bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparison of forward masking for the monoaural and binaural hearing systems
Authors: Yama Mark F.
Published: October 2005

Forward masking functions were obtained using a 500-Hz tonal musket of 100-ms duration, followed by a 20-ms sinusoidal test probe at the same frequency. A continuous, broadband noise was also present during the experiment. Noise levels were chosen so that for long ISI's, masking functions for both the monaural and binaural system conditions would asymptote at a common level of signal detectability. In the monaural system condition, the masker, signal, and noise were all presented to one ear alone, while for the binaural system conditions, the signal was antiphasic, the noise homophasic, and the tonal masker was either homophasic or antiphasic. Results showed the mortaural system condition to exhibit the fastest recovery from masking. For the binaural system conditions, the homophasic tonal masker was more effective than the antiphasic masker when masker and signal were temporally nonoverlapping, but the reverse was found for simultaneous presentation of signal and masker. These data are interpreted as demonstrating that the binaural system has a longer integration time than does the monaural system. [Work supported by the Neurobehavioral Sciences Program, University of Iowa.]
Temporal integration of forward masking in normal and hearing-impaired listeners
Authors: Kidd G. , Feth L. L. , Corban M. , Beachler C.
Published: October 2005

Listeners with cochlear pathology often demonstrate less temporal integration at threshold than normal listeners. One explanation for that finding is that the pathologic ear is prone to excessive fatigue or adaptation to brief sounds. If this is indeed the case, it might be expected that the growth of forward masking with masker level would be less influenced by masker duration for listeners with sensorineural losses than for normal-hearing listeners. To test this hypothesis, we measured the growth of tonal forward masking as a function of masker level at several different masker durations for both normal-hearing and cochlear-impaired listeners. Masker duration ranged from 35 to 500 ms and probe duration was 20 ms with a 10-ms masker-probe time delay. In addition, unmasked probe thresholds were measured for probes ranging from 20 to 500 ms. Generally, it was found that those hearing-impaired listeners demonstrating less-than-normal temporal integration at threshold, also showed little effect of varying masker duration for forward masking. This suggests that integration of energy at probe threshold and integration of masker energy for forward masking are related phenomena. [Work supported by a David Ross Fellowship from Purdue University and grants from N.I.H.]
Summating potentials recorded from guinea pig round window
Authors: Koch Dawn Burton
Published: October 2005

Summating potentials (SP) were recorded from the round window of guinea pigs for frequencies 500–18 000 Hz and intensities 10–80 dB SPL. Stimuli were trapezoidal tone bursts with rise-fall times of 2.5 ms and plateaus of 40 ms. High-frequency stimuli (8–18 kHz) produced an SP+ for all intensities while low-frequency stimuli (0.5–1 kHz) elicited an SP− for intensities up to 70 dB SPL. Mid-frequency stimuli (2–4 kHz) showed a negative-to-positive polarity shift as intensity was increased. These results indicate that round window SP magnitude and polarity closely approximate those recorded from a single electrode in the scala tympani of the first cochlear turn [Dallos et al., Acta Oto-Laryngol. Suppl. 302 (1972)]. Furthermore, these measurements are analogous to the SP recorded from the human promontory [J. Eggermont in Electrocochleography, edited by Ruben et al. (1976)] and imply that both responses are dominated by first turn scala tympani activity. [Supported by NINCDS grant NS06730.]
Application of acoustic microscopy to measurement of elastic parameters of living cells
Authors: Rugar Dan , Hildebrand John
Published: October 2005

The scanning acoustic microscope operating at 1.7 GHz with resolution of 0.7 μ has been used to record reflection images of living cells cultured on various substrates. The character of the observed acoustic contrast changes dramatically as a function of the focal position of the object. At some focal positions the cell is seen with concentric bright and dark rings which appear to be correlated with cell topography. At other focal positions images with more uniform contrast are observed. A theoretical model has been developed to explain the dependence of contrast on focal position. Acoustic parameters of the cell (e.g., velocity, impedance and attenuation) may be chosen to give good agreement between the model and experimental data. [Work supported by NIH].
Diagnosis of narrowing in arteriosclerosis
Authors: Kinney Brian M. , Lees Robert S. , Stevens Kenneth N. , Kamm Roger D.
Published: October 2005

Spectral analysis of the sounds of arterial turbulence (phonoangiography) is the basis of an accurate non-invasive method for quantifying arterial narrowing. In 90% of patients the diameter can be easily determined using the phonoangiographic equation, d = Ulf, where U is flow velocity, and f is the break frequency. However, in 10% of patients, sharp resonant peaks in the lower frequency range (50–300 Hz) obscure determination of the turbulent break frequency, and thus the diameter. In a laboratory model of structural resonance, we have controlled flow velocity, stenosis diameter, mean pressure, and length of the vessel. Vessel vibrations were measured using a fiberoptic sensor, recorded on tape and analyzed by computer. The actual diameter of the stenosis was compared with that obtained by phonoangiography, and agreed to within 0.1 mm (>10%). The relationship between frequency of resonant peaks and length of the vessel was linear (r = 0.99) and independent of flow conditions. Using a theory based on the Moens-Korteweg derivation for pressure-induced dilational waves in vessels, theoretical frequencies of resonance were calculated and agreed with the actual values to within 10%. This suggests that structural resonance may superpose on an existing turbulent spectrum. Identifying resonant frequencies clarifies the determination of stenosis diameter.
Piezoelectricity in polymers
Authors: Sessler G. M.
Published: October 2005

