bluuebunny/crossref_metadata_2025 huggingface dataset:
Dependence of Spatial and Temporal Correlation of Forward-Scattered Underwater Sound on the Surface Statistics. II. Experiment
Authors: Medwin H. , Clay C. S.
Published: October 2005

A large laboratory “sea” has been used to measure the spatial and temporal correlation of forward-scattered underwater sound and to interpret this behavior from the knowledge of the corresponding correlative properties of the statistically stationary time-varying surface. It is shown that the laboratory sea is a scaled replica of a low wind speed low-fetch ocean surface (Kinsman) in the acoustically significant parameters of displacement probability density and temporal correlation. The spatial and temporal sound correlations are found to have a modulated decrease with increasing displacement from the scattering axis and/or increasing time lag. The modulation is predicted by (a) dividing the insonified surface into defined, intracorrelated subareas and (b) describing the wind-driven surface in terms of a three-dimensional (space and time) height-correlation function that propagates in the windward direction. The experimental observations support the validity of the theory developed by Clay and Medwin which is described in the preceding paper, “Pt. I—Theory,”
Evaluation of Rayleigh's Hypothesis in Low-Frequency Vibrating Diffusion Flames
Authors: Deckker B. E. L. , Sampath P.
Published: October 2005

By using the concept of the over-all time for combustion of an element of fuel in a vibrating flame, bounded inequalities have been obtained that embody Rayleigh's hypothesis for the existence of stable flame vibrations. The analysis proceeds from an earlier expression for the hypothesis; namely, ∫ CYCLEh′P′dt>0. The limits of the inequalities are dependent, in the first instance, on the relative values of flame frequency and natural frequency of the fuel system. Experimentally, three frequency modes of vibration of enclosed laminar diffusion flames have been distinguished, but the transition from one mode to another is discontinuous. During transition, higher harmonics of the vibration are excited, but the final stable state always conforms to the phase relationships implied by Rayleigh's hypothesis. The hypothesis has been found to hold under the conditions of this investigation, except near the boundaries between the modes where the limits of the inequalities require modification. The maximum deviation from the limits given by the inequalities occurs at the mode boundaries, and in these cases, the heat release has been found to be exactly in opposite phase to the pressure. Systematic experimental results are presented in the form of flame maps, and some of the data used in the analysis are presented in tabular form. It is considered that this work provides a test of the validity of Rayleigh's hypothesis.
Effective Mass of Bonded Rubber Blocks
Authors: Hilyard N. C.
Published: October 2005

The oscillatory compression of a rectangular block of rubber of infinite length bonded to two massless plates is considered. The material comprising the block is considered to be dissipative as well as elastic and to have a finite density. It is found that deformation perpendicular to the direction of compression makes a significant contribution to the effective mass.
Transmitted Waves in the Diffraction of Sound from Liquid Cylinders
Authors: Brill Donald , Überall H.
Published: October 2005

We investigate the portion of the acoustic field which, during the scattering of sound from a liquid cylinder imbedded in another liquid, traverses the interior of the cylinder. It is resolved into a series of waves which undergo zero, one, two… additional reflections on the interior surface of the cylinder before they reemerge. Wavefronts and amplitudes of the transmitted waves are calculated using the saddle-point method.
Large-Amplitude Pulse Propagation—A Transient Effect
Authors: Moffett Mark B. , Westervelt Peter J. , Beyer Robert T.
Published: October 2005

An experimental demonstration of transient-signal generation during the propagation of a large-amplitude ultrasonic pulse has been made. This phenomenon was treated theoretically by Berktay [J. Sound Vibration 2, 435–461 (1965)]. Data are presented for a pulsed 10-MHz carrier propagating in CCl4.
Signal Processing to Reduce Multipath Distortion in Small Rooms
Authors: Flanagan J. L. , Lummis R. C.
Published: October 2005

The transmission between a sound source and a microphone in a small, hard-walled room is characterized by multiple peaks and sharp valleys. Sound received by such a microphone often is judged to be undesirably distorted or spectrally colored. Speakerphones and conference telephony systems are vulnerable to this acoustic distortion. A technique is described for combining the signals from two or more microphones to produce a single output having less multipath distortion than any of the individual microphone signals. The output from each microphone is filtered into a number of bandpass signals occupying contiguous frequency ranges. The microphone receiving greatest average power in a given frequency band contributes that signal band to the output. Each microphone, then, is used only for those frequency bands in which its received power is greater than any other microphone, so that the combined output contains less spectral coloration than the signal from any individual microphone. The processing method is studied by simulation on a digital computer. Broad-band noise and speech signals are used to test the method.
Electrical Impedance Measurements of an Electrothermal Loudspeaker
Authors: Russell G. A.
Published: October 2005

A simple configuration of electrothermal loudspeaker is described, which is capable of producing audible acoustic outputs, without the usual supplements of flame seeding, voltage transforming, or biasing. The acoustic levels are measured for various electrode positions and electrical driving signals. The input impedance of the flame is measured and found to be approximately equivalent to that of a parallel resistance-capacitance circuit.
Monaural Detection and Filtering
Authors: Mulligan B. E. , Elrod M.
Published: October 2005

