bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluid Motion in Cochlear Models
Authors: Tonndorf Juergen
Published: September 2005

Békésy-type, transparent models of the cochlea were used in the present study. Suspensions of aluminum dust in glycerin-water solutions provided frequency responses sufficiently high so as to improve the display of Békésy's “eddies” and to allow demonstration of particle motion within the “perilymphatic” fluid. The membrane displacement was found to vary with frequency, whereas the revolving velocity of the dc eddy currents varied with the square of frequency. The “bed” of each eddy was narrowest along the membrane and much wider elsewhere, as evidenced by a reciprocal variation in speed, ac particle motion (in response to pure-tone signals) was longitudinal proximal to and trochoidal (elliptical) alongside the membrane. In general, the elliptical orbits flattened out with distance from the membrane or from the eddy's mainstream upon which particle motion was superimposed. Along the membrane, the trochoidal pattern conformed to the changes of the traveling wave, while in the rebound portion of the eddy it became almost longitudinal. No ac particle motion was seen to occur beyond the eddy. A phase lag of ac particle motion, totalling 360°, accumulated gradually throughout the eddy so that particles in the inbound and rebound portions of the eddy were in phase opposition to each other. Orbits of ac particle motion resulting from stimulation by complex tones were observed also and analyzed as Lissajou figures. A given phase relation between the partials of complex orbits remained unchanged throughout the eddy, although their relative magnitude did alter. In the case of beats, two separate patterns were observed in response to the beat frequency and to the intermediate frequency. This indicated that the model reacted nonlinearly to such stimulation.
Acoustic Intensity Anamolies: Comments on a Paper by Pedersen
Authors: Stewart Kenneth R.
Published: September 2005

By use of a ray acoustical model of the ocean with linear sound speed gradients, the intensity is calculated when a ray is horizontal at a layer interface.
Comment on “Aid to Music Composition Employing a Random Probability System”
Authors: Barbour J. Murray
Published: September 2005

A recently published article states that “a composing machine employing a random probability system based upon Stephen Foster songs may be developed ….” Later the authors make the categorical statement: “The resulting music [i.e., produced by the machine], while new, sounds like Stephen Foster music.” However, because of many errors in notes and rhythms and a failure to comprehend musical design, the output of the machine bears no resemblance whatever to the songs of Stephen Foster. A possible alternative method of mechanically simulating Foster's style is suggested.
Solid Mixtures with Specified Impedances and High Attenuation for Ultrasonic Waves
Authors: Lutsch A.
Published: September 2005

The manufacturing procedure for mixtures containing a resin, tungsten, and rubber powder, are described. The attenuation and elastic constants are measured at 1 Mc and compared with values predicted by an earlier theory.
Spoken Digit Recognition Using Vowel-Consonant Segmentation
Authors: Sholtz P. N. , Bakis R.
Published: September 2005

A procedure has been developed for recognition of spoken digits by means of digital computer simulation. Using power spectra computed at 10-msec intervals, the words are segmented into vowels and consonants. Vowels are then classified into one of 11 categories by a multivariate statistical decision method operating on approximations of the measurements. Consonants are classified into one of three categories by means of an empirically derived decision tree. Recognition is then performed by means of a dictionary search. When tested on a sample of 493 words spoken by 50 speakers, and with the internal dictionary adjusted for optimum results, 97% of the words were identified correctly. It appears that this procedure is more tolerant of interspeaker variations than those previously reported.
Measurement of the Distortion of Finite Ultrasonic Waves in Liquids by a Pulse Method
Authors: Ryan R. P. , Lutsch A. G. , Beyer R. T.
Published: September 2005

An rf pulse system is described for investigating progressive distortion of finite amplitude waves propagating in liquids. The system employs pulses short enough to avoid reflections but long enough to approach continuous wave conditions. A 25-Mc quartz crystal backed by fused quartz serves as a nonresonant receiver for the first few harmonics of the 2.58-Mc working frequency. Harmonic content is determined by Fourier analysis of waveform photographs, or by use of a heterodyne analyzer having bandwidth adequate to pass the pulse envelope. For an initially sinusoidal wave of 3.0 or 6.0 atm pressure amplitude in water, curves are shown tracing the decay of the fundamental and the growth and decay of harmonics through the fourth, to a propagation distance of 40 cm. Results are in good agreement with published theory within the region of convergence of the latter.
Long-Range Shallow-Water Signal-Level Fluctuations and Frequency Spreading
Authors: Mackenzie K. V.
Published: September 2005

