bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic Stresses and Strains in a Buoy Cable System Subjected to Longitudinal Excitation Using a Continuum Approach
Authors: Laura P. A. , Goeller Jacques
Published: October 2005

This paper deals with the analysis of the stresses and displacements in a buoy cable system subjected to longitudinal excitation when one-dimensional wave effects are taken into account. The cable is considered as a distributed mass with external linear damping due to fluid viscosity and internal damping simulating viscoelastic behavior of the cable material. The payload mass is attached to a rigid foundation by an elastic spring and a dashpot. The results are presented in terms of parameters common to a discrete single degree of freedom (df) system so that comparisons could be made showing the effects of cable distributed mass and cable external damping. Numerical results are presented for the case of a sinusoidal displacement at the upper end of an externally damped elastic cable and payload damping at the lower end. The results show that the cable stress in the low-frequency range can be higher for a system with cable damping than the stress value obtained in the case of a system with no damping. External damping, however, does reduce the stress in the vicinity of the resonant frequencies. It is also shown that the cable stress increases significantly at the higher harmonic resonant frequencies. Comparisons of the analysis of a distributed mass system with the one corresponding to a lumped parameter system using an effective cable mass of one-third its actual mass in a single (df) discrete system indicates fairly good agreement below the first fundamental frequency. The largest difference occurs in the vicinity of resonance where the continuum approach yields higher amplification factors. Better agreement over the fundamental-frequency range is obtained using a two-parameter lumped system. The case of a two-material cable system is also analyzed and experimental verification of the linear mathematical model is presented. Future research will consider improvement of some of the simplifications introduced in the analysis: nonlinear versus linear external damping, finite versus infinitesimal deformations, etc.
Speech Generation with a Computer Simulated Vocal-Tract Analog
Authors: Ruiz P. , Mermelstein P.
Published: October 2005

An interactive computer facility for speech generation is described. The vocal tract is modeled as a 12-section nonuniform transmission line coupled to a nasal tract represented as a second transmission line of fixed shape. A discrete sequence of articulatory states, excitation and timing parameters is used for control. Movement between specified articulatory states is achieved by linear interpolation of the lumped reflection coefficients for each section. Execution time is about 40 times real time, and this allows repeated on-line synthesis and data modification of sentence-long utterances. The control program provides for quick and convenient addition or replacement of items in the sequence of articulatory targets, graphical or numeric cross-sectional area input, and time-motion display of a vocal tract changing in accordance with the specified data. In addition to the audio output, oscillogram and formant-track displays are available to the experimenter. The facility is to be used to evaluate postulated models for articulatory movements. Examples of synthesized material are presented.
Selected Vowel-Consonant Learning by Preschool Children
Authors: Gilbert J. H.
Published: October 2005

As part of an ongoing investigation of the phonological development of vowels, an experiment using four sets of vowel-consonant (VC) syllables has been conducted. The four vowels /i/, /æ/, /ɑ/, /u/ were combined with the four consonants /t/, /Þ/, /f/, /s/ in a series of ensembles. These ensembles were presented as learning tasks to a group of four-year-old preschool children. Performance during learning did not reach unity for any vowel or consonant despite the linguistic abilities of the children and the linguistic nature of the stimuli. There appeared to be a “marker” vowel, which was both the most easily identified and the most easily learned, particularly in conjunction with the alveolar plosive /t/. Although it might be assumed that familiarity with the language would have allowed for better learning of all stimuli, this was not apparent. Manipulation of frequency, intensity, and time parameters in synthesized VC syllables is suggested as a further means of evaluating VC learning in terms of the Distinctive Feature system. [This research was supported by the National and Medical Research Councils of Canada.]
Speech Synthesis by Rules with Physiological Parameters
Authors: Hiki Shizuo , Harshman Richard
Published: October 2005

A speech-synthesis system that consists of a dynamic analog vocal-tract circuit controlled by programs written for the LINC-8 digital computer is being developed. The computer program is designed to be able to control the synthesizer with acoustical parameters for the sound sources plus parameters specifying either vocaltract configuration or the neuromuscular commands underlying such configuration. The time functions of these parameters or the instantaneous vocal tract shape can be drawn in with a special X-Y curve input device, and can be displayed on the CRO in the course of synthesis. The possibility of effecting simplicity and economy of input for the synthesis by specifying neuromuscular parameter (rather than vocaltract configuration) is discussed. [This research is partially supported by the National Institutes of Health, U. S. Department of Health, Education and Welfare, and the Office of Naval Research.]
Ray Progress in a Stochastic Layered Medium
Authors: Lord Norman W.
Published: October 2005

