bluuebunny/crossref_metadata_2025 huggingface dataset:
Subjective Assessments of the Speech Communication Papers Presented at the 80th Meeting of the Acoustical Society of America
Authors: Noll A. Michael
Published: October 2005

Prescoring based upon the material contained in abstracts was used to allocate presentation times for the papers in Speech Communication submitted for presentation at the 80th Meeting of the Acoustical Society. After the papers were actually presented, their technical content, presentation quality, and discussion quality were judged. No casual relationships could be established between the prescoring and postjudging of the paper, although the papers allocated 15 min were judged statistically better in technical content than the papers allocated 5 or 10 min. It is hoped that this letter might entice others to conduct further experimentation and subjective assessment of different methods for improving professional meetings.
Quantitative Evaluation of a Lateralization Model of Masking-Level Differences
Authors: Hafter Ervin R.
Published: October 2005

A lateralization model is proposed in which binaural detection in those cases that produce a masking-level difference is of a shift in the spatial locus of the auditory image. The shift is presumed to be a function of interaural time and intensity differences in the signal-plus-masker; it is quantified as a weighted sum of these two differences, averaged across the observation interval. The model is applied to a broad range of experimental data in which detection is given as a function of interaural phase and amplitude differences in the signal. It is shown here that, when applied to noise-masked low-frequency detection, the lateralization model is identical in its predictions to the time-difference model of Jeffress (1965) and the equalization-cancellation model of Durlach (1963). However, when applied to noise-masked high-frequency detection and to detection of signals masked by pure tones, the lateralization model better describes the data.
Additivity of Forward and Backward Masking as a Function of Signal Frequency
Authors: Patterson James H.
Published: October 2005

Temporal masking of tones by clicks was investigated using a forward-masking paradigm, a backward-masking paradigm, and a combined backward and forward paradigm. The amount of temporal masking was found to decrease as a function of signal frequency for all three paradigms. In addition, the combined backward-forward masking paradigm produced much more masking than either the forward- or backward-masking paradigm alone, indicating a nonadditivity of forward and backward masking.
Masking of Tones by Transient Signals Having Identical Energy Spectra
Authors: Patterson James H.
Published: October 2005

The detectability of sinusoidal signals (1500 Hz) masked by brief signals having the same broad-band energy spectrum was determined. On the average, maskers with a relatively uniform envelope (low peak factor) produce more masking than maskers with a more peaked envelope. The amount of masking produced by individual maskers with a relatively uniform envelope is related to the short-time spectrum of the maskers. Changes of 10–15 dB in the detectability of sinusoidal signals were noted as a function of changes in the short-time spectrum of the masker. The ability of the auditory system to perform a short-time analysis of brief stimuli is supported by the results.
Amplitude and Time Jitter Thresholds for Rectangular-Wave Trains
Authors: Pollack Irwin
Published: October 2005

Thresholds were obtained for the absolute detection and the relative discrimination of amplitude variation (“jitter”), of time variation, and of combined amplitude and time variation of individual half-waves of auditory rectangular-wave trains. The results for amplitude variation alone, or for temporal variation alone, closely reflect previous obtained thresholds of temporal variation for monopolar pulse trains. Thresholds approaching 0.1% were obtained for long high-frequency trains. Additive models for the interaction of amplitude and time jitter were examined for the case of the discrimination of changes in amplitude or time variation alone, and for changes in combined amplitude and time variation for signals with both amplitude and time jitter. A description that reasonably describes their interaction assumes orthogonal representation with vector addition of amplitude and time variation.
Effects of Attenuation Step on Descending Békésy Threshold
Authors: Young I. M. , Harbert F.
Published: October 2005

For fixed suprathreshold starting intensities, Békésy thresholds were compared for interrupted tones, tones with 2.5-dB attenuation steps, and continuous tones with 0.25-dB steps in normal ears and those with cochlear lesions. Thresholds for interrupted tones were best, those for continuous tones were the worst, and those with an attenuation step of 2.5 dB were intermediate in both normal and pathological ears. The threshold difference between interrupted tones and tones with 2.5-dB steps are about two-fifths the magnitude of difference in threshold between interrupted tones and tones with 0.25-dB steps. In pathological ears, as the differences in threshold between interrupted tones and both stepped tones increased, the amount of separation between interrupted and continuous tone fixed-frequency Békésy trackings and tone decay also increased. As the differences in threshold between interrupted tones and 2.5-dB step continuous tones increased by 1 dB, threshold differences between interrupted tones and 0.25-dB step continuous tones increased by 2.3 dB in both normal ears and those with cochlear lesions. With high suprathreshold starting intensities, threshold differences for interrupted tones and continuous tones attenuated in discrete steps are probably due to normal and abnormal adaptation.
Airflow and Turbulence Noise for Fricative and Stop Consonants: Static Considerations
Authors: Stevens Kenneth N.
Published: October 2005

