bluuebunny/crossref_metadata_2025 huggingface dataset:
Comments on “Perception of the Range of a Sound Source of Unknown Strength” [H. R. Hirsch, J. Acoust. Soc. Am. 43, 373–374 (1968)]
Authors: Greene David C.
Published: September 2005

The relative error to be expected in human range perception is quite large, even under good conditions, and should be considered in designing the experiment suggested by Hirsch in his Letter to the Editor entitled “Perception of the Range of a Sound Source of Unknown Strength” [J. Acoust. Soc. Am. 43 373–384 (1968)]
Reflection from a Plane Pressure-Release Surface
Authors: Mellen Robert H. , Browning David G.
Published: September 2005

An experiment showing finite amplitude distortion of an acoustic wave reflected from a plane, pressure release surface is described. The decay and regrowth of the waveform distortion agree qualitatively with plane wave theory except for the additional phase distortion associated with diffraction.
First Formant Transitions and the Perception of Synthetic Semivowels
Authors: Ainsworth W. A.
Published: September 2005

The method of studying speech perception by means of a formant synthesizer has been facilitated by the use of a small digital computer to control the synthesizer, record the listeners' responses, and analyze the results. This method has been applied to the perception of the semivowels /w, r, l, y/ in isolated CV syllables. It has been found that the frequency of the locus of the first formant greatly affects the quality of the perceived sounds, and that the shape of the first-formant transition is rather critical in the case of /l/ before open-front vowels.
Ultrasonic Attenuation in Thin Specimens Driven through Buffer Rods
Authors: Papadakis Emmanuel P.
Published: September 2005

A method is presented for measuring ultrasonic attenuation in thin solid specimens. The sample is bonded to one end of a buffer rod, and a transducer is bonded to the other end. All three elements must have plane parallel faces. The system is excited by an rf burst shorter than the round-trip travel time of the elastic wave in the buffer but longer than three times the round-trip travel time in the specimen. The specimen and its interface with the buffer act as a multiple-path elastic wave interferometer. The envelope of the returning echo in the buffer rod shows a stepwise amplitude modulation, one step per round trip in the specimen. The amplitudes of the first three steps are measured at rf frequencies at which the phase delay in the specimen is an integer multiple of π. From the amplitudes, the attenuation in the specimen and the reflection coefficient at the buffer-specimen interface are computed. Measurements can be made over a broad frequency band with a single transducer, so the frequency dependence of the attenuation can be determined. The method has been applied to thin brass samples. The results are presented and interpreted.
Nearfield of Time Harmonic Scalar-Wave Beams
Authors: Kritikos H. N.
Published: September 2005

By superimposing radiation spherical wave modes of the scalar-wave equation, a beam is formed. The farfield of the chosen beam is the truncated delta-function spectrum expanded on the basis of Legendre functions. By introducing an error criterion, the passage from the farfield to the nearfield is investigated. It is found that the nearfield along the direction of the main beam begins approximately at a radial distance rnf, given by rnf = 2G/k (G = GAIN, k = 2π/λ, λ is the wavelength) and for other directions, on the average, by r̄nf = 2√G/k. For both radial distances rnf, and r̄nf, the corresponding errors are bounded between 8% and 15%.
Ray Theory of the General Epstein Profile
Authors: Pedersen Melvin A. , White De Wayne
Published: September 2005

This paper presents the detailed mathematical properties and the ray-theory ranges, intensities, and travel times of the five-parameter Epstein profile with the parameters assuming all values capable of producing real velocities. Although examples represent the underwater-sound situation, results apply to any ray theory. The wealth of profile forms produces special cases requiring intricate analysis, but leads to more complete understanding of field theory. Analyses of rays that become horizontal at velocity extrema show little dependence on profile symmetry for the case of a velocity maximum, but a marked dependence for the case of a velocity minimum. This last is a point of significance apparently neglected in the literature covering ray-theory channels. Very steep, channeled rays, which become horizontal at very high (infinite) velocities, are shown to have a loop range πC(dZ/dC), where the velocity-slope product is evaluated as a limit at the infinite velocity. This expression, valid for profiles other than the Epstein profile, was suggested by examination of the hyperbolic cosine profile, which is a degenerate case of the Epstein profile.
Lateral Localization of 0°- or Near-0°-Oriented Speech Signals in Anechoic Space
Authors: Gardner Mark B.
Published: September 2005

Many studies have been made of man's ability to localize various types of sounds under various acoustic conditions. Of particular interest in loudspeaker reception is the ability to localize transient-type signals that originate at or near the intersection of the horizontal and median planes, i.e., in the region directly in front of the listener. The present study explores this ability for high quality speech signals in noise-free, anechoic space. It was found that, under such test conditions, the average error of lateral or angular localization was 1.5°. In addition, an average individual bias of 1.1° and a group bias of less than ±0.1° were also found. When the speech signals were presented over a wide range of levels from a source located among similar units displayed at various angles and distances from the observer, average angular shifts as large as 5° were observed in the apparent lateral position of the source.
Lateralization Threshold of a Signal in Noise
Authors: Houtgast T. , Plomp R.
Published: September 2005

