bluuebunny/crossref_metadata_2025 huggingface dataset:
Laboratory Measurement of Sound Absorption
Authors: Huntley Ralph
Published: October 2005

A discussion of the assumptions underlying measurements of absorption. The inadequacy of the Eyring equation. The necessity for moving vanes. The effect of signal bandwidth. The acoustical meaning of the mean-free path.
Acoustical Modelling—Progress Report
Authors: Veneklasen Paul S.
Published: October 2005

Recent applications of acoustical model testing to building design are described. The correlation of guidance so derived with other means of evaluation is stressed. Examples of application are: the determination of achievable ratios of direct to envelopmental and to reverberant sound levels in auditorium design, and correlation with recommended ratios derived from auditorium synthesis; sound isolation design for open office plans and correlation with calculations and full-scale measurements; sound isolation design for combined dining and entertainment spaces, and correlation with objective design criteria. As heretofore, the value of modeling is stressed in situations where acoustical design is much too complex for assurance and responsibility based on theory alone.
Modulated Air Flow Direct Radiator Loudspeaker
Authors: Olson Harry F.
Published: October 2005

A study of the theory, operation, and performance of a modulated air flow direct radiator loudspeaker has been carried out. As a result of the study, a research prototype of a modulated air flow direct radiator loudspeaker has been developed. The frequency range is 40–100 Hz. The maximum sound power output is 0.25 W for an audio input of 5 W. The electrical input is 120 W from 117 V ac. The space occupied by the loudspeaker is 18 cu ft.
Sound Levels of Emergency Warning Signals
Authors: Pierce E. Thomas , Leasure William A.
Published: October 2005

Field measurements were made of the sound-output characteristics of several emergency vehicle warning sirens. Measurements were made out-of-doors with the sound propagating over a hard reflecting surface. The sirens were mounted on typical emergency vehicles and signals from the microphone array were tape recorded as functions of microphone location and vehicle speed. The analog tapes were then frequency analyzed and the A-weighted sound levels calculated. Spectral as well as over-all sound level contour plots will be presented. These data will be the basis for a discussion of similarities and differences among various sirens tested. The sound levels at the driver's position in nearby vehicles will also be measured and the results discussed.
Ultrasonic Determination of the Bulk Modulus of Polyethylene Oxide
Authors: Corsaro Robert D. , Jarzynski Jacek , Davis Charles M.
Published: October 2005

An ultrasonic densitometer has been constructed for measuring volume changes of solids and liquids over a wide range of temperatures and pressures. Data are presented for the polymer polyethylene oxide. The high precision of this device has allowed the determination of the pressure and temperature dependence of the bulk modulus and calculation of the Anderson-Gruneisen parameter for this polymer. The values of this parameter are compared with the predictions of the model for linear polymers advanced by Broadhurst and Mopsik [J. Chem. Phys. 52, 3634 (1970)].
Effect of High-Frequency Vibratory Stress and Magnetic Barkhausen Activity in Some Metal Structures
Authors: Feith K. E. , Kerr G. S. , Whymark R. R.
Published: October 2005

Investigations directed toward a better understanding of the effect of intense sound on solid materials and their resultant reduction in strength has dictated a need for new methods of probing the microstructure of metallic materials. Magnetic Barkhausen noise has been investigated as one possible means of assessing the change in dislocation density introduced by the effect of vibratory energy. Measurements of Barkhausen activity, in nickel and iron wires, as a function of vibratory stress amplitude, magnetic fields, and frequency, were carried out. Data are presented which provide a link between magnetic domain wall motion, peak vibratory stress, and the rate at which vibratory stress is applied. [Acknowledgment is made to Dr. W. W. Lester for his contributions during the course of this work. This work sponsored in part by ONR Code 468.]
Decision-Theoretic Approach to Speaker Verification
Authors: Jayant N. S.
Published: October 2005

This paper develops upper bounds on the performance of a speaker verification system on the basis of a simple statistical model. The problem is to verify that a given measurement belongs to a claimed identity. A nonzero probability of impersonations is presupposed, and the verifier can (1) accept or (2) reject the claimed identity, or (3) refuse to take either of these actions. Corresponding costs-of-wrong-decision will be typically different. We characterize sample measurements by normal distributions, and provide explicit results for the case of efficient measurements whose interpattern variances are much greater than their intrapattern variances. In our specific model, this will imply that the probability-density-function (pdf) of a measurement under the “impersonator” hypothesis is “diffuse” in relation to the pdf of the same measurement under any of several “truepattern” hypotheses. We mention the suitability of a certain minimax strategy for the verification problem, and study its performance—for a binary-action (accept-or-reject) verifier-as a function of (1) a parameter which reflects the pecularity of the claimed identity, and of (2) the measurement dimensionality. Finally, we describe a variable-time-for-decision verifier designed to provide a prespecified performance; and note that, in our model, the expected-time-for-descision is greater when the customer is a true speaker than when he is an impersonator.
Variations of Design in Bat Sonar: A Comparative View
Authors: Novick Alvin
Published: October 2005

