bluuebunny/crossref_metadata_2025 huggingface dataset:
Automatic Detection of English Stress
Authors: Jancosek Elizabeth , Takefuta Yukio
Published: September 2005

The object of this study was to examine the applicability of simple statistical methods in the processing of the acoustic parameters for automatic detection of English stress. Acoustic parameters such as the fundamental frequency, intensity, and duration were measured from 340 two-syllable words recorded by 10 American speakers. These measures were then put into statistical transformations to simulate the human perception of the English stress. The relative efficiencies of these transformed parameters for the detection of stress signals were computed by calculating the classical indexes of signal detectability. No single parameter could perfectly predict the perception of the stress signals by human listeners. A further simulation of selecting, weighting, and combining the data of more than one of these transformed parameters, with a preset program, was made using a digital computer. The detection of stress signals by this computer simulation was found to be as accurate as detection by average native listeners. [This research was supported by a contract between The Ohio State University Research Foundation and the Office of Naval Research.]
Identification of Brief Pauses in the Fluent Speech of Stutterers and Nonstutterers
Authors: Love Laura R. , Jeffress Lloyd A.
Published: September 2005

Research has indicated that the fluent speech of stutterers is different from normal speech. A previous experiment suggested that part of the difference between the fluent speech of normals and stutterers is to be found in the number of brief pauses, but varying recording gain levels could have affected the measurements. The present paper reports an attempt to resolve the gain problem and to examine brief pauses in the speech waveform. Twenty-five normal subjects and 25 fluent stutterers were employed as S's. Taped samples of reading were processed, using a computer of average transients as the basic unit. An analysis of variance showed decisively that in our method of processing the speech samples, gain had affected pause length but had done so in the same manner for both stutterers and nonstutterers. There was no interaction. Stutterers were found to have a significantly greater number of pauses 150 to 250 msec long. A simple counter, called a “speech-pause counter,” was devised that was able to give results as reliable as those of the computer, using a single sample of speech from each subject.
Verbal Transformation Illusion: Satiation or Synthesis?
Authors: MacKay Donald G.
Published: September 2005

When a word is played over and over by tape loop, listeners hear illusory changes. For example, “police, police, police…” may be heard as “please,” “fleece,” and “fleas” as well as “police.” The present study investigated two factors influencing the rate of change of these perceived forms, which normally increases regularly over time. (1) Phonetic similarity. A word such as “town” was played for 3 min followed by either a phonetically similar word (e.g., “down”) or a phonetically different one (e.g., “crash). The rate of perceptual change for the phonetically similar word was faster than for the phonetically different word. (2) Semantic similarity. Again, a word such as “town ” was played for 3 min, this time followed by either a synonym (e.g., “village”) or a nonsynonym (e.g., “rampage”). Perceptual changes were initially faster for synonyms than nonsynonyms, but the rate of change reached an upper bound sooner for synonyms than nonsynonyms. These findings suggest that speech perception may involve two processes at the semantic level: (1) an analyzer or filter stage, susceptible to fatigue or satiation and (2) an analysis-by-synthesis stage for generating hypotheses about speech input.
Analysis of Fundamental Frequency Contours
Authors: Levitt H. , Rabiner L. R.
Published: September 2005

Fundamental frequency contours for several simple declarative sentences were estimated using a computer-simulated pitch extractor. Measurements were obtained for three American male speakers repeating each of three sentences three times. The speakers were instructed as to which syllables should be emphasized in each sentence. The purpose of the experiment was to determine which aspects of the fundamental frequency contour reflect vowel stress and which aspects reflect characteristics of individual speakers. The stressed vowel regions of the fundamental frequency contours were found to be easily identifiable across speakers and replications. In addition, the variability of the contours during unstressed regions appeared to be greater than that for the stressed vowel regions. This result suggests that in modeling fundamental frequency contours greater weight should be attached to deviations between observed and predicted values in the stressed vowel regions.
Ultrasonic Attenuation in Liquid Hellium above 1°K at 1 GHz
Authors: Imai J. S. , Rudnick I.
Published: September 2005

The attenuation of first sound in liquid helium in the temperature range from about 1°–4°K was measured with a two crystal interferometer with a variable path length. Because of the short acoustic wavelength of about 2000 Å and the large attenuation, some details of the interferometer system are unusual and will be discussed. The ultrasonic attenuation measurements in this temperature range can be divided into several regions. There is a classical region above the superfluid transition with ordinary viscous and thermal attenuation processes. There is a region near the lambda transition in which our measurements reveal an anomalously high attenuation peak located at, or very nearly at, the lambda point. This peak is not due to the Landau-Khalatnikov mechanism, which produces a large peak in this region at lower frequencies, but is postulated to be due to critical point fluctuations. There is a region below the lambda transition in which roton and phonon interactions control the attenuation process. Our measurements show the local maximum which separates the hydrodynamic régime from the collisionless régime and agree with the theory of Khalatnikov and Chernikova.
Ultrasonic Attenuation in Liquid Argon, Nitrogen, and Oxygen at 1 GHz
Authors: Imai J. S. , Leonard R. W.
Published: September 2005

