bluuebunny/crossref_metadata_2025 huggingface dataset:
Pitch of High-Pass-Filtered Pulse Trains
Authors: Guttman Newman , Flanagan J. L.
Published: September 2005

This experiment determined the pitch of mixed-polarity pulse trains, high-pass-filtered at 2 and 4 kcps. It was found that pitch may be associated with pulse rate at rates higher than the limit of 150 pps found with unfiltered pulses. At frequencies higher than those supporting pulse-rate pitch, some tendency to hear a pitch equal to the spectral difference frequency appears. Evidence for the difference-frequency interpretation is the contrast in pitch of patterns equated for pulse number but possessing all-harmonic and odd-harmonic spectra. Comparison of the pitch results with a computer simulation of basiliar-membrane displacements revealed some correlation of difference-frequency pitch with displacement envelope. It is hypothesized that the high-pass input-filter slope combines with the natural-membrane low-pass characteristic to form a narrow passband. The envelope of membrane displacement at the passband site tends to contain a pitch-significant frequency component equal to the difference frequency. It is furthermore suggested that a major source of the pitch of low-frequency broad-band periodic sounds is roughly the 400-cps region of the basilar membrane.
Light Diffraction by Ultrasonic Waves for Oblique Incidence
Authors: Mayer Walter G.
Published: September 2005

The diffraction of light by progressive, sinusoidal ultrasonic waves in water is investigated experimentally for conditions where Raman-Nath diffraction or Bragg reflections might occur. Results are given for frequencies between 3 and 12.3 Mc/sec and for angles between the direction of sound and light propagation within ±1° of normal incidence.
Some Factors Governing the Lateralization of High-Frequency Complex Wave Forms
Authors: David E. E. , Guttman Newman , van Bergeijk W. A.
Published: September 2005

The experiments described here were designed to investigate the reciprocity of interaural intensity and arrival-time differences for complex signals above 1500 cps. When clicks are brought to the ears at nearly the same times and intensities and at a typical repetition rate of 20 per second, single clicks are perceived as originating inside the head. As had previously been shown, place of lateralization depends upon interaural arrival-time and intensity differences. Centering may be achieved over a range of these differences. Our results show that with 2000 cps high-pass clicks a very nearly linear trading relationship exists between the time and intensity differences (in decibels) when the product of the two intensities is constant, that is, when the sum of the binarual intensities (in decibels) is constant. The slope of the function depends upon sensation level and is independent of repetition rate at moderate levels and rates up to at least 140 clicks per second. Lateralization may also be controlled by masking the clicks with noise. Similar experiments with other wave forms will be reported also.
Comparison of Threshold in Air and in Water
Authors: Wainwright Walter N.
Published: September 2005

Hearing thresholds were measured for two subjects over a frequency range of 250 to 4000 cps. These measurements were made both in air and in water. When threshold intensity levels are compared it is shown that the greatest loss in hearing acuity occurred over the frequency band from 500 to 2000 cps and amounted to about 20 db, while below 300 cps the threshold intensity in water was lower than that in air. Measured intensity levels for an underwater swimmer speaking into a face mask are also presented.
Detection of Multicomponent Auditory Signals in Noise
Authors: Green David M.
Published: September 2005

How can the detection of a multicomponent signal be predicted if the detection of each single component of the complex signal is known? In the detection of a single sinusoidal signal, Fletcher's critical-band hypothesis asserts that all but a narrow band of frequencies near the signal to be detected may be ignored. What will happen if two or more components, widely separated in frequency, are simultaneously presented is uncertain. Complex signals using various durations, frequency spacings, and amplitudes were generated. Both monaural and binaural observations were made. In each experiment the detection of each individual component was first determined. Then a complex signal was generated by adding two or more of these components together. The detection of the complex signal was determined. Three models are considered: (1) a model which asserts there is no summation, (2) a statistically independent threshold model, and (3) a statistical decision model. The results support the third model. If two equal-amplitude sine waves have equal detectability and are separated by several critical bands, the same detection for the combination is obtained if each individual component is reduced 1.5 db. Thus, the total energy in the complex is greater than either single component for a given detectability. [This research was supported by U. S. Air Force Contract AF 18(600)-1219. The author held a National Science Foundation Fellowship.]
Effect of Multiple Observations on the Detectability of Signals in Noise
Authors: Swets John A. , Shipley Elizabeth F. , Green David M.
Published: September 2005