A number of speech sounds are generated by creating turbulent airflow in the vicinity of a constriction in the vocal tract. The equations relating the airflow through such a constriction, the pressure drop across the constriction, and the dimensions of the constriction are reviewed and are summarized in graphical form. Previous theoretical and experimental data on turbulence noise generation at a constriction or obstruction in a tube are described. These data are consistent with a model that represents a turbulence noise source in the vocal tract as an equivalent sound-pressure source whose magnitude is proportional to the pressure drop across the constriction or obstruction. The characteristics of the sound radiated from the mouth opening are determined by the source location and radiation characteristics, as well as by the properties of the source. The airflow and acoustic characteristics for various classes of speech sounds produced with turbulence noise at the glottis or at a supraglottal constriction are discussed in the light of these findings.
Underwater Sounds from the Blue Whale, Balaenoptera musculus
Authors: Cummings William C. , Thompson Paul O.
Published: October 2005

Powerful low-frequency sounds were recorded from blue whales, Balaenoptera musculus, off the Chilean coast. These three-part sounds lasted about 36.5 sec, and ranged in frequency from 12.5 to 200 Hz. The sounds occurred in a repetitive pattern that was interrupted as the whale came to the surface to breathe. We estimated that these moanings, in a 14- to 222-Hz band, were 188 dB re 1 μN/m2 (= 88 dB re 1 μbar) at 1 m. They are the most powerful sustained utterances known from whales or any other living source. This finding is especially noteworthy because it is doubtful if these animals, the largest ever to inhabit the earth, will survive man's overharvest.
Discrimination of the Interval between Two Brief Pulses
Authors: Pollack Irwin
Published: October 2005

The absolute detection of extremely short interpulse intervals (IPIs), demonstrated by Leshowitz, is extended to differential interval thresholds over a wide range of IPIs. Discrimination thresholds in the low microsecond region are obtained. The basis for microsecond threshold discrimination probably to be found in the discrimination of short-term spectral differences at high auditory frequencies.
Influence of Pulsed Masking on Spondee Words
Authors: Dirks Donald D. , Bower Deborah R.
Published: October 2005

Two experiments were designed to observe the effects of selected pulsed maskers on the intelligibility of spondee words and bisyllabic items. The bisyllabic items had the same general physical and phonetic characteristics as the spondees, but the linguistic structure of the items was modified. The results of the first experiment demonstrated substantial release from masking for spondee words during the 10- and 1-interruptions/sec conditions and an increase in masking effectiveness at the very slow pulsing rate of 0.67 and 0.5 ips. In the second experiment, the effectiveness of the pulsed maskers and the intelligibility functions for the bisyllabic items were similar to results obtained earlier with monosyllables rather than spondees.
An Improved Underwater Earphone
Authors: Schumann Juergen , Abbagnaro Louis A. , Bauer Benjamin B.
Published: October 2005

An improved underwater earphone, insensitive to depth, has been developed. This new transducer offers good efficiency and yields speech reproduction comparable to most air acoustic earphones. The earphone design provides tympanic, rather than bone-conduction, sensing, thereby providing directional signal information to the listener. Pairs of these devices have been used successfully in a directional communication system for underwater swimmers. Threshold levels and some man-earphone equal-loudness contours were obtained for this device.
Preferred Noise Criterion (PNC) Curves and Their Application to Rooms
Authors: Beranek Leo L. , Blazier Warren E. , Figwer J. Jacek
Published: October 2005

The noise criterion (NC) curves were developed both as a method for evaluating existing noise situations and as a means for specifying design goals for noise control. They have also influenced the N ratings used abroad. It has been demonstrated that if a background noise whose spectrum conforms to an NC-curve shape is deliberately generated, it does not sound to a listener as a pleasant or neutral noise, but is both “hissy” and “rumbly.” A recent tendency in consulting practice, therefore, has been to specify noise levels that are lower than NC curves at both low and high frequencies. Also, the original NC curves were derived using Stevens's Mk. I method of calculating loudness level from noise levels measured with the old octave bands, the lowest of which was the “below 75 Hz” band. A reexamination of the noise criterion curves has been undertaken using Stevens's Mk. VI method and the new octave bands. The result is a new set of curves, called “preferred noise criterion (PNC) curves,” having levels in the bands below 125 Hz and above 1000 Hz that are lower than those of the 1957 NC curves by 2–5 dB. The new set also takes into account the engineering realities of achieving the specified noise levels with conventional air-handling equipment. The results of a number of recent noise-control projects in building are presented for comparison.
Comments on “Experiments with the Raes Method for Producing Diffuse Sounds” [A. Behar and J. Menyhart, J. Acoust. Soc. Amer. 48, 854–855 (1970)]
Authors: Raes Auguste C.
Published: October 2005

Behar and Menyhart, in a recent study of a variation of a technique reported earlier by us [A. C. Raes, J. Acoust. Soc. Amer. 46, 831–834 (1969)], conclude that the method is not fully successful in reducing the need for a multiplicity of source positions in reverberant sound field measurements. We would point out that their study, although interesting in several respects, presents no information on effects of varying source positions, and thus sheds little direct light on the value of the new technique.
Household Noise Problems
Authors: Baade Peter K.
Published: October 2005

