bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic wide-bandwidth acoustic form-function determination
Authors: Dardy H. D. , Bucaro J. A. , Schuetz L. S. , Dragonette L. R.
Published: October 2005

The use of near-real-time digital signal processing to obtain acoustic data on the scattered form function of an object is considered. Modifications inherent in the analog to digital conversion process are found not to alter the analog data representation. The experimentally obtained backscattered form function for an ’’effective’’ infinite aluminum cylinder is presented for the region 4?ka?21.
Reflectivity of the ocean bottom at low frequency
Authors: Fryer Gerard J.
Published: October 2005

The theoretical reflectivity of the ocean bottom estimated from a model composed of fluid sediment layers is misleading because the effects of shear propagation are ignored. Reflectivity computations which include the effects of shear may be made using Thomson–Haskell matrix theory. The delta-matrix extension of this theory provides a method for computation of plane-wave reflectivity of a viscoelastic layered ocean bottom at the frequencies of interest in acoustics. The results from a hypothetical turbidite section show that when elastic parameters vary continuously with depth, conversion of compressional to shear energy is unimportant at frequencies above 20 Hz. However, at discontinuities, conversion to shear does occur. This strongly affects the reflectivity at all frequencies, except at small grazing angles and near-normal incidence.
Frequency discrimination for pulsed versus modulated tones
Authors: Fastl Hugo
Published: October 2005

Estimates of frequency discrimination for pulsed versus modulated tones were obtained by 11 observers at 350, 500, 1000, 2000, 4000, and 8000 Hz. At low frequencies, frequency DL’s are larger for modulated than for pulsed tones; at 8000 Hz the contrary was found. Frequency DL’s (difference limens) determined by different methods and procedures differed by a factor up to four; extreme individual frequency DL’s, however, by a factor up to 27.
Observations of the propagation of very short ultrasonic pulses and their reflection by small targets
Authors: Weight J. P. , Hayman A. J.
Published: October 2005

The field of a circular ultrasonic transducer emitting a single-cycle pulse into water has been observed using a specially constructed small (150 μm) wide-band receiving probe and a compact stroboscopic schlieren system. The theoretically predicted plane-wave and diffracted edge-wave components of the field have been resolved. Good agreement with the theory for a pistonlike source is obtained, except in a region less than 1.5 transducer radii from the transducer. The output of the transducer used in the transmit–receive mode to detect small targets has been measured and the results are in accord with a time-domain principle of reciprocity between transmission and reception. Implications of the results for field plotting and for the location and characterization of small targets are considered.
A novel approach to digital beamforming
Authors: Pridham Roger G. , Mucci Ronald A.
Published: October 2005

For many sonar applications, the sensor outputs of a hydrophone array are sampled at a rate significantly higher than that required for waveform reconstruction when digital beamforming is used. The reason for this is that the number of synchronous, or ’’natural,’’ beampointing directions is proportional to the beamformer input rate. This paper presents an implementation of a digital beamformer that achieves the desired synchronous beams while minimizing the sensor channel sampling rate requirement. The technique employs zero padding of sensor data followed by digital interpolation filters to achieve vernier beamformer delays. Interpolation filtering can be done either at the beamformer input or output to minimize processing requirements. The resulting structure realizes a hardware savings since both A/D converter and cable bandwith requirements can be traded off against digital processing complexity to achieve an optimal partitioning.
Temporal integration of tone glides
Authors: Collins M. Jane , Cullen John K.
Published: October 2005

Temporal integration of rising and falling tone glides against a 50–2800-Hz background of noise at a sound pressure level of 60 dB re 20 μPa was studied in two experiments. Glides were in the frequency ranges 200–700 Hz and 1200–1700 Hz for durations of 5–120 ms. Results indicate an asymmetry in the detectability of rising and falling glides of short duration, with rising glides detected at lower signal intensities in both frequency ranges. These effects are discussed in terms of differences in pattern of frequency analysis of identical, but temporally reversed, waveforms.
Auditory handicap of hearing impairment and the limited benefit of hearing aids
Authors: Plomp Reinier
Published: October 2005

The aim of this article is to promote a better understanding of hearing impairment as a communicative handicap, primarily in noisy environments, and to explain by means of a quantitative model the essentially limited applicability of hearing aids. After data on the prevalence of hearing impairment and of auditory handicap have been reviewed, it is explained that every hearing loss for speech can be interpreted as the sum of a loss class A (attenuation), characterized by a reduction of the levels of both speech signal and noise, and a loss D (distortion), comparable with a decrease in speech-to-noise ratio. On the average, the hearing loss of class D (hearing loss in noise) appears to be about one-third (in decibels) of the total hearing loss (A+D, hearing loss in quiet). A hearing aid can compensate for class-A hearing losses, giving difficulties primarily in quiet, but not for class-D hearing losses, giving difficulties primarily in noise. The latter class represents the first stage of auditory handicap, beginning at an average hearing loss of about 24 dB.
Auditory thresholds and kanamycin-induced hearing loss in the guinea pig assessed by a positive reinforcement procedure
Authors: Prosen Cynthia A. , Petersen Michael R. , Moody David B. , Stebbins William C.
Published: October 2005