Monaural detection of sinusoidal signals in noise is examined parametrically with an interest in extending our earlier work on prediction. The amplitude model is found to be compatible with empirical psychometric functions, human receiver operating characteristics, and the results of a narrow-band-noise experiment. Through an interpretation of the amplitude model in terms of filter bandwidth, an attempt is made to understand further the process of auditory filtering. Bandwidth is shown to vary as a function of both signal frequency and signal-to-noise (S/N) ratio. At very low S/N ratios, maximal tuning occurs in the region of 2200–2300 Hz. At higher S/N ratios, tuning improves as a function of frequency. To facilitate prediction, a table is made available. The table gives corresponding values of [(S/N0)13 − k], P[Hit], ds, (2S/N0W)12, and p[C].
Subjective and Objective Measurement of the Loudness Level of Single and Repeated Impulses
Authors: Reichardt W.
Published: October 2005

The subjective measurement of impulsive sounds involves equal duration for the 1-kHz comparison tones and the same repetition rate as the impulses being measured. The loudness levels of the short 1-kHz tones and repeated short 1-kHz tones can be taken from nomograms presented. The objective measurement of impulses requires an impulse sould-level meter with an RC-integrating network following the squaring device. The RC time constant must simulate the inertia of the human ear. The rise time and decay time constant must be the same. This impulse SLM sound-level meter indicated the same effective value as the classical sound-level meter for steady noises or for rapidly repeated impulses. The value indicated for slowly repeated impulses is higher, and we have a continuous transition to this higher value. The decay time constant must correspond to the rate of decrease in loudness after the sound has stopped. This can be described as τ = 25 msec or as 60-dB reverberation time of 0.35 sec. The reading of such an impulse sound-level meter with A weighting is designated LAI. Loudness calculation by Niese's (1956. Hochfrequenztech. u. Elektroakust. 65, 4.) method, for either single or repeated impulses, requires a spectrum correction ΔLSP to be taken from a nomogram, LNI=LAI+ΔLSP. Stevens' (1961. J. Acoust. Soc. Amer. 33, 1957) and Zwicker's (1960. Acustica 10, 304) methods, for single impulses or impulses repeated less frequently than 2/sec, require the dynamic impulse level LCI to be measured in 1-oct or 13-oct bands. Impulses repeated more frequently than 2/sec are measured and calculated in the classical way, but need by this method another impulse correction ΔLI=LAI−LAS.
Formant-Frequency Trajectories in Selected CVC-Syllable Nuclei
Authors: Broad David J. , Fertig Ralph H.
Published: October 2005

The frequencies of the first three vowel formants in 1728 monosyllables containing the Midwestern American English vowel /ɪ/ (as in fit) were measured by means of a computer-assisted technique employing a data-display screen, light pen, and television camera. Two-way analyses of variance for various time points of the formant trajectories reveal that nonlinear interaction between initial and final consonants is relatively small and that the influences of both initial and final consonants are highly significant throughout the vowel. A linear model gives the mean formant trajectory for a given consonantal context as the sum of a target frequency, an intial consonant transition function, and a final consonant transition function. The distributions of the differences between the model trajectories and the actual trajectories are reasonably approximated by normal stochastic processes. These distributions are interpreted not as errors of the model, but, rather, as due predominantly to the variability between syllable tokens of the same syllable type.
Performance Characteristics of an Experimental Harmonic Identification Pitch Extraction (HIPEX) System
Authors: Miller R. L.
Published: October 2005

A description is given of the HIPEX (Harmonic Identification Pitch Extraction) pitch measurement system. This experimental system is based on finding the common denominator of harmonically related components as separated out by narrow-band filters. The performance characteristics are given in relation to system-parameter changes. A statistical study of “period histograms” with a wide range of pitches gives an optimum peak-detection ratio of 0.91 to identify the peak corresponding to the fundamental period. Performance of the HIPEX system in the presence of noise is unusually good. Usable pitch information was obtained from speech in an approximate zero S/N condition. The effectively coherent addition of harmonic signals in the period histogram, regardless of their phase in the speech wave, implies that the technique is approaching an optimum for determination of the fundamental period from the available information.
Measurement System for Fetal Audiometry
Authors: Bench R. J. , Anderson J. H. , Hoare Margaret
Published: October 2005

There has recently been renewed interest in the early development of audition, especially in the fetus and neonate, but new techniques are required before reliable substantive findings can be made. A measurement system is described for assessing the capacity of the animal (goat) fetus for response to audio-frequency stimulation. Particular emphasis placed on the characteristics and development of an internally implanted hydrophone for monitoring sound levels close to the fetal head. Sound levels generated by an externally mounted vibrator and monitored at the uterine wall underwent attenuation increasing with gestational age. This is attributed to changes in the geometry of the goat with advancing pregnancy.
Transient Interactions of Spherical Acoustic Waves and a Cylindrical Elastic Shell
Authors: Huang H. , Wang Y. F.
Published: October 2005

