bluuebunny/crossref_metadata_2025 huggingface dataset:
Unit activity in auditory cortex of conscious rabbit
Authors: Perkins N. Kraus , Disterhoft J. F.
Published: October 2005

Major portions of the right hemisphere of conscious rabbit were stereotaxically mapped for auditory and nonauditory responsive regions. Extracellular activity was recorded from 101 auditory units. Acoustic stimuli were tone and white-noise bursts, 130 ms in duration, with 5 ms rise/fall times, presented 1/s. A silastic earmold fitted to the rabbit's external auditory meatus positioned the earphone, sound measuring microphone, and calibrated probe tube assembly so as to direct the sound source as close as possible to the eardrum. Cells with well-defined characteristic frequencies (CFs), ranging from 0.4 to 23 kHz. comprised approximately 60% of the population. Tuning curves were heterogeneous in shape. Latency of response onset ranged from 7 to 100 ms. Spontaneous rates less than 1 spike/s and up to 32 spikes/s were measured, and appeared to increase with cortical depth. A variety of temporal response patterns (PST histograms) were measured. Several units exhibited variable responses, such as occasional or inconsistent firing to stimulus presentations. Surgical procedures, sound delivery and recording techniques for unit recording in the conscious rabbit will be described. Characteristics of stimulus-evoked and background activity will be compared with neuronal activity in auditory cortex previously reported in other species. [Work supported by NIH Grant No. 2R01 NS12317.]
Directivity functions and reconstructed images of baffled planar radiators
Authors: Ayers R. Dean
Published: October 2005

A simple construction is used to relate the farfield radiation to the two-dimensional Fourier transform of the radiator's velocity distribution. This results in a convenient mapping of the (θ, φ) dependence for the radiated amplitude into the k plane. The inverse transform of the contents of the “radiation circle” of radius ω/c0 then yields all information available from the far field about the radiator's motion. This reconstructed image is the simplest among an infinite number of velocity distributions that would radiate identically with the actual distribution. If the radiator is a plate or membrane, transforming its equation of motion yields important information about the directivity function and the image. A mode function for an infinitely extended, homogeneous vibrator has a transform which is non-zero only on a circle. Below the coincidence frequency, radiation arises only from inhomogeneities—driving forces, loads, and boundaries. Boundary terms are intrepreted as linear force multipoles, and their images are expressed as normal derivatives of linear delta functions convoluted with a characteristic “smearing function.”
Remote acoustic sensing of internal wave fields in the North Atlantic
Authors: Orr Marshall H.
Published: October 2005

A towed multifrequency acoustic backscattering system was used during the joint air-sea interaction experiment (JASIN) to detect the short period internal wave field which existed in the experiment area. The experiment was conducted from July–September 1978 in an area centered at 12.5°W 59°N. The data to be presented were obtained during the second phase of the experiment, which lasted from the latter part of August to mid-September. Graphic acoustic records indicating the nature of the internal wave field which was detected and three-dimensional plots revealing the depth variability of the mixed layer base as a function of time during two 24-h box tows will be presented. A possible mixing event was detected and will be discussed. [Work supported by NORDA.]
Remote sensing of high-frequency internal waves with a narrow-beam echosounder
Authors: Kaye G. T.
Published: October 2005

A method is presented to extract internal wave information from acoustic reverberation data. Previous work with a narrow-beam 87.5-kHz echosounder from R/P FLIP off southern California indicated that the reverberations from below the mixed layer was dominated by discrete returns from fish and other similarly sized organisms. Excellent qualitative agreement was found between scatterer depth fluctuations and high-frequency internal waves inferred from isotherm motions. For a quantitative comparison, a tracking scheme was developed which estimates the local mean vertical motion of a number of scatterers and thus approximates the internal waves. Good coherence is found between isotherm depth histories and the tracking output for frequencies of 0.5–10 cph, especially in the octave of 3–6 cph. [Work supported by DARPA, Code 222 of ONR, and NORDA.]
Infrasonic ambient ocean noise measurements: Eleuthera
Authors: Nichols Rudolph H.
Published: October 2005

Measurements of ambient ocean noise in the frequency range 0.02–20 Hz were made with three current-screened hydrophones bottomed off Eleuthera Island, at depths of 13, 300, and 1200 m, respectively, over a period of about six weeks in June, July, and August. The results are compared with reported results of other experimenters and with results of some published theories of infrasonic noise generation in the ocean. Comparisons with published experimental data in the frequency range from 0.1 to 20 Hz show reasonable agreement. There do not appear to be published data in the region below 0.1 Hz for comparison. Comparisons with results of theories do not allow conclusive identification of generating mechanisms, but it appears that nonlinear interaction of surface waves and/or ocean turbulence are likely candidates in the frequency range 0.1–10 Hz. Below 0.1 Hz, no mechanism is postulated to account for the steep rise in noise level with decreasing frequency observed in the Eleuthera data. [Work supported by ONR.]
Low-frequency biologic noise near the NOSC oceanographic tower
Authors: Northrop J. , Stixrud T. E.
Published: October 2005