The difficulties in solving many of the noise problems in an average household are as much social and economic as technical. With many different parties being involved in the noise problem of even a single appliance, plea is made for uniform sound ratings of equipment, for information proper application and installation, and for realistic criteria on acceptable sound levels. Recent standards for performance ratings and application information of the Air-Conditioning and Refrigeration Institute are cited as an example of what an industry can do to further the communication of acoustical data between manufacturers, installers, and users of machinery.
Comment on the Optimum Use of Nulls in Beamforming
Authors: Rudnick Philip
Published: October 2005

Two recent communications are compared, and one is corrected.
Fifty Years of Ferroelectricity
Authors: Mason Warren P.
Published: October 2005

Developments in the field of ferroelectricity are traced from the discovery of the ferroelectric effect by Joseph Valasek in 1921 to its use in a variety of modern applications. Its appearance and utilization in different substances is discussed.
A Recursive Procedure for Computing the Nonlinear Spectral Interactions of Progressive Finite-Amplitude Waves in Nondispersive Fluids
Authors: Fenlon Francis Hugh
Published: October 2005

A method for computing nonlinear interactions between the spectral lines of progressive finite-amplitude waves in homogeneous media is developed via Burgers' equation. By means of Fourier analysis, this equation is reduced to a coupled set of ordinary nonlinear differential equations, which are then solved recursively using Airy's algorithm. The solution thus obtained has the form of a vector which initially contains the spectral amplitudes of the source waveform and is subsequently enriched by nonlinearly generated spectral components as the signal propagates through the medium. The utility of the method consists in the ease with which it can be implemented on a digital computer and its applicability to a wide variety of source waveforms.
Shock Beaming Capabilities of Hydrodynamic Conical Shock Tubes
Authors: Filler William S.
Published: October 2005

An experimental study was made of the shock wave projected into free water from the end of a hydrodynamic conical shock tube driven by a high explosive. Pressure-time measurements were made with small piezoelectric and piezoresistive gauges arrayed about two different shock tube configurations. For one tube, designed on a very small scale, results showed that a remnant of the sector shock front propagated undisturbed over the length of the water tank (20 cone lengths). This was demonstrated by the fact that attenuation with distance along the extended cone axis closely approximated the accepted relationship P ∝ R−1.13 for explosion shock waves in free water. On-axis data for the other tube whose shock wave energy was three orders of magnitude greater than the first, showed very rapid attenuation beyond the cone mouth. Both cone results are consistent with existing theory that defines the undisturbed shock front region in terms of cone parameters—length, angle, and amount of explosive—that affect shock energy and geometry. Results for the first cone on attenuation of pressure with angle to the axis also were consistent with the predicted angular extent of the undisturbed front region. At 30°, attenuation was about 75%.
Acoustic Radiation Impedance of Caps and Rings on Prolate Spheroids
Authors: Van Buren A. L.
Published: October 2005

The self-acoustic radiation impedance of cap-shaped and ring-shaped pistons conformal to a rigid prolate spheroidal baffle and vibrating with uniform normal velocity is calculated using prolate spheroidal wave functions. The necessary spheroidal functions are obtained using recently developed FORTRAN computer programs. Plots of the normalized radiation resistance and the normalized radiation reactance as functions of the acoustic size parameter h are presented for several different baffle shapes and relative piston sizes. The effect of the baffle size and curvature on the radiation impedance is shown to be small.
Sampling Statistics for a Cylindrical Mode
Authors: Waterhouse Richard , Chien Chi-Shing
Published: October 2005

The distribution functions are considered for the random sampling in space of a three-dimensional acoustic mode. These functions are of interest when it is desired to estimate either the total acoustic energy present in the space, from a finite number of sample values, or the driving-point impedance at an arbitrarily chosen point. Expressions are obtained for the probability density function (pdf) and cumulative function for a single mode excited in an ideal elastic fluid in a right circular cylindrical enclosure. Two kinds of axisymmetric mode are considered, those corresponding to the first zeros of the zero- and first-order Bessel functions. The distribution functions obtained are compared with those for modes in a rectangular enclosure [R. V. Waterhouse, J. Acoust. Soc. Amer. 47, 961–967 (1970)], and exhibit some novel and interesting features. For the cylindrical modes, the pdf's differ for each order of one type of mode, and in general have discontinuities, the number of which increases with the mode number. In both these respects the cylindrical modes differ from the rectangular modes.
Comments on “Beam Behavior within the Nearfield of a Vibrating Piston” [J . Zemanek, J. Acoust. Soc. Amer. 49, 181–188 (1971)]
Authors: Laura Patricio A.
Published: October 2005

The present letter discusses additional technical literature dealing with calculations of nearfield pressure induced by vibrating acoustic transducers.
An Accelerating Force on a String
Authors: Stronge W. J.
Published: October 2005

An infinitely long, perfectly flexible string is subjected to a transverse force that moves with arbitrary speed. The effect of the force accelerating through a resonant speed is determined. This invariably results in large deformations if the force is concentrated. With a distributed force, the deformations can remain small if the force accelerates through the resonant speed rapidly.
An Asymptotic Analysis of the End Mode in a Circular Disk
Authors: Tasi J.
Published: October 2005