The fluctuation of the received sound for frequencies of 350, 700, 1200, and 2400 cps was studied for transmission over flat 60-fathom sand and 50-fathom sandstone bottoms out to ranges of 15 miles. The received sound fluctuated over a range of 50 db. In general, the amplitude distribution was neither Gaussian nor Rayleigh. No significant correlation was found between the outputs of the receiving hydrophones which were separated vertically by 90 or more feet. The frequency was spread due to transmission and the relative power P is related to the half-width of the spectra |f − f0| from 350 to 2400 cps by P = bf0|f − 0|−3, where b = (7.7±0.8)×10−6 (cps)2 for the sand bottom and (3.9±2.7)×10−6 (cps)2 for the sandstone bottom. Special measurements indicated no significant asymmetry between the spectra above f0 from that below f0.
Boundary Losses Associated with Acoustical Streaming
Authors: Hueter T. F.
Published: September 2005

The response of an acoustic thermocouple probe to ultrasonic pulses of 0.005 to 1 sec duration exhibits a sharp transition from low to high boundary dissipation at a critical sound level which depends on frequency. This transition is related to acoustical streaming phenomena in the boundary layer of the thermocouple wire. A connection seems to exist between the onset of turbulence and the formation of cavitation nuclei, although gross cavitation has not been observed.
Tapering a Bar for Uniform Stress in Longitudinal Oscillation
Authors: Bies David Alan
Published: September 2005

A cross-sectional taper is described which provides a bar with the possibility of uniform stress in longitudinal oscillation. It is shown that this kind of motion is a special case of a more general kind of motion in which it is possible by properly terminating the bar to make the displacement and the stress functions related polynomials of any desired order. A theory which describes the behavior of the bar in longitudinal motion is presented and compared with the results of experiment.
Underwater Hearing Thresholds
Authors: Hamilton P. M.
Published: September 2005

Underwater hearing thresholds were measured at frequencies of 250, 500, 1000, 2000, and 4000 cps on four Aqualung equipped divers with normal hearing in air. In the frequency range investigated, the minimum audible fields underwater are from 44 to 60 db greater than the minimum audible fields in air, and the shape of the threshold vs frequency curve is different.
The Condenser Microphone as a Displacement Detector Calibrator
Authors: Koidan Walter
Published: September 2005

The absolute calibration of a variable capacitance type displacement detector was performed by using the diaphragm of a condenser microphone as a reference moving surface. The detector was calibrated by coupling its associated probe to the front end of the microphone to detect the variation in capacitance between the diaphragm and the probe, when the diaphragm was driven by applying an electrical signal to the microphone terminals. Computation of the displacement detector response was made in two ways: one based upon the reciprocity relationship in a set of two linear equations describing the microphone as a reversible transducer; the other, upon the acoustical impedance of a cavity with rigid walls. Measured values of the displacement detector response are plotted from 10 cps to 40 000 cps.
Regarding the Sound Quality of Violins and a Scientific Basis for Violin Construction
Authors: Meinel H.
Published: September 2005

Response curves, important both for steady sound and transients, give a far-reaching insight into the objective characteristics of violins: good ones exhibit large amplitudes at low frequencies and small ones at high frequencies, a broad minimum near about 1500 cps, and larger amplitudes between about 2000 and 3000 cps. The musical subjective significance of these physical properties is mentioned briefly. In general, the sound pressure radiated from a violin follows the inverse-distance law, being independent of frequency. The influence of wood thickness is very important, that of the varnish is comparably small. Pine has a greater damping at high frequencies than at low frequencies. This seems to be a good acoustical reason for making important parts of stringed instruments of pine. Sapwood is better than heartwood. Similarly, some kinds of varnish produce more damping at high frequencies than at low frequencies. If a resonance curve is to be imitated in detail, it is necessary to change carefully the wood thickness of certain parts of the violin body. The applicability of present-day scientific knowledge to the construction of violins is here outlined.
Sensitivity to Unidirectional Frequency Modulation
Authors: Sergeant Russell L. , Harris J. Donald
Published: September 2005

Responses to glissando at 1500 cps at a 50-phon level using trained and untrained listeners are analyzed. The sensitivity to this type of frequency modulation is surprisingly good. A constant of 5 cps change emerges indicating that sensitivity depends on a linear relationship between rate of change and stimulus duration. This constant is of the same order of magnitude as the traditional DL for pitch memory. The low observed relationship of glissando to either pitch discrimination by the constants method or with sensitivity to the presence or absence of sinusoidal frequency modulation indicates that probably a third distinct pitch factor is represented.
Auditory Intensity Discrimination as a Function of Stimulus Presentation Method
Authors: Loeb Michel , Hawkes Glenn R.
Published: September 2005

Relative differential intensive limens were obtained at three frequencies and two intensities for three stimulus patterns involving fluctuation of a steady tone and three patterns involving separate stimuli. The same observers were utilized in all cases; in Experiment I, signals were presented through earphones. Somewhat lower thresholds were obtained for fluctuating intensity patterns than for separate stimuli patterns, thresholds tended to be lower at the higher intensity level, and thresholds were lower for patterns allowing greater opportunity for comparison within the patterns. When similar thresholds were obtained for patterns presented through speakers (Experiment II), thresholds were smaller, the influence of intensity was smaller, and the influence of (presentation) pattern type was less consistent. Significance of the findings is discussed.
Amplitude Contour Display of Sound Spectrograms
Authors: Prestigiacomo A. J.
Published: September 2005