Low-frequency noise detected on horizontally polarized geophones, vertically polarized geophones and bottomed hydrophones was recorded near the NOSC oceanographic tower in summer (August), but was absent in winter (December). The sounds have been previously described as of the “chorus” type and have not yet been identified as to source (W. C. Cummings, personal communication). The sounds peak periodically at about 400 Hz with amplitudes diminishing rapidly below 100 Hz and above 1000 Hz. The periodicity is typically 45 s to 1 min, and observed amplitudes vary from barely detectable up to 26-dB peaks. Noise levels from this source are higher on the hydrophone recordings than on the geophone recordings and slightly higher on the E–W oriented geophone than on either the vertical or N–S geophone. The source appears to be light sensitive, being present under daylight and moonlight conditions, but absent during periods of cloud cover at night. [Work supported by ONR.]
Vertical directionality of the noise field at a deep ocean site off Cape Hatteras
Authors: Wales S. C.
Published: October 2005

The vertical ambient noise field was measured during April 1978 at a deep ocean (5400 m) site approximately 250 nm southeast of Cape Hatteras using a 31 element array (10 m hydrophone separation). Data has been analyzed using FFT narrowband processing and beamforming over the frequency range 45–100 Hz. The mean noise level due to surface shipping was observed to decrease rapidly beyond ±20° in elevation angle. Beyond ±20° multiple bottom-reflected arrivals were observed from nearby (<30 nm) ships. The long-range arivals were poorly defined in angle with the exception of those near 0°. Propagation models suggest that the near 0° arrivals represent noise from coastal shipping which has propagated through the oceanic front defined by the Gulf Stream and been channeled to near broadside angles. Noise between 10° and 20° off broadside is shown to differ spectrally from that in the near broadside region suggesting propagation from a different section of the ocean. The results are compared to theoretical models and the differences discussed.
Prediction of underwater transmission of helicopter rotor noise from measurements of noise during hovers over land
Authors: Hadden W. James
Published: October 2005

It is desirable, for such activities as helicopter-towed mine sweeping, to be able to make predictions concerning the noise transmitted into water from the helicopter. It is generally not feasible to make a “dry run” survey, nor is information readily available concerning rotor forces which would facilitate analytical predictions. A method is proposed for predicting the transmitted sound field by comparison measurements of the noise from a helicopter hovering over open terrain. The proposed technique incorporates the previously reported analysis of the transmission into water of the noise from a fluctuating force moving in a circular path. A similar analysis of the sound received at a plane surface with finite acoustic impedance is employed to relate land-based noise measurements to blade forces. The rotating forces are assumed to maintain a constant orientation with respect to the rotor path. The hover condition in the over-land measurements is deemed sufficient inasmuch as significant transmission to appreciable depths in water occurs only for a limited area under the helicopter rotor. (A simple ray-theory model indicates that total reflection results for angles of incidence greater than 11°.) It is found that contributions from horizontal (drag) blade forces are transmitted into water with negligible amplitude. [Work supported by Naval Coastal Systems Center.]
Application of reciprocity methods to the measurement of dynamic characteristics of a cavitating propeller in a water tunnel
Authors: Leehey Patrick , Gedney Charles J.
Published: October 2005

A reciprocity measurement, suggested by Dr. Neal A. Brown was used to determine volume velocity of a cavitating propeller operating in a simulated ship wake in the MIT variable pressure water tunnel. During calibration the tunnel wall was driven by a known force and the pressure at the propeller location was measured. The volume velocity was then inferred from the acceleration at the unloaded drive point caused by cavitating propeller operation. Initial measurements showed that the volume velocity so inferred decreased with increasing drive point distance from the propeller. Since unsteady thrust and torque are only slightly affected by the presence of cavitation, tests were carried out with a noncavitating propeller to determine the effect of dipole sources upon the initial results. A separate reciprocity measurement of alternating thrust, involving pressure gradient measurement at the propeller location, was carried out. The results of these tests, together with the effects of finite source size and mean shear flow will be discussed. [Work supported by the U. S. Maritime Administration.]
On the relation between the daytime deep scattering layer and the temperature field at Ocean Acre
Authors: Saenger R. Alfred
Published: October 2005

At Ocean Acre, the volume backscatter strength S(z;f), 12–15.5 kHz, associated with the daytime deep scattering layer in the main thermocline region is due to backscattering from swimbladder fish. In the NDI model for S(z;f) developed previously for light-sensitive layers, it is assumed that the number density n(z) of “effective scatterers” is determined by a Gaussian distribution of “preferred” light intensity values I tracked by the scatterers. that I decays with depth according to Lambert's law, and that the average backscatter cross section δ(z;f) is a constant, δ(f). This model is found to describe the daytime deep scatterer profile S only if I is replaced by an analogous “preferred” variable I′ with an exponential decay rate approximately one-tenth the extinction coefficient for light. Thus, some other environmental factor than light intensity primarily determines the shape of the S-profile for this layer. Here a physical interpretation of the NDI′ model is developed by showing that (1) measured abundance profiles nb(z) of swimbladder fish in the daytime deep scattering layer are described by the NDI′ model and (2), the exponentially decaying I′ required by the model is obtained if I′ is identified with a simple logarithmic function of the temperature field.
Representative hearing levels by race and sex in North Carolina industry
Authors: Royster L. H. , Royster J. D.
Published: October 2005

