bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement and Evaluation of Outdoor Community Noise
Authors: Botsford J. H.
Published: September 2005

This new group it attempting to translate the recommendations of the other groups concerned with measuring output of noise sources and those concerned with rating human reactions to noise into some practical limits or guidelines to facilitate application of current knowledge to control of outdoor community noise. First, a standard procedure for measuring outdoor community noise that will assure consistent results by independent investigators must be developed. The procedure must evaluate the ambient noise of unidentifiable sources upon which the noise of identifiable sources may be superimposed. Another procedure is needed for measuring the noise output of individual sources that contribute to community noise such as mowers, power boats, snowmobiles, etc., and a general procedure usable for many types of sources will be drafted. As the work of this and other groups progresses, plans call for developing (1) limits for noisy equipment, (2) limits for new products to be met by the innovator, (3) guidelines for land use management and planning, (4) community noise measurement methods and limits, and (5) recommended methods of enforcement.
Measurement and Evaluation of Room Noise
Authors: Goodfriend L. S.
Published: September 2005

Notwithstanding the establishment of certain guides by some of the engineering societies, the specification of a standard method of measurement and methods of establishing design guides for the selection of room noise levels by USASI has not been achieved. There is no question of the need for such standards. However, accurate measurement of sound levels outside of reverberation rooms has proved difficult, and a method that will correctly evaluate a noise source in a non-ideal room has not materialized. Because of the wide range of possible ambient conditions, specification of design guide or recommended or optimum room noise levels for even the simplest situation has proved difficult, and agreement between manufacturers of equipment and its users has not been achieved.
Measurement and Evaluation of Motor Vehicle Noise
Authors: Venema J.
Published: September 2005

This discussion of current activities of the SAE Vehicle Sound Level Committee will not emphasize standards that have already been prepared, but rather seek to explain the philosophy behind the measurement methods that were recommended. The future activities of this committee will also be discussed.
Rating of Noise with Respect to Human Response—A Summary of Status, Problems, and Outlook
Authors: Gales R. S.
Published: September 2005

There are presently nine writing groups sponsored by USASI working on methods for measurement and rating of noise. All of these in some respect relate to the human response to the noise. These writing groups can be divided into three areas: (1) those dealing with basic measures of human response, (2) those dealing with assessment of noise from a particular type of source, and (3) those constrained to assessment of all types of noise in a particular environment. The high degree of interaction and overlap of these various areas generates a requirement for commonality of noise rating methods and measures, yet it is clear that no single method will suffice for all applications as they differ in environmental constraints, need for precision, economic resources, etc. A philosophy of a minimal set of noise rating measures will be presented, including assessment as to factors affecting choice of measure such as need for precision, economics, simplicity, communication with laymen, etc. The concept of sound level A as a common method for all rating procedures will be discussed. Present problems of overlap of jurisdiction and problems of establishment of criteria for quality and acceptability will be explored. Goals for uniformity and compatibility of standards will be outlined.
Identification of Selected Vowel Phonemes by Children
Authors: Gilbert J. H.
Published: September 2005

Recordings were made of utterances of four vowels in a neutral context. The utterances were produced by children of C.A. 4–0 years, divided into groups of normal and late language users. Second formant frequencies for each of four vowels was determined and compared with data of Peterson and Barney. Utterances were presented to S's and adults for identification. Spectrographic analyses indicated a difference between the normal and late language users, although formant frequency values of the former group approximate those of Peterson and Barney. Identification of vowels by listeners showed confusion perception of vowels produced by late language users. Implications of these results will be discussed. [This research was supported in full by the Medical Research Council of Canada.]
Transglottic Air Flow Related to Selected Parameters of the Voice
Authors: McGlone Robert E.
Published: September 2005

This study was concerned with the relationship of air flow to systematic changes of vocal pitch, vocal intensity, and voice register. Nine young adult women with no previous vocal training were selected as subjects. Their respective pitch ranges were determined for the modal and upper registers and these ranges were divided into 10% segments. Vocal intensity ranges at each of these pitch levels were established and also divided into 10% segments. Air-flow measures were obtained from respirometric recordings made as each subject sustained the vowel /a/ for 4 sec at each intensity level for each pitch segment in both registers Results of these measurements showed that a progressive increase in air-flow accompanied increases in vocal intensity in both the modal and upper registers. A progressive increase in air flow also was found as vocal pitch was increased in the modal register. No such relationship was found in rite upper register.
Relation of Intraoral Air Pressure to Oral Cavity Size
Authors: Brown W. S. , McGlone Robert E.
Published: September 2005

The purpose of this study was to investigate whether the size of the oral cavity of a speaker was related to pressures occurring in the mouth during speech. Of the three previous studies that considered size and pressure, two report a positive relationship and one found no relationship. Six young adult males were selected as subjects on the basis of cavity dimensions obtained from measurements of lateral headplates and molar widths. Each repeated CV and VC syllables composed of /t/, /d/ and /n/, and /i/ and /a/. These syllables were produced at two relative intensity levels and at two rates of utterance. Pressure measures obtained during repetition of the speech sample showed no systematic trends associated with cavity size, different vowels, rates of utterance, or syllabic position. Mean pressure differences were found between consonants and relative intensity levels.
Computer-Controlled Display for Second Language Learning
Authors: Klatt Dennis H. , Dodds Douglas
Published: September 2005

