bluuebunny/crossref_metadata_2025 huggingface dataset:
Unified approach to aerodynamic sound generation in the presence of solid boundaries
Authors: Goldstein Marvin
Published: October 2005

In many cases of technological interest solid boundaries play a direct role in the aerodynamic sound generation process and their presence often results in a large increase in the radiated sound. A generalized treatment of the emission of sound from solid boundaries is presented. It is then shown how the various acoustic analogy theories of aerodynamic sound generation can be obtained as special cases of this equation.
Precision of reverberant sound power measurements
Authors: Lubman David
Published: October 2005

Determinations of sound power in a reverberation room are subject to random error whose size can be estimated and controlled by the knowledgeable laboratory manager. According to ANSI SI.21-1972, the chief sources of error are the variance of power output with source position and the variance of estimated room-averaged squared pressure. The latter can be expressed in terms of three factors. First, a frequency averaging factor (spatial variance) governed at midfrequencies by the spectrum shape and room reverberation time, at low frequencies by bandwidth and room volume, and at high frequencies by the direct field; second, a spatial averaging factor determined by the number and separation of fixed microphones or the path shape and size for a traversing microphone; and third, a rotating diffuser factor governed by the size and shape of the rotating diffuser in relation to room size and reverberation time.
Bearing estimation utilizing intervalized basis functions
Authors: Patrick E. A. , Carayannopoulos G. L.
Published: October 2005

Intervalized basis functions are used to represent a received signal s(t) and a set of training samples are used to estimate the coefficients of the basis function expansion for each interval. In particular, the approach is applied to a specific antenna system useful in passive sonar where there are two received signals, x(t)=s(t) cosθ + n x(t), y(t) = s(t) sinθ + n y(t). A maximum likelihood estimator is determined for θ after representing x(t) and y(t) by intervalized basis functions. The effect of using intervalized basis function is to be able to estimate signal-to-noise ratios separately in sequential time intervals. Through computer simulation it is demonstrated that improved bearing (θ) estimation results by using intervalized basis functions when signal-to-noise ratios can vary from one time interval to another time interval.
Perstimulatory loudness adaptation in selected cochlear impaired and masked normal listeners
Authors: Dirks Donald D. , Morgan Donald E. , Bray David A.
Published: October 2005

Two experiments were performed to determine the magnitude of threshold and suprathreshold adaptation for subjects with cochlear impairment due to noise exposure and normal listeners whose thresholds were raised by an external masking noise. For both groups, minimal loudness adaptation was observed near threshold (10 or 20 dB SL), but at higher intensity levels (20 to 30 dB SL), no loudness adaptation was measured over a 3-min period. The results of the threshold adaptation tests also indicated some adaptation near threshold. On an alternate binaural-loudness balance task, virtually complete loudness recruitment was found above 20-dB sensation level. The results suggest (1) that loudness adaptation and loudness growth in the cochlear impaired and masked ear at sensation levels beyond 20 dB reflect behavior for loudness similar to that found among normal-hearing subjects at comparable intensity levels and (2) cochlear impaired, masked normal, and unmasked normal listeners demonstrate comparable loudness adaptation behavior at low sensation levels.
Modification of DIF summating potential components by stimulus biasing
Authors: Durrant John D. , Dallos Peter
Published: October 2005

Positive and negative components of the summating potential (DIF SP) recorded with differential electrodes were studied in the presence of a low-frequency stimulus at different phases of this bias signal. Two clearly discernible ranges of behavior were observed depending on the sound-pressure level of the low-frequency stimulus. At the lower stimulus biasing levels, the SP components could be reversibly enhanced or depressed according to the magnitude (or equivalent magnitude at different phases) of the bias. At the higher intensity ranges, the SP output was generally depressed. The latter effect on the SP is a manifestation of the interference phenomenon.
Middle-ear function in the guinea pig
Authors: Manley Geoffrey A. , Johnstone Brian M.
Published: October 2005

The velocity and displacement of parts of the guinea pig middle ear were measured over a broad frequency range using the Mössbauer technique. Measurements under free-field/closed-bulla conditions gave a displacement curve with a slope of 6 dB/octave at frequencies above 3 kHz, breaking to a much steeper slope (30–40 dB/octave) above 25 kHz. Under closed sound-system/open-bulla conditions, the slope beyond 0.5 kHz was 7–8 dB/octave. These data indicate that a high-frequency displacement slope of 12 dB/octave (as used in mass-limited middle-ear models) does not exist in the guinea pig. Up to 25 kHz, the incus displacement is about 5 dB below the malleus, but larger differences exist at higher frequencies. The relative phase of the incus is near 0° to 6 kHz, then shows an increasing phase lag. The fusion of malleus and incus thus preserves an efficient ossicular linkage to high frequencies. At low frequencies, highest eardrum displacements are in the inferior portion, but above 15 kHz are on or near the malleus. At low frequencies, isoamplitude contours indicate that the drum does not vibrate like a stiff plate.
Non-metric scaling of loudness. I. 1000-Hz tones
Authors: Richards Alan M.
Published: October 2005

