bluuebunny/crossref_metadata_2025 huggingface dataset:
Localization of clicks, noise bursts, and tones by an Indian elephant
Authors: Hefther Rickye , Hefther Henry
Published: October 2005

The availability of the two binaural sound localization cues, time and intensity, is primarily determined by the distance between the two ears (interaural distance). To determine the effect of a very large interaural distance on sound localization, the ability of an elephant to localize sound was determined. The elephant was tested using a two-choice procedure in which the animal pressed an “observing” button to initiate a trial and then pressed one of two adjacent response buttons to indicate whether the sound came from a loudspeaker located to the left or right of midline. The elephant proved able to localize single clicks and brief bursts of white noise quite accurately with thresholds as low as one degree.When tested with brief tone pips, the elephant could localize tones from 125 Hz to 2 kHz with little difficulty, but was barely able to localize 4- and 8-kHz tones. In contrast, the elephant had no difficulty localizing narrow-band noise bursts from 125 to 8 kHz, stimuli for which a time cue is available in the envelope of the signal. These results suggest that while the elephant is able to use both time and intensity cues, it relies primarily on time cues for the accurate localization of sound. [Work supported by NSF.]
Development of the auditory orientation response in rats
Authors: Judge Peter W. , Kelly Jack B.
Published: October 2005

An index of auditory head orientation was employed to determine the onset and development of directional responses to sounds in the rat. The effects of monaural ear blockage and early monaural deprivation on the orientation response were also studied. Testing involved placing a rat in a small cage and presenting an occasional brief noise burst on the animal's left or right. A television monitor provided an overhead view of the animal's response. Rat pups were tested at postnatal days 8, 11, 14, 17, and 20. The first evidence of a directional response was seen on day 14 with a dramatic increase in accuracy on days 17 and 20. In further studies, it was found that wax earplugs inserted in one ear disrupted directional responses. However, animals raised with one ear blocked during the period from day 13 to day 27 did not subsequently show signs of behavioral disruption when tested immediately following removal of the ear plugs. Thus, under the conditions of this experiment, there was no evidence of impairment following monaural deprivation. [Supported by NSERC grant 7654.]
The relation between sensation level and frequency discrimination under conditions of informational masking
Authors: Watson C. S. , Lehman J. R. , Kelly W. J.
Published: October 2005

Previous studies of resolution of the frequency, intensity, and duration of individual elements of word-length tonal sequences have shown major degrading effects of trial-to-trial stimulus uncertainty. The same degree of stimulus uncertainty was recently found to cause elevations of detection thresholds of 40–50 dB above the levels expected from temporal masking [Watson, Kelly, and Mellen, J. Acoust. Soc. Am. 66, S83 (1979)]. We referred to the effect of stimulus uncertainty on the threshold of individual elements of patterns as informational masking. In the current experiment, we investigated the relation between the amount of informational masking and frequency discrimination for the same target tones. Detection and discrimination trials were interleaved in an adaptive psycho-physical sequence to measure observers' detection thresholds and frequency difference limens for a 45-ms, 1688-Hz target tone, presented 90 ms after the onset of a 10-tone pattern. Context (non-target) tones varied between 25–45, 35–55, or 65–85 dB SPL in level, 300–3000 Hz in frequency, and 25–105 ms in duration. Target-tone levels on frequency discrimination trials were 35, 45, 55, or 75 dB. Informational masking was found to increase 10 dB for each 10-dB increase in context level, essentially as does energy masking, although the source of the two effects is clearly different. At all negative sensation levels, the threshold values of ΔF were those required to shift target-tone frequency beyond the limits of the pattern bandwidth. Frequency discrimination improved systematically as current “effective” sensation level increased from 0.0 to 40–50 dB, yielding a range of just-detectable values of Δf from over 1000 to about 20 Hz. The relation between sensation level and frequency discrimination is thus quite similar for informational and energy masking. [Work supported by NIH.]
Pitch-intensity functions in impaired ears
Authors: Burns Edward M. , Williamson Susan J.
Published: October 2005