A modified Monte Carlo procedure has been used to study the effects of random variation in a stratified sound-velocity structure upon sound rays passing through turning points. To represent the medium, a stack of many thin isovelocity layers are established with considerable overlap between the ranges of velocity variation in successive layers. To choose the variates, a pseudorandom sequence of numbers is generated in such a way that at each layer the finite ensemble of rays is angularly distributed like the infinite ensemble. Comparison tests on subgroups in an ensemble of 4224 rays show how representative the small ensemble can be. In sound channels of the most common velocity structure, the interaction of velocity gradient and variance (missing from the classic Chernov treatment) lead to the preponderant ray spreading taking place at the thermoclinic turning points. The various statistical details for short- and long-range ray paths show good correlation with experiments on fixed-distance transmission-time fluctuation.
Response Characteristics of Kangaroo Rat Cochlear Nucleus Neurons
Authors: Moushegian George , Rupert Allen L.
Published: October 2005

In a preliminary study [J. Acoust. Sac. Amer. 41, 1585(A) (1967)], we reported that neurons of this aggregate could be tentatively categorized as “frequency followers” and “non-frequency followers” to low-frequency acoustic stimulation. In the present studies, of over 300 neurons, data are presented to categorize further the activity of cochlear nucleus neurons. Each of these neurons was stimulated by representative frequencies and intensities throughout its response area. Short duration tones, 200 msec, and continuous stimulation, 30 sec, were used. The data are presented in PST, interval, and rate format. Analyses of these data indicate not only qualitative principles but quantitative ones for this nuclear aggregate. [This work was supported in part by National Institute of Neurological Diseases and Blindness and the National Science Foundation.]
Single Auditory Units Recorded in the Medial Nucleus of the Trapezoid Body (MNTB) of Anesthetized Cats
Authors: Guinan J. J. , Guinan S. S. , Norris B. E.
Published: October 2005

We classified 392 Superior Olivary (SOC) units using physiological criteria and independently determined their locations. Of 169 MNTP units, 120 were in a single class characterized by a distinctive spike waveform (Pfeiffer, Science 154, 667). All 127 units in this class (except one) were monaural (contralateral excitatory), had firing patterns similar to auditory-nerve fibers, had short click latencies relative to (other SOC units, were located near calyces of Held, and were tonotopically arranged with higher best frequencies more ventromedial. Sixteen MNTB units responded like the above units but lacked the characteristic spike waveform and were placed in a different class. Twenty-three MNTB units were in a class characterized by an “OFF response” to contralateral stimuli. None of the 35 units in this class showed spontaneous activity or was located far from the MNTB. The 10 remaining MNTB units were distributed throughout five other classes. [Supported by NIH grants and the Joint Services Electronics Program.]
Scalp Responses from Human Subjects Evoked by Contingent Noise Bursts
Authors: Teas D. C. , Nielsen D. N. , Idzikowski R. P.
Published: October 2005

Subjects were seated comfortably in a soundproof room, cup electrodes were attached to vertex and earlobes, and earphones were carefully placed. One-hour experimental sessions were divided into four stages: Passive, Anticipation, Bisection, Passive. For Passive, S heard a 150-msec noise burst (40 dB SL) at the midpoint of a 2-sec interval that was marked off by 150-msec light pulses. For Anticipation, S pressed a response button at midpoint, contiguous with the onset of noise burst. Bisection, divided into three subconditions, also required a button press by S at midpoint. In Bisection1, allowable error for correct button press was ±150 msec around midpoint; for Bisection2, ±106 msec; for Bisection3, 75 msec. A noise burst followed correct bisections by 500 msec to inform S of correct presses and also to evoke a scalp response. Averaged response waveforms (6⩽N⩽12) and waveforms of single responses show greater amplitude for Bisection than for Passive. There may also be additional components in the response following correct bisections. [This research was supported in part by the National Institutes of Health.]
Estimating the Intelligibility of Continuous Discourse
Authors: Speaks Charles
Published: October 2005

Performance on a synthetic sentence identification (SSI) task was compared with data from Hawkins and Stevens (1950) for continuous discourse. First, the relation of speech level to noise level for an SSI performance criterion of 50% correct response was determined. This function then was compared with similar functions representing the thresholds of intelligibility (TI) and detectability (TD) for continuous discourse. The SSI function lies approximately midway between TI and TD for continuous discourse. When the Hawkins and Stevens definitions of threshold were applied to SSI data, TI for continuous discourse corresponded to approximately 99% and TD to 5% performance for SSI. Masked thresholds of intelligibility for continuous discourse can be estimated accurately by determining the lowest level at which a listener can perform the sentence task without error. The close correspondence suggests that when intelligibility of continuous discourse is difficult to quantify, reasonable estimates can be gained from other test materials if the gain functions are parallel to those of continuous discourse for a given experimental condition. [Supported by Graduate School, University of Minnesota, and by the Vocational Rehabilitation Administration.]
Diver-to-Diver Speech Intelligibility of Underwater Communication Systems
Authors: Hollien Harry , Coleman Robert F.
Published: October 2005