An asymptotic solution is obtained for the end mode in a circular disk, using second-order plate theory. Variation of end displacement with radius is indicated, and estimates of midpoints of the plateaus in the frequency spectrum are found. The results of a three-dimensional elasticity solution are given for frequency and modal displacement and compare reasonably well with available experimental results.
Independent Multiple Oscillations of a Single Quartz Wafer
Authors: Van Empel F. J. , Massen C. H. , Arts H. J. J. M. , Poulis J. A.
Published: October 2005

Experiments are described which demonstrate that the frequency of different electronic oscillators can be independently controlled by electrode systems evaporated on a single quartz wafer. This arrangement can be used in several fields of applications, where the use of separate quartz wavers for the oscillators would imply errors due to temperature and other environmental differences.
Minimum Effectiveness of Isolation Mounts at High Frequencies
Authors: Wang W. M.
Published: October 2005

The effectiveness of one-degree-of-freedom vibration isolation mounts is examined. It is shown that, at high frequencies where standing-wave resonances occur in mounts and structural resonances occur in the machine and the foundation, there exists a functional lower bound of the mount effectiveness, regardless of machine and foundation impedance variations. This functional lower bound is obtained and its significance is discussed.
Investigation of Double-Diffusive Convection Using an Ultrasonic Pulse-Echo Technique
Authors: Kim M. G. , Lambert R. B. , Letcher S. V.
Published: October 2005

Propagation of ultrasound is investigated in an aqueous solution stratified by two solutes which diffuse at different rates. Both the finger interface and the diffusive interface are considered. Following correction for background absorption, edge effects, and refraction, attenuation of the order of 1.4 dB/cm is observed in the finger interface, while no attenuation is detected in the diffusive interface. The attenuation increases with frequency from 0.8 to 25 MHz. For higher frequencies, up to 42 MHz, the attenuation is constant. The loss is attributed to an as yet unspecified scattering mechanism.
Sound Pressure in Water from Source in Air
Authors: Young Robert W.
Published: October 2005

Sound pressure in the water under a point source overhead in air is shown by theory and experiment to propagate as from a virtual source situated (c1/c2) times the actual source height above the water and emitting unit-distance sound pressure that is (2c1/c2) times the actual unit-distance sound pressure, where c1 and c2 are the speeds of sound in air and water, respectively.
Reflections of Weak Shock Waves from Acoustic Materials
Authors: Cloutier M. , Devereux F. , Doyon P. , Fitchett A. , Heckman D. , Moir L. , Tardif L.
Published: October 2005

A number of materials having good acoustic absorption properties have been tested in order to determine their relative effectiveness in attenuating weak high-frequency shock waves propagating atmospheric air. Weak shock waves with an N-wave configuration of about 110-μsec duration were generated by rifle bullets flying 2400 ft/sec over samples of acoustic material supported on a metal plate, and the details of the reflection of these waves at the surface of the various materials were monitored by using shadowgraph-schlieren photographic techniques and pressure transducers. The urethane materials available gave a high amount of surface reflection compared to fiberglass materials of similar density. The least surface reflection was obtained with very low density (less than 1.0 lb/ft2 fiberglass).
Coherent Recombination of Acoustic Multipath Signals Propagated in the Deep Ocean
Authors: Williams Ross E. , Battestin Henry F.
Published: October 2005

The multipath acoustic impulse response of the deep ocean has been measured over a 250-NM propagation distance and has been used in an attempt to remove the multipath distortion of a broad-band signal propagated over the same range interval. The process can be considered a coherent recombination of multipath arrivals, or a deconvolving of the received signal from the ocean impulse response. The measured impulse response is cross correlated with the distorted received signal to produce an estimate of the transmitted signal. Cross correlating this estimate with a replica of the original signal, and comparing this result to a cross correlation of the distorted received signal with the replica, shows a significant improvement in the former. Sidelobes due to undesired arrivals have been reduced to the point that, with a suitably chosen threshold, the message resolution time can approach the system inverse bandwidth rather than the multipath spread time, an improvement in resolution time of more than an order of magnitude. The experiment also demonstrates short-term (e.g., 6-sec) stability of the ocean impulse response, without establishing an upper limit for this stability.
AERODYNAMIC FLOW NOISE INTERFERENCE IN ACOUSTICALLY LINED DUCTS
Authors: Mangiarotty R. A.
Published: October 2005

In the course of a study of the basic properties of acoustic linings for ducts transmitting air at high speeds, experimental evidence indicated that aerodynamic noise generated by the flowing air could limit the magnitude of noise attenuation inside the duct achievable by means of linings. A discussion of the matter leads to the conclusion that aerodynamic noise generated by the fluid flow could limit the maximum attenuation achievable.
Differences of Interaural Phase and Level in Detection and Lateralization: 250 Hz
Authors: McFadden Dennis , Jeffress Lloyd A. , Ermey Harold L.
Published: October 2005

