bluuebunny/crossref_metadata_2025 huggingface dataset:
Some Solutions to a Mixed-Boundary-Value Problem
Authors: Solomon L. P. , Schryer N.
Published: October 2005

Most problems in wave propagation are characterized by boundary conditions of only one type, e.g., vanishing normal-velocity components in the case of a resonant cavity. The problem investigated by D. L. Lansing, C. E. Watkins, and G. T. Kantarges, “Oscillating Pressures within a Cylindrical Chamber that Has a Circular Piston in One End Wall” [J. Acoust. Soc. Amer. 36, 2222–2232 (1964)] is also of that type. A problem in the same vein, but with a pressure-release surface somewhere on the cylinder surface appears to be a logical and simple extension, but this is not the case, since the boundary conditions become mixed. Numerical techniques have been employed to obtain solutions to the problem of a cylinder with a piston of smaller radius than the cylinder radius at one end, with the shoulder having either a vanishing velocity condition or pressure-release condition imposed. Cases where the piston is inserted in the cylinder are also presented. Comparisons are made to the analytical solutions attained by Lansing et al.
Wave Propagation in an Infinite Elastic Plate in Contact with an Inviscid Liquid Layer
Authors: Walter W. W. , Anderson G. L.
Published: October 2005

The dispersion relation for straight-crested waves in an isotropic plate in a state of plane strain that is covered by a layer of an incompressible liquid is derived and investigated in the limits of very long wavelengths (thickness-stretch vibrations of the plate-liquid system) and of very short wavelengths (surface waves and the solid-liquid interface). In the case of surface waves, there are two dispersive modes, one predominantly elastic (analogous to Rayleigh waves) and the other essentially fluid, and in the thickness-stretch case, there are an infinite number of essentially elastic modes and one fluid mode. An approximate version of the dispersion relation valid for arbitrary wavelength is obtained by using two nonclassical plate theories to account for the extensional and flexural deformations of the plate. This relation gives rise to five modes on the real branch, which are identified as being thickness-stretch, thickness-shear, flexural, extensional, and fluid in character, and three modes on the imaginary branch, namely, flexure, thickness-shear, and thickness-stretch. Two of the five cutoff frequencies are modified by the presence of the liquid layer. A variety of numerical results are presented in graphical form.
Sound Radiated by Beam-Stiffened Plate
Authors: Feit D. , Saurenman H.
Published: October 2005

A common structural element in aerospace and marine vehicle design consists of a relatively thin skin supported by a framework of attached beams. The present study treats this configuration as a thin elastic plate with one or more parallel beams attached. In order to find the sound pressure radiated by such a plate, the dynamic response of the plate beam system is first computed following the procedure of Lamb [J. Acoust. Soc. Amer. 33, 628–633 (1961)]. The two-dimensional Fourier transform of the response thus obtained is used to calculate the radiated sound pressure. The resulting pressure field is then used as an indirect means of finding the significant interframe resonances. [The work presented here was supported by the Office of Naval Research Structural Mechanics Branch.]
Comparison between Theory and Experiment for a Mechanical Luneberg Lens
Authors: Brigham G. A.
Published: October 2005

The first mechanical Luneberg lens was built and tested by Toulis in the latter half of the previous decade. Using the wave theory [C. A. Boyles, J. Acoust. Soc. Amer. 43, 709 (1968); G. E. Lord, J. Acoust. Soc. Amer. 43, 1177(L) (1968); G. A. Brigham, Int. Congr. Acoust., 6th, Tokyo (August 1968)] for a Luneberg lens with a monopole feed close to the nearfield, we have computed, for Toulis' test conditions, the polar response of an ideal lens. The comparison is within 4 dB throughout the 180° scanning pattern. Visual observation of Toulis' compliant-tube lens reveals that the actual fabrication would produce some cylindrical effects in the lens. When allowances are made for this, the theory and experiment are observed to be within 2 dB of each other in the full pattern over the 2 oct test bandwidth.
Age and Sex Differences in Speech under Delayed Auditory Feedback
Authors: Buxton Lawrence F.
Published: October 2005

A developmental study of speech under delayed auditory feedback (DAF) indicated that: (1) the delay in auditory feedback producing maximal disruption of speech varied significantly with the age of the speaker. The delay in auditory feedback producing maximal speech disruption was 0.60 sec for children aged 4–6; 0.6 sec. for children aged 7–9; 0.2 sec for children aged 10–12; 0.2 sec for adults aged 20–26; and 0.4 sec for adults aged 60–81; (2) children aged 4 to 6 were more affected by DAF than adults, regardless of the delay condition; (3) the delay that produced maximal speech disruption did not become shorter with the increasing age of the subject, thus altering a conclusion reached by MacKay [D. G. MacKay, J. Acoust. Soc. Amer. 43, 811–821 (1968)]; (4) the critical interval of delay, which produced maximal disruption of speech, did not vary significantly for males and females within a given age group; (5) a subject's maximum rate of speech correlated significantly with the amount of stuttering produced under DAF. The slower a subject's maximum rate of speech, the more he tended to stutter under DAF.
Measurement of Community Noise
Authors: Donley Ray
Published: October 2005