The loudness function for 1000-Hz stimuli, as determined by the conventional scaling procedures, grows as approximately the 0.60 power of the sound-pressure level. That is, a 10-dB increment in intensity corresponds roughly to a 2:1 loudness ratio. By plotting loudness as a unidimensional logarithmic function of intensity we imply that if A is twice as loud as B, which, in turn, is twice as loud as C, then A is four times C. To test this prediction, loudness-ratio estimates of 1000-Hz tones were obtained from three 7 × 7 matrices with differing stimulus ranges and interstimulus spacings. Using a multidimensional representation of the data based upon Shepard's Analysis of Proximities [R. N. Shepard, Psychometrika 27, 125–140, 210–246 (1962)], simple two-dimensional spatial configurations were obtained. It was found that, for each of the matrices, the obtained configurations did not conform to the shape of the configuration which would have been obtained had the 10-dB rule been in effect.
Loudness summation between tones from two loudspeakers
Authors: Scharf Bertram
Published: October 2005

Loudness summation between two equally loud 500-msec tones, centered on 2000 Hz, was measured in an anechoic room as a function of the frequency separation ΔF and onset time difference ΔT between the tones. One tone was presented via a loudspeaker 3 m from the subject and 45° to the left of his median plane, the other tone via a loudspeaker 45° to the right. A comparison 2000-Hz tone was presented via a third speaker in the median plane. Overall loudness increased with ΔF once the critical band of 300 Hz was exceeded. As ΔT increased from 0 to over 200 msec, loudness summation gradually declined. The Haas or precedence effect was evident at ΔT's between 2 msec and 50 msec and at ΔF's less than about 1000 Hz, where the six subjects usually heard a single sound originating toward the side of the leading loudspeaker. For the most part, loudness summation between tones from two separated loudspeakers resembled that between two tones presented monaurally via a single earphone. Loudness summation seems not to depend on the real or apparent locus of the sound source or sources.
Time-intensity trading functions for pure tones and a high-frequency AM signal
Authors: Young Lamar L. , Carhart Raymond
Published: October 2005

A 200-Hz pure tone, a 2400-Hz sinusoid, and an AM waveform, created by modulating 2400 Hz with 200 Hz, were employed in a time-intensity trading experiment. Phase delays were imposed on one of the binaural stimuli and the intracranial image was centered by decreasing the intensity of the opposite signal. The 2400-Hz tone was perceived in the midline for equal intensities of the binaural stimuli, irrespective of the interaural phase relationship. The AM waveform and the 200-Hz sinusoid required similar intensity decreases for the disparate phase conditions to achieve a centered image. The fact that both time and intensity alterations shift the perceptual location of the AM signal and the 200-Hz sinusoid in the same way provides confirmation of a new type to the view that the envelope periodicity of a high-frequency AM waveform is maintained in the auditory system, at least to the level where lateralization occurs. A second experiment provided additional evidence on this point.
Adaptation of phonetic feature analyzers for place of articulation
Authors: Cooper William E.
Published: October 2005

A series of experiments was conducted to determine the effects of selective adaptation on the perception of linguistic feature contrasts. The test stimulus consisted of a series of synthetic speech sounds, 13 CV syllables which varied in the starting frequency and direction of second- and third-formant transitions. Variations in these formant transitions are sufficient for the perceived consonant distinctions along what linguists have termed the place of articulation dimension; in this case, the perceived distinctions were among the syllables [b æ], [d æ], and [g æ]. It was found that a significant adaptation effect could be obtained for the feature place, as measured by both identification and discrimination responses. For various adapting stimuli, alterations in perception occurred, such that test stimuli lying near a phonetic boundary, normally perceived as having the same place value as the adapting stimulus, were perceived after adaptation as having a systematically different place value. In addition, the effectiveness of a real speech adapting stimulus [bi], for which the second- and third-formant transitions differed from those of the test stimuli, suggested that adaptation for the feature place operates primarily at a site of phonetic, as opposed to acoustic, feature analysis. Characteristics of this feature analysis site are proposed in light of the obtained perceptual shifts.
Nonlinear interactions in organ flue pipes
Authors: Fletcher N. H.
Published: October 2005

The ideas introduced by Coltman and Benade are developed into a quantitative formalism for treating the oscillatory behavior of an air column in nonlinear interaction with an air jet, as in an organ flue pipe or a flute. Explicit solutions are given for the case when the pipe has only two resonances and the nonlinearity is described up to cubic terms. The results of illustrative calculations are discussed.
Operating modes of the clarinet
Authors: Wilson Theodore A. , Beavers Gordon S.
Published: October 2005

Operating modes of the clarinet are investigated via a simple model consisting of a uniform flat reed coupled to a constant-area tube as a resonator. The analysis shows that, for lightly damped reeds, the operating frequency which is closest to the natural frequency of the reed is excited at the lowest blowing pressure. Further, the reed must be very heavily damped in order for the lowest resonance frequency of the tube to be preferentially excited. Experiments on a model clarinet, using metal reeds with different amounts of damping applied to the reed, confirm the pattern predicted by the analysis. There is close agreement between the measured and predicted values of the frequency ratio, but in many of the experiments the observed blowing pressure ratios were somewhat higher than the predicted values, the deviation being as high as 40% for the more heavily damped reeds.
Sound transmission in the porpoise head
Authors: Norris Kenneth S. , Harvey George W.
Published: October 2005