Certain polymer materials, when electrically charged, exhibit a strong piezoelectric effect. Most prominent among these is polyvinylidene fluoride (PVDF) whose piezoelectric behavior was discovered only about a decade ago. In the present paper, the various change storage effects in PVDF and other polymers will be described, and the relation between the electrical polarization and the piezoelectricity discussed. The applications of these materials in electroacoustical and electromechanical transducers and in other devices will also be reviewed.
A new discovery of Wallace Clement Sabine papers
Authors: Kopec John W.
Published: October 2005

Twenty-two correspondence files of Wallace C. Sabine, discovered recently at the Riverbank Laboratory, contain a rich supply of solutions to acoustics and noise control problems. Differing from his published papers (1) and notebooks (1), they are records of Sabine's extensive activities between 1909 and 1916 as an acoustical consultant. His projects covered auditorium acoustics, building noise transmission, the reduction of noise from industrial plants, and from machines. Of interest also are Sabine's findings on a constant-power sound source, his part in the invention of acoustic tile, and his policies and ethical standards as an acoustical consultant.
Some advanced applications of time delay spectrometry
Authors: Heyser Richard C.
Published: October 2005

Time delay spectrometry (TDS) is a spread spectrum technique which utilizes a signal stimulus of the form exp[i θ (t)]. Delay tracking filters process the response of a system to that stimulus. The information extracted from these filters can either be of the more conventional type used for analysis, including the complex frequency response, complex time response, and complex cepstrum, or it can be of types not now readily obtained from conventional techniques. The choice of θ (t) with higher curvature than that of a quadratic phase chirp can allow direct measurement of dispersive propagation characteristics, including mode splitting into compressional and shear seismic waves which are created in the enclosure walls from air acoustic sources and which travel faster than sound in air to arrive at a listening location prior to the direct air path sound wave. Time varying systems, in which a boundary or scattering object move in the test space, can be isolated and measured by appropriate choice of TDS stimulus and filter. Four-dimensional imaging of acoustic surfaces in a room is possible by coherent wavefront reconstruction from one or more sources processed by one or more microphone locations.
Energy time curve, etc, measurements of the decay rate, 60/T, and mean free path for the first 50 ms in small well-damped rooms
Authors: Davis Don
Published: October 2005

The temporal patterning, energy levels, and rates of absorption of early sound fields (first 50 ms) in small (under 10 000 ft3-300 m3) well-damped rooms is measured and evaluated. The rates of decay, 60/T, are measured via TDS-ETC techniques for the first three reflected spectra in three planes and the mean free path they constitute is calculated from the measurement data. Remarks on the relevance of past theory with regard to present measurements will be offered.
Histological assessment of cochlear damage in basilar membrane experiments
Authors: Leonard D. G. B. , Khanna S. M.
Published: October 2005

The condition of the cochleas in the basilar membrane experiments [Khanna and Leonard, J. Acoust. Soc. Am. Suppl. 1 67, S46 (1980)] was assessed by gross potential responses (CM and NI) and by histological assessment. For histology, cochleas were fixed in vivo immediately after the experiments. An epon-embedded surface preparation technique was used, as described by Liberman and Beil [Acta Otolaryngol. (1978)]. In an early series of cochleas, surgical preparation for the experiments included drilling of the petrous bone and nonsterile techniques. In the second series of experiments, no drilling was used and precautions were taken to minimize introduction of bacteria into the cochlea. Some of the factors which seem to be related to the damage were: (a) condition of the hair cells and stereocilia; (b) presence of macrophages; and (c) presence of clear vesicles under the inner hair cells. An attempt is made to correlate the histological damage with the degree of damage as measured with electrical potentials.
Effects of hypothermia on ionic movement in the guinea pig cochlea
Authors: Konishi Teruzo , Salt Alec N. , Hamrick Philip E.
Published: October 2005

Anesthetized guinea pigs were subjected to hypothermia. During cooling, cochlear microphonics and endocochlear potential decreased, but K+ and Na+ concentrations in both endolymph and perilymph were not significantly affected. The rate constant for K+ turnover was determined by uptake of 43K into the endolymph, when the perilymphatic space was perfused with artificial perilymph containing 43K. The rate constant for K+ decreased significantly in hypothermic guinea pigs, when compared with that in normal guinea pigs. The K+ conductance of the endolymph-perilymph barrier estimated from the rate constant showed a marked decrease in hypothermic guinea pigs and was comparable with the conductance calculated from the rate of change of the endolymph K+ concentration relative to the K+ electrochemical potential difference recorded during permanent anoxia. These results indicate that hypothermia not only suppresses the active K+ transport system but also decreases the K+ permeability of the endolymph-perilymph barrier.
Psychoelectrical and speech comprehension results obtained through electrical stimulation of the auditory nerve
Authors: Hochmair-Desoyer Ingeborg J. , Hochmair Erwin S. , Fischer Richard E.
Published: October 2005

