bluuebunny/crossref_metadata_2025 huggingface dataset:
Frequency Discrimination of Pure and Complex Tones
Authors: Zeitlin Lawrence R.
Published: November 2005

Utilizing the method of constant stimuli, subjects performed significantly better in discriminating small changes of frequency of complex tones (15-μsec pulse length) than in discriminating similar changes of frequency of pure tones. This difference was obtained at the 6 base frequencies used in this experiment, 190, 490, 990, 1500, 3000, and 6000 cps. The superior performance with complex tones was attributed to the presence of overtones, which made the discrimination task much easier. The maximum efficiency of subjects in discriminating frequency changes in the complex tones occurred between 490 and 990 cps.
Temporal Variables in Masking of Short Tones by Noise Bursts
Authors: Elliott Lois L.
Published: November 2005

In a study of monotic backward, forward, and simultaneous masking, short 1000-cps tones (5- or 10-msec duration; 2-msec rise time) were masked by noise bursts that varied in duration from 30 to 500 msec (0.5-msec rise time). Masking is independent of duration of the noise burst when the tone begins within 10 msec after noise onset, but beyond this interval, and contrary to the conclusions of Osman and Raab, simultaneous masking decreases as tone onset is delayed relative to noise onset. For some subjects, a decrease as great as 10 dB occurs (70 dB SPL noise) within 120 msec after noise onset. Two kinds of results occur as the terminations of tone and noise approach coincidence. Particularly for the shorter bursts, some subjects show a small decrease in masking when the tone offset coincides with or precedes noise offset by about 5 msec. For longer burst durations, some subjects show a small, consistent increase in masking (relative to the preceding decrease) prior to noise termination. These findings are compared with results of other investigators.
Backward Masking for Tones in Narrow-Band Noise
Authors: Wright H. N.
Published: November 2005

Appropriate transformations based on the theory of temporal summation were used to determine backward masking as a function of the time interval between the onset of 800-, 1000-, 1200-, and 1750-cps tones and the onset of an 80-dB narrow-band noise centered at 1000 cps, which partially masked the tones. Backward masking was found to consist of at least two phases separated by a transition region in which threshold did not appear to be determined by the duration of the probe tone. Masking at 800, 1200, and 1750 cps was found similar to that at 1000 cps, but did not extend as far back in time. The results are interpreted to mean that masking occurs first for those tones within a noise band and then spreads to those frequencies outside the band until the pattern commonly observed under simultaneous masking is obtained. [Research supported by a contract between the U. S. Office of Naval Research NOnr 669(13) and Syracuse University.]
On the Limits of Binaural Interaction
Authors: Robinson Donald E. , Deatherage Bruce H.
Published: November 2005

Deatherage, in 1961, found that his observers could obtain a fused and unitary image when the stimuli to the ears were clicks of different frequency content. When the frequency difference was large, however, the observers obtained two click images of different pitch that could be independently brought to the median plane of the head. The present experiments are an extension of that work. In one experiment, 4 different clicks were paired with each of 5 tone bursts. A centering task was performed with these stimuli at one sound-pressure level and at one sensation level. In a second experiment, 2 clicks were paired with each of 2 tone bursts under several values of rise-decay time for the tone bursts. The interaural-time differences required for a centered image show interesting relations to level, click-frequency, burst-frequency, and rise decay time. These results are discussed in terms of the kinds of operations that take place in peripheral encoding and in central processing. [Work supported by a contract between the U. S. Office of Naval Research and TRACOR, Inc.]
Differential Dichotic Sensitivity (DDS) Functions
Authors: Bergman Moe , Schon Terry D.
Published: November 2005

In a previous investigation (by MB) of the binaural fusion phenomena for pure tones, it was observed that the threshold of hearing in one ear can be determined by the effect of a signal in that ear on the localization of the same signal, presented simultaneously, in the contralateral ear. In the present study, normal listeners were exposed to pure tones presented at elevated sensation levels in one ear (reference) while the signal was introduced randomly into the other ear (test) until the subject reported a “bulge” or “flare” of the high-level tone in the reference ear. At sensation levels in the reference ear ranging from 35 to 105 dB, the bulge occurred upon the introduction of signal into the test ear at sensation levels from 5 to 35 dB. In general, there was little change in the critical bulge-inducing level in the test ear, despite progressively higher levels in the reference ear, until the highest intensities were applied to the latter. At these levels, it is probable that crosscranial leakage from reference to test ear affected the results.
Compact Pitch Computer
Authors: Daggett N. L. , Gold B.
Published: November 2005

The operational rules of the pitch computer used in the Lincoln Laboratory experimental vocoder have been described at the Fourth International Congress on Acoustics, Copenhagen, 1962 (Bernard Gold, “Description of a Computer Program for Pitch Detection,” Paper G34). These rules, and some additional rules for buzz-hiss detection, described in a companion paper, have been implemented by a combination of analog and integrated circuit digital techniques. The complete pitch computer is packaged in a subrack 5×19×22 in. The basic storage element is an 8-bit circulating shift register. An array of 24 such registers provides the input memory. Use of this technique allows serial computations to be executed, simplifying the arithmetic portion of the computer and greatly reducing the density of interconnecting wiring. It is becoming increasingly clear that accurate pitch detection noticeably improves the quality of a channel vocoder. The work reported in this paper is a step toward realizing the improved vocoders as practical devices.
Prediction of the Course of F2 across Consonants
Authors: Pickett J. M. , Coulter D. C.
Published: November 2005