Sound spectrographs typically displayed complex signals, such as speech, on teledeltos (facsimile) paper with frequency and time plotted along the ordinate and abscissa, and shades of gray to indicate the relative intensity of the frequency components. The gray scale is usually limited by the teledeltos paper to a marking range of 12 dB, whereas the signal may have amplitude variations of 40 to 50 db. A voltage quantizer has been designed which will plot equal-level contours in the frequency/time plane. The equal-level plateaus were selected at 6-dB intervals over a 42-db range. Gray-scale compression is also obtained as a by-product of this quantizer to shade each contour level such that a 42-dB change in signal level causes a 12-dB change in marking voltage. A discussion of the design and operating principles is given so that one can incorporate the circuit into a spectrograph or modify the circuit for other applications.
Validation of the Articulation Index
Authors: Kryter Karl D.
Published: September 2005

French and Steinberg proposed the basic concept and method of calculating the Articulation Index (AI) approximately 15 years ago. Although improvements and modifications of AI have been made over the years, it has not been generally accepted, perhaps because of insufficient evidence as to its validity. On the basis of studies reported in the literature and on new studies herein reported, it is shown that AI is a valid predictor of the intelligibility of speech under a wide variety of conditions of noise masking and speech distortion.
Investigation of the Fluctuating Forces Acting on a Stationary Circular Cylinder in a Subsonic Stream and of the Associated Sound Field
Authors: Keefe Roger T.
Published: September 2005

The principal parameters governing the generation of almost pure tones (Aeolian tones) by a roll in a wind have been identified and measured, guided by a theory due to Etkin. In particular, the connection between rms fluctuating lift and the correlation length of the shedding vortices has been recognized, and light has been shed on both by measurements. This has been a group program and has been partially reported elsewhere. Reported herein are the comprehensive measurements of the fluctuating forces on the rod and of the sound field they generate. Sealing or unsealing the ends and the addition of disks at various spacings are found to have major effects. Substitution of the measured parameters in the theoretical equation yields sound pressures in acceptable agreement with experiment. The experiments covered a Reynolds number range of approximately 3000⩽Re⩽100 000.
Perturbation Solution for the Axisymmetric Vibrations of Prolate Spheroidal Shells
Authors: Shiraishi N. , DiMaggio F. L.
Published: September 2005

The nontorsional extensional axisymmetric modes and frequencies of elastic prolate spheroidal shells are obtained by a perturbation solution which converges rapidly for small ratios of major to minor axis.
Determination of Far-Field Characteristics of Large Underwater Sound Transducers from Near-Field Measurements
Authors: Baker D. D.
Published: September 2005

It has recently become necessary to find a way to determine far-field characteristics of large underwater sound transducers from measurements made in the near field of the transducer (at ranges small compared to the transducer dimensions). It is possible to compute far-field directivity patterns and source levels from pressure amplitude and phase measurements made in the near field. This can be done by using Kirchhoff's formula with a simple approximation for the normal component of the pressure gradient. Pattern computations were made on line, plane-array, dipole, and line-and-cone transducers from measurements made in open water. Extensive pattern and source level computations were made on a large, multistave cylindrical transducer from measurements made in open water and in a highly reflective tank. Agreement with measured far-field patterns and source levels was good throughout and was within ±1 dB in the more recent work with the cylindrical transducer. Particularly significant is the fact that successful measurements were made in a tank of diameter only 2.9 times that of the transducer. These measurements were made near the leading edge of the received pulses in order to avoid interference due to reflections. Preliminary work on a simplified near-field test for a cylindrical transducer has also been done. Such a test would enable one to use near-field data to make certain judgments about the far-field performance of a transducer without computations.
Extension of the Theory of Signal Detectability to Matching Procedures in Psychoacoustics
Authors: Sorkin Robert D.
Published: September 2005

The theory of signal detectability is used to analyze experiments where the observer's task is to state, after two signal presentations, whether the signals were the same or different. A model is suggested for predicting human performance in auditory “matching” tasks using data from detection and discrimination experiments. Three experiments are discussed which lend support to the model's application. The first, a two-alternative forced-choice, pulsed-carrier experiment, serves to determine each observer's efficiency. The efficiency η is assumed constant provided certain observation interval and signal characteristics are held fixed, as they were during the entire experimental sequence. The second was a simple matching task, where the first observation interval always contained specified signal and the second sometimes contained a signal identical to the first. In the third experiment the signal appearing in the first interval was randomly chosen from a set of possible signals, thus removing the long-term memory requirement, and necessitating a comparison observation based on both intervals. The results are consistent with the assumption of constant efficiency across different tasks, and close agreement with the model's predictions for matching performance is demonstrated. Also discussed are stone interesting side issues raised by the experimental data which are relevant to current use of the matching procedure in other areas of psychology. Consideration is made of possible further applications of the matching procedure, such as in determining the value of Θ in recognition experiments.
Growth of Loudness and Its Relationship to Intensity Discrimination under Various Levels of Auditory Fatigue
Authors: Riach W. , Elliott D. N. , Reed James C.
Published: September 2005