In learning the phonology of a foreign language, the features of the new vowel system are often the most difficult to perceive, produce, and recall. A computer-controlled display that may aid in teaching the appropriate articulatory gestures for vowels in arbitrary phonetic environments has been gestures for vowels in arbitrary phonetic environments has been implemented. Display parameters correlated with the position of the tongue body are obtained from a spectral representation of the acoustic waveform. Preliminary results comparing several native Spanish-speaking subjects who are learning English and a group of native English-speaking subjects indicate that many of the acoustic correlates of a foreign accent are discernible in the display. [Work supported by the Advanced Research Projects Agency.]
Transducing Jaw and Lip Movements in Speech
Authors: Ohala John , Hiki Shizuo , Hubler Stanley , Harshman Richard
Published: September 2005

Various schemes for easily and accurately transducing lip and jaw movements into an analog voltage have been explored. Considerations of cost, simplicity, linearity, and the need to maintain natural articulation in speech led to the development and construction of a device involving a simple optical system and a photocell. The device can track in any dimension the position of one or more tiny lights attached to the lips and/or jaw. Using the device a few simple experiments were conducted involving jaw deflection, velocity and acceleration. The experimental finding of Kozhevnikov et al. (Speech: Articulation and Perception, 1965) that the peak velocity of the lower lip on closing for a consonant varies proportionately with its maximum open position was found to be true of the jaw, too. [This research was partially supported by the National Institutes of Health, U. S. Department of Health, Education and Welfare, and the Office of Naval Research.]
Quantitative Evaluation of the Zwanzig Equation
Authors: Evans D. F.
Published: September 2005

The variation of ionic mobilities with size, solvent properties, temperature, and pressure remains one of the unsolved problems of transport theory. The Zwanzig equation, which is based on the continuum model for the solvent, is the ultimate that has been devised at this time. Although the Zwanzig equation successfully predicts many of the qualitative features of this transport property, the extent to which the theory is applicable in a quantitative manner has not been critically reviewed in the literature. This aspect of the Zwanzig equation will be discussed using ionic molibities in water, acetonitrile, nitromethane and the alcohols, methanol through butanol.
Effects of Signal Frequency on Sequential Aspects of Signal Detection Performance
Authors: Sorkin R. D. , Pastore R. E.
Published: September 2005

Three experiments were designed to investigate the manner in which the spectral character of the signal presented on any trial of a detection experiment influences detection efficiency on subsequent trials. Each of the experiments involved a two-interval detection procedure (2AFC) in which the signal was randomly chosen from a previously defined signal ensemble. The signals in the first experiment consisted of a 10-msec and a 100-msec burst of a 1000-Hz sinusoid. In the second experiment, the signal ensemble was composed of three 100-msec signals: a 650-Hz, a 1300-Hz, and a phase-locked combination of the 650- and 1300-Hz sinusoids. The ensemble in the third experiment consisted of two 100-msec signals: a 500-Hz and a 2000-Hz sinusoid. In the third experiment, there were additional constraints on the stochastic signal presentation process such that long runs of consecutive trials with the same signal were highly probable. Trial-by-trial transition probabilities were computed for all possible stimulus and observer outcome (correct-incorrect) combinations. These transition probabilities are discussed in terms of the influence on an observer's behavior of the relevance of the frequency information conveyed on previous trials.
Bandwidth Estimates in Human Signal Detection
Authors: Ahumada Al , Lovell John
Published: September 2005

Earlier attempts to fit a bandpass-filter energy-detector model to signal-detection data indicate that the energy passed by narrow filters best predicted the observers' responses on signal-plus-noise trials, but that wide filters best predicted the performance on noise trials [A. Ahumada, Detection of Tones Masked by Noise, doctoral dissertation; Psychology, UCLA (1967).] We have replicated this finding by presenting computer-generated tones and noises in random sequences to eliminate the possibility that the earlier results were an artifact of the particular stimulus sequence used. A version of the Bell Telephone Laboratory's Music IV Program was used to generate the stimuli: noise bursts synthesized from random amplitude sine and cosine waves. If the stimulus was to contain a signal, a constant was added to the amplitude of the sine member of the 500-Hz component of the noise. The observer made rating responses that were correlated with the energy in rectangular frequency bands of varying width centered at 500 Hz.
Lateralization and Detection of a Tonal Signal in Noise
Authors: McFadden Dennis
Published: September 2005