The orientation pulses of bats differ by species in frequency, frequency pattern, duration, repetition rate, and intensity. These design features also vary systematically with time during goal-directed flights such as inset pursuits, landings, or obstacle evasions. Several species using two quite different patterns, frequency-modulated or constant frequency, have now been studied in some detail. By interpreting their choice of pulse duration, repetition rate, and intensity in terms of the frequency pattern, we have come to a better understanding of what measurements the bats are making and which pulse parameters they are making use of. [This work has been supported in part by the National Institute of Neurological Diseases and Stroke.]
Coding and Processing in the Nervous Systems of FM-Signal-Producing Bats
Authors: Suga Nobuo
Published: October 2005

For echolocation, certain insectivorous bats emit frequency-modulated (FM) sounds in which frequency always sweeps from high to low. Neurons in the cochlear nerve and nucleus respond to various types of sounds, such as pure tones, FM sounds, and noise bursts, and are therefore not specialized for the analysis of the bat's orientation sounds. In the inferior colliculus and auditory cortex, however, there exist neurons which selectively respond to FM sounds. For the excitation of these FM-specialized neurons, the direction, range, and speed of frequency sweep are important factors. The FM-specialized neurons always have a large inhibitory area and respond to FM sounds sweeping across this area. Although seemingly paradoxical, such properties are easily explained by neural network models. Bats emit short FM sounds when certain parts of the brain are stimulated with electric pulses. The temporal pattern of emission differs according to the location of the stimulating electrodes. Many neurons in the lateral lemniscus and inferior colliculus are excited by the bat's own outgoing sounds, in spite of the contraction of the middle ear muscles, synchronized with sound emission. The lateral lemniscal neurons appear to be specialized for echo detection because of the facilitation of their responses to a second tone pulse (artificial echo), while the inferior collicular neurons appear to be specialized for echo ranging because they exhibit various types of recovery cycles, including temporary recovery. [Supported by grant GB-13904 and PIB-2103 from the N.S.F. and grant HSAA 53837 from the P.H.S.]
Time and Doppler Correlation for Passive Acoustic Ranging
Authors: Sebastian R. L. , Griffin J. N. , Boswell R. A.
Published: October 2005

In passive acoustic ranging, a correlation function is frequently used to measure the signal propagation time difference between two sensors, or between two paths to a single sensor. The same device can be used to measure the Doppler differences when the source is in motion. The joint use of time and Doppler differences can result in more accurate range estimation than is possible from time or Doppler differences alone. Examples are given of the use of the use of time and Doppler correlation in passive ranging on a submarine.
Generation of Infrasound by Atmospheric Turbulence
Authors: Meecham W. C.
Published: October 2005

Consider infrasonic atmospheric pressure variations, defined for our purposes to be in the period range from a few seconds to a few minutes. Such pressure fluctuations could come from nonpropagating pressure effects associated, for example, with the jet stream; such pressure variations are estimated. We shall be interested primarily in propagating pressure effects caused by atmospheric turbulence. Following standard aerosonic theory, which will be briefly reviewed, the intensity of low-frequency aerodynamic sound produced by upper atmosphere wind is estimated. The estimated power radiated by such aerodynamic sources is approximately that observed in noise measurements on the ground and in balloons. The infrasonic signals expected from large storms and from tornados will also be estimated and compared where possible with measurements. Certain characteristics of clear air turbulence could probably be sensed by arrays on the ground and this question will be briefly discussed. The possibility of sensing clear air turbulence in this way from moving aircraft will be examined.
Waveshape and Relative Phase: A Single Concept Film for Classroom Use
Authors: Strong William J.
Published: October 2005

Computer animation is used to illustrate the dependence of waveshape on the relative phases of the sine-wave components of various complex waves. Four standard waveforms (pulse, sawtooth, square, and triangular) are synthesized by using appropriate relative phases. The relative phases are then varied while keeping the spectrum constant in each case and the new waveshapes are synthesized. The waveshapes are generated with a PDP-15 computer and displayed on a CRT. The film is made by recording the CRT images on Super-8 film. A 4-min movie is presented.
Machinery Noise on Logging Operations in Mixed Woodlands
Authors: Embleton T. F. W. , Toole F. E. , Myles D. V. , Hirvonen R.
Published: October 2005

A statistical picture has been obtained of the noise produced by different types of machines employed on logging operations in typical forested areas of eastern Ontario and western Quebec. Noise levels were measured at the operator's ear, at 15 and 50 ft, and at greater distances while the machines were being operated normally. Thus state-of-repair, idiosyncrasy of operators, topographical conditions, etc., were accepted as they came and no attempt was made to approximate, or correct to, standard test conditions. It was found that chain-saw operators, with some exceptions, and skidder operators, with few exceptions, are working in noise levels exceeding the CHABA criteria for hearing-damage risk. This risk does not exist for operators of slashers, loaders, and other equipment. Noise from logging operations is just inaudible at a distance of 112 miles under average conditions. Where machine noise is of concern, e.g., to recreationists, logging operations should probably be kept at a minimum distance of 1 mile.
Vibration and Acoustic Signatures of a Rolling Element Bearing
Authors: Mitchell W. S.
Published: October 2005