The purpose of this research was to evaluate speech intelligibility of underwater diver-to-diver communication systems. To accomplish this, a second DICORS was designed for two diver/listeners, who could respond to speech produced by a diver/talker situated in the original DICORS. The research was conducted in 30 ft of water at NRL's Underwater Sound Reference Division's Bugg Springs facility. Speech materials consisted of Clarke multiple-choice lists; responses were recorded on an IBM keypunch, at the surface, coupled to specially constructed multiple-choice response switches activated by listeners. Five experienced diver/talkers and up to eight experienced diver/listeners (the average talker/listener totals were 36) were situated 30 ft apart and back to back. All systems evaluated were rigged with the Bioengionics “Nautilus” muzzle and a double hose regulator. Several units could not be kept in operation, however, and that equipment could not be evaluated. Mean scores for the other four units ranged from 57% to 64%. Our scares are higher than those previously reported for these units under diver-to-surface protocols; however, they probably reflect (1) experience with this type of research of both talkers and listeners, (2) the use of multiple-choice word lists (which elevate scores) instead of PB25 word lists, and (3) use of the Nautilus mouthcup and a double hose regulator (which has been shown to be the optimum available support configuration). In any case, it can be concluded that (1) while reasonably good diver communication systems are available, they are not yet of sufficient quality to allow for adequate underwater voice communications, and (2) no single approach (modulated, hardline, acoustic) is currently superior to the others. [This research was supported by Physiological Psychology Branch of the Office of Naval Research.]
Long-Wavelength Acoustic Holography
Authors: Graham Thomas S.
Published: October 2005

To date, acoustic holography has been used as a means of acoustically imaging objects. Since faithful imaging requires short wavelengths, interest has centered on ultrasonic holography. The idea of this paper is to show that acoustic holography using long wavelengths (several centimeters or more) is a valuable tool for studying acoustic phenomena. In the experiment described, the acoustic wavefront radiating from a thin plate vibrating in air is reconstructed optically. At the test frequency of 9800 Hz, the plate is vibrating below coincidence frequency, i e., the bending wavelength in the plate is shorter than the wavelength in air. The holographically produced real optical image of the plate shows that the edge of the plate and the point of excitation are the principal contributors to the farfield sound pattern. This image is the first direct experimental evidence of the “edge-effect” and “force-distortion” radiation previously predicted theoretically. Other specific applications of long-wavelength acoustic holography are discussed, along with some of the difficulties encountered in the experimental work.
Method for Measuring the Surface Impedance Presented by a Smooth Surface to a Sliding Indenter
Authors: White James V.
Published: October 2005

The electrical driving-point admittance of a linear transducer is linearly dependent on a sufficiently small impedance loading its mechanical port (a sufficiently small load impedance is one that is much smaller than the transducer's mechanical driving-point impedance). This makes possible a method for measuring the mechanical impedance presented by a smooth surface to a sliding indenter. The indenter acts as the mechanical port of a transducer whose electrical admittance causes the output voltage of a linear active network to equal the surface impedance in amplitude and phase. Calibration of the system does not depend on a detailed knowledge of the transducer's dynamics, but does require that the transducer be operated at frequencies for which its mechanical impedance is much larger than the surface impedance. This method has been used to measure groove impedances of phonograph records.
Constructional Principles for Bow Instruments Applied to Violino Grande, the Five-Stringed New Member of the Violin Family
Authors: Hansson Hans Olof
Published: October 2005

Constructional principles based on simple and well-known acoustical and mechanical laws and precision handcraft based on careful measurements are of great importance in the production of new bow instruments in order to achieve good resonance and equalization over the whole register and to compensate for much of the effect of the aging qualities observed on old bow instruments. Principles concerning thickness distribution of the plates, dimensioning and placing of the bass bar and sound post, and so on will be described. It has many times been suggested that the old Italian masters used a pore-filling primer to prevent the vanish itself from penetrating the wood. This primer has been identified by paper chromatographic methods. Such an analysis of a sample from a Hill certified old Italian violin will be described and some conclusions drawn. This primer seems to be of more importance to the tonal qualities than the varnish itself. [Research supported by His Majesty Gustaf VI Adolf, King of Sweden.]
ROC Curves Determined under Several Experimental Conditions
Authors: Leshowitz Barry
Published: October 2005

ROC curves for detection of 1000-Hz sinusoids presented against a background of narrow-band noise were obtained using a one-interval rating-scale procedure. Signals were added to noise alone (simple detection) or to noise plus sinusoidal pedestal (pedestal detection). While almost all stimulus-oriented theories of signal detection predict a monotonically decreasing relation for the slope of the ROC curves as a function of signal strength, slopes of the empirically determined ROC's never showed a systematic decrease with increases in signal amplitude. Two modifications of the basic energy-detection approach, a fluctuating criterion model and a neural counting scheme, are proposed to account for the data. Implications of the theoretical and empirical results for notions about the nature of the underlying probability distributions and decision mechanisms are discussed. [Research supported by the National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare.]
On the Effects of Stochastic Boundary Perturbations on Acoustic Wave Propagation
Authors: Bugnolo Dimitri S.
Published: October 2005