Experiments are described in which the accuracy of the perceived lateral position of a signal against a continuous background of masking noise is determined. Both signal and masker consisted of octave bands of thermal noise, with the same center frequency of 500 Hz. The signal-to-noise ratio and signal duration served as parameters. The results can be understood on a statistical basis, the random fluctuations of nerve impulses playing an important rôle. The fluctuations due to “internal” noise are found to have a standard deviation of about 80 μsec. It appeared that, as a result of the increase of the sound-pressure level, the onset part of the signal contributes more to the lateral position perceived than the ongoing part does. The relation to the precedence effect is discussed. The statistical procedure underlying the accuracy of the lateral position perceived suggests an approach to the binaural masking level difference effect based on a masking pattern in the binaural-hearing mechanism.
Fundamental Frequency of Vibration of Rhombic Plates
Authors: Laura Patricio A. , Grosson Joseph
Published: September 2005

The present study deals with the determination of the fundamental frequency of vibration of simply supported rhombic plates. The results are tabulated and compared with values already available in the literature.
Phase Shift at a Turning Point?
Authors: Hayes Wallace D.
Published: September 2005

A confusion as to the phase shift at a turning point is shown to arise from a misunderstanding.
Relation between Intelligibility Scores for Four Test Methods and Three Types of Speech Distortion
Authors: Williams Carl E. , Hecker Michael H. L.
Published: September 2005

Several intelligibility tests are currently being used to evaluate speech-communication systems. Individuals engaged in the development of such systems would often like to compare the performance of a system evaluated with one test with the performance of another system that has been evaluated with a different test. A study has been conducted to examine and quantify the relation between scores obtained with four intelligibility tests (the Harvard PB-Word Test, the Fairbanks Rhyme Test, the Modified Rhyme Test, and the Harvard Test Sentences) for various levels of three types of speech distortion (additive speech-shaped noise, peak clipping, and vocoderization). Recordings by two adult male speakers of the different test materials were processed by the three distortion systems, and output recordings were administered to a group of listeners. The results of the study demonstrate that the relation between the various test scores is not unique but depends considerably on the type of speech distortion employed.
Absolute Sound-Velocity Measurement in Distilled Water
Authors: Carnvale A. , Bowen P. , Basileo M. , Sprenke J.
Published: September 2005

Data are presented giving the absolute sound-velocity values, measured in distilled water, over the temperature range of 0° to 40°C. Measurements were made over the frequency range of 10–70 MHz and path lengths of 0.6–5.1 cm.
Real-Time Debye-Sears Effect Spectrum Analyzer for Audio Frequencies
Authors: Slaymaker Frank H.
Published: September 2005

Time compressing a low frequency signal before it enters an ultrasonic diffraction cell allows a coherent light optical spectrum analyzer to function at audio frequencies.
Surface-Coupled Losses in Surface Sound Channels
Authors: Schulkin Morris
Published: September 2005

Evidence is presented that for a large body of surface sound channel propagation data, collected for ionic absorption, there is a residual attenuation coefficient that may be due to the combined effects of scattering by sea waves as well as bubble-layer absorption and scattering. The bubble-layer properties are wakelike and are dominant whenever they are present. The bubble layer losses are proportional to the square root of the product of acoustic frequency and mean wave height.
Absorption Characteristics of Nonlinear Acoustic Resonators
Authors: Ingard Uno
Published: September 2005

In the present note, which is a supplement to a previous paper [U. Ingard and H. Ising, J. Acoust. Soc. Amer. 42, 6–17 (1967)] on the nonlinear impedance of an orifice, the absorption characteristics of a nonlinear resonator absorber have been computed as a function of frequency for different values of design parameters and incident sound-pressure levels.
Effect of Changes in Stimulus Frequency and Intensity on Habituation of the Human Vertex Potential
Authors: Butler Robert A.
Published: September 2005

Interposed between periodic presentations of a 1000-Hz tone were stimuli of different frequencies and intensities. The amplitude of the vertex (V) potential to the 1000-Hz tone became larger as the frequency of the intervening stimuli departed progressively from 1000 Hz. It also became larger when the sensation level of the 1000-Hz tone was raised progressively above that of the intervening stimuli. The notion that changes in stimulus frequency and increases in stimulus intensity activate new neural units was adopted to explain the data. It was asserted that habituation of the V potential is greatest when the same neural units are repeatedly activated and least when new neural units are brought into play.
Interaural Amplitude Effects in Binaural Hearing
Authors: Sayers B. McA. , Lynn P. A.
Published: September 2005

The interaural amplitude difference, which will compensate the effect of interaural time difference for lateralization of a binaural image, has been further investigated with binaural transients low-pass filtered in order to minimize the risk of interference from multiple images arising with wide-band transients. Arguing from the effects observed, it is shown that if properties of cochlear neural responses found in the experimental animal are applicable in the human, a simple basis for explaining the main effects of amplitude difference in binaural listening would be available.
Sounding Mechanism of the Flute and Organ Pipe
Authors: Coltman John W.
Published: September 2005

