bluuebunny/crossref_metadata_2025 huggingface dataset:
Doppler effects for randomly moving scatterers and platforms
Authors: Middleton David
Published: October 2005

Almost all earlier and current studies of scattering from random moving media and interfaces (and platforms) fail to provide proper treatment of the ensuing Doppler phenomena. This occurs apparently bemuse of failure to recognize that the scattering elements act like moving sources of reradiation (Hugens's principle with moving sources), where now the Langevin equations of propagation must be suitably “Dopplerized” to account for not only the kinematic but the physical, dynamical effects of wave and particle motion. For the usual far-field, small-Doppler cases (with scatteres and platform velocities weakly dependent at most on location), it is shown that this “dynamic” Doppler produces (on finite time intervals) a nonstationary frequency (or equivalent phase) modulation (FM) of the initial signal. (After sufficient time from initiation, the Doppler FM becomes essentially stationary, provided the scattering mechanism is likewise.) This FM is in addition to the familiar (stationary) phase modulation produced by the random spatial location of the (moving) scatter elements, in time, which has erroneously been said to produce “Doppler” frequency spreading. The discussion is illustrated with an example from scattering by random, moving ocean surfaces. [Work supported primarily by the Naval Sea Systems Command.]
Asymmetric Doppler amplitudes in the surface scatter channel
Authors: Tuteur F. B. , Tung H.
Published: October 2005

The generation of asymmetric Doppler sidebands in scatter channels in which the transmitter and receiver are at different depths has been demonstrated in several recent papers [E. Y. Harper and F. M. Labianca, J. Acoust. Soc. Am. 57, 1044–1051 (1975); 58, 349–364 (1975)]. In these papers the wave equation was solved by using a perturbation procedure. In the present paper a similar result is obtained by using a modified Fresnel expansion of the Kirchoff integral. The resulting expansion, which is correct to third order but contains only terms up to second order is then easily manipulated by standard methods. If the source and receiver are located in the xz plane at points (0, z0) and (x1, z1), respectively, and if the surface motion is along the x axis, the ratio of side-band amplitudes is approximately exp [(4p/k) (z02 − z12)/(z03 + z13)x1] where 2π/p is the surface wavelength and k is the acoustic wave number. Other geometries and surface models are also easily computed. [Supported by ONR, Code 480.]
Sound scattering from a fluid sphere revisited
Authors: Johnson R. K.
Published: October 2005

The fluid sphere model is compared with scattering models for a free gas bubble in water and for the gas-filled swimbladder of a fish. The parameters discussed are frequency response and resonant frequency. The fluid sphere model is also used to predict scattering from euphausiids and copepods.
Reflection of sound from layered elastic absorptive cylinders
Authors: Flax L. , Neubauer W. G.
Published: October 2005

The reflection of plane waves by a layered cylindrical shell in water is investigated theoretically. Either or both of the two layers of elastic material may be absorptive. The solution as a function of frequency is examined for several combinations of inner and outer layers.
Higher order diffraction into the shadow zone
Authors: Hudimac A. A.
Published: October 2005

In former work, ray theory has been extended to account for diffraction into the shadow zone by a suitable distribution of simple sources and or dipoles over the shadow boundary. This is a first-order correction because rays from a point on the distribution also produces a shadow zone. The correction due to the whole first-order distribution leads to a volume distribution of simple sources. Each successive order of diffraction leads to another volume distribution. The theory is applied to the diffraction of sound through a plane screen with a circular aperture for the cases of complete absorption and complete reflection. Calculations for the latter case are compared to those obtained from wave theory. [Work supported by ONR.]
Asymptotic grazing field on a locally excited, homogeneous, fluid-loaded thin plate
Authors: Sachs D. S. , Berkman E. F. , Barger J. E. , Smith P. W.
Published: October 2005

The usual asymptotic descriptions of the field radiated from locally driven fluid-loaded plates fail at grazing (observation point on or very near the plate). Higher-order asymptotic procedures are described which yield a closed-form expression for the grazing field. The result can be interpreted by noting that the effect of the plate is the same as that of a layer of fluid of mass equal to the plate mass; the gazing field is analogous to the field (in the source plane) of the resulting Lloyd mirror problem. Grazing field solutions are also developed for plates coated with a compliant layer. It is found that the layer is more effective in reducing the grazing field than the radiated far-field.
Cochlear injury from tobramycin and other aminoglycosides in guinea pigs
Authors: Hawkins J. E. , Marques D. M. , Clark C. S.
Published: October 2005

