bluuebunny/crossref_metadata_2025 huggingface dataset:
Cascade Models of Vibration Transmission in Flight Vehicles
Authors: Scharton Terry D. , Franken Peter A.
Published: September 2005

Cascade models offer a simple explanation of high-frequency vibration transmission in aerospace vehicles subjected to localized excitation sources. Vibration-transfer data from a variety of aerospace programs have been reduced to a common base by utilizing a “characteristic length” of the transmission path to scale the frequency axis. The results from several programs indicate that the degree of excitation coherence significantly affects the nature of the transmitted vibration. An example is presented to illustrate the use of cascade models to assess the relative importance of parallel vibration-transmission paths.
Transmission of Sound and Vibration to a Shroud-Enclosed Spacecraft
Authors: Manning Jerome E. , Lyon Richard H. , Scharton Terry D.
Published: September 2005

The flow of high-frequency vibratory energy to a shroud-enclosed spacecraft is discussed. Two paths of energy flow are considered: first, the acoustical path along which energy flows from the external exciting field through the shroud and interior acoustic space to the spacecraft; and, second, the mechanical path along which energy flows from the external field through the shroud and spacecraft mounting trusses to the spacecraft. Theoretically predicted response levels in octave frequency bands for a model of the OGO spacecraft assembly are presented. These predictions show that the spacecraft response to energy transmitted along the acoustic path is at least a factor of 10 greater than the response due to energy transmitted along the mechanical path over the frequency range 250–8000 Hz. Methods to reduce the spacecraft response are discussed. [Research supported by National Aeronautics and Space Administration.]
Creeping-Wave Pulses on Soft Cylinders
Authors: McNicholas J. V. , Überall H.
Published: September 2005

The formalism of the creeping-wave theory has been extended to enable calculations of various incident pulse forms. The particle velocity on the cylinder surface and the pressure radiated to a far-distant observer have been obtained for various pulse shapes. The incident pulse shapes studied are: (1) the delta function, (2) finite modulated step pulse, and (3) finite unmodulated step pulse. The growth curves of particle velocity and pressure have been calculated as a function of a reduced time τ. In addition, the creeping-wave speed and attenuation angle are given for the case of the delta pulse and the finite modulated step pulse. [Work supported by the Naval Ship Research and Development Center and the Office of Naval Research.]
Wave Theory of a Variable-Density Luneburg Lens
Authors: Boyles C. Allan
Published: September 2005

Previously, the author [J. Acoust. Soc. Am. 43, 709–715 (1968)] showed that the correct wave equation needed to describe the propagation of sound in an acoustic Luneburg lens is ∇2p − ∇ lnρ⋅∇p = (n2/Co2)∂2p/∂t2, where p is the acoustic pressure, ρ the density, Co a constant reference speed, and n2 = 2 − (r/a)2 is Luneburg's index of refraction. Here a is the lens's radius and r any radial point within it. A similar equation holds for the electromagnetic Luneberg lens with the dielectric coefficient ε replacing ρ. However, ε = n2 and consequently, it can be only one possible function of position. This is not so for the acoustic case, since ρ = n2/κCo2 (κ the compressibility), and κ can be a function of position. Previously, we investigated the case where ρ was approximately constant, so we could neglect the density-gradient term in the wave equation. (Strictly speaking, ρ cannot be constant if n is a function of position.) This case corresponds to W. J. Toulis' compliant-tubing lens, and we found that the theory agreed well with experimental data. In this paper, we examine a different possibility, viz., κ constant and ρ a function of position given by ρ = n2/κCo2. We then compare the two cases.
Theory of TTS
Authors: Botsford James H.
Published: September 2005

Laws stating that TTS varies as the logarithm of time disagree with experimental results very early or very late in these processes. Better agreement with observations results from regarding TTS as the sum of four components that vary exponentially with time. During constant stimulation, each component increases, approaching an upper limit asymptotically. After stimulation is terminated, each component diminishes toward zero asymptotically. Using data from published TTS studies, the magnitude and time constant of each component was determined. One component grows toward a limiting value dependent on stimulation intensity and test frequency, gaining half the remaining magnitude every 45 min; and decays afterward so that the magnitude is halved every 3 h. Another component grows to about 13 dB in most exposures and, afterward, decays to half-value every 8 min. Two more components, one positive and the other negative, decay at rapid but different rates to produce the “bounce” often observed during the first 2 min of recovery. Only the first-mentioned component seems related to permanent noise-induced hearing loss. The simple electrical analog of the theory makes possible a simple TTS meter for appraising noise hazard.
Ear-Protector Measurements: Are They Meaningful?
Authors: Schiller Elaine , Rosenfeld Jack B. , Fadigan James F.
Published: September 2005

