bluuebunny/crossref_metadata_2025 huggingface dataset:
Comments on several papers on impact dampers
Authors: Grubin Carl
Published: October 2005

The impact damper reduces the vibration amplitude of a mechanical system through momentum transfer by impact and conversion of mechanical energy into heat. The fundamental configuration consists of a single mass particle moving in a container fixed to the primary single-degree-of-freedom vibrating system which is driven by a simple harmonic force. A number of years ago, the author developed the (basic) solution for the steady-state two-impact/cycle symmetric motion for the fundamental configuration. More recently, S. F. Masri has published in this journal some interesting extensions of the basic solution for the fundamental configuration, as well as studies of other configurations, Using his results it is shown herein that the basic solution for the fundamental configuration is, in general, the only combination of practical interest.
Comment on “Lateral wave contribution to the underwater signature of an aircraft” [J. V. McNicholas, J. Acoust. Soc. Am. 53, 1755 (1973)]
Authors: Urick R. J.
Published: October 2005

McNicholas' theory generalizes the contours given earlier for the contribution of the underwater lateral wave.
Comments on “Sound pressure in water from a source in air” [R. W. Young, J. Acoust. Soc. Am. 50, 1392–1393(L) (1971)]
Authors: Weinstein M. S.
Published: October 2005

The reported experimental data were obtained under conditions for which ray and wave theory yield essentially identical results. A test of the theoretically predicted difference requires the use of substantially lower frequencies than those employed.
Measurements of the vertical coherence of the sound from a near-surface source in the sea and the effect on the gain of an additive vertical array
Authors: Urick R. J.
Published: October 2005

Using a ship as a source of broad-band sound, measurements have been made of signal coherence between two deep hydrophones separated vertically by 500 ft. The results show that the phase coherence, in terms of the clipped correlation coefficient, falls off rapidly with horizontal range of the source. This decorrelation appears to be accounted for by multipath interference by bottom-surface reflections. The rate of falloff with range indicates a bottom loss between zero and 4 dB, increasing with frequency over the range 44 to 350 Hz. Expressions for the degradation of the gain of a linear vertical array produced by multipath interference are obtained.
Temporal effects in frequency discrimination by hearing-impaired listeners
Authors: Gengel Roy W.
Published: October 2005

The purpose of this experiment was to determine whether temporal effects on frequency discrimination were the same for persons with sensorineural loss and for persons with normal sensitivity. Estimates of the difference limen for frequency (DLF) were obtained for signals of 50- and 500-msec durations, for standard frequencies of 0.5, 1.5, and 3.0 kHz. In most of the conditions, the temporal effects on frequency discrimination were similar for hearing-impaired and normal-hearing subjects. Speech discrimination of the five hearing-impaired subjects also was measured. The highest rank-order correlation (rs = 1.0) was found between DLF at 3.0 kHz and vowel- and consonant-discrimination scores.
Laser-excited broadside array
Authors: Westervelt Peter J. , Larson Richard S.
Published: October 2005

The expansions and contractions of an absorbing medium resulting from the passage of an intensity-modulated laser are utilized to form a thermoacoustic array producing a highly directional acoustic wave propagating perpendicular to the axis of the laser beam.
Neural processing mechanisms in echolocating bats, correlated with differences in emitted sounds
Authors: Grinnell Alan D.
Published: October 2005

Bats that emit pulses containing constant wavelength (CW) components preceding an FM sweep show neural adaptations that differ conspicuously from those of bats emitting purely FM pulses. In contrast to “FM bats,” which have sharply tuned units distributed broadly throughout the range of their emitted pulses, “CW bats” have auditory systems tuned predominantly to a much smaller range corresponding to the restricted range of emitted frequencies. There is an “off”-response sharply tuned to the emitted CW frequencies. “On” response sensitivity is greater at just lower frequencies (CW component of less than 8-msec duration) or on either side of the “off”-frequency, with a null at that point (CW component of 10–20 msec or longer). The “off”-response, which is present at the level of the auditory nerve, apparently represents rebound excitation following non-neural suppression peripheral to the primary afferent fibers. It reflects a mechanism for increasing frequency discrimination and has the effect as well of enhancing response to the FM portion of the emitted pulses. High sensitivity to frequencies above that of the emitted CW, in “long CW” bats, is apparently tied to a use of the Doppler-shifted echo CW to detect and determine the angle and/or relative velocity of echo sources. CW bats show much less dramatic temporal resolution ability than FM bats, although it seems probable that the same mechanism of distance determination—measurement of elapsed time between emitted and returning FM sweeps—is used by both. CW bats, on the other hand, appear to have more units that are sharply sensitive to signal angle, showing strong binaural interaction. The consistent and conspicuous differences in neurophysiology in different species indicates not only that central analytic mechanisms are highly adaptable, but that these adaptations are important and closely tied to the types of orientation sounds used.
Coding and processing in the auditory systems of FM-signal-producing bats
Authors: Suga Nobuo , Schlegel Peter
Published: October 2005