Measurements on an artificially blown and mechanically excited flute head joint provide values of the complex acoustic back pressure generated by the blowing jet. The magnitude of the acoustic back pressure is calculable from the jet momentum and is approximately twice the static blowing pressure times the ratio of the lip-aperture area to the tube cross-section area. The phase of the induced back pressure relative to the oscillation volume velocity is determined by the lip-to-edge distance and the velocity of propagation of a wave on the jet. Adjustment of this phase is demonstrated to be the major means by which the flutist selects the desired mode of oscillation of the instrument. The efficiency of conversion from jet power to acoustic oscillation power is low (2.4% at 440 Hz) and is about equal to the ratio of particle velocities in the air column and the jet. Nonlinear (turbulent) losses are measured and are substantial. Stroboscopic views of the jet motion under explicitly stated oscillation conditions show the large amplitude of the jet wave and its phase relative to the stimulating acoustic disturbance.
Higher Modes of Longitudinal Wave Propagation in Thin Rods
Authors: Hutchinson James R. , Percival C. Mark
Published: September 2005

The propagation of the higher modes of longitudinal wave propagation in a dispersive elastic rod was investigated, both analytically and experimentally. The Pochhammer-Chree equation was solved for the mode shapes and group velocities as a function of wavenumber for the axisymmetric modes of longitudinal wave propagation. By integration of the axial displacement across a cross section, an indication of the planeness of the waves was obtained. In the experimental investigation, elastic waves generated in a colored-glass pressure bar by absorption of luminous energy from a Q-switched laser were measured using a thin piezoelectric crystal sandwiched in the pressure bar. The gross experimental results showed good agreement with the response as predicted by Love's modified wave equation. Higher modes of wave propagation not predicted by the one-dimensional theory were evident in the experimental record. These effects were related to the results obtained from the Pochhammer-Chree equation.
Normal Modes and Natural Frequencies of Combined Structures
Authors: Fourney W. L. , O'Hara G. J.
Published: September 2005

The normal modes and natural frequencies of a structure are determined from a knowledge of the normal modes and natural frequencies of its components parts. Only linear elastic structures resting on an immovable base are considered. The total structure is mentally broken down into a primary structure (part including base points) and one or more substructures. The displacement of the total structure is expressed as a series expansion of the scaled normal modes of the primary structure. The scaling factors involved are determined from the equilibrium equations of the primary structure with the secondary structures removed and replaced by their internal forces of connection.
Clipped-Digital Technique for the Sequential Processing of Sonar Signals
Authors: Nairn Donald
Published: September 2005

A signal-processing technique for pulsed sonar systems is described in which the sound field is treated as a series of point targets or highlights. Only the phase information of the narrow band echo signals is utilized, the outputs of the individual transducers being infinitely clipped and encoded directly in digital form. Subsequent operations performed on these numbers have the effect of steering the system to point in the direction of the strongest signal which illuminates the array at that particular instant. A linear phase-difference pattern is looked for, and numerical parameters are extracted that are a measure of how closely the received pattern matches the expected one. Signal detection is achieved by a hierarchy of thresholds operating sequentially on these parameters. Field trials of an experimental equipment in a shallow reservoir are described, and the results and measurements presented. The technique has also been analyzed and simulated on a digital computer, and a quantitative comparison between the efficiency of the proposed system as a signal processer, with that of conventional amplitude methods, is included.
On the Nature of the Sounds Produced within the Nest of the Oriental Hornet Vespa orientalis F. (Hymenoptera)
Authors: Schaudinischky L. , Ishay J.
Published: September 2005

The sounds produced in the nests of hornets were studied with the aim of determining their origin, physical parameters, and significance. For this purpose, hornet nests were placed in a specially built, acoustically insulated chamber, and the sounds produced within the nests were recorded and analyzed. Sounds were recorded from both adult hornets as well as from the late-instar(large) larvae. Those produced by the adults were mainly air borne and were identified as ventilation and food-gnawing sounds, while those by the larvae were for the most part solid borne and were interpreted as “hunger signals.”
Evaluation of Intensity-Modulated Recording for Ultrasonic Diagnosis
Authors: Reid John M.
Published: September 2005

An evaluation of available intensity-modulated recording systems has shown that they do not produce identical records from the same echo pattern. Differences in the records are due to two factors: the video time constants used and whether or not the zero-signal level or “base line” is stabilized. Several tests are described by which the processing inherent in a particular type of equipment can be assessed and by means of which these changes can be demonstrated. Because of these differences in apparatus, it appears that conclusions about the usefulness of ultrasonic diagnosis depend on the particular equipment.
Monaural Temporal Masking of Transients
Authors: Babkoff Harvey , Sutton Samuel
Published: September 2005

Using an experimental paradigm in which both masking and probe-click intensity are fixed and the temporal interval is manipulated, we investigated forward and backward masking for various intensities of masking and probe clicks. For both masking modes, monaural temporal masking is found (1) to increase logarithmically as a function of increasing masking-click level; and (2) to decrease as a function of increasing probe-click level. The amount of masking is greater for the forward than for the backward mode. Intense masking clicks and weak probe clicks produce the greatest difference between forward and backward masking. For both forward and backward modes, masking is found to be less than previously reported. A peripheral latency-intensity conversion hypothesis appears adequate to account for these data.
Effect of Sound on Subsequent Detection
Authors: Mulligan B. E. , Adams J. C.
Published: September 2005

