bluuebunny/crossref_metadata_2025 huggingface dataset:
Cortical Responses of Awake Cat to Narrow-Band FM Noise Stimuli
Authors: Glaser Edmund M.
Published: October 2005

Unanesthetized cats with chronically implanted epidural electrodes in the region of primary auditory cortex were stimulated with frequency-modulated (FM) noises of varying bandwidths. The average evoked responses to these stimuli were compared with responses to tone bursts of the same center frequency and intensity. Two different noise stimuli were used: (a) bursts with rise/fall times the same as the tone burst; (b) transitions from tone to noise and back with transition times equal to tone-burst rise time. It was found that: (1) the magnitude of the early response components increases with the bandwidth of the modulating noise, the relationship being fitted well by a power function; (2) there is a smaller power-law type of increase in response amplitude with rms rate, noise bandwidth being held constant; (3) responses to transitions from tone to noise were quite marked, often exceeding burst responses, while responses to transitions from noise to tone were only rarely observed. These results are discussed in terms of the activity of single units in auditory cortex. A simple neuronal model is proposed to explain and unify the findings. The results are also compared with psychological loudness summation studies.
Depth of Sequential Auditory Information Processing: III
Authors: Pollack Irwin
Published: October 2005

The auditory discrimination of quasiperiodic finite-state sequences was examined for four alternative methods of encoding binary states: pulse polarity, the occurrence or nonoccurrence of a pulse, the ear to which a pulse was delivered, and interpulse interval. Except for relatively poor sensitivity for pulse polarity within low-frequency pulse trains, all four methods of encoding led to nearly comparable discrimination. The specific method of encoding finite-state information is apparently not critical for the auditory discrimination of quasiperiodic sequences. For each method of encoding, best performance is achieved for pulse trains of many short interpulse intervals. The detection of sequential constraints is apparently carried out primarily by means of information within high-frequency auditory channels. Under selected conditions, the three methods based upon binary coding of periodic clock intervals are more sensitive than that based upon pulse interval coding. The auditory analysis for partial periodicities is apparently carried out over relatively constant temporal sampling intervals.
Intracochlear Potential Recorded with Micropipets. II. Responses in the Cochlear Scalae to Tones
Authors: Weiss T. F. , Peake W. T. , Sohmer H. S.
Published: October 2005

Cochlear potential response to tones was recorded with glass micropipets in all three scalae of the basal region of the cochlea of 32 anesthetized cats. The fundamental component of the potential (referred to an electrode on the chin) is represented by complex amplitudes EV, EM, ET, where the subscripts denote the scala in which the potential was recorded. EM/EV is relatively independent of stimulus level and frequency and has a magnitude of approximately 1.0–1.8 and an angle of approximately zero. EM/ET is dependent on stimulus level and frequency. Its magnitude is as large as 10 at frequencies below 300 Hz and decreases for higher frequencies. The angle of the ratio increases from approximately zero at 100 Hz to a value between +90° and +180° above 1000 Hz. Similar results were obtained from two cochleas with a severed auditory nerve, which implies that these results apply to the cochlear microphonic (CM) potential response to tones. An electric-network model of the spatial distribution of CM is analyzed.
Speech in Deep-Submergence Atmospheres
Authors: Morrow Charles T.
Published: October 2005

Among the factors that could affect the intelligibility of helium speech at deep submergence are an upward shift of formant frequencies in accordance with the velocity of sound, a disproportionate shift of first formant frequencies as a result of increased pressure, attenuation of high frequencies of the voice just when they become essential, deterioration of microphone response with depth, change of the diver's hearing above 3 kHz with depth, occupational deafness above 3 kHz, and acoustic reaction of a mask cavity as opposed to the larger space of a habitat or diving bell. Of these, the first and the last two are the most important. The key to the problem is a microphone of satisfactory design. In conjunction with such a microphone, a helium translator can be made to restore intelligibility even when the listener has a severe high-frequency hearing loss.
On the Transmission of Sound through Finite Closed Shells: Statistical Energy Analysis, Modal Coupling, and Nonresonant Transmission
Authors: Pope Larry D.
Published: October 2005

An investigation of sound transmission into small enclosures considers the effects of acoustically induced coupling between shell modes. The level of cavity reactance is examined. The noise reductions for a closed cylinder and a rectangular parallelopiped enclosure (with a single flexible panel) placed in reverberant acoustic fields are computed and experimentally checked. The transmission by resonant and nonresonant shell modes is examined, especially in relation to the statistical-energy-analysis approach. The nature of the predominance of one type of transmission over the other is considered in relation to shell and cavity configurations and structural damping levels.
Scaling Laws for Underwater Exploding Wires
Authors: McGrath James R.
Published: October 2005

Peak pressure and time measurements and impulse and energy calculations are reported of the shock wave resulting from 5- and 10-mil 12-in.-long Nichrome wires. The time, impulse, energy, and gauge distance are scaled to obtain the resulting similarity curves of peak pressure, reduced time constant, reduced impulse, and reduced energy, which are plotted against the scaled reciprocal distance.
Comments on “Zero-Crossing Shifts as a Detection Method” [N. BOM AND B. W. CONOLLY, J. Acoust. Soc. Amer. 47, 1408–1411 (1970)]
Authors: Riter Stephen , Boatright P.
Published: October 2005