An investigation was made of the vibration and acoustic response of an operating ball bearing under varying degrees of damage. This included defects on the inner and outer races, the bearing cage, and the rolling elements. Vibration and acoustic measurements were made simultaneously with a 6% octave band analyzer. The bearing was rigidly mounted with a press fit on its outer ring, simulating industrial practice. It was found that considerable energy, both acoustic and mechanical, is dissipated at the higher frequencies even in a satisfactory bearing. Moreover, the energy distribution within the two signatures is not similar. Thus, identification of machine faults by an acoustic measurement method is still questionable.
Amplitudes of Gravity and Acoustic Modes in Air Waves from Nuclear Explosions
Authors: Donn William L. , Balachandran N. K. , Posey Joe W.
Published: October 2005

Relative amplitudes of gravity and acoustic modes in the ground-level pressure fluctuations produced by acoustic-gravity waves at long range from nuclear tests show considerable variation. The acoustic modes have higher amplitudes than the gravity modes when stratospheric winds have strong components in the direction of propagation of the waves. When stratospheric winds are in the opposite direction, the acoustic modes have much smaller relative amplitudes. The results have been found to be valid for different test locations and various receiver locations. These observations have been verified theoretically by synthesizing infrasonic farfield pressure waveforms generated by nuclear explosions, using actual stratospheric temperature and wind data.
Acoustical and Optical Activities in Alpha Quartz
Authors: Mindlin R. D. , Oupin R. A.
Published: October 2005

It is shown that the classical equations of linear elasticity and electromagnetic theory can account for both acoustical and optical activities in elastic dielectrics if the stored electromechanical energy is assumed to depend on the polarization gradient in addition to the usual strain and polarization. Formulas for the acoustical and optical rotatory powers of alpha quartz are derived and the values of new material constants appearing in them are calculated from old experimental data for optical rotation and the new data for acoustical rotation obtained recently by A. S. Pine [Phys. Rev. B2, 2049–2054 (1970)].
Low-Frequency Ambient Noise Cutoff
Authors: Polak J. A.
Published: October 2005

There have been very few measurements of ambient noise levels at frequencies below 1 Hz. These measurements show the ambient level to increase steadily with decreasing frequency. Does this trend persist or is there some frequency below which the ambient level no longer increases or actually decreases with frequency? It is suggested that such a frequency may exist. Estimates place this frequency between 0.13 and 0.06 Hz for the ocean basins; higher values are expected for the shallow regions near the continents and lower values over the trenches.
Size and Distance Discrimination Using an Ultrasonic Aid for the Blind
Authors: Long Glenis R.
Published: October 2005

Blindfolded sighted observers made size and distance judgments based on information provided by the Kay Ultra aid for the blind. This aid feeds an audible tone to the user based on the difference between a frequency modulated ultrasonic beam and its returning echo. Distance judgments are, thus, based on pitch and size judgments on amplitude and scanning. Distance judgments were found to follow the traditional Weber's law and to be more precise than either visual perception or unaided echolocation. Size discrimination was also linearly related to stimulus magnitude and appears to be better than unaided echolocation but worse than vision. Changing the texture of the object upset both distance and size judgments. Changes in distance also upset size judgments, but changes in size did not upset distance judgments, indicating that distance judgments are more stable than size judgments.
Temporary Threshold Shift and Permanent Threshold Shift Due to Rock and Roll Music
Authors: Flugrath James M.
Published: October 2005

Previous studies of rock and roll music have concentrated on its intensity in relation to damage risk criteria or on its effect on the musicians. The present study investigated temporary threshold shift (TTS) in the participants. Over a 6-week period, 52 males and 86 females with a median age of 15 yr were randomly selected for testing after exposure to 0, 10, 20, 30, 40, 50, or 60 min of music (96–113 dBA). Recovery time was 2–5 min. Females were found to have more acute hearing—before or after exposure. The greatest TTS appeared at 6000 Hz. An abrupt TTS occurred at all test frequencies after only 10 min of exposure. An abnormal loss of hearing acuity was found in the 0-min exposure group. The possible permanent threshold shift (PTS) appeared to be related to previous exposure to rock and roll music.
Highway Noise Impact: A Case Study
Authors: Copley Lawrence G. , Cavanaugh William J. , Jan M. Ashraf
Published: October 2005

During the corridor study and design phases of a new highway it is now customary to perform an environmental impact study. Noise from automobile and truck traffic is usually a major environmental change which must be studied and its impact evaluated. Four alternative alignments for a section of proposed Route 52 in Worcester, Massachusetts were studied along with the noise impact on the surrounding community for projected 1990 traffic volume. Projected noise levels in dB (A) were compared with existing ambient noise levels based on measurements made in selected locations in the surrounding community over a typical 24-h period. A simplified scheme is discussed for assessing the subjective response of the community to projected increases in highway noise.
Noise Sources and Noise Abatement Potential for the Tracked Air Cushion Vehicle (TACV)
Authors: Bender E. K.
Published: October 2005