The ability to lateralize a tonal signal against a white-noise background was investigated by presenting that signal at different intensities to the two ears. The signal (500 cps, 250 msec) was gated on every trial during the single observation interval. The more intense signal was equally likely to be presented to the left ear as to the right, and the subject's task was to indicate on each trial which ear received the more intense signal. Both the interaural phase relation of the signal and the magnitude of the interaural intensive difference were varied from session to session. For signals both in-phase (S0) and 180° out-of-phase (Sπ), six-point psychometric functions were determined with interaural intensive differences of 3, 6, and 12 dB. In addition, detection functions were obtained for each of these interaural conditions using the single-interval, or YES-NO, technique. Particularly for the smaller interaural intensive differences, S0 and Sπ signals led to lateralization functions of quite different forms. Masker: N0 continuous, 44 dB SPL/cycle.
Auditory Detection of Short-Duration Narrow-Band-Noise Signals
Authors: Whitmore John
Published: September 2005

At the 75th Meeting of the Society, Whitmore, Williams, and Ermey [J. Acoust. Soc. Amer. 44, 370(A) (1968)] presented a paper on the detection of a narrow-band-noise signal. For a duration the reciprocal of the signal's bandwidth, they showed that the shape of the human psychometric function is predicted accurately by a theoretical function derived from overlapping Rayleigh densities. This report extends their work to durations one-half, and twice the reciprocal of the bandwidth. Psychometric functions were obtained on three observers for 8.9-, 17.8-, and 35.6-msec signals. The signal and the masker were gated synchronously, and both were diotic. The psychometric function based on Rayleigh densities adequately described the shape of the human functions for all three durations, even though there was a fourfold change in signal energy. [Work supported by the National Institute of Mental Health and the National Aeronautics and Space Administration.]
Engineering Aspects of Material Damping and Structural Damping Measurements
Authors: Chang C. S.
Published: September 2005

Without a completely inclusive governing theory of damping, engineers are forced to substitute empirical models for the description of the true physical properties. A necessary criteria is that the damping model be independent of the process of deformation. It is usual to include damping in the equations of motion by selecting modal equations that give restricted agreement with some specific measured ensemble of data. The validity to extend empirically derived equations beyond the data ensemble must be demonstrated experimentally. The challenges to practicing engineers are clearly the following: (a) to develop the optimum experiments to determine the effects of damping on the dynamic responses of a structure, and (b) conversely, to make optimum usage of results of an incomplete set of experimental data for a given application. Some recent investigations on damping and dynamics responses of relatively complex structures and their models are described in this paper in an attempt to stimulate research and developmental efforts to meet the above challenges.
Combination Effects of Tone and Duration Parameters on Perceived Noisiness
Authors: Pearsons Karl S.
Published: September 2005

Subjective judgment tests were conducted to determine the effects of variation in the tone content and stimulus duration upon the relative acceptability of sound stimuli consisting of shaped broad-band noise with and without a 2000- or 4000-Hz tone. Tone-to-noise ratios measured 25, 10, and 5 dB in 13-oct bands. All stimuli were of triangular time patterns and included durations of 4, 12, and 32 sec. Tests were also conducted to investigate the effect of varying the time at which the level of the tone reached its maximum value relative to the time at which the level of the broadband noise reached its maximum value. Various measures were employed in the analysis of the judgment results; these included the over-all sound-pressure level (SPL), A-weighted SPL, N-weighted SPL, and perceived noise level with and without tone and duration corrections. The results of the tests indicate that the perceived noise level with tone and duration corrections provides better agreement with subjective judgments of acceptability than do the other measures that were investigated. [This work was supported by the National Aeronautics and Space Administration.]
On Estimating Noisiness of Aircraft Sounds
Authors: Young Robert W. , Peterson Arnold
Published: September 2005

Published results of judgment tests that have been cited [K. D. Kryter, J. Acoust. Soc. Amer. 43, 344–361 (1968)] in support of calculated perceived noise level as the most accurate predictor of the “noisiness” of aircraft noise have been reanalyzed with small corrections known to be appropriate for the measuring instruments used. Application of standard statistical procedures indicates that the minor differences among A-weighted sound level, calculated loudness level, calculated perceived noise level, and D- (formerly N-) weighted level, in their correlation with judged noisiness, are not statistically significant. Only the B and C levels are clearly inferior as predictors of noisiness.
Method of Computing Elements of Diaphragm-Type Transducers
Authors: Carlisle Richard W.
Published: September 2005

The acoustical elements of transducers, such as apertures and air chambers, are computed in acoustical units. The acoustical impedance of each element may be written by inspection. These impedance values may be converted into “specific acoustical impedance” by multiplying by the first power of the diaphragm area. It will be shown that these values are mathematically compatible with the mechanical impedance of the diaphragm and mechanical compliance per unit of diaphragm area. It has been found that transducers having a given frequency response yield similar specific impedance values even though radically different in size and construction. Examples will be given. The use of cgs and mks units will be compared. Advantages of the above method will be demonstrated.
Phonon-Phonon Interaction
Authors: Krasilnikov V. A.
Published: September 2005