The three-dimensional transient interaction between spherical acoustic waves with infinitely steep wavefronts and a circular cylindrical elastic shell of infinite length is investigated. The incident spherical wave is transformed into cylindrical partial waves by using the addition theorem for the modified Bessel function. The governing wave equation and equations of motion of the shell are solved by a series expansion-Laplace-Fourier transform technique. The transformed solution of the problem is obtained in closed form exact within the limit of series solution imposed by the Gibb's phenomenon. The physical solution is obtained by an accurate numerical scheme for the two-fold inverse Laplace-Fourier transforms. Detailed numerical results are obtained for the transient response of the shell and some quantitative effects of the sphericality of the incident waves on the response of the shell are also revealed.
Physical Interpretation of the WKB or Eikonal Approximation for Waves and Vibrations in Inhomogeneous Beams and Plates
Authors: Pierce Allen D.
Published: October 2005

The WKB or eikonal approximation is derived for flexural waves of constant frequency in inhomogeneous Euler-Bernoulli beams and plates and for waves in inhomogeneous Timoshenko beams. The derivation is based on the assumption of negligible partial reflection of waves and holds when the relative variation of parameters characterizing the medium is small over distances comparable to one wavelength. The approximate relations governing the variation of wave amplitude from point to point are derived from the requirement that no energy be lost from the wave. The extension of this technique to include evanescent waves as well as propagating waves is also discussed. As an application of the method, some simple results are given for the modal frequencies and normal modes of a cantilevered inhomogeneous Euler-Bernoulli beam. A general development of the eikonal method applicable to a wide class of mechanical systems is also given, which establishes the consistency of the energy-conservation technique with the results obtained by taking the eikonal approximation as the zeroth-order approximation to a series.
Approximate Technique for Treating Random Vibration of Hysteretic Systems
Authors: Lutes Loren D.
Published: October 2005

A technique is presented for predicting response statistics of a nonlinear hysteretic system by seeking an approximate equivalence between the hysteretic system and a nonlinear nonhysteretic system for which certain statistics of stationary response can be computed by an existing analytical method. The response statistics that can be computed include stationary displacement and velocity levels, and probability distributions. The technique is applied to the bilinear hysteretic oscillator, and the results are compared with experimental results and with the results of the equivalent linearization approximate technique of Krylov and Bogoliubov.
Asymptotic Dynamic Response of a Taut String on an Elastic Foundation to a Randomly Moving Load
Authors: Recker W. W.
Published: October 2005

This paper considers the dynamic response of a taut string, of infinite extent and resting on an elastic foundation, to a moving concentrated load, whose position X(t) can be regarded as a sample function of a stationary random process. An expression for the asymptotic value of the mean deflection is obtained without specification of the particular random process. The results obtained are applied to an example of practical interest.
Measurements of Acoustic Energy from Underwater Explosions
Authors: Kibblewhite A. C. , Denham R. N.
Published: October 2005

Measurements of the energy levels of underwater explosions are described. The energy-flux density was determined by an analog method, and the range and depth variations of level were separated. The horizontal range was 47 miles, the detonation depth was varied from 100 to 10 000 ft, and the charge weight varied from 1 to 300 lb. It was found that source-level curves given by E. A. Christian [J. Acoust. Soc. Amer. 42, 905–907(L) (1967)] can be sensibly used to correct energy levels for differences in charge weight and also applied to find the relative transmission loss as a function of depth, when a sequence of charges is fired at various depths.
Near- to Farfield Transition of a Scalar-Wave Pencil Beam
Authors: Sher Lawrence D. , Lassoeur Michel , Kritikos H. N.
Published: October 2005

The fields and power-flow patterns for a scalar-wave pencil beam are calculated without reference to a specific radiating structure and are plotted to show the features that characterize the transition from the near- to the farfield.
Scattering of Acoustic Waves in a Waveduct with an Irregular Boundary
Authors: Slavin L. M. , Wolf B.
Published: October 2005

A method originally formulated by the authors in terms of elastic wave theory is directly applicable to obtaining the scattered field produced by a steady acoustic wave propagating in a waveduct with an irregular boundary.
NOTE ON THE SPEED OF SOUND IN TWO-PHASE MIXTURES
Authors: Torvik Peter J.
Published: October 2005

Conditions under which the sonic speed of a mixture can be less than that of either constituent are developed from the well-known expression for the sonic speed. For a nonreacting mixture of two phases, such a minimum can occur if certain inequalities relating the ratio of densities and the ratio of impedances are satisfied. It is necessary, but by no means sufficient, that the denser material have the greater impedance.
Temporary Changes of the Auditory System due to Exposure to Noise for One or Two Days
Authors: Mills John H. , Gengel Roy W. , Watson Charles S. , Miller James D.
Published: October 2005