In a formant-tracking vocoder, any lag in acquiring correct formant-frequency values, after the release of a consonant, produces false formant transitions; these may cause an error in transmission of the consonant. Tracking of the second formant (F2) is especially critical in this respect. In the present study, some means of predicting F2 are presented. F2 relations across consonant constrictions were measured in spectrograms of the spontaneous speech of five male speakers. The study compared prediction of the frequency of postconsonantal F2 by three extrapolations of preconsonantal F2: (1) holding the last value; (2) linear extrapolation of the last course; and (3) exponential extrapolation of the last course. Holding and exponential extrapolation were superior to linear extrapolation. Mean prediction error was about 300 cps with the two better methods. Errors were then partitioned according to upward or downward last course, in conjunction with high-middle, or low-frequency regions for the beginning of extrapolation. Certain partitionings reduced mean prediction error to 200 cps. [Research supported in part by the U. S. Army Electronics Research and Development Laboratory.]
Harmonic Distortion of Initially Sinusoidal Plane Wave
Authors: Williams A. O. , Ingenito F.
Published: November 2005

To examine this problem further, a simplified acoustical equation with one nonlinear and one absorption term is reduced, via Fourier series, to a set of simultaneous, nonlinear differential equations of first order, one per harmonic. Propagation is toward +Z, originating, with a first harmonic only, at Z=0. If vn is particle-velocity amplitude of the nth harmonic, dvn/dz equals a conventional absorption term (linear) plus two sums of terms vsvn−s and vsvn+s. The first sum represents “accretion” to the nth harmonic from lower ones, and the second, “depletion” from the nth to higher. This set reduces exactly or closely to known special solutions (e.g., Fubini, Keck-Beyer, Fay). Numerical integration on a modest computer is easy; 20 harmonics, to 8 times the “critical distance,” have been done, agreeing closely with more-elaborate calculations by others, Near Z=0, “depletion” is negligible; the equations become exactly soluble by iteration, in different forms with or without absorption. Adding “depletion” as a perturbation, thereafter, is one step better than using both nonlinear terms thus. Some more-general theorems can also be proved. Thus far, the asymptotic behavior is puzzling. [Supported in part by Aeronautical Systems Divisions, Wright-Patterson Air Force Base.]
Experimental Study of Acoustical N Waves
Authors: Wright Wayne M.
Published: November 2005

The electrical discharge has proved to be a reliable and convenient source of finite-amplitude acoustical pulses for laboratory investigations. The pressure signature of a typical spark sound pulse has a shape that is roughly that of the letter N; an initial shock front is followed by a gradual decay, a rarefaction phase of somewhat longer duration than that of the initial condensation, and an abrupt rise to ambient pressure. An experimental study has been conducted with discharge energies of up to 1 J and spark-gap lengths of up to 2 cm, and acoustic waveforms have been observed on the normal axis for propagation distances between a few gap lengths and 50 cm. Use of a high-frequency electrostatic microphone in a rigid baffle provides faithful transduction of abrupt pressure changes with rise times of less than 1 μsec. The maximum observed shock strength and pulse durations have been of the order of 1% of an atmosphere and 20 μsec, respectively. Experimental results include evaluation of the dependence of shock amplitude and pulse length upon spark parameters and propagation distance. [Work supported in part by the U. S. Office of Naval Research.]
On Finite Amplitude Attenuation of Sound Waves in Air
Authors: Allen Clayton H.
Published: November 2005

Some modified forms of Rudnick's [J. Acoust. Soc. Am. 30, 339 (1958)] relations governing the propagation of finite-amplitude acoustic waves have been derived that simplify calculations for certain practical applications. The theory compares well with data for spherically expanding waves in the free field of a piston radiator. The inclusion of ordinary atmospheric absorption into the finite-amplitude relations permits the evaluation of a limiting distance over which finite-amplitude losses are significant; beyond this distance, ordinary attenuation dominates finite-amplitude effects.
Noise Reduction of Jets by Multiple Nozzles and Turbo Fans
Authors: Eldred Kenneth M.
Published: November 2005

Simplified jet-flow models are utilized to predict the noise of jets issuing from complex or multiple nozzles and annular coplaner bypass nozzles. Comparison of the noise predicted from the simplified jet-flow models with experimental data is generally good, thus enabling the utilization of the prediction methods in determining optimum-design trends and limits for future jet engines. The results demonstrate that future jet engines can have significantly lower noise levels than those of current generation jets if noise is one of the major parameters that is considered during engine design. [Work supported by the U. S. Air Force Aeronautical Systems Division, Flight Dynamics Laboratory, Dynamics Branch, under contract AF 33(616)-5744.]
Laboratory Simulation of Aircraft-Propeller Noise
Authors: Griffith E. D. , Hancock R. N. , Raulston C. M.
Published: November 2005