A narrow band of noise (50 Hz wide centered at 250 Hz) was passed through a phase-shifting network and was then used as both masker and signal. The phase shifter permitted control over the phase angle α at which the signal and the masker were added. The masker was continuously present and was in-phase interaurally N0); the signal could be presented in-phase interaurally (S0) or 180° out-of-phase (Sπ). Detection data were taken for N0-S0, α = 0° (increments) and α = 180° (decrements), and both detection and lateralization data were taken for N0-Sπ for several values of α. A single-interval psychophysical method was used throughout. For all subjects for all values of α, the masking-level differences (MLDs) were positive and substantial. In the N0-Sπ conditions, two cues were available to the subject for all values of α except 0° and 90°—an interaural phase (time) difference and an interaural difference in level. Between α = 0° and α = 90 °, the two cues are consonant, but between α = 90° and α = 180°, the two cues are in opposition, i.e., one cue indicates that the sound source is to one side of the median plane while the other cue indicates that it is to the other side. Some subjects were more sensitive to one of these cues, and other subjects were more sensitive to the other cue; this fact was apparent in both their detection and their lateralization data. For each subject there was a value of α between about 120° and 170° at which detection performance was good while lateralization was nearly impossible.
Responses of Some Neurons of the Cochlear Nucleus to Tone-Intensity Increments
Authors: Smith Robert L. , Zwislocki J. J.
Published: October 2005

The study concerns units of the cochlear nucleus of anesthetized Mongolian gerbils. The incremental stimuli consisted of short tone bursts at the units' CF (characteristic frequency) superimposed on 250-msec pedestals of the same sound frequency and phase. The response firing rates were determined from PST (poststimulus time) histograms. In response to the pedestals, the maximum firing rate occurred at the tone onset and decayed subsequently to a steady state. The response to intensity increments was studied as a function of time delay from the pedestal onset to the increment onset. The incremental firing rate either remained constant or increased with the time delay, which means that the ratio between the incremental and pedestal firing rates always increased. The effect may be related to the psychophysical finding that intensity increments are the most difficult to detect when they occur at the pedestal onset.
Degradation of DNA in High-Intensity Focused Ultrasonic Fields at 1 MHz
Authors: Coakley W. T. , Dunn F.
Published: October 2005

Gassy and degassed aqueous solutions of DNA were treated ultrasonically while monitoring the field for discrete cavitation events. At irradiation intensities greater than about 500 W/cm2, transient cavitation is shown to be responsible for the observed reduction in molecular weight. At intensities of 200 to 288 W/cm2, degradation of DNA was observed which did not depend upon transient cavitation.
Quantitative Relationships between Ultrasonic Cavitation and Effects upon Amoebae at 1 MHz
Authors: Coakley W. T. , Hampton D. , Dunn F.
Published: October 2005

An amoeba, Hartmannella castellanii, which possesses many features typical of higher-order animal cells, was irradiated with 1-MHz ultrasound while suspended in ordinary growth medium and in one with increased viscosity. The ultrasonically produced cavitation was monitored and a strong correlation is found between the number of discrete cavitation events occurring and the decrease in cell numbers, on irradiating at 515 W/cm2 for 10 min. The growth of treated cells was also examined.
Comments on “Correspondence between Cochlear Microphonic Sensitivity and Behavioral Threshold in the Cat” [G. R. Price, J. Acoust. Soc. Amer. 49, 1899–1901 (1971)]
Authors: Dallos Peter
Published: October 2005

It is argued that the apparent covariance of cochlear microphonic (CM) and behavioral sensitivity is a result of the common dependence of both upon the middle-ear transmission characteristics and not an indication of the causal role of CM in hearing.
Comment on “Proposed Explanation of Synchrony of Auditory-Nerve Impulses to Combination Tones” [E. de Boer, P. Kuyper, and G. Smoorenburg, J. Acoust. Soc. Amer. 46, 1579–1581(L) (1969)]
Authors: Hall J. L.
Published: October 2005

Interval histograms are computed from a threshold-crossing model for auditory-nerve activity. The calculations do not resemble real nerve histograms measured for combination-tone frequencies. It appears unlikely that a threshold-crossing model can explain the synchrony of auditory-nerve impulses to combination tones.
Temporary Threshold Shifts Produced by Pure Tones and by Noise in the Absence of an Acoustic Reflex
Authors: Mills John H. , Lilly David J.
Published: October 2005

Six subjects with an acoustic reflex and six subjects without an acoustic reflex were exposed on separate occasions to a 710-Hz pure tone and to a 18-oct band noise with an upper cutoff frequency of 710 Hz. Both exposures were 10 min at 110 dB sound-pressure level. Temporary threshold shift (TTS) was measured at 1000 Hz. For the subjects with an acoustic reflex, the pure-tone exposure produced 10 dB more TTS2 than the noise exposure. However, for the subjects without an acoustic reflex, the pure-tone exposure and the noise exposure produced the same amounts of TTS. These results support the hypothesis that low-frequency pure tones produce more TTS than low-frequency bands of noise because of the differential effects of the acoustic reflex in responding to these two types of sounds.
Location of Slope Discontinuities in Glottal Pulse Shapes during Vocal Fry
Authors: Hamlet S. L.
Published: October 2005

Comparison of the speech waveform with ultrasonic signals from the larynx recorded simultaneously gives information about the temporal properties of the glottal source. Physiological information obtained with this technique corroborates the time relationships between speech output and excitation waveform found with inverse filtering.
Refraction and Attenuation of Sound by Wind and Thermal Profiles over a Ground Plane
Authors: Kriebel Anthony R.
Published: October 2005