Comments are made on the subject paper. The use of level crossing rate as a means of signal detection in white Gaussian noise is proposed. Some preliminary results are given which indicate that acceptable performance may be realized at low signal-to-noise ratios.
Scattering by a Spherical Cap
Authors: Miles John W.
Published: October 2005

The boundary-value problem for plane-wave scattering by a spherical cap is formulated in terms of either the radial velocity in the aperture or the equivalent-vortex strength of the shell. The resulting complementary integral equations are used to construct complementary variational expressions for the scattering cross section and also are solved approximately by Galerkin's method. Numerical results are given for the scattering cross section, say σ, with special reference to the Helmholtz resonator (small aperture) and the hemispherical shell. The function σ(k), where k is the dimensionless wavenumber based on the radius of the sphere, rises initially as k4 (Rayleigh-scattering regime) to a first peak, σ(k0), and then executes a decaying oscillation about the asymptotic value, σ∞ (twice the transverse area intercepted by the incident wave); σ(k0) = O(1/β) as the polar angle of the aperture, β, tends to zero, whilst σ(k0) = 2.13σ∞ for the hemispherical shell.
Effect of Shear Flow on Sound Propagation in Rectangular Ducts
Authors: Hersh A. S. , Catton I.
Published: October 2005

The investigation by Pridmore-Brown of the effects of shear on the downstream propagation of sound in rigid-walled rectangular ducts has been extended to include upstream sound propagation as well as the effects of boundary-layer thickness. Solutions are given in terms of a combined Galerkin-Runge-Kutta numerical technique as well as in terms of a technique based upon a perturbation of the well-known zero Mach number solution. The effect of shear on upstream sound propagation is to refract the sound into the center of the duct. The effect of refraction is found to be important for boundary-layer flows when the ratio of boundary-layer height to acoustic wavelength is equal to or greater than unity.
Dynamic Characteristics of Air-Pressure Measuring Systems Used in Speech Research
Authors: Edmonds Terry D. , Lilly David J. , Hardy James C.
Published: October 2005

A method was developed to measure empirically the dynamic characteristics of air-pressure transducers and associated attachments utilized in speech research. With this method, frequency-response data were collected for transducers used in measuring magnitudes of air pressure associated with speech production. The effect of attaching hypodermic needles (used for trachial punctures to measure subglottal air pressure) and plastic tubes (used for measuring intraoral and intraesophageal air pressures) to these transducers was also studied. In addition, frequency-response data were collected for two low-range pressure transducers that are used in conjunction with pneumotachographs (for measuring rates of airflow through the vocal tract). The effect of pressure magnitude upon the frequency response of an air-pressure transducer was determined. Conclusions are offered on the basis of the data obtained, and implications for speech research are suggested.
Electromechanical Properties of PbTiO3 Ceramics Containing La and Mn
Authors: Ikegami Seiji , Ueda Ichiro , Nagata Takashi
Published: October 2005

A piezoelectric ceramic material having low dielectric constant, high thickness coupling factor, high mechanical quality factor, high stability, and high operating temperature, has been prepared from PbTiO3 incorporated with 2.5 mol% of LaO12 and 1.0 mol% of MnO2. Typical electromechanical constants of this material are as follows: dielectric constant ε11T/ε0 230, ε33T/ε0 170; coupling factor k33 0.46, kt 0.46, k15 0.28, kp 0.07, k31 0.04; mechanical quality factor Q 1100, Poisson's ratio σE 0.20. Frequency constants Nt and N3t of the fundamental and third-harmonic thickness vibrations have temperature coefficients of −1.1 × 10−4°C−1 and −2 × 10−5°C−1, respectively. Aging rates of Nt and N3t, are +0.02% and −0.02%/time decade at 30°C, respectively. The Curie point of this material exists at 470°C, and k33 and kt increase gradually with temperature up to 400°C. This material has grain size of 2–3 μ and bending strength of 2 × 107 kg/m2, and can be polished into very thin plate. The PbTiO3 ceramics have a high potential for use in electromechanical devices at high frequency and high temperature.
Head-Related Two-Channel Stereophony with Loudspeaker Reproduction
Authors: Damaske P.
Published: October 2005

Reproducing stereophonic signal pairs with two loudspeakers on the front left and right of a listener yields acoustical crosstalk resulting from sound diffraction at the head. Stereophonic phantom sound sources are therefore heard only between the two loudspeakers. However, signal pairs can be constructed from the original signals generating extremely lateral phantom sources. A filter for this purpose is constructed using concentrated elements (“90° filter”). The complex frequency response of the 90° filter is determined in a listening experiment with narrow-band noise. Two 90° filters are combined for a two-channel reproduction system. Signals received by a dummy head with a microphone in each ear are fed to the inputs of the 90° filters. This transmission system was tested for its directional fidelity with many test persons. Localization is nearly ideal for the entire horizontal plane including front-back discrimination and is partly correct even for the median plane.
Speaker Sex Recognition of 5- and 6-Year-Old Children's Voices
Authors: Weinberg Bernd , Bennett Suzanne
Published: October 2005