For echolocation, many species of bats emit frequency-modulated (FM) sounds. When the central gray matter or reticular formation in the midbrain is electrically stimulated, these bats produce FM sounds similar to FM-orientation signals. The auditory system is excited by these emitted sounds, but the responses of auditory neurons in the midbrain are attenuated by a neural mechanism operating synchronously with vocalization. This neural attenuating mechanism is present between the auditory nerve and the inferior colliculus and may be a part of mechanisms for effective echo-detection. Among the various orientation sounds emitted by bats, FM sounds are the most suited for echo-ranging. In the lateral lemniscus, the majority of neurons show a very short recovery period, as well as frequent facilitation of their responses to a second tone pulse, so that these neurons are specialized for echo-detection and carry information necessary for echolocation. In the inferior colliculus, single neurons exhibit a broad spectrum of recovery cycles, so that these are probably able to scale echoes from different distances for the distance measurement. Neural-network models of a clock for echo-ranging are discussed. In the inferior colliculus and the auditory cortex, there exist neurons specialized for processing FM signals. For the excitation of these FM-specialized neurons, the direction, range, and speed of frequency sweep are important factors. The FM-specialized neurons always have a large inhibitory area and respond to FM sounds sweeping across this area. Although seemingly paradoxical, such properties are easily explained by neural-network models. Orientation sounds of several species of bats consist of constant frequency (CF) and FM components. Neurons specialized for the analysis of CF sounds have inhibitory areas on both sides of a very narrow excitatory area. The responses of the FM-specialized neurons to certain FM sounds in the presence of either FM or CF sounds are discussed in relation to the inhibitory area.
Echolocation by marine delphinids and one species of fresh-water dolphin
Authors: Evans W. E.
Published: October 2005

A brief summary is presented of the state of knowledge of echolocation by small toothed whales.
Summary Report for the Conference on Acoustics and Societal Problems
Authors: Johnson John C. , Stuart Alan D.
Published: October 2005

All organizations perform evaluations of their own purposes and effectiveness. The efforts of the Acoustical Society of America to this end during the past three years have included special studies by the Ad Hoc Committee on the Effectiveness of the Society. Recommendations of this Committee have resulted in a revitalization of activities in standards, formulization of a committee and programs in environmental acoustics, and the conduct of a Conference on Acoustics and Societal Problems. The Conference was made possible through a grant from the National Science Foundation and is reported upon here. The Conference, which was held at the Arden House 18–21 June 1973 with 52 participants in attendance, addressed the definition of problems of society at large which are of particular concern to the Acoustical Society of America as a corporate body, and to its members. The Conference established several vital elements—ranging from improved communications, through delineation of unsolved basic and applied research problems, to needs for strong leadership by the Acoustical Society of America—if an increased rate of progress is to be achieved during the next decade in areas dependent upon acoustics. A summary of these elements is set forth in this report.
Multidimensional encoding within the temporal microstructure of auditory displays. II
Authors: Pollack Irwin
Published: October 2005

Informational constraints were encoded within individual pulses of multivariate auditory displays. Sensitivity for the constraints was determined by forced-choice discrimination tests. With a single informational constraint imposed upon a combination of display variables, discrimination is impaired as additional display variables contribute to the constraint. With multiple informational constraints, discrimination improves with the number of constraints, and thereby improves with the number of controlled display variables. The latter result is consistent with the identification of individual dimensions of multivariate auditory displays.
Perceptions of personality from speech: effects of manipulations of acoustical parameters
Authors: Brown Bruce L. , Strong William J. , Rencher Alvin C.
Published: October 2005

A speech analysis-synthesis system was used to manipulate variance of fundamental frequency and a mechanical rate changer was used to manipulate speech rate. The synthesized and altered voices were tested for realism. Synthesized voices were mistaken for normal 50% to 58% of the time and rate-changed voices were mistaken for normal 78% of the time. Additional studies were conducted to test the effects of these acoustical manipulations on the adjective ratings judges made of speakers. Variance of intonation was increased and decreased by 50% for eight speakers. There was a significant trend for increased intonation to cause voices to be rated more “benevolent” by judges and decreased intonation to cause them to be rated less “benevolent.” In two additional studies, rate was decreased and increased by varying amounts. Slowing the voices caused them to be rated less “competent.” Speeding the voices caused them to be rated less “benevolent.” Results were more consistent over speakers for rate manipulations than for intonation manipulations.
An integral-equation approach to dispersion relations for guided elastic surface waves
Authors: Fossum A. F. , Freund L. B.
Published: October 2005