Absolute thresholds from 125 Hz to 52 kHz ere determined for six guinea pigs trained by a positive reinforcement method. Four to five hundred trials were conducted during daily testing sessions and little between- or within-subject variability was found. Two of the six animals were subsequently treated with kanamycin and the development of a hearing loss for the high frequencies was followed. Loss of outer and to a lesser extent inner hair cells was well correlated with the threshold shift observed. Contrary to the experience of previous investigators, this operant training procedure has proved as efficient as that for other species of experimental animals, such as the monkey and the chinchilla. It holds excellent promise for future auditory behavioral work with the guinea pig.
Difference limens for formant frequencies of steady-state and consonant-bound vowels
Authors: Mermelstein Paul
Published: October 2005

Difference limens (DL) of formant frequencies were measured for two steady-state vowels and the same vowels in symmetric stop-consonant contexts. The stimuli were generated using a computer-programmed synthesizer, and the formant-frequency parameters were adjusted to be steady or symmetric transition functions around the temporal center of the syllable. The DL for the time-varying consonant–vowel–consonant (CVC) stimuli were found to be significantly larger than those for the steady-state vowels. In some cases the DL for the second formant was found to be larger in the direction of expected formant shift due to consonantal coarticulation than in the reverse direction. For CV or VC stimuli the increase in vowel-formant DL is reduced. The difference in DL values in and out of context has, at least partially, an auditory origin. However, the phonetic decoding of the CVC stimuli may also contribute to the loss of vowel-quality information.
Speech interference level as a predictor of face-to-face communication in noise
Authors: Waltzman Susan B. , Levitt Harry
Published: October 2005

An experiment was performed to check the validity of the distance versus speech interference level (SIL) curves for face-to-face communication in noise [Beranek, Proc. IRE 35, 880–890 (1947); Webster, Proc. Natl. Conf. Noise as a Public Health Hazard (1969)]. Monosyllabic word intelligibility was measured both with and without visual cues at talker-to-listener distances of 2, 4, and 8 ft, and at speech interference levels of 65, 75, and 85 dB. The distance-versus-SIL curves were found to be reasonably consistent with the intelligibility data when no visual cues were available, but substantially underestimated tolerable speech interference levels for barely reliable communication with visual cues. Another major source of error was the difference between the observed rate of attenuation with distance of the speech signal and the idealized, free-field rate of attenuation assumed for the distance-versus-SIL curves. Errors resulting from this assumption were found to be consequential only at the larger talker-to-listener distances. Other important factors which affected the accuracy of the curves were the total speech power of the talker, the shape of the speech power spectrum, and the rate at which the talker raises his/her voice in noise.
A unidirectional transducer with three electrode groups for Lamb- wave devices
Authors: Toda Kohji , Shinoda Yoshiaki
Published: October 2005

The theory and design of a new type of unidirectional transducer for Lamb-wave devices are described. The transducer consists of three electrode groups. One of them is used as a common earth electrode and is on the bottom surface. The others are interdigital electrode groups on the top surface. The unidirectionality of this transducer can be realized under the phase condition of x+y=1/2, where 2πx is the phase difference arising from the geometry and 2πy is the phase difference of two electrical signals applied to the transducer.
Additive masking effects of noise bands of different levels
Authors: Small Arnold M. , Tyler Richard S.
Published: October 2005

The simultaneous, ipsilateral masking of a sinusoid of frequency fs (600–860 Hz), located near the common cutoff frequency fc (750 Hz) of a low-pass and high-pass noise was examined as a function of the level of each of the bands. The pressure spectrum level of the high-frequency band Lh ranged from 5–50 dB re 20 μPa in 15-dB steps and the level of the low-frequency band L1 was from 0–24 dB down from each of these levels. The computer-synthesized noise provided a spectral step function transition at fc. The data generated by each of the three listeners in the 4IFC adaptive task was virtually identical. When fs≫fc masking was determined simply by Lh, and when fs≪fc masking was generally equal to but sometimes greater than that attributable solely to L1. When fs?fc, masking was intermediate relative to the asymptotic values just mentioned. The data are consistent with a conceptual auditory filter which has a Gaussian shape, an equivalent rectangular width of 110 Hz (for the limited frequency range considered), and a center frequency which is shifted away from the high-band noise relative to fs. These characteristics are not dependent on Lh although the asymmetry of filter positioning is weakly related to L1−Lh. The data are also consistent with a model which postulates that masking is a function of the simple sum of the masker power derived from the low-band, high-band, and internal noise appearing at the filter output.
The distributed response of complex branching duct networks
Authors: Fredberg J. J. , Moore J. A.
Published: October 2005