An extensive sample of North Carolina industrial audiometric test data has been compiled. The data base includes several different types of industrial environments. The size of the industries represented ranges from less than fifty to over ten thousand employees. The total population considered is in excess of 30 000 employees. The data are examined using analytical techniques developed over the past six years while investigating the effectiveness of industrial hearing conservation programs. One of the findings is significant differences in the initial hearing threshold levels by race and sex. A second observation is differences in the change in hearing levels by race and sex. It is concluded that the hearing levels of industrial employees differ significantly by race and sex. The differences are of such magnitude that a meaningful evaluation of industrial audiometric data bases is not possible unless the race and sex characteristics of the population are considered. [Work supported by North Carolina industry and The Rockefeller Foundation.]
Differences in the mean hearing levels between black and white nonindustrial noise exposed populations (NINEP)
Authors: Thomas W. G. , Driscoll Dennis
Published: October 2005

Evaluation of general population hearing level data yields significant differences by Race and Sex. These differences are most obvious in industrial populations investigated to date. In order to define these differences and gain a better understanding of possible causes, white and black NINEP samples have been obtained. A comparison is made between hearing levels representing the black and white NINEPs. Significant differences between male and female and black and white populations are observed. These differences are frequency dependent and are most pronounced in the male populations. [Work supported by The Rockefeller Foundation.]
On some aspects of mechanical reed woodwinds
Authors: Strong William J.
Published: October 2005

During the lifetime of the Acoustical Society of America, certain developments have led to an improved understanding of the physical and tonal properties of woodwind instruments. These developments include theoretical analysis, instrumentation for measuring acoustical properties, and high speed digital computing. This paper will review past work, summarize the present state of our knowledge. and offer some conjectures on the future. The content is restricted to a consideration of mechanical-reed woodwinds, although comparable things could be said about “air-reed” woodwinds. The following aspects will be discussed: (1) acceptable bore shapes; (2) theory of tone holes; (3) experimental measurement of input impedance: (4) numerical calculation of input impedance; (5) implications of input impedance: (6) reed and air-column interaction: (7) small-amplitude, steady-state vibrations: (8) medium-amplitude, nonbeating, steady-state vibrations; (9) functional modeling of arbitrary amplitude transient and steady-state vibrations: (10) tonal analysis-synthesis and spectral properties; and (11) tonal perception.
What happens when you blow your own horn?
Authors: Pyle Robert W.
Published: October 2005

This paper will trace the development of our understanding of the acoustics of brass wind instruments from the eighteenth century to the present. Topics to be covered include the theory of sound propagation in ducts and flaring horns, the physical attributes of brass-instrument tone, the physiology of the player, the regeneration mechanism of the player's embouchure, and the influence upon the instrument of the materials from which it is made. The sometimes remarkable empiricism of instrument makers and players will be discussed along with research by the scientific community.
Parametric acoustic array in the presence of turbulence
Authors: Korman M. S. , Beyer R. T.
Published: October 2005

The nonlinear interaction of two collinear ultrasonic beams in the presence of turbulence in water has been investigated. The transmitting unit was driven continuously at 3 and 5 MHz. A 1-in, diameter water jet (20 ft/s) was located with nozzle 75 cm from the beam path which intersects the flow at 90° and originates 40 cm from it. Forward scattering angles were measured in the plane of the jet and sender by a 2-MHz receiver located 185 cm from the interaction region. The energy spectrum of the turbulence had frequency components in the range of several Hertz to 2 kHz. In the presence of turbulence the difference frequency was broadened by sidebands up to +1 kHz from the center frequency for scattering results taken in the angular range −30° to +30°. The received spectrum was asymmetric relative to the center frequency. Comparisons are made between the spectral broadening of a primary 2-MHz signal and the broadening associated with a difference frequency component (2 MHz) that exists due to the mechanisms of the parametric array. These results are an extension of earlier experiments of the authors on the scattering of sound by sound in the presence of turbulence for a crossed-beam arrangement. [J. Acoust. Soc. Am. 64, S14 (A) (1978)] [Work supported by the Office of Naval Research.]
Intensity-induced “transverse amplitude diffusion” in the field of an axisymmetric parametric acoustic array
Authors: McKendree F. S. , Fenlon F. H.
Published: October 2005