An intensive study of the attenuation properties of numerous ear protectors and the statistical treatment of the data obtained, explains and/or documents many previously suspected or noted irregularities in measurement procedures. Detailed data on subjective measurement, directionality, linearity, and asymmetry of attenuation of ear protectors were collated. These findings will be presented along with a description of the nonparametric statistics used to ascertain central tendencies, sources and magnitudes of variability, and degrees of correlation of the data. In the study, nine ear protectors, 10 trained subjects, and two artificial heads were utilized. The USA Standards Institute's method (i.e., free-field threshold shift) was used to obtain subjective measurements. The artificial heads were employed for the acquisition of detailed information on the noise-exclusion properties of each ear protector.
Impulse Duration and Temporary Threshold Shift
Authors: Loeb Michel , Fletcher John L.
Published: September 2005

Subjects were exposed, on different test days, to 166-dB (peak, normal incidence) impulses 34, 58, 72, or 96 μsec in duration spaced 1 sec apart. For each pulse duration, the subjects were first exposed to one pulse, then the number of pulses was doubled on successive days until the temporary threshold shift (TTS) following exposure exceeded 30 dB. Intercorrelations of numbers of impulses required to reach criterion TTS at each duration were obtained; they were highest when durations were similar. At the largest pulse duration, a median of only four impluses was required to achieve criterion; some individuals exceeded criterion at one impulse, while others required hundreds. No evidence was seen of a 4-kHz notch; maximum shift was at high frequencies (10–15 kHz) and relatively independent of impulse duration. There is reason to believe if one exceeds allowable TTS in the speech-range frequencies with this kind of impulse noise, there is a chance of producing permanent high-frequency loss.
Levator and Palatoglossus Muscles in Movements of the Soft Palate
Authors: Fritzell Björn
Published: September 2005

The activity of the various palatal muscles in speech was recorded by means of electromyography. Specially designed needle electrodes were passed through the nasal cavities for recording from the levator, the tensor, and the superior constrictor muscles. Very fine wire electrodes were inserted transorally for recording from the palatoglossus and palatopharyngeus muscles. The electrodes did not noticeably interfere with speech. In a study on normal subjects, the levator and the palatoglossus demonstrated the most consistent patterns of activity, that of the levator being closely related to velopharyngeal closure, and that of the palatoglossus to the opening of the velopharyngeal portal. Cinéradiography was carried out synchronously with EMG recordings from these two muscles. An analysis of the relationships between muscle activity, movements of the soft palate, and speech produced by the subjects will be presented. [Research supported by U. S. Public Health Service grants.]
Temporal Characteristics of Palatal Movement
Authors: Speaks Charles , Benitez Luis
Published: September 2005

Observations were made of temporal characteristics of palatal movement during speech on a patient with a surgically created facial defect. Frame-by-frame analyses were made from color film exposed at a rate of 146 fps. Three indices of movement during the closing and opening phases of excursion were utilized—absolute time, percent of total excursion time occupied by each phase, and the closing opening (C-O) ratio. C-O ratios for vowels and oral consonants approximated 1.5:1. For nasal-vowel utterances, the ratio increased to 2:1; for vowel-nasal utterances, the ratio was 0.7:1. A set of expected values was derived from CV and VC data to predict the temporal characteristics for CVC utterances. The accuracy of the expected values for predicting measures of absolute and relative timing characteristics will be described. The greatest error was associated with absolute time (30–80 msec). Relative measures of palatal excursion time, however, were exceedingly stable.
Tongue-Body Motion during Selected Speech Sounds
Authors: Houde Robert A.
Published: September 2005

The articulatory behavior of the tongue body was observed and related to the phonemic representation of speech through the use of cinéradiography at 100 frames/sec. Specific points on the tongue-body surface were identified by the attachment of small radiopaque markers. Points on the jaw and each lip were also marked. The motion of these markers was observed during the production of nonsense trisyllables constructed from /i/, /ɑ/, /u/, /b/, /g/ in the form V1 CV2 CV1, with various conditions of stress as produced by a single speaker. Target positions were identified for each point marker corresponding to each phoneme. The transitions between target positions were observed. It was determined that the principal motion between vowel target positions could be characterized by a single characteristic transition function. Deviations from this principal intertarget motion that appear to be related to perturbations in oral pressure were observed.
Acoustic Reverberation at the Sea Surface: Surface and Sublayer Spectra vis-à-vis Scattering and Reflection
Authors: Martin John J.
Published: September 2005

This paper combines previously developed theories of surface and volume scattering and reflection with published and previously unpublished acoustic reverberation data to develop a composite theory for reverberation strength as a function of acoustic frequency, incidence or grazing angle, and sea-surface wind speed. In passing, spectra of sea-surface roughness and of the surface sublayer turbulence are developed, these spectra being consonant with theoretical and experimental estimates.
Near-Grazing Specular Scatter of Underwater Sound from a Wind-Driven Model Sea Surface
Authors: Scheible Jack W. , Fowler Richard C. , Medwin Herman
Published: September 2005