Cochlear toxicity of tobramycin was compared with that of four other aminoglycosidic anitbiotics. Small groups of guinea pigs received tobramycin (TM), gentamicin (GM), neomycin (NM), or kanamycin (KM) in doses of 50 and 100 mg/kg/day subcutaneously for 1–6 weeks; others received KM 200 and 400 mg/kg/day, or dihydrostreptomycin (DHSM) 400 mg/kg/day. Cochlear microphonics were recorded one week after treatment ended, and hair cell losses were plotted as cytocochleograms. Curves relating maximum response (CMmax) to duration of treatment fell less steeply for TM than for GM and NM, but more steeply than for KM. At 200 and 400 mg/kg KM produced moderate or severe deduction in CMmax after 2 weeks. DHSM 400 mg/kg was without effect in 11 of 12 animals treated for 3–6 weeks. Hair-cell losses were roughly consistent with CM levels. In cochleas with only moderate CM loss, inner hair cells often persisted when outer hair cells had disappeared, but with severe CM loss there was also extensive loss of inner hair cells. [Supported by NIH Research Grant NS-05065 and Program Project Grant NS-05785.]
Patterns of hair-cell orientation in the sacculus and lagena of two species of teleast fish
Authors: Popper A. N.
Published: October 2005

The hair-cell patterns in the sacculus and lagena of two Salmonids, lake trout (Salvelinus namaycush) and lake whitefish (Coregonus clupeaformis), were studied with the SEM. The maculae are elogate structures connected to a dense otolith by an otolithic membrane. The saccular hair cells are divided into four groups with all cells in each group having the same general directional orientation. The posterior saccula macula has dorsal and ventral groups while the anterior portion of the macula has anterior and posterior oriented groupings. The lagena in both species has two groups, one oriented dorsally and the other ventrally. In addition there are also smaller numbers of hair cells oriented anterior and posterior but these cells are not organized into clearly discrete groupings. Analysis of cell orientation patterns on the macula, and the overall shape and position of the saccula and lagena maculae, indicates that these salmonidas have hair cells that are positioned to provide good sensitivity to otolith movements in three dimensions. [Work supported by NINCDS.]
Structure and function of the ear in the bat, Pteronotus p. parnellii
Authors: Henson O. W. , Henson M. M.
Published: October 2005

With the aid of chronically implanted electrodes it has been found that the cochlear microphonic (CM) audiogram of Pteronotus is very sharply tuned to a narrow band (100–200 Hz) of frequencies in the 59–63-kHz range. Within this tuned band high amplitude potentials can be elicited by pulses of moderate intensity or by frequency-modulated signals which sweep through the best frequency of the audiogram. With intense brief (10 msec) pulses the cochlear microphonic potential was often low in amplitude while the signal was being presented to the ear. With the cessation of each pulse the CM amplitude rapidly increased to a peak and then slowly decayed. These observations suggest an over-critically-damped system. The basis for this may be the well developed basilar membrane thickenings. Scanning electron microscopic observations have revealed that the configuration of the thickenings in the region of the pars tecta changes markedly in different parts of the cochlea whereas the pars pectinata shows only minor variations in thickness and surface topography throughout the cochlear turns. [Supported by NIH grant NS-12445.]
Brief periods of prenatal auditory stimulation accelerate the hatching of Japanese quail
Authors: Woolf Nigel Keith , Bixby John L. , Capranica Robert R.
Published: October 2005

Many species of precocial ground-nesting birds brood egg clutches whose eggs hatch within a short time of one another. This synchronization of hatching is mediated by acoustic communication between the individual members within a clutch [M. A. Vince, Anim. Behav. 14, 389–394 (1966)]. Audible clicks, which are correlated with the embryo's respiratory cycle, provide the basis for the inter-egg communication. Experiments utilizing synthetic clicks (i.e., very brief, broad-band burst of noise) have shown that the response of embryos to acoustic stimulation is dependent on their gestational age, the duration of the stimulating period, and the click repetition rate. A single very brief (2-h) exposure to auditory stimulation at any point during the final three days of incubation accelerates the hatching of Japanese quail (Coturnix coturnix japonica). The three-day sensitive period includes both prenatal and perinatal stages of incubation. The accelerated embryos do not differ from normal hatchlings in any of the behavioral or physiological measures examined to date. These results provide the first unequivocal evidence that such short-term sensory stimulation can affect the rate of development of a vertebrate embryo. [Supported by NIH NS02675 and NS09244.]
Functional properties of the acoustic laryngeal muscle reflex in echolocating bats
Authors: Jen P. H.-S. , Suga N.
Published: October 2005

When an acoustis stimulus is delivered, not only the middle ear muscles (MEM's) but also tim laryngeal muscles (LM's) contract. These two groups of muscles are activated in a coordinated manner by action potentials from the auditory system. Functional properties of the acoustic LM reflex were electrophysiologically studied with Myotis lucifugus. (1) In terms of electromyograms, the shortest latency of the reflex was 6.2 msec. Its minimum threshold was 50 dB SPL for a pure tone stimulus, but it was 30 dB SPL for an FM stimulus. (2) Tuning curves of single LM fibers had an average Q-10 dB value of 3.1 which was smaller than that of the primary neurons but larger than that of stapedius muscle fibers. (3) The acoustic LM reflex evoked by the vocal serf-stimulation augumented the following reflex for about 70 msec which would be evoked by the returning echo. Then the reflex evoked by the echo suppressed the following vocalization for 180 msec. (4) The acoustic LM reflex may act as a negative feedback loop to stabilize the performance of the vocalization system. [Work supported by NSF.]
Influence of mercurials upon cochlear potentials and Na, K-ATPase of the Stria vascularis
Authors: Ise I. , Thalmann R.
Published: October 2005