By using small hydrophones implanted in porpoise tissue and an external sound source, pulsed sound was found to be channeled by the blubber coat and strongly reflected by blubber-muscle interfaces. Implants in the head showed concentration of sound in the proposed sound channel of the throat and jaws, complete acoustic isolation in the peribullary air space, and sound focusing in the melon. Sound-velocity measurements in the melon showed a low-velocity core extending from just below the anterior surface toward the right nasal plug and a graded outer shell of high-velocity tissue. Such structure should beam sound generated or transmitted from the area of the superior narial passages forward and impedance match it closely to the surrounding water.
Structures for the detection of acoustic stimuli in the Atlantic codfish, Gadus morhua
Authors: Offutt George C.
Published: October 2005

Codfish, Gadus morhua, were classically conditioned to respond to tonal stimuli with a change in hear rate. Thresholds were obtained at frequencies from 10 to 600 Hz. Sensitivity of receptors was determined by ablation operations. The sacculus had the lowest threshold at 150 Hz (−35 dB re 1 μbar) and the lagena and utriculus might have successively higher thresholds. One fish was about 9 dB less sensitive at 150 Hz after swim-bladder ablation. A piezoelectric transduction mechanism was hypothesized for the sacculus. The lateral line might detect the acoustic stimulus and be most sensitive at 75 Hz to particle velocity (−14 dB re 1 μvar).
Note on acoustic scattering from random-amplitude/random-phase sinusoidal sea surfaces
Authors: Swarts Robert L. , Scharf Louis L.
Published: October 2005

An alternative approach is used to obtain a previously derived result for the acoustic field scattered by a random-amplitude/random-phase sinusoidal surface. The current approach is somewhat lengthier than that used earlier, but is straightforward and uses traditional concepts of probability theory.
On electrocochleographic electrode design
Authors: Coats A. C.
Published: October 2005

An investigation of the effect of contact-point position on the click-evoked response recorded from the external auditory meatus demonstrated severe attenuation of auditory-nerve and cochlear potentials as the contact point was moved outward from the tympanic annulus. Therefore, the ideal electrocochleographic (ECochG) electrode should contact the external auditory meatus as close as possible to the tympanic annulus. A clear-plastic, nontraumatic, intrameatal ECochG electrode is described, which contacts the canal wall within 4 mm of the tympanic annulus, yet is easy to insert. This electrode records click action potentials (APs) within 10 dB of normal threshold and of essentially the same amplitude as an intrameatal needle electrode.
Decay of weak waves in liquid crystals
Authors: Currie P. K.
Published: October 2005

Weak plane discontinuities carrying disturbances in orientation can propagate in liquid crystals of nematic type. It is shown that these waves decay exponentially in time, and the rate of decay is determined. It is found that this rate of decay depends on the angle between the direction of propagation and the orientation of the material, and that in most liquid crystals the waves will decay rapidly.
Matrix formulation of acoustic scattering from an arbitrary number of scatterers
Authors: Peterson Bo , Ström Staffan
Published: October 2005

The transition matrix formulation of acoustic scattering given previously by Waterman [J. Acoust. Soc. Am. 45, 1417 (1969)] is extended to the case of an arbitrary number of scatterers. The resulting total transition matrix is expressed in terms of the individual transition matrices and in terms of functions which describe a translation of the origin for the spherical (and cylindrical) wave solutions of Helmholtz equation. Explicit formulas are given for the case of two and three scatterers and the (finite) iteration scheme for the general case is described. Some numerical calculations concerning some aspects of the scattering from two spheres are also reported.
Infrasonic response characteristics of gas- and liquid-filled porous media
Authors: Smith Peter G. , Greenkorn Robert A. , Barile Ronald G.
Published: October 2005

The infrasonic (0.15–30 Hz) responses of several nitrogen-saturated porous models are measured experimentally. Within the frequency range covered, the results verify a theory proposed earlier by Smith and Greenkorn [J. Acoust. Soc. Am. 52, 247–253 (1972)]. Results of a similar response study of water-filled porous media show the effect of dynamic coupling between the solid and fluid phases, the excitation of which precludes agreement with a rigid frame theory. However, the results significantly indicate an approach to a condition of zero coupling at very low frequencies and/or low permeabilities.
Theory of the transient pressure response of fluid-filled porous media
Authors: Smith Peter G. , Greenkorn Robert A. , Barile Ronald G.
Published: October 2005

A theory is developed to describe the transient pressure response of rigid, isotropic, and uniform porous media, including the higher-order effects of viscous dissipation and thermal conduction. A transfer function which is transcendental in the Laplace time-image variable is obtained for the system. For the case of sinusoidal excitation, the results reduce to those given earlier by Smith and Greenkorn [J. Acoust. Soc. Am. 52, 247–253 (1972)]. Rational approximations are developed for the regime limiting cases of viscosity (long transient times or low frequencies) and inertia (short transient times or high frequencies), and are used to derive the system step and impulse responses.
Effect of a Rossby wave on the phase of an underwater acoustic signal
Authors: Baer R. N. , Jacobson M. J.
Published: October 2005