For five completely deaf humans equipped with an implanted cochlear prosthesis based on electrical stimulation of the auditory nerve, phoneme and word discrimination and recognition have been determined (optimum recognition results of 70% for an open list of words have been achieved). These results are contrasted to psychoelectrical measurements like amplitude and frequency scaling and masking experiments. Both single channel and multichannel experiments with up to four channels have been performed leading to the result that in most cases single channel stimulation is sufficient to reach up to 80% comprehension of unknown sentences. The influence of the configuration of the stimulating field was also investigated. Bipolar stimulation leads to a steeper increase in subjective loudness as compared to stimulation against a common distributed intracochlear ground. Field extension concepts have been confirmed by masking experiments. Using a suitable compensation for the different slopes in the loudness scaling characteristics. no significant difference in speech comprehension results for bipolar stimulation and stimulation against a common intracochlear ground have been found.
Objective tonal tinnitus
Authors: Zurek P. M.
Published: October 2005

Objective tonal tinnitus (OTT) is a spontaneous and continuous narrowband acoustic signal that can be measured in many persons by placing a probe microphone in the ear canal. In a sample of thirty-two normal-hearing persons. sixteen possessed at least one OTT. These signals were most often found between 1.0 and 2.0 kHz at sound pressures in the occluded ear canal less than 200 μPa. Among several experiments with the author's own OTT at 1910 Hz was one in which the suppression of OTT by an external tone was examined. It was found that a contour of constant suppression (amplitude versus frequency of external tones that produce a criterion reduction in the amplitude of the OTT) exhibits frequency selectivity like that commonly associated with the cochlea. Objective tonal tinnitus provides a clear explanation for the phenomena connected with monaural diplacusis except for the aftertone, which does not have an observable acoustic correlate. The existence of objective tonal tinnitus of cochlear origin: (1) demonstrates that the ingredients for active biomechanical processes are present in the inner ear; and (2) suggests that such processes are employed to increase the sharpness and sensitivity of mechanical frequency analysis in the cochlea. [Work supported by NIH.]
A quantitative study of some nonlinear aspects of drop shape oscillations
Authors: Trinh Eugene , Wang Taylor
Published: October 2005

The small amplitude analysis of shape oscillations of drops is generally performed within the framework of the linear harmonic oscillator theory. When the vibration-induced deformations become large, however, one might expect that such an approach would no longer yield the correct behavior. Controlled experimental studies of such large amplitude effects for drops immersed in liquid hosts are not available at the present time. Thus, we would like to present new experimental results pertinent to the nonlinear characteristics of large amplitude oscillations. A significant decrease (6% to 7%) in the frequency of the fundamental mode has been obtained for deformed ellipsoidal shapes having axial ratios up to 1.5 when the appropriate drive is used. The decay constant for this mode shows an increase with larger deformations. Were the drops to be statically deformed in the nonvibrating state, a substantial increase in the resonance frequency would be detected. Finally, the outcome of a detailed photographic analysis of drop motions during steady-state oscillations will be communicated. [Work supported by NASA under contract No. NAS 7-100.]
Equilibrium positions of acoustically levitated spheres
Authors: Stoneburner J. , Barmatz M. , Jacobi N.
Published: October 2005

Measurements of the equilibrium position of levitated, low-density spheres in air were made in a rectangular resonant system as a function of acoustic pressure. Vertical acoustic forces were generated by two opposing JBL compression drivers exciting the fundamental plane-wave mode at 1.2 kHz. Additional acoustic forces in the horizontal plane centered the sample along the vertical axis. The sample equilibrium position is determined by a balance between the gravitational and acoustic forces. A cathetometer measured the sample position to better than ±0.03 cm for sound-pressure levels up to 160 dB. The dependence of equilibrium position on acoustic pressure and sample radius will be compared to theoretical prediction [N. Jacobi and M. Barmatz, Proceedings of the 1979 Ultrasonic Symposium, IEEE Cat. ♯79CH1482-9SU, p. 476]. [Work supported by NASA.]
Shock wave measurements with a matched-impedance, condenser hydrophone
Authors: Clark J. A.
Published: October 2005