An integral-equation approach is utilized in numerically determining dispersion relations for guided surface waves on an elastic half space. The surface waveguide problem is first cast as a partial-differential-equation boundary-value problem whereupon an application of the bilateral Laplace transform enables transformed displacement to be determined as a function of transformed stress. By inverting the transformed displacement directly and incorporating the boundary conditions, one can obtain an integral-equation formulation of the boundary-value problem which is analyzed numerically to yield dispersion relations. The problem which is considered assumes that an elastic half space is in contact with two rigid smooth barriers. A waveguide is formed by arranging the barriers so that a strip on the surface of uniform width is traction free. It is demonstrated that a valid simplification in waveguide problems is that body-wave disturbances, localized in the vicinity of each edge of the guide, have negligible effect on the reflection of surface waves at the opposite edge of the guide.
Elastic waves in free anisotropic plates
Authors: Solie L. P. , Auld B. A.
Published: October 2005

The mathematical formalism for obtaining dispersion relations for acoustic waves in plates of arbitrary anisotropy is outlined, and dispersion curves for propagation in a (001)-cut cubic plate are presented. These results are compared to the uncoupled SV and P modes which, in turn, are related to the slowness curves for bulk waves. This approach provides an explanation for the behavior of the computed dispersion curves, and it also provides a means of approximating plate wave dispersion curves from the behavior of the slowness curves. The relationship of plate waves to surface waves is also explored for directions in which pseudosurface waves are known to propagate.
Forced response of a discontinuously constrained damped ring
Authors: DiTaranto R. A. , Lu Y. P. , Douglas B. E.
Published: October 2005

Experimental and theoretical results are presented and discussed for the radial driving point mechanical impedance of a damped composite ring made of a thin-walled ring having a finite number of mass segments equally spaced and attached to its circumference by a viscoelastic material. The effects of the operational temperature and frequency ranges of concern on the viscoelastic material properties are taken into account in the analysis. Experimental data show good comparison with theoretical results over a wide frequency range of interest.
Sound transmission in a channel with bilinear sound speed and environmental variations
Authors: Baer R. N. , Jacobson M. J.
Published: October 2005

The effects in a bounded channel of a bilinear sound-speed profile on ray geometry, travel time, and spreading loss are examined. General equations are derived. The case of bottomed source and receiver is considered in detail. Appropriate approximations are made and properties of the ray geometry, travel time, spreading loss, and the total acoustic field at the receiver are deduced. It is shown that the gross characteristics of observed phase variations off Bermuda may be generated by changes in sound speed associated with Rossby waves and tidal effects. The addition to the model of tidal depth variation leads to intensity variation which accounts for 80% of the range of intensity variations observed near Bermuda.
Spectral characteristics of sound transmission through the rough sea surface
Authors: Medwin H. , Helbig R. A. , Hagy J. D.
Published: October 2005

The predicted dependence of sound transmission on the statistics of the randomly rough interface between dissimilar fluids has been studied by use of the Helmholtz integral [J. Acoust. Soc. Am. 51, 1083–1090 (1972)]. The predictions have been verified for a plane wave passing from air through an aperture into water (laboratory model) and for radiation from a point source in air (laboratory and ocean experiments) for a wide range of surface acoustical roughnesses, R = k22σ2[(c2/c1)cos θ1−cos θ2]2. The roughness parameters σ,k ,c , and θ are the rms height of the surface, propagation constant, speed of propagation, and angle with the normal, respectively; subscript 1 refers to air and subscript 2 to water. When the surface is mirror smooth, the transmitted sound pressure is due to the change in divergence and change in impedance at the interface. For low roughness, R < 1, the mean-square transmitted pressure becomes decreasingly coherent with increasing frequency; its magnitude is decreased by the factor e−R compared to the perfectly smooth surface. For R ⩾ 1 the incoherent component dominates and the transmitted pressure depends also on the correlation length of the surface displacements.
Sound attenuation provided by several wood-framed floor-ceiling assemblies with troweled floor toppings
Authors: Grantham J. B. , Heebink T. B.
Published: October 2005

The sound attenuation provided by 11 wood-framed floor-ceiling assemblies with troweled floor toppings is presented. Three tests of assemblies with nailed gypsum board ceilings provided sound transmission class (STC) values of 48 to 50. By comparison, seven assemblies with ceilings applied on resilient channels and one with a suspended ceiling gave STC values of 55 to 59. The addition of glass fiber in the joist space, or the substitution of factory-fabricated, plywood-web joists for solid wood joists, provided less impressive improvements in STC values. Tests of three assemblies with vinyl tile floor covering and with pad and carpet provided an impact sound insulation class (IIC) of 50 to 52 with tile and 72 to 77 with carpet. The improvements in IIC that were anticipated from other changes in the floor-ceiling assemblies were clouded by the measuring and rating system. The need for a method other than the current ISO/R140 international standard for realistically measuring and rating resistance to impact sound transmission is emphasized by results of these tests.
Quantitative model for the effects of stimulus frequency upon synchronization of auditory nerve discharges
Authors: Anderson David I.
Published: October 2005