The use of repeated presentations of a given signal event as an experimental technique in psychoacoustic studies permits the inference of several general properties of the hearing process. In addition to the immediate datum, i.e., the amount and rate of gain in detectability that results from repeated observations, this method provides information concerning the observer's ability to integrate over successive observations, the amount of noise generated within the auditory system, some characteristics of the frequency-selectivity process, and the effects of uncertainty about signal frequency. Data are presented from experiments that permitted five observations of each signal where the signal consisted of a pulsed tone in noise. Both independent noise, i.e., noise that was statistically independent from one presentation to another, and identical noise, i.e., noise that was exactly the same on each of the five presentations, were used. Using the independent noise, the detectability index d′ improved according to the square root of the number of observations. Using identical noise, an inference concerning the portion or total noise affecting the detection process that is of internal origin was made. Experiments designed to distinguish between two opposing models of the process of frequency analysis and to show the effects of uncertainty as to signal frequency are described. [This research was supported by funds provided under U. S. Air Force Contract AF 19(604)-1738 with the Operational Applications Laboratory, Air Force Cambridge Research Center, Bolling Air Force Base, Washington, D. C.]
Measurements of Hearing Threshold by Bone Conduction
Authors: Corliss Edith L. R. , Smith Ernest L. , Eanet June O. , Burkhard Mahlon D. , Koidan Walter
Published: September 2005

Measurements of threshold of hearing by bone conduction have been made for a group of young normal subjects. For each threshold, measurements of the mechanical impedance of the subjects foreheads and mastoids were taken. By use of the impedance data, thresholds obtained in terms of displacement amplitude also were converted into threshold force determinations. The results provide additional data for design of an artificial mastoid and serve as a source of tentative threshold values. Threshold data to be reported are for a driving tip of 2 cm diam applied with a static coupling force of 1 kg.
Space-Time Correlations of Random Noise above a Reflecting Plane
Authors: Lambert R. F.
Published: September 2005

A theoretical analysis of the space time correlations of random noise measured at two points separated a distance ξ and height h above a reflecting plane is formulated. The random-incidence correlation function is discussed for noise independent of angle of incidence, omnidirectional receivers, and for a reflection coefficient Γ = ±1. Certain aspects of the resulting anisotropy of the noise field are pointed out, but attention is directed toward predicting the influence of the receiving-point-aspect ratio 2h/ξ on the value of the measured correlation function. It is shown that the space-time correlation function for large-aspect ratios approaches in the limit a form identical with that resulting for zero reflection Γ = 0. Also, the possibility of reducing the value of the spatial-correlation function for band-limited noise by judicious choices of ξ and 2h/ξ is pointed out.
Acoustic Measurements in School Classrooms
Authors: Lane R. N. , Mikeska E. E. , Anderson C. D.
Published: September 2005

Acoustic measurements were made in the classrooms of twenty-two different school buildings in a study sponsored by the Acoustical Materials Association. Interior acoustical treatments in the rooms included full ceiling treatment, peripheral treatment, and no treatment. Measurements included reverberation time, definition, percentage articulation, transmission loss and noise reduction between rooms, followed by a questionnaire survey of the teachers who use the classrooms. The questionnaire returns indicated some interesting teacher impressions which will be reported, although not enough teachers were polled to treat their answers in a statistical manner.
On the Steady-State Transmission in Rooms
Authors: Schroeder M. R.
Published: September 2005

In 1935, E. C. Wente [J. Acoust. Soc. Am. 7, 123 (1935)] suggested an approach to the problem of finding a quantitative measure other than reverberation time for the acoustical quality of a room. The effect of reverberation time on acoustical quality was fairly well known at that time, and it had become apparent that reverberation time alone, though the most important room-acoustical parameter, was not sufficient to describe the acoustical behavior of an enclosure. Wente's approach consisted of measuring the steady-state transmission level from one point within a room to another as a function of frequency. He and other workers in the field suggested a variety of statistical quantities obtainable from such transmission curves as quality measures to supplement reverberation time. In this paper it will be shown that for large rooms these new parameters do not contain new information. In fact, the transmission curves can be proved to be members of an ensemble of statistical functions with a given amplitude distribution and a spectrum which depends only on reverberation time. Large rooms in the above sense are characterized by the fact that for each frequency in the range considered many normal modes are excited simultaneously. Assuming random distributions of the eigenfrequencies and the excitation coefficients [M. R. Schroeder, Acustica 4, Beih. 1, 456 (1954)] of the normal modes an inequality for the volume of the room can be derived which defines the range of validity of the statistical theory [M. R. Schroeder, Acustica 4, Beih. 2, 594 (1954)]. This theory has been confirmed by measurements in many concert halls, theaters, and broadcast studios [H. Kuttruff and R. Thiele, Acustica 4, Beih. 2, 614 (1954)].
Effect of a Slightly Irregular Boundary on the Coherence of Waveguide Propagation
Authors: Clay C. S.
Published: September 2005

The normal-mode solution of the problem of the radiation field of a simple harmonic source in a layered waveguide is extended to the case of small irregularities in the surface. The effect of the irregularities is to decrease the coherence of acoustical propagation and increase the attenuation. The theory is used to calculate the radiation field of a 147.8 cps simple harmonic source in about 20 in of shallow water over a thick layer of unconsolidated sediment. The calculations indicate that the effects of small surface roughness, i.e., rms waveheight about 12 m, are to increase the attenuation as a function of range and to decrease the mode-interference maxima and minima as evidence of the decrease in coherence. The experimental dependence of the acoustical pressure upon source distance similar to that calculated with the theory.
Reception Characteristics of a Linear Array in a Random Transmission Medium
Authors: Lord Gary E. , Murphy Stanley R.
Published: September 2005