An attempt is made to identify some of the sources of variability among data on after-effect masking. Suggestions are offered that may prove effective in eliminating or controlling this variability. In addition, generalities apparent in existing data are expressed as hypothetical equations, together with graphs that illustrate the assumed relationships. These hypotheses are discussed within the context of the assumptions underlying them.
Recovery from TTS in Children with Sensorineural Deafness
Authors: Macrae J. H.
Published: September 2005

The rate of recovery from TTS caused by hearing-aid use in four children with sensorineural deafness has been found to be 3–4 dB (log l) for at least 4 h after cessation of aid use. This corresponds closely to the “slow” rate of 4–5 dB (log l), found in recovery from high values of TTS in normal hearing subjects.
Comments on Papers Concerning Rectified Diffusion of Cavitation Bubbles
Authors: Hsieh D. Y. , Plesset M. S.
Published: September 2005

It has been shown by Safar that a theory of rectified diffusion when combined with a linearized analysis of the bubble dynamics gives an adequate description of threshold phenomena. The value of an explicit formula for the process is emphasized.
Correlation of Naturally Occurring Infrasonics and Selected Human Behavior
Authors: Green J. E. , Dunn F.
Published: September 2005

An initial attempt is made to determine whether infrasonic waves generated by storms of distant origin affect local human behavior. Severe storm activity in North America was compared with the automobile accident rate and the rate for absenteeism among school children in the area of Chicago Illinois during the first 28 days of May 1967. The results suggest that a correlation may exist between the presence of infrasonic disturbances in the Chicago area and changes in selected human behavior. It is urged that more comprehensive studies of this nature be carried out.
Functional Changes in the Ear Produced by High-Intensity Sound. I. 5.0-kHz Stimulation
Authors: Price G. Richard
Published: September 2005

Sounds of sufficient intensity and duration can produce decrements in the cochlear microphonic (CM). It was the purpose of these experiments to determine the extent of such changes and the rate at which they occurred. Cat ears were exposed to 5.0-kHz tones at intensities from 99 to 138 dB SPL (re 0.0002 μbar) for periods totaling 80 min. Losses in CM sensitivity (measured with a round-window electrode) occurred for tones ranging from 0.1 to 10 kHz with the greatest losses at 3.0 or 4.0 kHz. Changes occurred at a rate that was linear in time for the lower intensities and linear in time at the higher intensities.
Farfield Radiation from an Infinite Elastic Plate Excited by a Transient Point Loading
Authors: Magrab Edward B. , Reader Wayne T.
Published: September 2005

An expression is obtained for the farfield pressure radiated by a thin elastic plate bounded on one side by a fluid medium when the plate is excited by a time-varying point load. Both the fluid and the plate are considered to be infinite in extent. The solution is obtained with the use of transform theory to solve the coupled differential equations describing the transverse motion of the plate and the velocity potential in the fluid: A Hankel transform is used on the spatial coordinate and a Laplace transform on the temporal variable. The inverse Hankel transform is evaluated using the saddle-point integration technique. The inverse Laplace transform is expressed as a convolution integral that is evaluated for the case when the point load is a short tone burst.
Free Vibration of Laminated Orthotropic Cylindrical Shells
Authors: Dong Stanley B.
Published: September 2005

Vibration characteristics of thin laminated orthotropic cylindrical shells are investigated. The theory, based on the Kirchhoffean hypothesis regarding deformation, can accommodate shells composed of an arbitrary number of bonded layers, each with a different thickness and different elastic orthotropic properties. Donnell-type equations expressed in terms of the reference surface displacements are employed, and the effects of initial extensional forces in the shell are included. The frequency equation for a simply supported cylinder is derived. Next, an iterative procedure for determining the natural frequencies of a shell under an arbitrary set of homogeneous boundary conditions is described in detail. Specialization of present results to laminated orthotropic plates is indicated.
Natural Frequencies and Modes of Skew Membranes
Authors: Durvasula Somayajulu
Published: September 2005

Natural frequencies and mode shapes of a wide range of skew membranes are obtained by the Rayleigh-Ritz method expressing the deflection as a double Fourier sine series in oblique coordinates. Since the eigenvalues of a polygonal simply supported plate are the squares of the eigenvalues of a polygonal membrane of the same geometry and the eigenfunctions are identical, the results of the present paper readily provide the vibration characteristics of simply supported skew plates as well. This detailed study revealed interesting features like the skew angle splitting the degenerate frequencies of rectangular membranes into distinct ones and the “frequency crossing” of some modes that belong to opposite symmetry groups of the skew membrane. With changing skew angle, the nodal patterns of some modes undergo a gradual change to other totally different patterns. Since, for some modes the diagonals happen to be the nodal lines, such modes can be interpreted as the appropriate modes of the corresponding triangular membrane and consequently, of triangular simply supported plates.
Transmission Characteristics of Conical and Cylindrical Shells under Lateral Excitation
Authors: Kana Daniel D. , Hu William C. L.
Published: September 2005