Listeners were generally able to identify the sex of 5- and 6-year-old children through recordings of their speech. Differences in average fundamental frequency characteristics among the children did not account for the recognition performance of listeners.
Ultrasonic Examination of the Hemoglobin Dissociation Process in Aqueous Solutions of Guanidine Hydrochloride
Authors: O'Brien W. D. , Dunn F.
Published: October 2005

The ultrasonic absorption was determined, in aqueous solutions of hemoglobin undergoing dissociation as a function of the strong electrolyte guanidine hydrochloride (GuHCl), up to 5.4M (molar), over the frequency range 1–50 MHz. With increasing GuHCl concentration to 0.7M, the Hb molecule dissociates into half-molecules without loss of tertiary structure, and at GuHCl concentrations greater than 2.5M, the Hb molecule dissociates further into its four individual polypeptide chains with complete loss of tertiary structure. The ultrasonic absorption coefficient appears to be insensitive to the dissociation process, though a small contribution appears at the lower frequencies, owing to the expansion of the polypeptide molecule. A maximum in the absorption occurs near 2M GuHCl concentration, which does not correspond to dissociation or expansion of the Hb molecule, and it is thought to be associated with the proton transfer reaction.
Short-Time Spectra and Time-Frequency Energy Distributions
Authors: Ackroyd Martin H.
Published: October 2005

The squared magnitude of the cross-ambiguity function of two signals is shown to be given by the two-dimensional cross correlation of the individual time-frequency (t-f) energy distributions of the signals. This result is used to show that a short-time spectrum measured in the usual way is the two-dimensional convolution of the t-f energy distribution of the signal with a function which is simply related to the t-f energy distribution of the window which is used.
A Decade of Experience with Velocimeters
Authors: Mackenzie Kenneth V.
Published: October 2005

Over a decade of experience with velocimeters aboard deep submergence vehicles has demonstrated that accuracies of 0.1 m/sec or better can be obtained with proper procedures. Calibrations and distilled water equations are discussed, along with the new International Temperature Scale adopted in 1968. Calibration drift is described for three types of velocimeters to underscore that accuracy requires frequent calibrations as well as intercomparisons between several instruments during. deep dives. Pressure corrections are computed. Errors due to thermal lags of earlier velocimeters were observed while transmitting thermoclines. Laboratory measurements with a velocimeter in 50 gal of natural seawater of 27.405‰ salinity gave good results, closer to those of V. A. Del Grosso [J. Acoust. Soc. Amer. 47, 947 (1970)], than to W. D. Wilson [J. Acoust. Soc. Amer. 32, 1357 (L) (1960)].
Transmission of Acoustic Waves through Submerged Orthotropic Spherical Shells
Authors: Naghieh Mohammed , Hayek Sabih I.
Published: October 2005

The problem of transmission of acoustic waves through submerged orthotropic spherical shells was considered. The sound radiation in an infinite acoustic fluid is induced by a rigid spherical transducer, concentric within an orthotropic spherical shell having an axisymmetric surface-velocity distribution. The space between the spherical transducer and the orthotropic spherical shell is full of the same acoustic fluid as that outside of the shell. The equations of motion for orthotropic shells, as well as for the fluid inside and outside, were derived. These equations are then solved by satisfying the continuity conditions on all solid-fluid interfaces. Four representative transducer surface-velocity distributions were considered. The solution for the farfield acoustic pressure was obtained for an orthotropic and for an isotropic shell.
Kinematics of Wide-Band Field Sensing by Extended Sensors in Motion
Authors: Eichler Ewald
Published: October 2005

This analytical study concerns the sensing of wide-band pressure fields by moving receivers or sensors. Treated are linear kinematical aspects for ideal sensors that travel at constant subsonic or supersonic velocities. The fields are described in wave-harmonic (wavenumber-frequency) space. The sensed signal or noise components are related at their sensed frequencies and on a spectral basis. It is shown that the point sensor is no longer uniform or nondirective once it moves. Its directional pattern, and that of spatially extended sensors, too, depends upon the Mach number of sensor motion, upon the sensed frequency, and even upon the choice of a reference spectrum for the fields in the resting fluid. A certain compensation for the effects of motion is possible in directive sensors by adjustment of parameters. This compensation, however, is partial and permits only the preservation of some crucial feature. The adjustment is explained in terms of a “matched Mach number” for back-nulled gradient and endfire-line sensors. The definition of gain is amended, and the concept of the equivalent signals of sensed field components is recommended as a suitable measure of a sensing situation. Equivalent spectra of noise incident from the rear and of isotropic noise are presented for velocity-matched back-hulled gradient and endfire-line sensors; depending upon frequency and reference spectrum, they differ from their rest values.
An Acoustic Model for the Experimental Study of Water-Wave Problems
Authors: Shaw R. P. , Parvulescu A.
Published: October 2005

A two-dimensional acoustic analog to gravity water waves traveling over constant depth is suggested as an experimental approach to problems of water-wave scattering, harbor resonance, etc. The advantages of an acoustic model over the present water tank models are many, including a factor of 20–50 in cost, shortened time scale of experiments, sensitive readily available measuring equipment, etc.
Effects of Smoothing and Quantizing the Parameters of Formant-Coded Voiced Speech
Authors: Rosenberg A. E. , Schafer R. W. , Rabiner L. R.
Published: October 2005