A subject was exposed on two occasions to an octave band of thermal noise centered at 500 Hz. The first noise exposure was for 48 h at 81.5 dB SPL. Five weeks later, the second was for 29.5 h at 92.5 dB SPL. Auditory function was evaluated by several types of measurements made prior to an exposure, during periods of quiet interspersed within an exposure, and at various times after an exposure. Temporary threshold shift (TTS) measured after 4 min of quiet (TTS4) increased for the first 8–12 h of exposure and then remained constant as the exposure was continued. At 750 Hz, the value of TTS4 at asymptote was 10.5 dB for the 81.5-dB exposure, and 27.5 dB for the 92.5-dB exposure. Recovery from TTS required 3–6 days. While TTS was present: (1) the time constant of temporal integration was reduced at 750 Hz; (2) there was delayed recruitment of loudness; (3) the amplitudes of the Békésy tracings were reduced; (4) frequency discrimination was unaffected; and (5) threshold shifts measured by evoked-response audiometry approximated those measured behaviorally, but the slope of the input-output function of the evoked response (N1−P2) was unchanged.
Pure-Tone Auditory Behavioral Thresholds in Three Species of Lemurs
Authors: Mitchell Curt , Gillette Richard , Vernon Jack , Herman Paul
Published: October 2005

Absolute thresholds were determined for pure tones of frequencies 100 Hz–40 kHz by the method of constant stimuli using a two-bar operant technique. Lemurs of three subspecies were trained to press a white bar to turn on a tone lasting 5 sec. During the tone, a single press on a second (black) bar resulted in food reward. Failure to respond simply terminated the trial. Response in the absence of tone was scored as a false positive response and resulted in a 12-sec shock of from 0.6 to 1.3 mA. Thresholds, based on a response probability of 0.5, indicate a lesser sensitivity in the low and middle frequencies than found in the anthropoid primates, but an apparent extension of sensitivity into the higher frequencies beyond the upper-frequency cutoff points found for the anthropoids.
Technique for Investigating Monaural Phase Effects
Authors: Nixon James C. , Raiford Carolyn A. , Schubert Earl D.
Published: October 2005

A procedure for detecting a monaual phase effect (MPE) involving a two-tone complex is described and the results for two observers are given.
Critical-Band Theory and the Auditory-Evoked Slow-Wave V Potential
Authors: Skinner Paul H. , Antinoro Frank
Published: October 2005

An investigation of the effects of signal-energy dispersion of the auditory evoked response (AER) was made in an attempt to determine whether the relationship between loudness and critical band might be reflected in changes in the waveform of the AER and thus provide electrophysiological evidence for the existence and limits of critical bandwidth. Two experiments were performed in which pure tones and noise bursts were employed to stimulate regions inside and outside of the critical band. The pure tones had center frequencies of 560, 1155, and 2480 Hz, and the noise bands had center frequencies of 250, 500, 1000, 2000, 4000, and 8000 Hz. Neither experiment revealed any change in the AER amplitude or latency with the changes in signal bandwidth.
Hemispheric Specialization for Speech Perception
Authors: Studdert-Kennedy Michael , Shankweiler Donald
Published: October 2005

Earlier experiments with dichotically presented nonsense syllables had suggested that perception of the sounds of speech depends upon unilateral processors located in the cerebral hemisphere dominant for language. Our aim in this study was to pull the speech signal apart to test its components in order to determine, if possible, which aspects of the perceptual process depend upon the specific language processing machinery of the dominant hemisphere. The stimuli were spoken consonant-vowel-consonant syllables presented in dichotic pairs which contrasted in only one phone (initial stop consonant, final stop consonant, or vowel). Significant right-ear advantages were found for initial and final stop consonants, nonsignificant right-ear advantages for six medial vowels, and significant right-ear advantages for the articulatory features of voicing and place of production in stop consonants. Analysis of correct responses and errors showed that consonant features are processed independently, in agreement with earlier research employing other methods. Evidence is put forward for the view that specialization of the dominant hemisphere in speech perception is due to its possession of a linguistic device, not to specialized capacities for auditory analysis. We have concluded that, while the general auditory system common to both hemispheres is equipped to extract the auditory parameters of a speech signal, the dominant hemisphere may be specialized for the extraction of linguistic features from those parameters.
Comment on “Pitch of Noise Bands Reconsidered” [J. D. Lovell, R. J. Madigan, and E. C. Carterette, J. Acoust. Soc. Amer. 48, 595(L) (1970)]
Authors: Small Arnold M. , Daniloff Raymond G.
Published: October 2005

It is suggested that the explanation given by Lovell et al. [J. Acoust. Soc. Amer. 48, 595(L) (1970)] represents an oversimplification of the situation.
Spatial Detectability Characteristics of One-, Two-, and Three Dimensional Array Receiving Systems
Authors: Cline Robert W. , Gregg William D.
Published: October 2005

The signal detectability gain performance index, for array receiving systems, is employed to derive the spatial detectability characteristics of some simple one-, two-, and three-dimensional configurations. Analytical results are obtained in terms of array geometry, dimensionality, and space-time correlation structure of the interference field. The analytical treatment is predicated upon decision theoretic foundations for waveform signal and noise structures. Homogeneous and isotropic Gaussian interference fields are assumed. Particular array-geometry examples treated are linear, triangular, rectangular, and isosceles pyramidal, employing three and four elements. Analyses of the spatial detectability gain characteristics are achieved for the above configurations. Illustrations of the detectability gain are given in a plane passed through the array coordinate system, for 360° about the main lobe, with various permutations in array parameters. Various advantages of the two- and three-dimensional configurations, over the one-dimensional configuration and the associated conditions, are discussed.
Distribution of the Sum of Clipped Waveforms in Terms of the Multivariate Input-Amplitude Distribution
Authors: Eby Edward S.
Published: October 2005