The fluctuation of the response-signal intensity as a result of correlated phase and amplitude fluctuations is considered in connection with the performance of various common types of linear arrays. The results of Chernov's treatment of sound transmission through a random medium are used extensively for the formulation and solution of the problem of signal degradation by phase and amplitude fluctuations. This method of solution indicates that amplitude and phase fluctuations must be considered simultaneously. A generalization of Chernov's method shows that the bearing angle of the array, relative to the direction of propagation, is of importance in connection with the autocorrelation of the phase and amplitude fluctuations. The simultaneous inclusion of phase and amplitude fluctuations as well as bearing angle effects leads to quite general results for the computation of mean signal intensities, along with higher-order moments. Explicit expressions are given for the case of large values of the parameter D=4R/ka2, where R is the range, k is the wavenumber, and a is a characteristic correlation distance for the transmission medium.
Measurements of Backscattering from the Sea Surface
Authors: Richter R. M.
Published: September 2005

Measurements of ocean-surface backscattering were made off Nassau in 2500-f water using 2-lb TNT charges as acoustic sources. Analysis in octave frequency bands between 0.8 and 12.8 kc/sec shows surface backscattering decreasing down to grazing angles of 2° and confirms that scattering strength is proportional to frequency and wind velocity, with wind velocity becoming increasingly significant as grazing angle is decreased. Volume backscattering predominates over surface backscattering at low wind velocities and small grazing angles; the volume backscattering is presumed to be due to the presence of a layer of large numbers of microscopic marine life. General agreement was obtained on backscattering coefficients at grazing angles where previously published data are available for comparison.
Lumped-Parameter Design Formulas for Electrically Driven Tonpilz Strongly Loaded at One End
Authors: Pordes Fritz
Published: September 2005

The Tonpilz (two lumped masses linked by a lumped compliance) is loaded only on one end and mechanical losses are attributed to the loaded end. The compliant member as a whole, or a fraction of it, is either piezoelectric, electrostrictive, or magnetostrictive, and its electromechanically active portion is electrically lossless. Formulas developed in terms of dimensionless variables and their graphical plots allow one to arrive quickly at the optimum design(s) with given material constants for stated performance requirements. Considerable saving in time spent in computations is achieved.
Dynamic Mechanical Stability in the Variable-Reluctance and Electrostatic Transducers
Authors: Sherman Charles H.
Published: September 2005

Large displacement behavior of the variable-reluctance, and the mathematically equivalent electrostatic, transducing mechanism was analyzed in order to evaluate the importance of mechanical instability as a limiting factor in high-power sound projectors. Previous work by Hunt et al. had shown the existence of static instability. This paper first considers the effect of transients on static stability and then shows that instability can also occur under steady-state dynamic conditions, even when the system is statically stable. When the excitation is increased in order to increase the amplitude of the oscillations, the average displacement also increases, which leads to collapse of the gap. This interdependence of the oscillatory motion and the average displacement, intentionally excluded from linearized treatments, is the cause of dynamic instability. Detailed calculations show the conditions for instability for typical values of mechanical Q, polarization, and frequency. Under steady-state dynamic conditions, the average displacement can exceed the static limit of 13 the gap length, and the relative oscillatory displacement amplitude can reach 12 or more without collapse. Although such instability renders the transducer inoperative, the calculations indicate that it will seldom be a serious limitation.
Acoustic Direction Determination
Authors: Bugajski H. J. , Prout J. H.
Published: September 2005

A method has been devised to automatically compute and display the azimuth of an acoustic signal generating source. Three sensors are arranged in a given pattern so that a signal wave front traversing the pattern from any direction becomes part of a mathematical function with respect to time. The signals as obtained from the sensors are converted to time pulses and fed to three respective delay lines to which are connected many coincidence channels. The output of each coincidence channel is fed to a display board which designates the given azimuth of the signal wave front. Limited experimentation has shown that a narrow beam system, less than five degrees, is feasible. The system is not frequency sensitive below a given upper limit determined by the spacing of the sensors. The proposed method suggests many possible uses from a single directional unit to an elaborate omnidirectional system. Where a passive omnidirectional detection unit is desired, the time pulses from three sensors could be transmitted by wire or radio to the master computing unit and display some distance away. (Parts of this research were supported by Tri-service Contract No. DA-36-039-sc-52654.)
Echolocation: Measurement of Pitch versus Distance for Sounds Reflected from a Flat Surface
Authors: Bassett Irvin G. , Eastmond E. John
Published: September 2005