Various mercurials were applied by perilymphatic perfusion in the guinea pia. The diuretic mersalyl acid (MA), the nondiuretic p-hydrox-mercuribenzoate (PHMB), and HgCl2 produced profound changes of the endolymphatic potential (EP), the organ of Corti potential (OCP), and the cochlear microphonics (CM). With 1 mM HgCl2, both the EP and the OCP fell to 0 mV within 20 min. Changes were less rapid with PHMB and MA. Only with MA was the decline of the OCP not complete when the EP had reached 0 mV. In no instance did the EP turn negative. The CM were reduced to less than 5% when the EP and the OCP approached 0 mV. The failure of the EP to turn negative is attributed to the simultaneous decline of the OCP, which has been proposed as generator of the negative EP. The complete abolition of the CM is ascribed to the breakdown of both “batteries.” The 50% inhibition point of strial NA, K-ATPase with respect to MA is 8 × 10−6 M, about 5 times lower than its 50% inhibition of the EP. [Supported by NIH.]
Energy balances of flow noise excitations
Authors: Peter Abraham C.
Published: October 2005

The net energy balances of “hydrodynamic” fluctuations in dissipative flow regions add up to zero, since there is no net frictional work implemented upon the surroundings. In contrast, the net work balances of flow noise excitations caused by dissipative fluid motion have a finite contribution through the conversion of the frictional heat input into acoustic excitations of the fluid. The net work implemented by the collapsing disturbance upon the surroundings is exactly equal to the energy of formation of an acoustic wave in a uniform (or zero) velocity field. The energy of flow noise formation varies as a high power of the fluid velocity. In particular, some characteristic values of the velocity exponents when γ = 1.4 are as follows: 8.0 for vanishingly small flow Mach number; 7.92 for M = 0.5; 7.69 when M = 1.0; 6.5 for M = 2.0; and 4.0 for M = 2.6. It is also shown that the total work imparted to the fluid to form flow noise excitations is such, that its maximum efficiency is 6.2% of an equivalent Carnot cycle efficiency working between the same temperature differences. Some aspects of “effective frequency” characteristics of dissipative flows are also discussed with relation to the frequency of collapse of the convected frictional disturbances.
Sound propagation out of an open-pit strip mine
Authors: Nicholson M.
Published: October 2005

The sound propagation out of an open-pit strip mine is determined by solving the wave equation for the particular geometry of a strip mine and for an incoherent point sorce. The geometry of the strip mine is assumed to consist of five separate regions. Region I is a horizontal region of height h1; region II is a negatively sloped line from (x1, h1) to (x2, 0); region III is a horizontal line at height 0; region IV is a positively sloped line from (x3, 0) to (x4, h3); and region V is a horizontal line at height h3. The Green's function equation is solved from each of the five regions. The solutions and their derivatives are then matched at the boundaries of each region. The attenuation for each octave band for noise emitted out of the pit is determined by averaging the results of small variations in spacial dimensions.
Resolving the excess attenuation controversy
Authors: Brown E. H. , Clifford S. F.
Published: October 2005

The attenuation of finite-width beams of sound or noise propagating through the atmosphere depends on turbulence-induced beam broadening as well as molecular absorption. Here, we develop a theory for such excess attenuation that does not suffer from the logical deficiencies of previous theories and that predicts both magnitudes and functional dependence in good agreement with experimental observations. We show that excess attenuation is not an intrinsic property of air, or even of the dynamic state of the atmosphere, but depends on both the geometry of the experiment and the orientation of the sound beam. The results should have great utility, both for estimating sound and noise propagation, and for improving the accuracy of acoustic remote sensing of the atmosphere such as echosonde measurements of the turbulence intensities Cv2 and CT2.
Effects of wind and turbulence on propagation over short distances near the ground
Authors: Plotkin Kenneth J.
Published: October 2005

A major difficulty with outdoor noise tests, such as those used for motor vehicles, is the variation of measured sound levels under various conditions, or even between successive tests under nominally identical conditions. An analytic investigation of wind and turbulence effects has been conducted to identify the source of these variations. Theoretical models for refraction by large-scale gradients and scattering by turbulence have existed for a considerable time; the present study was simply a matter of applying these to a typical vehicle noise test configuration of a 4-ft-high microphone 50 ft from an extended source ranging from ground level to 15 ft high. Considering only a perfectly reflecting, level ground surface, two phenomena have been identified as significant: changes in interference pattern between direct and reflected rays due to mean wind gradients and scattering by velocity and thermal turbulence. It is predicted that changes in interference patterns can lead to a nominal 3-dB variation in measured noise level, depending on sorce height and wind direction. This result is based on consideration of broad-band effects only, and does not include anomolous cancellation minima of pure tones. Scattering was computed for two conditions: wind under thermally neutral conditions, and an extremely strong temperature inversion with no wind. Conditions of a 12-mph wind, or of pavement temperatures 15° above ambient, were computed to result in rapid vehicle noise measurement fluctuations on the order of several decibels. In both cases, this variation is proportional to the mean gradient. A significant result of the wind scattering calculation is that the variation is independent of mean wind direction.
Noise impact of air carrier operations for the nation
Authors: Sutherland L. C. , Guido H. , Meindl  , Bartel C.
Published: October 2005