A theoretical procedure is developed in an effort to solve the acoustic propagation problem in the ocean in the presence of stochastic boundaries. This theory is believed to be an improvement over past efforts that treated the surface as a separate problem. My result for the mean or mean-squared potential function can be used to calculate the effects of a stochastic surface including mode coupling, attenuation, scattering into a shadow region, etc., without recourse to the approximations of past theoretical efforts. While this theory is complex in structure, it is my opinion that the difficulties are justified in that less is neglected. The usual plane-wave surface scattering theories may suffice in certain applications; however, it is evident that they must be used in conjunction with ray tracing. A mode theory is a step in the right direction in that the limitations of the ray theory are overcome.
The Bowed String
Authors: Schelleng John C.
Published: October 2005

Primarily from the point of view of the player, the various aspects of the behavior of the bowed string will be considered: the form of its vibration, the parameters of bow position, velocity, and “pressure”; maximum and minimum pressure and their relationship to tone production, starting conditions, efficiency of the “stick-slip” process as a generator, and effects of stiffness in the string. Some observations of particle velocity made by electromagnetic pickup along the string will be shown, along with measurement of the spectrum; and the recorded sounds evoked by cello strings alone, without the corpus of the instrument, will be compared with those from the normal cello.
Research Potentials in Auditory Characteristics of Violin Tone
Authors: Boomsliter Paul C. , Creel Warren
Published: October 2005

The science of musical sounds arose from development of methods of measuring regularities in the physical stimulus. The ear was regarded as a passive transducer, but the ear is not a passive transducer. It is a system that actively processes stimuli and gains information from irregularities, producing the acoustic effects that we call “richness” and “quality,” and like names. To move forward in understanding the violin, we must turn from analysis of its steady states to examination of changes taking place in real time. The violin is noteworthy in that the slip-stick action of the bowed string combined with bowing techniques not only produce irregularities but place their control in the right hand of the player as violin fingering produces irregularities controlled by the left hand. It may well be that the difference between a good violin and a great one cannot be found in any steady-state quality but in its responsiveness to change willed by a great player who exploits that responsiveness to add additional and meaningful irregularities and relationships to the broad pattern of a musical composition.
Acoustic Properties of Wood
Authors: Sakurai Yoshimasa , Skudrzyk Eugen J.
Published: October 2005

A square redwood plate was progressively cut, removing crossgrain and longitudinal-grain strips, with simultaneous acoustic measurements made of strips (beams) and plate. Findings show that regions near the ends of a free beam or plate do not contribute to losses. Thus damping of a beam vibrating in its fundamental is almost 50% smaller than in a long beam vibrating at the same frequency in an overtone. As frequency increases, the free ends act like rigid (mass) clampings, increasing the resonant frequency relative to values predicted by elementary theory. Because of shear, effective bending stiffness decrease with a frequency rate inversely proportional to the shear modulus (deduced from Timoshenko correction). Since shear modulus is small for crossgrain vibrations, their loss factor is identical to that of shear modulus; whereas damping parallel to the grain in goverened by the loss factor of Young's modulus. Vibrational properties, therefore, depend on properties of the material, on size and shape of the vibrator, and direction of nodal lines relative to grain structure—important factors in muscial instrument construction that are also applicable to fiber shells and somewhat to isotropic vibrators. [Work sponsored by the Ordnance Research Laboratory under contract with U. S. Naval Ordnance Systems Command.]
Time-Intensity Trading Ratios for Narrow-Band Transients
Authors: Zerlin Stanley
Published: October 2005

Narrow-band clicks (approximately 200 Hz wide) with center frequencies of 250, 1000, 4000, and 6300 Hz were given to three experienced listeners at interaural intensity differences (ΔI) of 3, 6, and 9 dB. A reference sensation level of 30 dB was used throughout, and listeners asked to center the click image with an opposing time difference (Δt). Although two ranges of compensatory time (Δt) could often center the image only the smaller times were considered. Trading-ratio slopes for the four transients, in order of increasing click frequency, were: 25, 20, 50, and 40 μsec/dB. Increasing the click bandwidth around the same center frequencies (while maintaining the sensation level constant at 30 dB) did not significantly affect the trading ratios. The trading-ratio results will be compared to some lateralization (jnd) data for time and for intensity to see whether both kinds of data indeed reflect the same underlying process.
Binaural Signal Detection: Independent Signals in Each Channel
Authors: Sorkin R. D. , Pastore R. E.
Published: October 2005