A draft proposal for a uniform method of measuring community noise, developed by the USASI S3-50 Working Group, presents a method for obtaining and analyzing community noise data to serve as a basis for noise-control codes and engineering-design goals. The various procedures and requirements are discussed along with the reasoning on which the proposed standard is based.
NBS Mobile Acoustical Laboratory
Authors: Winzer George E.
Published: October 2005

In response to the need for research and study of the acoustical problems of urban environments, a mobile laboratory was designed to provide field measurement instrumental capabilities of the quality usually associated only with fixed acoustical laboratories. The facility provides for the field study of the actual acoustical performance of sound-isolating partitions and floor-ceiling assemblies, structureborne sound transmission generated by impacts, vibrating plumbing and electromechanical equipment as installed, and for acquisition of data toward determining relationships between field and laboratory measurement results. Most measurements are conducted from the mobile unit with only loudspeakers and microphones located remotely from the laboratory. For high-rise buildings and situations where lengthy cables are involved, a measurement subsystem is removed and transported readily to the site. Data may be reduced and analyzed at the field site or stored for later reduction and analysis. Some considerations and decisions involved in the preparation of specifications are discussed.
Scattering by Spherically Symmetric Inhomogeneities
Authors: Frisk George V. , DeSanto John A.
Published: October 2005

The Jost function formulation of quantum scattering theory is applied to classical problems involving the scattering of a scalar plane wave by a medium in which the velocity is a function only of the spherical radial coordinate. This technique is used to solve the radial differential equation for scattering from a constant spherical inhomogeneity. The radial equation can be converted into an integral equation incorporating the Jost boundary conditions. The l = 0 partial wave integral equation for a constant inhomogeneity is solved using an iteration procedure (the first two iterations are considered). The Jost function and l = 0 cross section σ0 are plotted as a function of kR1, where k is the wavenumber in the surrounding medium and R1 is the sphere radius. The iterative technique is good for long wavelengths (kR1≪1) and any ratio of wavenumbers in the scattering and surrounding media. For shorter wavelengths and small ratio of wavenumbers (e.g., k1/k = 1.1, where k1 is the wavenumber in the scattering medium), it gives a good approximation to σ0 for the entire range of kR1 considered (0⩽kR1⩽2π). For shorter wavelengths and larger ratio of wavenumbers (e.g., k1/k = 1.5, 2.0), it gives a good approximation to σ0 out to approximately kR1 = 3π/4. More general problems using this method are also discussed.
Interaction between Acoustic Modes in Extended Media and between Components of the Brillouin Spectrum of Scattered Light
Authors: Piercy J. E.
Published: October 2005

Much of the theory of acoustics and also of the Brillouin scattering of light has been based on the Stokes-Kirchoff method of solving the linearized differential equations of fluid dynamics; modes of propagation or decay of sound and components of the Brillouin spectrum are identified by roots of a secular equation. It has then been assumed that the general solution is the sum of the particular solutions, making the modes normal and the components separable. This assumption is shown to be not correct, in general, for a given real value of the propagation constant, and errors that arise through its use in the analysis of Brillouin spectra of relaxing fluids are examined. Different sets of approximate normal coordinates are required for the adequate description of spectra, depending on the ratio of the frequencies of relaxation and acoustic resonance.
Acoustical Manifestations of Emotional Speech
Authors: Williams C. E. , Stevens K. N. , Hecker M. H. L.
Published: October 2005

High-quality tape recordings were obtained of professional method actors reading the dialogue of a short scenario especially written for determining those parameters in the speech signal that reflect a speaker's emotions. Excerpts from the recordings were subjected to both quantitative and qualitative analyses. Several acoustical manifestations were noted for the various emotions portrayed by the actors. Some of these acoustical correlates are measurable quantities that are amenable to extraction from the speech signal by automatic means; others represent characteristics of patterns that can be observed and categorized by visual examination of sound spectrograms. Some of the quantitative results found support the results of previous studies. Other findings, particularly those describing qualitative effects observed on spectrographic patterns, have not been reported previously.
Real-Time Hybrid Sound and Vibration Analyzer
Authors: Lapointe James A. , Kundert Warren R. , Partridge Gordon R.
Published: October 2005

The general Radio type 1921 real-time analyzer employs a combination of analog and digital techniques for determining the true rms levels within 13-oct bands. Samples of a filtered input signal are taken over spans of time varying from 18 sec to 32 sec at the operator's discretion. Each sample is converted to a digital value by an analog-to-digital converter. The resulting binary number is squared and added to any preexisting values in a memory bank. The memory contents at the end of each measurement represent a sum of the squares in digital form. This sum is decoded through a “hard-wired” routine to give a level in decibels. Dynamic range of 60 dB (plus a 10-dB crest-factor reserve at full scale) is provided. Frequency range depends on the analog filters selected; various combinations from 3.15 Hz to 80 kHz are available in standard instruments. Detector accuracy is ±1 dB for all combinations of amplitude and frequency; in most cases, it is ±0.5 dB. Answers are displayed by both analog and digital methods: a voltage proportional to level and a voltage proportional to band number are provided for deflecting an oscilloscope; digital results are shown on Nixie tubes, and made available as binary-coded-decimal voltages to operate computers or printers. Results are equally good with signals of all types: noise, sine waves, tone bursts, and AM and FM signals.
Mathematical Model for the Class V Flextensional Underwater Acoustic Transducer
Authors: Nelson R. A. , Royster L. H. , Boone J. N.
Published: October 2005