Mortaural-pitch-intensity functions were measured in observers with permanent losses in hearing sensitivity which were assumed, on the basis of audiological testing, to be of cochlear origin. Observers with low-frequency losses (normal high-frequency thresholds) and observers with broadband high-frequency losses (above about 1500 Hz) both showed abnormally large pitch shifts with changes in intensity (up to 5% per Bel) at low frequencies. On the other hand, observers with low-frequency losses and observers with losses only at very high frequencies (above about 4000 Hz) both showed essentially normal pitch-intensity functions in regions where their thresholds were within normal limits. The implications of these results for various tonotopicaily-based and temporally-based models of pure-tone pitch perception will be discussed. [Research supported by NINCDS.
Loudness recruitment in abrupt drop sensori-neural hearing impairment
Authors: Young I. M. , Lowry L. D.
Published: October 2005

Alternate monaural loudness balance tests were performed in eleven cases of abrupt drop sensori-neural hearing impairment. To study frequencies on the slope, two-octave Bekesy tracing measurements were made beginning at a frequency nearest to initiation of the slope with normal hearing. Loudness was matched between f1 (a frequency nearest to initiation of the slope) and f2 (a frequency nearest to termination of the slope) (test 1), f1 and 2f1 + f2/2 (a frequency halfway between f1 and f2) (test 2), and f1 and 2f1 (a frequency one octave above f1) (test 3). Our data indicated that combination of asymptotic and straight-line recruitment was shown in test 1, pure asymptotic recruitment in test 2, and straight-line recruitment in test 3. There was no correspondence between the shape of loudness recruitment curve and the slope of hearing loss or the excursion size of Bekesy tracings. It is postulated that diffuse hair cell lesions such as frequency areas in the vicinity of 2f1 in abrupt drop sensori-neural hearing impairment or endolymphatic hydrops may show straight-line recruitment and discrete outer hair cell lesions such as frequency regions around f1 + f2/2 or temporary threshold shift may demonstrate pure asymptotic recruitment. Our results were discussed in relation to histopathological findings of human and animal subjects with abrupt drop hearing loss.
Auditory temporal resolution in normal and brain-damaged subjects
Authors: Smiarowski Richard A.
Published: October 2005

The minimum perceptible separation between two successive bursts of broadband noise has been used as a measure of auditory temporal resolution by Plomp [J. Acoust. Soc. Am. 36, 277–282 (1964)] and Smiarowski and Carhart [J. Acoust. Soc. Am. 57, 1169–1174 (1975}]. By varying the relative level of the trailing noise burst, these investigators provided information about the time course of the decaying auditory excitation from the leading noise burst. Using the same paradigm as these earlier studies, the present paper shows how the presence of various types of central auditory pathology in human subjects can alter the time course of this decay function. This data has implications for auditory persistence in the normal and pathological auditory systems. [Supported by the Medical Research Service of the Veterans Administration.]
A procedure for detecting variability of psychophysical thresholds
Authors: Hall J. L.
Published: October 2005

In adaptive psychophysical testing, it is desirable to identify experimental runs during which the subject's threshold changes. This is not easy to do, because the testing level changes during the course of the run. The following screening procedure can assist in detecting threshold variability. At the conclusion of the run, make a maximum-likelihood estimate of the psychometric function. That is, for some assumed parametric form of the psychometric function, determine values of the parameters that maximize the probability of the observed set of responses. Next, for each trial determine the value of the random variable Z = Y − Px(C). Px(C) is the probability of a correct response at testing level x, given by the fitted psychometric function, and Y is a random variable equal to 1 for a correct response and equal to 0 for an incorrect response. Finally, determine the slope of the linear regression of Z upon trial number. If the subject's response behavior is stable, then E(Z) = 0 regardless of testing level and the expected value of slope is equal to zero. If the observed slope differs greatly from zero, then it is unlikely that the subject's response behavior is stable. Results from computer simulations and psychophysical experiments are presented.
The loudness of harmonic versus nonharmonic two-tone signals
Authors: Papsin Blake C. , Clack T. Dean
Published: October 2005