There is a significant excess attenuation of sound traveling downwind within a typical turbulent shear profile due to the downwind refraction and spreading of the sound rays. This attenuation is in excess of that due to absorption by turbulent eddies, spherical spreading, and ground reflection. When the source and receiver are both located on the ground, the excess attenuation of the directly transmitted sound due to refraction is predicted to be uniform at −11 dB beyond a short range downwind of the source until a shadow zone is reached at a much longer range. This predicted excess attenuation decreases markedly with the elevation of the source and receiver, particularly at short range. There can be an indefinitely large number of reflected rays transmitted to a receiver downwind of a ground-level source, and the shallow reflected rays which skip off the ground a large number of times may have little excess attenuation, since they travel through the laminar sublayer where the velocity gradient is constant. There are several caustics formed downwind of a ground-level source. The results show that wind can easily cause anomalous recording of the sound-pressure level from freeways, airports, and other urban noise sources.
Natural Resonant Frequencies of an Oblate Acoustical Resonator
Authors: Chang C. T. M.
Published: October 2005

Natural resonant frequencies of oblate acoustical resonators with either perfectly soft or perfectly rigid boundaries are calculated by locating the zeros of Rmn(1)(−ih, iξ) and Rmn(1)′(−ih, iξ). These frequencies are normalized to those of the corresponding modes of a spherical cavity with the same volume and presented for various ratios of major to minor axes.
Passive Sonar Processing for Noise with Unknown Covariance Structure
Authors: Liggett W. S.
Published: October 2005

Passive processing is interpretation of the noise and noise like signals received by an array of hydrophones. Our model assumes that there is an important noise component about which very little is known, that the data are stationary, that a long data sample is available, that signal wavefronts are planar, and that the response of the array to plane waves is known. We propose a processor and compare it with high-resolution frequency-wavenumber spectrum analysis. Let F̂ denote an estimate of the spectral density matrix, and let H denote any spectral density matrix that corresponds to a noise field composed of uncorrelated plane waves. A reasonable estimate of the spectral matrix of the signals and ambient noise is a value of H for which F̂-H is positive semidefinite and trace H is maximized. The rationale for this estimate is closely related to a rationale for the estimate obtained by high-resolution frequency-wavenumber spectrum analysis (which is also called adaptive beamforming). The difference is that the former extracts the contribution from all directions at once, whereas the latter extracts the contribution from each direction separately. The former estimate rejects more unwanted noise than the latter.
Comments on “Speech Analysis and Synthesis by Linear Prediction of the Speech Wave” [B. S. Atal and S. L. Hanauer, J. Acoust. Soc. Amer. 50, 637–655 (1971)]
Authors: Flinn Edward A.
Published: October 2005

References to publications on linear prediction theory are suggested to complement those given by Atal and Hanauer [J. Acoust. Soc. Amer. 50, 637–655 (1971)].
Calibration of Condenser Microphones under Increased Atmospheric Pressures
Authors: Thomas William G. , Preslar Mack J. , Farmer Joseph C.
Published: October 2005

The sensitivity and frequency response characteristics of type-L standard laboratory microphones were measured with an electrostatic actuator at surface and at 12 different levels to 31 atm absolute (ATA) in a hyperbaric chamber. The microphones were measured in compressed air and a helium-air environment, with and without the capillary pin. In addition, one microphone remained at a depth of 31 ATA for 24 h to measure its stability under pressure. Results indicated a loss in sensitivity in compressed air and helium-air as a function of pressure. In a compressed-air environment a resonant peak occurred at 4000 Hz, which shifted to 8000 Hz in the helium-air environment. The microphones showed extremely close agreement between compression and decompression, between different pressurizations, and between different microphones. Also, there was no change in sensitivity over a 24-h period of pressurization at 31 ATA. Calibration data at several pressures are given.
Intensity Distribution of Light upon Reflection from Surface Waves
Authors: Hallermeier Robert J. , Mayer Walter G.
Published: October 2005

The actual phase modulation introduced in a light beam by reflection off a surface corrugated in an arbitrary manner is calculated. The forms of the light intensity distribution in the reflection of a uniform- or Gaussian-intensity monochromatic circular light beam from a sinusoidal cylindrically corrugated surface are given.
Vibrational Relaxation Times of Methane and Oxygen at Increased Pressure
Authors: Parker J. G. , Ritke D. N.
Published: October 2005