We describe an efficient method for simulating the distributed response of complex asymmetrically branching networks which satisfy requirements of network self-consistency. Individual tree links may be dispersive and lossy. As a case in point we simulate the response of the human lung, and characterize the variations in pressure with frequency, path, and position. The effects of tree asymmetry are found to be significant above 100 Hz in the air-filled lung.
Infrasound and sound: Differentiation of their psychophysiological effects through use of genetically deaf animals
Authors: Busnel R.-G. , Lehmann A.-G.
Published: October 2005

The effects of steady-state acoustic stimulation on resistance to fatigue as shown by reduction of swimming time was studied on three sublines of mice, one of which is genetically deaf. High frequencies (500–10 000 Hz) reduce swimming time from 25% to 50% in mice with normal hearing at a 60–80-dB threshold, but have no effect on deaf mice. Low frequencies and infrasounds (6–50 Hz) reduce swimming time in all mice similarly, even deaf animals, but the threshold is higher (160–115 dB). The use of genetically deaf animals therefore permits elimination of the auditory component; differentiation of the effects of air-born sound from those of mechanical vibrations are thus possible.
Theory of elastic resonance excitation by sound scattering
Authors: Flax L. , Dragonette L. R. , Überall H.
Published: October 2005

The resonance formalism of nuclear-reaction theory is applied to the problem of sound scattering from submerged elastic bodies (illustrated here by circular cylinders and spheres). It is demonstrated that the strongly fluctuating behavior of, e.g., the backscattering cross section is caused by a superposition of generally narrow resonances in the individual normal modes (partial waves), which move up in frequency from one partial wave to the next, corresponding to a series of creeping waves (’’Regge poles’’), and which are superimposed on a background of rigid-body (potential) scattering. This fact, together with a resonance representation of the elastic field in the interior, indicates that the elastic body is relatively impenetrable to the incident wave except in the vicinity of the resonances, which occur at the eigenfrequencies of the elastic vibrations of the body. Various types of interference between resonance and background are analyzed, and the phase of the partial wave is shown to undergo a jump of π at each resonance. Decay times (ringing) of the excited resonances are found to depend inversely on their width, and the appearance of nulls in the scattering angular distribution at certain resonances is related to the cross section of the rigid body.
Approximations to distant shipping noise statistics
Authors: Mikhalevsky Peter N. , Dyer Ira
Published: October 2005

Distant shipping noise modeled by multiple phase-random line components has a probability density and statistics easy to state in generality but difficult to compute in particular. To obtain numerical results with reasonable effort, previous computations have been based on Gaussian approximations to the densities. Here we show that an Edgeworth-series approximation to the density greatly improves the quality of the result, without adding much to the computational effort. Also, to justify adoption of the Edgeworth series, and to further develop the theoretical framework for distant shipping noise, exact analytical results are presented for several new cases of multiple line components.
Effects of density gradients on bottom reflection loss for a class of marine sediments
Authors: Rutherford Steven R. , Hawker Kenneth E.
Published: October 2005

The sensitivity of bottom reflection loss to a density gradient is examined within the context of a physically meaningful model consisting of a fluid sediment layer having depth-dependent density and sound speed overlying a substrate having solid properties. The bottom grazing-angle range is divided into two regions, the low-angle and the high-angle regions. In the low-angle region sediment sound-speed gradients refract incident energy upward before it encounters the substrate. In the high-grazing-angle region, energy impinges on the substrate. Through the use of a numerical plane-wave reflection coefficient model it is shown that the effect of a density gradient on low-angle bottom loss is small. An expression indicating this effect is derived and is shown to agree with numerical bottom-loss calculations. The high-angle bottom loss is more influenced by a density gradient because of the impedance changes at the sediment–substrate interface which accompany a density gradient. It is shown that introduction of density gradient of 0.002 g/cm3/m can cause the high-angle bottom loss to change on the average by 12.5%, 7%, and 3% in 100-m clay, silt, and sand layers, respectively.
Bistatic surface scattering strength measured at short wavelengths
Authors: Zornig John G.
Published: October 2005

A series of measurements of the scattering strength of wind-driven water surfaces at short wavelengths (circa 1 mm) have been performed. Bistatic azimuthal configurations ranging from 0° (backscatter) to 180° (specular direction) were used at three grazing angles and two conditions of roughness. Orientations with respect to the wind over a range of 180° were also studied. The experiments were conducted with short, relatively narrow-band probing signals under computer control. The data were converted to scattering strength using a flat-surface reference and a computed compensation for beam patterns and source and receiver time gating. The results of these measurements indicate that wind direction is an important factor in determining reverberation from the surface. Wind speed, hence roughness was confirmed to be an equally important factor, but Rayleigh parameter, an often used scalar index of effective roughness, was shown to be insufficient to predict reverberation. At short wavelengths, scattering strength was found to be insensitive to small changes in wavelength as expected. Backscatter strengths measured at 8.3 m/s at crosswind were found to agree closely with a relation proposed by Marsh [J. Acoust. Soc. Am. 35, 240–244 (1963)] relating backscattering strength to grazing angle. No satisfactory predictive theory, however, seems to be available for the general case of bistatic scattering.
Collinear interaction of noise with a finite-amplitude tone
Authors: Webster Don A. , Blackstock David T.
Published: October 2005