Precision measurements of the instantaneous-pressure history of large amplitude, waterborne sound and shock waves are difficult to obtain with currently available electromechanical transducers such as PZT hydrophones and tourmaline pressure gages. One source of the difficulty is the poor phase response of these probes. A new type of condenser hydrophone has been designed which appears to significantly improve the precision of instantaneous pressure measurements. The hydrophone is built with a dielectric material between the condenser plates which is similar in acoustic impedance to that of water. A theoretical analysis of this design shows that the acoustic sensitivity of a matched-impedance hydrophone is (−2Vμ/β) volts per Pascal, where Vp is the polarizing voltage across the condenser and β is the compressibility modulus of the dielectric material. The sensitivity is found to be constant over a very broad frequency range and is not significantly changed by hydrostatic pressure, temperature or the dynamic range of signals. Experimental comparisons of the response of matched-impedance, condenser hydrophones with other transducers have been obtained with a laboratory facility for the generation of repeatable underwater shock waves. [Research supported by ONR.]
Phase-locked loop demodulator for a parametric receiver
Authors: Lamb R. A.
Published: October 2005

The parametric acoustic receiving array (PARRAY) exhibits a response to transducer vibration that is significantly different from a linear array. In some applications, low-frequency transducer vibration may degrade PARRAY performance since Doppler modulation of the PARRAY signals caused by transducer vibration produces a convolution of the acoustic and vibration spectrums. A phase-locked loop demodulator has been developed that can reduce the detrimental effects of transducer vibration on the PARRAY. The processor is described and theoretical and experimental results demonstrating the effectiveness of the receiver are presented.
The parametric receiver in a thermally inhomogeneous medium
Authors: Culbertson C. R.
Published: October 2005

A theory is presented for the effects of thermal inhomogeneities upon the performance of a parametric receiver. It is assumed that the medium is weakly scattering so that acoustic amplitude and phase fluctuations remain small compared to unity. Expressions are found for the mean-square amplitude and phase fluctuations in the second-order pressure field. Both nearfield and farfield parametric receivers are considered. The performance of the parametric receiver in a thermally inhomogeneous medium is compared to that of a conventional end-fired array and of a point hydrophone.
Perceptual (ir)relevance of the envelope features: steady time versus decay time
Authors: Heuven Vincent J. van , Newman Roxana Ma
Published: October 2005

Rise (± interrupted) and decay time (± checked) of speech sounds have often been proposed as distinctive features with perceptual correlates. Production data will be presented from Hausa, a Chadic language from Africa, suggesting that the prepausal pure vowel short-long contrast is exclusively characteristic by decay-time differences. In the corresponding perception experiment steady time and decay time were orthogonally varied, observing equal ranges and stepsize, and amply covering the parameter space found in the production experiment. Results indicate that decay time does not contribute more to the contrast than steady time. It will be argued that the Jakobson, Fant, and Halle feature (± checked) is without perceptual correlates in the case of vowels; an explanation will be sought in the poor auditory discriminability of rise and decay time phenomena [V. J. J.P. van Heuven and M. P. R. van den Broecke, J. Acoust. Soc. Am. 65, 1308–1315 (1979); M. P. R. van den Broecke and V. J. van Heuven, preceding abstract]. [Work supported in part by the Netherlands Organisation for the Advancement of Pure Research, Z. W. O.]
Context-sensitive coding in speech perception
Authors: Marcus Stephen Michael
Published: October 2005

Many problems in speech recognition result from the representation and storage of speech as a linear temporal sequence. It is proposed, following Wickelgren [Psych. Rev. 76, 1–15 (1969)] that speech should instead be represented by a nonsequential associative or context-sensitive code. A computer simulation, ERIS, is presented to demonstrate the viability and power of such an approach. The use of recognition element activity as a correlate of stimulus time is also proposed as a novel means of representing temporal information. No intermediate processing levels between the acoustic stimulus and word recognition are assumed, and it is suggested that through such an approach it will become apparent what intermediate levels may be either necessary or useful. The power of even this relatively unsophisticated simulation suggests that context-sensitive coding and direct acoustic-lexical mapping are important principles to be considered in any approach to understanding and modelling human speech perception.
A top-down effect on the identification of function words
Authors: Isenberg David , Walker Edward C. T. , Ryder Joan M.
Published: October 2005

A realistic-sounding /tə-ðə/ continuum was constructed by successively attenuating the amplitude of the burst + aspiration interval of a naturally produced /tə/. Members of the series were placed before the words “go” and “gold” in two sentence contexts: “We tried-go/gold,” and “-go/gold is essential.” Listeners were asked to identify the critical tokens as “to” or “the.” A shift in the phonetic boundary was evidenced in both sentence frames. Specifically, more “to” responses were made in the “go” contexts and more “the” responses were made in the “gold” contexts. A second experiment is in progress that is designed to ascertain whether effects of syntactic category are present in the absence of linguistic anomaly by using syntactically ambiguous words in the experimental context (e.g., “I like-joke/drive”.) [Work supported by NIMH, NINCDS, and NICHD.]
Perceptual contributions of anticipatory coarticulation
Authors: Martin James G. , Bunnell H. Timothy
Published: October 2005