For an arbitrary multivariate input-amplitude distribution, it is shown that the density of the sum of clipped versions of the input waveforms is linearly related to the sums of the clipped moments of each order. This linear dependence implies that the vector of clipped-moment sums must lie within an N-dimensional tetrahedral restriction region in a moment space and provides a necessary condition on the multivariate input distribution. Previous derivations of the density and moments of the sum of clipped waveforms were restricted to the case in which the components of the input vector were statistically independent.
Response of an Elastic Cylindrical Shell to a Transverse Acoustic Shock Wave in a Light Fluid Medium
Authors: Geers Thomas L.
Published: October 2005

A plane acoustic step-wave traveling through a light fluid medium impinges upon an infinite, elastic, circular cylindrical shell whose axis is parallel to the wavefront of the incident wave. Approximate analytical expressions are given for the post-envelopment response of the first three modes of the shell appropriate to both a rigorous treatment of the fluid-shell interaction and a treatment that disregards the effects of the scattered wave. These analytical expressions, plus numerical computations of modal pressures and of displacement and strain responses for an aluminum shell in air, show why neglect of the scattered wave is a poor approximation.
Triboelectric Noise Generation in Some Cables Commonly Used with Underwater Electroacoustic Transducers
Authors: Donovan John E.
Published: October 2005

Quantitative data on the triboelectric signal output of 17 samples of commercially available cable are presented along with a description of the measurement apparatus. Voltages generated ranged from less than 10μV (for some of the “low-noise” cables) to more than 100 mV peak-to-peak when the cables were mechanically driven in three independent modes (bending, twisting, and crushing). Results show that triboelectric noise signals may be of greater amplitude than the hydrophone output.
Normal-Mode Propagation Calculations for a Parabolic Velocity Profile
Authors: Nicholas N. C. , Überall H.
Published: October 2005

The normal-mode series solution to the acoustical wave equation with parabolic velocity of sound profile C02/C2(z) = 1 − α2z2 is discussed. The full series representation is evaluated to exhibit focusing in both range and depth, show the effect of frequency on focusing, validate the series cutoff indicated by analysis, and test an asymptotic closed-form solution valid near the convergence zones.
Measurement of Noise on an Underwater Towed Body
Authors: Nishi R. Y. , Stockhausen J. H. , Evensen E.
Published: October 2005

Noise has been measured on a streamlined body of revolution towed by a hydrofoil craft at speeds up to 30 kt. The body was instrumented with accelerometers, flush-mounted hydrophones in the wall, and cylindrical hydrophones in the interior of the body. Towing was conducted with different lengths of cable. The noise in the body was found to result from body-wall vibrations, from farfield radiated noise sources, and from flow noise caused by pressure fluctuations in the turbulent boundary layer. Wall vibrations were found to be caused by cable vibrations, cavitation, and other flow-induced mechanisms. The pressure distribution along the towed body and thickness of the turbulent boundary layer have been calculated and are also presented to aid in the interpretation of the results.
Frequency Spectra of Forward-Scattered Sound from the Ocean Surface
Authors: Roderick William I. , Cron Benjamin F.
Published: October 2005

This study consists of a theoretical analysis, a model tank experiment, and an ocean experiment to determine the frequency spread of surface-reflected sound. The theoretical study is based on the concept that the phase and amplitude of the surface waves modulate the acoustic signal. The amount of spreading is a function of the incident acoustic frequency, the surface-wave spectrum, and the geometry of the experiment. The ocean experiment was conducted in winter off the coast of Bermuda. Two frequencies (750 and 1500 Hz) were emitted simultaneously from a fixed projector. The tones were surface reflected and received on a narrow-beam fixed bottom-mounted vertical array. Oceanographic and meteorological data were obtained in the vicinity of the insonified area. The time variation of the surface elevation was obtained from a wave staff, and this information has been processed to obtain the one-dimensional ocean spectrum. The experimental results are compared with theoretical predictions. It is shown that the comparison is excellent for both the model tank and the ocean experiments. Under all conditions for the ocean experiment, the frequency spread is less than 1.0 Hz, and under low sea-state conditions, the spread is about 0.2 Hz.
Comments on “Interferometric Measurement of Ultrasonic Velocity in Liquids—Effect of Diffraction” [S. V. Subrahmanyam, V. Hyder Khan, and C. V. Raghavan, J. Acoust. Soc. Amer. 46, 272–274(L) (1969)]
Authors: Del Grosso Vincent A.
Published: October 2005

Sound-speed dispersion in interferometers is attributable to multimode waveguide effects involving the lateral or radial boundary and not simply to free-field diffraction. The empirical equations which have been used for comparison with recent measurements are shown to correspond to special cases of a general theory.
The NASA Acoustically Treated Nacelle Program
Authors: Lowry John G.
Published: October 2005