The interaction between a low-level band of noise and a finite-amplitude tone has been measured in air in a plane progressive wave tube. Noise bands generally 1–3 octaves wide with center frequencies in the range 0.7–1.2 kHz were used. At the source the tone SPL was in the range 140–151 dB (re 20 μPa); the frequency was either within the noise band or somewhat above. The data show the following. When the tone is absent, the noise propagates as a small-signal wave. When the tone is turned on, however, a strong modulation takes place. After a propagation distance of only a few meters, not necessarily beyond the point of shock formation for the tone, the noise spectrum extends many octaves above the original noise band and, moreover, becomes nearly flat. The energy required to extend the noise apparently comes from the tone and its harmonics, not the original noise band. Theoretical predictions have also been obtained. A computer algorithm based on the Earnshaw solution, with corrections for tube wall absorption added, was used. The input waveform of the noise was constructed from the measured source power spectrum, the components of which were assigned random phase. The computed results agree well with the experimental data.
Frequency dependence of ultrasonic absorption in mammalian testis
Authors: Goss S. A. , Frizzell L. A. , Dunn F.
Published: October 2005

The earlier report that the frequency dependence of ultrasonic absorption of mammalian testis mimicked a single relaxation process is explained as an effect of ultrasonic beam width upon the transient thermoelectric technique. More detailed measurements show that the frequency dependence of the ultrasonic absorption in testis is much the same as the attenuation in other soft tissues, viz., α proportional to f1.1. The earlier finding that testis exhibits an ultrasonic absorption coeffieient significantly lower than reported for other tissues is confirmed.
Localization of pure tones by Old World monkeys
Authors: Brown C. H. , Beecher M. D. , Moody D. B. , Stebbins W. C.
Published: October 2005

The acuity of auditory localization in Old World monkeys (Macaca) was psychophysically determined for nine sinusoidal stimuli ranging from 250 Hz to 16 kHz. Monkeys were trained through positive reinforcement operant conditioning procedures to contact a response disk (observing response) initiating a repetitive series of 300-ms pure tones presented from 0° azimuth (standard location). At random intervals the stimulus changed from the standard to one of four comparison locations. The monkey reported the change in azimuth by releasing the response disk. The acuity of localization was assessed through the method of constant stimuli under free-field conditions in an anechoic chamber. The results were consistent with the classic duplex theory of auditory localization. Thresholds for the detection of a change in space decreased from 21.8° at 250 Hz to 3.5° at 1000 Hz, and corresponded to a constant 11° interaural phase difference. The localization of high-frequency tones (above 1000 Hz) was highly variable across frequencies and between subjects, ranging from less than 3° to greater than 20°, and displayed the basic attributes associated with the detection of interaural differences in sound pressure level.
Internal friction in rocks
Authors: Mason W. P. , Marfurt K. J. , Beshers D. N. , Kuo J. T.
Published: October 2005

This paper intends to show that the low-amplitude effects, in particular the attenuation proportional to the frequency from very low frequencies up to the kilohertz range, are connected with the motion of dislocations in cracks. The measurements have been made of the resonant frequencies and the internal friction of spherical rock speciments, including Solenhofen limestone, Indiana limestone, Westerley Granite, Friedensville sphalerite, galena, magnetite, and olivine of small grain sizes. The different types of stresses are thus easily determined through the various modes of motion. On the basis of dislocation motion in cracks, it is shown that the ratio of the radial Q to the torsional Q is about 0.8 and is nearly independent of the crystal structure. This result is in agreement with the measurements, which vary from about 0.6 to 0.9. From longitudinal and torsional measurements of cylinders, the torsional Q’s are nearly twice those for the longitudinal mode. The model used also agrees with the variation of velocity and Q with the external pressure.
Three-level coincidence-correlator detectors
Authors: Shin Jung Gil , Kassam Saleem A.
Published: October 2005

Nonparametric three-level coincidence-correlator (CC) detectors are considered for the detection of random signals in noise in two-input systems. Based on the maximum-efficacy criterion the structure of the optimum detector is obtained, together with the corresponding efficacy. The results allow the evaluation of practical detection schemes in this class of detectors, in terms of their performance relative to the constrained optimum and to the unconstrained optimum three-level CC detector. Some specific three-level CC detectors which are simple extensions of the polarity coincidence correlator are examined and a numerical comparison is made for Gaussian noise.
Measurement of acoustic reflection from an obstruction in a pipe with flow
Authors: Johnston J. P. , Schmidt W. E.
Published: October 2005