When sound containing many frequencies is reflected from a flat surface, an observer in the field of both the incident and reflected sounds hears a broad tone with an associated pitch that varies inversely with distance from the surface. Measurements made in three experiments have led to an explanation of the phenomenon. First, reference tones were sounded and positions located where their pitches matched those of a sound field produced with thermal noise. Again with thermal noise as a source, the field was carefully analyzed with a sound spectrograph. With an array of discrete frequencies used as the source in the third experiment, the regular array of standing waves thus produced gave rise not only to a pitch change at the barrier, but also to similar pitch changes at points in front of it. The pitch that is heard is a subjective tone produced by the ear from the sound pattern in front of the reflector. This pattern is caused by interference between the incident and reflected sounds. Although the phenomenon can be produced with a very narrow band of frequencies, it cannot be produced with a single pure tone. It is most easily noticed with frequencies ranging from 200 to 2000 cps and does not depend on frequencies above 10 000 cps.
Transient “Tilt” Distortion in Hearing Aids
Authors: Burnett Edwin D. , Jensen Thelma H. , Corliss Edith L. R.
Published: September 2005

When some hearing aids are exposed to acoustic signal trains with sharp onset and cutoff, the envelope of the acoustic output is tilted. Upon frequency analysis, this is found to correspond to generation of the gating frequency, which is actually below the normal pass band of the instrument. Subjectively, instruments exhibiting this “tilt” in response envelope sound noisy and distorted, although their frequency response may be fairly flat and their steady-state nonlinear distortion may be measured to be low. This appears to be a type of intermodulation test which is not critical with respect to pulse-repetition rate and is fairly insensitive to frequency. This work was supported by the Department of Medicine and Surgery of the Veterans Administration.
Role of Stimulus Frequency and Duration in the Phenomenon of Localization Shifts
Authors: Butler Robert A. , Naunton Ralph F.
Published: September 2005

Subjects were instructed to locate an auditory signal emanating from a concealed loudspeaker while an interference stimulus was being delivered monaurally. The apparent location of the signal presented in the presence of the interference was compared with that recorded in the absence of interference. In the first experiment, the signal frequency was set at either 500, 1000, 2000, 4000, or 8000 cps. The frequency range of the interference stimuli extended from two to three octaves below to an octave above the signal frequency. The results indicated that the apparent location of the signal source was displaced (pulled) toward the side receiving the interference most noticeably when the frequency of the latter was near that of the signal; a pulling effect was, however, exerted by interference stimuli whose frequencies were an octave or more below that of the signal. As the loudness level of the interference was increased, the magnitude of the pulling effect became greater. In a second experiment, both the signal and interference consisted of random noise and signal duration was varied systematically. The data showed that the pulling effect increased as the signal duration was lengthened from 0.5–100 msec. The interaction critical to the observed localization shifts is thought to be occurring centrally.
Frequency and Temperature Dependence of Internal Friction in Pure Copper
Authors: Mason W. P. , Bömmel H.
Published: September 2005

Measurements have been made at low strain amplitudes, of the internal friction, Q−1, for 99.999% pure copper for frequencies from 100 cy to 14 mc and from 4.2°K to room temperature. If one plots the Q−1 values against the log of the frequency for a given temperature, a linearly decreasing relation is obtained. At low temperatures the internal friction becomes very small. Although the loop length dependence agrees with the Koehler pinned loop model of internal friction, the present data shows that the frequency dependence does not. It is suggested that another source of dissipation is needed. The present data suggest that this is connected with the displacement occuring as the loop moves and is of a hysteresis nature. The frequency and temperature data show that the hysteresis lag in the motion cannot follow the applied stress at high frequencies or low temperatures.
Measurement of Dynamic Shear Impedance of Liquids at High Ultrasonic Frequencies
Authors: McSkimin H. J.
Published: September 2005

Further development of a shear reflectance technique reported on previously is here described [Phys. Rev. 75, 936 (1949)]. Shear waves at 30 mcps are reflected at a low grazing angle from a polished surface on a fused silica rod. Simultaneously waves are transmitted through a second path designed to provide a precisely matched reference channel with high relative stability. The specimen liquid when placed on the polished surface produces a change of amplitude and phase for the reflected wave from which the complex shear impedance can be calculated. Illustrative data is presented for a series of Dow Corning DC-200 silicone fluids having steady flow viscosities from 1.5 to 200 000 centistokes. At 39 mcps and 25°C relaxation effects are present for viscosity grades as low as 5 centistokes. The limiting stiffness (Voigt) is ∼2×107 dynes/cm2—in the range for rubber-like materials.
Propagation of Acoustic Transients in Water
Authors: Carome E. F. , Parks P. E. , Mraz S. J.
Published: September 2005

A technique is described for investigating the propagation of acoustic transients in liquids. Thick piezoelectric plates are employed as acoustic sources and detectors. The results of recent theoretical works on the transient response of such elements are extended to determine the relationships between the time profiles of the voltage applied to the source, the stress wave in the liquid, and the output voltage of the detector. Effects of transient processes in the field of a piston source also are considered. Results are presented of an experimental study of the propagation in water of low-amplitude pressure steps and impulses as narrow as 0.05 μsec. The data are strongly dependent on the parameters of the source-detector configuration. This limits the range of applicability of the technique, but its usefulness for studies of absorbing liquids is indicated.
Viscoelastic Constants of a Short-Chain Polymer
Authors: Hunter J. L. , Montrose C. J. , Shively J. H.
Published: September 2005