The ultrasonic attenuation at 1 GHz was measured in liquid argon, nitrogen, and oxygen at their boiling points with a variable-path-length two-crystal acoustic interferometer. The attenuation in argon shows an absorption in excess of the value calculated from the classical Stokes-Kirchhoff equation for shear viscosity and thermal conductivity. The excess absorption can be attributed to a volume viscosity predicted by Gray and Rice, and is in good agreement with the lower-frequency measurements of others such as Naugle and Squire. The attenuation measurement in nitrogen shows a similar excess absorption and is in good agreement with the lower frequency values of Singer and Lunsford. The ultrasonic attenuation measurements in oxygen indicate that it may also have a volume viscosity. In the process of aligning the apparatus, some data were obtained in methanol that give a lower volume viscosity than that observed at lower frequencies.
Dips in Sound-Velocity Dispersion Curves for Relaxing Liquids
Authors: Nichols William H.
Published: September 2005

The theoretical phase velocity v=(Reω)/k of temporally damped waves in liquids with relaxing loss mechanisms is not in all circumstances a monotonically increasing function of wavenumber k. In CCl4, if the (longitudinal) viscosity does not relax, then v vanishes for k>1.24×107 cm−1; if the viscosity has a relaxation time of 10−13 sec, v vanishes only for 1.24×107<k<1.34×107 cm−1; if the viscous relaxation time is 10−12 sec, v is monotonic increasing [W. H. Nichols and E. F. Carome, J. Chem. Phys. 49, 1000 (1968)]. In benzene, if the viscous relaxation time is 10−13 sec, v may merely dip at k=1.27×107 cm−7. In argon, for either choice of viscous relaxation time, v is monotonic increasing. [This research was supported in part by the U. S. Office of Naval Research and by the Advanced Research Projects Agency.]
Magneto-Acoustic Interaction in Mercury
Authors: Sachs Thomas D. , Hughes Gregory P.
Published: September 2005

The magnetically induced acoustic absorption coefficient in liquid mercury has been measured around its inverse relaxation frequency using an on-line computer and magnetic fields of up to 10 kg. The hybrid computer-operated differential measuring system took between 2560 and 25 600 experiments per run. The results agree with Anderson's predictions [J. Acoust. Soc. Amer. 25, 529 (1953)]. [Work supported in part by the National Science Foundation.]
Ultransonic Relaxation in Normal Propyl Alcohol-Water Mixtures
Authors: Madigosky W. M.
Published: September 2005

Ultrasonic relaxation has been observed in a binary mixture of normal propyl alcohol with water in the frequency range 5 to 200 MHz. As expected, the absorption goes through a maximum at intermediate concentrations. However, the frequency dependence can not be explained by a single relaxation time. A theory of Romanov and Solvyev, which assumes that the excess absorption is due to concentration fluctuations, was found to predict correctly the observed distribution of relaxation times. The size of the minimum concentration fluctuation allowable and its concentration dependence is discussed. A high-frequency absorption or “B” value in excess of that predicted by shear and compressional viscosities was observed, and this also peaks as a function of concentration.
Sound-Velocity Studies of Carbon Dioxide in the Critical Region
Authors: Carome E. F. , Singal S. P. , Feke G. T.
Published: September 2005

The behavior of sound velocity in the critical region of carbon dioxide is under investigation. The study involves several aims: (a) to determine the temperature and density dependence of the velocity minima; (b) to deduce the behavior of the specific heat at constant volume in the critical region; (c) to investigate the possibility that the behavior of a substance near the critical point depends not only upon its temperature and density, but also upon the past history of the material. Measurements of velocity as a function of temperature are made isochorically using a resonant cavity technique. Results indicate that minima in sound velocity occur on the coexistence curve. Minima significantly lower than any previously reported have been observed. Information regarding the temperature dependence of the specific heat has been obtained, as well as evidence of hysterisis in the fluid. [Work sponsored by National Aeronautics and Space Administration.]
Material Damping
Authors: Jones D. I. G.
Published: September 2005

The phenomenon of mechanical hysteresis is discussed briefly in this paper with reference to common structural materials. The class of materials known as viscoelastic materials is then introduced and briefly discussed in terms of phenomenological behavior. These materials form the basis of a wide variety of clamping techniques that may be divided into two main classes, namely, those that utilize stiff viscoelastic materials and those that utilize soft viscoelastic materials. The current materials state of the art is then discussed with reference to the development of both stiff and soft viscoelastic materials giving effective damping over wide temperature ranges, and the improvement in wide temperature range performance resulting from their use is discussed. It is shown that a great deal of work is necessary before viscoelastic materials are effective at the most severe temperature conditions.
Damping in Built-Up Structures
Authors: Ungar Eric E.
Published: September 2005