In this paper numerical solutions of the Zabolotskaya, Khokhlov, Kuznetsov (i.e., ZKK) second-order paraxial wave equation are used to illustrate the concept of “transverse amplitude diffusion” [G. D. Malyuzhinets, Soviet Phys. Uspekhi 69, 749–758 (1959)] via the changing field structure of a diffraction-limited parametric acoustic array. In order to establish confidence in the numerical procedure, computed solutions are first compared with analytically derived weak finite-amplitude solutions. The amplitude-dependent directivity of parametric arrays formed by quasisaturated and saturated primary waves is then examined by considering (i) the effect of intensity-induced mutual coupling between adjacent ray tubes; (ii) its effect on the range-dependent ‘diffraction’ patterns of individual spectral components; and (iii) its effect on the time waveform. Throughout the review results will be displayed by means of three-dimensional computer graphic projections.
Noncontributive virtual sound sources
Authors: Woodsum Harvey C. , Westerrelt P. J.
Published: October 2005

It is well known that the virtual sound sources derivable from a d'Alembertian do not contribute to the field scattered out of the interaction region of two nonlinearly interacting sound waves. It is demonstrated in this paper that, in the absence of viscous stresses, these local field terms do not contribute to the nonlinear attenuation of the primary waves. Based upon this result, it is concluded that the attenuation produced by these terms is, in most practical cases, negligibly small. The method of proof is based on energy conservation and the work done by the primary fields on the virtual sources. The attenuation of one of the primary waves is determined by the energy conservation equation, ∇⋅〈Ij〉 = 〈pJ(1)q〉. If the virtual source strength q is derivable from d'Alembertian, i.e., 〈J(1)q〉 the spatial integral of this quantity over a simply connected volume V, enclosed by a boundary surface S which is removed to infinity, is readily shown to be zero; thus, no attenuation of the primary waves can be produced by such a term.
Nonlinear acoustodiagnostics of viscoelastic media
Authors: Nigul Uno
Published: October 2005

One-dimensional finite longitudinal pulses propagating according to the Voigt. Maxwell, standard, and Volterra-Rabotnov hereditary type linear and nonlinear mathematical models are considered. For the linear case the exact and asymptotic solutions are derived with the aid of Laplace integral transforms. Further, making use of an iterative method, asymptotic solutions are obtained which take into consideration weak nonlinear effects. The distortion of the finite pulse's form due to viscosity and nonlinearity of the medium is analysed. Conclusions are made about how experimental data on this distortion might be used for solving the inverse problem of finding the proper mathematical model of the given nonlinear viscoelastic medium and the physical constants which describe it.
Interaction of weak shock waves with random media
Authors: Sturtevant B. , Hesselink L. , Haas J. F
Published: October 2005

Recent studies of the scattering of weak shock waves by continuous and discrete scatterers in random media, and of the flow generated in the scattering medium by shock propagation are described. Consideration of the coupling between shock propagation and vorticity and/or entropy fluctuations in a fluid is particularly difficult if the wave is of finite amplitude, for basic nonlinearities of fluid mechanics become important both in the wave propagation and in the turbulent motion. In one experiment, wave propagation through a cubical volume of incompletely and randomly mixed gases at the end of a large shock tube has been studied. In a second, interaction with a random array of discrete scatterers (small helium-filled soap bubbles) is studied in a smaller facility. Both of these flows are visualized by schlieren and shadowgraph photography. The scattered pressure field behind the initial disturbance is measured. Methods for measuring the characteristics of the “turbulence” before and after passage of the wave using laser scattering in the random medium have been developed; the laser speckle pattern at the focal plane of the schlieren system has been recorded photographically and has been analyzed with a computer-controlled photodensitometer to yield information about the scale and intensity of the inhomogeneities in the scattering medium. [Work supported by NSF.]
Nonlinear theory of sound beams in dissipative fluids
Authors: Tjötta J. Naze , Tjötta S.
Published: October 2005

A general theory is being developed for the propagation and interaction of finite amplitude sound beams in dissipative fluids. The main results are obtained by introducing perturbation methods and deriving simplified equations governing the sound field, taking into account diffraction, absorption, and nonlinearity. From these equations solutions are obtained and matched to give a solution valid in the whole space of propagation. Applications are made to parametric acoustic arrays. In a very simple way, the theory here accounts for the variations in the amplitude and directivity of the generated sound as a function of range. It fully explains the observations by Hobaek and Vestrheim [Acustica 37, 74–82 (1977)], showing at short ranges a directivity of the generated sound stronger than that predicted by Westervelt's asymptotical formula [J. Acoust. Soc. Am. 35, 535–537 (1963).]
The use of SEA in building acoustics
Authors: Craik R. , Mackenzie R. K.
Published: October 2005

During 1974 a survey was carried out by the International Council of Building to establish the state of knowledge relating to noise and vibration within the built environment. The results of the survey clearly demonstrate the need for a better understanding of the transmission of sound through connected structures, and it was recommended that the solution to these problems would be best achieved by investigating the coupling loss factors between structural elements using SEA methods. During 1975 a meeting of representatives from 19 laboratories from throughout the world was held at Grenoble, France. The outcome of this meeting was the establishment of a program of collaborative studies based on agreed set of research priorities with each laboratory tackling the same problem, but using a different approach. Significant progress has been made to date, particularly in the study of a full scale building in Edinburgh. This study has resulted in the analysis of a large SEA model with 104 subsystems and has given over 150 measured coupling loss factors. These coupling loss factors, which give reasonable agreement with predicted results, are being used to determine the noise reduction of specific acoustic paths.
A simplified model for the prediction of airplane interior noise by the statistical energy analysis (SEA) method
Authors: Thanedar Balakrishna Dattatraya
Published: October 2005