The tracked air cushion vehicle (TACV), currently being studied as a means of providing high-speed ground transportation, has some unique noise control problems not previously encountered in ground transportation systems. This study surveys the TACV noise sources and abatement potential of each source in light of the proposed criteria for sideline noise. Among the sources considered are the compressor, linear induction motor, current collector, and aerodynamic sources including the air cushion. Data from tests on the French TACV are presented and interpreted in terms of projections for the American TACV. [This study was supported by the Department of Transportation, Transportation Systems Center, Cambridge, Massachusetts, under contract.]
Tentative Damage Risk Criteria for Noise of Inflatable Restraint Systems
Authors: Pearsons K. S. , Dietrich C. W. , Bruce R. D. , Allen C. H.
Published: October 2005

Three independent tentative criteria for evaluating the effects of the noise of inflatable restraint systems (airbags) on hearing have been developed by extrapolating from the work of the National Academy of Science/National Research Council Committee on Hearing Bioacoustics and Biomechanics and others. The first criterion pertains to rupture of the eardrum. Even when the magnitude of the pressure pulse is below the eardrum criterion, it may cause internal damage. The risk of damage is determined by the shape and duration of the pulse to such an extent that two additional criteria are needed. Airbag noise is considered in two parts, one being the relatively smooth single acoustic pressure impulse that rises to a peak and falls again with negligible oscillation. To this part we apply the Modified A-duration criterion. The other part of the noise consists of the somewhat longer period of irregular pressure occillations, and to this we apply the Modified B-duration criterion. The tentative criteria are compared with experimental results [“Human Auditory Response to an Air Bag Inflation Noise,” National Highway Safety Bureau, Contract No. P. O. ♯9-1-1151, 1969]. [Study supported by the National Highway Traffic Safety Bureau, Contract No. DOT-HS-006-1-006.]
Propagation of Long Waves in Curved Ducts
Authors: Rostafinski W. , Buckens F.
Published: October 2005

Propagation of waves in curved ducts and pipes belong to the class of motion which is characterized by wave patterns totally different from those known in straight ducts or in unlimited space. The curvilinear boundaries are responsible for the appearance of a continuous standing radial wave which in turn affects the transmitted tangential waves. The purpose of this paper is to solve the problem of propagation of long acoustic waves in slightly and sharply bend ducts. This problem has been only partially analyzed by various authors. In this study two acoustic systems are considered which allow determination of the basic modes of motion and desribe the transition and distortion of plane waves as they propagate down the curved channel. A detailed study of the behavior of waves in junctions between straight and curved ducts will be given. Solutions and expressions for principal modes of the wave are obtained by using the linearized equation of motion solved for its characteristic values. This original approach required a novel use of Bessel functions to determine the characteristic values of the steady and the decaying fields of motion.
Experimental Study of the Effect of Studs on Sound Transmission Through a Single Plasterboard Wall
Authors: Lyon Richard H. , Rinsky Alan
Published: October 2005

A sound transmission facility has been constructed at M.I.T. This facility has a test opening of 9×14 ft. The source and receiver rooms are identical with dimensions of 15×19.4×12 ft. Room reverberation times and background noise levels are reported. The experimental transmission loss (TL) of a 12 in. plasterboard wall without studs compares well with its theoretical transmission loss, thereby verifying that the facility is operating properly for low TL walls. Experimental studies show the effect of varying the ratio of stud impedances to panel impedance by adjusting the lineal weight and moment of inertia of the studs. As the effective perimeter is increased by adding studs of sufficiently high impedance, a situation is reached where the sound transmission by resonant modes below the critical frequency exceeds the transmission due to mass controlled motion alone. The implication of these results on the design of stud reinforced walls is discussed.
Effect of Shear on the Transmission Loss of Thick Panels
Authors: Sharp Ben H.
Published: October 2005

One of the problems associated with concrete and masonry structures is their relatively poor acoustical performance in relation to their mass. A principal reason for this result lies in the fact that the critical frequency for these types of structures occurs at very low frequencies, sometimes as low as 100 Hz. The effect of coincidence, and the corresponding reduction in transmission loss in the vicinity of the critical frequency, results in the poor performance at low and medium frequencies. However, in the frequency region above the critical frequency, the theoretical transmission loss curve indicates values in excess of the theoretical mass law, whereas measurements show values that are substantially lower and that lie in a line essentially parallel to the mass law line. This presentation will briefly review the theory of the transmission loss of single panels including the effect of shear relating to the behavior of thick panels. Theoretical curves and experimental verification of the results for concrete and masonry structures will be presented. The application of the theory to the case of sandwich panels is discussed in connection with previous work by other authors. [This work was conducted under contract to the Department of Housing and Urban Development.]
Critical-Angle Phenomenon in Anisotropic Media
Authors: Henneke Edmund G.
Published: October 2005