A mathematical model is developed for both the disk and shell of the Class V flextensional underwater acoustic transducer. The disk is approximated by a thin piezoelectric disk with an arbitrary impedance on the boundary. Electrical impedance and coupling coefficient are developed for this case. The coupling coefficient is also developed for a springlike boundary condition around the disk. The shell is approximated by a discrete set of equations. These equations of motion are derived for both the guided-pinned and guided-clamped boundary conditions. The results are then set up in matrix form and solved. [Work sponsored by the Office of Naval Research, Acoustics Programs, and by the Naval Underwater Sound Laboratory.]
Vacuum Maintenance in Image Tubes
Authors: Turner William R.
Published: October 2005

The conflict between the vacuum requirements for electron-beam tubes and the physical characteristics of piezoelectric conversion materials has restricted most ultrasonic image converters in current use to continuous pumping, or if sealed, to limited beam currents. This paper reviews some of these conflicts encountered during the development of a sealed high-conductance quartz image converter. The vacuum problem is described in terms of the pressure level allowable, the gas sources within a tube, and the gas evolution produced by temperature changes and electron bombardment. Measurements disclose gas evolution rates proportional to the 37th power of the absolute temperature, and similar effects for electron bombardment. Consequently, unbaked tubes must be continuously pumped at high rates, and the potential life of a sealed tube is extended as the bakeout temperature during vacuum processing is raised. However, the properties of some piezoelectric materials may prelude high bakeout temperature. The anisotropic thermal expansion characteristics of crystalline quartz was an initial problem, but has been overcome through the use of a compliant seal. Barium titanate is susceptible to reduction when heated in vacuum at high temperatures. Any new ultrasonic material considered for a sealed image tube is suspect until its reaction to the rigors of vacuum processing is fully known.
Linear Wave-Vector Dispersion of the Shear-Wave Phase Velocity in α Quartz
Authors: Pine Alan S.
Published: October 2005

Certain optically active crystals may exhibit linear wave-vector dispersion in the transverse acoustic branches. Along the c axis in α quartz, the two linearly polarized transverse modes have equal velocities in the limit qz → 0. This degeneracy is lifted proportional to wavevector at finite frequencies, and the normal modes are circularly polarized. The phase velocity difference leads to the phenomenon of acoustical activity [D. L. Portigal and E. Burstein, Phys. Rev. 170, 673 (1968)] in which the displacement vector of a linearly polarized shear wave rotates around the propagation direction. We have observed a ∼1% velocity difference of two ∼30 GHz shear waves along the c axis in α quartz by high-resolution backward Brillouin scattering. The polarization of the shear waves is demonstrated by scattering with circularly polarized light. 180° scattering is employed to obtain the maximum wave-vector transfer together with adequate spectral and angular resolution. Backscattering from transverse waves is observable in a quartz (but not in higher symmetry crystals), because of an allowed Pockel's tensor component, p14. The magnitude of the velocity splitting in α quartz may be extrapolated from recent neutron scattering measurements. [This work was sponsored by the Department of the Air Force.]
Introduction to the Consonant-Recognition Test
Authors: Preusse John W.
Published: October 2005

A test of speech intelligibility called the Consonant Recognition Test has been developed and evaluated. Designed to use human subjects in conjunction with a digital computer as a precision laboratory tool for diagnostic analysis of speech communication systems, this test appears to combine the attributes of simplicity, efficiency of testing, sensitivity, and diagnostic ability to an extent not previously attained by intelligibility tests. To minimize the effects of speaker differences and to permit one to use conveniently a large number of speakers, nine speakers were rotated or “multiplexed” in the recorded version of the lists so that each list contained a sample of the nine voices. Experiments comparing the consonant recognition test to the Fairbanks rhyme test have demonstrated that the consonant recognition test requires less than 75% of the time for test administration and is about 18% more sensitive, while still providing an extensive diagnostic analysis of the systems under evaluation.
Signal-to-Noise Level as a Predictor of Speech Transmission Quality
Authors: Sen Tapas K. , Carroll J. Douglas
Published: October 2005