A theory has been developed which can be used to quantify the loss of synchronization in auditory nerve discharges with increasing stimulus frequency.The assumptions for the theory are (1) the probability of discharge versus time position within the period for very low stimulus frequency has the shape of a half-wave-rectified sine wave, and (2) travel times for impulses propagating along the acoustic nerve have a Gaussian statistical distribution around some mean travel time. With these two assumptions it is possible to predict the shapes of histograms which arise from higher frequency stimulation. Further, a single quantity (Gt ) may be derived from these fits which characterizes the whole progression from pure half-sine-wave distribution at zero frequency to a completely flat distribution at high frequencies.
Localization of pure tones
Authors: Casseday J. H. , Neff W. D.
Published: October 2005

Eight cats were trained to localize the source of tonal signals, presented in a free field. Tones of six different frequencies, in octave steps from 250 Hz to 8 kHz, were used. The angle at which an animal's performance was 75% correct was defined as the threshold for minimal detectable angle. This localization threshold was obtained for each cat at each frequency. Across frequencies the localization thresholds changed little from 250 Hz to 2 kHz, then increased greatly at 4 kHz and decreased again at 8 kHz. Similarities and differences in the performance of man and cat in localizing pure tones are discussed in relation to the possibility that the cat, like man, uses differences in binaural time and in binaural intensity as the principle cues for sound localization.
Anomalous loudness function for speech
Authors: Warren Richard M.
Published: October 2005

It is known that a greater attenuation is required for judgments of half-loudness with speech than for half-loudness with steady-state sounds. This study explored the role of reverberation in the anomalous loudness function of speech. Comparison stimuli were prepared by electrical attenuation of the standard stimuli, keeping the proportion of reverberant to direct components fixed for any particular judgment. A total of 1110 subjects were tested with speech or with isolated speech sounds, using a single judgment procedure employed in earlier studies designed to minimize known experimental biases. Changes in reverberation produced profound changes in loudness functions. Estimates of the loudness of speech resemble estimates of acoustic perspective, both being based upon the ratio of direct to reverberant sound as well as the intensity of these components. Evidence indicates that judgments of half-loudness of speech (as well as half-loudness of isolated speech sounds, noises, and tones) are equivalent to estimates of the effect of doubling distance from listener to sound source: The anomalous loudness function for speech is attributable to the special role of reverberation with this stimulus. These conclusions are in agreement with the physical correlate theory of sensory intensity.
Calculation of wave amplitudes by ray tracing
Authors: Chen Kenneth C. , Ludwig Donald
Published: October 2005

A method of calculating wave amplitudes by ray tracing is presented. It consists of an integration of six first-order differential equations, and three second-order quasilinear differential equations. The six first-order equations are the ray equations, and an equation for an additional Euler angle ψ. Two of the second-order equations are equations for two scale factors, h2 and h3, of an oblique system a2, a3 defined on the wavefront. The third second-order equation determines the angle χ between a2 and a3.
In-plane free vibrations of tapered oval rings
Authors: Brigham Gerald A.
Published: October 2005

A set of differential force and moment equilibrium equations for the in-plane dynamic strains in an oval ring of variable thickness is determined. This set is reduced to algebraic form by substituting Fourier series for the stresses and deformations. The resulting matrix is then truncated and evaluated in order to determine the first five normal modes and the first eight natural frequencies for an elliptical ring of uniform wall thickness. Excellent agreement is shown between theoretical and experimental data for several aluminum rings of pseudoelliptical shape.
Amplitude spectra of acoustic pulses in the ocean
Authors: Brown Edmund H. , Clifford Steven F.
Published: October 2005

An acoustic pulse propagating the ocean encounters weak thermal patches that scatter energy. If these patches are moving with a mean current perpendicular to the direction of propagation, a temporal fluctuation in the pulse-averaged amplitude occurs. This study calculates the temporal frequency spectrum of the pulse-to-pulse amplitude fluctuations and finds the result in terms of a frequency convolution of Tatarski's CW spectrum found for the electromagnetic case, and the spectral distribution of the initial pulse. The result easily generalizes to amplitude, phase, and phase-difference spectra, for plane, spherical, and beam-wave pulses.
Sound sources with corona discharges
Authors: Matsuzawa Kiichiro
Published: October 2005