The critical angle for reflection and refraction of stress waves at a plane boundary in anisotropic media is discussed in terms of the energy flux (or Poynting) vector. The critical angle is shown to occur when the energy flux vector associated with the reflected or refracted wave first becomes parallel to the boundary. The associate wave vector may be in a direction outside the medium, inside the medium, or parallel to the boundary. These three cases are discussed theoretically and possible real crystals are suggested in which these effects may be found. Knowledge of this effect is especially important in using the reflection technique at a liquid-solid interface to measure the phase velocity of stress waves in the solid since the phase velocity measured would not necessarily be that one along the surface.
Auditory Analysis of Time-Varied Sentential Approximations
Authors: Beasley D. S. , Shriner T. S.
Published: October 2005

Recent research has suggested that auditory perceptual processing and short-term memory are interrelated and temporally biased. A recommended manner for investigation of this concept is to co-vary stimulus duration (SD) and inter-stimulus interval (ISI) in recognition and recall tasks. The purpose of this study, then, was to investigate the recall accuracy of seven-word first- and second-order sentential approximations, co-varying SDs of 200, 300, and 400 msec, with ISIs of 100, 200, 300, and 400 msec. Ten monosyllabic sententlal strings of each order were read by a trained male speaker under controlled experimental conditions. Twelve experimental tapes representing the 12 possible SD/ISI combinations were then manually prepared. One hundred and twenty college-age normal hearing listeners heard the 20 sentential strings as processed under one of the 12 conditions and were required to recall the seven-word strings. The results of an ANOVA revealed significant main effects for ISI, WD, and Order, as well as interactions of WD×ISI, and WD×Order. Recall accuracy increased as WD increased, as ISI increased, and as Order increased. The WD×ISI and WD×Order interactions revealed that recall proficiency could be enhanced via a trading relationship between the interacting factors. The results are discussed in terms of their theoretical and clinical implications.
Radiation from a Spherical Source Eccentrically Positioned in a Fluid Sphere
Authors: Thompson William
Published: October 2005

Acoustic Radiation from a spherical source eccentrically positioned within a fluid sphere embedded in another fluid is evaluated. This configuration is an idealization of a spherical acoustic lens used as a sound projector. To effect a solution, the translational addition theorem for spherical wavefunctions is used to express series of wavemodes centered at one sphere in terms of modes centered at the other, thereby facilitating the task of satisfying the boundary conditions. Because spherical wavefunctions centered at one point are not orthogonal over the surface of a sphere centered elsewhere, each mode associated with the first sphere couples into every one of the modes associated with the other. Hence, the evaluation of the modal coefficients in the series for the radiated pressure necessitates solving an infinite set of equations. Approximate solutions are obtained by truncating the set to finite size and solving numerically. The source radiation impedance and farfield directivity have been calculated for representative values of the many parameters that characterize the problem, such as wavelength size of fluid sphere and source, relative characteristic impedances and sound velocities of the two fluids, and position and velocity distribution of the source. [Research was supported by the Ordnance Research Laboratory under contract with the U. S. Naval Ordance Systems Command.]
Detecting a Sound Radiation from Plates Using Long-Wavelength Acoustical Holography
Authors: Watson E. E.
Published: October 2005

Theoretical predictions have determined that farfield sound radiation from plates driven below a certain critical frequency is not generated from the entire surface of the plate, but only from certain zones on the plate. However, recent experimental work reveals that theoretical calculations and empirical evidence do not completely agree. Four plates driven at their center have been studied using holographic techniques. The reconstructions show that active sources exist at all the centers of the driven plates. Also, radiation was revealed at the edges of an unbaffled free circular plate and a baffled clamped circular plate. Radiation also is shown emanating from the ribs of two rectangular ribbed plates. In each case, certain hot spots were revealed suggesting the uneveness of the source distribution on the radiating plates.
Optical Wave Reconstruction from Acoustically Acquired Data
Authors: Greguss P. , Caufield H. I.
Published: October 2005

The difference between the recording and reconstructing wavelengths used in acoustical holography leads to a longitudinal distortion in the image. Furthermore, one of the important advantages of the three-dimensional nature of the hologram image, namely, the parallax effect, cannot be utilized unless resolution in the image is sacrificed by not using the full hologram aperture. This paper describes the experimental apparatus and a technique whereby the principles of multiplexing by holography are extended to 3-D representation of acoustically acquired data. It will be shown that full aperture sharing among the recorded wavefront of B-scans is compatible with off-hologram-plane sampling, so that the convenience of off-hologram-plane sampling can be combined with the image properties characteristic of the full aperture. Experimental results demonstrating the usefulness of the technique in ultrasonic diagnostics and nondestructive testing are presented. The possibility of using it in earth holography also will be discussed.
Cavitation in Liquid Helium Using a Piston-in-Cylinder Method
Authors: Vroulis T. , Neppiras E. A. , Finch R. D.
Published: October 2005

