of Gaussian random fields (which are nonhomogeneous in space or are part of homogeneous random fields in space) is presented to a solution of stochastic boundary-value problems. The method consists of expanding the simulated field, with known mean and autocorrelation function, in series in terms of the structural ’’natural’’ mode shapes, and the Fourier coefficients of the truncated series are then simulated as random normal vectors. The method is applicable to static or dynamic stochastic two-point boundary-value problems in mechanics of solids.
Hysteretic structural vibrations under random load
Authors: Spanos P-T. D.
Published: October 2005

The nonstationary and stationary response of a lightly damped hysteretic structural system to white random load are considered. The hysteretic behavior is examined by using a model consisting of an infinite collection of elastoplastic elements, the yield loads of which are probabilistically specified. An equivalent linear system is constructed for the original hysteretic system. This system is used to obtain approximate solutions for the statistics of the response amplitude. The analytical results are used to perform a variety of parameter studies.
Comparison between different methods for impact testing of floors
Authors: Nordstedt J. R.
Published: October 2005

This project was intended to answer the question of whether measurements of impact noise on floors with a modified tapping machine, proposed by Dr. T. Schultz at Bolt Beranek and Newman Incorporated would yield results that better relate to subjective ratings than do those of the present ISO tapping machine. The studies were performed on two different floor constructions: one concrete slab and one wood joist. Out of this study it has not been possible to observe a significant difference in the ratings obtained with the two methods. However, the proposed method shows some advantages that facilitate impact noise testing in field and laboratory.
Underwater passive detection and spatial coherence testing
Authors: Bienvenu Georges
Published: October 2005

A problem in underwater passive listening is to detect a possible noise source in a given direction when background noise and other sources are present. It is assumed that the signal to be detected is perfectly coherent spatially. If the correlation matrix of the outputs of the sensors without the signal is known, it is possible to compute both an estimation and a detection test for the signal. When this matrix is unknown, which is the case in passive listening, an estimation of the signal can be obtained by an adaptive antenna thanks to the perfect coherence hypothesis. But in order to find a detection test, the shape of the spatial coherence matrix of the background noise must be known. Then the spectral density of this noise can be estimated even in the presence of the signal and of other coherent sources. A detection test using this estimation and the output of the adaptive antenna is proposed. Theoretical asymptotic results and simulations are presented.
On the classification of underwater acoustic signals. I. An environmentally adaptive approach
Authors: Deuser Larry M. , Middleton David
Published: October 2005

Environmental conditions and geometries have a pronounced effect upon signals received as scattered underwater acoustic waveforms. Information which may be processed to yield accurate assessments of the current environmental condition (and geometry) is important to the effective analysis and classification of these received signals. However, such environmental information is often ignored, or at best introduced indirectly, in degradation, through the usual formulation of composite hypothesis tests. Here, a methodology is developed which permits one to introduce estimates of the current environmental state (i.e., certain environments and object properties) in order to adapt the classification algorithm to the situation. The implications of such an environmentally adaptive approach are discussed, and general procedures for estimation, feature extraction, and feature selection are then presented. The pertinent features of analytic statistical–physical models of the medium provide useful guides, not only for the type of experiments needed to define these environmental states, but also for models, for deriving ’’artificial’’ data, or waveforms, by which the adaptive portions of the classification process can be studied and implemented.
Calculation of differential cross sections of sound geometrically reflected from impedance cylinders
Authors: George Jacob
Published: October 2005

We present a new method, identical in its predictions to the Luneburg–Kline method, for the calculation of differential cross sections of sound geometrically reflected from impedance cylinders in inverse integer powers of ka. The method employs Watson transformation and saddle-point integration techniques and allows easier evaluation of higher-order terms than the Luneburg–Kline method, as demonstrated. This is a crucial improvement, as it enables us to determine exactly the number of terms to be retained for the best value for cross section.
Acoustic target strengths of marine organisms
Authors: Penrose John D. , Kaye G. Thomas
Published: October 2005

The empirical relationships linking fish length and target strength for geometric region scattering, which have been developed by Love [J. Acoust. Soc. Am. 62, 1397–1403 (1977)], are shown to apply in the case of peak dorsal values, to some other marine organisms. Peak dorsal target strengths for squid, crab and penaeid prawns lie within 6 dB of the appropriate predictions due to Love. Some zooplankton values are within similar limits provided insonifying frequencies are sufficiently high to ensure that geometric region interactions occur. The target strength data reviewed show little overall frequency dependence in the geometric region, as would be expected if the scatterers were modeled as finite cylinders.
Scattering of elastic waves by randomly distributed and oriented scatterers
Authors: Varadan Vijay K.
Published: October 2005

We analyze the two-dimensional problem of multiple scattering by randomly distributed and oriented scatterers, and compare the results with those for the aligned scatterers. Waterman’s T-matrix approach in conjunction with the statistical averaging for both position and orientation are employed to obtain the phase velocity and attenuation due to geometric dispersion for a wide range of frequencies. Analytical expressions for the dispersion relation are also derived at low frequencies for both randomly distributed and oriented inclusions and cracks.
The absorption of sound by pine trees
Authors: Burns Stephen H.
Published: October 2005