Prediction of interior noise essentially represents a definition of attenuation of noise through a sidewall structure. It is a combination of response of the fuselage primary structure to the excitation and subsequent vibration and reradiation. In the cabin noise study, the cabin interior space is an indirectly excited subsystem, the surrounding exterior space is the directly excited subsystem and the fuselage shell structure forms the barrier. The important paths of vibrational energy exchange are mechanical and acoustical. The mechanical connections between the fuselage skin, stringer, frame, vibration isolator, and trim panels provide for the transmission of energy from the exterior space to the interior space by a mechanical path. The flow of vibrational energy via the sidewall cavity is by an acoustical path. The frames and stringers as well as the skin are the elastic structural elements that are capable of being excited under resonant, coincidence and nonresonant conditions. For a typical fuselage structure the frame coincidence frequency is about 80 Hz and the stringer coincidence is about 300 Hz. A typical skin coincidence frequency is 12 000 Hz. This indicates that in an ultimately desired basic SEA model, an appropriate representation for the primary fuselage structure, particularly for adequate low to mid frequency region, is to preserve the identity of all the three basic elements skin, frame and stringer. This makes the model very complex (Fig. S-1). Initially as a first step to SEA capability an alternate simplified model of intermediate complexity is considered. In this simplified model (Fig. S-2) the frame and stringer stiffened shell is replaced by an orthotropic shell of an equivalent stiffness. In addition it is assumed that mechanical path is secondary in importance to the acoustic path and can be eliminated as a first approximation. The method for the energy flow calculations and the evaluation of the parameters for this model has been programmed on the CDC6600 computer. The SEA cabin noise computer program has been used to calculate 737 fuselage skin vibration and interior noise levels. Figure S-3 shows calculated and measured 737 skin vibration levels for takeoff. The predicted values of the present analysis, with orthotropic representation for the fuselage shell are seen to compare quite well with the measured ones. Figure S-4 compares calculated and measured 737 interior noise levels for a ground engine run. In the low- to midfrequency range the SEA predicted interior noise levels is about 2 dB higher than the noise levels measured on a 737 during a ground engine run test (Fig. S-4). The limitations of the simplified model are discussed and the further planned analytical modifications are outlined.
Relationships between high- and low-probability SPIN scores
Authors: Bilger R. C. , Rabinowitz W. M.
Published: October 2005

The test of Speech Perception In Noise (SPIN) [D. N. Kalikow, K. N. Stevens. and L. L. Elliott, J. Acoust. Soc. Am. 61, 1337–1351 0977)] results in two scores for a subject—the percent-correct identification of low- and high-probability items, denoted PL and PH. A basic problem is to derive from these raw scores appropriate metrics which characterize a subject's abilities (a) to make use of context, and (b) to hear speech in noise. Examination of the PL and PH scores (averaged across all ten forms) for 128 subjects with sensorineural hearing loss suggests that normal-normal-probability space may be a useful coordinate system for characterizing these abilities. In this space, the extent to which the subject makes use of context can be associated with the difference d between the Z scores associated with PL and PH, i.e., d = ZH − ZL. Additionally, the overall ability of the subject to hear speech in noise can be associated with the quantity κ = −(ZH −ZL)/2, which is independent of d, and which can be transformed back to an equivalent “percentage-hearing” score. [Work done under contract to NINCDS.]
Ratings of voicing disruptions
Authors: Clack T. D. , Stone R. E.
Published: October 2005

Perceptual judgments of speech are used by clinicians, by those assessing telecommunication systems, etc.—often without systematic evaluations of reliability or accuracy. To examine such issues, brief disruptions in voicing are studied in samples of flowing speech, i.e., via recordings of a woman reading two sentences in examples of her “worst” to “best” possible voice during and after recovery from laryngitis. Five samples were heard (real time) twice by 11 listeners who graphically rated each for disruption severity along a normal-to-abnormal continuum. These ratings reveal large and significant disparities in some rejudgments of identical samples. and thus suggest the operation of sequential dependencies. A simple “linear-with-memory” model is developed to describe such operations. In a follow-up study, judgments were obtained again using graphic-rating protocols incorporating descriptive guides. This effectively reapportions the ratings, and the sequential dependencies are even more evident. The model demonstrates utility in describing and recursively predicting these ratings by individuals as well as groups of listeners. [Work supported by NIH and Department of Otorhinolaryngology, University of Michigan Medical School.]
The California consonant test in noise
Authors: Danhauer J. L. , Leppler Jonathan G.
Published: October 2005