Systems for simulation of aircraft-propeller noise in the laboratory have been developed at LTV Vought Aeronautics. The basic unit of these systems is an electronic propeller-noise generator that was designed and built as a Company-sponsored R and D program. This unit produces a voltage signal proportional to the rotational and vortex sound pressures generated by aircraft propellers. The rotational noise is made up of the fundamental 4P blade-passage frequency plus several significant harmonics. Adjustments are possible on frequency, amplitude, and relative phase of these discrete-frequency components. Vortex noise is random in character and adjustments of over-all level, spectrum shape, and frequency-band limits are possible. In a final stage, the rotational- and vortex-noise components are mixed to produce simulation of the complete propeller-noise signal. This voltage signal is used as an input to a high-intensity progressive-wave sound system. In this system, sound-pressure levels of 150–170 dB are generated for testing of structural panels. Another use for this signal is as an input to a high-fidelity speaker system that operates at SPL's of 70 to 125 dB. This system provides simulated propeller noise for interior-fuselage acoustic investigations and human-factors studies. Equalization of either system operating into various impedances of different panels and enclosures can be accomplished by appropriate adjustment of noise components produced by the propeller-noise generator. Typical results are shown in slides illustrating measured waveforms and spectra. These results are compared to propeller noise measured from aircraft propellers.
Acoustical Measurements of Static Tests of Clustered and Single-Nozzled Rocket Engines
Authors: Tedrick Richard N.
Published: November 2005

The predictions of the acoustic effects of the static firing of large rocket engines have usually been based upon such engine parameters as specific impulse, nozzle diameter, etc. However, the recent development of large clusters of smaller engines have introduced a new possible variant. Tests were performed using two 1.5-million-pound-thrust rocket systems—one with a single engine and one with a cluster of eight smaller rockets. The two systems, NASA's F-1 and Saturn S-1, use the same liquid fuel and were fired on the same test stand. It was also possible to equate most of the other engine parameters so to effect a comparison of the acoustical effects resulting from static tests of clustered and single-nozzled rockets. Acoustical data are presented in this paper, showing both the over-all and octave-band acoustic-power levels for both test configurations. The differences in near- and far-field directivities and in mechanical-to-acoustical conversion efficiencies are presented.
Characteristics of Noise Generated by an Electro-Pneumatic Transducer
Authors: Van Houten John J. , Fiala Walter T.
Published: November 2005

Questions have been raised regarding the capability of the electropneumatic transducer to produce a Gaussian distribution of pressure amplitudes. Recent measurements indicate close similarity to the Gaussian distribution. These measurements were made in a progressive-wave tube at a location very near the transducer. Peaking in the distribution is noted at distances further downstream of the sound generator. These results are illustrated, along with measurements of propagation distortion at higher intensity levels. Essentially, undistorted sinusoidal response has been measured at levels to 180 dB (re 0.0002 dyn/cm2) at the immediate exit of the transducer. The finite-amplitude effects associated with propagation at these intensities places distinct limitations on spectral control at locations distint from the transducer location.
Noise in Rolling-Element Bearings
Authors: Scanlan R. H.
Published: November 2005

In recent years, a great deal of attention has been directed to the subject of the audible sound produced by ball and roller bearings. In addition, fluid- and structural-borne sound of audible or higher frequency emanating from such bearings is of great interest in installations like those of submarines. The subject, presently attacked from a variety of angles with each yielding partial results, has to date given rise to a number of somewhat conflicting efforts. It is, however, possible at the present juncture to make a number of general remarks, some of which are aimed at reconciling these efforts. This is the purpose of the present paper. In this paper, the questions of the definition of rolling-element “noise,” its basic causes, its quantitative measurement, and criteria for its objective and subjective evaluation are discussed, with technical illustrations. The paper is drawn from continuing research in this area at Case Institute of Technology.
True Model of the Vocal Tract
Authors: Anthony J.
Published: November 2005

A static model of the supraglottal speech processes has been built. Dimensions were obtained from x-rays laminagrams, photographs, casts, and direct physical measurements of one subject. Anatomical dissection of a cadaver was used to verify the relative positions of the muscles and the shape of the vocal tract. The building of the model and a review of the literature have revealed certain inadequacies in the traditional description of the vocal tract. The acoustic output of the model with a simulated larynx source was compared with the sound produced by the subject on whom the model was based. Differences between the two sounds are discussed. [Research supported by Public Health Service, U. S. Department of Health, Education, and Welfare, research grant No. NB-04595.]
Analysis of Glide Consonants
Authors: House Arthur S. , Stevens Kenneth N.
Published: November 2005