A summary is presented of available information on the damping associated with shear and normal relative motions at simple structural joints; the important mechanisms and parameters are indicated, and the applicability to realistic structures of results for idealized configurations is discussed. Data on the damping of panels due to variously attached beams are reviewed; the importance of the “fluid-pumping” mechanism is pointed out, and the edge-absorption coefficient approach for predicting panel damping is discussed. The contributions of energy transport and energy dissipation to establishing the responses of multipanel structures are described on the basis of statistical energy analysis. Difficulties associated with measuring the damping of panels in situ are discussed, as well as the results of some attempts at overcoming them. Areas requiring further study are delineated.
Noise Measurements and Noise Measurement Systems
Authors: Lang W. W.
Published: September 2005

Only a brief description of the measurement of sound level and sound-pressure level is given in S1.2-1962, American Standard Method for the Physical Measurement of Sound. The initial task of S1-W-51 is to prepare a partial revision of S1.2-1962, which includes recommended procedures for measuring weighted and band-limited sound-pressure levels under conditions that are commonly encountered in the field and laboratory. This work on methods of airborne noise measurement is closely coordinated with the activities of Working Group 16 (Measurement and Assessment of Noise) of Technical Committee 43 on Acoustics of the International Organization for Standardization. The draft proposal being prepared by S1-W-51 classifies the purposes of the measurements, identifies different kinds of commonly encountered noise, describes techniques for measuring steady and nonsteady noise as well as the instrumentation systems suitable for such measurements, and includes general guidelines for noise measurements in the field and in the laboratory.
Measurement and Evaluation of Aircraft Noise
Authors: Kolk F. W.
Published: September 2005

This paper covers three areas of activity being stimulated and/or directed by Committee SAE-A-21, which is also S3-W-44 (S1). The documents published by SAE-A-21 are reviewed with a description as to the adequacy of these documents in describing procedures needed in the measurement and evaluation of aircraft noise. Work on the development of additional documents to fill in gaps in the present list is also reviewed with a description of the status of this work and, where possible, an indication of steps required to complete the work. Research work needed for the further standardization of methods for measurement and evaluation of aircraft noise is also discussed. A description is given of projects underway and the need for new projects.
Checked/Unchecked Correlation in the English Vowels
Authors: Stuart Don Graham , Singh Sadanand
Published: September 2005

All English dialects show a series of oppositions of the type beet/bit, bet/bate, look/Luke, etc. Several have a complete correlation of this “checked/unchecked,” cutting through the entire vowel pattern. All interpretations of this opposition that play a rôle in current discussions treat the unchecked members of the correlation (e.g., beet, bate, Luke, etc.) as being formed by the addition of a specific mark to the corresponding checked member. For Smith and Trager (and Sweet before them), this mark was dipthongalization; for Jones, length; for Jakobson, Chomsky, and Halle, tenseness. These all assume some extra effort, some greater complexity, for the unchecked vowels as compared with the checked vowels. This assumption is contradicted, however, by the neutralization of this opposition in open syllables. That the archephoneme here is realized with a phonetic type resembling the unchecked term implies that either it is the checked term that is marked or that the English vowel system has a perverse economy in which a special articulatory effort is demanded precisely in contexts where this effort can have no linguistic relevance.
Acoustic Influence of Consonants on the Duration of the American English Vowel /I/
Authors: Fertig Ralph H.
Published: September 2005

A set of 576 different CVC monosyllables was generated by combining 23 consonants and silence in initial or final position around the vowel /I/. This set was recorded by one speaker in three different orders on three different days. Sound spectrograms were produced, and data consisting of three phoneme durations and 11 frequency values for each of the first three formants of the vowel were extracted from them, employing a TV camera and light-pen controlled computer display system. Results demonstrate that the vowel duration is influenced by (1) consonantal position, initial or final, (2) consonantal voicing, (3) consonantal manner of articulation, (4) consonantal horizontal place of articulation, and (5) the articulatory pace for a particular clay. Several parametric descriptions for obtaining accurate vowel durations in CVC contexts are presented.
Palatal Movements for Vowel-Nasal and Nasal-Vowel Utterances
Authors: Speaks Charles , Benitez Luis D.
Published: September 2005