A theoretical and experimental study is presented for determining the steady-state frequency response of laterally excited truncated cones and cylinders in a low to moderate frequency range. The theoretical results are formulated in terms of forward transmission matrices, although relationships are reviewed which allow application of the results for impedance or admittance formulations as well. Expressions for the 4×4 matrices of transmission for coupled bending-shear displacements are developed by means of the membrane theory of thin shells. The results are then applied to the case of laterally excited shells that support a rigid top mass. Input and transfer coupled impedances are calculated and compared with experimental observations for 30° and 15° cones and a cylinder. Over-all comparison of the results indicates that the membrane theory provides a reasonable approximation for determining response characteristics, but some definite deficiencies remain unexplained.
Deep-Sea Ambient-Noise Statistics
Authors: Arase T. , Arase Elizabeth M.
Published: September 2005

The statistics of ambient noise in the ocean have been investigated for a single hydrophone at 5200 ft and 14 300 ft. Five frequencies in a 13-oct bands were used in the range from 100 to 1600 Hz. Amplitude samples were taken every 20 msec and were recorded digitally. The data were analyzed in blocks of 500, 1000, and 2000 sample points. Distribution functions and moments were computed up to the fourth moment and the data were tested as to their normality at the 95% and 99% acceptance level using moment tests for skewness and kurtosis and the one-sample Kolmogorov Smirnov test. The two-sample Kolmogorov-Smirnov test was used to test for stationarity. A greater percentage of the smaller samples, i.e., 500 points, fall within the 95% acceptance interval for normality than the longer samples, thus confirming the nonstationarity of ambient sea noise. More than half of all the samples tested were found to be normal.
On the Validity of Laryngeal Photosensor Monitoring
Authors: Coleman Robert F. , Wendahl Ronald W.
Published: September 2005

A comparison between ultrahigh speed photography and photocell monitoring of the larynx is presented. The authors question the contention that photosensors accurately represent glottal area functions.
Time Scaling and Short-Time Spectral Analysis
Authors: Gambardella G.
Published: September 2005

If F(l) and F(ω) are a pair of Fourier transforms, then the property holds that time scaling corresponds to frequency scaling (by an inverse factor) and vice versa. The extension of this property to the case of the short-time Fourier integral F(l,ω) is investigated. It is found that the property does not hold for most conventional spectrum analyzers, whereas it holds for an interesting class of spectrum analyzers including the model of that special analyzer that is the peripheral auditory system.
One-Dimensional Wave Propagation through a Short Discontinuity
Authors: Kenner Vernal H. , Goldsmith Werner
Published: September 2005

The one-dimensional transmission and reflection laws for a change in section have been employed to analyze wave propagation in two elastic circular cylinders with discontinuities resulting from either the insertion of a short wafer of different acoustic impedance between or the eccentric junction of the bars. Appropriate experiments using aluminum cylinders and semiconductor strain gauges have been carried out, and good correlation of the results has been obtained.
Coherence of Acoustic Signals Reradiated from the Time-Varying Surface of the Ocean
Authors: Parkins B. E.
Published: September 2005

The space and time variation of a monochromatic acoustic plane wave reradiated by the moving, rough surface of the ocean is described using coherence theory. The complex degree of coherence of the pressure field is calculated approximately for the extreme cases of slightly rough and very rough surfaces. For both of these cases, the results are specialized to the situation of a wind-generated sea described by the Neumann-Pierson directional wave spectrum, and the dependencies of the coherence upon surface roughness and the angles of incidence and observation are shown. For the case of a slightly rough surface, the reradiation is principally a reflection, and the coherence in the direction of specular reflection is the same as that for a smooth surface. Away from this direction, there is scattering, and the coherence depends upon the surface roughness. For very rough surfaces, there is diffuse scattering in all directions with no reflection, and the coherence depends upon the surface roughness for all angles of observation.
Vibrations of Circular Cylindrical Shells Due to Gyroscopically Induced Inertia Loads
Authors: Kessel P. G. , Schlack A. L.
Published: September 2005

An analytical study is described for both open and closed circular cylindrical shells subjected to gyroscopically induced inertia loads. The shells are considered to be spinning at a constant rate about their longitudinal axis of revolution, which is simultaneously precessing at a constant rate at a fixed angle of nutation. Based on shallow-shell theory and assuming a dominantly transverse deformation, the equations of motion are formulated for this type of loading. These equations are found to contain distributed harmonic inertia forces whose amplitude and frequency are dependent on the precessional and spin angular velocities, respectively. The solutions of these equations of motion show that the natural frequencies of the shell are reduced by both the spin and precessional angular velocities and that only certain modes of vibration will respond to the gyroscopically induced inertia loading. It is also shown that the reduction in natural frequencies can become important for very shallow shells.
Turbulent-Flow-Excited Vibration of a Simply Supported, Rectangular Flat Plate
Authors: Strawderman Wayne A. , Brand Ronald S.
Published: September 2005