A model sea has been generated by wind over a large anechoic tank. The wave-height distribution, rms height, σ, surface energy-frequency spectrum, and the crosswind and downwind surface spatial correlations have been measured for a homogeneous section of this statistically stationary, anisotropic surface. Underwater sound was scattered from this surface. The distribution, mean, and variance of the specularly scattered pressure were measured and compared with reflection from a smooth surface. Several thousand data points were obtained for each of several frequencies and angles of incidence, θ. Most of the data were taken at angles near grazing, where the usual theories cannot be expected to hold because of shadowing and multiple scattering. According to various theories, the mean-squared specularly scattered pressure (relative to a mirror surface) should vary as e−g for g≪1(g12 = 2kσ cosθ), and the distribution should be approximately Gaussian. Experimental results are compared with theory, and differences are discussed. [Work supported by Naval Ship Systems Command.]
Relation of Hearing Loss to Cochlear Histopathology Produced by Antibiotics in the Monkey
Authors: Stebbins W. C. , Johnsson L.-G. , Hawkins J. E.
Published: September 2005

A method is described for evaluating the effects of ototoxic drugs on hearing in monkeys by behavioral audiometry and phase-contrast microscopy of Corti's organ. To date, four animals have been trained by operant conditioning procedures with food reinforcement and pure-tone thresholds determined by the psychophysical method of constant stimuli. After the normal threshold curve was established (0.5–15 kHz), kanamycin or neomycin was administered daily (100 mg/kg i.m.), and the development of hearing impairment was followed. When a profound loss had appeared in one or more of the higher octaves, the animal was sacrificed and the temporal bones were fixed with osmic acid for microdissection and study of changes in the inner ear by stereo- and phase-contrast microscopy of surface preparations. Hearing impairment followed an orderly progression from the highest frequencies downward and was clearly correlated with the extent and pattern of destruction of Corti's organ found post mortem. [Research supported by U. S. Public Health Service grants.]
Lateral-Line Sensitivity
Authors: Weiss Burton A.
Published: September 2005

Many studies have employed various physical, physiological, and morphological techniques to assess the functional sensitivity of the lateral-line organ. Controversy has developed mainly because determination of functional sensitivity of any sensory system requires behavioral analysis. The behavioral technique of shock-avoidance conditioning of goldfish to tonal stimuli in an aquatic shuttle box has yielded curves of intensity thresholds as a function of frequency for the lateral line. These curves are distinctly separated from those of the inner ear by the absence of generalization of the conditioned response between the lateral-line and inner-ear modalities of the goldfish. Lateral-line sensitivity appears most functional in the region of frequencies below 100 Hz.
Acoustic Stimulator for Rats
Authors: Crowley David
Published: September 2005

The ear bar of a stereo-taxic instrument was modified to permit the introduction of acoustic stimuli to the rat's eardrum during acute experiments on the auditory nervous system. For measurement of the sound pressure of pure-tone stimuli, a probe microphone was attached to the hollow ear bar so that the probe tube tip is placed near the eardrum. Pure tones are led through a fiber tube in the wall of the experimental chamber to the hollow ear bar. Tones between 100 and 15 000 Hz are produced by an electromagnetic speaker, while higher frequencies are generated by an electrostatic transducer. Acoustic transients are produced by a 1-in. condenser microphone operated as a loudspeaker attached to the hollow ear bar inside the experimental chamber. The acoustic waveform of these transients was measured with a 14-in. condenser microphone situated at the end of a 0.08-cc coupler, which is placed on the hollow ear bar to take the place of the rat's bulla. The three sound-producing devices can be interchanged without disturbing recording electrodes or the probe microphone. [Research was supported by the National Institutes of Health and Middlebury College.]
Noise-Reduction Study in a Scaled-Model Acoustic Test Facility
Authors: Tomren Raymond H. , Brandtzaeg Per
Published: September 2005

The acoustic properties of five insulation materials were investigated in a 110-scale model acoustic facility. The materials were designed for applications in space vehicles. The model facility, consisting of a reverberation chamber coupled to an anechoic chamber, was evaluated for its use in noise-reduction testing. It was found that a reasonably diffuse sound field existed above 900 Hz. Modal-density graphs of the reverberation chamber and spatial acoustic gradients measured within the chamber and across the test-panel opening are compared to an idealized facility. [This work was performed for the National Aeronautics and Space Administration under contract.]
Noise-Control Design for the Main Hall of the Canadian National Arts Center in Ottawa
Authors: Miller Laymon N.
Published: September 2005

The main auditorium of the new National Arts Center in Ottawa is bounded by several mechanical equipment rooms that house the air-handling equipment for the auditorium and its stage area and for some of the other parts of the total complex. Noise-control design includes: (1) control of fan noise through the ducts, (2) control of fan noise into the mechanical rooms themselves, (3) control of the escape of mechanical room noise into the auditorium and stage areas, (4) control of air movement noise in the ducts, and (5) control of damper and diffuser noise. Vibration control includes the vibration isolation of fans, pumps, ducts, and piping in various crucial locations. The exterior shell of the building has been designed to exclude city noise and to limit the intrusion of aircraft noise. A very brief summary is given of the noise criterion goals and the design objectives for achieving those goals.
High-Power Underwater Sound Sources Using Ceramic Ring Elements
Authors: McMahon G. W.
Published: September 2005