Observation of temporal characteristics of palatal movement during nasal-vowel (NV) and vowel-nasal (VN) utterances were made on two patients. Although the two subjects differed considerably with respect to absolute measures of timing during the closing and opening phases of palatal movement, the relation between these two phases, expressed as a ratio, seemed quite constant. For NV utterances, the palate closed at a rate slower than for vowel (V) alone to accommodate the initial nasal. The opening characteristics for NV were similar to V alone, which was to be expected from the common vowel termination. The slowed closing, but constant opening, produced a closing-opening ratio for NV that was slightly smaller than for V alone. The rate of movement during the opening phase for NV was slowed markedly in comparison to either V or NV.
Mechanical Behavior of the Diaphragm during Speech
Authors: Hixon Thomas J. , Minifie Fred D. , Peyrot Alain H. , Siebens Arthur A.
Published: September 2005

Simultaneous recordings of the following were made during the speech of five subjects: acoustic signal, lung volume, electromyographic activities of the diaphragm and rectus abdominis, pleural and abdominal pressures, and anteroposterior displacements of the thorax and abdomen. Records were obtained at various lung volumes and loudness levels during sustained [a] productions and during a variety of speech utterances. Results indicate that the diaphragm often plays an active rôle in the regulation of the respiratory driving force at high lung volumes during productions of normal or less than normal loudness. For some productions, its active rôle terminates at lung volumes where the net muscular effort of the entire respiratory mechanism remains opposite in sign to airflow. This suggests a dissociation of the diaphragm from other inspiratory muscles for certain speaking conditions despite the need for a braking action against elastic forces. Occasionally, active diaphragmatic behavior was observed at lung volumes below the functional residual capacity. Possible explanations for such activity will be offered.
Some Relationships between Solid and Liquid Structure as Exemplified by Water
Authors: Kamb Barclay
Published: September 2005

Phase relationships suggest that the structure of liquids is related to an average over structural features of various solid polymorphs. In water, such an average must include the high-pressure polymorphs of ice. Consistent with contributions from these phases are the decrease in volume on melting, the radial distribution function, dielectric constant, structural compressibility, band of OH stretching frequencies, and fusion energy. The effect of these contributions is a great increase in H-bond bending in the liquid, by comparison with ordinary ice. The presence of distinguishable contributions from different structure types requires transient existence of molecular clusters of contrasting structure and density. Various lines of evidence suggest that such clusters must be small (∼10–100 molecules). Defects involving H-bond breakage are required in the boundary zones between the H-bonded molecular clusters. These defect regions probably have low molecular-packing density and high mobility, and are responsible for relaxation processes in the liquid structure. Most of the high heat of fusion and the excess heat capacity of water must be due to creation of defects of this type. The temperatures and pressure dependence of the viscosity can be explained on this basis.
Effects of Details of Dynamics on dc Transport Coefficients in Solution
Authors: Harris Stewart M. , Friendman Harold L.
Published: September 2005

The theorem that a dc transport coefficient is determined completely by the zeroth moment of the time-relaxed correlation function of the underlying dynamic process applies only to coefficients for fluxes that are linear in the driving fields and in which the carriers of the motion do not mutually interact. For other (“higher-order”) transport coefficients more information is required. Conversely, one may use experimental data for higher-order transport coefficients to determine more than just the zeroth moment, the correlation time of the underlying motion. This was illustrated by calculations for a particular Brownian-like model for the underlying dynamics [J. Chem. Phys. 48, 120 (1968)]. In the framework of the general Liouville equation a simple higher-order transport coefficient, the Hall conductance, may be resolved into two terms. One is the first moment of the time-relaxed momentum correlation function of the carrier in the field-free system while the other, an intrinsically non-Markoffian contribution, is not simply a functional of this correlation function. The latter term does not appear in the earlier work. It vanishes in limiting cases corresponding either to a dilute plasma or the converse extreme corresponding to ions in a dense, strongly interacting solvent. It seems that these results may be extended to other higher-order transport coefficients.
Ionic Translation in Molten Salts
Authors: Barton A. F. M. , Bannard J. E. , Hills G. J.
Published: September 2005

Measurements are reported on the electrolytic conductances of the molten alkali nitrates as a function of pressure and temperature. Corresponding studies of the isothermal compressibilities enable the full range of thermodynamic parameters of activation to be evaluated. Isothermal volumes of activation and isochoric enthalpies of activation all vary systematically with ion size. The compressibilities agree well with those previously estimated from acoustical experiments and can be fitted satisfactorily to a van der Wools equation of state.
Ultrasonic Relaxation and Diffusion-Controlled Processes in Electrolytic Solutions
Authors: Yeager Ernest , Goldfarb Louis
Published: September 2005