A subjective evaluation of the effects of smoothing and quantization of the parameters for formant-coded voiced speech has been carried out. Thresholds were obtained for the degree of smoothing or quantization of specified parameters associated with a just noticeable degradation of all-voiced sentence material. Average quantization threshold levels obtained were: pitch period, 3.9 bits; first formant, 2.7 bits; second formant, 3.1 bits. The average of low-pass filter bandwidth thresholds for the simultaneous smoothing of formants was 7.6 Hz per formant; for pitch-period data the low-pass filter bandwidth threshold was 3.9 Hz. With simultaneous low-pass filtering and quantization, the estimated over-all bit rate for the coded parameters of all-voiced speech was approximately 200 bits/sec.
Inhibition in the Auditory Nerve?
Authors: Moushegian G. , Rupert A. L. , Stillman R. D. , Weiss I. P.
Published: October 2005

Some recent findings from auditory nerve studies are considered as evidence for primary afferent inhibition.
Comments on “Application of Conformal Mapping and Variational Method to the Study of Natural Frequencies of Polygonal Plates” [J. C. M. Yu, J. Acoust. Soc. Amer. 49, 781–785 (1971)]
Authors: Laura Patricio A. , Marinelli Evelina
Published: October 2005

Some of the results obtained by Yu are compared with values obtained by other investigators. In the case of a square plate, Yu's results are approximately 8% higher than the exact values.
Acoustic Ray Paths through a Model Vortex with a Viscous Core
Authors: Georges T. M.
Published: October 2005

Angular deflection and the formation of a line caustic are examined for acoustic rays passing through a cylindrical vortex with a viscous core. Ray paths are displayed in normalized form and appear to be applicable to the aircraft-wake problem as well as to long-distance sound propagation through synoptic weather features.
Sound Transmission through Vegetation in Relation to Leaf Area Density, Leaf Width, and Breadth of Canopy
Authors: Aylor Donald
Published: October 2005

Transmission of random noise through dense reeds (Phragmites communis) was measured. The ground surface was water and thus ground attenuation could be closely determined. A single relationship between leaf area density, breadth of canopy, leaf width, and frequency is presented, which allows the attenuation due to a stand of herbaceous plants to be estimated.
Reply to “Comments on ‘Approach to the Multiple-Surface-Reflection Problem in a Linear-Gradient Medium’” [D. T. Raphael, J. Acoust. Soc. Amer. 49, 1680–1681(L) (1971)]
Authors: Raphael David T.
Published: October 2005

The remarks made by L. A. Stallworth concerning a letter by D. T. Raphael [J. Acoust. Soc. Amer. 49, 1680–1681 (L) (1971)] have no bearing on the controversy dealing with the approach to the multiple-surface-reflection problem in a linear-gradient medium. The example that Stallworth cites is for an isospeed medium involving no refraction correction.
Synthesis of an Optical Sound Spectrograph
Authors: Yu F. T. S.
Published: October 2005

The basic theory of a large space bandwidth signal analysis by means of a two-dimensional optical processor is discussed and the synthesis of a near real-time optical sound spectrograph is presented. In the current state-of-the-art, the realization of an optical sound spectrograph is feasible. It is also concluded that the optical sound spectrograph may offer a broader frequency range of analysis and flexibility in spectrum data handling. The former may be important in ultrasonic signal analysis; the latter may be important in future research in automatic speech recognition, synthesis, and translation.
Numerical Study of Sound Refraction by a Jet Flow. I. Ray Acoustics
Authors: Schubert L. K.
Published: October 2005

Sound rays are traced numerically from a point source on the axis of a jet flow with realistically chosen velocity profiles. The directivity patterns computed from the ray paths have no cone of absolute silence, in contrast with analytic results for nonspreading jets. A related observation is that the surfaces of constant phase are ultimately spherical. Nevertheless, the computed axial refraction valleys are much deeper than those observed in jet noise studies. The difference is due to diffraction, which tends to offset refraction effects at all but the highest (ray-acoustic) frequencies.
APPLICATION OF MECHANICAL IMPEDANCE INSTRUMENTATION FOR THE STUDY OF VIBRATION PROPERTIES OF MUSICAL INSTRUMENTS
Authors: Pallett David S.
Published: October 2005

A series of informal measurements of the mechanical driving-point impedance properties of a toy xylophone and a souvenir steel drum is described. Complicating factors are indicated. It is shown that interesting mechanical properties of the toy xylophone can readily be demonstrated. In contrast, it is more difficult to perform accurate measurements upon the steel drum, and the measurements program was ultimately directed toward the properties of a large steel drum, with greatly improved accuracy.
Intensity Perception. II. Resolution in One-Interval Paradigms
Authors: Braida L. D. , Durlach N. I.
Published: October 2005