Experiments have been performed in which a piston is vibrated inside a glass cylinder containing liquid helium. The piston is driven by an electromagnetic shaker in the frequency range 10–100 Hz at an intensity capable of generating cavitation effects. At a certain critical particle velocity about 3 cm/sec noise is generated. This threshold velocity appears to be independent of frequency. A much higher velocity, about an order of magnitude greater, is required to produce visible bubbles in superfluid helium II. The significance of these results will be discussed. [This work was supported by the National Science Foundation.]
Vibrational Relaxation in SO2/O2 Mixtures
Authors: Anderson B. , Shields F. D. , Bass H. E.
Published: October 2005

Measurements of sound absorption due to vibrational relaxation in SO2/O2 mixtures indicate a vibration-vibration (v-v) coupling between the asymmetric stretching mode of SO2 and the vibrational mode of O2. The theory of Tanczos, modified to allow for four-quantum interchanges, was used to analyze the results. The sound absorption measurements of the 5% SO2/95% O2 and 10% SO2/90% O2 mixtures enabled the distinction between the series and parallel relaxation schemes in SO2. The measurements indicate that SO2 relaxes by way of the series process with the energy passing through the stretching modes into the bending mode by v-v energy transfer. SO2/O2 collisions are of the order of five times as effective as SO2/O2 collisions in producing v-v exchanges within the SO2 molecule. The theoretical fit to the experimental absorption data on 5% SO2/95% O2 and 10% SO2/90% O2 mixtures is improved slightly by including rotational relaxation absorption of the two molecules.
Ultrasonic Absorption Produced by Inversion Splitting in Octahedral Transition Metal Complexes
Authors: Hentz R. P. , Yun S. S.
Published: October 2005

The experimental investigation of ultrasonic absorption due to the inversion splitting predicted by I. B. Bersuker [Sov. Phys.—JETP 17, 1060 (1963)] was studied using undiluted single crystals of Cu3La2(NO3)12⋅24H2O. Each Cu++ is surrounded by six water molecules forming an octahedral complex. It is possible to excite these water molecules to oscillate with respect to an inversion center, and this excitation is predicted to yield an anomalous ultrasonic attenuation. The method used was the pulse-echo technique, and measurements were made along a number of crystal axes. The frequency dependence of the attenuation was found to be directly proportional to the frequency squared, and inversely proportional to the first power of the temperature; however, anomalous absorption was observed for the frequency range 10–170 MHz, and for a temperature range of 5° at 240°K.
Ultrasonic Attenuation Measurements Near the Upper Critical Field in Clean Niobium
Authors: Carsey F. , Levy M.
Published: October 2005

Ultrasonic attenuation measurements are reported for the superconducting transition in clean niobium. Linear relationships are found between measured attenuation and magnetic field as well as between attenuation and temperature. Data taken in the two experimental situations q⊥H and q∥H are compared with an effort to measure the anistropy of the flux line lattice. Here q = 2π/λ, the ultrasonic phonon wave vector for phonons of wavelength λ and H is the external field. [Work supported by Air Force Office of Scientific Research, Grant AFOSR 71-2079.]
Three-Directional Dynamic Green's Function for Thin Shells by Modal Expansion
Authors: Wilken Irvin D. , Soedel Werner
Published: October 2005

A general expression for the three-directional dynamic Green's function for vibrating thin shells is expressed in terms of mode shapes and natural frequencies by the modal expansion technique. The response in three directions, one component normal to the shell surface and two components tangential to it, is defined for general forcing functions with components in these three directions when the mode shapes are given in these directional components. As an example, the three-directional dynamic Green's function for the simply supported cylindrical shell is evaluated. Treatment of the nonpreferential orientation of the modes of shells of revolution is illustrated.
Acoustic Properties of a Two-Mass Model of the Vocal Cords
Authors: Ishizaka K. , Flanagan J. L.
Published: October 2005

The acoustic theory of a two-mass model of the vocal cords is outlined. An interactive DDP-516 laboratory computer is used to implement the vocal-cord model and a coupled vocal tract. The digital simulation shows the two-mass model to correspond in acoustic behavior to observations made on human vocal cords. Realistic results are obtained for fundamental frequency of vibration, duty factor, waveform of glottal volume velocity, source-system interaction, and dependence upon subglotta1 pressure, cord tension, and phonation-neutral area.
A Study of Buccal Speech
Authors: Weinberg B. , Westerhouse J.
Published: October 2005

Buccal speech represents one of several types of alaryngeal speech; however, its use as a primary method of alaryngeal communication is exceedingly rare. An intensive study of a normal subject, highly proficient in the use of buccal speech was undertaken to obtain information about the mechanism of buccal phonation, the fundamental frequency, phonation time, intelligibility, and rate characteristics of buccal speech. Comparisons were made among the acoustic and perceptual characteristics for buccal, esophageal, and normal speech. The results of the present experiment support the hypothesis that buccal speech does not represent an efficient primary method of alaryngeal speech. [This research supported in part by the Delaware County Cancer Society].
Responses of Inferior Collicular Units in the Chinchilla to Binaural Stimuli
Authors: Adams J. C. , Teas Donald C.
Published: October 2005