An alternative to the impedance tube method is proposed for measurement of acoustic reflection coefficients. The new method has the advantage that it may be used to measure the reflection and transmission coefficients for plane sound waves incident on an obstruction (orifice, nozzle, valve, elbow, etc.) in a long, straight, hard-walled duct in the presence of flow through the duct. It employs the time-delayed cross correlation between an acoustic signal source and the output signals from microphones located ahead of, and behind, the obstruction. The method is demonstrated for several situations, including the case of flow through square-edged orifices where Mach number in the jet downstream of one orifice was as high as 0.73.
Visual-field displacements in human beings evoked by acoustical transients
Authors: Parker D. E. , Tubbs R. L. , Littlefield V. M.
Published: October 2005

Sixty-two of 133 subjects reported visual-field displacements when they were exposed to intense (125 dB SPL) repetitive audiofrequency transients. This phenomenon was investigated in three experiments. Frequency (100–5000 Hz) was varied in experiment I; repetition rate (0.5/s–6.0/s) was varied in experiment II; acoustical transient onset/offset time (0.2–25 ms) was examined in experiment III. The results of these three experiments indicated that the largest proportion of displacement reports and the largest perceived motion magnitudes followed stimulation in the 500- to 1000-Hz frequency range at repetition rates of about 1/s. Response differences as a function of onset/offset time were erratic. The pattern of results obtained in this study, in conjunction with the results of previous investigations of acoustical vestibular stimulation, suggests that the visual-field displacements resulted from stimulation of the receptors of the vestibular system. These experiments may account for discrepancies in reports of infrasound-evoked eye movements. Finally, it is suggested that intense sound exposure may damage the vestibular receptors with or without concomitant damage to the auditory portion of the membranous labyrinth.
High-precision phase-velocity measurements utilizing a continuous-wave feedback technique
Authors: Telschow K. L. , Stasiak J. W.
Published: October 2005

A common technique for measuring the phase velocity of an acoustic wave under free-field conditions has been a determination of the phase shift between transmitted and received signals. We report here a modification of this scheme involving the addition of a feedback loop which increases the precision of the absolute velocity measurement. In addition, this technique provides automatic tracking of relative velocity variations with high precision and noise immunity. Measurements illustrating this technique for acoustic waves in thin superfluid helium films are presented with precisions of better than 80 ppm obtained.
Poincaré–Lighthill–Kuo method and wave propagation in an inhomogeneous medium
Authors: Shivamoggi Bhimsen K.
Published: October 2005

The following note uses the Poincaré–Lighthill–Kuo method to treat the general problem of wave propagation in an inhomogeneous medium through the model example (due to Lesser [J. Acoust. Soc. Am. 47, 1297 (1969)] utt−[1+εa (x,t)]2uxx =0, ε≪1; u (x,0) =f (x), ut(x,0) =g (x). It is found that (1) the uniformly valid first-order solution for wave propagation in an inhomogeneous medium is simply the solution corresponding to the wave propagation in a homogeneous medium with the respective characteristic replaced by the characteristic calculated by including the first-order inhomogeneities in the medium, and (2) for the case a (x,t) ≡1, the first-order solution turns out to be the exact solution itself.
General relationships between ultrasonic attenuation and dispersion
Authors: O’Donnell M. , Jaynes E. T. , Miller J. G.
Published: October 2005

General relationships between the ultrasonic attenuation and dispersion are presented. The validity of these nonlocal relationships hinges only on the properties of causality and linearity, and does not depend upon details of the mechanism responsible for the attenuation and dispersion. Approximate, nearly local relationships are presented and are demonstrated to predict accurately the ultrasonic dispersion in solutions of hemoglobin from the resuts of attenuation measurements.
Merged seawater sound-speed equations
Authors: Lovett Jack R.
Published: October 2005

Recent checks of published seawater sound-speed measurements indicate that the Del Grosso–Mader data provide the best relationships with temperature and salinity, while the Wilson data have the preferred pressure dependence. Possible error sources in the original measurements are discussed. Anderson’s pressure-dependence, based on the Wilson data, is applied to Del Grosso’s equation and to the Del Grosso-Mader data, resulting in three new equations. The third and simplest equation seems preferable for most applications. The new equations agree well with Anderson in comparison with acoustically determined convergence-zone ranges at sea.
Theory of nonlinear electroacoustics of dielectric, piezoelectric, and pyroelectric crystals
Authors: Nelson D. F.
Published: October 2005

Based on a fully electrodynamic Lagrangian theory of elastic dielectrics, a completely deductive derivation of the dynamical equations and constitutive relations for elastic, electric, and electroelastic phenomena is presented. The equations apply to crystals of arbitrary symmetry, structural complexity, and nonlinearity. These include pyroelectrics as well as dielectrics and piezoelectrics. Emphasis is placed on the lowest order nonlinearities, that is, ones depending either bilinearly or quadratically on the elastic and electric variables. A relation between the electrostriction tensor and the low-frequency limit of the elasto-optic tensor, different from any previous relation in the literature, is derived and discussed.
Speed of sound in NaCl, MgCl2, Na2SO4, and MgSO4 aqueous solutions as functions of concentration, temperature, and pressure
Authors: Chen Chen-Tung , Chen Lee-Sea , Millero Frank J.
Published: October 2005