This paper reports the results of a series of experiments on tone pulses designed to test certain predictions of the preliminary theory of intensity resolution (Durlach and Braida, 1969) relevant to one-interval paradigms. Resolution was measured in identification and scaling experiments as a function of the range, number, and distribution of intensities, and the availability of feedback. Some of the results, such as those on the dependence of resolution on range and number of stimuli in absolute identification, support the theory. Other results, however, such as those comparing resolution in identification with resolution in magnitude estimation for a small common range, indicate that the theory is inadequate and needs to be revised.
Perceived Level of Noise by Mark VII and Decibels (E)
Authors: Stevens S. S.
Published: October 2005

The calculation procedure Mark VII gives the perceived level of loudness or noisiness in PLdB. It utilizes a set of frequency-weighting contours based on an average of 25 experimental contours. The standard reference sound is defined as a 13-oct band centered at 3150 Hz. The perceived magnitude (loudness or noisiness) grows as the 23 power of the sound pressure, so that perceived magnitude doubles with each increase of 9 dB. The summation formula for the total subjective magnitude remains St = Sm + F (∑S − Sm), but the value of F is made to vary as a function of level in order to reflect the nonlinear growth (in log-log coordinates) of broad-band noise. As a result of the new reference sound at 3150 Hz, perceived level in decibels (PLdB) is approximately 8 dB lower than the older loudness level in phons. Except for the nearly constant difference of 8 dB, Mark VI and Mark VII give closely similar results for typical broad-band noises. The 8-dB downward shift makes it possible for a sound level meter with an “ear weighting” to give readings (E) in decibels within a decibel or two of perceived level in PLdB. With the frequency-weighting contours extended down to 1.0 Hz, Mark VII also provides a procedure for calculating the perceived levels of sonic booms and other impulse noises.
Auditory Adaptation and Its Relationship to a Model for Loudness
Authors: Weiler Ernest M. , Loeb Michel , Alluisi Earl A.
Published: October 2005

Predictions, inferred from Small's model, of significantly lower auditory adaptation when test-tone intensity exceeds adapting-tone intensity were confirmed. Adaptation effects with test and adapting tone equal in intensity increased between 40 and 60 dB and remained relatively constant between 60 and 80 dB. When adapting-tone intensity exceeded test-tone intensity, previous findings that adaptation does not increase generally were confirmed. Theoretical implications of the results are discussed.
Dural Recordings of the Averaged Evoked Response in Guinea Pigs
Authors: Rubin A. M. , Gannon R. P.
Published: October 2005

Auditory evoked responses to pure-tone stimuli were examined in guinea pigs, with chronically implanted electrodes on the dura mater, by means of the summing computer technique. Two distinct response patterns differing in waveshape, latency, association with the pinna reflex, habituation, and threshold were noted. The first, called the Preyer reflex evoked response (PRER) because it tended to occur in association with the pinna reflex, was a myogenic response. The second was a neurogenic potential called the evoked cortical response (ECR). The ECR response was resistant to habituation and present at low intensities of approximately the same level as those reported by behavioral investigation. Once PRER habituation had occurred, myogenic contamination was no longer a hazard in dural recordings.
Comparison between Objective and Threshold-Shift Methods of Measuring Real-Ear Attenuation of External Sound by Earphones
Authors: Villchur Edgar
Published: October 2005

The attenuation of low-frequency external sound by MX41/AR earphone cushions appears greater when measured by the threshold-shift method than when measured by an objective real-ear method. It is suggested that the objective measurements have greater validity, because threshold-shift measurements are subject to the influence of masking by earphone-induced physiological noise.
The Need for Standards on Noise
Authors: Meyer Alvin F.
Published: October 2005

The problem of noise is reviewed from the standpoint of environmental pollution. The regulation of noise by government at every level demands the setting up of standards which take into account not only scientific criteria but also economic, sociological, and political considerations.
Analysis of Unsteady MHD Flow in Conduits of Arbitrary Cross Section by a Complex Variable Approach
Authors: Laura Patricio A. , Ercoli Rubén
Published: October 2005

The present paper deals with the dynamic response of MHD (magnetohydrodynamic) flow when subjected to an impulsive pressure gradient. Since the governing differential system is linear, the results can be easily generalized to include any arbitrary variation of the pressure gradient with respect to time. Approximate but unified analytical solutions are obtained for any type of cross sections.
17-Moment Theory of Sound Propagation in Polyatomic Gases
Authors: McCormack Francis J. , Creech Harold W.
Published: October 2005

The problem of combined translational and internal relaxation of sound waves in polyatomic gases is studied using the 17-moment approximation. When applied to the sound problem, the moment equations, which are valid for any number of internal degrees of freedom, yield a generalized complex matrix eigenvalue equation which is solved numerically for the absorption coefficient and propagation speed as a function of the rarefaction parameter (the approximate ratio of collision frequency to sound frequency). The physical parameters in the equations are the self-diffusion coefficient (assumed the same for each internal mode), the internal relaxation times, and the internal specific heats. Our solutions for the combined absorption for the case of a single internal mode are compared to those obtained assuming the total absorption is the sum of that due to the translational and internal effects separately, and to that obtained by using the combination rule of Greenspan. Comparison is also made between the combined dispersion calculated by the 17-moment method and the Greenspan rule. In addition, absorption curves are calculated for the case of two internal degrees of freedom for various combinations of internal collision numbers. When applied to rotational relaxation in N2 our theory yields, for a rotational collision number of 5.26, good agreement with experiment over the range of values of the rarefaction parameter for which a continuum theory is expected to be valid.
An Amplifier Gain Control for Ultrasonic Pulse-Echo Measurements
Authors: Reed Robert W. , Binnie David E. , Brickwedde F. G.
Published: October 2005