The effects of sound-speed variations, produced by an assumed Rossby wave, on ray geometry, travel time, and spreading loss are investigated for an ocean region such as the Sargasso Sea. A horizontally discretized sound-speed model is used, and a bottomed source and receiver are assumed. The phase of the total acoustic field is examined, and it is found that the major effects of the Rossby wave arise through travel-time variations. The period of the phase is that of the Rossby wave, and a formula for maximum phase variation is presented. In an example, the Eleuthera-Bermuda area is modeled approximately, and the total-field phase variation is examined as a function of Rossby wave propagation direction. The phase variation and period are highly sensitive to this direction, to the choice of parameter values, and to source and receiver depth.
Detection of low-frequency underwater sounds from a submarine volcano in the Western Pacific
Authors: Northrop John
Published: October 2005

Underwater sound signals in the frequency band below 100 Hz were recorded at several widely spaced SOFAR depth hydrophones in the North Pacific. The signals, which typically lasted from 5 to 30 sec and were spaced about 1 min apart, continued at a high level of activity during the fall and winter of 1973–1974. SOFAR fixes obtained on discrete events in the series plot in the volcano islands near 22°N, 144°E. Some of the signals exhibited spectral banding with fundamental frequencies in the 1–2-Hz region. If one assumes the spectral banding is due to constructional interference of surface- and bottom-reflected sound in the vicinity of the source, the calculated depth of the explosions was between 375 and 750 m. The volcanic noises are therefore believed to have originated from explosive volcanic activity associated with the shallow seamount charted at 21.9°N, 143.4°E with a minimum sounding of 150 m (Navy Hydrographic Office Chart No. 970000).
Reflection of a Gaussian ultrasonic beam from a liquid-solid interface
Authors: Breazeale M. A. , Adler Laszlo , Flax Larry
Published: October 2005

A Gaussian distribution of amplitudes in an ultrasonic beam reflected from liquid-solid interfaces is used in the reexamination of the concept of “beam displacement” which occurs at the angle of excitation of surface waves on the interface. Experimental results show that the energy of the reflected beam is redistributed into two or more beams at (or near) this angle. The theory of Brekhovskikh has been extended to include both a Gaussian input beam and the second derivative of the phase shift upon reflection. Reasonable agreement is obtained between theory and experiment for water-aluminum and water-brass interfaces. For water-beryllium and water-stainless steel the agreement is fair.
Vibrations of an infinite viscoelastic layer with a dissipative memory
Authors: Caputo M.
Published: October 2005

A model of elastic-energy dissipation based on a memory mechanism with two degrees of freedom is applied to the problem of the determination of the response spectrum at the surface of a layer when the spectrum is given at the bottom. The reaction of the surface of the layer is obtained directly with the Laplace-transform method. With the Fourier method, the amplification function is also found at the surface of the layer; it depends on the first power of the coefficient of viscosity—the Q−1 is proportional to a fractional power of the frequency. The reaction inside of the layer in the case of an infinite layer has also been obtained as function of time and in the Fourier space. It is verified that the amplification function (namely, the peak amplitude response of the free surface of the viscoelastic layer at a “resonant frequency”) depends strongly on the dissipation mechanism; a complete knowledge of the parameters of this mechanism could be of great help in the solution of many physical and engineering problems, especially in the cases when the characteristics of the layer can be varied.
Vehicular noise regulation in Hawaii
Authors: Burgess John C.
Published: October 2005

Hawaii has adopted a comprehensive regulation on noise from motor vehicle operation and enforcement has begun. Separate sets of objective noise-level limits are specified for the operation of light and heavy vehicles. Motorcycles are not given preferential treatment. Limits are specified in terms of sound level A, posted speed limit, and measurement distances between 20 and 50 ft. For heavy vehicles, limits are specified also for times of day and days of the week. A goal of 75-dBA maximum for any vehicle under any condition of operation is identified for the future. Permits and truck routes are used to allow stringent standards to be set initially in residential areas without resulting in significant interference with transportation functions that are in the public interest.
Passive detection of Gaussian signals with narrow-band and broad-band components
Authors: Pasupathy S. , Schultheiss P. M.
Published: October 2005

The performance of the optimum passive detector for Gaussian signals is studied for TW (observation interval—signal spectral bandwidth) products of the order of unity. Detection and false-alarm probabilities are evaluated for carrier-symmetric bandpass signals. Conditions are then obtained under which it is preferable to use either the narrow-band or the broad-band component of the received signal. Though in most situations the results advocate processing the higher-energy component, there are situations of practical importance where the lower-energy component may be preferred.
Comparison of ideal performance of some real-time acoustic imaging systems
Authors: Wang Keith Y. , Wade Glen
Published: October 2005