Utterances of three talkers in which the glide consonants /w/ and /j/ occurred were processed by analysis-by-synthesis methods utilizing a digital computer. The frequencies of the three lowest formants were measured approximately every 30 msec and the so-called “target” positions and temporal characteristics of the consonants and vowels were described. The data on the temporal characteristics of the formant frequencies indicate the extent to which the articulation of the glide consonant is influenced by the adjacent vowel. As a by-product of the study, data on formant bandwidths, glottal spectra, and other spectral irregularities were examined, and indicated that the spectra of the glide consonants differ from those of vowels in several respects. Implications of the findings for acoustical and articulatory theories of speech production are discussed briefly. [Work supported in part by the U. S. Army Signal Corps, the U. S. Air Force Office of Scientific Research, and the U. S. Office of Naval Research; in part by the National Science Foundation (grant G-16526), the National Institutes of Health, U. S. Department of Health, Education, and Welfare (grants MH104737-03 and NB-04332-01), and the National Aeronautics and Space Administration (grant NsG-496); and in part by the U. S. Air Force (ESD) under contract AF19(628)3325.]
Utilization of the Redundancy of the Phonemic Transcription of Speech for Automatic-Speech Recognition
Authors: Otten Klaus W. , Kleiner Richard T.
Published: November 2005

An automatic-speech-recognition system segments continuous speech into phonemes and identifies those phonemes. This segmentation and acoustical-recognition process is far from perfect. A high-order linguistic-recognition process, which considers the restrictions in the use of phonemes in sequences, can correct a large percentage of the errors made in the acoustical-recognition process. A study and simulation program was conducted to determine the relationship between the redundancy of the spoken langauge in its phonemic transcription and the potential percentage-error correction as a function of the original error rate. Models of 4, 8, and 16 phonemes with redundancies comparable to those of spoken languages were synthesized. These synthesized phoneme sequences were artificially distorted. Through use of first-order conditional probabilities, partial correction of the distorted sequences was achieved. The results of the computer-simulation program indicate that speech recognition with low error rates is feasible even if the initial acoustical recognition has a high error rate, provided that the statistical properties of the acoustical-recognition elements are known and that they are used in a linguistic error-correcting recognition process as simulated. The simulation program and the numerical results are presented.
Relaxation in Polyethylene: Orientation of Lamellar Crystals
Authors: Eby R. K. , Colson J. P.
Published: November 2005

In polymers with a lamellar morphology, crystallization in the presence of a temperature gradient can result in oriented lamellar crystals. Although the orientation is imperfect because of the helical [twisted] nature of the lamellae, shear stress applied by a torsion pendulum can be oriented with respect to the long lamellar dimension. Data of this type have been obtained to provide insight into the mechanical relaxation of polyethylene. The data assist the interpretation of experiments in which samples of the same density are obtained by different thermal histories.
Effective Elastic Coefficients for Wave Propagation in Strained Elastic Crystals
Authors: Thurston R. N.
Published: November 2005

The concept of effective elastic coefficients for wave propagation in strained crystals is examined critically. It would seem natural to expect that wave propagation in a strained crystal be governed by effective elastic coefficients that obey the same symmetry relations as the thermodynamically defined coefficients for crystals of the same symmetry as the strained crystal. However, it follows from publications of Toupin and Bernstein (1961), Truesdell (1961), and Noll and Truesdell (1964) that this is not true in general. The usual symmetry is lost because the effect of initial stress in the equations of motion governing wave propagation is to replace relations like eljkm=ejlkm by relations that depend on the initial stress. The idea of effective elastic coefficients remains useful, but it is important to distinguish them from the thermodynamically defined coefficients and to recognize that they do not obey the same symmetry relations. Two different sets (based on ρV2 and ρ0W2, respectively) of effective elastic coefficients for quartz under hydrostatic pressure are defined and related to the thermodyqnamically defined coefficients, the pressure, and the deformation. Here, W is the “natural velocity,” defined as the unstressed path length divided by the transit time under pressure.
Transmission of Directional Perception
Authors: Bauer B. B. , DiMattia A. , Rosenheck A.
Published: November 2005

In a previous paper [B. B. Bauer, “Stereophonic Earphones II,” presented before the 13th Ann. Convention Audio Eng. Soc., 1961], one of the authors described a scheme for transmitting directional information using crossed dipole receptors connected to dichotic earphones through a stereo-binaural network [B. B. Bauer “Stereophonic Earphones and Binaural Loudspeakers,” J. Audio Eng. Soc. 9, No. 2, 148–151 (1961)]. In the paper, it was predicted that improved realism would be obtained by using receptors having a limacon characteristic. Recently, experimental work with cardioid pattern receptors has been performed, confirming the above prediction. This paper describes the new apparatus and the orientation ability afforded by it. Applications of the directional transmission scheme to aerospace and underwater communications are discussed. [Work supported in part by the Avionics Laboratory, Research and Technology Division, ASD, W-PAFB, Ohio, under contract AF 33(357)-10737.]
Feedback and Noise-Signal Detection at Three Performance Levels
Authors: Campbell Richard A.
Published: November 2005