A detailed estimate has been made of the total impacted area and population around the nation's air carrier airports. Results of this analysis are summarized in this paper to illustrate unique modeling aspects in the area of land use and population density. The model is based, in part, on results of an earlier study conducted for the Department of Transportation on 23 of the nation's airports (DOT-TST-75-3) and on an analysis of operations at all air carrier airports. Three statistically average airports (AVports) were constructed to represent air carrier operations ranging from 10 to 1600 per day. Population data from census records for over 110 airports were used to construct corresponding average towns (AVtowns) around each AVport. The baseline estimate of the total impacted land area and population within the Ldn 65-dB contour in 1972 was 2740 square miles and 7.1 million people. The noise impact models are used to evaluate cost effectiveness of a number of noise abatement alternatives including aircraft noise reduction, operational changes, and land use or residential noise reduction treatments. [The study was supported by the U.S. Environmental Protection Agency.]
Surface wave simulation of jet noise using a Mercury Ripple Tank
Authors: Colwill W. H. , Reethof G.
Published: October 2005

The concept is investigated of reducing jet noise from aircraft jet engines, flare stacks, and similar high velocity jets by reducing the turbulence in the turbulent mixing region by means of magnetohydrodynamic interaction in an electrically conducting medium. Electrical conductivity is to be obtained by ion seeding. The feasibility of the concept is investigated by means of a shallow-surface-wave analogy to the aerodynamic noise generation, propagation, and radiation using a 4 by 6-ft mercury ripple tank. The mercury layer was 1/8 in. thick to assure nondispersive wave propagation. Jet velocities from Mach 0.4 to 1.1 were studied and good simulation of sound power, directivity, and spectrum characteristics of the jet were established relative to an axisymmetric air jet.
Comparison of cross-spectral and signal enhancement methods for mapping steady state acoustic fields in turbomachinery ducts
Authors: Posey J. W.
Published: October 2005

Any steady state acoustic field can be completely specified by spatially mapping the pressure amplitude and phase as a function of position and frequency. However, in many measurement situations, the observed pressure is not due entirely to the steady state field; but also contains random transients (either acoustic or nonacoustic). Using modern real time analysis equipment, it is possible to measure spatial variations in steady state acoustics-pressure amplitude and phase by taking the cross spectrum between two signals from probes in the same field or by taking the difference in complex. Fourier transforms of enhanced probe signals. The conceptual differences between these two approaches are examined, and each is used to analyzed pressure data from the inlets of two different turbo-machines. A complete mapping of this steady state field could be used to determine its modal content. A problem with long term non-stationary is found with both methods. Conditions for equivalence of the two methods are discussed.
Acoustics source diagnosis using coherency analysis
Authors: Scharton T. D.
Published: October 2005

Coherency analysis offers two potential advantages over cross-correlation analysis for diagnosing sources of acoustic noise. Firstly, coherency analysis yields frequency decomposition which is usually essential in acoustics problems; secondly, coherency is not frustrated by reverberation effects which reduce cross-correlation valves. Coherency measurements with multiple source in an anechoic, a reverberant, and a wind-tunnel environment are presented and interpreted, where possible, using the appropriate theory.
Noise path diagnosis in dispersive structural systems by cross-correlation
Authors: Barger J. E.
Published: October 2005

The cross-correlation between two noise waveforms measured at different points in a system is often calculated to show which paths are followed by noise reaching one point, when the noise is injected near the point. This technique can be frustrated when the mode of noise propagation is dispersive, as flexural waves on elastic plates, because the cross-correlation functions of the noise waveform is not simply a time-delayed and scaled version of the autocorrelation function. Simple analytical expressions have been derived for three attributes of the cross-correlation coefficient function for band-limited white noise waveforms; time delay at the center of the peak in the function, time spread of the peak in the function, and average cross-correlation coefficient at the peak. The attributes are related to the path length, phase speed, and frequency exponent of the propagation wavenumber. The peaks in some experimental cross correllograms are compared to calculations using the analytical expressions, showing evidence of dispersive propagation.
“Total Voice”—Speaker verification goes deluxe!
Authors: Doddington George R. , Hydrick Barbara M.
Published: October 2005

Practical use of speaker verification implies a preliminary task of user identification. The identification mode is selected to be a spoken sequence of six digits. Verification may then be performed on the identifying speech data. This “total voice” system must recognize connected digits independent of speaker with very high reliability. Three sequence constraints aid recognition: (1) two parity checks must be satisfied, (2) all digits must be different, and (3) “difficult” digit pairs are disallowed. The speech processing strategy features highly reliable time registration and accommodates multiple concurrent hypotheses at various processing levels. Operational performance appears feasible from preliminary results: sequence recognition-< 1% rejection, < 0.2% error; speaker verification-< 1% user rejection, < 2% impostor acceptance. This system has been simulated in real time on a minicomputer. [Research was sponsored by the Air Force Systems Command, Rome Air Development Center.]
Automatic recognition of semivowels in word context
Authors: Fujisaki Hiroya , Sato Yasuo
Published: October 2005