A study of the effect of microphone design on sound absorption and velocity measurements has been carried out for pressures ranging from 1 to 18 atm. Results of this research show clearly that losses may be introduced by the microphone itself and that this problem becomes more severe with increasing pressure. A microphone has been developed which completely eliminates such effects at lower pressures and greatly reduces them at higher pressures. Measurements in CH4 gave a pressure dependence of the effective specific-heat ratio in good agreement with theory. Extrapolation to zero pressure gave a result in good agreement with that obtained by using the vibrational specific heat calculated from the Planck-Einstein formula. Relaxation times τv were determined as a function of pressure p0 and lead to the averaged value p0τv = 1.565±0.013 (μsec⋅atm). This is in good agreement with recent results using the spectrophone method (1.60 μsec⋅atm) and in significant disagreement with results obtained from fluorescence experiments (1.90 μsec⋅atm). Data obtained for O2 gave relaxation times τv = 3.34(−2) sec⋅atm at room temperature and τv = 2.36(−2) sec⋅atm at a temperature of approximately 50°C. The room-temperature value is higher than previously published data by a factor of 2 and is in reasonably good agreement with extrapolation of high-temperature shock-tube data. The value obtained at 50°C is in still better agreement with this extrapolation.
Effect of Particle Viscosity on Propagation of Sound in Suspensions and Emulsions
Authors: Ahuja Avtar S.
Published: October 2005

The effect of particle viscosity, when it is at least one order of magnitude greater than that of the suspending medium, has been included in the formula, existing in the literature, for the velocity of sound in suspensions or emulsions. The corresponding coefficient of viscous absorption and cross section for scattering of sound energy have also been calculated. The hydrodynamic dispersion of the velocity of sound, due to the frequency-dependent nature of the viscous interaction between the particles and the suspending medium, has been shown to exist in suspensions or emulsions.
Noise Reduction by Vegetation and Ground
Authors: Aylor Donald
Published: October 2005

Transmission of random noise through dense corn, a dense hemlock plantation, an open pine stand, dense hardwood brush, and over cultivated soil was measured. The relation between attenuation and frequency in these diverse cases suggested models that permit the prediction of attenuation in any configuration of vegetation and soil. The corn crop had an excess attenuation of 6 dB/100 ft for each doubling of frequency between 500 and 4000 Hz. On the other hand, the stems of the hemlock, pine, and brush all reduced noise by only about 5 dB/100 ft at 4000 Hz. Bare ground attenuates frequencies of 200–1000 Hz, and the frequency of maximum attenuation depends on the soil permeability to air. Thus, tilling the soil reduced the frequency of peak attenuation from 700 to 350 Hz and increased maximum attenuation at 52 m from the source by nearly 80%. Furthermore, earlier conflicting reports of noise attenuation by vegetation appear reconciled if ground attenuation is taken into account. Scattering and ground attenuation are the principal factors in sound attenuation by vegetation. Both factors attenuate relatively less sound as distance from the sound source increases. Hence measurements far from the source can underestimate the effect of a narrow band of vegetation or soil.
Reflection and Transmission of Acoustical Waves from a Layer with Space-Dependent Velocity
Authors: Steinmetz George G. , Singh Jag J.
Published: October 2005

The refraction of acoustical waves by a moving medium layer is theoretically treated and the reflection and transmission coefficients are determined. The moving-medium-layer velocity is uniform but with a space dependence in one direction. A partitioning of the moving medium layer into constant-velocity sublayers is introduced and numerical results for a three-sublayer approximation of Poiseuille flow are presented. The degenerate case of a single constant-velocity layer is also treated theoretically and numerically. The numerical results show the reflection and transmission coefficients as functions of the peak moving-medium-layer normalized velocity for several angles of incidence.
Plane Stress Waves in Membranes Caused by an Arbitrary Pressure Wave
Authors: Nigul Uno
Published: October 2005

Using the example of the plane motion of a membrane, an analytical method is developed for finding the approximate solution of the second-order wave equation whose right-hand side describes a pressure wave moving with decreasing velocity. It is assumed that the variation of the velocity includes the characteristic speed of wave propagation in the membrane. The method is elaborated for obtaining a solution which is valid in the early-time region. It exploits the Laplace integral transform technique with appropriate approximate methods of inversion. The latter are improved here in comparison with those which have been previously developed in the analyses of similar problems, and can be easily generalized to approximate analyses of the early-time stage of elastic waves which are caused in thin shells by a pressure wave.
An Extension of the Bessel-Fubini Series for a Multiple-Frequency CW Acoustic Source of Finite Amplitude
Authors: Fenlon Francis Hugh
Published: October 2005

A fundamental operational solution of the lossless Burgers' equation is used to derive the spectrum of a two-frequency CW source of finite amplitude as a function of range. The resulting expression is then generalized to the case of a multiple N-frequency CW source of finite amplitude. The region of validity of these solutions is determined by specifying the critical ranges at which the wavefronts become discontinuous. Finally, a modification of these omnidirectional solutions which makes them applicable to directive sources is briefly discussed.
Performance Degradation of Deep-Ocean Transducers Using Onionskin Paper for Acoustic Decoupling
Authors: Haan D. E. , Higgs R. W. , Eriksson L. J.
Published: October 2005

The acoustic decoupling behavior of onionskin paper is examined, with emphasis on sonar transducer applications. Nonlinear changes in the sound velocity of onionskin paper with pressure are used to predict the degradation of both frequency and directional response. These results are obtained by computer analysis of a longitudinal-vibrator equivalent circuit. The results are in reasonable agreement with the measured characteristics of a specific transducer configuration.
Circumferential Waves in a Thin-Walled Air-Filled Cylinder in a Water Medium
Authors: Horton C. W. , Mechler M. V.
Published: October 2005