Upon increase in frequency of ultrasonic waves in solids—i.e., for an increase in energy of coherent phonons and increase in ultrasonic intensity—the interaction of phonons and phonons, electrons, photons, and magnons becomes more and more important. Interactions between coherent phonons are discussed. This type of interaction is a purely acoustical aspect of the problem—nonlinear interactions between elastic waves or the nonlinear acoustics of a solid in the narrow sense. The selective rules, which define the possible conditions for three-phonon interactions consist of the conservation of energy and quasimomentum of the interacting phonons. These conditions follow both from the nonlinear equations of elasticity theory and from quantum-mechanical consideration with account of the anharmonicity of the lattice. Experimental work in the investigation of three-phonon interactions—the generation of harmonics of a longitudinal wave, the formation of the second harmonic of a transverse wave due to the presence of dislocations, the scattering of sound by sound in the intersection of waves of different polarizations. Experiments on the nonlinear interaction of elastic waves allow us to find certain third-order elastic moduli. Interactions of thermal phonons with coherent phonons, which lead to ultrasonic absorption in solids are considered. These are connected both with the disruption of the equilibrium distribution of thermal phonons, and also with the direct interaction of ultrasonic and thermal phonons.
Transient Effects in the Propagation of a Sound Pulse in a Viscous Liquid
Authors: Moffett Mark B. , Beyer Robert T.
Published: September 2005

The propagation of an rf (f≈7.5-MHz) acoustic pulse in a viscous liquid, CCl4, has been experimentally investigated. As the path length increased, the pulse developed a precursor. Furthermore, the first peaks of the pulse were attenuated nonexponentially, persisting over much larger distances than later peaks in the pulse. These effects were noticeable for propagation distances x≳1/α, where α is the amplitude absorption coefficient. Theoretical results of Blackstock [J. Acoust. Soc. Amer. 41, 1312–1319 (1967)] for a step-modulated sinusoidal pulse were modified to take into account the actual shape of the experimental pulse at x=0. Comparison of the expected and measured pulse shapes gave good agreement for the peak positions, but only qualitative agreement for the peak heights. This discrepancy is probably due mainly to departure of the waves from the planarity assumed in the theory. [Supported in part by Office of Naval Research.]
Rayleigh Wave Dispersion in Layered Media
Authors: Lawrie W. E.
Published: September 2005

A theoretical analysis has been carried out to determine the Rayleigh wave velocity in an elastic material in which residual stresses exist, varying rapidly with depth. The analysis is based on a layered model in which each layer represents a corresponding stratum of the stressed material. A computer program has been developed to compute the Rayleigh wave-velocity dispersion for the layered models. The Rayleigh wave velocity was found to be dependent upon a weighted average of the stress in a layer of approximately one-wavelength thickness. In a model consisting of two layers overlying an infinite half-space, each 0.0076 cm thick and stressed to 50 ksi and 25 ksi, respectively, the Rayleigh wave velocity asymptotically approaches 2.9916 (105) cm/sec at low frequencies and is 2.9752 (105) cm/sec at frequencies above 45 MHz. When the stress in the 25-ksi layer is changed from tensile to compressive, a significant change occurred in the velocity dispersion curve between 5 and 40 MHz. The analysis has been used to optimize the ultrasonic parameters involved in determining residual stress. [Supported by Air Force Materials Laboratory, U. S. Air Force.]
Temperature Dependence of Ultrasonic Harmonic Generation in Copper Single Crystals
Authors: Peters R. D. , Breazeale M. A.
Published: September 2005

Pulsed finite-amplitude ultrasonic waves have been used to determine the temperature dependence of the nonlinearity parameters of copper single crystals. (Nonlinearity parameters are combinations of third-order elastic constants). By maintaining a constant detector gap of 5 μ with a pneumatically controlled variable-gap capacitive detector, it was possible to measure fundamental and second harmonic amplitudes of the ultrasonic wave between 77° and 300°K. From these amplitudes, calculations were made of the nonlinearity parameters relative to their room-temperature values, which could then be determined by absolute calibration. Typically, the nonlinearity parameters change linearly with temperature by about 10%. Over this temperature range, the measured values of the nonlinearity parameters are consistent with the assumption that the primary contributor to the third-order elastic constants is the closed-shell repulsive interaction of nearest-neighbor atoms. [Research sponsored by the U. S. Atomic Energy Commission under contract with the Union Carbide Corporation.]
Low-Temperature Ultrasonic-Attenuation Measurements in Cs
Authors: Murphy John A. , Trivisonno J.
Published: September 2005

Measurements of the magnetic-field dependence of the ultrasonic attenuation of longitudinal waves in cesium single crystals have been made between 4.2° and 1.3°K. Ultrasonic frequencies between 10 and 70 Mc/sec were employed. Single crystals oriented along the [100] and [110] were used, and the magnetic field was always perpendicular to the direction of propagation. At 1.3°K, the attenuation is oscillatory and periodic in 1/H. These periods, which are related to the extremal dimension of the Fermi surface, were used to measure the anistropy in the Fermi surface of Cs in the (100) and (110) planes. These measurements will be compared with the band structure calculations of Ham and the de Haas-Van Alphen measurements of Okumura and Templeton. The attenuation measurements will also be compared with the free-electron theory of the ultrasonic attenuation due to conduction electrons. [Supported by U. S. Air Force Office of Scientific Research.]
Pressure Derivatives of the Elastic Constants of Lead
Authors: Schuele D. E. , Miller R. A.
Published: September 2005