Signal-to-noise level may be generalized to the form logSa/Nb, where S and N are respectively signal and noise values expressed in power units. As usually defined, the exponents a and b both assume values of +1. This paper presents some data analyses that were performed to study the optimum value of the ratio a/b as a predictor of speech transmission quality. In two separate experiments using simulated and normal telephone circuits, subjects rated the transmission quality in the presence of interference. In the first experiment, the interfering variables were crosstalk, speech, and noise. In the experiment, the variables were noise and loss of speech energy. A factor analysis of the rating data indicated that signal-to-noise level was the dominant factor. Both canonical correlation and multiple regression analyses were performed to find the optimum value of the ratio a/b as mentioned above. In all cases, it was found that a/b > 1 was a better predictor of transmission quality than a/b = 1.
Concepts and Acoustics of Open-Plan Offices and Schools
Authors: Veneklasen Paul S. , Hyde Jerald R.
Published: October 2005

The present popularity of open planning for offices and schools is surprising in terms of supposedly establishing criteria for privacy and sound isolation. It is very difficult to approach these criteria in an “open” plan. Precise model measurements define attainable steps in sound isolation as one uses extreme absorption on available surfaces, and then introduces functional obstacles as sound barriers, partial partitions, and even specific acoustical reflectors to improve the ratio of desired to objectionable communication. Much can be accomplished with transparent partitions to preserve visual openness and improve isolation. The magnitude of background noise to mask residual unwanted communication and noise exceeds generally tolerable levels and suggests use of programmed familiar sounds selected for acceptability and without distraction. Economy will not be a feature of the acoustically acceptable open plan. Knowledgeable school planners stress flexibility more than openness; hence, folding and readily movable partitioning may flourish. Since architects generally will not respect the acoustical sophistication, nor will owners like the cost, the alternative will probably be either passing of the fad or evolution of consideration and discretion in voice communication.
Ten Years of Experience with Several Score Open-Type Classroom Schools
Authors: Fitzroy Dariel
Published: October 2005

After completing a study of the data acquired as a result of a national survey of “acoustically bizarre” schools, sponsored by the Educational Facilities Laboratories, coupled with several years experience in being responsible for the acoustical design, and subsequent testing of an extended number of similar schools, certain conclusions and opinions have been derived. These are based on the opinions of the teachers and administrators actually using these facilities. Instrument measurements do not seem to be wholly conclusive. Several ideas will be advanced that may explain the apparent anachronisms between our conventional ideas, from the viewpoint of acousticians, as contrasted with actual teaching experience.
Acoustical Problems in Open-Plan Spaces
Authors: Hirtle P. W. , Schultz T. J.
Published: October 2005

Adequate speech privacy and communication are two of the most important acoustical goals in offices; but in open-plan spaces, these two are in conflict: The more you have of one, the less you have of the other. Laboratory studies and evaluation of field situations have led to the development of an analysis technique based on the articulation index concept which takes into account: speech effort, room characteristics and treatment, desk spacing, location and size of acoustical barriers, background noise levels and spectrum, and the degree of privacy or intelligibility required. Particular attention is given to the requirements for ceiling absorption. Calculation techniques are presented that permit a simple analysis, and comparisons between predicted and observed subjective reactions are made. Although the amount of data is limited, it appears that useful predictions relative to speech privacy and speech communication in open-plan spaces can be made.
Application of the Acoustically Terminated Tube for the Measurement of Horn-Loudspeaker-Driver Characteristics
Authors: Locanthi B. N. , Sepmeyer L. W.
Published: October 2005

The application and limitations of the acoustically terminated small-diameter tube and calibrated pressure microphone to the measurement of horn-loudspeaker-driver characteristics are discussed. Terminated-tube measurement data obtained from a loudspeaker-horn driver are presented showing acoustic power output as a function of frequency, harmonic distortion as a function of frequency, intermodulation distortion as a function of frequency and acoustic power output, and one-third octave band pink-noise distortion. Measurement data taken from a horn driver coupled to a short horn operating in an anechoic environment as well as a diffuse field environment will be presented and correlated with the data obtained from terminated tube-measurements of the horn driver alone. This work was performed as a result of the proposals from Writing Groups S1-47 and IEC TC 29B. The one-third-octave pink-noise distortion test was proposed by the Russian delegate to TC 29B, Morris G. Belkin.
Tone-Burst Technique of Sound Absorption Measurement
Authors: Powell John G. , Van Houten John J.
Published: October 2005

Sinusoidal tone bursts are generated by an electrodynamic transducer at frequencies from 500 to 10 000 Hz for measurement of material absorptive characteristics. The transducer is placed at one end of a tube and the sample located at the other. Pulse amplitude of the reflected tone burst provides a measure of the normal incidence absorption coefficient of the material. Wave amplitudes are generated that are considerably greater than those achieved on a steady-state basis. Excellent agreement is found between impedance tube measurements and the tone burst technique. Nonlinear absorptive characteristics of material samples have been identified at sound pressure levels approaching 160 dB (re 0.0002 dyn/cm2). [Work supported by NASA, Langley Research Center.]
Acoustic Rays in Two-Dimensional Rotating Flows
Authors: Salant Richard F.
Published: October 2005