An analytic solution is obtained for the plate-velocity statistics of a turbulent-flow excited, simply supported, rectangular flat plate. The radiated acoustic pressure is neglected as contributing to the plate excitation, leaving only the turbulent-boundary-layer pressure fluctuations as the exciting force. The mathematical model for the turbulent-boundary-layer pressure statistics is based on that of Corcos, which agrees well with experiment. Plate-velocity statistics are expressed in the forms of dimensionless cross-power spectral and power spectral densities. Plate-velocity-spectral and cross-spectral densities were obtained with a digital computer for selected flow and plate parameters. From these computed dimensionless spectra, effects of major parameters on the plate-velocity statistics were determined. A “peak spectrum,” constructed by connecting major spectral peaks of the plate-velocity-spectral density, proved to be a useful engineering concept, inasmuch as knowledge of the “peak spectrum” is equivalent to knowledge of the maximum plate velocity spectral density for a given set of input parameters. The computed dimensionless plate-velocity “peak spectrum” compares well with “peak spectra” constructed from available experimental data.
Spoiler-Generated Flow Noise. II. Results
Authors: Gordon Colin G.
Published: September 2005

In an earlier paper [J. Acoust. Soc. Amer. 43, 1041–1048 (1968)], an experiment was described in which the noise radiation from flow spoilers inserted within a jet pipe was studied. In the present paper, we present detailed results of this study. We present also an analytical model of spoiler-generated sound that suggests the form of a prediction scheme. Data are presented on level, spectrum, and directivity of the radiated sound power.
Optimum Arrays and the Schwartz Inequality
Authors: Cox Henry
Published: September 2005

Optimum processors for detection of known and random signals in noise using an array of sensors are derived. It is shown how the Schwartz inequality may be used to solve the problem of maximizing the detection index in both cases. This approach provides both the optimum filter functions and the performance of the optimum processor simply and directly. Narrow-band signal assumptions are avoided.
Lengthening of Shock Waveforms Caused by their Propagation to High Altitudes
Authors: Daniels Fred B.
Published: September 2005

Expressions are given for the lengthening of shock waveforms that is caused by their travel upwards to high altitudes. Numerical values are computed for specific examples and pronounced lengthening of the waveform is found to occur. In particular, the N wave from a supersonic transport (SST) is lengthened to a point where it may be a source of interference to geophysicists observing infrasound of natural origin.
Prevalence of Impaired Hearing and Sound Levels at Work
Authors: Botsford James H.
Published: September 2005

The hearing deficiency of a group may be described in terms of the percentage having impaired hearing in order to focus attention on the abnormalities of medical significance. The prevalence of hearing impairment for speech, as defined by the medical profession, was determined for various populations using published hearing survey data. The incidence of hearing impairment was found to increase with age in all populations and also with A-weighted sound levels in the groups exposed to harmful noise at work. Curves were drawn for estimating the net increase in incidence of hearing impairment resulting from exposure to various A-weighted sound levels at work. They show that each decibel of occupational noise above 84 dBA increases the prevalence of impaired hearing by approximately the same amount as would 1 yr of aging. The curves also indicate that noise exposures that do not exceed the limits currently recommended should cause few additional cases of hearing impairment.
Radiation Characteristics of Spherically Symmetric, Perfect Focusing Acoustic Lenses
Authors: Boyles C. A.
Published: September 2005

It was shown in a paper by Morgan [J. Appl. Phys. 29, 1358–1368 (1958)] that there exist an infinite number of spherically symmetric, perfect-focusing lenses of which the Luneburg lens is but one example. Using the Helmholtz formulation of diffraction theory, we examine the farfield radiation characteristics of these lenses for both the case of an omnidirectional source and a particular directional source.
Wave Theory of an Acoustic Luneburg Lens. II. The Theory of Variable Density Lenses
Authors: Boyles C. A.
Published: September 2005

It was shown in Part I [J. Acoust. Soc. Amer. 43, 709–715 (1968)] that the wave equation for an acoustic Luneburg lens is ∇2p − (1/ρ)∇ρ⋅∇p = (nL2/c02)∂2p/∂f2, where p is the pressure, ρ the density, c0 the constant speed of sound in water and nL2 = 2−r2/a2 Luneburg's index of refraction. Here r is the radial distance measured from the center of the lens and a is the radius of the lens. Also, we have in general that nL2(r) = c02ρ(r)κ(r), where κ(r) is the compressibility. In Part I, the solution of the wave equation was obtained for plane-wave irradiation when ρ is constant. In this paper, we first obtain the solution to the wave equation for plane-wave irradiation when ρ(r) = nL2(r)/c02κ, κ being constant. Then the general case is examined when ρ(r) is an arbitrary function of position. It is found that at low frequencies, the speed of sound is affected by the presence of ∇ρ. while at high frequencies, this effect is negligible. Consequently, a completely arbitrary choice of ρ(r), even though κ(r) is chosen so that ρ(r)κ(r) − nL2/c02, could destroy the perfect focusing property (no spherical aberration) of the lens at low frequency. Therefore, conditions are established for ρ(r) so that the lens will retain its perfect focusing property at all frequencies.
Experimental Study of Aerodynamic Sound from a Rotating Disk
Authors: Chanaud Robert C.
Published: September 2005