The pressure derivatives of the adiabatic elastic constants of lead have been measured at 296° and 195°K using an ultrasonic pulse-echo technique. The values found for dC′11, dC′, aind dC′44, are 7.69, 0.301, and 2.06 at 396°K and 7.51, 0.280, and 1.97 at 195°K, where the notation C′11=(C11+C12+2C44)/2 and C′=(C11—C12)/2 has been used. The low-temperature limiting value of the Grüneisen parameter has been calculated and is compared with the value obtained from thermodynamic data.
Some Physical Properties of Single Crystals of Normal and Deuterated Cesium Dihydrogen Arsenate
Authors: Adhav R. S.
Published: September 2005

The elastic, dielectric, and piezoelectric constants of single crystals of cesium dihydrogen arsenate grown in H2O and of cesium dideuterium arsenate grown in D2O have been measured in the temperature range of 20°–80°C. The shear elastic constants S44 and S66 increase, while the extensional elastic constants S11 and S33 decrease on deuteration. Considerable changes in the temperature coefficients of three constants S11, S33, and S66 are produced by deuteration. Zero temperature coefficients of frequency of extensional and shear resonator plates are obtained in the Z plane, which are useful in electromechanical applications.
Ultrasonic Measurements beyond 3000°K
Authors: McDonough M. S. , Lynnworth L. C. , Carnevale E. H.
Published: September 2005

Ultrasonic attenuation has been measured in tungsten and rhenium as a function of video pulse width and temperature. Measurements were performed up to 3000°K using pulsewidths from 6 to 40 μsec. Attenuation decreased as pulsewidth increased, but increased as temperature increased. A particularly sharp increase was observed as temperature increased beyond the recrystallization temperature. Mechanisms possibly responsible for this behavior are discussed. From velocity measurements, Young's modulus in rhenium and tungsten was determined to about 3500°K. The change in modulus of rhenium due to the diffusion of carbon at a fixed temperature over a period of several hours has been examined. These experimental results were obtained by ultrasonically interrogating electrically self-heated wire specimens. This method has been used with metallic specimens ranging in length from ∼20 mm to ∼6 mm long, at temperatures up to the melting point.
Influence of Ultrasonic Vibration on Metallic Friction
Authors: Lehfeldt Eckart
Published: September 2005

The influence of vibrations on the internal friction of metals has been investigated by tensile and bending tests with superimposed ultrasonic vibrations at 20 kHz. In contrast with previously published work, these experiments have shown that the internal friction is not influenced because the yield strength of the sample is reduced by an amount which just equals the induced acoustic stress amplitude. Therefore, the effect comes from the super position of stresses. On the other hand, the boundary friction can be reduced by ultrasonic vibrations. This effect depends on the vibration direction in relation to the moving direction as well as on the vibration speed in relation to the moving speed. If the moving speed equals or surpasses the vibration speed, no reduction of boundary friction can be obtained. As an example of technical application wire drawing experiments with superimposed ultrasonic vibrations have been carried out. In most cases, the drawing force is reduced approximately by the amount of the acoustic stress amplitude if the drawing speed is low and if a certain resonance condition is checked.
Frequency Discrimination in Noise
Authors: Jesteadt Walter H.
Published: September 2005

Frequency DL's at 1000 Hz were obtained in quiet and at three noise levels—60, 80, and 100 dB SPL. Sensation levels of 4, 6, and 10 dB SL were used at each noise level. The DL's were obtained by means of a tracking task in which the subject controlled the input voltage to a frequency modulator. Characteristic improvement is seen when frequency DL's are plotted as a function of sensation level. The curve for the DL's for 60-dB SPL noise runs parallel to the curve for quiet, with the noise DL's slightly greater. The curves for the DL's for the 80- and 100-dB SPL noises are less steep, and the average DL's are greater than the DL's for quiet by ratios of 1.5:1 and 2:1, respectively. [This research was supported by research grants from the National Institute of Neurological Diseases and Blindness, U. S. Public Health Service.]
Separating the Effects of the Acoustic Reflex from Remote Masking
Authors: Gunn Walter J.
Published: September 2005