Based on an approximate formulation of the coarticulatory process at the acoustic level and a method for adaptation to individual differences, a scheme for reliable segmentation and recognition of connected vowels has already been established [H. Fujisaki et al., Speech Communication Seminar, Stockholm 1974]. The present paper describes a study for the extention of the scheme to recognition of vowels and semivowels in word context. Values of formant targets which represent a command for each phoneme, its duration, as well as the rate of transition between successive phonemes are extracted as parameters from time-varying patterns of formant frequencies. Among these parameters, the command duration is shown to be most effective in discriminating semivowels /j/ and /w/ from vowels /i/ and /u/. A scheme for recognition of vowels, semivowels, and their sequences based on formant targets and command duration is then proposed and tested experimentally using meaningful and nonsense words uttered by four speakers.
Vocabulary and syntactic complexity in speech understanding systems
Authors: Goodman Gary , Reddy D. Raj
Published: October 2005

Comparing the realtive performances of speech-understanding systems has always been difficult and subject to speculation. Different tasks naturally require different vocabularies with varying acoustical similarities. Moreover, constraints imposed by the syntax may make recognition easier, even for vocabularies with high ambiguity. We define “inherent size” as a measure of vocabulary complexity and investigate its relation to recognition rates and the (apparent) vocabulary size. Word recognition is modeled as a probabilistic function of a Markov process using phoneme confusion probabilities derived from an articulatory position model. Multiple pronunciations and allophonic variations are allowed. Analysis of maximal word confusions leads to lower bounds for expected word recognition rates. Inherent vocabulary size is derived from these bounds. To evaluate syntatic constraints for finite state languages, an inherent size is computed for each state based on the subset of words which lead from that state. Then, average path complexity is computed for the language. This language complexity, when compared with the total vocabulary complexity and average path length, yields the degree of syntactic constraint. Analysis of several tasks will be reported.
Monitoring sound pressures within the ear: levels experienced by operators of snowmobiles
Authors: Brammer A. J. , Piercy J. E.
Published: October 2005

Diffraction by parts of the body and nearby objects (e.g., parts of machines), the proximity of the source, and the directional properties of the external ear lead to differences between free-field measures of sound pressure and the levels experienced by an individual. A miniature microphone located within the ear at the cavum of the concha is free of these effects and is therefore well suited to studies of an individual's exposure to noise. For operators of snowmobiles, sound pressures at the concha exceed levels measured 8 cm from the side of the head by ∼7 dB from 2–4 kHz, but are ∼3 dB less at frequencies below 500 Hz. For these and similar shaped source spectra, A-weighted sound pressures at the concha (typically 100–105 dB) exceed levels near the head by ∼3 dB. Predictions of the A-weighted levels experienced by an operator from measurements of sound level 15 m from these vehicles can introduce errors of ±5 dB.
Search for individual multidimensional differences in annoyance ratings
Authors: Ahumada A. , Nagel D. C.
Published: October 2005

Annoyance ratings of real and simulated aircraft flyover noises were analyzed under the assumption that each person's rating of a sound was a possibly idiosyncratic linear combination of the values of a set of common stimulus features. A standard statistical package factor analysis program, BIMED P4M, was used to find stimulus vectors and observer weight vectors identical to those obtainable by Carroll and Chang's multidimensional sealing program MDPREF. Results are presented for five jet flyovers to ten amplitude levels and for sets of short bursts of wide band noise spectrally shaped like jet flyovers. These sets varied in burst number and amplitude, allowing for individual differences to appear in temporal weighting functions. [Work supported by Stanford-Ames Joint Institute for Aeroacoustics.]
Vibrations of plates and cylindrical shells in an acoustic medium
Authors: Martin Gordon E.
Published: October 2005

In the calculation of the natural frequencies for submerged infinite plates and cylinders, the equations generally solved are of transcendental form. By using a suitable transformation, it is demonstrated that the equations to be solved become of polynomial form and readily amenable to exact solution. This paper discusses such equations for thin plates and cylindrical shells with vacuum on one side and air or water on the outer side. Numerical results are given for the solutions obtained. The technique can be applied to other problems of similar form.
On the statistical energy analysis
Authors: Maidanik G.
Published: October 2005

The statistical energy analysis is based on the expression for the power flow between coupled dynamic systems, each consisting of a multiplicity of modes. Usually, the expression is derived by properly identifying the modes as mechanical oscillators and by simply generalizing the expression for the power flow between two coupled mechanical oscillators. The latter expression states that the power flow is proportional to the difference in the “temperatures” of the two mechanical oscillators. In the generalization, cross-modal terms are neglected and dismissed. In the presentation, the expression for the power flow between two multimodal dynamic systems that are coupled by a single link attached at localized positions on the dynamic systems is derived in full. The cross-modal terms are identified and isolated. A number of conditions under which the cross-modal terms tend to vanish so that they can be neglected are illustrated and discussed.
Frequency decomposition of the vibratory excitation of gear systems
Authors: Mark William D.
Published: October 2005