An experimental technique described by Eijkman and Vendrik [“Can a Sensory System be Specified by Its Internal Noise?,” J. Acoust. Soc. Amer. 37, 1102–1109 (1965)] is applied to a binaural task involving the detection of simultaneous signals in both ears. In the first observation interval of a modfied 2AFC task, a tone burst Vo is presented to each ear. In the second interval, one of four random events occurs: (1) the tone burst Vo is present in each earphone, (2) Vo is in left, Vo+ΔV in right, (3) Vo+ΔV in left, Vo in right, or (4) Vo+ΔV presented in both phones. The observer is to report which of the four events occurred. Uncorrelated noise is continuously present in each earphone channel. Comparison conditions were run in monaural and Sm-Nu versions of the binaural task. Analysis of the data includes consideration of the facilititative-inhibitory interactions between the channels, and the computed between-channel correlation. For example, hit and false-alarm probabilities in each channel are examined in terms of their dependence on signal and response conditions in the other channel. The results are interpreted in the context of binaural masking and contralateral cueing phenomena.
Monaural Detection with Contralateral Cue (MDCC): Masking the Cue
Authors: Taylor M. M. , Smith S. M.
Published: October 2005

At the last three meetings of the Society, we have described MDCC experiments with unmasked cues. When the signal (and therefore the cue) is a sinusoid of frequency below about 1100 Hz, the cue may either aid or detract from the detection of the monaural signal. The direction of effect depends on the phase difference between the signal and the cue. As the cue is made louder, performance at bad phase drops steadily; but over a wide range of cue intensities, performance at optimum phase is near that of the signal-known-exactly (SKE) observer. However, performance drops drastically for very loud cues whether the phase is good or bad. In this paper, we consider the effect of masking the cue. If the detrimental effect of the loud cue at all phases were due simply to “contralateral masking,” adding more noise should further reduce performance. If, on the other hand, the loud cue provides some sort of misinformation to the detector, cue masking should improve performance. The latter proves to be the case; the masked cue acts like a softer cue.
Optimum Configuration for Damping by Constrained Viscoelastic Layers
Authors: Plunkett R. , Lee C. T.
Published: October 2005

Viscoelastic materials are extensively used to damp flexural vibrations of metallic structures; it has been known for some time that the energy dissipation due to shear strain in the viscoelastic layer can be increased by constraining it with a stiffer covering layer. In this report, we discuss a method for increasing this damping by cutting the constraining layer into appropriate lengths. The analysis for a single layer of this treatment is relatively straightforward. The damping can be increased still further by using several layers; in this case, the analysis is based upon effective complex elastic moduli of an equivalent homogeneous medium. One result found from this analysis is that, for optimum spacing of cuts, the damping depends primarily upon the stiffness of the constraining layer and only slightly on the shear modulus of the viscoelastic layer. Experimental data are presented for comparison with the theoretical predictions.
Acoustic Lining Concepts and Materials for Engine Ducts
Authors: Mangiarotty R. A.
Published: October 2005

The requirement for attenuating engine fan noise is summarized. The inlet and duct environment to which linings are exposed in a typical turbofan engine and the noise spectrum to be attenuated are reviewed. Concepts of acoustic linings and their mechanisms for attenuating the propagation of sound in ducts are discussed with particular application to turbo-machinery. The procedure used for screening and selecting suitable acoustical facing materials for linings is discussed. This is followed by a summary of the experimental methods used for this procedure to obtain the specific flow resistance, specific acoustic impedance, and the acoustic absorption coefficient. Suitable materials were evaluated as part of duct linings using a laboratory flow-duct apparatus in which linings were subjected to sound levels up to 155 dB over-all SPL and airflows up to Mach number 0.4. Parametric studies are then discussed showing the important acoustic and geometeric characteristics that influence the acoustic attenuation of linings. A comparison is made of the attenuation of linings obtained in the flow duct and in a full-scale engine. The acoustic materials evaluated in the study are reviewed. Finally, a description is given of a theoretical method developed for predicting the attenuation of linings, and compared with experimental measurements.
Structural and Environmental Studies of Duct-Lining Acoustical Materials
Authors: Watson H. A.
Published: October 2005

The development of an aircraft noise-suppression system is essential to the relief of communities adjacent to commercial airports that are adversely affected by jet-aircraft noise. This paper is a brief review of the structural aspects of current turbofan noise-suppression designs presented in conjunction with a summary of the environmental conditions that determine the design criteria of duct-lining materials. Also included are: (1) prospective drawings of the various acoustical sandwich configurations; (2) descriptions of the porous sheet, honeycomb core, and adhesive materials that compose the composite configurations; and (3) a discussion of the special structural and evironmental tests required to develop the mechanical properties of acoustical materials.
Ultrasonic Modulation of Gamma Rays
Authors: Marshall S. W. , Diederich D. P.
Published: October 2005

We have observed the results of ultrasonic modulation on gamma rays in a Mössbauer effect experiment of the type first reported by Ruby and Bolef [Phys. Rev. Letters 5, 5 (1960)]. This modulation may be viewed classically as the phase modulation of an electromagnetic wave whose carrier frequency is that of the gamma ray, in this case 3.48 × 1018 Hz. In their work, the modulation at 20 MHz was effected by a quartz resonator, and they obtained a Mössbauer velocity (frequency) spectrum consisting of a central absorption line plus sidebands at frequencies both lower and higher than that of the central line. To extend their results to higher modulation frequencies, we deposited directly on the stainless steel Mössbauer absorber a CdS film transducer, which was driven at frequencies up to 500 MHz. Gamma rays from a 20-mCi Co57-in-stainless steel source passed through this absorber and were detected in a gas-filled proportional counter. The effect of this ultrasonic modulation was revealed by the appearance of the first sidebands in the Mössbauer spectrum at 3.48 × 1018 ± 4.45 × 108 Hz.
Method for Measuring Phase Shifts at Ultrasonic Frequencies
Authors: McSkimin H. J.
Published: October 2005