In experiments reported by us at earlier meetings, the stimuli were sentences (e.g., “I say poozee”) of the form “I say/C V1 z V2/” in which C was /p, t, k/, V1 was /u, ae/, and V2 was /i, a/. Each /i, a/ sentence pair was cross-spliced by exchanging the final syllable /z V2/and recognition time (RT) obtained to V2 in crossed and intact (as spoken) sentence versions. The results were slower RT in crossed sentences, suggesting misleading coarticulatory information prior to the cross. LPC analysis showed pretarget variations in formant movement were jointly dependent on identity of C, V1, and V2 and were correlated with RT interference in crossed sentences. The present paper reports acoustic and perceptual results of effects of anticipatory coarticulation between other V1-V2 combinations and across other consonant classes. [Supported by NINCDS.]
Faulty timing degrades speech intelligibility
Authors: Huggins A. W. F.
Published: October 2005

Studies of deaf speech frequently cite faulty timing as a major cause of poor intelligibility. Yet modifying the timing of normal speech seems to have so little effect on its intelligibility that formal quantification is not worthwhile. Usually, however, the person who modifies the timing also knows what the utterance said, and therefore is not forced to rely on what he or she hears to establish its prosodic pattern. When formal tests are run, sentences that appeared perfectly acceptable to the experimenter suddenly become unintelligible to the subjects. An experiment will be reported comparing the intelligibility of monotone speech synthesized by rule under four conditions: (1) segment durations assigned by rule, (2) equal duration for all segments, (3) equal duration for all syllables, and (4) equal duration for all metric feet.
Perception of the duration of rapid spectrum changes: Evidence for context effects with speech and nonspeech signals
Authors: Carrell Thomas D. , Pisoni David B. , Gans Susan J.
Published: October 2005

For a number of years investigators have focused attention on the effects one acoustic segment has on the perception of other acoustic segments. In one study, Miller and Liberman [Percept. Psychophys. 25, 457–465 (1979)] reported that overall syllable duration influences the location of the labeling boundary between the stop /b/ and the semivowel /w/. They claim that this “context effect” reflects a form of perceptual normalization whereby the listener somehow readjusts his perceptual apparatus to take account of the difference in rate of articulation of the talker. More recently, Eimas and Miller [Science (in press)] have reported that prelinguistic infants also show similar context effects in discrimination of these stimuli. The inference drawn from the latter study is that infants perceive these speech sounds like adults and the context effects reflect the operation of perceptual mechanisms that underlie a phonetic-like mode of processing specific to speech. In the present study, we carried out several critical comparisons between speech and nonspeech signals and observed comparable context effects for perception of the duration of rapid spectrum changes as a function of overall duration of the stimulus. Our results with nonspeech signals falsify both of the earlier claims by demonstrating clearly that these sorts of context effects are not peculiar to the perception of speech signals or to normalization of speaking rate. [Work supported by NIMH Research Grant MH-24027-06.]
Onset spectra versus formant transitions as cues to place of articulation
Authors: Walley Amanda C. , Carrell Thomas D.
Published: October 2005

Stevens and Blumstein [J. Acoust. Soc. Am. 67, 648–662 (1980)] have proposed that the shape of the onset spectrum of a CV syllable provides listeners with a primary and contextually invariant cue to place of stop-consonant articulation. Contextually variable formant transitions, on the other hand, are claimed to constitute only “secondary” cues to place of articulation that are learned through their co-occurrence with the primary spectral ones. The present experiment assessed this claim about the relative importance of these two cues by obtaining listeners' identifications of synthetic stimuli whose onset spectra were matched to the Stevens and Blumstein spectral templates, but which contained conflicting transitions cues to place of articulation. The results indicated that listeners use formant transition information more often than the information contained in the stimulus onset—a result which argues against Stevens and Blumstein's claim that the static onset spectrum is the primary cue to place of articulation. However, because some listeners did consistently use the onset spectra cue for identification of place of articulation, it would seem that several perceptual strategies can be used in phoneme identification. [Work supported by NIMH and Research Council of Canada.]
Acoustic signals of nonthermal origin from high energy protons in water
Authors: Hunter S. D. , Jones W. V. , Malbrough D. J. , Van Buren A. L. , Liboff A. , Bowen T. , Jones J. J. , Learned J. G. , Bradner H. , Pfeffer L. , March R. , Camerini U.
Published: October 2005

Acoustic pulses generated by the passage of 30-GeV protons through water show evidence for the presence of a nonthermal source. In addition to the bipolar leading-compression signal expected from thermal shock, a tripolaf leading-rarefaction component is observed. This component is dominant at 4°C, where the thermal signal should vanish. A space-charge effect may be the source of this component, since other proposed mechanisms leading to tripolar pulses should give a leading-compression signal.
The effects pitch-distorbed feedback on vocal productions
Authors: Elman Jeffrey L.
Published: October 2005

Previous investigations into the effects of distorted auditory feedback on vocalizations have been limited to manipulations of intensity, background noise, or delay in arrival time. The current study reports the results of real-time distortions of the frequency components of auditory feedback. Subjectively, such distortion is perceived primarily as an alteration in the fundamental frequency of the speech. Subjects performed a variety of tasks under conditions where they received either normal auditory feedback (NAF) or pitch-altered feedback (PAF). NAF performance was consistently good; PAF performance was quite poor. Subjects attempted to compensate for the frequency alterations by adjusting their fundamental frequency up or down such that the resulting feedback appeared to be “normal.” [Work supported by NSF.]
Rays and modes in an underwater channel with exponential velocity profile
Authors: Cho S. H. , Felsen L. B. , Niver E.
Published: October 2005