The sound generated aerodynamically by a relatively smooth disk rotating in its own plane was measured in an anechoic room. The sound field was broad band owing to random, acoustic, dipole sources caused by the turbulent-boundary-layer flow on the disk. The low-frequency part of the spectrum was due to a uniform distribution of pressure dipoles over the disk surface. The separated flow from the disk periphery had a well-defined periodic vortex development and was the cause of the low-frequency sound. The high-frequency part of the spectrum was due to a distribution of pressure dipoles very near the disk periphery confirming Powell's [J. Acoust. Soc. Amer. 32, 982–990 (1960)] prediction of edge noise. When the surface roughness was one-tenth the boundary-layer thickness, it was found that significant high-frequency sound was generated at the point of roughness, indicating that apparent shear-stress dipoles can be important sound sources. The sound-power level was found to be 70.5 Db for the relatively smooth disk.
Release from Multiple Maskers: Effects of Interaural Time Disparities
Authors: Carhart Raymond , Tillman Tom W. , Greetis Elizabeth S.
Published: September 2005

Masked thresholds for spondees were measured during 37 binaural listening conditions covering homophasic, antiphasic, parallel time-delayed, and opposed time-delayed listening in the presence of one to four competing maskers at three nominal masker levels (65, 75, and 85 dB SPL). Two of the maskers used were white noise modulated 4 times per second by 10 dB with a 50% duty cycle; the modulation patterns were such that when the noises were combined they produced a continuous white noise. The other two were whole sentences spoken by different male talkers. Masking-level differences (MLD's) re homophasic performance in the same masker complex emerged for every one of the 28 conditions of dichotic listening. MLD's were slightly smaller in the presence of a single competing talker (with or without noise also present) than with two talkers, and MLD's were always largest for the antiphasic conditions (range 4.4–6.8 dB). MLD's for parallel delayed listening (entire masking complex given 0.8-msec lead to a single ear) averaged about 1 dB less than antiphasic conditions, ranging from 3.5 to 6.6 dB. MLD's for opposed time-delay conditions (0.8-msec delays given to all portions of the masker complex but not all masker signals delayed to the same ear) reduced the MLD another 0.6 dB from the antiphasic conditions on the average (range 2.6–6.4 dB). Since subjective separation of competing signals was more definitive during opposed time delays than during either parallel time delays or antiphasic presentation, but since MLD's were smaller during opposed time delays than in the companion dichotic conditions, this study indicates anew that escape from masking and lateralization of signal origin, while depending on common input information, are separate capacities involving two different neurological mechanisms. These findings also suggest that listening in interaurally complex conditions brings into play phenomena that are not covered by contemporary theories of masking.
Rayleigh Waves on Curved Surfaces
Authors: Rulf Benjamin
Published: September 2005

Rayleigh waves, which are elastic surface waves occurring at the interface between a solid elastic body and vacuum, are investigated. The exact solution of some canonical elastodynamic problems in a circular cylindrical geometry is given, from which the Rayleigh wave contribution is isolated. The dispersion—i.e., the dependence of the velocity of propagation of these waves on the local radius of curvature (of the interface)—is investigated. The propagation velocity diminishes as the ratio between wavelength and radius of curvature diminishes, reaching an asymptotic value at “zero wavelength.” A comparison is made with the small-wavelength asymptotic approach of Keller and Karal, which does not take dispersion into account. It is found that the effects of dispersion should not be ignored down to rather small wavelengths. Moreover, it is found that there occurs a “critical” or “cutoff” wavelength, above which no proper Rayleigh wave can exist. Thus, a Rayleigh wave that propagates on an interface of variable curvature towards a point of minimum radius may be scattered and partially transformed into body waves.
Influence of Reed Motion on the Resonance Frequency of Reed-Blown Wood-Wind Instruments
Authors: Nederveen C. J.
Published: September 2005

When vibrating, the needs of wood wind instruments displace an amount of air that shifts the resonance frequency of the instrument in the same way as does a mouthpiece cavity. In cylindrical instruments, this shift corresponds to an effective lengthening of the resonating tube. In conical instruments, the shift is strongly frequency dependent and it is essential for bringing first and second mode in tune.
Ultrasonic Method for Determining Thermodynamic Properties of Liquids with Results for Mercury
Authors: Stallard J. M. , Rosenbaum I. J. , Davis C. M.
Published: September 2005

An ultrasonic method for measuring thermodynamic parameters in liquids has been developed. By the pulse-repetition technique, the velocity of sound is determined in a cylindrical sample of fixed length. These data are then used to determine the change in height of a similar cylindrical sample of variable length. A preliminary investigation in mercury was accomplished to evaluate the technique. Thermal expansion and isothermal compressibility data are presented over the ranges 20°–90°C in temperature and 1–2000 bars in pressure. Estimated accuracies for thermal expansion and isothermal compressibility at 2000 bars are 1% and 3%, respectively.
Some Simple Modes of Wave Propagation in an Infinite Piezoelectric Plate
Authors: Bleustein Jeffrey L.
Published: September 2005