The principal source of vibratory excitation of gear systems is the static transmission error which measures the deviation from uniform relative rates of (slow) rotation of pairs of meshing gears. The static transmission error can be decomposed into tooth bending, profile modification, and machining error components. The contributions of each of these components to the frequency spectrum of the static transmission error, and the effects of the mesh geometry parameters of helical gears on the spectrum, will be discussed.
Diffuse field sensitivity of external ear based on reciprocity principle
Authors: Shaw E. A. G.
Published: October 2005

The reciprocity principle defines a general relationship between transmission and reception in an acoustical system. By applying this principle, the transformation of sound pressure level from a diffuse sound field to the eardrum can be expressed in terms of the frequency. the radiation impedance Zrad of the external ear looking outward from the eardrum position, and the load impedance Zd presented by the eardrum. The formula, which contains no assignable constants, has been used to calculate the diffuse field response curve for a physical model of the external ear combined with an eardrum impedance simulator. An impedance tube was used to measure Zrad and Zd. The magnitude of the response and the frequencies of the resonance peaks are in excellent agreement with other measurements. The diffuse field pressure gain at the primary resonance frequency (2.7 kHz) is approximately 18 dB.
Effects of an experimental acoustic neurinoma on stapedius reflex activity
Authors: Mangham C. A. , Miller J. M.
Published: October 2005

An experimental model for controlled studies of an acoustic neurinoma will be described. The model employs nonhuman primates. It permits chronic experimentation. It is reversible. Essentially, the preparation is based upon the implantation of an inflatable Silastic rubber balloon in the VII and VIII cranial nerves in the internal auditory meatus of the monkey. Prior to and following such preparation, a systematic study of the contralaterally evoked stapedius reflex was performed. Afferent and efferent limbs of the reflex arc were studied. The effects of balloon inflation and deflation were examined. Variables studied included threshold across frequency, dynamic range, habituation, rate of rise, and recovery time. Normative data indicate the characteristics of the monkey stapedius reflex are comparable to man. Implantation reversibly affected all variables except habituation which was permanently affected. Changes in all variables were reversibly influenced by balloon inflation and deflation. The time course and quantitative changes observed will be described. Clinical implications and possible basic mechanisms underlying the effects of the acoustic neurinoma on auditory function will be discussed. [Work supported by NS08181 and RR00166.]
Noninvariance of the ear advantage in dichotic listening
Authors: Speaks Charles , Niccum Nancy , Carney Edward
Published: October 2005

Listeners received 50 dichotic trials of both natural and synthetic CV syllables, and marked two responses for each of 30 syllables pairs per trial. The paired responses were distributed as a bivariate normal; left and right-ear scores had equal variance (σ=8%) and were uncorrelated (r=−0.02 for synthetic; +0.15 for natural). Percent ear advantage also was distributed normally with a standard deviation about equal to the mean (synthetic, X̄=12.9%, σ=11%; natural, X̄=9%, σ=10%). Thus, listeners with a mean REA evidenced many trials with either no ear advantage or an LEA (29% natural; 19% synthetic). Variability in left and right-ear scores is assumed to arise from random, uncorrelated, time-varying “noise” in pathways from each ear. The ear advantage, left or right, is modeled as a function of the S/N ratio in the respective pathways. The ear advantage is not invariant and, by this account, may not always be indicative of unilateral hemispheric specialization for speech processing. [Supported by PHS Grant No. NS-12125.]
Difference limens for formant frequencies of steady-state and consonant-bounded vowels
Authors: Mermelstein Paul , Fitch Hollis
Published: October 2005

Difference limens of formant frequencies were measured for two steady-state vowels and the same vowels in symmetric stop-consonant contexts. The stimuli were generated using a computer-programmed synthesizer and the formant frequency parameters were held constant or adjusted to symmetric cubic functions of the time difference from the temporal center of the syllable. The difference limens (DL) for the time-varying consonant-vowel-consonant (CVC) stimuli were found to be significantly larger than those for the steady-state vowels, sometimes exceeding 10% of F1 or F2. In some cases the DL for the second formant is found to be larger in the direction of expected formant-shift due to consonantal coarticulation than in the reverse direction. The difference in DL values in and out of context has, at least partially, an auditory origin. Additionally, the phonetic decoding of the CVC stimuli may introduce information loss from auditory short-term memory. Implications for speech coding applications are discussed. [Supported in part by NICHD Grant HD-01994.]
The Hearsay-II speech understanding system
Authors: Erman L. D. , Hayes-Roth F. , Lesser V. R. , Reddy R.
Published: October 2005