Two experiments were performed in order to separate the effects of the acoustic reflex from remote masking. In the first experiment, subjects adjusted the level of a 400-Hz maskee in the homolateral ear in order to keep the perceived sound source centered when presented binaurally simultaneously with the 3000-Hz monaural masker for various durations, some of which were shorter than the latency of the acoustic reflex. The results of the first experiment show remote masking at durations of 50, 200, and 500 msec, with significantly more masking at 500 msec than at 50 msec. In the second experiment, some procedural refinements were made and durations as short as 20 msec were used. Results again showed remote masking taking place at durations much shorter than the latency of the acoustic reflex and significantly more remote masking at 500 msec than at 20 msec. The results of both experiments seem to support notions of the involvement of distortion products in remote masking at short durations and the additional involvement of the acoustic reflex at longer durations.
MLD' with Narrow-Band Noise Maskers
Authors: Wightman Frederic L.
Published: September 2005

The detectability of 1110 sec S0 and Sπ signals, masked by continuous Gaussian noise, was measured as a function of the bandwidth of the noise. Electronic filters with near-rectangular passbands were used to provide noise bandwidths of 3, 10, and 50 Hz, centered at the signal frequency, 250 Hz. Previous experiments have shown that the MLD, the difference in detectability of S0 and Sπ signals, grows as noise bandwidth is reduced, reaching a maximum of about 25 dB when the bandwidth is under 10 Hz. In the present study, however, the maximum MLD (22 dB) was obtained when the noise bandwidth was 50 Hz. The discrepancy between these two results was studied by considering the effects of slight changes in the shape of the noise power spectrum. Such small changes in the shape of the noise spectrum were found to have marked effects on detectability of S0 signals, and thus on the MLD. For example, when a 200-Hz band of noise at 30-dB spectrum level was added to a 3-Hz band at 50-dB spectrum level, the S0 threshold was elevated at 8 dB. The Sπ threshold was unaffected by the added low-level noise. [Research supported by the National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare.]
Frequency-Modulation Masking
Authors: Hopkinson Norma
Published: September 2005

Remote masking has been attributed to a mechanical nonlinearity in the cochlea that results in the detection of the random envelope of a band of noise. If this speculation is correct, remote masking should not appear when the masker is a band that results from frequency modulation. The tone would have characteristics of a band of noise, but its envelope is rectangular. Masking of a 245-Hz tone was determined for a 1200-Hz pure-tone masker and for a 1200-Hz masker, frequency modulated at a rate of 25 Hz through a range of ±100 Hz. Results for the pure-tone masker showed 5 dB of masking at 110 dB SPL. However, for the frequency-modulated masker 20 dB of masking occurred at 110 dB SPL. This masking begins around 90 dB and increases linearly with level at a slope of +1.00. Measurement of noise level in the 250-Hz octave indicated that this effect is not due to noise in the earphone. Neither is it remote masking, since the slope of the masking function is not +2.00. [Supported by grants from the National Institute for Neurological Diseases and Blindness.]
Effect of Signal Duration on Pure-Tone Masking
Authors: Ehmer Richard H. , Ehmer Barbara J.
Published: September 2005

A Békésy audiogram was obtained for a signal of 5- or 20-msec duration recurring once per second. This audiogram was repeated with the signal presented during a 100-msec masking tone. The signal began 10, 22, 50, 75, or 87.5 msec after the start of the masker. Maskers used were 250–8000 Hz at 20–90 dB SL's. Although the unmasked threshold for the 20-msec signal is lower than that for the 5-msec signal, this is not found for masked thresholds. The amount of masking is not uniformly related to the duration of the signal. It often appears that there is more masking of the 20-msec tone by low frequencies, but there may be more masking of the 5-msec tone by high frequencies. These results differ somewhat from the findings of others relating tone duration to masking thresholds of white noise. A reconcilation of these different findings is attempted. [Work supported by the National Institute of Neurological Diseases and Blindness.]
Diffuseness in Reverberation Rooms
Authors: Schultz Theodore J.
Published: September 2005

This paper discusses the relations between pressure squared, energy density, and power flow in a practical reverberation room, as contrasted with an ideal diffuse sound field, and also how to characterize the state of diffusion in a real room. It will consider the reaction of the room upon the power output of a nonideal source (i.e., neither “point source” nor “constant volume velocity”) and will present data to illustrate some of these effects.
Point-to-Point Correlation of Sound Pressures in Reverberation Chambers
Authors: Morrow Charles T.
Published: September 2005

Point-to-point correlations of reverberant sound fields are important both for high-intensity noise tests of spacecraft and for exploring the state of diffusion of the sound field. The classic paper on reverberant field correlation by Cook and others [J. Acoust Soc. Amer. 27, 1072 (1955)] derived a narrow-band correlation coefficient of (sin kr)/kr, where r is the separation of any two points considered, on the assumption that the field is completely diffuse. The primary intent of the present paper is to consider the actual reverberant mode shapes of a rectangular room and, without any assumptions concerning diffusion, show that the correlation can approach Cook's formula. The treatment sheds some light on conditions that alter the correlation. For example, extreme symmetry in the chamber, noise source, and measurement points can increase the point-to-point correlation. The derivation can be a point of departure for computer programs to study the correlation in particular situations. These should be quite valuable, as it is easier to change dimensional ratios, for example, in a computer program than in an experimental setup. The presentation will concentrate on the applications, the basic concepts and the approach. Detailed derivations will be deferred until publication.
Instrumentation for Space-Averaging Sound Pressure Levels
Authors: Wootten John
Published: September 2005