Phase relationships between the components of a harmonic complex influence the loudness of the signal (Chapin and Firestone, 1933). For nearly-harmonic components, phase varies continuously. In this experiment, the loudness of two-tone complexes consisting of equal-amplitude components with 500-Hz frequency separations are compared. The loudness matches are obtained using a method of adjustment, and monaural alterations of nonharmonic versus harmonic signals. The phase angle between the harmonic components is varied in 60° steps through one complete period of the higher frequency tone. Preliminary findings appear to confirm the expected cyclic variations in the loudness of the harmonic complex. The nonharmonic signals, however, always seem to be the louder.
Production and perception of phonetic contrast during phonetic change
Authors: Costa Paul , Mattingly Ignatius G.
Published: October 2005

In ENE English, underlying /r/ after low vowels is represented only by vowel lengthening, and in urban ENE, both [a] and [o] have become [ɑ] [C. K. Thomas, Phonetics of American English (New York, 1958), p. 217], resulting in such minimal pairs as cod [kɑd] and card [kɑ:d]. Ten productions of each of these two words (and a number of foil words involving other phonetic contrasts) were recorded in a neutral carrier sentence by each of ten phonetically naive urban-ENE speakers unaware of the purpose of the investigation. Spectrographic measurements revealed fairly consistent differences in the vocalic-segment durations of cod and card for most speakers. But no speaker could reliably identify his own intended productions (though identification of foils was perfect) and for only two speakers was there any evident correlation between identifications and vocalic-segment durations. Evidently a phonetic change is in progress, and our results suggest that during such a change, contrasts in production may persist after they have ceased to be perceptually relevant.
The relative nature of voice quality
Authors: Ladefoged Peter
Published: October 2005

What is phonemic in one language may be pathological in another. This is especially true with respect to voice quality. In English, phonation which is either too breathy (with a large turbulent component), or too creaky (with the arytenoids pressed too tightly together) is considered deviant. But in Bushman languages, both these phonation types contrast with each other and with regular voice. (These languages also have a fourth contrasting phonation type involving ventricular action, which would be considered very pathological in English.) All these phonation types will be demonstrated and, to a limited extent, quantified. It will be shown that some speakers (notably the elderly) have a more breathy voice as their norm, and make their contrasting breathy voice sounds with an even larger turbulent component.
Relationship between vowel articulation and pitch control
Authors: Honda Kiyoshi , Baer Thomas , Hirose Hajime , Sawashima Masayuki
Published: October 2005

Extrinsic muscles of the tongue and larynx influence laryngeal function through their effects on the hyoid-larynx complex, and thus cause interaction between vowel articulation and fundamental frequency. It has been argued that the mechanism for pitch control by the extrinsic frame of the larynx is related to vertical movement of the larynx, although physiological data has not always supported this view. In this study, positional control of the hyoid bone was examined by monitoring electromyographic activity from suprahyoid muscles and displacements of the hyoid bone. A speaker produced Japanese two-mora words /ia/ and /at/ with different accent types. The data showed that activity of at least one anterior suprahyoid muscle, the geniohyoid, actively participated in pitch raising by producing anterior movements of the hyoid bone. This result suggests that horizontal rather than vertical movements of the hyoid bone caused by contractions of anterior suprahyoid muscles are used to tilt the thyroid cartilage forward and increase the longitudinal tension of the vocal folds. [Work supported by NINCDS.]
A limiting form for the nearfield of the baffled piston
Authors: New Ronald
Published: October 2005