High-frequency underwater sound propagation in the ocean is usually analyzed either in terms of a normal mode expansion or in terms of ray acoustics. These formulations lead to difficulties when the number of required modes or rays is excessively large. Moreover, ray acoustics requires corrections near caustics and cusps of the ray system and actually becomes inapplicable in a surface duct where the ray fields may experience an arbitrarily large number of reflections. To alleviate these difficulties, we apply a newly developed theory that utilizes a judiciously chosen mixture of ray fields and modal fields to represent the signal due to an oscillating line source at various depths, observed at different depth and range intervals. The ocean is modelled by an exponentially increasing sound velocity between the free surface and a homogeneous semi-infinite bottom. This environment combines surface-duct and waveguide phenomena. The nature of the hybrid formulation for surface-ducted fields and fields guided by top-bottom interaction is studied in detail, as is the possibility of choosing the ray-mode mixture so as to avoid corrections near caustics and cusps of the ray-acoustic pressure field. [Work supported by ONR Ocean Acoustics Branch.]
A finite-difference treatment of interface condition for the parabolic wave equation
Authors: Lee Ding , McDaniel Suzanne T.
Published: October 2005

An elegant finite-difference approach is introduced to handle the interface conditions between two layered media with different sound speeds and densities for the parabolic wave equation. Continuity of pressure as well as continuity of vertical particle velocity are preserved. The method is designed to be implicit and is unconditionally stable. The resulting mathematical expression is short. Since the entire procedure is systematic, it becomes easy to implement into computer programs. At every interface, it requires only a few scalar operations, thus, no additional memory capacity is required. Details of the mathematical treatment of the fiat boundary will be described. Test results are shown to compare with FFP results. A generalization to handle irregular interfaces will be outlined.
Pertubed ray theory via a bifurcation theory analysis
Authors: Watson John G. , Siegmann W. L. , Jacobson M. J.
Published: October 2005

A perturbation approximation to the total geometrical acoustic field is obtained by a bifurcation analysis of the nonlinear ray equations. The approximation, perturbed ray theory, is specifically designed for underwater acoustic applications. The method is first demonstrated for an arbitrary, depth-dependent, sound channel with source and receiver at the SOFAR axis. Using the theory of imperfection bifurcation, these results are extended to include horizontal sound-speed variations and more general source-receiver geometries. The dependence of total field on sound-speed profile and geometry is investigated in general, and specifically illustrated using Eckart and Epstein profiles. [Work supported by ONR.]
Normal-mode propagation in deep-ocean sediment channels
Authors: Williams A. O.
Published: October 2005

E. L. Hamilton has discussed the likelihood of ducted acoustic transmission in deep-ocean sediment channels, just below the water-bottom interface. The normal-mode solution is presented here; it yields eigenfunctions, the associated eigenvalue equation, and the minimum acoustic frequency that allows trapping of any specified mode. This frequency increases nearly linearly with mode number. Much of the acoustic energy propagated by any trapped mode travels through lossy bottom sediment. Accordingly, equations are derived for the attenuation coefficient of the nth mode. Numerical results are given for an “average” channel at a frequency of 100 Hz. [This work was sponsored by Naval Electronic Systems Command and Naval Ocean Research and Development Activity.]
Airport planning and the environmental impact process: The level of effectiveness
Authors: Bragdon Clifford R.
Published: October 2005

Since the passage of the National Environmental Policy Act (NEPA) in 1969 all federally funded activities, including airport development, has had to prepare an environmental impact assessment (E1A). Noise, among other factors, has had to be discussed including abatement methods to minimize the noise, such as land use controls. To date there has not been a review of the EIS process in terms of airports. This paper evaluates the overall process of review as it has been practical. A series of 100 airport master plans was evaluated in terms of noise impact and control. Further consideration was given to the implementation of these control strategies. Land use control was specifically addressed. Results show that noise does not consistently get evaluated in airport master planning. In those situations where noise is recognized, land-use compatibility is not always recommended. It was further found that the requirements of land-use assurance agreements in the long run do not insure that compatible development will result. Recommendations are made to strengthen this present weakness. [Work in part supported by EPA.]
Cost versus noise exposure reduction tradeoff analysis for the future commercial jet fleet
Authors: Rackl Robert
Published: October 2005