This paper describes a study of the absorption of sound by pine trees. Swept frequency measurements were made with small boughs in a reverberant box. Tests for branch and needle resonances were also made. The observed absorption is comparable to the expected thermoviscous absorption in the boundary layer of air that surrounds the individual needles.
Forward scattering of underwater sound and its frequency dependence on the medium
Authors: Andrews R. S.
Published: October 2005

In the interference region of forward scattered sound by thermal inhomogeneities, there appears to exist a dominant thermal patch size for scattering at a given frequency. Several published results are examined and it is shown that over a decade of frequencies, the dominant (or effective) scattering patch size shows an f−5/2 frequency dependence. It also appears that a minimum patch size of approximately 1 cm is reached and that the frequency selectivity disappears after this value has been reached.
Statistical models of coupled dynamical systems and the transition from weak to strong coupling
Authors: Smith P. W.
Published: October 2005

The statistical model for steady-state response of a coupled dynamical system that is used in both room acoustics and statistical energy analysis is taken as the hypothesis. The model is defined by the fundamental equations of linear relation between the response energies of the subsystems and the input powers. Additional restrictions arise from the principle of reciprocity. The model is used to examine the effect of variable strength of coupling between the subsystems and the transition from weak to strong coupling. Results familiar from modal analysis [J. Acoust. Soc. Am. 63, 1081–1083 (1978)] are derived without introducing modal concepts.
A bispectral synthesizer
Authors: Sasaki Kimio , Sato Takuso
Published: October 2005

Methods for synthesizing a random signal with a preassigned power spectrum and the amplitude characteristics of a bispectrum are discussed from the standpoint of phase relationship with the bispectrum. A new approach is proposed, which uses a bandpass filter array, a multiplicatory array, and Gaussian white noise. Further, a random signal corresponding to the Japanese vowel [a] is synthesized by using the constructed device, according to the analyzed data of a voiced vowel [a]. The results of the experiments show the usefulness of the synthesizer.
Normal short-latency electrophysiological filtered click responses recorded from vertex and external auditory meatus
Authors: Coats A. C. , Martin J. L. , Kidder H. R.
Published: October 2005

We recorded normal electrophysiological responses to third-octave filtered clicks from external auditory meatus (EAM) and vertex electrodes referred to coupled earlobe electrodes (forehead ground). From both vertex and EAM, polarity-sensitive responses predominated at low frequencies and exhibited characteristics of both phase-locked neural responses (frequency-following response or FFR) and cochlear microphonics (CM). The FFR-like response predominated at the vertex site and the CM-like response predominated at EAM. At high frequencies, polarity-insensitive responses closely resembled rectangular-pulse click action potentials and brainstem evoked potentials, with clearly defined N1 and V peaks recorded from EAM and vertex, respectively. As frequency was lowered, the N1 and V peak latencies increased, the peaks broadened, and the latency-intensity curves steepened with greater prolongation occurring at lower click intensities. Lowering click frequency also shortened the N1–V interval and caused the plot of N1–V interval versus click intensity to become steeper. Plots of polarity-insensitive response amplitudes and thresholds against frequency revealed a high-frequency bias for both N1 and V, but the V ’’frequency response’’ was flatter. A possible explanation of the shortened N1–V interval at low click frequencies based on this flatter V ’’frequency response’’ is presented.
Permeability of fluid flow through hair cell cilia
Authors: Frommer Glenn H. , Steele Charles R.
Published: October 2005

Models (∠400×) were constructed of the one row of inner hair cell cilia bundles and the three row array of ’’w’’ shaped outer hair cell cilia bundles found in the mammalian cochlea. These were placed between parallel plates simulating the under surface of the tectorial membrane and the upper surface of the reticular lamina. The pressure required to produce a given volume of flow through the obstacles was measured. For low flow rate, the behavior is linear, i.e., the ratio of flow rate to pressure drop (permeability) is independent of flow rate. For higher flow rates (Reynold’s number Λ?0.08) the behavior is nonlinear, characterized by an increase in the effective permeability to a maximum at Λ∠10 and an asymmetry in the flow through the OHC cilia bundles. Interpretation in terms of cochlear function is beyond the scope of the present work. A very tentative estimate places the onset of nonlinearity at around 80 dB SPL, so the flow around the cilia bundles in the cochlea is linear for normal intensity levels.
Stop consonant place perception with single-formant stimuli: Evidence for the role of the front-cavity resonance
Authors: Kuhn G. M.
Published: October 2005

The third formant and the second formant were found on average to cue the place of articulation of intervocalic stop consonants equally well when the stop consonants occurred before the vowel /i/. This result and others provide some support for the notion that the fundamental resonance of the front cavity plays an important role in the perception of the phonetic dimension of place of articulation.
Coherence estimates for signals propagated through acoustic channels with multiple paths
Authors: Jobst W. , Zabalgogeazcoa X.
Published: October 2005

Theoretical estimates of space, time, and frequency coherence are obtained for a sound field generated by a moving source and observed at a stationary array of sensors. It is shown that spatial coherence depends principally upon the spread of ray-path-arrival angles at the receiving sensors and on the orientation of the receiving array to the sound field. Temporal coherence depends upon the ray-path angle spread at the source and on source motion. Oscillatory source motion introduces frequency modulation of the transmitted signal with sideband levels related to projector displacement amplitude. Frequency coherence depends upon the time spread between arrivals which propagate over different acoustic paths. Examples of theoretical coherence functions are presented for multipath channels of interest in underwater acoustics.