A line source and a line receiver are used to measure values of group and phase velocity for circumferential waves around a thin-walled air-filled aluminum cylinder when the cylinder is immersed in water. These are believed to be the first experimental measurements of phase velocity of circumferential waves around a thin-walled cylinder. Also, experimental values of attenuation are measured for pulses. These experiments are carried out for frequencies from 50 to 200 kHz, corresponding to a value of ka from 15 to 60. A theoretical analysis based on the equivalent mechanical impedance of a thin-walled elastic shell is developed and numerical values are computed for comparison with the experimental data. The phase velocity measurements agree with computed values in their dependence on frequency, but the values are systematically too large by 2%. However, the experimental values measured for pulses do not show good agreement with theory.
Design of Optimum Directional Arrays Using Linear Programming Techniques
Authors: McMahon G. W. , Hubley Barbara , Mohammed A.
Published: October 2005

The techniques of linear programming have been applied to the synthesis of optimum directional patterns from arrays of point elements. The simplex method has been used to generate optimum element excitations for a given array when the desired directional characteristics are specified. Various criteria are included in the definition of optimality. Numerical examples are given for arrays of up to 70 elements. The size and geometry of arrays that can be treated by this approach are limited only by computation time and computer storage requirements.
Normal-Mode and Ray Theory Applied to Underwater Acoustic Conditions of Extreme Downward Refraction
Authors: Pedersen Melvin A. , Gordon David F.
Published: October 2005

This theoretical article investigates the acoustic field in the image-interference and shadow-zone regions for a model in which the sound velocity decreases with increasing depth from the surface. Near the surface the shadow-zone boundary is the surface-grazing ray, while in deeper regions this boundary is a caustic. The field near the caustic is investigated by modified ray theory based on Airy functions. A comparison of mode theory results with those of ray theory indicates that there is a −π/2 jump in the ray theory phase when the ray touches a caustic. There is, however, no such jump when the ray becomes horizontal. The normal-mode series is absolutely convergent for ranges greater than 1.732 times the sum of the source and receiver depths. When the shadow zone is bounded by a well-developed caustic, the series converges so slowly as to be impractical except at ranges well into the shadow-zone region.
Measured Discrimination of Boundary-Layer Pressure Fluctuations by Round, Square, and Rectangular Transducers
Authors: Recine Emilio C.
Published: October 2005

Pressure fluctuations obtained in a turbulent air pipe flow facility were measured using 19 flush-mounted transducers that varied in size and shape. The results of these measurements, in the form of spectral density, were then compared with the results obtained using a modified theory on transducer size correction originally proposed by Corcos [J. Acoust. Soc. Amer. 35, 192–199 (1963)]. The modification, by White [J. Acoust. Soc. Amer. 41, 1358–1363 (1967)], consisted of using the measured transducer response kernel. Agreement between the experimental data and theoretical predictions was good. In the midfrequency range, transducers that had their longest dimension parallel to the flow produced the greatest discrimination against pressure fluctuations. At high frequencies, the response becomes a function of size and independent of shape, as predicted.
Preliminary Experimental Investigation of the Simple-Source Theory of Jet Noise
Authors: Scharton Terry D. , Meecham William C.
Published: October 2005

Starting with the simple-source theory of jet noise, an approximate relation between the radiated sound-power spectrum and the jet-pressure spectrum is derived. This relation is compared with 12-oct band sound-power levels and jet-pressure levels measured during ground runup of a small turbojet engine, and the agreement between theoretical and measured values is encouraging.
Exact Solutions for the Response of Some Coupled Multimodal Systems
Authors: Davies Huw G.
Published: October 2005

The response of two continuous systems that are coupled together by N mass, spring, and gyroscopic elements is discussed. It is shown that an exact solution may be obtained by inverting a 2N×2N matrix. The case N = 1 is discussed in detail.
Calculation of Spheroidal Wave Functions
Authors: Van Buren A. L. , Baier R. V. , Hanish S. , King B. J.
Published: October 2005

FORTRAN computer programs have been developed which accurately and rapidly evaluate for a wide range of parameters both prolate and oblate spheroidal radial wave functions of the first and second kind and their first derivatives, and both prolate and oblate spheroidal angle wave functions of the first kind and their first and second derivatives. This letter briefly discusses available documentation on these programs and describes some of the computational procedures necessary for their success. In addition, recently published tables of spheroidal radial wave functions calculated using these programs are described.
A Significant Single Quantity that Typifies a Sonic Bang
Authors: Warren C. H. E.
Published: October 2005

The paper introduces the concept of the characteristic overpressure, defined as 4I/T, where I is the maximum impulse, that is, the maximum value of the running integral of the overpressure with respect to time, and T is the signature interval, that is, the time interval between the onset of the first shock and the onset of the last shock in the signature. The characteristic overpressure is considered to be a significant quantity, particularly in regard to the effect of sonic bangs on structures. This is illustrated by the collapse that is achieved when the results of Crocker and Hudson are presented in a manner employing the characteristic overpressure. Finally, the characteristic overpressure is shown to lead to a particularly simple engineering formula for the dynamic magnification factor as a function of the product of the natural frequency of a structure and the signature interval.