The Hearsay-II System has as its design goal recognition, understanding, and responding to connected speech utterances, particularly in situations where sentences cannot be guaranteed to agree with some predefined, restricted language model, as in the case of the Harpy System. Further, it attempts to view knowledge sources as different and independent which cannot always be integrated into single representation. It is based on the blackboard model [V. R. Lesser, R. D. Fennell, L. D. Erman, and D. R. Reddy, IEEE Trans. Acoust. Speech and Signal Process. ASSP-23, 11–23 (1975) with knowledge sources as a set of parallel processes which are activated asynchronously depending on data events. The system performs on the Information Retrieval task with accuracy comparable to that of the Harpy system, but runs about 2 to 20 times slower. More complete performance results will be reported. As we get closer to unrestricted vocabularies and nongrammaticality of spoken languages, it will be necessary to have systems which have the flexibility of Hearsay-II and the performance of Harpy. [Research supported by the Defense Advanced Research Projects Agency.]
Feature extraction segmentation and labeling in the Harpy and Hearsay-II systems
Authors: Goldberg H. G. , Reddy R.
Published: October 2005

Goldberg [J. Acoust. Soc. Am. 59, S97(A) (1976)] has shown that uniform techniques for segmentation and labeling can provide the initial signal-to-symbol transformation for speech recognition systems with reasonable accuracy and efficiency. Furthermore, the choice of parametric representation was not found to be critical for most commonly accepted representations. However, for efficiency, the computationally simplest techniques should be used to segment the utterance before more accurate (and expensive) spectral representations are used for labeling [R. Reddy, J. Acoust. Soc. Am. 42, 329–47 (1967)]. To provide an initial symbolic input for both the Harpy and Hearsay-II systems, an hierarchical, feature-extraction based segmenter, using the ZAPDASH parameters, has been developed. After segmentation, labeling is done by a modified LPC minimum distance [F. Itakura, IEEE Trans. ASSP-23, 67–72 (1975)]. Labeling proceeds by comparing the midpoint of each segment with stored templates (acquired by an iterative learning process from speaker-specific training corpus) and adjusted with weights according to features obtained from the segmenter. The use of the highly efficient segmentation procedures and parameters provides approximately a factor of 5 speedup over uniform techniques which were previously used with both Harpy and Hearsay-II [Research supported by the Defense Advanced Projects Agency.]
Teaching musical acoustics to the musician—problems and questions
Authors: Kelly Robert E.
Published: October 2005

Some problems and possible solutions associated with teaching musical acoustics specifically to musicians are discussed, along with some typical questions encountered. The topics are considered from a dual viewpoint: the physicist knowledgeable in music and a musician knowledgeable in physics. Some of the subjects considered are vibrators, tuning, terminology, transposition and algebra, scales, translation between scientific and musical language, choice of instruments and personality, and problems in communication.
Some aspects of flow noise suppression
Authors: Peter Abraham C.
Published: October 2005

Some aspects of flow noise suppression are discussed on the basis of the processes underlying the physics of flow noise formation [A. C. Peter, J. Acoust. Soc. Am. 59, S92 (A) (1976)]. It is shown that, for a given fluid, the efficiency of noise emission is a function of the frictional temperature rise attained by the frictional disturbance front. Accordingly, an early collapse of this disturbance front will cause a reduction of its lifetime (i.e., the time elapsed from the formation of the disturbance until its ensuing collapse). This, in turn, will cause a reduction of the frictional temperature buildup with the resultant decrease in the efficiency of flow noise emission. It is also shown that such early collapse of the disturbances may be induced by decreasing their linear scale. An illustrative application of these principles to the physical action of a multinozzle jet engine suppressor is made. It is shown that by forcing the jet exhaust to pass through a cluster of smaller nozzles, while keeping the velocity of efflux unchanged, the decreased scales of the disturbances induce a faster collapse, thus, decreasing the efficiency of flow noise emission. The device is also shown to shift the peaks of noise emission from lower to higher frequency ranges. The principles may be extended to other jet noise suppression devices which tend to “break up” the flow in the dissipative region.
Unified acoustic theory and its application
Authors: Tsao M. C. C.
Published: October 2005

The role of acoustics theory in Noise Control Research is reviewed. The classical sound theory of ∂2ρ/∂t2 − c2 ∂2ρ/∂xi2 = 0 which deals only with the wave propagation problem is compared with the unified acoustic theory derived by Lighthill, ∂2ρ/∂t2 − c2 ∂2ρ/∂xi2 = ∂Q/∂t − ∂Fi/∂xi + ∂2Tij/∂xi ∂xj, which deals with the sound propagation problems as well as the sound generation problems. With this unified theory, the problems of fan noise, axial compressor noise, jet noise, flow noise, and turbulent noise all become apparent. The unified theory clearly illustrates the limitation of the nearfield and farfield sound measurement that can be confidently performed. Examples of various types of noise sources and their radiation directivity will be discussed.
Aircraft cabin noise barrier design and test
Authors: Campanella Angelo J.
Published: October 2005

The cockpit and cabin of contemporary propeller driven lightplanes continue to suffer high ambient noise levels in flight. These noise levels are typically 85–95 dBA. It was sought to typify and test lightweight barrier configurations in an attempt to achieve the 30 dB predicted performance [J. T. Howlett and D. A. Morales, J. Acoust. Soc. Am. 59, S64 (A) (1976)]. Several structural arrangements were tested as 12 in. (30 cm) square samples. Broadband transmission loss values of 20–25 dB were easily achieved, as opposed to considerably smaller values for thin aluminum panels. The barrier performance due to stiffness over and above that due to the mass law is clearly evident at lower frequencies. The achievable TL values are compared with known aircraft noise spectra, both inside the outside the cabin, to predict cabin quieting achievable with practical weight and cost constraints.
Interface wave model for deep cavity resonator oscillation
Authors: Elder S. A.
Published: October 2005