Exact solutions of the equations of the fully coupled linear theory of piezoelectricity are obtained for some simple types of two-dimensional waves in an infinite plate. It is shown that the coupling of the mechanical and the electrical fields can give rise to dispersion curves with complex branches and to waves that are largely confined to the region near the major surfaces of the plate.
Transient Interaction of Plane Acoustic Waves with a Spherical Elastic Shell
Authors: Huang H.
Published: September 2005

The problem of the transient interaction of plane pulse waves and an elastic spherical shell is solved exactly within the scope of linear acoustic and thin shell theories and within the limit of series solution. Detailed numerical results for the transient and vibratory responses of the shell are presented, and some interesting features of the transient wave shell interaction are revealed.
Observations of Fluctuation of Transmitted Sound in Shallow Water
Authors: Urick R. J. , Lund G. R. , Bradley D. L.
Published: September 2005

An 1120-Hz CW sound source was placed on the bottom in 60 ft of water off Fort Lauderdale, Florida. The sound from the source was monitored by a number of hydrophones placed on the bottom about 5000 ft away in the direction parallel to the shore. The received sound was observed to be unsteady, and to exhibit fluctuations of two kinds. One fluctuation had a periodicity of 3 to 4 sec, the same as that of the sea and swell in a 5- to 15-kt wind, and was accompanied by phase-difference fluctuations between hydrophones. The other had a periodicity the same as that of the tides, with fades of 15 dB or more occurring at the times of low water. This tidal variation has been accounted for by both a simplified form of normal mode and by image theory in terms of the interference between the first few modes or rays responsible for the transmission.
Judged Noisiness of Modulated and Multiple Tones in Broad-Band Noise
Authors: Pearsons Karl S. , Bishop Dwight E. , Horonjeff Richard D.
Published: September 2005

Paired-comparison judgment tests, undertaken to investigate the subjective noisiness of single, modulated, and multiple tones plus noise, clearly confirm the need for corrections in calculating perceived noise levels of spectra containing strong discrete frequency components. The tone-correction procedures of Little and Kryter-Pearsons both provided a considerable improvement in calculating perceived noise levels that agreed with judgments. The tests indicate that the tone corrections may continue to increase in magnitude as a function of tone-to-noise levels even for levels greater than 25 dB as measured in 13-oct bands. However, the rate of increase diminishes for higher tone-to-noise levels. Little difference was found in the judged noisiness of unmodulated and either frequency- or amplitude-modulated tones, except at rates of 5 Hz, where the modulated tones were found to be more annoying because of envelope irregularities. For multiple tones, little difference was noted in the judged noisiness of harmonic and nonharmonically related tone complexes. There was also found to be little consistent trend in the judged noisiness of two- or five-tone complexes of the same frequency range, except for the relatively narrow frequency range of 110 oct where the five-tone complexes were judged slightly noisier than the two-tone complexes.
Significant Features in the Perception of (Hindi) Consonants
Authors: Ahmed Rais , Agrawal S. S.
Published: September 2005

Twenty-nine consonants in the initial position and 31 consonants in the final position of CVC syllables were studied for perceptual confusions. The error matrices for consonants in initial and final positions showed significant differences in the response. A quantitative procedure was adopted to ascertain which features were most significant for listeners, and whether or not these were similar in the initial and final positions. The amount of information transmitted in bits per stimulus was calculated for all features and for each feature separately. The data indicated that the rank order of the features is not similar in the two positions. A comparison with observations made by earlier workers and with a recent work in this laboratory on intelligibility of consonants in clipped speech provided further evidence to show that the initial and final vowel transitions play different rôles in the recognition of consonants.
Excitation of Vocal-Tract Synthesizers
Authors: Flanagan J. L. , Cherry L.
Published: September 2005

A method is described for representing voiced and voiceless excitation in the vocal tract. Three physiological factors suffice for synthesis of nonnasal speech: subglottal pressure, vocal-cord tension, and vocal-tract shape. Voiced excitation is obtained from an oscillator model of the cords. Voiceless excitation is produced by elements that approximate turbulent flow in the tract. These elements are controlled automatically by factors related to the acoustic volume velocity in the tract and the tract shape. Voiced, voiceless, and voiced-fricative sounds are synthesized from a vocal tract incorporating these sources. The whole system is computer simulated.
Cry Characteristics in Cleft-Palate Neonates
Authors: Massengill Raymond M.
Published: September 2005

Thirty babies with cleft lip/palates were tape recorded during crying. The tapes were analyzed by polygraph recordings and were rated for nasal severity by three speech pathologists. Results from the polygraphic analysis revealed that the older children had longer cries. The data suggested a trend toward correlation between the length of cry and the age of the child, and the judged nasality. Statistical analysis further indicated that babies with cleft lip, cleft palate, and cleft lip and palate were judged alike with regard to nasality.