Transducers comprising free-flooding ring elements of lead zirconate titanate ceramic have been built and tested. The elements are operated in the coupled ring-cavity mode over the octave band from 2000 to 4000 Hz. Performance results are presented for single elements and a directional line array. A source level of 112.3 dB re 1 μbar at 1 m has been obtained from a single ring at a depth of 60 m, representing a radiated acoustic power of 11.2 kW and an efficiency of 87%.
Mathematical Model of the Flextensional Underwater Acoustic Transducer
Authors: Royster Larry Herbert
Published: September 2005

The basic design principles of the flextensional underwater-acoustic transducer are investigated by developing a mathematical model representation for this type of transducer system, and then establishing the effects that the various geometrical parameters have on the systems performance. The acoustic radiation problem is solved by numerically evaluating the Helmholtz integral for the farfield and nearfield pressure distributions. The mechanical-shell vibration problem is simplified by replacing the continuous shell with an analogous framework consisting of a series of bars and joints and having a finite number of degrees of freedom. Finally, the coupled stack wave equation is solved in terms of an arbitrary terminal impedance that simulates the combined impedance of the shell and acoustic-radiation impedances. Values of transducer impedance, farfield radiation pressures, and effective electromechanical coupling coefficients are calculated and compared with published experimental values for the University of Miami flextensional underwater acoustic transducer. [This research was supported by the U. S. Office of Naval Research, Acoustics Programs.]
Free Vibrations of Beams with Flexible Boundary Conditions
Authors: LeBlanc C. L.
Published: September 2005

In the design of flexural transducer elements in the form of beams and plates for high-power applications, nonideal support mechanisms are sometimes employed in the structure to ensure mechanical stability. The influence of these flexible boundary conditions on the fundamental resonance, mode shape, and stress distribution in a bilaminar beam composed of polarized ferroelectric ceramic (PZT-4) material is analyzed according to linear elasticity theory. An effective electromechanical coupling-coefficient ratio, based on an energy distribution in the composite structure, is derived. The results indicate that there are optimal support-mechanism dimensions, which allow for maximum coupling in the system and maintain acceptable stress levels in the ceramic.
Calibration of the Transmitting and Receiving Modes of a Transducer Array
Authors: Chertock George
Published: September 2005

The sound field of a transducer array used as a transmitter is completely specified by the field at any closed surface about the array. In principle, measurements made at the surface could be processed to yield the sound pressure at any external point. The theoretical transfer function that applies to an arbitrary surface and an arbitrary field point is derived in a form that could be realized by a network that adjusts for field-point position in a simple way. Alternatively, when the array is used to receive the signal from some external field point, the sound-pressure distribution at the array could be simulated by a source distribution on the arbitrary closed surface. The source distribution for this application is exactly the same function of surface shape and field-point position as the transfer function of the first case, and is likewise independent of the size, shape, and surface impedance of the array. In both applications, there are errors to be discussed, which are due to approximating the continuous surface distribution by a finite number of elements.
Computer Simulation of Sharpening Effects on Response Areas of Single Auditory Units
Authors: Nomoto Masahiro
Published: September 2005

This simulation deals with the problem of the neural mechanisms that may be responsible for the sharpening of response areas, in terms of sound frequency, that were observed in single neurons of the upper-auditory relay nuclei. It assumes that there is tonotopic localization and lateral inhibition in each nucleus. The model is a network that consists of elements with similar connections. The parameters of the model were varied until an appropriate sharpening was obtained. It became clear that a threshold parameter for individual elements was also necessary to create a sharpening similar to the sharpening seen in electrophysiological experiments. The presence of spontaneous activity served a little to emphasize the sharpening. The study also indicates that a negative feedback, i.e., recurrent inhibition, was necessary for obtaining reliable responses over a wide range of sound intensities. [Work supported in part by National Institutes of Health International Postdoctoral Fellowship, and in part by NIH grants and the Joint Services Electronics Program.]
Neural Correlates of the Aural Combination Tone 2f1−f2
Authors: Goldstein J. L. , Kiang N. Y. S.
Published: September 2005