The differential equation of acoustic rays in two-dimensional rotating flows is derived and is integrated for the cases of rigid body rotation and the potential vortex, with a point acoustic source. In the case of rigid body rotation, the rays are bent in the direction of rotation, resulting in defocusing on the side of the acoustic source near the center of rotation and focusing on the opposite side. In the case of the potential vortex, a number of rays are trapped by the vortex and spiral towards the center. Other rays at first appear to be trapped, but then reach a turning point and leave the vortex. These rays are substantially deflected and defocused. In addition, with a circulation corresponding to a Mach number of 0.5 at the acoustic source, a caustic is formed. However, with one-half that circulation, the caustic does not appear.
On the Effects of Viscosity on Sound Propagating in a Moving Fluid through Cylindrical Ducts
Authors: Rentzepis G. M.
Published: October 2005

In this paper, the effects of the presence of viscosity in a fluid flowing through a cylindrical duct, on the sound propagation and attenuation is discussed. The field equations are obtained from the linearized variational equations of the conservation equations. Solutions of viscous case for various flow profiles are obtained and the results are compared with the inviscid and the stationary cases. The effects of shear flow coupled with viscosity are discussed and compared with the case of flow bounded by two infinite planes.
Tracking of Articulatory Movements by Means of a Computer Controlled X-Ray Microbeam
Authors: Fujimura O. , Ishida H. , Kiritani S.
Published: October 2005

A special x-ray generator produces a fine beam of x-rays that can be deflected with very fast response by computer control. A high sensitivity scintillation counter essentially counts the number of the outcoming x-ray photons and feed the detected beam intensity into the computer. Small pellets are placed on selected parts of articulatory organs and their movements are tracked by this method, the result being displayed by an oscilloscope. The radiation dose is minimized by giving x-ray exposures under program control only when and where necessary for deriving immediately useful data. The first prototype system has been assembled and preliminary experiments are being performed for establishing the experimental method. Some computer programs for pellet tracking have been written. With the present x-ray generator system for preliminary studies, it is shown that a lead pellet of 1 mm in diameter can be tracked at a rate of 400 frames/sec. A similar x-ray generator with a higher acceleration voltage is being designed for optimal performance in articulatory data collection. [This work is supported in part by PHS Research Grants from the National Institute of Neurological Diseases and Stroke, U. S. A.]
Loss in the Cochlear Microphonic as a Function of Constant Duty Cycle and Varying Repetition Rate
Authors: Price G. Richard
Published: October 2005

As part of a program designed to investigate the mechanisms of hearing loss as a function of exposure to intense sound, 50 anesthetized cats were exposed to a 5.0-kHz tone, and loss in CM (cochlear microphonic) sensitivity was monitored. During exposure, the tones were on 20% of the time and were repeated every 50 msec, 500 msec, 5 sec, or 5 min. The level of the tone was always set 30 dB above whatever level was necessary to produce a maximum in CM at 5.0 kHz (mean exposure SPL was 133 dB). Losses in CM sensitivity after 250 min (50 min of “on” time) were large (55 or 60 dB) and with one exception were not significantly different for the different exposure periods. The exception was that half the animals exposed on the 5-min cycle showed the same large losses as the other groups and half showed significantly smaller losses.
Auditory Response to the Acoustic Impulse from an Air-Bag Crash Protection System
Authors: Nixon Charles W.
Published: October 2005

The potential acoustic hazard of an impulsive noise generated inside an automobile by inflation of a rapidly expanding air-bag personal crash protection system was evaluated. Widespread use of this system in vehicles would result in an average exposure of about one impulse per person over a lifetime. The acoustic impulse is characterized by a median duration of 21 msec, median rise time of 5 msec and median peak pressure level of 168 dB. Ninety-one volunteers experienced the single intense impulse without ear protection and their pre- and postexposure audiometric and otologic examinations provided measures of auditory responses. Otologic effects on the drum membrane were negative. No discomfort or aural pain was reported. About 50% of the subjects and 35% of the ears experienced some temporary threshold shift with 65% of the ears recovering within 24 h. Many subjects reported short duration tinnitus. Results indicate that the impulsive noise is very loud; however, the probability of irreversible harm to the auditory systems of vehicle occupants may be considered to be extremely small.
Some Experience with the Computerized Noise Monitoring System at Stuttgart Airport
Authors: Straessner P. M. , Blaesser H.
Published: October 2005

This new aircraft noise monitoring system has proved to be successful in noise abatement. A symmetrical arrangement of the outdoor noise monitoring terminals about the axis of the main runway allows monitoring of specially developed flight patterns and techniques. An additional terminal close to the runway checks the effects of reverse thrust, which should be used only if absolutely necessary. The monthly averaged noise exposure index gives an accurate indication of the noise conditions at the terminal locations.
Vehicle Warning Devices—Necessity versus Nuisance
Authors: Ortega Jose C.
Published: October 2005