Using superposed elementary wave functions, an attempt has been made to model the oscillating wave displacement profile at the interface of a flush-mounted deep cavity resonator. It is found that, in order to obtain a match with experimental profile data for an air cavity, it is necessary to postulate the presence of upstream as well as downstream-traveling waves. Surface wave amplitude is set by requirement of asymptotic agreement with particle displacement of acoustic field in cavity. Implications for cavity drive mechanism will be discussed. [Work supported by GHR contract with the Naval Ship Research and Development Center.]
Speech quality of deaf children
Authors: Conrad R.
Published: October 2005

A brief review is given of the problems involved in, and solutions suggested for, assessing the intelligibility of the speech of deaf children. A Study of 350 deaf children aged 15–16 is reported which uses a new test for the intelligibility of spoken words. Results, as a function of hearing loss, are compared with the intelligibility of spoken two-digit numbers and with teachers' ratings. In all cases the correlation with hearing loss is very high; the main effect occurring for hearing loss between 65–95 dB. Two-digit numbers are significantly more intelligible to untrained listeners than are words, and the role of reading ability in this connection is examined. With hearing loss taken out there is a highly significant correlation between intelligibility of spoken two-digit numbers and prose comprehension. But there is little evidence that the intelligibility advantage of spoken numbers over spoken words read by a deaf speaker, is due to poor reading ability.
Influence of vowel environment on duration of consonants produced by normal hearing, hearing impaired, and deaf adult speakers
Authors: Whitehead R. L. , Jones K. O.
Published: October 2005

The effect of vowel environment on duration of consonants in the speech of ten normal-hearing, ten moderately to severely hearing-impaired, and ten profoundly deaf adult males was investigated. Each subject uttered five consecutive repetitions of the VCV syllables /isi/, /asa/, /i∫i/, and /a∫a/. The hearing-impaired and deaf subjects congenital hearing losses and were able to intelligibly produce the syllables. Each VCV sample was recorded onto audio tape and then individually played into a visicorder which produced the acoustic wave. Durational differences for /s/ and /∫/ resulting from the two final vowel conditions were examined for each of the three groups. Results indicated that for both the normal-hearing and hearing-impaired groups, there were significantly longer durations of the consonants in the final /i/ environment than in the final /a/ environment. For the deaf subjects, the consonants in the final /a/ environment were significantly longer than in the final /i/ environment.
Evaluation of an automatic word recognition system over dialed-up telephone lines
Authors: Rosenberg A. E. , Itakura F.
Published: October 2005

An evaluation of an automatic word recognition system [F. Itakura, IEEE Trans. Acoust. Speech Signal Process. ASSIP-23, 67–72 (1975)] has been carried out over dialed-up telephone lines using a laboratory computer on line. Thirteen speakers participated in the evaluation, calling up the system once a day over a five-month period. In each experimental session speakers were instructed by voice prompt to provide utterances of 12 words spoken in isolation. These words were randomly selected in each session from an 84-word vocabulary, 50 of whose entries are North American cities, designed to give the speaker access to airline flight time-table information. At each trial the speaker was informed whether his utterance was correctly recognized or not. There are two categories of error: an incorrect match or a rejection (no match). Speakers were requested to repeat words not recognized on the first attempt a second and, if required, a third time. The average number of trials per speaker over the entire experimental period was 840. The median percentage of incorrect matches on the first attempt over the 13 speaker was 2.7% while the median percentage of rejections was 5.7%. The median percentage of words still not recognized after 3 attempts was 1.5%.
Long-term feature averaging in voice authentication
Authors: Markel J. D. , Oshika B. T. , Gray A. H.
Published: October 2005

The purpose of this paper is to investigate the applicability of long-term feature averaging as an eventual means for performing text independent voice authentication (speaker verification). Based upon a set of long-term feature vectors, a principal component analysis is performed to obtain a normalized reference coordinate system for each speaker. Features extracted from the test speaker are transformed to this coordinate system and then the Euclidean distance is measured. It is shown thatunder a weak assumption of Gaussian statistics, the threshold necessary to attain a given probability of correct acceptance as a function of the number of dimensions or features can be theoretically calculated. Results of several preliminary experiments are presented to illustrate the technique.
Setting vibration limits from shaft amplitude measurements
Authors: Wilson D. S.
Published: October 2005

Confusion often exists on setting vibrational amplitude limits for rotating machinery. Present day monitoring instrumentation often includes shaft-displacement-type sensors. Specifications for acceptable amplitude limits for vibration are more commonly available for bearing cap or housing vibration and do not reflect levels for shaft amplitudes. An approach is proposed to compute acceptable amplitude levels due to rotating unbalance to protect the rotating components. The approach may be extended to nonsynchronous motions of the rotating shaft.