The circular piston on the planar, infinite, rigid baffle and the pulsating sphere are fundamental (if not classic) problems in acoustic radiation theory. Those who work in the area of radiation and scattering are very familiar with the solutions to these two problems. The solution to a somewhat more difficult problem—the radially vibrating polar cap on an otherwise rigid sphere—is also available and is well documented. Although mathematically difficult to prove, the polar cap problem (or more precisely its general solution) reduces to that of the pulsating sphere in one limiting form, and to that of the piston on the baffle in another. This notion—that the solution to the polar cap problem subsumes the solutions to the two classic radiation problems of linear acoustics—is instructive and useful, if not profound. Its significance is in the use of the general solution of the polar cap problem to generate a convergent infinite series solution for the nearfield of the piston on the baffle. Extension computations have been performed in limiting cases to demonstrate this convergence.
Rayleigh and Lamb wave resonances in a viscous elastic plate
Authors: Fiorito Ralph , Madigosky Walter , Uberall Herbert
Published: October 2005

In a previous publication [J. Acoust. Sec. Am. 66, 1857 (1979)] we have analyzed the acoustic transmission (T) and reflection coefficient (R) of an elastic plate imbedded in a fluid in terms of a series of resonances. The distribution and the widths of the resonances have been shown to provide a determination of the geometrical and the material parameters of the plate, hence to solve the inverse reflection problem. In the present study, we extend our analysis to include the effects of viscosity (loss) in the plate. The Rayleigh and Lamb wave resonances are seen to experience a broadening and a frequency dependence of their widths as a consequence of the plate viscosity, and it is demonstrated that these effects may be used to determine the loss factor of the plate. [H. Überall is also at Catholic University, Washington, DC 20064, supported by ONR Code 421.]
Isolation of geometric response in experimental measurements of scattering from finite elastic bodies
Authors: Numrich S. K. , Frank L. J. , Dragonette L. R. , Flax L.
Published: October 2005

Acoustic scattering measurements are performed with fine frequency resolution to permit the observation of elastic effects which occur at discrete frequencies. For a body of known shape various physical properties of the material such as sound speed or density can be delineated from its elastic behavior. The elastic or resonance behavior dominates in the high ka region (where k is the acoustic wave parameter and a is the characteristic dimension of the body), and target classification is greatly complicated when the shape of the body is in question. Experimental and analytical scattering work done on finite elastic bodies has shown that information about the shape of a body can be obtained even in the resonance frequency region. When scattering results are averaged over a broadband of frequencies, the form function obtained resembles that of a rigid body of the same shape. Analytic computations for rigid bodies can be compared with the averaged results and an approximate determination of shape can be made. In this way, both elastic and rigid body scattering results can contribute to the identification of the scattering object.
A network model of cochlear dynamics
Authors: Kletsky E. J. , Zwislocki J. J.
Published: October 2005

The mechanical dynamics of the cochlear duct are modeled as a linear electrical transmission line with parameters that vary with distance. The continuous line is approximated by a cascade of from 96 to 960 lumped sections, each representing an incremental length along the cochlea. Parameter values are based on anatomical and physiological measurements or on reasonable assumptions where direct data are lacking. The resulting lumped electrical network is solved for quantities representing basilar membrane displacement, tectorial membrane displacement, and shear between the reticular lamina and tectorial membrane for a set of 55 selected frequencies. Computations are carried out in FORTRAN using a “backward calculation” algorithm. The result is a set of data representing the magnitude and phase of displacement and shear at all points along the cochlea. The tuning characteristics for basilar membrane displacement and for shear (assumed proportional to neural tuning) are determined by making a cut through the set of fixed frequency data at the desired cochlear location. Nonlinearities in tuning as a function of intensity are accounted for by interpolation between sets of data generated for different values of the parameter representing hair-cell impedance. [Work supported by NIH.]
Effects of crossed olivocochlear bundle stimulation on the intracellular dc receptor potential from cochlear inner hair cells
Authors: Brown M. Christian , Nuttall Alfred L. , Masta Robert I.
Published: October 2005