The relationship of growth of loudness to differential sensitivity for intensity has not been experimentally established. Alteration of the rate of loudness growth by auditory fatigue provided the means whereby this relationship could be systematically investigated. Loudness growth was determined by the method of magnitude estimation. Difference thresholds for intensity were obtained using a 3/sec amplitude-modulated tone. Loudness growth and intensity difference thresholds were determined under normal conditions and under three levels of auditory fatigue, i.e., TTS's of 10, 20, and 30 db. In the area of hearing where recruitment manifests itself, it was found that loudness growth under any of the three fatigue conditions differed significantly from normal, and that, as severity of fatigue increased, there were significant systematic increases in the rate of loudness growth. On the other hand, while the intensity difference thresholds under any of the three fatigue conditions differed significantly from normal, there was no significant difference in the thresholds as severity of fatigue was increased. It is obvious that the relationship of growth of loudness to differential sensitivity for intensity is of only a most general nature.
Acoustic Refraction and Scattering with Compliant Elements. II. Analysis
Authors: Toulis W. J.
Published: September 2005

The characteristic behavior of a compliant tube to underwater sound is predicted with sufficient accuracy by treating the compliant tube as a clamped-clamped beam and assuming that the distribution of vibration on the beam is independent of the interaction with the fluid medium. This procedure leads to an index of refraction that depends at low frequencies only on the diaphragm volume displacement and the concentration of compliant tubes. The radiation load plays a more significant and variable role in the reflection of sound since it determines, part, the compliant tube resonant frequency and, therefore, the frequency where practically complete reflection is theoretically possible. Since the radiation load is a complex function of the frequency and the dimensions of the array, a graphical method is suggested in connection with an equivalent circuit to determine the reflection coefficient as a function of frequency. The success of this method requires, in addition, a compatible definition between the radiation load and the mechanical impedance of a compliant tube.
Precise Calibration of Sea-Going Velocimeters
Authors: Lord Norman W.
Published: September 2005

A method is suggested for separating sound propagation and instrumental delay times. In addition, the effect of environmental temperature changes on the circuit operation is measured.
Acoustic Ambient Noise in the Ocean: Spectra and Sources
Authors: Wenz Gordon M.
Published: September 2005

The results of recent ambient-noise investigations, after appropriate processing, are compared on the basis of pressure spectra in the frequency band 1 cps to 20 kc. Several possible sources are discussed to determine the most probable origin of the observed noise. It is concluded that, in general, the ambient noise is a composite of at least three overlapping components: turbulent-pressure fluctuations effective in the band 1 cps to 100 cps; wind-dependent noise from bubbles and spray resulting, primarily, from surface agitation, 50 cps to 20 kc; and, in many areas, oceanic traffic, 10 cps to 1000 cps. Spectrum characteristics of each component and of the composite are shown. Additional sources, including those of intermittent and local effects, are also discussed. Guidelines for the estimation of noise levels are given.
Velocity of Cavitation Bursts
Authors: Darner Charles L.
Published: September 2005

A sensitive aural method for detecting the onset of cavitation developed by a resonant high-frequency transducer and a method of determining the velocity of the cavitation bursts are discussed.
Printout System for the Automatic Recording of the Spectral Analysis of Spoken Syllables
Authors: Olson Harry F. , Belar Herbert
Published: September 2005

A printout system has been developed which automatically records any one of over a trillion different quantized analyses of a spoken syllable. The main purpose is research toward improved methods of recognizing speech by machines. However, other applications for the digitized transmission of speech are also indicated. Results of tests made are analyzed and different approaches to the decoding problem are presented.
Studies of Nasal Consonants with an Articulatory Speech Synthesizer
Authors: Hecker Michael H. L.
Published: September 2005

An electrical analog of the nasal cavities has been designed for use in conjunction with a dynamically controllable analog of the vocal tract [G. Rosen, J. Acoust. Soc. Am. 30, 201 (1958)]. The acoustical coupling between vocal tract and nasal cavities is electronically variable. Listening tests are conducted to determine the most suitable vocal-tract configurations for producing nasal consonants in consonant-vowel and vowel-consonant syllables. Other listening tests determine the most suitable patterns of temporal variables for these syllables. In general, it is found that more natural-sounding syllables are obtained when the velopharyngeal coupling varies slowly with time compared to changes in vocal-tract configuration. The results compare favorably with recent cineradiological data, and are interpreted to support the view that studies with articulatory synthesizers reveal important details about the production and perception of natural speech. The experiments demonstrate that speech can be synthesized from articulatory information in a straightforward and natural manner.
Sonic Structure of the Mesosphere
Authors: Webb Willis L. , Jenkins Kenneth R.
Published: September 2005