Acoustical warning devices may be essential for public safety and a nuisance to nearby residents. The question arises, how much reduction in the level of the warning device can be tolerated before it loses its value as a warning signal? This paper presents the results of a short study related to possible reduction in acoustic level of a Diesel-engine horn. The important variables that were studied included (a) level and spectral content of the horn signal; (b) distance between Diesel engine and the driver of an automobile approaching a railroad crossing; (c) whether the automobile windows are open or closed; (d) the level of the masking sound the driver is experiencing. Use is made of the critical-bandwidth concept to obtain allowable Diesel-engine horn sound reductions for several automobile window configurations and three types of masking sounds.
Aerospace Noise Sources
Authors: Hubbard Harvey H.
Published: October 2005

The physical characteristics of noises associated with various aircraft and spacecraft and which cause dynamic loadings on either flight- or building-type structures are summarized. These noise loadings are characterized according to the manner in which they are generated, as well as their temporal and spectral characteristics.
Determination of the Pressure Cross Correlation on a Cylindrical Body Due to Rocket Exhaust Noise
Authors: Jones Jess H. , Schutzenhofer Luke , Guest Stanley H. , Wilhold Gilbert A.
Published: October 2005

A description is presented of an experimental program to determine the pressure cross-spectral density distribution on a cylindrical body resulting from a hot rocket exhaust. It is shown how the pressure cross-spectral density can be applied to determine the response of a continuous linear structure. The main effort is to describe the basic objectives of the experimental program, the experimental facilities, the data-acquisition system, and calibration procedures. In regions on the cylindrical body where the random pressure field can be considered homogeneous in space, a simplified model of the longitudinal pressure cross spectral density distribution is presented.
Turbulent-Boundary-Layer Pressure Fluctuations over Rough Walls
Authors: Blake William K.
Published: October 2005

The effect of distributed wall roughness on surface pressure fluctuations has been measured with very small (relative to a boundary-layer displacement thickness) “pinhole” microphones. Measurements were also made on smooth walls for comparison. The rough-wall rms pressure levels increase over the smooth-wall value in approximate proportion to the increase in wall shear by the roughness. In addition, intermediate- and high-frequency pressure levels are predominantly determined by roughness size, whereas low-frequency levels are influenced by roughness separation and by boundary-layer displacement thickness. Cross-spectral density measurements made with 5-Hz bandwidth filters disclose lower rough wall phase speeds. The pressure-field coherence loss is higher; pressure eddies of any frequency lose their coherence over rough walls in one-third to one-half the streamwise distance over smooth walls. Very low phase speeds at low frequencies were measured over both smooth and rough walls. The broad-band space-time decay rates are slightly higher, and the convection velocities are lower for rough than smooth walls. [This work was performed while the author was at the Massachusetts Institute of Technology; it was sponsored by the Naval Ship Systems Command, General Hydromechanics Research Program.]
Artificial Intonation
Authors: Vanderslice Ralph , Rand T.
Published: October 2005

Artificial intonation refers to means for imposing controlled changes on certain prosodic parameters of natural human speech by computer. In particular, fundamental frequency and local rate can be modified by pitch-synchronous time-domain operations on digitized speech waveforms. Pitch is raised without altering formants by deleting consecutive sample values from each pitch period in playback, or lowered by reiterating a single sample value in each pitch period for the length of time by which the interpulse interval is to be increased. Synthetic intonation offers advantages over conventional speech synthesis by art (convenience) and by rule (quality and intelligibility) for basic research into the prosodemic structure of languages—where typically the input is spoken at a constant f0 (aside from articulatory perturbations) and the prosodic contours imposed entirely by the program—and such applications as a word-storage reading machine, normalizing psycholinguistic stimuli, and improving second-language pedagogy.
Acoustical Properties of Word Boundaries in English
Authors: Coker C. H. , Umeda N.
Published: October 2005

From empirical studies to adjust the durations of phonemes in rule-synthesized speech, it is found that the durations of phonemes at the word junctures separate into three clearly defined categories. These duration classes are taken to define three types of word boundary: weak, intermediate, and strong. The weak boundary occurs between monosyllabic functional words such as “in-the, is-the”, and “it-is.” Consonant durations are quite the same as inside polysyllabic words. The strong boundary occurs between major content words (roughly, words that would be capitalized in a title). It is characterized by quite-lengthened single consonants and medium-duration initial consonants of clusters. If the initial syllable of the word following the juncture carries primary stress, initial plosives will have stronger bursts and increased aspiration. Initial primary-stressed vowels will have an unaspirated devoiced portion resembling a glottal stop. The intermediate boundary occurs between compound words and at junctures between content words and certain semifunctional words, like “such,” “there,” “other,” and “most.” Changes of speech rate do not strongly affect definitions of the strong and intermediate boundaries. As rate increases, weak boundaries selectively replace strong ones, often without progression through the intermediate level.
Toward Rules for Natural Prosodic Features in American English
Authors: Browman C. P. , Coker C. H. , Umeda N.
Published: October 2005