Extracellularly recorded discharges of units in the inferior colliculus of the Flaxedilized chinchila will be described. The two ears were stimulated independently so that interaural intensity and phase could be manipulated. Of those units encountered whose activity could controlled by acoustic stimuli below about 2 kHz, a large majority were found to be differentially responsive to alterations of interaural phase and intensity. The time patterns (histograms) in response to binaural stimulation showed characteristic alterations of excitation and inhibition similar to those which have been reported for neurons in the cat. The effect of interaural phase changes could be maximized by appropriate choice of interaural intensity differences.
Vertex Potential in Sensory Hearing Loss
Authors: Nichols Thomas L.
Published: October 2005

The pedestal-plus-increment stimulus paradigm I described at the Society's San Diego meeting was administered to subjects with known sensory hearing loss. These subjects, who had histories of exposure to high-intensity noise while in military service, showed both marked high-frequency loss and recruitment when tested by conventional audiometric methods. The averaged auditory evoked potential (vertex potential) was measured at a low frequency where the subjects' auditory thresholds were near normal, and at a high frequency where their thresholds were approximately 50 dB above normal. At both of the pedestal levels employed, the functions relating log (N1−P2) to ΔI (the magnitude of the 150-msec increment) differed markedly. At the lower frequency, the functions resembled those obtained from normal subjects; at the higher frequency, increments as small as 1 dB yielded N1−P2 potentials of approximately 10 μV. At this higher frequency, the vertex potential was near its maximum for a 1-dB change in stimulus level, and increases in ΔI up to 12 dB resulted in only slight increases in N1−P2. These findings suggest that this method may prove useful in the detection of recruitment of loudness.
Properties of Period Histograms from a Nonlinear Model of Cochlear Nerve Fiber Activity
Authors: Matthews John W. , Pfeiffer Russell R. , Molnar Charles E.
Published: October 2005

Properties of period histograms of responses to continuous sinusoidal stimuli were studied in a model for cochlear nerve fiber activity consisting of a bandpass nonlinearity and an analog neuron. The analog neuron is a device that has adjustable threshold, recovery time-constant, and amplitude of “depolarization.” It accepts an analog waveform from the bandpass nonlinearity, and generates a pulse train output analogous to a train of spike discharges. In addition, noise is provided to simulate spontaneous. activity. We have studied nonlinear properties of the period histograms for various neuron and stimulus parameters and for various levels of spontaneous activity. Some of the observed nonlinear effects are solely due to the neuron, others are due to the bandpass nonlinearity. These results indicate that caution must be taken when attempting to relate nonlinear properties of response patterns to specific elements in the peripheral auditory system. [This investigation was supported by PHS research grants from the National Institutes of Health.]
Anomalies of Response Patterns of Single Cochlear Nerve Fibers to Click Stimuli
Authors: Pfeiffer Russell R. , Kim Duck On
Published: October 2005

Spike discharge patterns of single cochlear nerve fibers in response to acoustic clicks suggest that the cochlear neuron is excited by an oscillatory waveform that is half-wave rectified. The number of effective cycles of excitation as well as other details for both rarefaction and condensation click stimulation have been studied for more than 600 fibers with characteristic frequencies (CF) below 1750 Hz. We find that: (1) the number of cycles of oscillation to which fibers respond varies from a few to as many as 26! (2) On the average, the number of oscillations to which a fiber responds is proportional to its CF, 2.7 cycles for CF < 300 Hz to an average of 7.4 cycles tot 1500 <CF <1700 Hz. (3) The duration of the preferred times of spike discharge, as illustrated by the width of the individual peaks of PST histograms, varies depending upon the cycle of oscillation of the excitation and on the polarity of the click. (4) For about 5% of our data the “envelopes” of the PST histograms are modulated, implying a variable sensitivity during response. This group on the average responds to 9.1 cycles of oscillation vs 5.4 cycles for the remainder of our population. (5) Finally, the preferred times of discharge of responses to rarefaction and condensation clicks do not always interlace, as commonly believed. Preferred times of discharge for fibers with CF below 200–350 Hz overlap for opposite polarity clicks, and frequently show a dramatic reduction in response to clicks of one polarity. These details can assist in the studies of transducer activity within the cochlea. [This investigation was supported by PHS research grants from the National Institutes of Health.]
Exhaust Noise Field Generated in the JT3D Core Engine—Noise Floor Presented by the Internal Noise Sources
Authors: Grande E.
Published: October 2005

An experimental study has been conducted to determine the strength of the acoustic radiation generated in the combustion and turbine stages of a JT8D core engine and transmitted out through the primary jet exhaust duct. The acoustic field within the tall pipe duct extension was measured by an array of microphones flush-mounted on the extension wall. The interpretation of the cross-power spectral densities of the microphone signals by means of a theoretical model of the sound propagation within the duct permitted the acoustic energy transmission out of the nozzle exit to be determined. The results show that the internally generated noise is a dominant noise component from the core engine at larger angles from the jet axis for the case of low engine power settings. In general, although the internally generated core engine noise component lies well below the JT8D engine jet-noise and fan-noise components at the higher engine power settings, it represents an additional noise parameter that must be considered in the application of fan-noise and jet-noise suppression techniques. [Work accomplised when the author was a member of the Aircraft Noise Staff of the Boeing Company, Seattle, Washington.]
Engineering Models for Aerodynamic Noise Environments
Authors: Crenwelge Otto
Published: October 2005