The efferent crossed olivocochlear bundle (COCB) was electrically stimulated during recordings of acoustically evoked potentials from the guinea pig cochlea. Round window recordings of the click-evoked whole nerve action potential were decreased during COCB stimulation by the equivalent of 10–20 dB SPL. Recovery was complete about 400 ms after the stimulation ended. COCB stimulation increased by 0–3 equivalent dB the round window cochlear microphonics in response to a 1-kHz continuous tone, similar to earlier investigations [T. Konishi and J. Z. Slepian, J. Acoust. Soc. Am. 49, 1762–1769 (1971)]. The inner hair cell intracellular dc receptor potential, in response to tone bursts near the characteristic frequency, was decreased during COCB stimulation and recovered during a time period similar to that followed by the whole nerve-action potential. The reductions ranged from 3–14 equivalent dB and were greatest for lower SPLs. The resting membrane potential was unchanged. Since the COCB is thought to primarily innervate the outer hair cells, these results may be a conclusive demonstration of hair cell interaction. [Supported by NIH Grants NS-05785, NS-15107, NS-07106.]
High-intensity “notches” in responses of auditory nerve fibers
Authors: McGee J. , Farley G. R. , Walsh E. J. , Javel E.
Published: October 2005

In cat auditory nerve fibers, pure-tone input-output functions for both discharge rate and synchronization can be nonmonotonic. That is, there can exist an intensity range over which the response saturates, then declines, then increases again at higher intensities. In our experiments, this intensity “notch” usually began at 70–100 dB SPL and persisted for the next 10–50 dB, with 30 dB being a typical range. The upper leg of the rate-intensity function had a steeper slope and saturated at a higher rate than the lower leg. The depth of the “notch” could vary from only a slight inflection in response to a depression down to spontaneous level. We have observed “notches” in all regions of fibers' response areas. The intensity range and magnitude of the “notch” varied both within and across fibers. “Notches” at low stimulus frequencies were usually accompanied by rapid shifts in mean discharge phase angle. The cumulative phase shift was not consistent, ranging from less than 90° to more than 200°. Reversals in the direction of phase change were common. “Notches” for tones below 600 Hz often displayed bimodal period histograms, but the two peaks usually existed only over a narrow range of intensities. [Work supported by NIH.]
Experiments on the origin of two-tone suppression
Authors: Javel E.
Published: October 2005

Two-tone suppression has been shown to exist in virtually every response of cochlear origin. For comparable stimulus conditions, however, suppression magnitude measured in responses of hair cells and auditory nerve fibers is considerably greater than suppression magnitude measured in basilar membrane displacement patterns, and tho mechanical suppression threshold appears to be higher than the auditory nerve-fiber suppression threshold. We recorded responses of single auditory nerve fibers in anesthetized cats and used discharge synchronization as an index of suppression magnitude. It was found that (a) when “notches” in input-output rate functions exist, suppressed responses cannot be made to occur to the right of the upper leg of the unsuppressed function; (b) unlike results obtained for cochlear microphonics, the discharge phase angle of a suppressed response in auditory nerve fibers is the same as the angle of the pure-tone response at the same intensity; and (c) for low-frequency suppressors, the rate of growth of suppression with increasing suppressor-tone intensity can easily exceed the presumed rate of growth of basilar membrane displacement. A possible explanation is that there are two generators for suppression. One generator operates at high intensities and originates in basilar membrane mechanics. The other generator operates at all suprathreshold intensities and originates either in the micromechanics of the subtectorial space or in the mechanical-to-neural transduction process occurring inside hair cells. [Work supported by NIH.]
Neural tuning thresholds in the presence of a second subthreshold tone
Authors: Allen J. B.
Published: October 2005

The standard tuning paradigm used by Kiang and Moxon was modified to simultaneously present a continuous second frequency tone of level Ag and frequency fs. Results will be presented showing the effects of the tuning curve for various (Ag, fs,) combinations. In all cases (Ag, fs) was chosen to be below each units excitation threshold. Two major effects were observed. First, when fs < fCF, strong two-tone rate suppression effects were observed at fCF with CF thresholds being elevated by up to 40 dB as a result of the sub-threshold suppression tone. Second, when fs > fCF, for certain values of Ag and fs, strong cochlear distortion components were seen, causing dramatic threshold reductions above CF. While both of these effects seem to be consistent with previous measurements of two-tone suppression and combination tone distortion components, the methods described here appear to be a much improved way of quantifying these effects. Work was done in collaboration with Columbia University.
Coding of some consonantal features in the auditory nerve
Authors: Delgutte B.
Published: October 2005