The speeds of sound in aqueous solutions of NaCl, MgCl2, Na2SO4, and MgSO4 have been measured relative to pure water from 0 to 1 molal ionic strength, 0° to 55 ° C, and 0 to 1000 bar applied pressure. The 1-atm results have been fitted to polynomial equations of concentration and temperature with standard deviations of about 0.1 m/s, U0−UW0=am+bm3/2+cm2 where U0 and UW0 are the 1-atm sound speeds in solution and in pure water, respectively; m is molality; and a,b, and c are temperature-dependent parameters. The effect of pressure on the relative speeds of sound has been fitted to equations of the form (UP−UWP)−(U0−UW0) =dm+em3/2+fm2, where UP and UWP are the sound speeds of the solution and water at applied pressure P and d,e, and f are temperature- and pressure-dependent parameters. The standard deviations of the least-squares fits are within 0.12 m/s for all the salts.
Effect of sound-absorptive facings on partition airborne-sound transmission loss
Authors: Brown Steven M. , Niedzielski Joseph , Spalding G. Robert
Published: October 2005

Laboratory measurements of the improvement of partition airborne-sound transmission loss in the presence of sound-absorptive partition facings are presented. For a double-leaf partition of 1/2-in.-thick gypsum board on 2×4-in. studs, the application of such facings has led to improvements in transmission loss in excess of 10 dB in the 1/3-octave bands above 1 kHz. Corresponding, but smaller, improvements have been measured at lower frequencies.
Human response to house vibrations caused by sonic booms or air blasts
Authors: Schomer Paul D.
Published: October 2005

Descriptions of the effects of sonic booms or air blasts by observers in buildings have included such statements as ’’noticeable vibrations’’ in addition to phrases such as ’’the house rattles,’’ ’’the windows rattle,’’ or ’’bric-à-brac rattles.’’ Analysis of studies of human response to vibrations, vibration complaints in the Toronto area, special tests by Kryter at Edwards Air Force Base, and laboratory studies of human response to sonic booms show that perceived vibration is not normally a factor that contributes significantly to human response to airborne, large-amplitude impulse noise. Rather, human response is solely the result of the impulse noise itself and of audible noise due to induced radiation from vibrating surfaces.
Radiation from a submerged elastic shell defined by nonconcentric cylinders
Authors: Shaw Richard Paul
Published: October 2005

The acoustic radiation from an elastic cylindrical shell defined by nonconcentric cylindrical surfaces and submerged in an acoustic fluid is studied. The driving mechanism is a time-harmonic internal pressure. In particular, the influence of the nonconcentricity parameter δ on the resulting radiation field is examined. The solution is obtained by means of an expansion in powers of this parameter about the concentric solution, δ=0. Each order of solution is solved in closed form by means of boundary integral equation methods. Results are given for the zeroth and first-order solutions and it is seen that a jth driving mode will introduce nearest neighbor (j−1 and j+1) modes in the first-order solution.
Intensity perception. IX. Effect of a fixed standard on resolution in identification
Authors: Berliner J. E. , Durlach N. I. , Braida L. D.
Published: October 2005

This note reports some measurements of the changes in identification performance that result from presenting a fixed standard before each trial. These measurements indicate that the presence of the standard improves perfromance for test stimuli in the vicinity of the standard, except when the standard is near the extremes of the stimulus range.
Electret transducer equations by Lagrange’s equation
Authors: Hawley Melville S. , Romanow Frank F.
Published: October 2005

The equations of motion of the electret foil transducer are derived by applying Lagrange’s equation to the total electrical and mechanical energies of the transducer system. The resulting equations apply for the operation of the transducer both as a sound source and as a sound pickup. An expression for the induced static surface-charge density on the back plate is obtained from these equations modified for the quiescent state. An electrical circuit model of the transducer is given for linear operation.
Backscattering from discrete targets at 87.5 kHz
Authors: Kaye G. T.
Published: October 2005

Reverberation structure has been observed from research platform FLIP with a narrowbeam, high-resolution 87.5-kHz echo sounder. The system resolution indicates that the backscattering can be resolved as discrete targets. Targets strengths and scatterer densities suggest that the scatterers are probably fish and possibly squid and siphonophores. Although zooplankton may be observed acoustically if there are sufficient animal densities, they will not be the dominant scatterers below the mixed layer for small insonified volumes. A midnight migration was observed that corresponded with the passage of rain squalls.
Resonant acoustic scattering by swimbladder-bearing fisha)
Authors: Love Richard H.
Published: October 2005

A new model of swimbladder-bearing fish has been developed in order to provide improved predictions of the resonance frequency and acoustic cross section of such a fish. The model consists of a small spherical shell in water, enclosing an air cavity which supports a surface tension. The shell is a viscous, heat-conducting Newtonian fluid, with the physical properties of fish flesh. A comparison of the results obtained with the new model to experimental data indicates that the new model constitutes a definite improvement over previous models. The new model can predict the high values of damping and elevated resonance frequencies that previous models could not. The model appears to be most accurate for fish in which tension in the swimbladder wall has a minor effect on resonant scattering. This includes the fish which are of interest in studies of volume reverberation, and the new model should therefore be of considerable value in such studies.
Propagation of Atlantic bottlenose dolphin echolocation signals
Authors: Au Whitlow W. L. , Floyd Robert W. , Haun Jeffrey E.
Published: October 2005