Speech discrimination scores for 35 normal-hearing listeners were obtained on the California Consonant Test (CCT) in four noise competitors: (1) a four-talker complex (FT), (2) a nine-talker complex (BGMTN), (3) party noise (PN), and (4) white noise (WN). The CCT was mixed with each of the noises and presented ipsilaterally to five listeners in one of seven signal-to-noise ratios (S/Ns). Articulation functions were similar for all four noises except at more severe S/Ns where “peripheral maskers” had less effect on scores than “perceptual maskers.” Practical considerations are discussed.
Male-female differences in speaker intelligibility; normal and hearing-impaired listeners
Authors: Marguiles Maris K.
Published: October 2005

Five groups of ten listeners each (normal-hearing, conductively impaired, flat, moderately sloping-, and severely sloping sensorineural impairments) were presented with recordings of the CHABA sentences. The hearing-impaired groups were further subdivided into five male and five female listeners. A second nonindependent subdivision was that of age (five above and five below 50 years). Five types of background noise were used; high-pass, low-pass, white, male-spectrum and female-spectrum shape. The ratio of speech peaks to rms noise level was set at 0 dB for each list. Significant differences in intelligibility were obtained between listener groups, noise type, listener age, and talker gender. The female talkers were more intelligible than the male [for a common speech-to-noise ratio]. Younger listeners scored higher than older. As expected, intelligibility scores decreased with increase in degree of impairment, but the relative masking of the different noises varied between listener groups and speaker gender.
A Proposal for standard intelligibility test tape recordings
Authors: Schiller E.
Published: October 2005

Intelligibility testing is often the only correct way to evaluate a speech system. Two factors have not been standardized: the talkers' voice quality and the listeners' ability to understand degraded speech. Significant differences exist between test groups because of these factors, so it is not proper to consider the resulting intelligibility scores as absolute values. I propose to coordinate the development of tape recorded word lists to be used as a reference/standard. A group of “representative” talkers, rather than one talker, would read each word list for balanced voice quality. A large representation of the population would evaluate these tapes under various degraded speech conditions to obtain the “reference” scores. Details as to word lists, method of presentation, types of degration, and listener population selection would be addressed by a varied group of interested and qualified investigators.
Performance of external ear as a sound collector
Authors: Shaw E. A. G.
Published: October 2005

The overall performance of an acoustical antenna system can be expressed in terms of its absorption cross section which, for a diffuse sound field, is defined as the cross-sectional area A of the perfectly absorbing sphere which would absorb the same sound power from the field as the system under study. The limiting value of A is λ2/4π. For the external ear A can be expressed in terms of the eardrum impedance ZA, the impedance looking outward from the eardrum Za, and the radiation efficiency η all of which can be measured or estimated. The analysis shows that the ear is a very inefficient sound collector at low frequencies but performs well at its primary resonance frequency (2.7 kHz) where A attains a peak value of 5 cm2 compared with theoretical limit of 13 cm3. The cross section almost attains the limiting value at 9 kHz and remains within 6 dB of the limit up to 15 kHz. However, when allowance is made for the energy loss in the eardrum and middle ear it is clear that the cochlea receives no more than 10% of the power available in a diffuse field at any frequency.
Computerized analysis of moiré contours applied to eardrum shape measurements
Authors: Funnell W. R. J.
Published: October 2005

Khanna and Tonndorf have used moiré topography to study the resting shape of the eardrum and the effects of static pressures [J. Acoust. Soc. Am. 57, S72 (1975} and 58, S88 (1975)]. They have recently modified their apparatus so as to remove the parallel grating image that had been superimposed on the moiré isotathmic (constant-depth) contours. By simplifying the pattern recognition problem, this has made it feasible to develop a semiautomatic method of analyzing the data. An interactive computerized image-processing system is used to identify and extract the contours from the photographic image. An interactive computer-graphics system is then used for computing shape profiles, volumes, static displacements, etc. and for preparing the shape data for use in a finite-element model of the eardrum. [Work supported by Medical Research Council of Canada and Macdonald Stewart Foundation.]
The development of middle-ear admittance in chicks
Authors: Bahl C. A. , Relkin E. M. , Saunders J. C.
Published: October 2005

Tympanometry was used to follow the maturation of middle-ear function in neonatal chicks from hatching to 10 days of age. The methods have been described elsewhere [Relkin and Saunders. J. Acoust. Soc. Am. 63, Suppl. 1, S42 (1978)]. Subjects in each of five age groups were anesthetized, mounted in a head holder, and the tympanic ring was surgically exposed. A small hole was made in the contralateral tympanic membrane in order to equalize middle-ear pressure to ambient pressure through the interaural pathways. A tympanometer probe was sealed directly over the tympanic membrane using a short piece of metal tubing to couple the probe to the tympanic ring. The magnitude of the volume velocity required to reach a criterion value of sound pressure was measured at frequencies between 0.4 and 1.8 kHz. Acoustic admittance at the tympanic membrane was calculated from the volume velocities measured when the tympanic membrane was stressed with a pressure of +200 mm H20 and when it was at ambient pressure. In all groups a monotonic increase in admittance magnitude was noted with increasing frequency. Phase, for low frequencies, was about 90° and decreased toward zero as the test frequency increased. There was relatively little change in admittance magnitude over the range of ages tested. These data further reflect the high degree of auditory development in the newly hatched chick.
Acoustic emissions in soils and their use in assessing earth dam stability
Authors: Lord A. E. , Koerner R. M.
Published: October 2005