The viscoelastic constants of a short-chain polymer (a 10-atom polydimethylsiloxane) have been obtained by a combination of longitudinal-absorption and shear-reflection measurements. The measurements were made over a frequency range of 3–300 Mc/sec and a temperature range of −70° to +25°C. Measurement of the low-frequency limit of the absorption, combined with viscosimeter measurements, gave both the shear and compressional viscosities. Synthesis of the experimental absorption curves as the sum of a single-frequency shear-relaxation curve and a single-frequency compressional-relaxation curve yielded the shear- and compressional-relaxation times. The limiting shear modulus and relaxational compressional modulus could then be computed. The shear-reflection measurements were found to reduce with the value of the limiting shear modulus obtained from the absorption measurements.
Radio-Frequency Bridge Methods in Ultrasonic Interferometry
Authors: Carome E. F. , Gutowski F. A. , Schuele D. E.
Published: September 2005

The sound absorption coefficient in liquids may be shown to be simply related to the acoustic resistance of a liquid column [J. Acoust. Soc. Am. 29, 769 (A) (1957)]. It is possible to determine accurately the variations of this resistance by employing radio-frequency bridge techniques. Such a method has been used to measure the temperature dependence of the absorption coefficient of castor oil in the frequency range from 2 to 10 Mc. The experimental accuracy and consistency of the results indicate that this method may aid in removing discrepancies in the existing data. In addition, because of its extreme sensitivity the bridge-type detection system appears to be ideal for velocity and dispersion measurements.
Role of Time Cues in Pitch
Authors: Thurlow W. R.
Published: September 2005

It is pointed out that Nordmark's theoretical explanation of the effects on pitch of polarity reversal (of either one or the other pulse train of a double-pulse-train stimulus) is based on a very special set of assumptions. Furthermore, this theory predicts pitches that are not heard, when it is applied to certain “cophasic” pulses. An additional situation is noted where time cues in the nerve impulses are not reflected in the perceived pitch.
Effects of High Pass, Low Pass, and Band Rejection Filtering upon Articulation Test Scores
Authors: Kryter Karl D.
Published: September 2005

Articulation tests (CVC nonsense syllables) were conducted with a wide variety of HP and LP filter and gain conditions in an attempt to determine bands of speech frequencies that contribute equally to the intelligibility of speech. Comparison is made between our results and those reported by French and Steinberg (1947). In addition, tests with HP and LP filtering were run in which several portions of the range of speech frequencies were sharply rejected. It was found that with certain of these latter filter arrangements the articulation scores that were obtained greatly exceeded those predicted by any “articulation index” (Al) based on the simple addition of the contributions of “equal articulation bands.” There will be a brief discussion of the theory underlying different methods used for dividing the frequency range into bands supposedly contributing equally to speech intelligibility.
Prediction of Speech Intelligibility at High Noise Levels
Authors: Pickett J. M. , Pollack Irwin
Published: September 2005

Word articulation tests were conducted with three noise spectra (spectral slopes of −12, 0, and +6 db per octave) and with two speech spectra (spectral tilt of 0 to +6 db per octave) with noise levels up to 130 db SPL. Loss of intelligibility was observed at higher noise levels for all spectral conditions examined. The effective change in the speech-to-noise ratio (S/N)e defines the effect of high noise levels upon intelligibility. This quantity is that change in the S/N ratio which, at moderate listening levels, produces the equivalent change in intelligibility observed at high noise levels. To a first approximation, (S/N)e is primarily dependent upon the over-all noise level. For example, as the over-all noise level is increased from 90 to 125 db SPL, (S/N)e increases to 4.5 db (averaged over spectra and averaged over S/N ratio). However, (S/N)e is not invariant with spectra and S/N ratio. (S/N)e is generally higher at more favorable S/N ratios, and it is also somewhat lower when speech and noise spectra are parallel than when divergent. The use of (S/N)e for predicting intelligibility at high noise levels is compared with procedures suggested by French and Steinberg and by Beranek.
Computed Pressure-Time Waveforms for an Impulsive Source near a Fluid/Two-Layer-Solid Interface
Authors: Spitznogle F. R. , McLeroy E. G.
Published: September 2005

Computed waveforms for the problem of an impulsive source near a fluid/two-layer-solid interface are calculated, using a recently published theory [F. R. Spitznogle and E.G. McLeroy, J. Acoust. Soc. Am. 35, 1808–1815 (1963)], and compared with waveforms obtained in an experimental model.
Distortion of the Temporal Pattern of Speech: Interruption and Alternation
Authors: Huggins A. W. F.
Published: September 2005