Aqueous electrolytic solutions with substantial ionic association usually exhibit an ultrasonic relaxation at frequencies of 109–109 Hz. The excess absorption in this range is attributed to the diffusion controlled formation of an encounter complex. The recent data of the author's together with that of Kehl and Plass at Göttingen indicate the frequency corresponding to maximum excess absorption per wavelength to be at a substantially higher value than reported by earlier workers. The data do not fit the frequency dependence expected for a simple relaxation in this frequency range. Factors contributing to this deviation include: (1) use of the absorption of pure water as an approximation for the nonrelaxing portion of the observed absorption and (2) failure of the theory for the diffusion controlled formation of the encounter complex to take into account the diffusion controlled relaxation of the ionic atmosphere as a whole with the encounter complex just corresponding to the distance of closest approach without changing the chemical nature of the separate ions. The experimental data will be interpreted in light of these effects. [Research supported by the Office of Naval Research.]
Detection of Signal with Poisson Arrival Time
Authors: Luce R. Duncan , Green David M.
Published: September 2005

The beginning of each trial is marked by a light. From this onset a signal is presented according to a Poisson process with a mean wait of about 5 sec. Once the signal, a sinusoid partially masked by noise, is presented, it remains on until a response occurs. The subject is instructed to respond as soon as he hears the signal. A trial is terminated as soon as a response occurs. Three basic latency distributions are measured. One is the time from the beginning of the trial to the occurrence of a response, given that no signal has been presented: the second is the latency of the response from signal onset; the third is the time from the beginning of a trial until the occurrence of the signal, given that no response has occurred. The tails of these latency distributions are all exponential and the time constant of these tails can be used to estimate quantities analogous to the hit and false-alarm rate of more conventional detection situations. [This research was supported by a grant from National Science Foundation.]
Monaural Detection with Contralateral Cue (MDCC): Interference between Detection Processes
Authors: Taylor M. M. , Clarke D. P. J. , Smith S.
Published: September 2005

A sinusoid was the masked monaural signal in a MDCC experiment [M. M. Taylor and S. M. Forbes, J. Acoust. Soc Amer. 42, 1194(A) (1967)]. During each presentation interval, a cue was derived from the signal by a change in phase and amplitude and presented unmasked to the other ear. Psychometric functions, determined by varying the masker level, suggest that two independent detection processes are involved, the ordinary monaural process and one that uses the information in the cue. When the cue phase is correct (≈55° lead at 500 Hz for most observers), both processes tend to give the same answer on a given trial, but the cue-using process works at lower signal-noise ratios (S/N). When the phase is wrong, the cue-using process is misleading, and for S/N at these low levels, performance is below chance. At medium S/N, the processes compete and performance is near chance. At high S/N, the monaural process dominates and performance is error free. The region of competition depends strongly on cue intensity, suggesting that the monaural process, but not the cue-using process, is masked by the contralateral cue.
Amplitude Discrimination in Noise, Pedestal Experiments, and Additivity of Masking
Authors: Henning G. Bruce
Published: September 2005

The masking effect of a stimulus composed of a noise masker, a sinusoidal masker, or both, may be represented in a simple three dimensional space. The space shows performance as a function of (1) a measure of the level of the sinusoidal components relative to the noise and (2) a measure of the relative energy in the signal plus sinusoidal masker waveform and the waveform of the sinusoidal masker alone. Results that appear complicated in other representations appear straightforward in this space. For example, over wide ranges, neither frequency, duration, or interaural phase of the signal affect the shape of the space but produce, at most, only a simple translation.
Image Fusion, Broadening and Displacement in Sound Localization
Authors: Gardner Mark B.
Published: September 2005

The fusion or blending of two or more spatially separated complex signals (such as speech) into an apparent single image requires that the individual signals be reasonably alike in quality and follow each other in rather dose sequence (within about 50 msec). If both the quality and arrival time conditions are fully met, complete fusion appears to occur and a single image is heard coming from a single location. If these conditions are only partially met, then only partial fusion or image broadening results. The degree of broadening may be relatively small or it may be sufficient for the image to appear to fill the intervening space between the physical boundaries of the real sources. For certain combinations of parameters, the creation of a single image either inside or outside these boundaries (image displacement) may occur. The present paper describes a number of arrangements that may be used to achieve each of these effects. The techniques employed date from as early as the mid-eighteen hundreds to the modern filter and computer techniques of recent years.
Some Interrelated Acoustics and Aerodynamics of Transonic Shock-Boundary-Layer Unsteadiness
Authors: Luksus E. J. , Huang J. T. , Stevens V. C.
Published: September 2005

During nominally subsonic flow (M=0.60 to 0.90), there may exist locally supersonic environments that are unstable, showing extreme susceptibility to excitations that cause unsteady displacement or unsteady rippling of associated shock fronts. Intense unsteady pressure fluctuations result when these shock fronts are so distributed. In AEDC's 16T facility, Lockheed has recently studied such unsteady pressure fluctuations on forward portions of several rocket shroud models; and the combination of large model size (21.6 in. diam) and small microphone size (0.07 in. diam) has admitted some very fine resolutions of some acoustic environments associated with unsteady shocks. This paper illustrates typical data, both acoustic and aerodynamic, and presents them as interrelated symptoms of the shock unsteadiness associated with such models.
Fatigue Evaluation of Noise-Suppression Materials
Authors: Scott D. H.
Published: September 2005