The frequency of a stable oscillator is periodically offset a small amount, then restored to its original value. The resulting change in phase of the oscillator output with respect to its original value can conveniently be related to the average voltage of a dc pulse generator that produces the frequency offset. For application to the ultrasonic pulse-echo method, phase shifts for a selected echo can readily be measured by using the oscillator output as a calibrated phase reference. Two circuits for doing this are described. Several desirable features of the method are: (1) phase shift is measured at a fixed frequency; (2) no mechanical parts are required; (3) phase can be varied continuously over a wide range, with essentially linear calibration; (4) application to measurements at high frequencies can be made. By way of illustration, some results are listed in connection with measuring the shear mechanical properties of dibutyl phthalate at 100 and 300 MHz.
Perstimulatory Shifts in the Difference Limen for Frequency
Authors: Bilger Robert C. , Feth Lawrence L. , Jesteadt Walter H.
Published: October 2005

The frequency difference limen, as estimated from listener control of the amplitude of the 2-Hz input to a frequency modulator, was observed to have an unusual time dependence at high sound levels. To explore this perstimulatory effect, six listeners were asked to track Δf for the initial and final 2 min of an 8-min exposure. During the middle 4 min, the frequency modulator was turned off and the listener heard an unmodulated pure tone. This experiment was conducted at four levels (37, 57, 77, and 97 Db SPL) of three frequencies (300, 1000, and 3000 Hz). Results show a strong perstimulatory effect, which always was an improvement in Δf, from the initial to the final tracking period, by approximately two to one. This effect, however, was greatest at low levels for 300 Hz but greatest at high levels for 3000 Hz. At 1000 Hz, improvement was minimized at the intermediate levels and greatest at the extremes. These results are discussed in terms of learning and of adaptation of the ear. [Supported by a grant from NINDB, National Institutes of Health.]
Threshold Improvement (Negative Threshold Shift) Following Exposure to Dental Drill Noise
Authors: Gerstman H. L. , Reddy R. P.
Published: October 2005

In a pilot investigation of dental drill noise as it affects the hearing thresholds of children and dental operators, it was found that pure-tone thresholds improved (NTS) following an operative procedure when evaluation utilized continuous-tone Békésy audiometry. In a full-scale investigation, TTS's were found under the same conditions as the pilot study when pulsed-tone stimuli were used. Continuous-tone investigation was reinstated and NTS was again elicited. The reliability of the subjects was established through test-retest at 500 Hz. Exposure time for each subject and lapsed time between the end of exposure and the onset of testing were recorded. This paper examines the procedures of the investigation and the possible explanations accounting for the discrepancy between pulsed and continuous-tone Békésy conditions. Results of the primary investigation indicated that patients did not appear to be subjected to more intense (or different) exposure relative to the operators and that “high-speed” drill-noise exposure, for the duration encountered, is relatively “safe” with regard to patient PTS. [This work was supported in part by Social and Rehabilitation Service of US, DHEW, Research and Training Center No. 7, Tufts University.]
Earmold Influence on Aided Speech Identification Tasks
Authors: Northern Jerry L. , Hattler Karl W.
Published: October 2005

The physical characteristics of hearing aids are modified when the instrument is coupled with an earmold and fitted to an ear canal. This study was undertaken to compare the electroacoustic characteristics of four specific earmold variations with behavioral speech audiometric tasks in five normal-hearing and seven sensorineural-hearing-loss subjects. Speech-Békésy thresholds were obtained under each earmold condition with continuous discourse for detectability, intelligibility, most comfortable loudness, and tolerance. Speech discrimination ability was evaluated with the Modified Rhyme Test in three signal-to-noise ratio conditions. Significant differences in test scores attributable to earmold modification were difficult to demonstrate, in spite of the fact that substantial variations in the ear inserts were readily apparent in both structural and electroacoustics analysis. Clinical implications of earmold effect on hearing and performance are discussed.
Real-Time Digital-Cepstrum-Pitch Extraction on a 12-Bit Machine
Authors: deLellis Joseph , Freudberg Richard L. , Howard Calvin R. , Manley Harold J. , Shaffer Harry
Published: October 2005