Responses of auditory-nerve fibers to computer-generated stimuli having consonant-like changes in amplitude and spectral characteristics were obtained for two different sound levels. Experiment I concerned the distinction between two noice bursts differing in the abruptness of their onset: a/č/ stimulus with a 10-ms rise time, and a /š/ stimulus with a 75-ms rise time. Response patterns of auditory-nerve fibers over a wide range of characteristic frequencies (CF) showed a more prominent peak at the onset of the stimulus for /č/ than for /š/. In experiment II the stimuli consisted of /da/-like formant trajectories preceded a context that was varied to produce stimuli sounding like /da/, /ada/, /na/, /ša/, and /sa/. After the low-frequency context in /na/, the response of low-CF fibers during the formant transitions was lower than after a silent context as in /da/ or /ada/, whereas after a high-frequency context as in /ša/ or /sa/ the response of high-CF fibers was lower. This dependence of response on context, which was found both for mean discharge rate and for response measures involving fine time patterns of discharge, emphasizes “new” frequency components in the representation of spectrum. [Supported by NIH.]
Velar activity during speech: An electromyographic study
Authors: Dixit R. Prakash
Published: October 2005

Levator palatini activity and voice were simultaneously recorded while a native speaker of Hindi produced monosyllabic, bisyllabic and polysyllabic meaningful and non-meaningful words in the frame/kya-ap dȝante hæ̃/. High and low vowels and voiced and voiceless stops occurred in various positions in these words. Although there was considerable overlap in levator activity for different segment types, the stops were produced with greater activity than the vowels. In stops, the voiceless stops showed greater activity than voiced stops, whereas in vowels, the high vowels revealed greater activity than the low vowels. Furthermore, levator activity for the stops following high vowels was in general greater than for those following low vowels; it was greatest following nasals. These results will be discussed in relation to the results of other studies of levator palatine activity.
Phase relationships among articulator muscles as a function of speaking rate and syllable stress
Authors: Tuller Betty , Harris Katherine S. , Kelso J. A. Scott
Published: October 2005

The present experiment—continuous with our earlier work— examined the temporal relationships among muscle activities as a function of suprasegmental variations in stress and speaking rate. In all, five muscles known to be associated with lip, tongue, and jaw movements were sampled. Large variations in magnitude and duration of activity in individual muscles were observed. However, analysis of the phase relationships among muscles suggested that the timing of consonant-related activity remained fixed relative to activity for the flanking vowels. This style of control in which the relative, rather than absolute timing of activity among muscles is preserved across metrical changes is a characteristic of many non-speech motor activities and may rationalize certain findings in speech production and perception. [Work supported by NINCDS and BRSG.]
Low-frequency sound absorption in sea water: A new chemical relaxation mechanism?
Authors: Mellen R. H. , Browning D. G. , Simmons V. P.
Published: October 2005

Excess sound absorption in sea water arises mainly from chemical relaxations involving MgSO4 and B(OH)3. The high-frequency (100 kHz) MgSO4 relaxation has been identified as a multistep ion-pair process. The low-frequency (1kHz) and B(OH)3 relaxation apparently involves more complex interactions with other constituents. To investigate B(OH)3 interactions in a simpler system, we measured absorption in NH3 solution using the resonator method. We have found αmax to be proportional to the product of NH4+ and B(OH)4− concentrations; however, the magnitude is much too large to be caused by the ion pair. The mechanism, probably similar to that in sea water, resembles catalysis, the absorption being governed by the large volume change of the faster NH3/NH4+ equilibrium and the relaxation frequency by the slower B(OH)3/B(OH)4− equilibrium. [Work supported by NUSC and DARPA.]
The struggle against noise in French dwellings
Authors: Josse R.
Published: October 2005