Test programs have been conducted and are continuing in order to determine the acoustical characteristics and noise-suppression capabilities of various porous materials including fiber metals. Even though some data have been published on the structural properties of such materials, little has appeared with respect to the fatigue behavior. It has been proposed that these materials be used as face sheets over cellular panels in an engine duct liner configuration. For this reason, it was necessary to establish S-N data for use in relation to acoustical fatigue life design criteria of the liner. Coupons were prepared from the various materials for testing as clamped cantilever beams attached to the head of an electromechanical shaker. Using a sinusoidal excitation, tuned to their natural first-mode frequency, to ensure repeatability, the specimens were tested to failure under constant-stress, reverse-bending, zero-mean-stress conditions. This paper summarizes the information obtained from the investigation and discusses the preliminary test work with emphasis on some of the problems encountered—e.g., strain gauging, response curves, and failure definition. Ideas for future tests (hardware qualification tests) are also mentioned.
Eigenvalue Density of Conical Shells
Authors: Miller David K. , Hart Franklin D.
Published: September 2005

An analysis is made for determination of the number of eigenvalues and the eigenvalue density of conical shells over a wide range of cone geometries. The Galerkin method is used to determine a frequency equation. Values perdicted by this closed-form solution show favorable agreement with experimental results available in the literature. The frequency equation is then expressed in terms of wavenumbers and the k-space geometry is obtained. A numerical integration procedure for determination of the cumulative number of modes from the k space is developed. A comparison is made of values obtained from an actual count of the eigenvalues predicted by the frequency equation and this procedure shows a high degree of correlation with the k-space integration technique. Using finite differences in conjunction with the k-space integration, the eigenvalue density is obtained. The influence of variations in cone angle, thickness, and truncation are found to be significant. The results of the study are normalized with respect to geometric parameters and expressions covering a wide range of configurations are presented in graphical form. [This work is sponsored by NASA, Langley Research Center.]
Laboratory Facility for Annoyance Rating Studies
Authors: Hart Franklin D. , Pearson Richard G.
Published: September 2005

A study relating the individual characteristics of people and their subjective evaluation of annoyance to different noise stimuli is described. Particular attention is given to a description of the environmental facility and the speaker system that was designed and constructed for purposes of the study. The results of a series of pilot studies to establish a rating scale and suitable exposure levels are presented. PNdB levels are compared with the mean annoyance ratings obtained in the facility based on data from 166 test subjects. The tests were conducted under two room conditions that are categorized as acoustically soft and acoustically hard. Results show that the effect of environmental condition on individual annoyance ratings was small in comparison to the frequency characteristics of the noise stimuli. [This work is sponsored by NASA, Langley Research Center.]
Noise, You Get Used to It
Authors: Webster J. C. , Lepor M.
Published: September 2005

On the basis of several Laboratory studies, noise levels of 64 dB SIL (based on the octaves centered at 500, 1000, and 2000 Hz), or 71 dBA, were proposed as the criteria levels for acceptable voice communications. Two validation surveys were undertaken where ambient-noise levels were measured and subjective questionnaires were completed in various ship's spaces. When asked to rate a space along a five-point scale of noisiness (VERY QUIET, QUIET, MODERATELY NOISY, VERY NOISY, and INTOLERABLY NOISY), responses tended to center on MODERATELY NOISY regardless of objective noise level (SIL, LA, PNL, LC, LL), confirming the remark, “You get used to it.” When asked to give binary judgments on whether (1) normal speech was affected, (2) work was affected, (3) the space was acceptable, or (4) the environment was loud (and/or noisy, and/or annoying), vice very loud (and/or very noisy, and/or very annoying), the following results were obtained: 80% thought that neither speech nor work was affected (and the space was acceptable) at an SIL of 67 dB (68 dB) or 73 dBA (74 dBA); 20% would accept higher noise levels, but 20% also said levels this high did affect speech and work and made the space “uncomfortable” and the noise “loud.”
Characteristics of Noise Generated by Secondary and Auxiliary Aircraft Systems
Authors: Gasaway Donald C.
Published: September 2005

Fixed- and rotary-wing aircraft employed by the military contain subsystems, many of which generate noise. The author has attempted to survey the spectrum of secondary and auxiliary systems that produce acoustic noise that invades occupied areas of fixed- and rotary-wing aircraft. The variety of such systems are classified into exclusive categories and illustrations and acoustic descriptions are given for each group. A few systems described include: pneumatic and electrical power systems, environmental and pressurization systems, secondary mechanical power distribution units and systems, rain and ice control and removal systems, and others. In addition, contributions of the noise generated by such systems that elicit potentially undesirable auditory responses among crew-members and passengers are identified and discussed.
Noise Measurements on the World's Largest Airplane
Authors: Gibson John S.
Published: September 2005