The effect of the presence or absence of feedback, or immediate positive reinforcement, was studied at three performance levels: 87.5%, 75%, and 62.5% corrct. The BUDTIF experimental procedure [R. A. Campbell, J. Acoust. Soc. Am. 35, 1732 (1963)] was utilized. Signal-to-noise ratios were varied in a 104-trial run (about 7 min) so as to maintain the desired performance level. The noise was set to 35 dB SL. One group of naive subjects was used. Each subject was presented one of the 6 conditions of performance level and feedback for 5 consecutive runs. Threshold signal-to-noise ratios, variability of levels utilized, and the time required were determined for each run. These subjects tended to reach their optimum performance during the second run with subsequent deterioration. Another group of experienced subjects was presented with all six conditions in each of six 1-hr sessions. Threshold signal-to-noise ratios, variability of levels utilized, the time per run, and interrun variability were determined. The only definite effect of feedback, for either group, was the tendency toward less interrun variability with feedback for the experienced subjects. These subjects expressed definite feelings regarding the effect of feedback, which were generally unrelated to their actual performance.
Precise Timing of Underwater Sound, Using Phase-Reversed Pulses
Authors: Lord Norman W.
Published: November 2005

Using a vertical source array, directive horizontal transmission of 1200 cps sound pulses was studied in the Caribbean north of Bonaire Island. Both the fixed source and a linearly moving receiver were operated at 800 m depth and ranges between 0.35 and 5.6 NM. Close to the source, the pulse consisted of two sets of 12 wavefronts, each in immediate sequence with their phases exactly reversed. The directly propagated pulse exhibited a well-recognized phase-reversal point out to a range of 4 NM, beyond which it gradually merged into the basic pulse. Measuring transmission times to this phase reversal, a total of 4000 were statistically analyzed, using a moving average to eliminate the effect of the linear motion of the receiver. The rms deviation of transmission time from this average remained between 0.3 and 0.5 msec for ranges up to 4 NM, beyond which it climbed to 2 msec. The normalized autocorrelation coefficient calculated with respect to time interval always had the same shape and a first null near 1.5 sec. If we use the velocity inhomogeneity that was measured at the same time and the Chernov theory for an idealized model, we would infer an rms deviation in transmission time 100 times smaller than was measured. It seems that, particularly for horizontal transmission, one must consider the large and rapid variation that can be caused by the motion of inhomogeneous water across the band of multipaths connecting the source and receiver. [Hudson Laboratories, Columbia University Informal Documentation No. 43. Work supported by the U. S. Office of Naval Research.]
Investigation of Fluid Flow over Flexible Surfaces
Authors: Karplus Henry B.
Published: November 2005

An investigation into the transition to turbulence shows that initially steady laminar flow changes to a slowly oscillating flow, which then breaks up into intermittent turbulence. Intermittency then increases until turbulence is fully developed near the walls. Interaction with infrasonic waves (fractional to a few cps) generated by a sirenlike flow chopper in a water tunnel indicates that certain frequencies of fluctuation are attenuated whereas others are amplified. The region of wave amplification is a function of surface-structure roughness and flexibility. With these parameters, effectiveness of wall treatment to delay turbulence can be investigated empirically. [Work was supported by the David Taylor Model Basin.]
Acoustic Simulation of Underwater Sounds
Authors: Miller Norman D. , West G. W.
Published: November 2005

Training of sonar personnel in the recognition of underwater sounds can be greatly facilitated by electronic simulation of target-radiated noises. For simulation purposes, radiated noise from a vessel is composed of a shaped broad-band noise-spectra and line-spectra components. A broad-band spectrum is modulated at a frequency corresponding to the blade rate of the ship's propellers. Although the basic signature can be defined from an analysis of the radiated noise, the qualities that aurally distinguish one class of target from another or different operating modes of a target are subjective in nature and must be added to the basic signature for a purpose of audio recognition. A typical class of noise that must be considered is cavitation. This paper describes the process of simulating a ship signature. A tape recording demonstrates the buildup of a radiated-noise signature for a cargo vessel and highlights the audio cues used for aural recognition.
Panel Response and Its Relation to the Type of Excitation
Authors: Richards E. J. , Wilby J. F.
Published: November 2005

Recent work at the Institute of Sound and Vibration Research involves the relative response of small panels to various types of sound and pressure-fluctuation excitation. The relative response of panels to jet noise, to siren noise, and to actual boundary-layer turbulence is described and examined. The effect of pressurization is discussed and the sound radiation from the panel is examined.
Correlation of Launch-Vehicle Aerodynamic Noise with Spacecraft Flight-Vibration Data
Authors: Schiffer Robert A.
Published: November 2005

It has been observed that the maximum vibration levels experienced by a launch vehicle occur in the regions of q max and transonic flight. Flight-vibration data from Ranger launches 1 through 4 have been correlated with available wind-tunnel transonic buffet fluctuating-pressure data in order to establish a realistic basis for vibration-test definition for vehicles that have not previously been flown. Statistical analysis of the wide-band vibration data suggests a linear correlation with the wind-tunnel wide-band fluctuating-pressure data. Good correlation was obtained between the average vibration-response spectra calculated using the empirical method of P. Franken of Bolt Beranek & Newman Inc. and the 95 percentile log-normal acceleration confidence level obtained by spectral analysis of the flight data.
Some Experimental Effects of Curvature on Response of Simple Panels to Intense Noise
Authors: Rucker Carl E.
Published: November 2005