Good images have been obtained from several different approaches to real-time acoustic imaging, including approaches involving the following three phenomena: static-ripple diffraction, dynamic-ripple diffraction, and Bragg diffraction. Using threshold acoustic contrast as the basis of comparison, this paper examines analytically these three approaches and compares their sensitivities with those of another category of systems whose operation utilizes fundamental scanning modes. The analyses are based on idealized models where only the most fundamental noise is considered. The threshold contrasts are shown to vary in different ways with various system parameters. A nonexisting, hypothetical system, which is the best theoretical candidate among the fundamental scanning systems, is selected as the reference of comparison. For a set of consistent operating conditions compatible with the application of medical diagnosis, calculation shows that the inherent capabilities of the three systems involving, respectively, the three above-mentioned phenomena are of the same order. However, the inherent capability of the hypothetical reference system is considerably better. The other members of the category of fundamental scanning systems, although theoretically less advantageous than the hypothetical reference system, also enjoy advantages in terms of ultimate sensitivity.
Stability and accuracy of adaptive tests of speech discrimination
Authors: Bode Daniel L. , Carhart Raymond
Published: October 2005

Five experiments were conducted with normal listeners to investigate the reliability (stability) and validity (accuracy) of adaptive tests for measuring the linear portion of CNC discrimination functions. Monosyllables (consonant-vowel-consonant form) included in Northwestern University Auditory Test No. 6 were employed as test stimuli. Constant-level tests were used as criterion measures to judge the accuracy of best-of-five (100 words), best-of-three (50 words), doublet (50 words), and simple-up-and-down (50 words) adaptive tests. All tests were conducted under monaural (earphone) listening conditions in quiet or against a background of either 60- or 80-dB-SPL white noise. The shorter doublet tests were found to be as stable and accurate as the longer best-of-five procedures when seeking levels required for approximately 30% and 70% CNC discrimination. Adaptive tests using 50 words appear to be highly reliable and valid for determining the location and slope of CNC articulation functions with normal listeners.
Aerodynamic and acoustic study of stress in sentence productions
Authors: Brown W. S. , McGlone Robert E.
Published: October 2005

Two aerodynamic and three acoustic measures were related to stressed versus unstressed words of American English. Six speakers were required to repeat sentences while systematically varying stress. A group of listeners verified the place of stress intended by the speakers. Intraoral air pressure, air flow, vocal intensity, fundamental frequency, and duration were measured. Of these parameters, fundamental frequency was most significantly related to stress variations, suggesting that stress may be a laryngeal function. Moreover, a trading relationship between frequency and duration for terminal stressed words was noted.
Transmission of wave energy in curved ducts
Authors: Rostafinski W.
Published: October 2005

A formulation of wave-energy flow has been developed for motion in curved ducts. A parametric study over a range of frequencies determined the ability of circular bends to transmit energy for the case of perfectly rigid walls.
Sea-bed motion as a source of the ambient noise background of the sea
Authors: Urick R. J.
Published: October 2005

Some 12 years ago, G.M. Wenz hypothesized, on the basis of scanty data, that the seismic unrest of ocean floor was possible cause of the low-frequency noise background of the deep sea. In the present note this idea is reexamined quantitatively in the light of subsequent measurements with seismometers on the sea bed. It is found that the noise levels likely to result from sea-bed motion of the sea are indeed comparable with those of shipping, and therefore, must be included in models to explain and predict the level of the ambient noise background of the sea.
Sound absorption in mixtures of oxygen and helium at 296 K
Authors: Harlow R. G. , Street P. R.
Published: October 2005

The relationship f0 = 10 + 3.8h has been found to hold for mixtures of O2 and He with h between 50 and 130, where 10−3h is the molar fraction of He and f0 Hz is the frequency of maximum sound absorption per wavelength at 1 atm pressure.
A novel broad-band beamformer
Authors: Morgan D. R.
Published: October 2005

A novel, broad-band, sampled-data beamformer is described which requires considerably less hardware to implement than conventional methods for an electronically steered, single-beam application. In addition, this technique is capable of infinite beam steering resolution.
Effect of speaking mode on temporal factors in speech: vowel duration
Authors: Harris M. S. , Umeda N.
Published: October 2005

Previous investigators have shown that vowel duration decreases as the number of syllables in a word increases, when carrier phrases constitute the material. Umeda [J. Acoust. Soc. Am. 52, 133(A) (1972)] found that, in connected text, factors other than the number of syllables in the word have stronger influence in vowel duration. It turned out that differences were very small, if present at all, in vowel duration in connected text material. This investigation was conducted to find whether the differences result from speakers' idiosyncracies or from different speech modes—carrier phrase reading and connected speech. Two subjects, one of whom served in Umeda's study, read lists of monosyllabic and polysyllabic words in carrier phrases. Measurements were taken on the duration of one vowel /æ/, in stressed syllables in words of varying length. Conditions also investigated were the position of the stressed syllable and the class of the following consonant. Analyses of variance were computed separately for each subject. Results from the carrier sentence material confirm previous findings of the decreased duration, at least up to three syllables. One subject, while showing the characteristic shortening in vowel duration in the carrier phrase mode, exhibited almost no differences in duration of the vowel in connected text. Apparently the dependence of vowel duration on number of syllables is one of the dominating factors in the carrier phrase mode, but is a negligible factor in connected speech.
Sonic nearfields of a pulsed piston radiator
Authors: Beaver William L.
Published: October 2005