Noise measurements have been made under the flight path of the Lockheed/Air Force C-5A for both landing and takeoff. Comparisons are shown of PNdB calculations for the C-5A transport with the new generation high-bypass TF39 engines and the C-141 transport with low-bypass TF33 engines. Octave-band time histories, pure-tone corrections, and time-duration corrections comparisons are presented showing the differences between the two aircraft. Most noticeable features of C-5A are the rapid decay of noise as the aircraft passes overhead and relative lack of human irritability to the noise.
Method of Measuring the Acoustical Impedance
Authors: Merhaut Josef
Published: September 2005

An electrostatic transducer, made as a sandwich with a thin foil membrane, gives an output voltage, the first derivative of which is exactly proportional to the volume velocity passing through it. Such a sandwich is located at a place where the acoustic impedance is to be measured with a feeding loudspeaker in front of it. The loudspeaker is fed by a tone generator with a compressor, controlled by the first derivative of the output voltage of the sandwich. The arrangement acts as a constant-volume velocity generator. In this case, the acoustical impedance of the attached system is proportional to the acoustic pressure, measured by a condenser microphone at the output of the sandwich.
Device for the Measurement of Acoustic Impedance in Air
Authors: Rudolph Janet A. L. , Hixson E. L.
Published: September 2005

The device described here basically measures the radiation impedance of a thin circular membrane. The membrane is excited by a push-pull electrostatic drive, and its velocity is determined by a carrier capacitance measurement method. The force applied divides between the air on both sides and the membrane itself. One side is terminated in a reflectionless chamber, and the unknown is presented to the other side. The ratio of potentials proportional to force and velocity give total impedance from which the unknown can be determined. When pressure is measured by a microphone, specific impedance is measured and compensation for the membrane and terminated side is not necessary. However, the separation of the membrane and microphone results in a phase error. The characteristics and limitations of the device are presented and some measurements given. Some application to room acoustics and sound-reproducing systems are suggested. [Supported in part by the Office of Naval Research.]
Transient Response of High-Frequency Condenser Microphones
Authors: Benson Robert W.
Published: September 2005

Observations of the transient response of microphones have been obtained to determine rise time and sensitivity. It is desirable to determine the behavior of microphones when extended durations of both positive- and negative-going pressures are applied. The diffraction effects are also of importance for field measurement of transient phenomena. A modified shock tube has been constructed which allows for a variety of pressure waveforms for both normal and grazing incidence. Several commercial microphones having steady-state frequency response up to several hundred kilohertz have been studied to determine their suitability for the measurement of transients. Procedures have been established that allow for defining the limitations of microphones for transient pressure measurements. [This work was performed for U. S. Army Medical Research and Development Command, Washington, D. C., under contract.]
Measurement of Residual Stress with Ultrasonic Waves
Authors: Benson Robert W. , Chapman J. Ronald
Published: September 2005

Ultrasonic shear waves have been used to measure the stress in metallic samples by determining the relative velocity of propagation for particle motion along the principal axes of stress. Techniques have been developed for determining the orientation of the principal axes of stress and the measurement of the magnitude of the equivalent uniaxial load corresponding to a residual stress. Additional measurements using ultrasonic waves allow for the measurement of the stress gradient near the surface of the material. Procedures will be described that allow for field-type measurements of stress in metallic specimens. An application of the techniques for the measurement of stress in plates containing weldments will be given. Stresses in aluminum samples may be measured to an accuracy of 1000 psi. [This work was performed for the George C. Marshall Space Flight Center under contract.]
Response of Model Structures to Sound Fields
Authors: Benson Robert W.
Published: September 2005

An experimental investigation has been conducted to determine that aspect of a sound field that is the forcing function for a structure placed within the sound field. Special emphasis has been placed on excitation of structures at their natural frequencies for which maximum motion exists. Sample configurations including bars and plates were chosen for study. All samples investigated appear to have a low acoustical impedance at modal frequencies. Maximum sample motion is therefore obtained when the pressure gradient at the sample is a maximum rather than when pressure is a maximum. Boundary conditions behind the structure have a marked effect upon sample motion. The effect of these observations on fatigue testing of structures within reverberation rooms will be discussed. [This work was performed for the Langley Research Center under contract.]
Measured Radiation Characteristics of Hexagonal Transducer Arrays
Authors: Gruber George J.
Published: September 2005