The main body of a set of rules, which assign pitch and timing for the synthesis of reasonably fluent and natural-sounding speech, is described. The rules predict vowel durations with proper regard for the variation of “prevocalic” lengthening with over-all context. Rising, falling and rise-fall intonations are assigned quite plausibly in most cases. Three values of word boundary (juncture) are generated. At present, boundaries for careful but fluent speech are assigned quite well by simple rules. Possibilities for changing the speech rate may be incorporated without great difficulties. The rules are applied in three levels. The first level requires a limited syntax analysis. [Teranishi and Umeda, Int. Congr. Acoust., 6th, Tokyo (1968).] At this level, breath-group boundaries and certain other syntactic features are marked. In the second level, word boundaries not coinciding with breath-group boundaries are marked. In the final level, consonant durations and detailed pitch control are generated. Analysis at the second and last level require limited context only. Word boundaries depend on attributes of adjacent words passed down from the previous level. Vowel and consonant durations depend on information extending only up to the adjacent vowels.
Lateralization and Loudness Summation
Authors: Chaves John F.
Published: October 2005

Subjects judged the loudness of a two-tone complex when presented alone to the left ear and when presented simultaneously with a single tone in the right ear. The purpose of the contralateral tone, whose frequency was the same as one of the components of the complex, was to shift the location of that component to the right ear. The components were geometrically centered at 500, 1000, 2000, and 4000 Hz and were presented at loudness levels of 30 and 60 phons. The loudness of the complex increased as the frequency separation of the components increased from one to eight critical bands, both when the complex was presented alone and when one of the components was shifted to the right ear. However, loudness summation was reduced when one of the components was shifted to the right ear. Moreover, this reduction in loudness was greater when the lower-frequency component was shifted than when the higher-frequency component was shifted. These data support the notion that loudness summation occurs peripherally in the auditory nervous system. [Supported by a Research Fellowship from the National Aeronautics and Space Administration.]
Ultrasonic Relaxation in Aqueous Solutions of Tetraalkyl Ammonium Salts
Authors: Marchessault Joseph , Broadhead John , Yeager Ernest
Published: October 2005

Ultrasonic-absorption measurements have been made with send-receive pulse techniques in aqueous solutions of tetrabutyl ammonium bromide as a function of frequency (up to 500 MHz), concentration, pressure (up to 2 kbar), and temperature. A double-Carstensen cell system in a high-pressure vessel has been used for the determination of the pressure dependence at and below 50 MHz. The results give evidence of two relaxation frequencies, one above 300 MHz for concentrations of 0.6 M or greater at 25°C and 1 atm, and the second below 50 MHz. The molecular absorption cross section increases abnormally fast with increasing concentration above 1 M, particularly at lower frequencies, suggesting that a large number of solvent molecules are involved with the solute in the low-frequency relaxation process. Various mechanisms are considered and predictions based thereon compared with experiment. The high-frequency relaxation is attributed to a second-order diffusion controlled-association process. [Research partially supported by the Office of Saline Water and the Office of Naval Research.]
Specularly Reflected Pulses from Soft Cylinders Using the Creeping-Wave Formulation of Scattering Theory
Authors: Rudgers Anthony J. , Überall H.
Published: October 2005

The creeping-wave formulation of scattering theory shows that for an acoustically soft body, the scattered field due to an incident plane-wave pulse is composed of two component pulses. The creeping-wave-type component pulse, resulting from waves traveling circumferentially around a soft cylinder, has been previously analyzed. This paper deals with the other component pulse, the one produced by specular reflection. The rationale is presented of a mathematical and numerical development by which the specularly reflected pulseform has been found at points in the farfield of the cylinder. The incident pulseform used is a modulated δ function. The specularly reflected pulseform resulting from this incident pulse is a δ function possessing a tail. The computed specular pulseform has the characteristics expected for a pulse originating by specular reflection in the cylindrical scattering geometry. Reflected pulseforms for other incident pulseforms may be obtained from the δ function result using the convolution integral.
Classification of Axisymmetrica Apertures
Authors: Brigham G. A.
Published: October 2005

A large class of well-known axisymmertic scanning devices such as paraboloidal reflectors, uniform circular pistons, spherical Luneberg lenses, etc., may be compared because they all have Fraunhoffer patterns equivalent to those produced by shaded, circular, plane arrays, i.e., the devices all collimate over a plane circular aperture. The scanning pattern is a normalized Bessel function Δν(z) with ν the order and z = CIRCUMFERENCE/WAVELENGTH × SINE OF THE ANGLE FROM THE APERTURE AXIS. All orders (integral and nonintegral) from ν = 0 to ν → ∞ have been explored and such relevant parameters as sidelobe, beamwidth, and directive-gain versus order have been computed and are shown. The calculation of directive index leads to the algebraic proof that the uniform piston has the best directive gain. For very large apertures, a phased spherical volume array (ν =) and phased spherical surface array (ν = 12) may be included in the general classification.
Temporal Patterns of Rate Alterations in Oral Reading
Authors: Lass Norman J. , Deem Jodelle F.
Published: October 2005