Responses of single fibers in the auditory nerve of anesthetized cats show evidence of combination tones when the acoustical stimulus consists of two sinusoidal tones. The stimulus frequencies were chosen so that the combination frequency 2f1−f2, where 1 < f2/f1 < 2, was approximately equal to the characteristic frequency of the fiber. The major findings are: (1) For every fiber, a portion of the responses was locked in time to individual cycles of a reference combination tone. (2) The time-locked responses could be canceled by adding a combination tone to the stimulus. (3) The stimulus frequencies could be chosen to obtain a response that was predominantly time locked to the reference combination tone. (4) The rates of discharge for both single and two-tone stimuli have a similar dependence upon sound level. These findings are closely related to psychophysical measurements of aural combination tones. [Work supported by NIH grants, the Joint Services Electronics Program, and a NASA grant.]
Cochlear Microphonic Response of Guinea Pig to Two-Tone Stimulation
Authors: Nieder P. , Nieder I.
Published: September 2005

The nonlinearity of the distributed generator for the cochlear microphonic has been investigated using the modulation technique. In the presence of a suitably intense low-frequency stimulus, the microphonic response to a high-frequency stimulus is amplitude modulated during each cycle of the low-frequency response. For frequency pairs giving responses similar to those predicted on a single-generator model, the transfer characteristic may be inferred from the modulation data. Interference effects between the two stimuli appear mainly to depend on the nonlinearity of the generator, but discrepancies exist that are apparently due to traveling-wave effects. Summating potentials as measured for the test frequencies are also in general agreement with predictions based on observed transfer characteristics, but, especially for high frequencies, the filtering effect of the traveling wave must also be considered. [Work supported by a grant from the National Institute of Neurological Diseases and Blindness, National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare.]
A Cochlear Temporal Nonlinearity Determined from Spike Discharge Patterns for Combination Click Stimuli
Authors: Pfeiffer Russell R. , Goblick Thomas J.
Published: September 2005

The nulling technique described in the preceding abstract has been used to study the responses of cochlear nerve fibers with low characteristic frequency (CF) to combination click stimuli. For a given fiber the intensities of two clicks separated by some multiple of half the period of the fiber's CF can be adjusted to null a particular peak in the corresponding PST histogram. If the two clicks are assumed to produce identical, linearly superposing click excitation functions (CEF's), the relative amplitudes of adjacent peaks of the CEF can be obtained from nulls in the PST histograms obtained with a click separation of half the period of the CF of the fiber. The relative amplitudes of peaks separated by k half-periods can be obtained indirectly from these measurements or by direct measurement using the nulling technique with click separations of k half-periods. The results obtained by these two methods do not agree and hence are inconsistent with the assumption of linear superposition of CEF's. In all cases, the nulls obtained at longer click separations require smaller intensities of the second click (from a few decibels to more than 25 dB) than would be expected for linear superposition of the CEF's. Furthermore, for a given fiber, the deviation from linearity increases with increased second click delay (delays range from 0.3 to 4 msec). Thus it seems appropriate to term this effect a temporal nonlinearity. These measurements point out a fundamental defect in existing models of the peripheral auditory system, none of which, to the best of our knowledge, include the effect of such a temporal nonlinearity. [This investigation was supported by PHS research grants from the National Institutes of Health.]
Response of Structures to Turbulent Wind
Authors: Davenport A. G.
Published: September 2005

Civil-engineering structures such as long-span suspension bridges, tall towers, skyscrapers, and radio telescopes respond not only statically but also dynamically to natural wind. The dynamic response can be attributed to the following causes acting either separately or together: 1. buffeting by gusts; 2. buffeting by vortices and turbulence shed in the wake of the structure; 3. buffeting by vortices shed by other structures; 4. instability of the galloping or flutter categories. A description is given of the physical processes involved; in particular, the characteristics of the natural wind and the nature of the aerodynamic and mechanical response of structures are described. Approaches to the theoretical description of the problems are outlined, and their degree of success is discussed in the light of experimental results. Some approaches to design are referred to.
Stress Effects on Bilabial Consonants
Authors: Gay Thomas , Harris Katherine S. , Sholes George N.
Published: September 2005

It has been shown that changing the stress from the first to the second syllable of a word will affect the pitch, duration, and vowel color of the syllables. In this study, we will examine the effect of stress changes on the amplitude of the electromyographic signals for /p/, in various positions with respect to the word stress. Preliminary results show some amplitude changes with stress. [Work supported in part by a grant from the National Institute of Dental Research.]
Spherical-Wave Approximation in Horns: Measured and Calculated
Authors: Benade A. H. , Jansson E.
Published: September 2005

Webster's equation for the pressure p may be written ψ″ + [k2 − U(z)]ψ = 0, where ψ = p/(S)12, U(z) = (π/S)⋅(d2/dx2)⋅(S/π)12, and S(z) is the wavefront area at the point z. Theory and experiment indicate that S is almost spherical in flaring horns at low frequencies, thus S(z) > πR2(z) if R is the geometrical radius. Trumpet, trombone, and French horn bells (R≅B/zα, with α⩽1) on 2 m of pipe, are studied. Experiment and calculation agree within 0.3% for the first 10–15 resonance frequencies. Wall losses fit within 1% of the Rayleigh formula α = (1.974 × 10−5)(ω/S)12 cm−1 recalculated with best values for μ, η, κ, etc (Note: Rayleigh's thermometric conductivity is κ/ρcv.) Radiation losses agree well at low frequencies, but as k2 approaches Umax, sphericity fails, and theory first under- and then overestimates the losses. A short inner bell added at the open end, designed to constrain sphericity, improves high-frequency agreement in the manner expected.
Rôle of Oral Cavities in the Support of Tone Production in Wind Instruments
Authors: Stauffer Donald W.
Published: September 2005