This paper describes a digital cepstrum-pitch detector designed to work in real time on a 12-bit binary machine. Spectrum and cepstrum analysis of raw speech data is accomplished through the use of a single complex Fast Fourier Transform (FFT) algorithm. Pitch detection is accomplished by a cepstrum-peak scanning logic designed to locate the position of a peak corresponding to the pitch period. Since other peaks may exist in the data, logic is required to differentiate these peaks from the desired one. Because of the limited word size of the machine, special processing algorithms were developed to perform logging and to avoid the squaring of variables. Various logical operations performed on the spectrum and cepstrum functions in voicing detection and in the extraction of pitch are presented and discussed. A demonstration of the performance of this pitch detector when operated with a 2400-bit/sec digital vocoder will be presented by means of a tape recording. [Work supported under contract.]
On-Line Evaluation of Three HeO2 Speech Unscramblers
Authors: Hollien Harry , Malone James
Published: October 2005

The purpose of this project was to evaluate the improvement in speech intelligibility levels provided by three HeO2 “unscramblers” developed for the Navy. It is well established that a talker in an environment of high helium concentration and under high ambient pressure experiences severe distortion in the intelligibility of his speech. The three devices investigated consist of electronic circuitry that essentially attempts to return the speech formants—that have been shifted upward on the frequency continuum—to their normal regions. The site of the project was one of the multiple-room compression chambers at the Experimental Diving Unit, Washington Navy Yard; a special 2.5-day “communications” dive (12 days over-all) was scheduled for this purpose. Since the reason for these evaluations was to provide data on the units prior to their use in Sealab-3, the experiment was carried out at 600 ft (slightly in excess of 19 ATA) in a helium/nitrogen/oxygen breathing mixture of 92.4%/6.0%/1.6%, respectively. Talkers were four Navy divers in training for Sealab; the speech material consisted of PB25 word lists. Recordings were made on a Honeywell 8100 FM tape recorder that simultaneously recorded the unprocessed speech and the output of the three unscramblers situated on line. Listeners were (at least) 10 University of Florida students trained for tasks of this nature. Intelligibility data are reported for the following conditions: (1) when the divers reached the experimental depth, (2) after two days at saturation depth, (3) for two different microphones, and (4) for two underwater communication rigs used in the chamber's wet pot. Over-all results indicate that, while substantial improvement in intelligibility levels was afforded by the use of the speech processing systems evaluated, such improvement was not sufficient to provide good voice communication with individuals under the HeO2/ambient pressure conditions studied. [This project was supported by the U. S. Navy Deep Submergence Systems Program and by the Physiological Psychology Branch of the Office of Naval Research.]
History of International Standardization in Mechanical Vibration and Shock
Authors: Muster D.
Published: October 2005

Any history of International Standards Organization Technical Committee 108, “Mechanical Vibration and Shock,” must include the significant contributions of Dr. Irwin Vigness, especially in the formative years of the Committee. In this paper, the history and current status of the work of ISO/TC 108 in mechanical vibration and shock is reviewed. The relationship of this technical committee with other related activities in the ISO and IEC are also described.
Are We Going the Right Way?
Authors: Angeluscheff Z. D.
Published: October 2005

Protection and promotion of the faculties given to man by Nature and his destiny must be the primary consideration of science. This was my answer to the referendum of the Academy of Sciences on the occasion of its 150th anniversary jubilee. Acoustics, which refers primarily to hearing, in its zeal for progress, has become the enemy of hearing. The decibel is its darling. Technology today adds decibels and promotes deafness and mental illness among the people. Industrial and aviation noise intrudes into homes and exerts a deleterious effect upon human hearing and upon the nervous system. A population not exposed to noise, the natives of Morocco, the Congo, Sudan, can perceive frequencies as high as 28 000 Hz and more. Middle-aged population in Long Island, New York, an area highly infested with aviation noise, can hardly perceive 8000 Hz; a pilot after long duty, 4000 Hz. The decibel has reached the acme, 140–160 dB, with supersonic boom, and we are committed with it. When supersonic flying became a reality, the phenonenon of the sonic boom was discovered because people heard it, reacted to it with surprise, and wondered about its source. A study (Physics Today, 1968) attempted to prove the damage of sonic boom as superficial, and due to dehydration and poor workmanship. Could the same cause be blamed for the damage of New Air Force Academy in Colorado Springs, at its dedication, where more than 200 windows were shattered and many participants injured. When the supersonic transport comes into business, it will be too late.
Form of Equal-Attribute Contours for Predicting Subjective Response to Noise
Authors: Parry Hugh J.
Published: October 2005

The form of the equal-attribute contour used for predicting subjective response to noise has a pronounced effect upon the accuracy of the prediction. A number of such equal-attribute contours are presently in existence. These include equal loudness and equal noisiness each in several forms as determined by different investigators or by the same investigator under differing conditions. Forms of loudness contours have been determined by Stevens, Zwicker, Fletcher and Munson, Robinson and Whittle, and Parnell, Nagel, and Parry; and equal-noisiness contours by Wells, Stevens and Kryter, Kryter and Pearsons, and Parnell et al. The differences in the forms of each of these is discussed and described. The effect of these differences on accuracy of predictions of subjective judgments is considered from the standpoint of spectral content of the stimuli and frequency ranges of the differences in the contour forms.
Computation of Perceived Noise Level
Authors: Wells R. J.
Published: October 2005