Temperature and wind data up to altitudes of 200 000 ft have been obtained with meteorological rockets at various locations over North America during the seasons of 1959 and 1960. Seasonal and geographical variations of the atmosphere's acoustical structure, as derived from these data, are illustrated. The thermal and flow effects on the sonic profiles in the lower mesosphere are pointed out. Data in the form of individual cases of interest and seasonal summaries for several locations are presented.
Effects of Auditory Fatigue upon Intensity Discrimination
Authors: Elliott D. N. , Riach W. , Silbiger H. R.
Published: September 2005

Although a majority of auditory fatigue studies have utilized the TTS as the primary index of change in functioning of the auditory system, it is clear that the threshold of audibility is not a completely adequate indication of the auditory system's functional status. Indices of discrimination, for example, are not related in any systematic fashion to the threshold of audibility, since various pathological conditions of the auditory system are reflected differentially in measures of the threshold of audibility and measures of differential thresholds. In the present study changes in the intensity discrimination threshold (IDT) as well as in the threshold of audibility have been determined. Significant decreases in the IDT were found to follow fatiguing exposure, such changes being related in a negatively decelerated manner to the TTS. The extent of the change in the IDT as a function of fatigue was found to be inversely related to the SPL of the signal to be discriminated. As a result of these two relationships the range of IDT's as a function of signal strength was markedly decreased for the fatigued ear. In addition, no relationship was found between normal IDT's and size of the recording pen excursions bracketing the threshold of audibility, or in the change in the size of these two measures as a function of fatigue.
Loudness Summation and Spectrum Shape
Authors: Scharf Bertram
Published: September 2005

The loudness of three-tone complexes centered at 2000 cps was studied as a function of the intensity relations among the three components. Two types of spectra were investigated: (1) peaked spectra, in which the intensity difference between the middle component and the less intense side bands was varied from 0 to 35 rib, and (2) sloped spectra, in which the slope of the connected heights of the three spectral lines of the complex was varied from 0 db per octave to + and −∞. Generally, three-tone complex whose over-all spacing was greater than a critical band was loudest, at a given SPL ,when its spectrum was flat, i.e., when the components were equally intense and, more important, equally loud. Complexes whose over-all spacing was slightly less than a critical band changed little in loudness as a function of spectrum shape. The results are related to the assumption that the loudness of a complex sound is the sum of the loudnesses of the component critical bands.
Ultrasonic Absorption in Toluene in the Kilocycle Region
Authors: Cerceo M. , Meister R. , Litovitz T.
Published: September 2005

Investigators have studied the absorption of sound energy in toluene from 30 kc to 200 Mc in an effort to determine the causes of the excess absorption. The results to date have raised many puzzling questions. For example, Verma and Yeager (private communication) have reported a resonance peak at 50 kc, the existence of which is quite difficult to explain. R. T. Beyer reports a relaxation peak at 150 kc, the mechanism of which is not clear. We have made ultrasonic absorption measurements in toluene using the reverberation method and the pulse method over a frequency range from 150 kc (overlapping Beyer's [J. Acoust. Soc. Am. 27, 1 (1955)] frequencies) to 55 Mc and a temperature range from 6° to 44°C. The high-frequency attenuation is studied as a function of temperature, and it is found that the temperature dependence is different from that reported by G. S. Verma [J. Chem. Phys. 18, 1352 (1950)]. The results in the kilocycle region show that the absorption per wavelength has a resonance type peak at approximately 210 kc independent of temperature with a magnitude that increases with increase in temperature. The Q of this loss mechanism is about the same as the Q of the resonance type loss reported by Verma and Yeager in the 50-kc region. The position and magnitude of the peak at 210 kc is unaffected by the introduction of ethyl alcohol as an impurity up to concentrations of 10% by volume.
Correlation Loss in Echo Ranging
Authors: Weston D. E.
Published: September 2005

In a correlation echo-ranging system, many features of any correlation loss may be predicted without considering detailed mechanisms. Correlation loss may be due to both a spreading time delay, τ and a spreading in Doppler-frequency shift φ. First, these effects are considered separately, for one-way transmission and for two-way transmission or echo ranging. Generally, the total correlation loss may be regarded as due to a two-dimensional spreading in the τ-φ plane. When τ and φ spreading are both significant, the loss for an FM pulse is much less than that for a noise pulse. The excess of the two-way loss over the one-way loss may often be about 112 dB for an FM pulse and 3 dB for a noise pulse.
Some Characteristics of 25-cps Shallow-Water Ambient Noise
Authors: Willis Jack , Dietz F. T.
Published: September 2005