A study has been made of three sound sources, each of which is constructed out of a plane wire gauze (positive electrode) and a great many needles (negative electrode) pointing toward it. Direct current coronas have appeared when a high de potential has been applied to the sound sources in the atmosphere. Various experiments have been performed on the acoustical characteristics of the sound sources as they are supplied with an ac current in the frequency range of 0.2–10 kHz, which is superposed on a de current. The sound sources are each considered as consisting of a resistance shunted by a capacitance, so far as the ac current is concerned. Theoretical formulas are obtained from the assumption that the sound is produced by a vibratory force which acts directly on the air between the electrodes and which has an rms value (d/b)I′, where d is the gap length, b = 2.2 cm2/V-sec and I′ is the rms value of an ac current through the resistance. It has been found the experimental results for 0.2–1 kHz are in good agreement with the calculated ones obtained from the formulas.
Prediction and measurement of the proportionality constant in statistical energy analysis of structures
Authors: Lotz Robert , Crandall Stephen H.
Published: October 2005

The fundamental equation of Statistical Energy Analysis (SEA) states that the average power flow between two coupled vibrating systems is proportional to the difference in their average modal energies. Under certain circumstances one can estimate the proportionality constant by modifying system boundary conditions on the separated systems and calculating or measuring changes in the systems. Newland's estimate, based upon blocking part of the system, is reexamined and limitations are discussed. Three alternative methods which circumvent blocking are presented. These were applied to predict power flow in experiments on coupled beams and on coupled plates wherein power flow through the coupling was measured directly as a product of force with velocity. The measurements support the fundamental SEA relation, including the null power point where the average modal energies are equal. Measured and predicted proportionality constants are compared.
Stapedius reflex and speech features
Authors: Borg Erik , Zakrisson John-Erik
Published: October 2005

Articulation scores and stapedius reflex responses to the same speech phrases were determined in subjects with unilateral stapedius muscle paralysis. Understanding of the speech sounds deteriorated significantly for maximal levels above 100 dB SPL, which was just above the threshold for the stapedius reflex. We conclude that the stapedius muscle extends the dynamic range of the ear by 15–20 dB.
Continuous speech data base with 14 marked vowel and nasal classes
Authors: Preusse John W. , Drucker Harris
Published: October 2005

One of the problems in the design of continuous speech recognition systems is evaluation of the stage which detects occurrences of phonemes in the speech signal. A method of evaluating and optimizing phoneme recognition networks has been developed which uses data obtained by manual “marking” of phoneme locations on a tape recording of speech. With the aid of a digital computer and display, 1090 occurrences of vowels, nasals, and “don't care” conditions were marked in a five-minute sample of speech. These data, which may be used for measurement of error rates in speech recognition systems, have been included in the IEEE Computer Society repository for data bases.
Free-flexural vibrations of an elliptical plate with free edge
Authors: Sato Kenzo
Published: October 2005

This work considers free-flexural vibrations of a free-elliptical plate by the use of Mathieu functions and modified Mathieu functions which are solutions of the differential equation of motion and by the method leading to the frequency equation by making use of orthogonal property of Mathieu functions. The non-dimensional frequencies calculated numerically for the first five normal modes of symmetrical vibration about both axes are tabulated for various aspect ratios and are shown in graphs for the eccentricities. The experimental results are obtained and are found to be in good agreement with the theoretical results.
Wavefronts in membranes caused by a moving pressure
Authors: Stronge W. J.
Published: October 2005

A steady-state solution is obtained for the displacements in an ideal membrane traversed by a steady pressure distribution. The pressure is considered to act behind a convex front that moves over the membrane surface with a constant speed. One part of this pressure front has a speed normal to the front, νν that is larger than a characteristic speed, c, of the membrane. In adjacent parts where νν < c an acoustic wave will move ahead of the pressure front. In this case, it is incorrect to postulate that an early-time solution will be a plane wave dependent on the nearfield excitation. The displacements behind the acoustic wave depend on the pressure distribution near where ν ν = c in addition to the local pressure distribution. In general, changes in the displacement gradient are more abrupt across the acoustic wave than across the pressure front.
Calibration of pressure-gradient transducers in an oscillating liquid column
Authors: Strasberg M. , Schloss F.
Published: October 2005

When pressure-gradient hydrophones are calibrated in a cylinder of liquid subjected to axial vibration, vertical orientation of the cylinder axis has several advantages over horizontal orientation.
Genetic features of deafness
Authors: Brown Kenneth S.
Published: October 2005

The pattern of hearing loss of children in schools for the deaf provides little information regarding etiology, but it is possible to evaluate the relative contribution of several etiologic factors by study of medical histories and family records. Traits such as thyroid or pigment anomalies can be used to identify particular genetic defects in a small proportion of deaf children; however, family data suggests that over half of all cases are the result of inheritance. Although most of the responsible genes are not now recognizable, pedigree data give excellent fit to simple genetic models. Thus we are able to estimate the minimum number of genes causing deafness and predict risks of deafness in offspring. Using experimental animals with patterns of hereditary deafness similar to man we can observe development and anatomy which suggest important directions for the study of deaf children.
Effect of anisotropic turbulence on aerodynamic noise
Authors: Goldstein M. , Rosenbaum B.
Published: October 2005