The propagational characteristics of high-frequency echolocation signals (peak energies above 100 kHz) of the Atlantic bottlenose dolphin Tursiops truncatus in open water were determined by a series of measurements conducted while the animal performed a target-detection task. The animal was trained to station in a ’’chin-cup’’ device so that the vertical beam pattern of the projected echolocation signals could be measured with a vertical array of hydrophones and the horizontal beam pattern could be measured with a horizontal array. The projected echolocation signals as a function of distance from the animal out to 2 m were measured with a horizontal array of hydrophones placed directly in front of the animal. These measurements were used to study the relationship of the signals in the near and far fields of the animal sound source. The relationship of the signals measured with a contact hydrophone placed on the animal’s rostrum and on the melon with the signals measured at 1 m and at the target was also studied. It was found that the 3-dB broadband beamwidth was approximately 10° in both the horizontal and vertical planes. The major axis of the vertical beam was directed at an agnle of 20° above the plane defined by the animal’s teeth. It was also found that the acoustic pressure of the echolocation signals began to satisfy the farfield criterion of decaying inversely with distance at approximately 0.5–0.6 m from the tip of the animal’s rostrum.
Acoustic scattering from locally homogeneous turbulence
Authors: Ramsey Vernon W. , Peterson Allen M.
Published: October 2005

From the basic equations of fluid dynamics, an equation is derived for acoustic scattering from the velocity and temperature fields of a drifting blob of air turbulence. With the aid of the Born approximation, the equation is then solved for scattering from the mean and turbulent portions of both fields, and the time autocorrelation and power spectral density of the received signal are calculated. The mean velocity and temperature fields, as well as the corresponding turbulence intensity distributions, are allowed to be spatially nonuniform. The turbulent fields are required to be only locally homogeneous and, because of the nonzero drift, locally stationary. It is shown that the common practice of representing antenna patterns by either truncating the flow or tapering the strength of the flow is, at least in the case of the transmitting pattern, not a bad approximation. Spectral broadening of the received signal due to convection of the small scattering eddies by macroeddies and by the mean flow is modeled, and the broadening by macroeddy convection is seen to render negligible the broadening which arises from the drift of the target flow through the antenna beam. The analysis reveals that only for target flows having a high degree of spatial uniformity and/or symmetry does the received positive-frequency power spectral density turn out to be symmetrical about a center frequency.
Response of fibers in the cat’s auditory nerve to the cubic difference tone
Authors: Buunen T. J. F. , Rhode W. S.
Published: October 2005

Recordings were made of discharges in single fibers of the cat’s auditory nerve using single-tone and two-tone signals of varying frequency. The frequency of the single tone was varied stepwise from the fiber’s best frequency to about 1.7 times this value. One component of the two-tone signal was varied in exactly the same manner while the frequency of the other was increased in such a way that the frequency of the cubic difference tone (CDT, 2f1−f2) generated within the auditory system was kept constant at the fiber’s best frequency. Responses in terms of discharge rate and period histograms were collected for both signals. The difference in spike rate between the response to the single tone and to the two tones could be ascribed to the CDT and was used to estimate the CDT level as a function of the signal level and frequency. It turned out that the CDT level relative to that of the primaries is about 15 dB smaller for frequencies beyond 10 kHz than for lower frequencies, and slighly decreasing for an increasing stimulus level. Period histograms of responses to CDTs of frequencies below 4 kHz made it possible to estimate CDT phase as a function of the frequencies and the level of the two generating tones. The intensity of the tones had no effect on the CDT phase. The varying frequency separation produced shifts in the CDT phase of several hundred degrees if its frequency was above 2.5 kHz. For lower frequencies the shifts were maller, and varied considerably between different preparations. The phase estimated from period histograms for acoustic tones and for CDTs of varying frequency turned out to change in an identical manner. This shows that the CDT must be subject to the same delays or phase shifts as the traveling wave in the cochlea produced by an acoustic tone.
Statistical grouping of acoustic reflection profiles
Authors: Milligan S. D. , LeBlanc L. R. , Middleton F. H.
Published: October 2005

A new technique is presented for the study of seismic reflection profiles. Previous investigations of the reflection of sound from marine sediments have been restricted to the determination of a specular reflection coefficient. This study is based upon the hypothesis that the entire reflected waveform, rather than just the amplitude, contains valuable information on the classification and characteristics of these sediments. The multivariate statistics technique of principal component analysis is proposed for analyzing the variability in the shape and amplitude of the reflected waveform. The results of this analysis are used in conjunction with an improved cluster analysis program to produce maps of sediment distributions for a section of Narragansett Bay, Rhode Island. The groupings produced are in basic agreement with previous studies of the area. Preliminary regression equations are presented for converting the principal components to percentages of sand, silt, and clay.
Measurements and analysis of farfield scattering from a prolate spheroid
Authors: Bayliss A. , Maestrello L.
Published: October 2005