The purpose of this study was to investigate possible future aircraft-noise certification policies for civil aircraft in the United States. The cost effectiveness of various noise-exposure reduction options were compared with each other. The options were grouped into three categories: aircraft source noise reductions, flight path (operational) alternatives, and land-use options. Among the source options were application of sound-absorbing nacelle liners, use of large bypass ratio engines, and use of long duct nacelles. The operational alternative consisted of a special takeoff cutback procedure. Among the land-use options were improved building insulation for existing and future structures, and relocation of people. For the planning years 1980, 1990, and 2000, the noise impact for the future fleets and expected new aircraft configurations was evaluated. For various scenarios of the future, equivalent noise-exposed populations were calculated at a sample of 14 airports representative of the nation, using the A-weighted average noise level as the underlying noise metric. The cost differentials between scenarios with a particular combination of noise-exposure reduction actions and a “do-nothing” scenario were calculated and compared to the accompanying reduction in people noise exposure. Thus, the most promising scenarios could be identified. [Work supported by FAA.]
The effect of ground cover on truck pass-by A-weighted sound level measurements
Authors: Hellweg Robert D.
Published: October 2005

To determine the effect of different ground covers on sound-level readings, A-weighted sound levels [dB(A)] from more than 1000 trucks were measured with 16 pairs of microphones. For each pair, one microphone was located on a “hard” site and the other on a “soft” site (a soft site occurs when grass cover is (12) or more of the distance between the microphone and the center of the lane of travel). The microphones were used at three locations simulating typical enforcement of vehicle noise regulations and varied from 41.5 to 71 ft from the center of the lane. As a truck passed each pair of microphones, the maximum dB(A) was recorded and the difference determined. Results indicate that as the amount of grass cover increases, the dB(A) difference between a hard and soft site increases; however, the average dB(A) difference for hard and soft sites is less than the correction factor used for enforcement of the Interstate Motor Carrier Noise Emission Standards.
The annoyance of helicopter noise with impulsivity varied by phase shifting
Authors: Ahumada A. , Fish R. S. , Henckel P.
Published: October 2005

Annoyance ratings to four digitally synthesized helicopter sounds were collected. Two were relatively impulsive; a standard helicopter-pulse waveform produced according to the model of Schmitz and Yu (European rotorcraft and powered lift aircraft forum, France, 1977), and its cosine phase equivalent. The other two sounds were substantially less impulsive. They were low peak stimuli produced from the standard waveform by randomizing the phase relations among its Fourier components. All four stimuli had identical Fourier series amplitude spectra. The four synthesized sounds were utilized in a within-subject factorial design with each sound presented at pulse frequencies of 10 and 20 Hz and levels of 89 and 95 dBA. The pulse trains lasted for 3 s for one group often subjects and 12.5 s for another ten subjects. In addition, another group of ten subjects with a mean age of 36 rated the sounds. All groups rated the more impulsive sounds significantly less annoying. The magnitude of this effect was 2.7, 3.5, and 4.5 dB for the three groups, respectively. This result indicates that previous studies in which the power spectra across impulsive and nonimpulsive sounds was not held constant and which found that impulsivity resulted in increased annoyance ratings may have been contaminated by this deficiency. [Work supported by NASA Langley Research Center.]
Effects of conversation interference on annoyance due to aircraft noise
Authors: Key Kelli F. , Powell Clemans A.
Published: October 2005

The annoyance and interference effects of aircraft flyover noise on face-to-face conversation were investigated. Twenty 5-rain sessions of three flyovers for each session were presented to each of 20 pairs of female subjects in a simulated living room. Flyovers varied in noise level (55–79 dB A-weighted) and spectrum (low-or high-frequency components). Subjects engaged in conversation for 10 sessions and in reverie for the other 10 sessions, and completed subjective ratings following every session. The ratings concerned the annoyance of the noise, the difficulty of conversing in the noise, and acceptability of the noise for conversation. Conversation interference was defined as an increase in vocal effort or cessation of talking during flyovers for each session. Annoyance was affected by noise level, but was not significantly different for the activities—reverie and conversation. A noise level of 77 dB (A-weighted) was found to be unacceptable for conversation by 50% of the subjects. Furthermore, conversation-interferance measures did not improve prediction of individual annoyance judgments.
Field testing of earplugs for noise reduction using a supra-threshold procedure
Authors: Fleming Roy M.
Published: October 2005

A new procedure for testing the noise reduction of earplug hearing protectors in the field was developed and evaluated. The new procedure involves a midline lateralization (ML) technique that is similar to loudness balancing. Advantages of the new procedure include elimination of the need for a special test space with very low ambient-noise levels, short test time, and probable avoidance of interference from physiological noise that may be present in hearing-threshold testing. This procedure provides a means of monitoring hearing protectors to help ensure adequate noise reduction for individuals working in noisy occupations. Noise reduction was measured for two models of earplugs. Subjects were scheduled for test sessions and were asked to insert their earplugs as they normally did on their jobs. Values of noise reduction from the scheduled tests ranged from 0–35 dB and 45 dB for the two models of earplugs. Noise reduction results by the ML procedure agreed well with results by a hearing threshold-shift procedure. [Supported by NIOSH while at Harvard School of Public Health.]
The capabilities and limitations of microprocessors and their influence on present and future acoustical instruments and analyzers
Authors: Manning R. L.
Published: October 2005