An automatic gain control (AGC) for maintaining constant gain of the i.f. amplifiers in an ultrasonic pulse-echo system is described. The AGC stabilizes the receiver against long-term drifts. It is applicable if the duty cycle of the sonic-echo train is small (5% or less) and the rest of the cycle is available for introduction of a reference signal. The AGC samples the amplified reference signal and keeps its level constant, thereby maintaining constant gain in the i.f. amplifiers without the necessity for using an additional gated integrating amplifier. The AGC improved the reliability of measurements of sonic-echo voltage from ±3% without the AGC to ±0.5% with the AGC over a long period of time. The total ultrasonic system for attenuation measurements in the range 20–500 MHz, including the AGC, is described.
Schlieren Visualization of Radiation Caused by Illumination of Plates with Short Acoustical Pulses
Authors: Dragonette Louis R.
Published: October 2005

Schlieren visualization of the radiated field in water above and below aluminum plates, illuminated by short acoustic pulses, is presented. At certain angles of incidence of the incoming pulse, radiated wavefronts are seen to progress along the plates with specific angles of inclination and associated speeds of progression. In particular, strong effects are observed near the longitudinal and shear critical angles. The measured angles of incidence, at which these effects were generated, are in good agreement with predictions of Lamb theory for plates whose thicknesses are 0.58 wavelengths and larger. For thinner plates, the effects of water loading appear to become significant. A path trace analysis gives good agreement with the group velocity of observed effects when obvious trapped propagation paths are suggested by the reflection coefficient curves for a water-aluminum boundary. Specific radiated wavefronts on plates are related to waves which were observed on cylindrical shells. Relationship of the shell results to Lamb modes is discussed. Plates with thicknesses from 0.002 to 0.241 cm, and frequencies of 5 and 7.2 MHz, are used.
Signal Rate Processing for Transit Detection
Authors: Hunt F. V.
Published: October 2005

A transit detector has been devised that yields a positive response, with high detection probability and a low and reliable false-alarm rate, whenever a moving sound source completes a transit past the monitoring sensor. The signal rate, instead of the signal amplitude, is processed by sampling periodically the time derivative of the output of a smoothing filter with a very long time constant operating on a rectified broad-band input signal. Only the algebraic sign of the derivative is retained and this is entered in a shift register. Half the shift register will be filled with ones and the other half with zeros at the end of a transit-like time variation of the signal component of the input signal-plus-noise. This represents a unique binary detection number that can easily be recognized with digital certainty, and the false-alarm rate can be made arbitrarily small by making the shift register long enough. The selection of optimum design parameters for the processor was studied with a time-scaled model. The results indicate, for example, that a detection probability of 90%, with a false-alarm rate of one per 107 samples, can be achieved when the maximum signal-to-noise level difference during a transit is no higher than −10.6 dB. Detection sensitivity can be traded off against false-alarm rate in either direction at an exchange rate of about 0.5 dB for each factor of 10 in false-alarm rate.
SOLIDS MEASUREMENTS IN BEVERAGES, SAUCES, AND SYRUPS USING SOUND VELOCIMETRY
Authors: Zacharias E. M. , Parnell R. A.
Published: October 2005

Sound-velocity measurements were made in fruit and vegetable juices, vegetable oils, sauces, wines, and syrups. The dependence of sound velocity on total solids and on temperature is discussed. Sound velocity values at 25°C are given for 38 products tested. A relationship is described for determining percent solids from sound-velocity measurements and an expression is given for computing measurement error. Solids measurement accuracies ranging from 0.024% to 0.088% are listed for prune juice, tomato juice, apple juice, applesauce, maple syrup, and corn syrup.
Preceding Vowel Duration as a Cue to the Perception of the Voicing Characteristic of Word-Final Consonants in American English
Authors: Raphael Lawrence J.
Published: October 2005

A number of studies in the literature have stated that the duration of a vowel is a significant cue to the voicing characteristic of the consonant that follows it. The present study investigated the effect of varying preceding vowel duration upon the perception of word-final stops, fricatives, and clusters in synthetic speech. A variety of minimal CVC (C) pairs was synthesized and the vowel of each was varied over a range of values derived from durations found in real-speech samples. It was found that, regardless of the cues for voicing or voicelessness used in the synthesis of the final consonant or cluster, listeners perceived the final segments as voiceless when they were preceded by vowels of short duration and as voiced when they were preceded by vowels of long duration. Discrimination tests revealed that when the voicing characteristic is cued by vowel duration, perception is continuous rather than categorical.
Resonance Structure in Echoes from Schooled Pelagic Fish
Authors: Holliday D. V.
Published: October 2005