A model based on Lighthill's theory for predicting aerodynamic noise from a turbulent shear flow is developed. This model is a generalization of the one developed by Ribner. It does not require that the turbulent correlations factor into space and time-dependent parts. It replaces his assumption of isotropic turbulence by the more realistic one of axisymmetric turbulence. In the course of the analysis, a hierarchy of equations is developed wherein each succeeding equation involves more assumptions than the preceding equation but requires less experimental information for its use. The implications of the model for jet noise are discussed. It is shown that for the particular turbulence data considered anisotropy causes the high-frequency self-noise to be beamed downstream.
Effects of differing phonetic contexts on spectrographic speaker identification
Authors: Hazen Barry
Published: October 2005

This study investigated how well the file card system of “Voiceprint Identification” reported by Kersta fulfills its purpose of minimizing the effects of contextually caused spectral variation, and how well it serves as either an identification or population reduction tool. Subjects received training believed to be equivalent to that received by the experimenter in the Voiceprint Identification Training Course, and achieved error rates approximating those reported by Kersta for similar training tasks. Experimental tasks required subjects to identify unknown speakers from a population of 50 known speakers by first excluding all known speakers they were certain were not the unknown speaker, and then attempting absolute identification or elimination. Attempts were made under five experimental conditions created by combining two variables, phonetic context and inclusion of the unknown speaker in the known speaker population. The data show that the system tested does not effectively reduce the effects of contextual variation, and cannot be used for either absolute identification or elimination, or population reduction.The data suggest that the value of spectrograms for speaker identification purposes is limited to use as an investigative aid, and then only if speech samples of similar context and adequate duration are compared.
Intelligibility of temporally interrupted speech
Authors: Powers Gerald L. , Speaks Charles
Published: October 2005

The variations in intelligibility of a temporally interrupted connected discourse passage that result from changes in both switching conditions and message rate were studied. Six normal-hearing listeners estimated the intelligibility of ten, 15-sec speech samples presented monaurally at 36 interruption conditions (12 interruption rates × 3 speech-time fractions) for each of two speaking rates. Results indicated that for a given speech-time fraction, changes in intelligibility as a function of interruption rate depend on the precise temporal correspondence of switching and message parameters. Specifically: (1) for slow interruption rates, where on-time and off-time are greater than average word duration, temporal features of the message are relatively unimportant and intelligibility varies directly with speech-time fraction; (2) intelligibility functions will begin to recover from minimum at an interruption rate where off-time is equal to, or just shorter than, average word duration; (3) differences in performance along the recovery portions of the functions for the two message rates are negligible when intelligibility is expressed in terms of percent off-time relative to average word duration. It is apparent that a trading relation exists between speech-time fraction and interruption rate. Within certain limits, decrements resulting from lowering the speech-time fraction can be overcome by increasing the switching rate.
Transient pulse propagation in a fiber-reinforced material
Authors: Choi D. S. , Bedford A.
Published: October 2005

Propagation of plane pulses in an elastic half-space reinforced by parallel, uniformly distributed elastic fibers is analyzed using an approximate continuum theory. Comparison of the results with experimental data for the case of fibers normal to the half-space boundary shows excellent agreement. Typical results are also presented for other fiber orientations.
Negative resistance mode of forced oscillations of a string
Authors: Anand G. V.
Published: October 2005

A new mode of driven nonlinear vibrations of a stretched string is investigated with reference to conditions of existence, properties, and regions of stability. It is shown that this mode exhibits negative resistance properties at all frequencies and driving force amplitudes. Discovery of this mode helps to fill certain gaps in the theory of forced nonlinear vibrations of strings.
Bottom backscattering in the Java Trench area and the Tasman Sea
Authors: Hall Marshall
Published: October 2005

Acoustic backscattering strengths of the sea floors in the Java Trench, and the Tasman Sea near Sydney, have been measured for the first time. The results obtained for the Java Trench area are, on average, several decibels lower than the Tasman Sea results, which are similar to results that have been published for the bottom of the Atlantic Ocean. In each area, the standard deviations of the station-to-station variability are generally around 5 dB. All of the backscattering strengths increase with frequency; the rate of increase is greater at the lower grazing angles. The backscattering strengths also increase with grazing angle, and the rate of increase is greater at the higher grazing angles. Sea floors at depths from 4 to 7 km have similar backscattering strengths to each other, whereas sea floors at 1 to 2 km depth tend to have lower backscattering strengths.
The impulse response and mutual radiation impedance between a circular piston and a piston of arbitrary shape
Authors: Stepanishen P. R.
Published: October 2005