In 1953, Cherry found that a subject can repeat virtually all of a continuous message that is switched alternately to his left and right ears, except at certain critical rates of alternation around 3 cps. The experiments reported here investigated the effect described by Cherry. In the first experiment, the intelligibility of continuous speech was measured as a function of rate of alternation, which ranged from 1–16 cps. Two such functions were measured, one using normal speech and the other using the same speech played back at slightly increased speed. Comparison of the two functions shows that, when the playback speed of the speech was increased, the rate of alternation that gave subjects most difficulty also increased by the same factor. Therefore, the effect cannot be ascribed to any processing time, etc., that is independent of the speech, but must occur because the speech reaches each of the listener's ears in segments, as a result of which some portions of the speech wave arrive in such a form that he cannot extract the cues from them. A second experiment compared the words that were correctly repeated by subjects who heard alternated speech with the words that were identified by subjects who heard only the signal for the left ear (interrupted speech) and the words that were identified by subjects who heard only the signal for the right ear (also interrupted speech, but complementary to the left-ear signal). It was found that the performance of subjects repeating alternated speech can be adequately described as the sum of the performances of the two groups of subjects who repeated interrupted speech, at all rates of alternation, if allowance is made for the additional context available to the alternation subjects, who heard both the left-ear signal and the right-ear signal, one in each ear.
Confidence Ratings, Message-Reception, and the Receiver Operator Characteristic
Authors: Decker Louis R. , Pollack Irwin
Published: September 2005

Can an observer rate the accuracy of his message reception? Apparently, yes. Listeners were presented with spondee words against a white noise background. For each word presented, the listener recorded his received message. Immediately thereafter, he assigned a confidence rating with respect to his accuracy of message reception. We find that the assignment of confidence ratings does not interfere with the accuracy of message reception. More important, the relative accuracy of message reception is directly related to the confidence rating. This relationship is relatively invariant over a range of speech-to-noise ratios. It may be noted that the rating procedure directly yields the entire trading relation between correct confirmations and false alarms—the receiver operating characteristic (ROC). The form of the ROC curves obtained by the rating procedure is independent of average word difficulty and is similar to that obtained by successive experiments with fixed acceptance criteria.
Sound Propagation in Dissipative Layered Media
Authors: Ryan R. P. , Eby R. K. , Williams A. O.
Published: September 2005

When sound is propagated from a point source in a layer of fluid, comparable in depth to the acoustic wavelength and overlying a much thicker layer of fluid with greater density and sound velocity, “wave-guide” or normal-mode effects and cylindrical spreading are to be expected, according to well-known theory. If the thicker layer absorbs sound, total internal reflection is destroyed, and the sound in the thin layer should be attenuated according to relations derived by Kornhauser and Raney [J. Acoust. Soc. Am. 27, 689 (1955)]. If the thicker layer is also shear-elastic, this attenuation should increase, through conversion of compressional into shear waves [K. Ergin, Bull. Seismological Soc. Am. 42, 349 (1952)]. These predictions have been confirmed by measurements in a water layer 0.5–2 cm thick, over a slab of rubber for which the density, absorption, and sound velocities were known. The frequency range was 55 to 600 kc. Vertical modal patterns of sound intensity and interactions of two modes were also found to agree with theory. (Supported in part by the Office of Naval Research.)
Validity of Thin-Plate Theory in Dynamic Viscoelasticity
Authors: Biot M. A. , Pohle F. V.
Published: September 2005

Resonance damping for a vibrating plate is investigated both according to the exact equations of dynamical viscoelasticity and the classical thin-plate equations derived in mechanics of materials. The plate is assumed as isotropic and homogeneous and no shear- or rotatory-inertia corrections have been included in the thin-plate approximations. Two types of materials are investigated that correspond to real and complex values of the bulk modulus. For each case, the complex shear modulus is μ(1+ig) and values of g up to 0.10 were used in the calculations. The two theories are in excellent agreement in a range of wavelengths as low as about ten times the thickness. It is found that thin-plate theory evaluates the damping more accurately than it does the static rigidity.
Alteration of the Bubble Pulse Amplitude of an Underwater Explosion
Authors: Hill Otto H.
Published: September 2005

The underwater detonation of a conventional high explosive is characterized by the production of a shock wave and an oscillating gas globe, containing primarily the reaction products, which in certain circumstances may result in the almost periodic generation of an acoustic pulse. If one postulates a scheme for altering the internal energy of the gas globe which will not affect the kinetic energy associated with the water, and which provides for internal pressure equilibration in a time sufficiently short that the actual radius of the bubble does not appreciably alter, then it is possible to obtain relations which yield the effective alteration of the bubble pulse amplitude as a function of the change in total energy produced in the bubble system, the time at which the alteration is made, and the initial history of the bubble.
Steady-State Behavior of the Dynamic Absorber—Addendum
Authors: Snowdon J. C.
Published: September 2005