The formation of sonic pulses in the nearfield region of a pulsed piston radiator has been investigated by simulation on a digital computer. The results give insight into the sonic radiation process, showing the formation of pulses that replicate the piston motion, with trailing disturbances which originate from the rim. A comparison is made between pulsed and CW beam profiles, showing that there is little difference for moderate pulse lengths.
Scattering of elastic waves in an inhomogeneous solid
Authors: Chow T. S.
Published: October 2005

The propagation of plane harmonic waves through an isotropic material containing inhomogeneities is analyzed. The fluctuation density and elastic moduli are treated as random coordinate variables. The scattering intensity and cross section are calculated from the appropriate farfield solution and results are expressed in terms of correlation functions.
Low-frequency radiation characteristics of free-flooded ring transducers with application to a low-frequency directional hydrophone
Authors: Zalesak Joseph F. , Rogers Peter H.
Published: October 2005

Numerically predicted radiation characteristics of uniformly vibrating free-flooded rings are compared with experiment at frequencies above the monopole region but still below any resonances. Low-frequency velocity distributions for piezoceramic rings for several commonly used drive conditions are derived. Analytical formulas for the monopole radiation resistance, farfield pressure, and free-field voltage sensitivity are presented. A technique is developed for measuring the piezoelectric constants of free-flooded ceramic cylinders. It is predicted and experimentally verified that a free-flooded circumferentially polarized ring has maximum sensitivity in the axial direction for a band of very low frequencies. Thus, such a system may have application as a low-frequency directional hydrophone.
Measurement of wave propagation in a weakly inhomogeneous medium—the sea
Authors: Brownlee L. R. , Sagar F. H. , Ash D. E.
Published: October 2005

An account is given of measurements of amplitude fluctuations for sound transmitted over a fixed off-shore multiple-transducer range from projectors radiating in turn at the two frequencies: 35 and 65 kHz. The observed fluctuations are found to saturate with range even though their values are small for all of the ranges employed. This effect is explained in terms of a truncation concept which is found to apply not only to the results reported here but also to the previously published measurements of other workers.
Sound phase and amplitude fluctuations due to temperature microstructure in the upper ocean
Authors: Medwin H.
Published: October 2005

A truncated “universal” spatial correlation function of the differential index of refraction has been derived for reasonably well-mixed water in the upper ocean. Since it is predictable from a knowledge of only the depth of the ocean experiment, it permits previously derived expressions for sound phase and amplitude fluctuations due to microstructure to be used without further changes. The predictive technique is simple, requires only a knowledge of the standard deviation of the index, and appears to work well for a large range of experimental conditions.
Observations of strong current shears in the deep ocean and some implications on sound rays
Authors: Sanford Thomas B.
Published: October 2005

In the northern Sargasso Sea, recent continuous vertical profiles horizontal velocity and sound speed have revealed strong current shears of large horizontal extent and of inertial frequency in regions of low sound-speed gradient. The influence of shear on ray paths is particularly evident in restricted regions in which the sound-speed-gradient is smaller than the current shear. Stability considerations pertaining to stratified shear flow suggest that shear refraction is most likely to be of importance when the ratio of the vertical gradient of sound speed (CZ) and the Brunt-Väisälä frequency (N) is of order one. A simple model illustrates that rays emitted or vertexing within a layer of large shear, but small sound-speed gradient, will be significantly refracted. Moreover, since the interaction is not isotropic, the reciprocity theorem does not apply and the effects of shear on ray paths are dependent on the direction of the ray with respect to the current.
Coherence of low-frequency acoustic signals in the deep ocean
Authors: Shaffer J. D. , Fitzgerald R. M. , Guthrie A. N.
Published: October 2005

Calculations are presented of the functional dependence on the vertical (depth) and longitudinal (range) coordinates of the phase of a low-frequency continuous-wave signal. These calculations are compared with the measured dependence on the longitudinal coordinate. Inferences are drawn regarding coherence in time and in the transverse coordinate (azimuth).
Sound propagation in binary gas mixtures
Authors: Shen C. H. , Springer G. S.
Published: October 2005

The propagation of a sound wave through a monatomic binary gas mixture of arbitrary composition was studied using the model equations proposed by Hamel. A set of six simultaneous algebraic equations was derived containing the unknown wave speed V and absorption coefficient α. Simple expressions for V and α were obtained for the limiting case when the sound-frequency is much less than the mean collision frequency. The results were compared to Kohler's formula and to existing data.
Free flexural vibrations of a ring-shaped plate bounded by confocal ellipses
Authors: Sato Kenzo
Published: October 2005

This paper studies free flexural vibrations of a confocal elliptical ring-shaped plate using Mathieu functions and modified Mathieu functions which are solutions of the differential equation of motion. We give the procedure leading to the frequency equations by making use of the orthogonal property of Mathieu functions in order to satisfy the boundary conditions. Some numerical results are shown graphically in comparison with experimental ones.
Forced vibration of internally damped rectangular and square plates with simply supported boundaries
Authors: Snowdon J. C.
Published: October 2005