Engineering models have been constructed for several aerodynamic noise environments typical of those exciting random vibratory response on aerospace vehicles during subsonic, transonic, and low supersonic flight. Data for these models were obtained from the publications of various investigators. The data are nondimensionalized with respect to common parameters, so that statistical properties of the various environments may be compared directly and some insight into the physical phenomena producing differences between the environments may be obtained. The specific models presented describe the fluctuating wall pressures produced on smooth surfaces by subsonic turbulent boundary layers with zero, mild-adverse, and mild-favorable mean-pressure gradients; supersonic turbulent boundary layers; and oscillating shock interaction with separated flow in the vicinity of compression corners at supersonic speeds. Nondimensional statistical properties used to describe the models are fluctuating pressure coefficients as a function of free-stream Mach number, pressure spectral densities, stream-wise and transverse root-coherence and phase, and convection/free-stream velocity ratios. [This work was performed under contract for NASA, Manned Spacecraft Center.]
Acoustic Streaming near a Cylinder in Crossflow
Authors: Hribar A. E.
Published: October 2005

Several investigators have found increases in heat and mass transfer rates of several hundred percent from a circular cylinder in crossflow with an intense sound field acting perpendicular to the cylinder and the crossflow. A rough, two-dimensional approximation of the flow field was obtained by superposition of potential flow over a cylinder and Schlichting's solution for acoustic streaming about a cylinder in an unbounded quiescent fluid. Photographs were taken of the actual flow field at various sound pressure levels and crossflow velocities. Tobacco smoke was used to render the flow visible. The approximate model and the photographs were compared. Limitations of the model and a hypothesis for the observed mass transfer rate increases are discussed.
Preliminary Investigation of the Aeroacoustics of Jets Perturbed by Screens
Authors: Arndt Roger E. A.
Published: October 2005

It is observed that the placement of a screen across the exit plane of a jet nozzle results in a substantial reduction in noise intensity over what would be realized with an equivalent unperturbed jet. The general features of this phenomenon are analyzed experimentally utilizing both acoustic and velocity (hot wire) measurements. Acoustic radiation data from a jet operating in the Much number range 0.2–0.6 indicate that the insertion of a screen into the flow can reduce the maximum intensity by as much as 14 dB. Associated with this noise reduction is a loss of directivity and a substantial flattening of the power spectrum. Comparison with the spectrum of unperturbed jets indicates that the noise radiation from both the mixing and adjustment regions of the jet is affected. Hot wire data indicate that the predominant change in the mixing characteristics occurs at the interface between the potential core and the outer mixing region. Turbulence scale and mean shear are reduced which, on theoretical grounds, is consistent with the acoustic observations.
Perceptual Features of Nine English Consonants Determined by Choice Reaction Time
Authors: Weiner Frederick , Singh Sadanand
Published: October 2005

Nine English consonants were presented in pairs for the judgments of same/different to 10 subjects. Subject's choice reaction time (CRT), in making the above judgment, was considered to represent the interpoint distance of the criterion phoneme in subjects' perceptual space. A multidimensional analysis (IND-SCAL) showed that the magnitude of subjects' CRT for determining the sameness or differentness of a phoneme pair was governed by the distinctive features of these sounds. The features retrieved from a three-dimensional analysis were (1) sibilant, (2) voicing, and (3) place. It was further shown that phoneme pairs distinct by zero, one, two, or three feature differences had significantly different CRTs. Pairs having a “zero” feature difference had significantly greater CRTs than pairs different by one-three features. Similarily, pairs with a one-feature difference had significantly greater CRTs than those with a three-feature difference. Within one-feature comparisons, CRT associated with sibilant was shortest following by the features place and voicing. This indicated greater distinctiveness of sibilant than place and voicing. Voicing showed the longest CRT, thus indicating minimal perceptual distinctiveness.
Consonant Confusions in Patients with Sensorineural Hearing Loss
Authors: Bilger R. C. , Wang M. D. , Jesteadt W. H.
Published: October 2005

Confusion matrices were obtained for 22 patients on four sets of nonsense syllables, using a forced-choice procedure. Each syllable set considered of 16 consonants in combination with the vowels /i,a,u/ either in CV or VC form. Syllables were presented at a comfortable listening level approximately 40 dB above the audiologic SRT. Over-all performance varied as a function of syllable set, vowel, and hearing loss. The confusions were analyzed by two multidimensional scaling procedures, MDSCAL and IND-SCAL. In addition, an iterative feature analysis of transmitted information was performed, in which the feature system of Miller and Nicely and Chomsky and Halle were compared. [Research supported by grants from SRS and NINDS.]