Explosive acoustic sources were used to obtain echoes from aggregations and schools of commercially important marine fish. Narrow-band spectral analysis of the echoes from these targets revealed significant structure in the frequency range from 200 Hz to 5 kHz. The targets were partially captured after the acoustic tests; three yielded northern anchovy (Engraulis mordax), one consisted of a mix of anchovy and jack mackerel (Trachurus symmetricus), and the last sample contained an aggregation of seven species of rockfish (Sebastes), whitefish (Caulolatilus princeps), and a striped seaperch (Embiotoca lateralis). The results of the direct biological sampling were combined with theoretical predictions for the resonant swimbladder response and compared with the experimentally observed resonances.
Research on Fan Noise Generation
Authors: Benzakein M. J.
Published: October 2005

Different aspects of multiple-pure-tone (MPT) “broadband” noise generation in high-speed fans are discussed. An analytical model for multiple-pure-tone generation is presented. Experimental evidence indicates that the MPT generation does not seem to be a function of the presence of shock waves. It is also shown that fan “broadband” noise is not broadband in character and could be attributed to the modulation of the blade-passing-frequency tones, their sub- and higher harmonics.
Comments on “Lowest Natural Frequencies of Elastic Hinged Arcs” [E. Volterra and J. D. Morell, J. Acoust. Soc. Amer. 33, 1787–1790 (1961)]
Authors: Romanelli Enrique
Published: October 2005

This letter discusses the effect of variable curvature in the mechanical behavior of arc-type structures.
Elastic Constants and Acoustic Absorption Coefficients in MnO, CoO, and NiO Single Crystals at Room Temperature
Authors: Uchida Naoya , Saito Shoichi
Published: October 2005

Sound velocity and absorption coefficient have been measured for three antiferromagnetic crystals—MnO, CoO, and NiO—at 23±1°C by the pulse superposition method and the pulse-echo method, respectively. Elastic constants have been calculated from the velocity data: c11 = 22.20, c12 = 10.99, c44 = 7.83 for MnO: c11 = 25.56, c12 = 14.36, c44 = 8.03 for CoO; and c11 = 27.0, c12 = 12.5, c44 = 10.5 for NiO (in 1011 dyn/cm2). The absorption coefficients are found to be proportional to square of frequency between about 60 and 500 MHz for MnO and CoO and between 10 and 50 MHz for NiO. The absorption of the shear wave is of comparable order to that of the longitudinal wave in the paramagnetic phase (MnO and CoO), and this fact suggests that single-ion magnetostrictive interaction rather than the volume magnetostrictive interaction is a dominant cause for the acoustic attenuation in these materials.
Passbands for Acoustic Transmission in an Idealized Drill String
Authors: Barnes Thomas G. , Kirkwood Bill R.
Published: October 2005

A comparative analysis is given for zero-mode transmission of torsional and longitudinal harmonic waves in an idealized drill string of uniform pipe sections with uniform coupling joints. Multiple passbands are shown to exist with successively increasing and then decreasing bandwidths. The longitudinal-wave passbands have the wider maximum pass bandwidths but successively occur at higher frequencies where a non-idealized system may have more attenuation.
Influence of Material Properties on Rayleigh Critical-Angle Reflectivity
Authors: Becker F. L. , Richardson R. L.
Published: October 2005

This paper extends the investigation of critical-angle phenomena and investigates the relationships between material properties and the condition (F0) for which zero reflectivity occurs. It was found that material attenuation, density, and velocity all influence F0. Graphs are presented for several materials from which the reader may determine F0 for a particular sample. Measurements which further verify the accuracy of the model, which we have used in these calculations, are also presented.
Tables of Rectangular Piston Radiation Impedance Functions, with Application to Sound Transmission Loss through Deep Apertures
Authors: Burnett David S. , Soroka Walter W.
Published: October 2005

Extensive and highly accurate tables have been calculated for the radiation impedance functions of a rigid rectangular piston mounted in a rigid infinite baffle radiating into a half-space. This was accomplished by developing a numerical technique of general applicability which yields a highly efficient computer algorithm. The latter computed 3792 highly oscillatory integrals containing branch point singularities, each to 7D accuracy, in a total of 74 sec on a CDC 6400 computer.
Scattering of a Transient Acoustic Wave by an Elastic Cylindrical Shell
Authors: Geers Thomas L.
Published: October 2005

A plane acoustic step wave traveling through an infinite fluid medium is scattered by an infinite, elastic, circular cylindrical shell whose axis is parallel to the wavefront of the incident wave. The resulting transient acoustic field is studied through the use of temporal convolution techniques in conjunction with wave front analysis. Computed pressure histories are presented for various points in the fluid. The field produced by the cylindrical shell is compared with those produced by a fixed rigid cylinder and a cylindrical cavity. Attention is given to the nearfield pressure reduction capability of the cavity.
Applications of Matched Asymptotic Expansion Methods to Acoustics. I. The Webster Horn Equation and the Stepped Duct
Authors: Lesser M. B. , Lewis J. A.
Published: October 2005

Modern perturbation theory in the form of the method of matched asymptotic expansions is applied to the problem of long-wavelength acoustics in ducts. The relatively simple problem of a duct discontinuity is used to illustrate the method. It is shown that away from the discontinuity the leading term in the asymptotic expansion for the pressure satisfies the Webster equation, and in a “boundary layer” around the discontinuity the leading terms satisfy the Laplace equation. A large amount of attention is spent on the problem of matching expansions. The results obtained are shown to agree with those found by more intuitive means and the groundwork is laid for some more challenging problems where intuition is less reliable.
Liquid Sodium in a Sinusoidal Pressure Field Including Gas Effects
Authors: Hammitt F. G.
Published: October 2005