Details of a modified method for computing perceived noise level are presented. Statistical studies of jury-test results show that the modifications lead to a significantly improved prediction. Early results of this study were presented at the Sixth International Congress on Acoustics in Tokyo and at the Miami meeting of the Acoustical Society of America.
Further Study of the Operational Definitions of Loudness Level and Perceived Noise Level
Authors: Mabry J. E. , Cohen V. V. R. , Little J. W.
Published: October 2005

The operational definitions of loudness level and perceived noise level are similarly expressed. “The Loudness Level (or Perceived Noise Level) of a sound is equal to the Over-all Sound Pressure Level of a standard band of noise judged to be equally loud(noisy).” This paper presents the results of a study designed to test the accuracy of these statements, and to provide further information on the differences between judged loudness and judged noisiness as separate attributes of sounds. The different calculation methods were studied. Eighteen subjects were required to match two sounds on the attribute of loudness, and 18 subjects on the attribute of noisiness. Various noise spectra were used at levels between 73 and 99 dB. The results indicate that loudness and noisiness are the same attributes of sounds of the types studied. A third calculation procedure was also tested, and results will be presented.
Status Report on the SAE R-6 Research Committee
Authors: Parry Hugh J. , Little John W.
Published: October 2005

The R-6 Research Committee of the Society of Automotive Engineers was organized in February 1968 for the purpose of developing an accurate subjective reaction rating scale for complete aircraft-noise flyover cycles. The committee has completed the first part of a 2-year research project that includes considerable experimental activity. This report describes the work performed to date and the plan for the remaining program. In the past, individual investigators in the field of subjective reaction to aircraft noise have developed a variety of rating methods. However, it has become increasingly clear that these have limited reliability. With the formation of the R-6 Committee, six laboratories working in this general field have formed a cooperative organization to remedy this problem. The committee has developed a detailed research plan that will result eventually in a reliable subjective reaction rating scale for aircraft noise. In addition to this long-range plan, the committee has assembled descriptions of each participating test facility, has retained individual and laboratory consultants, has conducted a comprehensive acoustical calibration of each laboratory, and has completed some preliminary judgment tests.
Computerized Noise-Measurement System
Authors: Kapuskar Wisu T.
Published: October 2005

Evaluation of noise is acquiring such importance that a symposium entitled “Where Do We Stand on Standards for Noise?” was devoted to it at the 76th Meeting of the Acoustical Society of America. With the increasing complexity of procedures being adopted (e.g., International Organization for Standardization Recommendation R507 on Procedure for Describing Aircraft Noise Around an Airport), a stage has been reached where the use of a low-price instrumentation computer in the measuring system seems to be an optimum solution. Such a system is not only capable of preforming measurements according to a complicated procedure (the system being described evaluates tone-corrected perceived noise levels according to ISO Recemmendation R507 at half-second intervals on a real-time basis), but it is also easily adaptable to changes in the procedure itself. A single system can handle different measurements (A, B, C, and D weighting, Steven's method, SAE sones, Noise and Number Index, long-term integration, just to mention a few). Programming for individual applications is easy. Such a system is ideal for monitoring and control. Other applications will be briefly described.
Ultrasonic Propagation in High-Temperature Gases
Authors: Uva S. , Carnevale E. H. , Carey C.
Published: October 2005

An ultrasonic pulse method (1 to 3 MHz) has been used to measure both sound speed and absorption in monatomic and polyatomic gases in a temperature range of 300° to 20 000°K and at atmospheric pressure. In monatomic gases in a temperature range where no ionization occurs, the ultrasonic technique described may be used to determine shear viscosity and thermal conductivity. In nitrogen and oxygen, in the range of 5000° to 10 000°K, relaxation times due to the excitation of bound electrons have been determined. In argon at T>8000°K, the effects of ionization and radiation on sound propagation are investigated. The temperatures were calculated from theoretical temperature-sound-velocity relations. The main emphasis of this work is to determine experimentally the acoustic properties of gases at elevated temperatures and to then relate these properties in terms of various relaxation mechanisms—including, for example, excited electronic states, ionization, and radiation. For all the gases investigated, the usefulness of ultrasonics to obtain previously unknown quantities will be discussed.
“Free-Field” Tube for Perturbed Propagation Measurements
Authors: Sachs Thomas D.
Published: October 2005

A tube geometry and acoustic burst time scale is described that avoids the interference with perturbed propagation parameter measurements caused by the diffraction patterns due to wall reflections in tubes. It is shown that the normal mode picture is inadequate to describe burst propagation in bounded systems. Also, a causality paradox results from using a one-dimensional model of a laterally bounded propagation situation. The insight gained from these considerations leads to a ray picture that is utilized to design a “tube” not subject to the usual difficulties. Construction details and methods are given. Measurements with the system indicate that it approaches a free-field situation in a confined space. [Work supported in part by the National Science Foundation.]