The farfield acoustic scattering by a prolate spheroid with axial point sources near the tip of the body was measured. Data were taken for ka between 10 and 160, where a is the semimajor axis of the spheroid. Comparisons were made with numerical results obtained by an integral equation based on the simple-source method, with appropriate coordinate stretching introduced to permit high-frequency solutions with a minimal number of grid points. Theory and experiment agree within experimental error except for the highest frequencies in the shadow region, where very rapid changes in pressure make precise measurements difficult. The results show that for frequencies of aeroacoustic interest, the scattered field is very large and cannot be ignored.
The Rayleigh wave in a finitely deformed isotropic elastic material
Authors: Iwashimizu Yukio , Kobori Osami
Published: October 2005

The propagation of the Rayleigh surface wave in an isotropic elastic material subjected to a homogeneous strain is studied theoretically. The displacement of the wave is assumed infinitesimally small, and its propagation direction is taken to be arbitrary. By the practical approximation that the second and higher orders of the initial strain are neglected, the formula for the change of the propagation velocity due to the strain is derived. In this analysis, the SH component of the wave cannot be assumed small and plays an important role, but it is finally ascertained that the resultant mode of the wave is almost the same as that in the linear theory of elasticity and the SH component contained in the mode is of the first order of the strain.
Generating vocal tract shapes from formant frequencies
Authors: Ladefoged Peter , Harshman Richard , Goldstein Louis , Rice Lloyd
Published: October 2005

An algorithm that uses only the first three formant frequencies has been devised for generating vocal tract shapes as seen on midsagittal x-ray diagrams of most English vowels. The shape of the tongue is characterized in terms of the sum of two factors derived from PARAFAC analysis: a front raising component and a back raising component. Stepwise multiple regression techniques were used to show that the proportions of these two components, and of a third parameter corresponding to the distance between the lips, are highly correlated with the formant frequencies in 50 vowels. The recovery algorithm developed from these correlations was tested on a number of published sets of tracings from x-ray diagrams, and appears to be generalizable to other speakers.
Exact effect of surface roughness on the reverberation time of a uniformly absorbing spherical enclosure
Authors: Joyce W. B.
Published: October 2005

We assess the validity of the Sabine, Eyring, and Kuttruff reverberation-time expressions, and of their underlying mean-path-length formula 〈l〉=4V/S, by determining the exact reverberation time and asymptotic sound distribution for a uniformly absorbing spherical enclosure with any amount of air absorptivity and with a surface that can be continuously varied from nonabsorbing to completely absorbing and from specular to randomly reflecting. In disagreement with an extensive literature that presents the Eyring formula as a correction to that of Sabine, we find, on the one hand, that Sabine’s formula and the applicability of 4V/S are vindicated in this application under Sabine’s stated conditions of weak absorptivity and (any nonzero amount of) irregular reflection, while, on the other hand, we find that Eyring’s and Kuttruff’s expressions are less accurate than Sabine’s unless the roughness and absorptivity of the surface exceed certain levels which are evaluated. Related concepts are discussed in some detail. Geometrical acoustics is assumed throughout, and its limitations are not considered here. The analysis is equally applicable to light in LEDs (light-emitting diodes) and to mechanical particles which stick or experience elastic reflection at the surface of their container.
Propagation of nonlinear acoustic waves induced by a vibrating cylinder. II. The three-dimensional case
Authors: Ginsberg Jerry H.
Published: October 2005

The method derived in Part I for investigating the propagation of weakly nonlinear acoustic waves in systems described by curvilinear coordinates is extended herein to a three-dimesnional situation. Specifically, this is a determination of a uniformly valid first order approximation to the waves radiating from an infinitely long cylinder vibrating harmonically in a mode having circumferential wave number n and axial wavelength L. The phenomenon of self-refraction, in which the rays, as well as the wavefronts, are distorted by the wave motion, is shown to be the explanation for some unexpected types of distortion in the profiles of the pressure and velocity component waves. An important development is the disclosure that the three-dimensional case of large, but finite, L cannot be used to deduce the response in the two-dimensional case of infinite L studied in Part I. The explanation of this situation is found to lie in the existence of a dispersion relation for the phase velocity of linear waves in the three-dimensional case.
Mode locking in nonlinearly excited inharmonic musical oscillators
Authors: Fletcher N. H.
Published: October 2005

Many musical instruments consist essentially of resonant systems having only approximately harmonic normal modes and excited by a force that depends nonlinearly on the velocities associated with those modes. An approximate condition is derived for the resulting sound spectrum to consist of components rigorously locked into harmonic relationship. Such mode locking is favored by nearly harmonic normal mode frequencies, by large mode amplitudes, and by large nonlinearity in the driving force.