Because of the rapidly increasing noise pollution in the vicinity of large commercial airports, the government established an interagency panel in October 1965 to develop recommendations concerning the implementation of a coordinated noise-abatement program. A part of NASA's contribution to this program resulted in the awarding of contracts to The Boeing Company and The McDonnell-Douglas Corporation in May 1967, directed toward reducing the noise under the flight path of the current large four-engine fan-jet commercial transports. This paper is a brief review of the goals and scope of these contracts to study and develop nacelle modifications to minimize fan compressor noise radiation.
Quantification of the Noisiness of “Approaching” and “Receding” Sounds
Authors: Rosinger George , Nixon Charles W. , Von Gierke Henning E.
Published: October 2005

This investigation represents the first phase of a research program designed to quantify subjective responses to time-varying sounds grossly approximating those produced by aircraft flying over an observer at rest. The basic sounds employed represented “approaching” and “receding” sources that continuously increased or decreased in intensity and/or frequency over a period of 15.25 sec. The comparative annoyance or noisiness of such sounds was evaluated by means of paired comparison and individual adjustment judgments. For the three experiments conducted, the findings indicated that: (1) Signals representing an “approaching” sound were generally judged more annoying than those representing a “receding” sound—in spite of the fact that the approaching and receding signals contained the same average intensity and frequency content over signal duration. (2) Signals with time-varying components—whether intensity or frequency—were judged to be noisier than signals with non-time-varying components. The maximum average difference due to time variation of the signal was 17.5 dB. (3) Time-varying intensity components appeared to have a greater influence on judgments of noisiness than did time-varying frequency components. (4) On the average, only small nonsystematic differences in noisiness were found as a function of the three frequency conditions investigated (125-, 1000-, and 4000-Hz-band center frequency).
Reply to “Some Pitfalls in Adaptive Testing” [C. D. Creelman and M. M. Taylor, J. Acoust. Soc. Amer. 46, 1581–1582(L) (1969)]
Authors: Campbell Richard A. , Counter S. Allen
Published: October 2005

A recent Letter to the Editor [C. D. Creelman and M. M. Taylor, J. Acoust. Soc. Amer. 46, 1581–1582 (1969)] asserts that Campbell's and Counter's [J. Acoust. Soc. Amer. 45, 691–693 (1969)] “methodological inadequacies preclude interpretation of their data.” We suggest that while the psychophysical methodology issues raised by Creelman and Taylor may be interesting, they are neither timely nor relevant to an interpretation of the Campbell and Counter data.
Audibility of High Harmonics in a Periodic Pulse
Authors: Duifhuis H.
Published: October 2005

A periodic pulse consisting of sufficiently narrow pulses has a frequency spectrum which contains all harmonics with equal amplitude. Owing to the limited resolving power of the hearing organ, only the low harmonics can be perceived separately. The high harmonics are heard together as one complex signal. We have found that harmonics above a certain number are audible when spectrally absent (the other harmonics being present at normal amplitude). The solution of this seeming paradox is to be found in an analysis of the time structure of the signal. This time analysis of the stimulus is (in a limited way) possible at the basilar membrane because of its limitation in frequency-resolving power.
Stimulation of the Vestibular Apparatus in the Guinea Pig by Static Pressure Changes: Head and Eye Movements
Authors: Reschke M. F. , Parker D. E. , von Gierke H. E.
Published: October 2005

Head and eye movements elicited by static pressure increases of up to 1-min duration in the external auditory meatus were recorded using guinea pigs as subjects. The minimum stimulus intensity required to produce a response was 1.5–2.0 cm Hg. Observations were made of response latencies, durations, and amplitudes as a function of stimulus intensities, durations, and onset rates. Head and eye movements elicited by the pressure stimulation were found to be significantly correlated. The results of this investigation are interpreted as supporting the hypothesis that stapes footplate displacement, and consequently perilymph/endolymph displacement, produce direct mechanical stimulation of the semicircular-canal receptors. Moreover, these results suggest that the same mechanism might be responsible for stimulation of the vestibular system by low-frequency inaudible sound and for the vestibular effects observed in response to audio-frequency high-intensity sound. In the latter case, vestibular stimulation is hypothesized to occur as a result of a shift in the average position of the stapes footplate owing to overdriving the ossicular chain.
Variations in the Effects of Electric Stimulation of the Crossed Olivocochlear Bundle on Cat Single Auditory-Nerve-Fiber Responses to Tone Bursts
Authors: Wiederhold M. L.
Published: October 2005

Spike discharges were recorded from single auditory-nerve fibers in anesthetized cats. Counts were made of the number of discharges in response to tone bursts at several sound levels presented both alone and preceded by a train of shocks delivered to the decussation of the crossed olivocochlear bundle (COCB). From these counts, a measure 〈Δu〉 of the COCB effect was computed for 141 fibers. 〈Δu〉 is maximum when measured with tone bursts at a fiber's characteristic frequency and decreases for tones of higher or lower frequency. 〈Δu〉 was found to be unrelated to the fibers' spontaneous discharge rates. 〈Δu〉 increases with increasing characteristic frequency up to 6–10 kHz and decreases above 15 kHz. For most fibers, 〈Δu) does not correlate with fiber threshold. Those fibers whose apparent threshold is more than 25 dB above the minimum threshold at their characteristic frequency have low 〈Δu〉's. These results are discussed in relation to previous gross-electrode studies and the anatomical distribution of efferent endings in the cochlea.
Critical Band with Respect to Temporary Threshold Shift
Authors: Yamamoto Takeo , Takagi Koichi , Shoji Hikaru , Yoneda Haruhiko
Published: October 2005