Although considerable effort has been expanded into acoustic-emission research and related applications, scarcely any has been in the direction of particulate materials. One such material is soils where numerous earthen structures present challenging problems insofar as their stability and structural integrity is concerned. Such structures involving soils in whole or in part are earth dams, embankments, retaining walls, etc., where both fundamental and field problems exist. This paper is a brief review into our studies on the acoustic-emission response of soils. The majority of the work has been on laboratory-sized soil samples, although some large-scale model work and field instrumentation is also reported. Parallel studies as to the fundamentals of the emissions in soils are also noted. Thus far it appears that acoustic-emission monitoring techniques can provide the nucleus of a field monitoring technique to access stability of earthen structures.
Annoyance judgments of interior aircraft noises: A comparison of speech and reverie conditions
Authors: Rupf J. A.
Published: October 2005

Two groups of forty subjects each were presented with three minute noise exposures. Test stimuli consisted of four types of interior aircraft noise (two commercial jets, general aviation, helicopter), each presented at levels of 85, 80, 75, and 70 dBA. Subjects were seated in pairs in a transportation system simulator. During the noise exposures one subject group was instructed to converse while the other group was instructed to remain silent. After each noise presentation all subjects rated the annoyance of the noise, judged its acceptability, and estimated how long they could travel in the noise without discomfort. Responses by the speech group were more critical than the reverie group on all three measures. Annoyance ratings and acceptance judgments were approximately 3 dB more severe at low noise levels and approximately 1 dB more severe at high noise levels for the speech group. [Work supported by NASA.]
Interaction of 1.5-MHz ultrasound with human lymphocyte cultures
Authors: Hedges M. , Leeman S.
Published: October 2005

Lymphocytes constitute some 30% of the white cell population of human blood and any medical exposure to ultrasound will involve irradiation of this important cell group. Lymphocyte death, as monitored by pyknosis, has been found to follow almost immediately on exposure of cultures to 1.5-MHz continuous wave ultrasound, at power levels which leave the cells intact, and which are within the usual therapy range. An intensity threshold for the effect exists at ∼1.l W/cm2, and it is shown how both the number and induced pyknosis rate of the affected cells are modified by the parameters of the exposure. The response to pulsed ultrasound is very different, with a 15−20-h delay in the measurable consequences of the sonication. A remarkable result is that the course of the ultrasound action is strongly modified in the presence of certain drugs. Experiments relating to the sonic impairment of lymphocyte function are also discussed, and some preliminary results reported. Some evidence is presented to suggest that cavitation is an important interaction mechanism, but some difficulties with this interpretation are discussed.
Speech recognition through spectrogram matching
Authors: Ingemann Frances , Mermelstein Paul
Published: October 2005

In order to assess human analysis of acoustic data before attempting such analysis by machine, a series of experiments was conducted in which subjects were asked to match spectrograms of continuous speech to reference spectrograms of the same words. Although error rates varied with sentence difficulty and size of vocabulary, comparison of the matches shows greater agreement in phoneme segments than other experimenters have obtained in phonetic transcriptions of unknown utterances without semantic of syntactic processing. Accuracy in matching can be further improved by feedback to the human analyst in the form of spectrographic representation of a sequence of tentative matches spoken as if they made up the unknown utterance. The results suggest that automatic matching of word− or syllable−sized acoustic patterns may provide a more accurate phonemic input to the syntactic−semantic component of a speech recognition system than direct transcription of individual phonetic segments.

Subject Classification: 70.65, 70.60.
Sampled−data representation of a nonuniform lossless tube of continuously variable length
Authors: Strube H. W.
Published: October 2005

The sound transmission through a nonuniform tube (e.g., the human vocal tract) is digitally simulated using a tube consisting of uniform segments, the length of which is determined by the sampling frequency. Then the problem arises of how continuous changes of the tube length can be represented. It is solved by inserting a segment of variable length, which causes fractional powers of z to appear in the z−transform expressions describing the transmission behavior. These are made rational by first− and third−order expansion in (z−1 − 1). For a uniform tube, the resulting error in formant bandwidth is calculated.

Subject Classification: 70.50.
Matrix formulation of acoustic scattering from multilayered scatterers
Authors: Peterson Bo , Ström Staffan
Published: October 2005

A T−matrix formulation of both acoustic and electromagnetic scattering has been given by Waterman for the case of one homogeneous scatterer, and this formulation has subsequently been extended to the case of several such scatterers by the present authors. In the present article we show that the matrix formulation is also well suited for the treatment of acoustic scattering from scatterers consisting of an arbitrary number of consecutively enclosing homogeneous layers with different propagation constants. We also show how the earlier results on the matrix formulation of acoustic scattering can be combined with these new results so as to apply to more general types of multilayered scatterers. Some numerical applications are given.