The measurement of machinery noise, sound-transmission loss, and reverberation decay inside reverberant enclosures requires multiple measurements obtained from several positions in the test enclosure. These measurements are used to establish a space average sound pressure. The paper describes a multichannel microphone system that sequentially samples six microphones to provide a single microphone signal. This composite signal is then analyzed. No further space-averaging computation is required. The averaging time of the recorder is discussed with reference to swinging microphone arrangements and microphone multiplexing systems.
Response of Linear, Distributed Systems to Random Fields: Applications of the Fast Fourier Transform
Authors: White Pritchard H. , Otnes Robert K.
Published: September 2005

The calculation of the response of a distributed system to a homogeneous, random field involves the calculation of an integral of the form ∫∫S(ξ,ω)φ(x)φ(x′)dxdx′, where S(ξ,ω) is the cross spectrum of the random field and φ(x) is the system response function (mode shape or transducer response kernel). Transformation to the spectral domain (k—ω) space, simplifies the integration and gives considerable savings in computational time. The fast Fourier transform can be readily applied to the problem, reducing the required time by more than an order of magnitude. Examples of joint acceptance and transducer resolution in a turbulent boundary-layer pressure field are presented.
Farfield Prediction from Nearfield Crosspower Measurements
Authors: Butler John L.
Published: September 2005

A series expansion method for predicting the farfield from nearfield crosspower measurements is given. The method for the special case of coherent sound fields was presented previously [J. Acoust. Soc. Amer. 44, 35(A) (1968)]. The series method is based on an expansion in spherical wavefunctions truncated to include only the number of terms equal to the number of nearfield measuring points. A distinct advantage of the method is that the nearfield measuring points need not be restricted to the usual separable surfaces. An evaluation is presented through a set of numerical examples where the predicted farfield is compared with the exact farfield from a theoretical source of partially coherent sound. It is shown that good results can be obtained for partially coherent as well as coherent sound fields. [Work sponsored by the Office of Naval Research (Acoustics Programs Branch).]
Digital Camera for Acoustic Applications
Authors: Lopes L. A. , Thomas O. F.
Published: September 2005

We present a method for constructing a camera by using a digital computer to process the output of an array of hydrophones. The theoretical foundations of the system are presented, being nothing more than a new way of using established acoustic theory. The 1108 computer at NUWC has been programmed to simulate an acoustic field, and the digital camera has been used to form images of the simulated acoustic objects. The details of the program, and the pictures formed by the digital camera, are presented. Some of the details of a proposed first model of the camera are presented and the need for acoustic research is explored.
Flow-Induced Vibration of a Single Circular Cylinder by the Wake at the Transition Reynolds Number Range
Authors: Chen Y. N.
Published: September 2005

The results of the several investigations on the structure of the wake induced by the flow behind a circular cylinder in the transition Reynolds number range of about 2×105 to 3.5×106 contradict each other. Some authors detect a peak frequency of the dynamic force of the wake indicating the existence of the Karman vortices, while others find only a turbulence spectrum in it. The reason for this dispute seems to be due to the different width of the wake occuring in the different measurements, By introducing turbulence into the flow the formation of the vortex can be suppressed, whereas an increased surface roughness will force the vortex to form. As the flow turblence narrows the wake while the surface roughness widens it, a different combination of both will lead to a completely different result-occurrence or disappearance of the vortex. The phenomenon that the formation of the stationary shock waves on the cylinder surface will induce the vortex shedding under any circumstances supports this theory.
Generation of Subharmonics of Order One-Half: A Continuation
Authors: Solomon L. P. , Evans L. L.
Published: September 2005

Eller and Flynn, at the last Acoustical Society Meeting in Ottawa (M6), pointed out that under certain conditions bubbles driven by a sound field will pulsate with a frequency equal to one-half the frequency of the sound field. This was calculated by relating the bubble equation to the Mathieu equation which exhibits these subharmonic properties. We present here confirmatory evidence obtained with the hybrid analog computer. Solutions are presented both in the case of viscous and inviscid fluids. Analog results are compared to the Rayleigh collapse problem in order to demonstrate the accuracy and ease of operation of the hybrid facility. [Work partially supported by NSF grant GK-730 and ARO contract.]
Discontinuities in Cavitation Characteristics of Supersaturated Air-Water Solutions
Authors: Lierke Ernest G.
Published: September 2005

Discontinuities in the cavitation characteristics of supersaturated air-water solutions at 0.8 MHz are discussed by comparison between narrow-bandwidth sound-pressure measurements at characteristic frequencies of the cavitation spectrum and the degassing velocity at hydrostatic pressures between 60 and 500 Torr and power densities up to 12 W/cm2.
Ultrasonic Detection of Cavitation at Catheter Tips
Authors: Kremkau F. W. , Gramiak R. , Carstensen E. L. , Shah P. M. , Kramer D. H.
Published: September 2005