Ambient-noise measurements in a 1-octave band centered at 25 cps were made at a shallow-water location in Narragansett Bay, Rhode Island, using a velocity-sensitive transducer. Measurements over one month showed that the predominant factor influencing the ambient-noise levels was the tidal current. The noise levels reflected the effects of both the lunar and solar tides.
Binaural Interactions of Three Clicks
Authors: Guttman Newman
Published: September 2005

Listeners tracked the trajectories of auditory images produced by a group of three clicks, of which two were temporally fixed in opposite ears and the third ranged freely in time. The fixed clicks were positioned in three time- and level-difference combinations to produce a centered image. The results indicate that the temporally variable click interferes with the fixed-clicks image when it leads or lags by as much as approximately 25 msec. The leading interference is plausibly explained by monaural forward masking, but the lagging interference is puzzling, partly because it seems inconsistent with results of other experiments in which the two fixed clicks are in one ear and the variable click is in the other. It was also found that the variable click leading by 5 msec or less completely governs lateralization. It was concluded that monaural forward masking obstructs determination of complex binaural interactions.
Auditory Fatigue: Influence of Mental Factors
Authors: Capps Mary Jayne , Collins William E.
Published: September 2005

Conflicting reports regarding the influence of mental tasks on auditory fatigue have recently appeared in the literature. In the present study, 10 male subjects were exposed to a 4000-cps fatigue tone at 40 dB SL for 3 min under conditions of mental arithmetic and reverie. Temporary threshold shifts, as indicated by comparing pre- and post-fatigue thresholds, were consistently greater when subjects worked mental arithmetic during exposure to the fatigue tone than when they engaged in reverie.
Refraction of Sound from a Point Source Placed in an Air Jet
Authors: Atvars J. , Schubert L. K. , Ribner H. S.
Published: September 2005

A harmonic point source of sound was placed within the potential core of an air jet and the distortion of its sound field by the jet flow was measured. An axial intensity minimum was observed that increases with increasing velocity, frequency, or temperature. The investigation indicates that the cleft in the heart-shaded directivity pattern of subsonic jet noise can be attributed mainly to refraction.
Vocal-Response Synthesizer
Authors: Smith Caldwell P.
Published: September 2005

A new speech synthesizer is described, Instead of bandpass filters, it uses oscillators whose phase, frequency, and amplitude can be modulated pitch-synchronously.
Attenuation of Plane Waves in Semiinfinite Composite Bar
Authors: Plunkett Robert , Wu Chien-Heng
Published: September 2005

The attenuation of plane compressive waves in a semiinfinite composite bar is studied. The bar is composed of a main strip and two serrated septa symmetrically bonded to the main strip by viscoelastic material. The one-dimensional solution gives two complex wavenumbers whose values depend on the complex shear modulus of the viscoelastic material, the frequency, and the relative dimensions. It is shown that maximum attenuation occurs for an optimum value of the loss tangent of the shear modulus. For a typical practical example, this attenuation is about 20 dB in the first three wavelengths for a loss tangent of 0.32.
Method of Determining Complex Poisson's Ratio and Dilatational Constants, Using Forced Vibration of a Sphere
Authors: Lee T. M. , Smith J. L.
Published: September 2005

Following previous investigations on forced-vibration methods of determining dynamic mechanical properties of viscoelastic materials, this article is proposing a similar technique for determining the complex Poisson's ratio and the complex dilatation constants. Through the study of forced vibration of a free viscoelastic sphere with internal harmonic oscillating source, it is found that the above mentioned properties of the test material are related to the ratio of the vibration amplitude of two measurable points. Thus, when using the criterion of this ratio approaching its maximum, the maximum amplitude ratio, these properties can be expressed in simple relationship with the laboratory-measurable quantities: namely, the maximum amplitude ratios and their corresponding vibration frequencies. Investigations have been carried out for three sphere sets.
Extensional Vibrations of Thin Rectangular Plates
Authors: Medick M. A. , Pao Yih-Hsing
Published: September 2005

An approximate one-dimensional theory is derived for the extensional motion of elastic bars or plates of thin rectangular cross section. The resonant frequencies of extensional vibrations of a thin rectangular plate are obtained for a, range of plate dimensions, and a comparison made with some recent experiments. The theory predicts the frequency plateaus characteristic of the incidence of edge modes, as well as displacements at the edge-mode frequency that are localized to the corner edges.
Vertical Directionality of Ambient Noise in the Deep Ocean at a Site near Bermuda
Authors: Axelrod E. H. , Schoomer B. A. , Von Winkle W. A.
Published: September 2005

The vertical directionality of ambient ocean noise at 2400 f (fathoms) off Bermuda has been determined experimentally, using a novel data-reduction technique. In agreement with qualitative models, the results indicate that low-frequency noise arrives primarily from the horizontal while noise of higher frequency is incident from overhead. The measured dependence of observed levels on Beaufort-scale wind force is also consistent with the presumed sources of the noise. Absolute noise levels are several decibels lower than those measured near the surface.
Acoustic Losses of a Resonator with Steady Gas Flow
Authors: Gordon Colin , Smith P. W.
Published: September 2005