The existence of the critical band with respect to temporary threshold shift (TTS) was proved by the fact that TTSs, as a result of high-pass and low-pass filtered white noises, remained almost unchanged after they reached the certain value determined by the exposure time, irrespective of increase or decrease of the cutoff frequency of the exposure noises. Under the assumption that TTS becomes a linear function of a sound pressure level within the critical band, the center frequency and the width of the critical band for TTS at nine test frequencies (0.5, 0.8, 1, 1.5, 2, 3, 4, 6, 8 kHz) were calculated respectively from the data obtained by the narrow-band noises and the noises whose spectrum level is a linear function of log2f. It was found that the center frequency of the critical band is about half an octave below the test frequency and that the width in decibels is about 6 dB larger than that of the critical masking band.
“Assisted Resonance” in The Royal Festival Hall, London: 1965–1969
Authors: Parkin P. H. , Morgan K.
Published: October 2005

In 1964 an electronic system (“assisted resonance”) to lengthen the reverberation time over a limited frequency range was installed experimentally in the Royal Festival Hall, London. Following the success of this experimental installation, the frequency range covered was extended (to 58–700 Hz) and the installation made permanent. This paper describes the installation and operation of the permanent system, and its objective and subjective effects. Typically, the reverberation time in the empty auditorium has been increased in the 125-Hz octave band from 1.4 to 2.5 sec.
Generation of Fractional Harmonics in a Resonant Ultrasonic Wave System
Authors: Adler Laszlo , Breazeale M. A.
Published: October 2005

The problem of a fluid-filled cavity caused to resonate by an ultrasonic wave is described as a parametric phenomenon. Variation of the cavity resonance frequency as a result of the periodic change of length produces the condition for parametric resonance. As a result, fractional harmonics of the driver transducer frequency are generated. The wave equation describing the system is transformed into an ordinary differential equation with periodic coefficients. The solution of this differential equation (Mathieu's equation) predicts frequency doublets which have been observed experimentally. A threshold condition of parametric excitation is derived from the region of unstable solutions of Mathieu's equation. This threshold condition relates the amplitude and frequency of the driver transducer to the cavity length and to the absorption per wavelength of the medium. Reasonable agreement between theory and experiment is obtained.
A Graphic Solution for Wave Velocities of Sound in Crystals
Authors: Bond W. L.
Published: October 2005

A method is presented for solving the cubic equation involved in calculating velocities of sound in any direction in crystals.
Propagation of Sound in a Turbulent Atmosphere
Authors: Clifford S. F. , Brown E. H.
Published: October 2005

Applying a perturbation technique to the correct form of the equation for the acoustic pressure field in a viscous turbulent atmosphere yields the power spectra for the amplitude and phase fluctuations of a propagating plane wave. The development includes the effects of absorption and removes the restrictions on wavenumber that previously prevented solution of the problem for other than ultrasonic frequencies. For a wide range of propagation parameters, the amplitude and phase spectra found by Tatarski for optical propagation are shown to be good approximations for acoustic waves. Complete expressions, without limitation on the assumed refractive-index spectra, determine the range of validity of this result and also provide an exact first-order solution.
Radiation by Finite Circular Pistons Imbedded in a Rigid Circular Baffle. I. Eigenfunction Solution
Authors: DeVore R. V. , Hodge D. B. , Kouyoumjian R. G.
Published: October 2005

Spheroidal wavefunctions have been used to calculate the patterns and radiation impedances of several piston configurations mounted in a rigid circular baffle. The results are of some practical interest, and they also may be used to check approximate solutions. For one of the configurations there is no diffraction at the edge of the baffle; in this instance, the radiation characteristics are identical with those of the infinite baffle case.
Response of a Covering Plate to Noise in a Viscoelastic Half-Space
Authors: Remington Paul J. , Crandall Stephen H.
Published: October 2005

The steady-state response of an infinite Bernoulli-Euler plate placed on the surface of a vibrating viscoelastic half-space is studied both theoretically and experimentally. The surface displacements of the half-space before the plate is added are assumed to be stationary homogeneous random functions of position and time. Given the wavenumber-frequency spectra of these displacements, the frequency spectra of the displacements of the plate-half-space interface are calculated, assuming that there is no shear stress between the plate and the half-space. A test of the theory was performed in which several Plexiglas plates of varying thickness were placed on the vibrating surface of an “experimental half-space,” a tub filled with Plasticine (a modeling clay). Wavenumber spectra transformed from correlation measurements, made on the surface of the clay, were used in the theory to obtain response predictions that agreed to within 3 dB of measured response levels.
Bottom-Reflection-Loss Model with a Velocity Gradient
Authors: Morris Halcyon E.
Published: October 2005