Systematic tests show the effects of curvature on the vibration modes, strain response, and life characteristics of thin plates. Both discrete-frequency and random-noise tests on clad 2024-T3 aluminum panels of 20×20×0.020-in. dimensions are included. Discrete-frequency classical nonlinearities are exhibited. Mean-square spectral analyses, probability-density distributions, and crossing-rate statistics are included from random-test bending- and membrane-strain responses. Good agreement was obtained between experimental and calculated vibration frequencies for the lower-order vibration modes. Constant-level random inputs produced lower peak-strain levels and associated failure times were generally longer as panel curvature increased.
Effect of Surface Curvature on Boundary-Layer Noise
Authors: Meecham William C.
Published: November 2005

It has been previously remarked that inviscid turbulent boundary layers over a flat plate produce no dipole sound. The plane acts merely to reflect the volume-generated quadrupole sound. An image argument is used to examine the effect of a slight surface curvature on the dipole-generated sound. It is found that, if R is a surface radius of curvature and L the thickness of the boundary layer, then the amplitude of the farfield dipole sound is reduced by a factor of L/R. Thus, if L/R<(Mach number), the dipole sound can be neglected in order of magnitude estimates. The surface merely reflects and diffracts the volume-produced sound. The result of this analysis is that, for many practical situations involving boundary layers, the sound intensity will be proportional to the 8th power of the Mach number. The amount of dipole sound produced by bumps on the surface is also discussed.
Articulation-Test Control Circuits
Authors: Snow William B.
Published: November 2005

In the field of speech-transmission research, the articulation test remains a basic operation against which machine methods and calculations must be checked. Such test is simple in theory, but usually requires considerable coordination between separate locations for talker, listeners, and operator. The latter may have complex circuit changes to make and check between tests. If poor or noisy systems are under test, coordination between talker and listener may be easily lost. Thus, the mundane details of the actual This paper describes circuit arrangements that have been found to promote such efficiency.
Mathematical Analysis of Glottal Waveforms
Authors: Vezza Albert
Published: November 2005

An ensemble of glottal waveforms is represented by a weighted linear sum of exponential orthonormal functions, which may be written in closed form fi(t)=ΣkAikexp(skt). The glottal waveforms are obtained by means of inverse filtering. The signal ensemble consists of glottal waveforms of several speakers uttering a number of American English vowels. Suitable complex frequencies sk are chosen and an IBM-1620 computer is used to calculate the coefficients Aik for each member of the signal ensemble. [Research supported by the National Science Foundation under grant GP-590.]
Real-Time Measurement of Pitch Perturbations
Authors: Howard C. R.
Published: November 2005

An electronic system capable of measuring pitch perturbations in vocalic utterances is described. These perturbations are normally minute variations in the length of adjacent pitch periods. It has been shown that the size and number of these perturbations increases in the presence of laryngeal abnormalities such as cancerous growths. A semimanual technique for this measurement has been described in the literature [P. Lieberman, J. Acoust. Soc. Am. 33, 597 (1961)]. The present apparatus, when used with a high-quality instantaneous pitch-period indicator, allows the measurement to be accomplished in real time. The tests described were carried out using regenerated pulse trains derived from visual measurements and are shown to give perturbation and median-pitch measurements comparable to the computer-calculated values. [Research supported by the National Science Foundation under grant GP-590.]
On the Relationship between Prosodic Features and the Lexical Content of Speech
Authors: Soron Henry I.
Published: November 2005

The test material for this experiment consisted of 40 simple sentences. The words in 10 of these expressed fear; 10 others expressed anger; 10 connoted joy; while the remainder were neutral. These were read 4 times by two speakers, who attempted to convey one of these emotions by his manner of speaking, even though the lexical content and the emotion might not correspond. The speakers' voices were recorded simultaneously by a high-quality condenser microphone and by a throat microphone whose output was filtered to lie between 50 and 200 cps, thus eliminating intelligibility while preserving most of the prosodic features. These sentences, both high-quality and filtered, were presented to groups of male and female listeners, who were asked to give forced-choice impressions. Results show that, for stimuli containing both text and prosodic features, the listeners responded to the emotions conveyed by the prosodic features 62.3%, 84.2%, 59.5%, and 88.5% of the time for fear, anger, joy, and neutrality, respectively. The responses to emotions conveyed by the words were 36.3%, 42.0%, 39.9%, and 41.6%. For filtered sentences containing only prosodic features, correct identification was made 77.6%, 79.7%, 73.7%, and 93.3%, respectively.
Syllable Segmentation in Voiced Environments
Authors: Stowe Arthur N.
Published: November 2005