Measurements have been made of the acoustic losses of a resonator with a small vent and of their dependence both on the speed of steady flow through the system and on the position of the vent. The resonator is physically modeled on the “T burner” used to test solid propellants for combustion instability, but measurements are made at room temperature and pressure. It is a closed circular cylinder, resonant in the fundamental plane-wave mode, with a vent through the wall near the center. Steady gas flow is introduced at one end through a slightly porous piston whose vibration also generates sound. Losses are determined from the rate of decay of pressure. Significant flow-dependent loss attributable to the vent is found for flow speeds in the vent exceeding about 0.02 times the sound speed. The loss depends on vent position. Good quantitative prediction of this loss at flow velocities above a critical value is achieved by a theory based on the characteristics of quasisteady fluid efflux from an orifice (total pressure quadratic in total flow).
Lateralization Judgments and the Nature of Binaural Acoustic Images
Authors: Toole F. E. , Sayers B. McA.
Published: September 2005

Lateralization-judgment trajectories with interaural time delay of acoustic images arising binaurally are reported for certain multicomponent signals such as multiple tones and repetitive transients. It is shown that certain multiple sound images simultaneously perceived may be independently lateralized and the characteristic judgment trajectories manipulated predictably in various ways. With repetitive binaural transients, the dominant, impulsive, image is shown to be accompanied by tonal images due to harmonics but it is argued that the impulsive image does not arise as a synthesis of the harmonic tonal images. High- and low-pitched impulsive images appear to be related to individual acoustic transients and apparently arise by virtue of neural activity in two different regions of the cochlea.
Propagation of Forced Sound Waves in Rarefied Gasdynamics
Authors: Sirovich Lawrence , Thurber James K.
Published: September 2005

A kinetic theory description of sound propagation in a simple gas is presented. The results are in very close agreement with experiment through all values of Knudsen number.
Effective Elastic Coefficients for Wave Propagation in Crystals under Stress
Authors: Thurston R. N.
Published: September 2005

Effective elastic coefficients for wave propagation obeying all of the classical symmetry relations βijkm=βkmij=βjikm=βijmk= … can be defined for crystals of any symmetry under positive or negative hydrostatic pressure. For other states of stress, the full symmetry is lost, even in isotropic materials. The loss of the full symmetry commonly expected of elastic coefficients has a simple physical interpretation the case of uniaxial stress in an isotropic medium. A transverse wave propagates faster in the direction of tension than in the perpendicular direction because tension increases the restoring force for displacements associated with the former wave, just as in a stretched string. The difference in ρV2 for the two waves equals the tensile stress. Hence, the corresponding effective elastic coefficients, which would be equal under the classical symmetry, also differ by this same amount. In this paper, we define effective elastic coefficients and express them in terms of the stress, the deformation resulting from the stress, and the thermodynamic elastic coefficients, the latter being defined in terms of derivatives of the internal energy with respect to the Lagrangian strain components. When expressed in terms of effective elastic coefficients, the formulas for wave-propagation velocities in hydrostatically compressed crystals take the same form at any pressure. The quantities usually cited in the ultrasonics literature as pressure derivatives of elastic coefficients are derivatives of the effective coefficients rather than the thermodynamic coefficients. We also define “wave-propagation coefficients,” which are more convenient than the effective elastic coefficients for discussing wave propagation, especially under nonhydrostatic states of stress. These fall naturally into a 6×6 array that is symmetric under hydrostatic pressure but not in general. In general, 26 of the coefficients are independent.
Noise Spectrum of Arc-Plasma Generators
Authors: Burns Jay , Halle Henry
Published: September 2005

Typical acoustical-noise spectra of two different very-high-temperature gas heaters of the arc-plasma type are presented. Although the two arc-plasma generators differed greatly in size, their noise spectra were similar, being characterized by a broad midrange maximum with a rapid decrease at high frequencies.
Processing against Reverberation on a Moving Platform
Authors: Westerfield E. C. , Brandon M. K.
Published: September 2005

Cusps in the reverberation spectra caused by the speed of the transmit-receive platform are discussed. It is found that for side-looking SONAR, these cusps, received on the side lobes, may best be eliminated by steering nulls in the fore and aft directions.
Theoretical Model for Mutual Radiation Resistance of Small Transducers at an Air-Water Surface
Authors: Sherman Charles H.
Published: September 2005

Recent measurements of the mutual radiation resistance between small transducers vibrating at an air-water surface can be approximately explained theoretically with a model consisting of dipole spheres. The results provide a useful example of mutual radiation resistance for nonrigid baffle conditions.
On the Power Gained by Clipping Speech in the Audio Band
Authors: Wathen-Dunn Weiant , Lipke David W.
Published: September 2005