Teachers and performers are becoming increasingly aware of the influences of mouth and throat cavities in sound production on wind instruments. Experimenters have tended to overlook or minimize this factor in measuring other variables, particularly in attempts at synthetic tone production in wind instruments. This study documents the actual practice of performers through a study of 35 highly skilled and experienced musicians of The U. S. Navy Band. Embouchure placement, as equated to vowel formations, is related to the ease and quality of sound production in high, middle, and low tones in several reed and brass wind instruments, as determined by individual and group subjective judgment. Results indicate a satisfying consistency of methods among performers; and the necessity for varying the size of mouth cavity for proper artistic tone production in high and low registers. A better understanding of this factor should be pertinent to future experimental situations toward the improvement of wind instruments.
Moisture Susceptibility of Free Violin Plates
Authors: Hutchins Carleen M.
Published: September 2005

Studies of the resonances of free violin plates indicate that changes in the moisture content of the wood can affect the amplitude and other characteristics of the so-called “main tap tone resonance” to a greater or lesser degree, depending on the fine tuning built into the wood of each plate. This fine tuning is predicated on the hypothesis that a violin plate consists of two vibrating areas, coupled in the free back by the wood between the c bouts, and in the top by the bass bar and the wood between the f holes. Tests show that a “well-tuned” plate is much less affected by the addition of one gram of moisture than is a “poorly tuned” one. A possible explanation is offered for the widely known fact that some violins are far more susceptible to moisture changes than others. [Work supported by The Martha Baird Rockefeller Fund for Music, The American Philosophical Society, and C. M. H.]
Some Results Bearing on the Stability of Psychometric Data
Authors: Whitmore John K. , Ermey Harold L. , Williams Paul I.
Published: September 2005

The masking literature shows that the effect of practice in auditory tasks is small; in general, 1000 or fewer trials are sufficient to stabilize performance. Our data, however, show large improvements in performance over as many as 10 000 trials and five months time. In rating the magnitude of a partially masked, short-duration, narrow-band, noise signal, one observer's performance improved by 5.4 dB. Following this rating-scale experiment, the same observer, detecting a sinusoidal signal in a 2AFC task, demonstrated a 3-dB improvement over similar data collected prior to the rating experiment. Although the effects were not quite as large, the behavior of two other observers showed the same trends. [Work supported by National Institute of Mental Health, Naval Ship Systems Command, and National Aeronautics and Space Administration.]
On a Derivation of the Transmission Matrices for the Longitudinal, Torsional, and Bending Vibrations of Families of Tapered Rods
Authors: Pinkney H. F. L. , Basso G. L.
Published: September 2005

The transmission-matrix representation of structural elements finds useful application in the description of multielement systems. Many practical systems use tapered elements for which at present transmission matrices are not readily available. The present paper discusses a particularly useful approach to the derivation of transmission matrices for tapered rods. The transmission-matrix formulation is demonstrated to represent a particularly important fundamental set of the general solution to the governing differential equation. When viewed in this way, the coefficients of the matrix are shown to possess certain properties with respect to each other and the eigenvalue problem. Transmission matrices are derived from known general solutions for certain functional forms of taper and presented in tabular form.
Solution of Eigenvalue Problems Using Conformal Mapping Techniques
Authors: Laura P. A.
Published: September 2005

The study of many problems of importance in modern technology involves the determination of eigenvalues in domains of complicated boundary shape. Some examples can be cited—solid-propellant rocket motors: A simplified mathematical model of a rocket motor is an infinitely long, circular cylinder with a star-shaped perforation; electromagnetic waveguides: Within the last 15 yr the desire for more suitable waveguide shapes has often appeared. Investigation of different modes in waveguides of arbitrary cross section has been conducted by several authors. Flow and heat transfer through noncircular conduits and unsteady flow problems in ducts of arbitrary shape are also problems of great interest in aerospace engineering and biophysics. Conformal mapping techniques have been used by several authors when solving for the eigenvalues of the problem. A brief review of these applications is presented, and fundamental frequencies of vibrating parallelogram plates are computed as application of the method.
On the Unification of Normal-Mode Techniques for Solving Dynamic Elasticity Problems
Authors: Cinelli Gabriel
Published: September 2005