This paper gives details of improvements in the computer program for syllable segmentation, which was described at last year' spring meeting. Discussion at that time mainly concerned environments where voicing is maintained across syllable boundaries. The procedures reported were based on evaluation of minima in the amplitude versus time functions for the total speech band and for three subbands. Although the subbands were sensitive to boundary events, they also introduced false boundary decisions. It has now been discovered that a comparatively simple function relating the first moment of the spectrum density to time could be used to inhibit the false reports. Its effect on the over-all segmentation task was estimated on about 950 utterances of isolated words. Close to 90% of the words are now segmented correstly with very few false segmentations.
Concerning the Problem of Calibrating TDH-39 Earphones at 6 kHz with a 9A Coupler
Authors: Rudmose Wayne
Published: November 2005

The Telephonics TDH-39 earphone when measured on the NBS 9A coupler exhibits a strong peak in its frequency-response function in the vicinity of 6 kHz. Detailed threshold data taken over the frequency range 5.5 to 6.5 kHz in 100-Hz intervals show that the earphone does not perform in the same manner when coupled to the human ear. The ASA type I coupler also exhibits the same lack of correlation between real-ear response and coupler response. Six other methods of calibration are described and the results show that the real-ear correlation is better for any of these methods than for either of the methods using the two accepted standard couplers. [Work supported in part by the Lena E. Callier Trust.]
Occlusion Effect of the External-Ear Canal and Its Effect upon Bone Conduction
Authors: Tonndorf Juergen , Greenfield Elliot C. , Kaufman Roger S.
Published: November 2005

The study of this effect was recently included in a larger series of experiments in cats on bone conduction (BC). The effect was finally shown to have a dual cause, both contributing factors affecting the esseo—tympanic component of BC: radiation of sound by its osseous walls into the lumen of the external canal whence it is transmitted via eardrum and ossicular chain toward the cochlea. The two factors are: (1) The effect of a high-pass filter constituted by the open ear canal. (Elimination or reduction of this filter produces a low-frequency emphasis proportional with inverse frequency.) (2) An alteration of the resonant properties of the external canal. (This factor affects mainly the middle to high frequencies.) This concept combines aspects of earlier theories, notably those of Rinne (1855) and Huizing (1960) [resonance] and of von Békésy (1941) and Onchi (1954) [low-frequency emphasis]. The current results, in conjunction with earlier findings of the present long-range study, permit, for the first time, of a theory of BC compatible with observational facts, e.g., the clinical tests of Bing, Runge, Weber, and Gelle. Explanations for all of these differ slightly, but significantly, from each other. [This study supported by a Public Health Service, U. S. Department of Health, Education, and Welfare grant.]
Stimulus Parameters Contributing to TTS for Tone Bursts at 2.2 kc/sec
Authors: Smith P. F. , Pikler A. G. , Harris J. D.
Published: November 2005

Over 200 men were given 5–120 min of tone pulses of 37–250 msec, duty cycle 0.01–0.25, at 105–115 SPL. It was impossible to confine attention to 4-kc/sec TTS2. An audiometric tape led to 12 matched PDR-8 phones, providing a 5-frequency audiogram once a minute for 6 min. The concept was developed of TTS as an area, one audiogram for every moment in time, and each interpreted as a single numerical value, the value 1 being the area of some criterion hearing loss. The integrated area of this criterion loss is called from the Greek a kryt (plural: kryter). The total effect of a stimulus is thus assessed by plotting kryter over time. One nox equals 1 kryt over 2 min. The total information concerning hearing loss for several frequencies over time can now be compressed into a single nos value. In thus study, the nox value rises linearly with SPL, linearly with log session duration, negligibly with pulse duration, and with negative acceleration over duty cycle. Interactions are of a secondary order of importance.
Hearing-Loss Trend Curves and the Damage-Risk Criterion in Diesel-Engineroom Personnel
Authors: Harris J. D.
Published: November 2005

Well over a thousand diesel enginemen exposed to 105–110 dB SPL in the relevant octaves have been examined periodically for the past 5 years. With 360, hearing was demonstrated to be normal at the very beginning of engineroom duty. When a cross section of hearing in this population is sampled, with all factors contributing to hearing loss confounded, previous data and trend curves from similar populations are confirmed in general; but when known hearing losses at the outset of duty are eliminated, surprisingly little loss is seen even at 4 and 6 kc/sec. These mild losses cannot be explained in terms of ear-protective devices. It may be that the young age of this population differentiates it in this regard. It is more likely that current hearing-conservation practices arise from data compounded of initial hearing losses and TTS during industrial audiometry, in addition to permanent threshold shift (PTS). Data from TTS in this population sampled before exposure to engine noise cast doubt on the generality of the conclusion that TTS2 at 5 kc/sec for a 8-hr exposure will predict PTS after 10-yr exposure. Thanks are due to C. K. Myers for audiograms, C. E. Greene for equipment calibration, and P. F. Smith for the TTS data.
Modal Characteristics of Composite Elastic Structures
Authors: Coale Charles W.
Published: November 2005