Subject Classification: 20.30.
Measurements of radiation impedance
Authors: Gilheany John J. , McCumber Leonard , Andrews Frank A.
Published: October 2005

A method is described for measuring the free−field radiation impedance of a single−degree−of−freedom underwater transducer. The displacement amplitude and phase of the vibrating surface in air and in water are measured with a laser interferometer and with an accelerometer. From these values and the input current, the radiation impedance may be computed. Measurements of the radiation resistance and reactance of a J9 transducer at 0.5−kHz intervals from 5.0 and 10.0 kHz are reported. The radiation resistance is also calculated from reciprocity calibrations and measurements of the directivity patterns at 5.0, 7.5, and 10.0 kHz. Excellent agreement is observed between the two methods.

Subject Classification: 30.50.
Unified analysis of conical ray transmissions with application to a time−varying ocean channel
Authors: Widtfeldt J. A. , Jacobson M. J.
Published: October 2005

A unified treatment of conical ray paths, corresponding to a nonlinear sound−speed profile family, is presented. For a concave downward profile, ray arcs may be hyperbolic, and there may be two such paths. They may also be parabolic or elliptic, with vertical major axis. For a concave upward profile, ray arcs are elliptic with horizontal major axes. When a CW sound source and receiving point lie on a horizontal bottom, the number of bottom reflections, initial ray angle, travel time, and spreading loss are studied in detail for RBR (refracted/bottom−reflected) rays. In an application of our results, temperature data off the Miami coast is used to determine sound−speed profile variations as a function of time. The acoustic phase of the total RBR field is then computed at a receiver 3 NM from the source. Theoretical phase variations are shown to be in reasonably good agreement with experimental phase fluctuations.

Subject Classification: 30.20, 30.25.
Transverse vibration of constrained rods with axial force fields
Authors: Kunukkasseril V. X. , Arumugam M.
Published: October 2005

Free transverse vibrations of rods which are axially constrained at ends and initially loaded with an axial force at an intermediate point are discussed. The theoretical developments are based on Timoshenko equations and explicit solutions and results have been obtained for hinged−hinged and fixed−fixed beams. Various interesting and new aspects, such as the influence of the magnitude and location of axial forces on the frequency spectrum, are evident from the numerical results.

Subject Classification: 40.22.
Normalized curve of molecular absorption versus humidity
Authors: Harris Cyril M.
Published: October 2005

Numerical values are given here for the normalized curve of molecular absorption versus humidity, a relationship obtained in an earlier study of sound absorption [J. Acoust. Soc. Am. 40, 148−159 (1966)]. These data, heretofore unpublished, form important input information in setting up a computer program for the evaluation of air attenuation.

Subject Classification: 35.20; 55.30; 28.40.
Frequency−domain seismic deconvolution filtering
Authors: Lackoff Martin R. , LeBlanc Lester R.
Published: October 2005

Reverberation in shallow water seismic profiles is a frequent problem that sometimes makes the geophysical interpretation of the records difficult. This can be further complicated if the acoustic source emits a bubble pulse. This paper describes a frequency−domain approach to deconvolution of the seismic signals to remove these artifacts. The resulting computation speed was found to exceed that of a time−domain Wiener filter by a factor of 10, for the same length dereverberation operator. Guidelines are established for using the FFT approach to deconvolution of seismic signals. The guidelines established are for the statistical stability and deconvolution ’’reach’’ of the filter, and prevention of FFT wrap−around effects. A digital filtering technique for obtaining a replica of the source signal from the received data record is presented and utilized in processing continental shelf air−gun data.
Difference thresholds for interaural delay
Authors: Hafter E. R. , De Maio J.
Published: October 2005

Cross−correlational models of binaural interaction postulate an interaural delay line in which neural impulses arising in one ear are delayed relative to those from the other. For localization based on interaural differences of time, accuracy is limited by the resolving power of this hypothetical delay line. The present study sought to determine whether the delay line is organized in such a way as to provide a foveal area of best acuity, as exists in spatial vision. Thus, threshold increments of interaural time difference (Δt)’s were determined as a function of overall delay (t). Stimuli were acoustic transients of either low (0.1 to 2 kHz) or high (3−4 kHz) frequency content, ranging in level from 18 to 68 dB SPL. The overall delay ranged from 0 to 500 μsec. In general, the functions that relate Δt to t were found to rise gradually with lowest thresholds occurring for the lower−frequency and higher−level clicks. In exception were the results from weak high−frequency clicks, which showed a marked and sudden rise at large values of t. Ignoring the sudden rises in these latter cases, the resolution of the delay line is best described by a shallow decay in acuity over the range of delay tested, and though accuracy is best in the center, clearly no sharp delineation exists in sound localization as in vision.

Subject Classification: 65.62, 65.75.