Consideration is given to the force transmissibility, driving-point impedance, and transfer impedance of internally damped rectangular and square plates with simply supported boundaries. Expressions are presented for the force transmissibility and impedance of the plates, for the magnitude of the discrete forces that occur at the plate corners, and for the force transmitted to the two outer edges of one plate quadrant. The plates are driven by a sinusoidally varying point force either at the plate center or at an arbitrary location. The application of dual forces at two arbitrary locations on the plates is also considered. The manner in which force transmissibility and impedance depend on frequency and on the location of the driving forces is illustrated by results that have been calculated for plate damping of the solid type.
Tuned acoustic absorbers for piston radiators
Authors: Smith David L. , Faulkner Lynn L. , Marco S. M.
Published: October 2005

The use of a tuned acoustic absorber as a cover plate for piston-type sound radiators is shown to significantly reduce the acoustic power radiated. A tuned acoustic absorber is a flat plate cover which is tuned so that its surface velocity distribution achieves cancellation of the surface velocity of of the sound radiator upon which it is mounted. Theoretical and experimental results are presented to quantify the amount of sound-power reduction possible using a tuned acoustic absorber under various conditions. Experimental results confirm the validity of the theory for calculating the sound power radiated by a tuned acoustic absorber. The effects of pertinent parameters on the performance of a tuned acoustic absorber are described.
Audiometric and histological correlates of exposure to 1-msec noise impulses in the chinchilla
Authors: Henderson Donald , Hamernik Roger P. , Sitler Ronald W.
Published: October 2005

Monaural chinchillas were exposed to 50 impulses of either 155-, 161-, or 166-dB peak SPL. The impulses had an A duration of 1 msec. Quiet threshold was measured at 0.25, 0.5, 1, 2, 4, and 8 kHz using the average evoked response technique. Recovery was monitored for 31 days; the animals were then sacrificed for surface-preparation histology. The median PTS at all frequencies was determined for each level of the impulse. The 155-dB level produced essentially no PTS, but each animal showed large and consistent outer hair-cell (OHC) lesions, 6 to 12 mm from the apex. The 161-dB level produced a dichotomy of results, with some animals showing no PTS and no hair-cell loss, while others had substantial PTS with attendant large hair-cell losses. The 166-dB group was consistent in showing a median 5–15-dB PTS with all animals having substantial hair-cell lesions. Micrographs are presented which show some of the structural and vascular alterations in the cochlea after impulse noise exposure.
Investigations on the sources of whole-nerve action potentials recorded from various places in the guinea-pig cochlea
Authors: Legouix Jean-Paul , Pierson Annick
Published: October 2005

The electric source of the whole-nerve action potential recorded by cochlear electrodes is generally considered to be part of the nerve trunk which runs through the internal auditory meatus. The comparison of the APs recorded in the first and third turn, after inactivation of the central end of the nerve trunk by KCl, shows differences in shape which support this hypothesis but also indicate that the source of AP extends somehow towards the apex.
Auditory sensitivity of a California sea lion to airborne sound
Authors: Schusterman Ronald J.
Published: October 2005

Estimates of the California sea lion's (Zalophus californianus) sound-detection thresholds in air were determined by the conditioned vocalization technique, covering a frequency range of 4–32 kHz. In air, sensitivity beyond 4 kHz gradually decreased to 24 kHz, with a rapid loss in sensitivity beyond 24 kHz. An average loss of 15 dB in the aerial audiogram of Zalophus, compared to its underwater counterpart, indicated that, like the harbor and harp seals' ears, the California sea lion's ear is water adapted. In-air hearing sensitivity of Zalophus may be best in the frequency range most characteristic of their vocal signalling during the reproductive season.
Stiffness of Reissner's membrane
Authors: Steele C. R.
Published: October 2005

It is suggested that Reissner's membrane normally has a slight curvature toward the basilar membrane. With the coiling of the cochlea, it is then a thin shell of positive curvature which has a behavior consistent with the results and observations of Békésy. The membrane is not “slack” but remains stable in the curved configuration during physiological stimulation.
Temporal interactions within a phrase and sentence context
Authors: Wright Thomas W.
Published: October 2005

Recent timing control research has shown that when a smaller linguistic segment within a repeated utterance is produced either shorter or longer than its average duration, the resulting deviation constitutes a timing error that is temporally compensated by the remaining segments in the utterance. In the present study, timing errors and the extent to which they are compensated define different levels of temporal interaction. Temporal interactions were studied within a phrase spoken in isolation and within the same phrase spoken in a sentence context. Preliminary data from four adult male speakers of American English suggest that there is no basic or single unit of speech timing and that a correct model of timing is likely to have both “chaining” and “preplanning” features.
Disk parametric acoustic array
Authors: Lockwood James C.
Published: October 2005