Normal-mode techniques for solving dynamic elasticity problems with inhomogeneous boundary conditions are divided into two categories—namely, displacement (separation of variables, integral transforms) and acceleration (mode acceleration, Mindlin-Goodman, Williams) methods. In general, acceleration methods exhibit superior convergence properties relative to displacement methods. In this study, the solution of the complete linear dynamic elasticity equations of motion with inhomogeneous boundary conditions in an arbitrarily shaped regions is obtained by two methods: (1) a general integral transform technique (based upon Green's extended identity), and (2) a general Mindlin-Goodman process. It is then shown that both of these solutions are actually just different ways of writing the convolution integral in the complex (Laplace transform) domain thereby establishing the unity of all normal mode techniques. Finally, a means for obtaining the quasistatic solution from the displacement (integral transform) solution without the necessity for solving the quasistatic problem, as required in acceleration methods, is then given. [Work supported by the U. S. Atomic Energy Commission.]
Application of Loudspeakers for the Generation of Music
Authors: Locanthi Bart
Published: September 2005

The recent rapid increase in the demand for and application of electronic devices for generating new musical sounds has created a new rôle for the loudspeaker. Heretofore, the primary rôle for the loudspeaker was to act as a reproducer. That is, to reproduce with as little distortion or coloration as possible in a given acoustical environment sound pressures corresponding to the electrical input signal over the frequency range of 35 Hz to 20 kHz. This target performance was considered as having been achieved if the peak reproduced sound-pressure levels could reach 115 to 120 dB. In the rôle as an element in the chain of devices required for the generation of new musical sounds, the loudspeaker is often called upon to add coloration to the “reproduced” signals and to generate sound pressure levels well in excess of 120 dB. Some design problems connected with the design of loudspeakers for this new application will be discussed.
Limitations of Today's Systems for Noise Measurement and Analysis
Authors: Kamperman George W.
Published: September 2005

We have an increasing number of techniques and instruments available for solving noise-measurement problems. The selection of the instrumentation is determined by the over-all measurement objective plus the practical considerations of instrument accuracy, availability, cost, etc. The choice of microphone or vibration pickup is often determined by the nonacoustic portion of the environment. If magnetic-tape recording appears to offer advantages, one should be aware of the limited frequency and dynamic range, the subtle nonlinearity plus crosstalk on multichannel recorders. The acoustic signal may be analyzed in both the frequency and time domains with a variety of signal-detection and readout techniques. The preferred analysis system or technique would present the desired information in its simplest form. The inherent limitations of the total measurement-and-analysis system must be investigated and understood. This is accomplished by careful evaluation of the instrument manufacturer's specifications plus an over-all system checkout and calibration procedure.
Accuracy of Impulse-Noise Measurements
Authors: Rasmussen Gunnar
Published: September 2005

The accuracy one can expect on sound-level readings and the reproducibility obtained for different instrumentation is a function of many inaccuracies. In its present form, the precision sound-level meter is not well suited for measuring impulsive noise. Impulses and short-duration noises present severe problems when they are evaluated, compared, and analyzed. A standard for an instrument enabling impulse-noise measurements has been proposed. Different impulse-noise sources have been measured and analyzed using such an instrument. Readings have been taken for each type of noise on fast-slow and impulse-type meter circuitry as well as with a special circuit for holding the maximum rms value of a pulse with 35-msec rise time. The readings obtained are also evaluated for different weightings through the A, B, C and N networks. The actual wave shapes of the sources have been measured in order to analyze the requirements for the transient response of the microphone, the peak handling ability of the amplifier, and the rectifier circuit of the instrument. Other means of measuring, recording, and analyzing transient noises are briefly discussed.
Color Schlieren as a Quantitative Tool for Acoustic Measurements in Ballistics
Authors: Bixler O. C.
Published: September 2005

Current work in the field of transitional ballistics as described by Bixler et al. [J. Acoust. Soc. Am. 42, 1374(A) (1967)] has led to the development of a technique of measurement that utilizes a color schlieren optical system. This system provides quantitative evaluation of turbulent flow and shock-wave formation, propagation, and scattering. In color schlieren, the second opaque knife edge of the classical Toepler method has been replaced with a tricolor gelatin filter sandwich. This causes the image to be colored according to the sign of the gradient of the density of the compressible fluid being observed. In a typical arrangement, a positive gradient would be colored red, zero gradient green, and negative gradient blue. A unique innovation to the technique is the addition of more color bands to the color sandwich, so that the angular deviation experienced by the image forming rays are color coded. This technique allows a quantitative interpretation of the flow configuration. Photographs obtained using this technique complement the measurements of sound pressure in an examination of the transitional ballistics phase associated with a small weapon.
Amplification and Attenuation of Acoustic Waves in Non-homogeneous Steady Flows
Authors: Salant Richard F. , Toong Tau-Yi
Published: September 2005