Microprocessor technology will bring a wealth of instrumentation capability to the acoustical engineer in the future. Some of the past instrumentation has been plagued by heavy, large, power-consuming packages with limited calculating capability. Tube-type systems fell into that category. The transistor aided by minimizing package size and power consumption. Micrologic chips from the space program have further aided by allowing more sophisticated processes to be analyzed. The latest step in this direction has been a large-scale integration of micrologic (LSI) called microprocessors. The microprocessor itself is divided into classifications depending upon speed, ease of use, ease of programmability, ease of development and cost. This diversity includes “BitSlice”, 8-bit MOS, 16 bit MOS, Single Chip, and CMOS microprocessors. When the user understands some of the advantages and disadvantages of various microprocessor techniques and can communicate his requirements to the design engineer, then instruments can be developed which will not be blatant overkill on the one hand or redundantly simplistic devices on the other. Then the user will aid the designer to an optimal design for maximum usefulness at minimum cost, development time, and complexity.
Microprocessor-based building acoustics analyzer
Authors: Thomsen Carsten
Published: October 2005

A battery-operated analyzer incorporates all necessary measurement capabilities in one portable unit. This includes noise generator, 13-octave transmit and receive filters, detector and averaging system, plus a built-in microprocessor for post-processing of data as well as automatic control of the instrument and peripherals such as rotating microphone boom, microphone multiplexers, analog level recorder, digital printer and digital cassette recorder. Based on the automatic measurement of reverberation time and 13-octave spectra in transmit and receive rooms, the following are computed: Standardized and normalized level difference and impact level, insulation index and impact index to ISO 140 and ISO R 717. Automatic correction for background noise as well as sound power computations are included. The results can be plotted in analog form or printed digitally together with error codes, if any, indicating measurement errors (such as excessive noise, overload, microphone failure) or calculation errors such as improper surface areas or room volumes. A special manual mode allows the user to key in simulated data to evaluate the influence on the acoustic environment by, for example, reducing the reverberation time at 100 Hz by 25%.
Use of metal spheres as calibration devices for acoustic scattering measurements
Authors: Numrich S. K. , Frank L. J. , Dragonette L. R.
Published: October 2005

Tungsten-carbide spheres may be used as calibration targets in laboratory acoustic-scattering measurements. The steady-state response of any metal sphere in water greatly differs from a rigid body return over almost the entire frequency spectrum; however, the rigid body and elastic returns can be separated in a short pulse, broadband experiment. This rigid-body echo can then be used as a reference to normalize the scattering returns from targets of interest.
Ultrasonic model studies of Rayleigh wave scattering
Authors: Chamuel Jacques R. , Toksoz M. Nafi
Published: October 2005

The effects of surface irregularities on the propagation of Rayleigh waves are studied using two-dimensional seismic ultrasonic models. Specially designed contactless transducers (Chamuel, U.S. Patent Number 4,035,762, July 1977), in the form of electromagnetic coils, were used to generate and detect the ultrasonic waves in magnetostrictive sheets. The contactless transductions are based on the Joule and Villari effects. One type of transducer consisting of a folded circular coil was used to detect the longitudinal component of the surface waves propagating along the edge of the magnetostrictive sheet. A second type of transducer was used to measure the body wave generated by the surface waves upon reflections from the surface irregularities. Several shapes such as steps, ramps, pyramids, and rectangular obstacles were machined along the edges of the magnetostrictive sheets. Nickel 200 was chosen for the experiments. The data obtained from the experiments clearly showed the transmission. reflection, and mode conversion of the wave at the boundaries. The dimensions of the surface irregularities were comparable to the dominant wavelength.
Anatomo-physiological correlation in vestibular afferent neurons of frogs (rana catesbiana)
Authors: Honrubia V. , Sitko S. , Betts W. , Kimm J. , Schwartz I.
Published: October 2005

The morphological characteristics of physiologically identified neurons innervating the horizontal and vertical semicircular canals of rana catesbiana were investigated following intra-axonal horseradish peroxidase injections. Two distinct types of neurons were found. “Regular neurons” had spontaneous firing rates with a low (0.12 to 0.5) coefficient of variation (CV) while “irregular neurons” had CV > 0.5. Morphologically, the cell bodies of regular neurons had smaller diameters than irregular neurons: 7.1 ± 2.0 μm vs 12.7 ± 3.0 μm longitudinally and 4.9 ± 1.4 μm vs 7.6 ± 1.3 μm transversely. Small neurons were located in the antero-ventral and large neurons in the dorso-posterior portion of the anterior vestibular nerve. Differences were also found in the characteristics of response to physiological stimuli. During 0.5-Hz rotation, gain and phase of regular and irregular neurons were 0.98 ± 0.87 spikes × s−1/deg × s−1 and 2.7 ± 18.6 degrees relative to head velocity and 3.02 ± 0.7 spikes × s−1/deg × s−1 and 29.7 ± 9.6 deg, respectively. The time constant of the response decay to an impulse of acceleration was 6.77 ± 5.1 and 4.4 ± 1.05 s for regular and irregular, respectively. In conclusion, although frogs have only type II hair cells, they have two types of vestibular afferents with characteristics similar to those found in mammals.