A parametric acoustic array, the primary field of which is a thin disk of cylindrically spreading waves, is analyzed. It is shown that the half-power beamwidth of difference-frequency radiation perpendicular to the disk exceeds the beamwidth of the corresponding collimated plane-wave parametric array by a factor of 1.316. The radiated intensity is less than in the plane-wave case by a factor of α0/k for the same total acoustic power in the primary waves, where α0 is the absorption coefficient at the mean primary frequency and k is the wavenumber at the difference frequency.
Concept of a directional spectral energy density in room acoustics
Authors: Pierce Allan D.
Published: October 2005

The directional spectral energy density is defined in terms of an ideal measurement and is discussed in terms of its role in the description of nonisotropic and nonuniform sound fields. A number of indices for characterizing the nondiffuseness of reverberant fields are mentioned.
Equation for the intensity of acoustic rays deflected by an object in a variable velocity medium
Authors: Burkhard Donald G. , Shealy David L.
Published: October 2005

A general formula is derived for the acoustic intensity reflected by an object of arbitrary shape embedded in a medium of variable index of refraction. Formulas are applicable in the ray acoustics limit. As specific examples, contours of equal acoustic intensity over a planar receiver surface are calculated for a plane wave of sound incident upon an ellipsoid and upon a sphere embedded in medium in which the velocity is a linear function of depth.
Short-wavelength backscattering cross sections of rigid and partially coated cylinders and spheres
Authors: Junger M. C. , Garrelick J. M.
Published: October 2005

The underlying assumptions of Kirchhoff-type formulations of the cross sections of cylindrical and spherical scatterers are reviewed, with emphasis on the respective merits of alternative asymptotic techniques. Both the geometric- and physical-acoustics formulations are shown to lead to substantial errors when applied to rigid scatterers partially coated with a finite-impedance coating. The sources of these errors are discussed in some detail.
Investigations of acoustic-seismic effects at long range: early-arriving seismic waves from Apollo 16
Authors: Dalins I. , McCarty V. M. , Kaschak G. , Donn W. L.
Published: October 2005

A reasonably comprehensive technical effort is described dealing with the investigations of acoustically generated seismic waves of Apollo 16 and Apollo 17 origin along the eastern seabord of the United States. This expanded effort is a continuation of earlier, rather successful detections of rocket-generated seismic disturbances on Skidaway Island, Georgia. The more recent effort has yielded few positive results other than a recording of an early-arriving seismic wave from Apollo 16 that was detected in Jacksonville. Evaluation of the negative results obtained in the Fort Monmouth area, with earlier studies of infrasound, local weather conditions, and geology, could be advantageous in the process of trying to gain a better insight into the acoustic-seismic resonance mechanism requiring phase-velocity matching at the atmosphere-ground interface. The evaluation of the recording of early-arriving seismic disturbances in Jacksonville also yielded certain new information about this acoustic-seismic resonance phenomenon.
Effect of foreign bodies on aerodynamic sound
Authors: Lauvstad V. R.
Published: October 2005

The paper deals with the problem of estimating the sound field generated by a limited region of turbulence containing foreign bodies of arbitrary shape and arbitrary composition. According to the Lighthill-Curle acoustic analogy, the aerodynamically-generated sound is the same as that due to a distribution of quadrupole and dipole sources within the fluid and over the surfaces of the bodies. It is known that the presence of foreign bodies will usually convert some of the intense nearfield energy of Lighthill's quadrupoles into the form of sound attributal to dipole and monopole sound whose amplitude is much greater than that of the free-flow noise. Current trends towards more sophisticated theories have again focused attention on this problem with drastically different results. Calculations are here presented to determine the extent whereby this multipole-conversion process actually is taking place. It is shown that a method involving matching of inner and outer expansions yields intensity laws of different orders of magnitude comparing favourably with observed results. Curle and Powell's attempts to solve the problem have been reexamined to show inconsistencies their analysis. In particular, Curle's retarded-wave solutions are recasted by use of Fourier synthesis. It is suggested that much of the discrepancies between the results in the present paper and the predictions of Curle's theory can be explained by a more carefully conducted analysis, throwing emphasis on various possibilities by which pseudosound tuned to the presence of foreign bodies may give way to sound fields being many orders of magnitude stronger than those emerging from Curle's analysis.
Thermoelastic waves in anisotropic solids
Authors: Banerjee Dipak K. , Pao Yih-Hsing
Published: October 2005

As motivated by the recent discovery of heat pulses propagating in dielectric crystals at low temperature, a continuum theory of thermoelasticity, which is modified to include the effect of thermal phonon relaxation, is applied to investigate the propagation of plane harmonic waves in unbounded anisotropic solids. Four characteristic wave speeds are found, three being analogous to those of isothermal or adiabatic elastic waves. The fourth wave, which is predominantly a temperature disturbance, corresponds to the heat pulses known also as the second sound. Velocity, slowness, and wave surfaces of the thermoelastic waves are analyzed and are illustrated with numerical and graphical results for NaF and solid helium crystals. A new definition of the group velocity for waves in a dissipative and dispersive anisotropic medium is proposed and is calculated and compared with the energy transport speed of thermoelastic waves.