Discussed theoretically is the manner in which the transmissibility of a vibrating item may be reduced by the attachment of a dynamic absorber, or by the attachment of three absorbers of staggered natural frequencies. It is demonstrated that the dynamic absorbers can provide significant isolation at frequencies of concern; yet the presence of the “compensating” resonant peaks normally associated with the use of a dynamic absorber may be avoided by employing small absorber damping and by damping heavily the resilient elements that support the vibrating item.
Model of a Rough Boundary as a Backscatterer of Wave Radiation
Authors: Patterson Robert B.
Published: September 2005

It is hypothesized that the backscatter of wave radiation from a rough boundary is the result of reflections from a large number of “facets” having random distributions of size and slope. This hypothesis developed into a mathematical model from which curves are computed for a number of values of mean size and rms slope. An explanation is offered for the lack of frequency dependence in reported backscatter measurements. The model is also fitted to some previously reported measurements of the backscatter of sound from the deep-ocean bottom.
Measurement of Auditory Density
Authors: Guirao Miguelina , Stevens S. S.
Published: September 2005

Auditory density refers to the apparent compactness, concentration, or hardness of a sound. An attempt was made to determine directly the form of the density surface by the method of magnitude estimation with both pure tones and bands of noise (quarter-octave). For both tones and noises, density grows as a power function of sound pressure. The values of the exponents decrease with frequency, and the two families of power functions converge toward a common point near about 150 dB SPL. The equal-density contours turn out to be straight lines in a plot of SPL vs log frequency. The general slope of the equal-density contours for pure tones was verified by a direct-matching procedure.
Acoustic-Image Lateralization Judgments with Binaural Transients
Authors: Sayers B. McA. , Toole F. E.
Published: September 2005

Experiments on the extent of lateralization of sound images established by the binaural interaction of clicks with clicks or click pairs are reported. It is shown that two images formed by the interaction of a click with each member of a click pair can be readily identified. It is argued that studying the trajectory of judged image position as a function of interaural time delay clarifies certain aspects of the perception of acoustic transients, and a range of typical results with the technique is shown.
Energy per Unit-Area Spectrum of the Shock Wave from 1-lb TNT Charges Exploded Underwater
Authors: Stockhausen J. H.
Published: September 2005

Measurements were made of the energy per unit-area spectrum level of the shock wave 100 yd from 1-lb TNT charges exploded underwater. Over the frequency range covered, 0.1–25 kc/sec, the measurements were in agreement with values calculated, using peak pressures and time constants reported by Arons. In particular, the decrease in spectrum level with increasing frequency of 6 dB per octave at high frequencies, characteristic of pulses with short rise times, continued up to the high-frequency limit of the measuring equipment.
Directional Localization of Sound from Two Plane-Wave Sources
Authors: Igarashi Y. , Beck L.
Published: September 2005

The direction of the apparent angle of arrival of a sound image resulting from two plane wave sources impinging on two receiver elements is considered theoretically. For equal amplitude sources, the image shifts discontinuously from an average position between the sources to a point outside the source bounds and back again over a relative phase shift of 2π. For unequal-amplitude sources, angle of arrival is a continuous function of phase. Increase in aperture angle for equal-amplitude sources results in an increase in duration but decrease in magnitude of out-of-boundness. For unequal sources, the magnitude increases and then decreases. The average angular indication is to the greater amplitude source, independent of amplitude fluctuation. For n sound sources, the phenomena of angular discontinuity and out-of boundness may also be expected.
Neutralization of Stimulus Bias in Auditory Rating Scales
Authors: Pollack Irwin
Published: September 2005

Several techniques are examined for neutralizing the effects of stimulus bias in rating scales for sound level and auditory frequency. The techniques are based upon iterative procedures of experimentation, in which the results of the first ratings provide the stimuli for the second ratings; the results of the second ratings provide the stimuli for the third; etc. Unbiased rating scales are quickly achieved with these procedures.
Discrimination Limen for Loudness under Varying Rates of Intensity Change
Authors: Wolsk David
Published: September 2005

Two studies have been conducted on the influence of the rate of auditory-intensity change upon a subject's ability to discriminate that change. In Experiment 1, the stimulus intensity changed gradually through time. Complete psychophysical functions were obtained for four subjects at five rates of change between 2 and 150 dB/min. To control for possible differential auditory-fatigue effects, a stable level of fatigue was maintained throughout the trials. The slowest rate of change was the only one that produced results significantly different from the other rates and this was so for only two of the four subjects. In Experiment 2, a warbling type of intensity variation was used with four warble rates between 0.3 and 3.0 beats/sec. The rate of change of the warble amplitude was adjusted for each warble rate to serve as a compensation for the fewer number of warble cycles presented in a given observation time with the slower warble rates. This control has apparently not been used before in two previous similar studies whose results indicated a very definite decrement in discrimination as the warble rate decreased. The results from this experiment showed no significant effects on the DL from varying the warble rate.
Acoustic Bulk Parameters of Random Volume Distributions of Small Scatterers
Authors: Twersky Victor
Published: September 2005