Network representations are utilized to extract the head velocities and radiation resistances (and thus the radiated power and directivity pattern) of seven circular piston resonant projectors in hexagonal geometries from a set of driving force, motion, and sound-pressure measurements. These measurements included the velocities of the vibrating surfaces, input phasing angles, Q's of the elements, surface pressure profile, etc. A two-term approximation was found to be sufficient to describe the pressure over a passive element due to an active element. The second term is simply the self-pressure of the acoustically activated element. The complex coupling coefficient depends on the Q of the elements in a manner not accounted for by the conventional theories of acoustical interactions. It was found that a single adjustment in the velocity of an active reference element due to the radiation force of another active element adequately describes the measured changes in the velocity and the radiation resistance of the reference element. Superposition of the interaction effects was valid only for the first four neighbors in all cases studied. [Work supported by the National Science Foundation, Engineering Divison, and the U. S. Office of Naval Research (Acoustics Programs).]
Pressure-Insensitive Deep-Sea Velocimeter
Authors: Lynch T. , Patten H. , Webb D.
Published: September 2005

This paper describes the development and testing of a pressure-insensitive instrument for measuring the speed of sound in the ocean. The instrument utilizes pressure-insensitive electronics, single-transducer sing-around mode, and a double-bounce 5-cm sound path. The pressure-insensitive electronics are exposed to ambient pressure at depth without using a pressure vessel; this approach, which employs a single, lightweight pressure-equalized housing for both the transducer and the electronics, results in an instrument that has considerably less weight and bulk than those currently used. The paper describes the development of improved electronic detection techniques utilizing a tunnel diode/hybrid switch; these techniques limit the maximum long-term electronics error from all parametric changes (pressure, temperature, voltage, acoustic dynamic input, and aging) to less than ±1/50 000. In addition, the paper describes methods of mechanical temperature and pressure compensation and the results of rigorous calibration measurements.
Optical Farfield Polarization Analysis for an Acoustically Birefringent Liquid
Authors: Klein W. R. , Riley W. A. , Donnell L.
Published: September 2005

The experimental determination of the optical rotation and the degree of ellipticity of the light in the Fraunhofer diffraction orders permits the determination of fundamental optical and mechanical properties of an acoustically birefringent liquid. The solution of the optical-diffraction problem involves the separate treatment of the light of polarization normal to and within the plane of the acoustical wavefronts taking account of all relative phase shifts. Analytic solutions are discussed for Raman and Nath and for Bragg diffraction conditions as well as numerical solutions for the intervening transition region.
On the Transmission of Plane Waves through Layered Linear Viscoelastic Media
Authors: Shaw Richard , Bugl Paul
Published: September 2005

The propagation of two-dimensional time harmonic waves through a plane layered viscoelastic medium is considered in terms of the equivalent elastic plane strain problem with modified Lamé constants that are complex and frequency dependent. The problem is formulated directly in terms of stresses and displacements rather than potentials and is solved by matrix methods. If the incident wave is not attenuated in the direction parallel to the layering, as would occur if the incident wave were to travel through a semi-infinite elastic half-space before striking the viscoelastic layers, interface waves could be generated only if one of the layers is “pseudoelastic,” i.e., has at least one real wave speed. In this case, interface waves may be generated in the same manner as in the purely elastic case. If the incident wave is attenuated in this direction, however, interface waves could be generated for specific angles of incidence and material properties.
Normal Modes for a Translating Open-Ended Cylindrical Cavity
Authors: Brown Bernard , Libelo Louis F.
Published: September 2005

The effect of motion on the normal modes and wave patterns of a rigid open-ended right circular cylinder translating at constant velocity along its axis through an elastic medium has been studied. Solution of the wave equation, in cylindrical coordinates, for small-amplitude harmonic disturbances in a homogeneous, linear, irrotational elastic medium has been effected within the moving boundaries. The solutions yield the resonant frequencies and the changes in the nodal patterns with frequency and velocity.
Dispersion of Flexural Waves in Circular, Bimaterial Cylinders—Theoretical Treatment
Authors: Reuter Robert C.
Published: September 2005

The frequency equation for flexural waves travelling in infinitely long, circular, bimaterial cylinders is obtained, based oil the equations of linear elasticity. Several first branches of the dispersion curves are presented and discussed for various ratios of the constituent cylinder radii. Dispersion characteristics significantly different from those predicted by the theory for homogeneous cylinders are realized. Some implications in regard to equivalent properties are discussed.
Noise Masking of a Change in Residue Pitch
Authors: Patterson Roy D.
Published: September 2005

A comparison was made of the effectiveness of noise in masking (1) a change in the frequency of a sinusoid, and (2) a change in the repetition rate of a pulse train that had no low-frequency energy. The sinusoid and the pulse train had the same pitch. It was found that, whereas the change in the pitch of the sinusoid was better masked by low-frequency noise, the change in the pitch of the filtered pulse train was more easily masked by high-frequency noise. These results indicate that the basis for the low pitch associated with the pulse train is its high-frequency components. This conclusion contradicts the place theory of pitch perception which proposes that the filtered pulse train produced a low pitch because nonlinear distortion in the hearing process introduces a strong low-frequency component. [This research was supported by the National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare.]