Theoretical bottom-reflection losses are computed using a multilayered model of the ocean bottom in which the layers are considered to be absorbing liquid sediments with velocity gradients. The sound velocity of each sediment layer is assumed to be a nearly linear function of depth z. In this case, the acoustic field in the sediment layers can be represented as a linear combination of Airy functions. Comparisons of theoretical and measured bottom-reflection losses are made for three areas at frequencies from 0.1 to 1.6 kHz.
A New Approach to the Determination of Acquiring Rays in Singly and Doubly Layered Oceans
Authors: Raphael David T.
Published: October 2005

For singly or doubly layered oceans, it is possible to determine by means of an exact closed-form solution those rays having initial angles at the source depth which lead to acquisition of the point target. For the specific problems considered, the stationary target coordinates relative to the source plus the oceanic sound-velocity profile composed of either one or two linear-gradient layers are assumed to be known. An algebraic as well as an alternative geometric derivation of the closed solution for the initial target-acquiring ray angle at the source depth is first presented. The resultant solution is then used to solve the following two problems: (1) a ray having undergone n reflections from a horizontal surface, with source located at the surface depth and (2) a ray having undergone n interface crossings, with source located at the interface. Four cases need to be treated in order to solve this two-layer problem completely. For problems 1 and 2, existence conditions are developed which must be satisfied before the closed-form solution can be used. The acquiring-ray initial angles then obtained are related to the corresponding intensity equations developed in a previous article by P. Uginčius [J. Acoust. Soc. Amer. 45, 198–200 (1969)]. As a consequence of the aforementioned existence conditions, it is possible to determine the equations of the caustic curves which form the envelopes of the solution sets.
The Characteristics of the Acoustical Pulses Emitted by Boiling Bubbles in Water
Authors: Saxe R. F. , Cothren R. K.
Published: October 2005

An investigation of the acoustic emissions from boiling bubbles in water has been made using two methods—frequency analysis and pulse-height analysis. Pulse-height analysis, using coincidence techniques, shows that the pulse-height spectrum of boiling bubbles in water has a distribution which is independent of the amount of boiling, indicating that the distribution is governed by liquid, vapor, and possible wire-surface characteristics. The addition of wetting agent to the water has an appreciable effect on the pulse-height distribution. Frequency analysis is shown to produce no information about pulse characteristics.
Depth Dependence of Bubble Pulse Periods of Point and End-Fired Line Charges
Authors: Wentzell R. A. , Adlington R. H. , Moldon J. C.
Published: October 2005

A theory of the depth dependence of the first bubble pulse period of an infinitely long cylindrical charge is developed. The charge is represented by a cylinder of adiabatic gas and the time equation for expansion from its initial radius to equilibrium is derived as a function of the weight of explosive per unit length and the hydrostatic head. Theoretical results are compared with measured bubble pulse periods of end-fired line charges detonated at depths between 90 and 10 600 ft. The length-to-diameter ratio of the charges varied from 45 to 320 and the weight of explosive per unit length varied from 0.11 to 0.43 lb/ft. There is substantial agreement between theory and experiment, the agreement improving as the length-to-diameter ratio of the charge increases.
Temperature Dependence of the Ultrasonic Velocity in Cyclohexane
Authors: Taylor E. W. , Alpert S. S.
Published: October 2005

The velocity of 18-MHz ultrasound in cyclohexane as a function of temperature was measured by Bragg diffraction of laser light. The adiabatic compressibility was calculated from these measurements.
Sound Channels in Surficial Marine Sediments
Authors: Hamilton Edwin L.
Published: October 2005

Most deep-sea silt-clay surficial sediments have sound velocities less than that in the water overlying the bottom. These sediment velocities, bottom-water velocities, and recently established sediment-velocity gradients, define a sound channel in surficial sediments which should be present in most deep-sea floors, and in some shallow-water areas. The height of these sound channels in deep water should normally vary between 15 and 60 m.
An Impractical k
i3 Transducer
Authors: Woollett Ralph S.
Published: October 2005

A transducer is proposed that is capable, in principle, of achieving Baerwald's ki3 coupling factor. This coupling factor is noteworthy because it is the highest coupling factor that a piezoelectric ceramic can exhibit under any quasistatic extensional mode of deformation. The transducer is impractical, but its analysis may help to clarify the physical significance of ki3.
IN SEARCH OF AN INSTANT AUDIENCE
Authors: Moore J. E. , West R.
Published: October 2005

This paper describes the making and testing of dummy human beings to be used in experiments to discover the absorption of direct sound passing over the heads of an audience at various angles of incidence. It was found possible to make such dummies at small cost, for quantity production, which closely resembled human beings in their absorption and diffraction characteristics of at all important audible frequencies. A description of the materials and manufacture of the dummies is given in detail, together with details of test results, to enable other research workers to make them. An incidental result of the tests was the finding that the coefficient of sound absorption for human beings seated about 5 ft apart was almost double that of a closely seated audience at 2 kHz and above.