The possible influence of inert gas contained within the liquid upon nucleation in a sodium-argon system to which a sinusoidal pressure wave of selected frequencies (14.5–24.5 kHz) was applied has been investigated. The system consists of a beaker of molten sodium below an argon blanket into which is inserted a “vibratory horn” of the type commonly used for the study of cavitation. Nucleation threshold results covering the temperature range 500°–1500°F were previously reported. The present paper concludes that, even though gas-in-liquid solubilities are very low compared to air-water systems, there is adequate dissolved gas to provide a large number of suitably sized nuclei within the critical region. However, there is no mechanism for the transfer of this dissolved gas to the entrained microbubbles necessary for nucleation, except through rectified diffusion, which is shown to be possible only at very high temperatures (≳1000°F) beyond the range of usual interest in engineering systems. Hence, the nuclei which must be present to justify the observed threshold values must be entrained from the free surface, or introduced as unwetted solid impurities in the filling process.
Ray Acoustics and Fermat's Principle in a Moving Inhomogeneous Medium
Authors: Uginčius Peter
Published: October 2005

A different formulation is presented in terms of an ordinary second-order vector differential equation for acoustic rays in a three-dimensional medium moving with an arbitrary velocity (either subsonic or supersonic) and having an arbitrary index of refraction. It is given in terms of a canonical independent variable and is equivalent to Keller's Hamiltonian formulation [J. B. Keller, J. Appl. Phys. 25, 938–947 (1954)]. Its major advantage is that it lends itself readily to the construction of Fermat's principle. An explicit Lagrangian is constructed for this problem from which a generalized Fermat's principle is derived. An error in an earlier publication [P. Uginčius, J. Acoust. Soc. Amer. 37, 476–479 (1965)] is corrected, and it is shown that this error disappears when the velocity of the medium is small compared to the speed of sound. In that case, and with the further restriction of planar rays, an expression is derived for the curvature of the rays in terms of the velocity, speed of sound, and their gradients.
Correlation of Reverberant Sound Fields Using a k-Transform Technique
Authors: Donato R. J.
Published: October 2005

A transform method is described for calculating the spatial correlation for various kinds of acoustic fields. The method emphasizes the equivalence between using a k-number approach for specifying a sound field and the synthesis of a sound field as a summation of a series of plane waves.
Reflection Coefficients for Acoustic Waves Interacting with Stratified Media
Authors: Kong J. A.
Published: October 2005

Reflection coefficients for acoustic waves interacting with stratified media are obtained in closed form and expressed in terms of continuous fractions. A numerical example is given for the three layer case.
Auditory Temporal Integration at Relatively High Masked-Threshold Levels
Authors: Gengel Roy W.
Published: October 2005

The clinical literature indicates that some persons with sensorineural hearing impairment show temporal integration functions that have relatively flat slopes when compared to subjects (Ss) with normal sensitivity. It is not clear whether temporal integration functions with reduced slopes are due to sensorineural hearing impairment per se, or to the relatively high levels of signal required to measure the thresholds of these hearing-impaired Ss. Therefore, temporal integration functions were obtained from four normal Ss in the presence of a masking noise of sufficient over-all level (87 dB SPL re 0.0002 dyn/cm2) to simulate moderate to severe hearing loss. The results indicate that temporal integration functions with a reduced slope are a consequence of sensorineural hearing impairment and are not due to the relatively high levels of signal required to measure threshold.
Effect of Signal Frequency on the MLD for Uncorrelated Noise
Authors: Robinson Donald E. , Dolan Terrence R.
Published: October 2005

Rabiner, Laurence, and Durlach [J. Acoust. Soc. Amer. 40, 62–70 (1966)] reported that the masking-level difference (MLD) for uncorrelated noise with signals in-phase and reversed in-phase at the ears was independent of signal frequency for frequencies between 150 and 1000 Hz. Since all other “MLD conditions” show marked signal-frequency effects, and since the E-C model predicts that such effects will also occur with uncorrelated noise, the present study reinvestigates the effect of signal frequency on the MLD for uncorrelated noise. The results indicate that the MLD for NUS0 decreases with increasing signal frequency.
Simultaneous Two-Channel Signal Detection. II. Correlated and Uncorrelated Signals
Authors: Sorkin Robert D. , Pastore Richard E. , Pohlmann Lawrence D.
Published: October 2005

Two-channel auditory signal detection was investigated with narrow-band noise signals masked by independent, binaurally uncorrelated noise. The two-channel tasks included conditions where the signals in each channel were correlated, uncorrelated, or opposite in phase. No significant differences were observed between the single-channel conditions and the two-channel correlated signal condition, but performance in the uncorrelated and 180° phase conditions was significantly poorer. A comprehensive analysis of cross-channel interaction indicated a cross-channel inhibitory or masking effect, which may be counteracted by the presence of lateralization cues. Constraints on signal detectability due to a limited processing capacity appeared to be negligible.