To assist in the identification of inner heart structures during ultrasonic cardiac diagnosis, various liquids have been injected through catheters into heart chambers. Each injection produces a cloud of ultrasonic echoes within the blood-filled catheterized chamber. An experimental procedure involving injection of fluids into a test chamber under controlled hydrostatic pressure has shown that cavitation is the primary source of these echoes. Acoustic impedance difference between the injected fluid and the blood can contribute to echo production but is insignificant for commonly used fluids injected under normal conditions. Turbulence resulting from the injection produced no detectable echoes. [This work was supported in part by a grant from the National Institutes of Health.]
Reflection of Ultrasonic Waves: Phase Shift, Lateral Beam Displacement, and Surface Waves
Authors: van Buren A. L.
Published: September 2005

The lateral beam displacement when a finite-width ultrasonic beam is reflected from a plane liquid-solid interface is related to the phase shift upon reflection. In particular, the nongrazing angle of incidence for which the phase shift is 180° is almost equal to that angle of incidence for which the lateral beam displacement is a maximum. It is shown that this same angle also accurately represents that angle at which energy is radiated into the liquid when a surface wave propagates along the interface. Use of these relationships then allows a determination of the velocity of the longitudinal or shear wave in the solid or the longitudinal wave in the liquid when the other two velocities are known and a determination of the velocity of the surface wave from measurements of either the phase shift or the lateral beam displacement upon reflection. [Research done at the University of Tennessee and sponsored by the Office of Naval Research.]
Audiometric Effects of Discrete Laser Irradiation of the Squirrel Monkey Inner Ear
Authors: Wilpizeski C. , Sataloff J. , Innis R. , Shiner W.
Published: September 2005

Four young adult squirrel monkeys were trained in restraining chairs to track their auditory detection thresholds by means of a single-lever shock-avoidance procedure. Pure tones from 250 Hz through 12 kHz were presented free field, and measurements were obtained before and for at least 15 weeks following laser irradiation. Control audiograms were taken after each animal was surgically operated by reflecting the tympanic membranes and fenestrating both cochleas with a small burr. About one month later, each animal was reoperated and irradiated bilaterally through the burr holes with a neodymium laser. One, two, four, or eight light pulses were delivered into the inner ear through a flexible fiber optic. Subsequent to obtaining the 10-week postirradiation audiograms, the monkeys were trained on earphones, and each ear was assessed independently. [Work supported in part by National Institute of Neurological Diseases and Blindness.]
Experimental Evaluation of Moving Sound Diffusers for Reverberation Rooms
Authors: Ebbing Charles
Published: September 2005

The acoustic power flowing from a monopole source is proportional to the radiation resistance presented to the source. This value is determined by the modal structure and the acoustic impedance of the walls of the chamber. The rotating sound diffuser modulates the modal structure and with it, the radiation resistance. Comparison of the time average of the radiation resistance as the monopole source location is changed with and without the diffuser rotating indicates the effectiveness of a given diffuser design in removing the dependence of acoustic power output on the source position. The rotating sound diffuser evaluated was a symmetrical biconical surface of revolution rotating at speeds up to 30 rpm. Fifty percent of the surface area of the diffuser was covered with ribbed fiberglass, the remainder was left uncovered. In order to measure the radiation resistance an acoustic impedance head was fabricated from a modified loud speaker. Displacement of the diaphragm was sensed using a noncontacting fiber-optic sensor. The resulting pressure generated in front of the diaphragm was measured by a condenser microphone. Instrumentation normally used for the measurement of complex mechanical impedance was adapted to record the real part of the radiation impedance.
Sound-Power Measurements in a Reverberant Room
Authors: Schultz Theodore J.
Published: September 2005

This paper gives some field experiences with the ASHRAE test procedure to qualify reverberation rooms for the measurement of pure-tone sound-power output. The effects of room shape, room volume, room absorption, diffusing elements, rotating vanes, microphone traverse, etc., are compared, and the use of a “reference sound source” to calibrate a room is discussed.
Theoretical Predictions of Farfield Acoustic Waveforms Generated by Large Atmospheric Explosions
Authors: Pierce Allan D. , Posey Joe W.
Published: September 2005

A formulation of a feasible method of predicting acoustic-gravity waveforms from atmospheric nuclear explosions is given The atmosphere is represented as being composed of an arbitrary number of layers, each of constant sound speed and wind velocity. The explosion is represented as a point energy source with time dependence determined from published data and hydrodynamic scaling laws. The farfield waveform is approximated as a sum over guided propagating modes. A brief discussion is given of a computer program based on the method and of some of the numercial analysis problems that were encountered and resolved. A number of computed waveforms are exhibited, which confirm previous conjectures concerning the effects of the stratospheric winds on the propagation. The relative times of arrival of characteristic waveform features as seen in different azimuth directions is generally determined by the wind velocity component along the propagation direction at the altitude where the mode carrying a given characteristic feature is primarily ducted.