An investigation of the interaction between acoustic waves and steady-flow fields was stimulated by the problem of combustion instability in rocket engines. A one-dimensional analysis of traveling acoustic waves in flows of an inviscid, nonconducting, perfect gas, containing mass and heat sources, reveals the existence of a coupling between acoustic waves and non-homogeneous steady-flow fields. This coupling allows energy transport between the wave and the flow field, resulting in either amplification or attenuation of the wave, depending on the gradients of the steady-flow variables and on the propagation direction. Results of experiments with nonuniform velocity fields are in agreement with theoretical predictions. In particular, an air jet discharging into a straight organ pipe and a converging air flow through a tapered pipe, are found to attenuate waves propagating through the pipes. [This work was supported by the U. S. Air Force Office of Scientific Research.]
Transfer of Aircraft Weight to the Surface of the Earth
Authors: Bedard Alfred J. , Cook Richard K.
Published: September 2005

An increased pressure at the earth's surface is to be expected beneath an aircraft in subsonic flight. An infrasonic microphone at the earth's surface was used to measure the dynamic pressures associated with aircraft overflights at various altitudes. The observed measurements of pressure variations are compared with the theoretically expected variations, computed from the Kutta-Joukowsky circulation, which we assume supports the aircraft. These pressures could be comparable to those due to building snow loads for some aircraft flying at low altitudes.
Sporadic Barometric-Pressure Changes and Infrasonic Waves
Authors: Bowman Howard S.
Published: September 2005

In the Washington, D. C., area, sporadic changes in the surface barometric pressure correspond to a special class of slow traveling infrasonic waves having periods between ∼4 and 15 min. These pressure changes apparently account for some local interference encountered in the study of infrasonic wave propagation. The barometric-pressure-associated infrasonic oscillations differ distinctly from waves of the same bandpass recently correlated with the upper altitude tropospheric jet streams. The infrequently occurring large-amplitude low-frequency waves of short duration travel at the earth's surface at speeds much slower than the speed of sound. Also, these waves have no constant direction; and measurements show relation to certain local surface barometric-pressure changes. The particular atmospheric pressure changes are usually related to severe local weather activity such as hailstorms, snowstorms, or thunderstorms. Experimental data are presented that verify the phenomena.
Comparison of Vowel and Consonant Perception
Authors: Griffiths John D.
Published: September 2005

It has been suggested that there may be different mechanisms for vowel and consonant perception. A study of articulation-test-crew responses to minimal feature contrast vowel and consonant “rhyme” tests imbedded in various noises is reported here. Test-crew performance scores for vowels and consonants are compared with respect to noise spectral shape, test exposure, and specific test content by means of confusion matrices. Individual subject-response patterns for vowels and consonants are compared with respect to repeatability, predictability, variations from group means, and individual lingustic experience and history. It is found that perception of vowels relative to consonants varies among individuals, as does the absolute perception of each on a long-term average basis. This variation is not explicable in terms of individual pure-tone audiometric perception, or education, but may be related to individual linguistic experience and history as well as differences in perceptual processes. Occasional very large shifts in individual perception from trial to trial may be due to lapses in higher-order perceptual processes. No correlation was found between test scores and apparent subject fatigue to account for such lapses.
Acoustic Correlates of Place of Articulation for Constants
Authors: Stevens Kenneth N.
Published: September 2005

Theoretical examination of the generation of sound by a constricted acoustic tube that models vocal-tract shapes for consonants suggests that a distinctive acoustic output is obtained for just four (or possibly five) major places of consonant articulation. The sound output corresponding to each of these places of articulation has well-defined attributes that can be described in terms of frequency positions and temporal changes of spectral energy concentrations relative to the spectral characteristics of the adjacent vowel. Several kinds of experimental data are presented in support of these theoretical considerations. These data are derived from studies of the acoustic characteristics of a variety of consonants (primarily English consonants) and from analysis of the characteristics of the sound generated by turbulence in an idealized model of the vocal tract for fricative consonant production, consisting of an acoustic tube with an adjustable constriction. [This work was supported in part by a contract from the U. S. Air Force Cambridge Research Laboratories, Office of Aerospace Research, and in part by a grant from the National Institutes of Health.]
Effect of Pitch Averaging on the Quality of Natural Vowels
Authors: Rosenberg A. E.
Published: September 2005

A pitch synchronous analysis was carried out over the vowel portions of the CVC utterances /hed/, /had/, and /hod/ and the stressed vowel portions of the sentence, “Few thieves are never sent to the jug,” all recorded by a male speaker. The analysis provided formant frequencies, excitation parameters, and an accurate measurement of each pitch period. There were about 40 periods in each of the vowel portions of the CVC utterances and about 20 in each of the stressed vowel portions of the sentence. Each measured period was replaced by a period obtained by averaging adjacent periods over a symmetric “window.” Window sizes of 2, 4, 8, 16, 32, and 64 periods were selected. The vowel portions were then resynthesized with the new periods but maintaining all other parameters of the original analysis. Subjective evaluation was carried out by means of paired comparison tests between utterances with different window sizes, including the natural utterances. The results indicate that a relatively large amount of averaging is necessary to detect a difference in quality from the natural utterances.