Analysis of the dynamic response of complex structures requires knowledge of the dynamic characteristics of the structure. In many cases, a structure is composed of several sections, each having a known or determinable set of modal characteristics. In this paper, a matrix eigenvalue equation is derived for determination of the modal characteristics of the composite structure in terms of the characteristics of its sections. Use is made of functional vector modes to describe the modal behavior of the sections in 3-dimensional space. The problem is then formulated in terms of the modal and rigid-body coordinates of the sections. The eigenvalue equation is derived by application of Lagrange's equations. The connection conditions between sections provide relations between the coordinates, which are used to reduce the size of the matrices involved. Several arrangements of the sections are treated, including tandem and multibranch configurations. As an illustration of the application of the above equations the dynamic characteristics of a satellite with flexible solar panels are considered.
On the Damping of Laminated Elastic/Viscoelastic Plates
Authors: Azzi V. D.
Published: November 2005

That the elimination of the deleterious effects of flexural vibrations may be accomplished by the introduction of a damping mechanism into a vibrating system is well-known. The present investigation is concerned with the development of a theoretical means for the prediction of the damping effectiveness and flexural rigidity of combined elastic and viscoelastic laminae subjected to flexural vibrations. Considering the damping material as being linearly viscoelastic and employing the complex modulus type of notation, a general solution is obtained for the damping-loss factor and the flexural rigidity of a general 3-layer plate. In contrast to earlier investigations, the composite plate is considered to be in a state of biaxial stress, and no restrictions of symmetry are imposed on the cross section. Based on the general solution, results are obtained and compared for a number of example configurations, illustrating the effects of varying the dimensions and physical properties of the individual laminae. An experimental program was conducted and results were compared to the analytical predictions, thus confirming the validity of the theoretical solution.
Composite Loss Factors of Selected Laminated Beams
Authors: Blasingame W. , DiTaranto R. A.
Published: November 2005

The composite loss factors for beams having alternate laminae of elastic and viscoelastic materials have been computed for variations of frequency for 3- and 5-layer beams using the results obtained by Kerwin [E. M. Kerwin, D. Ross, and E. E. Ungar, “Damping of Plates in Flexural Vibrations by Means of Viscoelastic Laminae,” in Structural Damping (Am. Soc. Mech. Eng., New York, 1959)]. To properly design structures with laminated materials, in order to withstand and attenuate vibratory energy, it is desired to know the composite loss factor of the beam for different cross sections and materials. The results of this investigation obtained through the use of high-speed computers as a series of curves displaying the variations of composite loss factors as a function of frequency for different cross sections and materials. The cross-sectional configurations and materials were selected so that trends in composite loss factor could be obtained for such considerations as changes in thickness and/or physical properties of the elastic and/or viscoelastic material. These results may serve as a guide to the proper vibratory design of laminated materials.
Damping due to Mode Coupling: A Wave Analysis
Authors: Smith P. W.
Published: November 2005

In a uniform thin beam, there are waves of three types: torsional, longitudinal, and bending. The last exists in two forms: propagating and exponentially attenuated vibrations near boundaries. When the neutral axis for bending (i.e., the elastic axis) is offset from the inertial axis, the various types of wave are coupled. For a small offset, the wave coupling is small. However, reflection from a free end can result in a significant conversion of energy from one type to another. For example, a longitudinal wave is reflected as a weaker longitudinal wave and as a bending wave. No conversion occurs at a supported end. Results of this wave analysis are used to determine the damping of longitudinal modes of a finite beam, with free ends, in a case where longitudinal motion is undamped but bending motion is damped. The modal loss factor is found to be proportional to the square of the ratio of offset distance to beam length. [Work supported by the David Taylor Model Basin.]
Porous-Element Endfire Receivers for Sound Reception in Rapid Motion
Authors: Chin Gerald , Eichler Ewald
Published: November 2005

Porous wall elements of high flow resistance lend themselves to the construction of streamlined receivers possessing remarkably low flow noise. A porous-pipe receiver utilizes the delays suffered by the wave components traveling within a fluid-filled porous-metal pipe to achieve optimal phasing of noise and signal components. The backward response is suppressed by means of a reentrant-pipe absorber or by linear tapering along the line of the open cross section of the pipe, which makes the porous element double as anechoic termination. Calculated flow noise is compared with glider measurements obtained by Raytheon Company. At Mach numbers near 0.2, flow noise below 25 dB SPL in terms of the spectrum of an equivalent plane wave incident in the endfire direction at 2000 Hz was observed with a receiver 1 ft long and 1 in. in diameter. Existing wind tunnels are not quiet enough for such measurements. [Supported by the Office of Naval Research, Acoustics Branch.]
Group-Velocity Dispersion Due to Pulse Reflection from a Frequency-Dependent Boundary Impedance
Authors: Lange James N.
Published: November 2005

A time delay resulting from the reflection of a pulse from a frequency-dependent boundary impedance is computed and its effect on the measurement of ultrasonic group velocities is demonstrated experimentally. The time delay adds to the transit time of the pulse in the medium and its frequency dependence leads to an apparent dispersion of the group velocity.
Significance of S. S. Stevens's contribution to science
Authors: Zwislocki J. J.
Published: November 2005

This paper discusses the contribution of Stanley Smith Stevens to science, particularly in the realm of sensory psychology.