An approach is presented to compute the time-dependent force on a piston of arbitrary shape which results from the specified velocity of a circular piston in a rigid planar baffle. The force is expressed as the convolution of the specified piston velocity with an impulse response which is equivalent to the time-dependent force on the piston of arbitrary shape that results from an impulsive velocity of the circular piston. The mutual radiation impedance is shown to be equivalent to the Fourier transform of the impulse response. A circular piston and concentric annular ring are then investigated using the approach. A closed-form expression for the impulse response is presented and the impulse response is shown to consist of two pulses, each of which is associated with an edge of the ring. Numerical results are presented to illustrate the effect of changing the relative size of the piston and ring on the impulse response and mutual radiation impedance. Several interesting characteristics of the mutual radiation impedance are discussed and are shown to be in agreement with those obtained from an approximate solution.
Orientation sounds evoked from echolocating bats by electrical stimulation of the brain
Authors: Suga N. , Schlegel P. , Shimozawa T. , Simmons J.
Published: October 2005

The brains of several representative species of echolocating bats were found to contain regions concerned with the emission of species-specific orientation sounds. When the dorsal part of the reticular formation in the midbrain or the lateral part of the central gray matter is stimulated with a short train of electric pulses, the bat moves its mouth and pinnae and emits sounds identical to orientation sounds, with a latency of 25 to 60 msec. The acoustic parameters of the electrically elicited sounds and the temporal patterns of emissions vary with the location of the stimulating electrodes. Bats of the genus Myotis (little brown bat) emitted short frequency-modulated (FM) sounds both in nature and when electrically stimulated. Pteronotus parnellii (mustache bat) responded with sounds containing long constant-frequency (CF) and short FM components that were typical of the species. Eptesicus fuscus (big brown bat), Pteronotus suapurensis (naked-backed bat), and Noctilio leporinus (fish-catching bat) also made characteristic orientation sounds when electrically stimulated. It appears that the midbrain contains neural circuits for the emission of species-specific orientation sounds and that a part of the vocalization system is located in the regions juxtaposed to the inferior colliculus, an important neural center for echolocation.
Retroreverberation
Authors: Novoa Manuel
Published: October 2005

This is a report of a method found useful in finding defects easily in the response of acoustical chambers and sound systems. The method employs a complex sound or speech signal, which is successively recorded and reproduced several times in the chamber under test with the same double magnetic recording-reproducing system. The final results after several repetitions of the process are then studied.
Synthetic aperture sonar
Authors: Sato Takuso , Ueda Mitsuhiro , Fukuda Sadanao
Published: October 2005

This letter describes the principle and the fundamental results of experiments of a synthetic aperture sonar which enables us to resolve objects both in angle and range more sharply than the conventional ultrasonic imaging system. The basic idea of this technique is to introduce pulsed waveforms to ultrasonic holography and its operations consist of collecting hologram signals with ultrasonic pulses and using a computer for storage of these signals and image calculation. The elementary experiments were carried out using a single-wire target and ultrasonic waves of 1 MHz whose pulse duration was 12 μsec. The wire was set at a distance of 158 mm below the transducers and they were scanned over the hologram aperture of 50 mm across the wire. The results of the computer reconstruction were coincident with the theoretically expected values.
Comments on “Effectiveness of continuous spatial averaging in a diffuse sound field” [D. Lubman, R. V. Waterhouse, and C.-S. Chien, J. Acoust. Soc. Am. 53 650–659 (1973)]
Authors: Corrington Murlan S.
Published: October 2005

The integral for the spatial variance and the series for the average over the surface of the disk can be evaluated in terms of standard tabulated functions.
Experimental study of pulse propagation in curved elastic rods
Authors: Hsieh D. Y. , Lee J. P.
Published: October 2005

The distortion of longitudinal pulses in slightly curved elastic rods is discussed in terms of an elementary theory in which the effects of rotary inertia and radial shear are neglected. Moreover, when the wavelength of the pulse is long enough, practically all the bending effects can be justifiably neglected. The experimentally observed strain—time curve produced at one end of a curved brass-alloy rod by the impact of a pellet shot from an air gun is compared with that obtained theoretically using Fourier synthesis. Good agreement is found between theory and experiment. The main shape of the pulse travelling down the rod is retained even after the rod has turned 90° with respect to the initial direction.
Pressure dependence of the acoustic relaxation frequency associated with MgSO4 in the ocean
Authors: Bezdek H. F.
Published: October 2005

Utilizing horizontal transmission paths located at various depths in the ocean, the attenuation of sound waves has been measured at nominal frequencies of 30, 45, 60, 75, 90, and 145 kHz. Analysis of the data indicates that both the relaxation frequency at 50 kHz, which is usually attributed to the presence of MgSO4 in the sea, and the associated compressibility are functions of pressure. As pressure increases, the relaxation frequency shifts upward with a corresponding downward shift in the chemical compressibility. Results are also given for the pressure coefficient of attenuation which permit more precise predictions of acoustic attenuation at frequencies within the range of this experiment.
Long-range propagation in the shallow Bering Sea
Authors: Mackenzie Kenneth V.
Published: October 2005