The purpose of this investigation was to determine if there exists a typical temporal pattern or set of patterns employed by speakers in their attempts to increase and decrease their normal oral reading rates. Twelve subjects read a standard prose passage 10 times in each of six experimental sessions: the first three sessions consisted of readings at normal rate (standard task); Session 4 involved attempts to read at one-half as fast as normal (fractionation task); in Session 5, subjects attempted to read at twice as fast as normal (multiplication task); the sixth session consisted of a combination of fractionation and multiplication tasks. The recorded readings of all subjects were analyzed by means of a high-speed power level recorder. The following temporal measures were obtained from the power level tracings: total time (in seconds), speech time (in seconds), intrasentence pause time (in seconds), intersentence pause time (in seconds), number of intrasentence pauses, number of intersentence pauses, speech-time ratio, pause-time ratio, and over-all rate (words per second). Results indicate that despite differences between subjects involving amount of change exhibited in temporal measures, there emerges an obvious temporal pattern in all subject's attempts to increase and decrease their normal reading rates. [Research supported by the National Institute of Neurological Diseases and Blindness.]
Multidimensional Scaling of 12 American English Vowels
Authors: Singh S. , Woods D.
Published: October 2005

Twelve isolated, sustained American English vowels were magnetically recorded, and presented in pairs to 45 English speaking students for similarity judgments on a seven-point scale. “One” on the scale indicated greatest similarity, “seven” greatest dissimilarity. The individual results were pooled in a 66-cell matrix with one value for each unordered pair of vowel. This matrix was submitted to a multidimensional scaling (MDS: Shepard and Kruskal) which placed the vowels in configurations of two through five dimensions. The three dimensional configuration was rotated by a computer technique (Schoenemann and Carroll) to axes which were interpreted by the phonetic features of tongue height, tongue advancement, and retroflex. The same data were reprocessed after the elimination of all pairs with the vowel (American pronunciation of ir in bird). Good results were obtained for the 11 remaining vowels in two dimensions rotated for the features of tongue height and tongue advancement. The two-dimensional graph of the perceptual structure of 11 vowels shows marked similarity to the traditional articulatory chart with the same features. [This work was supported by a grant from the National Institutes of Health, U. S. Department of Health, Education, and Welfare.]
Estimate of the Inherent Channel Capacity of the Ear
Authors: Corliss E. L. R.
Published: October 2005

The growth of intelligibility of speech stimuli as a function of sound level above threshold can be computed from the “circuit parameters” of the hearing mechanism by applying Shannon's concepts of channel capacity, equivocation, and “bit rate.” The calculation starts from the “least count” derived from data on hearing by the equations for a circuit-type mechanism that represents the function of the ear. By considering the rate at which phonemes are produced in speaking, and the number of “distinctive features” characterizing the phonemes, intelligibility functions can be predicted that agree fairly closely with random word and random syllable intelligibility data obtained experimentally. This agreement shows that the listener need recognize no more than a single distinctive feature of each phoneme to display the recognition functions that have been observed. The duration of correlated utterance may be considered the “code length” that has the effect of lowering the channel capacity required for polysyllabic utterances as opposed to monosyllables. Evidently, contextural effects are not prominent in the intelligibility of random-word lists; the hearing process involved is primarily recognition of groups of sounds; meaning is secondary.
Surface Preparation and Scanning Electron Microscopy of the Cochlea
Authors: Bredberg Göran
Published: October 2005

The so-called “surface preparation” of the cochlea is described and illustrated. This method allows counting precisely the number of hair cells over large segments of the organ of Corti and identifying the scars left by degenerated cells. The method is particularly useful for assessing injury to the cochlea by noise or other agents. Scanning electron microscopy, which allows three-dimensional visualization at high magnification, will also be illustrated in its application to the anatomy of the cochlea.
Noise Hazard Meter Based on Temporary Threshold Shift
Authors: Moser L. M.
Published: October 2005

Criteria for hazardous noise are based on TTS. Therefore, the easiest way to measure dangerous noise exposure will be with an instrument simulating growth and decay of TTS. The growth and decay of TTS in the range of interest is approximated with exponential functions. The meter consists of an A-weighted input stage, a logarithmic converter, and a 1ossy integrator. In a varying noise field the meter takes care of the time history of the noise. The output can be read on a monitor plugged into the instrument. The instrument is small enough so it can be comfortably worn.
Noise Control for a Textile Machine
Authors: Bruce R. D. , Gubitose N. F.
Published: October 2005

The noise at the operator's position of a U. S. Textile Company Ringtwister has been analyzed. Variations in the noise level due to spindle finish, belt tension, belt width, and spindle speed are discussed. By varying the finish on the spindle (e.g., plastic coated and grooved), noise levels were varied over a range of 13 dBA. The variation in noise level with belt tension was 3 dBA. Reduction in the width of the belt reduced the noise levels. A doubling of the speed increased the noise levels by approximately 7 dBA. A partial enclosure, designed to enclose the spindles on the machine, was constructed of 16-gauge metal with damping material and absorptive material applied to the inside. A total reduction of 10 dBA at the operator's position was achieved through the use of the spindle enclosure.