General approximations for the “bulk parameters” of a uniformly random homogeneous distribution of relatively arbitrary scatterers are applied to obtain explicit results for the range where the significant dimensions of the scatterers are small compared to wavelength. We consider “slight scatterers” of arbitrary shape, symmetrical scatterers (plane slab, circular cylinder, and sphere) of arbitrary density and compressibility, elliptic cylinders, and ellipsoids (either aligned or averaged over orientations). For all cases, we give explicit results for the density and compressibility (or for the index of refraction and acoustic impedance) in terms of the isolated scatterer parameters. The range of applicability of the results should correspond essentially to that of “Clausius-Mossotti” type results for analogous electromagnetic problems.
Random Vibration of an Oscillator with Nonlinear Damping
Authors: Crandall Stephen H. , Khabbaz Ghassan R. , Manning Jerome E.
Published: September 2005

The damping force acting on a simple oscillator is taken as a nonlinear function of velocity. Although this implies a frequency-dependent damping mechanism, the model can be used to represent frequency-independent internal damping of metals, provided the oscillations are restricted to a narrow band of frequencies. Response statistics are obtained when the excitation is a stationary wide-band random process. The expected fatigue damage is calculated for the case where the member that provides the nonlinear damping is also subject to fatigue failure. A perturbation method indicates that amounts of nonlinearity that have small influence on the rms response level can result in large increases in fatigue life.
Ultrasonic Absorption in Water at Finite Amplitudes
Authors: Barnes R. P. , Beyer Robert T.
Published: September 2005

The total energy absorption has been measured in all ultrasonic beam in water by a modified radiation-pressure technique, in which the radio-frequency source transducer is square-wave modulated at an audio frequency. A microphone is then used to detect the audio variations in the radiation pressure produced by the modulation. Measurements at 5.0, 11.6, and 12.9 MHz are reported and compared with expected values from perturbation analysis. Satisfactory agreement is obtained.
Spectral Broadening of Acoustic Reverberation in Doppler-Shift Fluid Flowmeters
Authors: Green P. S.
Published: September 2005

The measurement of fluid flow velocity by observations of the Doppler frequency shift in reverberated ultrasonic waves is often plagued by a poor signal to noise ratio, owing to a low concentration of scatterers in the fluid. The extent to which this ratio can be improved by electrical filtering depends upon the spectral width of the return signal. Several mechanisms that cause spectral broadening of reverberated acoustic signals are investigated herein. An example is given to indicate the effect of each mechanism on a typical Doppler-shift flowmeter intended for measuring ocean currents. It is concluded that, with certain restrictions, it is possible to measure accurately flow velocity under conditions of uniform flow even when the fluid contains “relatively few” scatterers.
Calculation of Coupling Effects in Pritchard's Array
Authors: Eichler Ewald
Published: September 2005

Coupling impedances as given by Pritchard [J. Acoust. Soc. Am. 32, 730 (1960)] are applied to his hexagonal array for simply resonant array elements. With decreasing acoustical distance between elements, the element velocities diverge; the output power of the array fluctuates and decreases.
Signal Detection by Arrays in Noise Fields with Local Variations
Authors: Usher Theron
Published: September 2005

The signal-detection capabilities of an array that is essentially DIMUS in nature are analyzed for the situation in which the background-noise power from hydrophone to hydrophone is not the same. The signal to be detected is assumed to be a plane-wave random time function. The signal power at different hydrophones is assumed to be constant. The performance of the DIMUS system, with infinite clippers, is compared to that for a similar array with purely linear signal processing. Results indicate that the performance of the system with infinite clippers is generally superior on a signal-to-noise basis and on the basis of normalized signal output.
Perception and Retention of Verbal Information Presented during Auditory Shadowing
Authors: Mowbray G. H.
Published: September 2005

Nine subjects listened through one earphone of a binaural headset to 50-word lists of common English words read to them at a rate of two words per second. They repeated the words that they heard while listening for an occasional word that might or might not be presented on the other earphone. This word, should it appear, was to be remembered until the conclusion of the 50-word list, at which time it was to be recalled. No more than three target words were presented with any one 50-word list for shadowing. The results indicate that shadowing performance is almost totally disrupted at the point of insertion of the target word, whether the target word is finally correctly remembered or not. Memory for the target word deteriorates as some function of the time between presentation and recall. Since time between presentation and recall and amount of intervening material between presentation and recall are directly correlated, it is impossible to say with certainty that the recall data support a decaying-trace theory of immediate memory or an interference-type theory. The results of a similar study using visual target words are cited to lend support to the position that an interference-type theory is to be preferred in this case. Finally, these data further confirm the validity of the concept that man's perceptual system is basically a single-channel one with a limited information-handling capacity.
Acoustic Power Radiated by an Infinite Plate Excited by a Concentrated Moment
Authors: Thompson William , Rattayya J. V.
Published: September 2005

An expression is derived for the acoustic power radiated by an infinite uniform isotropic plate excited by a time-harmonic moment acting at a point on the plate. The effect of radiation loading is included. Results are obtained that are valid below the coincidence frequency.