For more than a decade it has been known, in a qualitative way, that the long-time average power of a speech signal in an amplitude-limited communications system can be increased materially by clipping the peaks of the speech wave and amplifying the remainder until the new peaks have the maximum allowable amplitude. This power increase can be computed from the statistical distribution for the instantaneous amplitudes of speech. Some of the available distributions have been collected and compared, and, upon their showing good agreement, one of them has been used for the computation. Simple formulas show that the power increase can be neither greater than the amount of clipping nor greater than the peak factor of speech. For 24 db of peak clipping, the power gain is about 12 db. The exact value depends upon the choice of peak factor for unclipped speech. In practice, the actual gain in signal-to-noise ratio on peak-limited communications systems (e.g., AM and DSB radio) will be less than that computed here.
Impact-Noise Characteristics of Female Hard-Heeled Foot Traffic
Authors: Watters B. G.
Published: September 2005

It has been said that the ISO tapping machine does not yield data on representative flooring materials that accurately relate to the impact-noise isolation provided for real, foot-fall impacts. To understand this problem, we have measured the impact force under both the ISO hammer and a woman's shoe heel. The hammer force is found to be much more intense and generally to contain more high-frequency components than the heel force. The differences between hammer and heel forces are found to arise from the different mechanical internal admittances and from the different approach velocities. Radiated sound levels for the measured force spectra applied to a concrete slab are calculated and found to agree closely with measured impact sound levels. We conclude that the ISO machine grossly misrepresents the impact isolation provided by some typical floor surfaces.
Use of Noise to Eliminate One Ear from Masking Experiments
Authors: Weston Peter B. , Miller James D.
Published: September 2005

To evaluate the possibility that one ear can be eliminated from a masking experiment by use of noise, certain relevant facts were determined. These are: (1) if a tonal signal mixed with noise is received at one ear, the addition of a noise to the other ear slightly reduces the threshold for the tone if the noises are statistically independent; (2) in contrast, the noise added to the nonsignal ear distinctly reduces the threshold for the tone if the noises are perfectly correlated (+1.0); (3) these effects, (1) and (2) above, are observed whether the level of the masking noise at the ear that receives the tonal signal is less than, equal to, or greater than the level of the added noise at the ear that does not receive the tone; (4) if identical tones are presented to the two ears and if the signal-to-noise ratio is about 25 dB lower in one ear than in the other, the effect of the signal at the ear with the lower signal to noise ratio is eliminated from the masking experiment.
Distortion Processes in the Cochlear-Microphonic Response under Normal and Abnormal Physiological Conditions
Authors: Wolsk David
Published: September 2005

There is a long history of controversy concerning the locus and mechanism of harmonic-distortion processes in the cochlea. This controversy has importance for theories of frequency analysis along the basilar membrane and concepts of the transduction process in the hair cells, as well as for the clinical significance of psychophysical tests of aural harmonics. The cochlear-microphonic response to a pure tone recorded at the round window of the guinea pig was led into three wave analyzers tuned to the 1st-, 2nd-, and 3rd-harmonic frequencies, each component then driving one channel of a pen recorder. The various components exhibit shifts through time, which were studied at various frequencies and intensities, and during recovery from fatiguing and damaging levels of tonal and random-noise stimulation and anoxia. The data are discussed in terms of mechanical versus transduction concepts of harmonic distortion in the cochlea.
Radiation Force on Bodies in a Sound Field
Authors: Olsen Haakon , Romberg Werner , Wergeland Harald
Published: September 2005

A simple derivation of the force which acts on a body placed in sound field is given. The tensor properties of the force are exhibited, but it is also shown that for a rigid body the force may be derived from the scalar pressure alone. It is shown how the time average force is determined by the momentum lost by the sound wave during the collision with the body. Using this result, the force is related to the scattering amplitude, and a simple expression in terms of the phase shifts is given.

The connection between the force and the scattering cross section is examined. A force factor κ = K̄z/(12ρ0k2σsc) is defined. It is shown that κ = 1 for plane scatterers perpendicular incidence. A simple general formula for the force in the limit of short wavelengths is derived. It is shown that neither for very long wavelengths nor for very short ones is κ in general equal to 1.

The case of a rigid sphere is treated in detail. Curves are shown for the force and for the force factor κ.
Definitions of d′ and η as Psychophysical Measures
Authors: Tanner Wilson P. , Birdsall T. G.
Published: September 2005

Because studies employing d′ and η are based on the theory of signal detectability, the theory is reviewed in sufficient detail for the purposes of definition. The efficiency, η, is defined as the ratio of the energy required by an ideal receiver to the energy required by a receiver under study when the performance of the two is the same. The measure d′ is that value of (2E/N0)12 necessary for the ideal receiver to match the performance of the receiver under study, where E is the energy of the signal, and N0 is the noise power per unit band width. The measure is extended to include the recognizability of two signals. Every set of signals is described by a Euclidean space in which distances are the square roots of the energy of the difference signal, (EΔ)12. The unit of measure is the square root of one-half of the noise power per unit band width (N0/2)12.