Long-range underwater sound propagation measurements were conducted in the shallow Bering Sea during the summer of 1960. The region, which had been acoustically surveyed, has vast 20- to 25-fathom areas of flat bottoms, and is therefore ideal for shallow water propagation research. The program was implemented to investigate some complex aspects of shallow propagation by acquiring extensive sets of continuous wave data at several frequencies, as well as with explosives. Supporting environmental measurements were more controlled and complete than for most such efforts, with many sound speed profiles determined from bathythermographs. Sound was received by an anchored string of 12 hydrophones spaced vertically at intervals of 10 ft. The transmitting ship, anchored at ranges of 5, 10, 20, 40, and 80 kyd sent 15-minute CW signals of 58, 350, 700, and 1300 Hz. Single-frequency signals exhibited frequency spreading and amplitude fluctuations of 50 dB. Range and frequency dependence of relative pressure level spectra are described by empirical equations. Fifty-eight sound pressure level profiles, each based on an average of 88 000 data points, yielded accurate propagation loss data and demonstrated depth dependence with very little evidence of mode-stripping.
Frequency difference limens for narrow bands of noise
Authors: Moore B. C. J.
Published: October 2005

The fluctuations in amplitude and phase characteristic of narrow bands of noise are discussed in relation to the difference limen for the center frequency of such bands of noise. Two models are elaborated: a temporal model on which pitch is derived from the time pattern of nerve impulses, and a “place” model in which pitch is derived from the patterns of excitation on the basilar membrane. These models predict how the difference limen for center frequency will vary as a function of the bandwidth of the noise. The temporal model predicts certain effects for very narrow bands of noise which would not be expected on the “place” model. The predictions from the two models were tested using bands of noise synthesized by the addition of a large number of sinusoids. These bands of noise had an essentially rectangular spectrum. The results conform with the predictions of the temporal model for center frequencies of 2 and 4 kHz, and with the predictions of the “place” model for a center frequency of 6 kHz. It is concluded that the pitch of pure tones and very narrow bands of noise is determined primarily by a temporal mechanism for frequencies up to 4 kHz, and that at some frequency above this a “place” mechanism becomes predominant.
Musical octaves and pitch
Authors: Sundberg J. E. F. , Lindqvist J.
Published: October 2005

In certain types of musical performances systematic deviations from the frequencies of the equally tempered scale have been observed. In such scales the octave interval exceeds a 2:1 frequency ratio slightly. Experiments were carried out in which musically trained subjects matched the upper octave of a reference tone with a subsequent variable tone. Both signals were complex tones. The results show that (1) generally the physical size of the perceptually pure musical octave, briefly the physical musical octave (PMO), exceeds a 2:1 frequency ratio also when complex tones are used, and (2) the PMO is intensity dependent. This intensity dependence can be explained as a consequence of a pitch-intensity dependence in complex tones. A stretched scale derived from the experimentally established average PMO at different frequencies shows striking similarities with the stretched scales observed in musical performances.
Investigation of the statistics of sound-power injection from low-frequency finite-size sources in a reverberant room
Authors: Smith Wayne F. , Bailey J. Ronald
Published: October 2005

The measurement of sound-power injection into a reverberant room is subject to statistical uncertainties owing to large fluctutations of sound-pressure level with variations in source frequency and source and/or receiver position. Especially for low-frequency pure-tone sources, point-source theory indicates a requirement of many microphone and source positions if radiated power is to be accurately measured. An investigation has been conducted to determine the effect of finite source size on the power statistics in a reverberant room for pure-tone excitation. Theoretical results indicate that the standard deviation of low-frequency pure-tone finite sources is always less than that predicted by point-source theory and measurably less when the source dimension approaches one-half of an acoustic wavelength. A supporting experimental study was conducted utilizing an 8-in. loudspeaker and a 30-in. loudspeaker at eleven source positions. The resulting standard deviation of sound-power output of the smaller speaker with source position is an excellent agreement with both the derived finite-source theory and existing point-source theory if the theoretical data is adjusted to account for experimental incomplete spatial averaging. However, the standard deviation of the sound-power output of the larger speaker with source position is considerably lower than point-source theory indicates, but in good agreement with the derived finite-source theory.
Noise measurement standards for machines in situ
Authors: Lang William W.
Published: October 2005

Two kinds of documents prescribe standards for noise measurements on machines and stationary equipment in the field. Fundamental methods of measurement are described in standards prepared by American National Standards Committee S1 for which the Acoustical Society of America serves as the Secretariat and by Technical Committee 43 of the International Organization for Standardization (ISO). Test codes applicable to specific types of equipment are prepared in the United States by engineering societies and trade associations. These two classes of documents should be mutually supportive and interdependent, but such is not always the case. The requirements of existing standards on noise measurements in situ are summarized, the shortcomings of these documents are described and the needs for new standards are reviewed.