For several years a considerable effort has been made in France to ensure good sound isolation between new dwellings, as well as against the intrusion of outdoor noises. The effort has been carried out in the following areas: regulations, labeling, controls and sanctions, scientific and technical research, and the publication of examples of solutions. The different aspects of this effort against noise will be examined in detail.
Environmental Protection Agency's Model Building Code Noise Control Provisions and Economic Impact Study
Authors: Caccavari C. , Pesce F. J. , Rudder F. F. , Weber S. W.
Published: October 2005

The U.S. E.P.A. Office of Noise Abatement and Control has developed an eight step approach to abate noise in multi-family and educational buildings. The core of this program is the adoption and implementation of the E P.A.'s Model Noise Control Provisions which can be adopted by state and local jurisdictions and inserted into their existing building codes. The Model Provisions contain recommended noise standards that the E.P.A. feels are practical and sufficient to reduce noise in an average community. A supporting study to the E.P.A.'s Building Code Program is an Economic Impact Study. This study presents a technique for evaluating the acoustical insulation costs defrayed by energy savings. The Cost Minimization Model developed by the National Bureau of Standards for the E.P.A. is also presented. In addition, the N.B.S. is undertaking a Benefit Study for the E.P.A. designed to estimate both acoustical benefits to be derived from implementation of the E.P.A.s Model Building Code Noise Control Provisions by local officials and the number of people in their community who will receive these benefits.
A theoretical approach to sound propagation and radiation for ducts with suppressors
Authors: Rice Edward J. , Sawdy David T.
Published: October 2005

The several phenomena involved in theoretical prediction of the farfield sound radiation attenuation from an acoustically lined duct have been studied. These include absorption by the suppressor, termination reflections, and farfield radiation. Extensive parametric studies have shown that the suppressor absorption performance can be correlated with mode cut-off ratio or angle of propagation. The other phenomena can be shown explicitly to be dependent upon mode cut-off ratio. A complete system can thus be generated which can be used to evaluate aircraft sound suppressors and which can be related to the sound source through the cut-off ratio-acoustic power distribution. Although the method is most fully developed for inlet suppressors, several aft radiated noise phenomena will also be discussed. This paper summarizes this simplified suppressor design and evaluation method. Comparisons of noise suppressor data from engine experiments are compared to the theoretical calculations for farfield sound attenuation directivity.
Aircraft absorbers—Promise and practice
Authors: Andersson A. O.
Published: October 2005

Sound absorbers have been applied in earnest to aircraft engine ducts since the 1960's. Designs have concentrated on locally reacting wall linings with exceptions motivated by physical constraints rather than a desire for more efficient absorbers. Emphasis has been on obtaining greater frequency bandwidth of attenuation through the use of lining configurations more complicated than the single-layer honeycomb absorber. Duct linings work in a significantly different manner than wall absorbers in rooms, however, in that one purpose of the lining is to create favorable pressure gradients in the field away from the duct surface. The implications are that different wavenumber components of the sound field require different boundary conditions for maximal absorption. The development of linings with great wavenumber bandwidth has received little attention. Analysis techniques need to be developed for such linings, which are necessarily nonuniform or of extended reaction. The number of design variables may then be so great that parametric testing for design optimization will be impractical. This also leads to a requirement for experimental determination of the structure of the sound field to be attenuated and new techniques for testing of lining components and systems to capitalize on the great potential in improvement of absorber technology.
Ultrasonic absorption in deer blood
Authors: Shung K. K. , Rocco M.
Published: October 2005

The erythrocyte sickling in white-tailed deer is very similar to that in humans. Deer hemoglobin molecules polymerize at high pH and high oxygen tension. Ultrasonic absorption in deer blood versus pH and oxygen tension has been measured with Carstensen's fix path method and a method described in an earlier paper [K. K. Shung et al., Blood 54, 451–458 (1979)]. It has been found that the ultrasonic specific absorption at 15 MHz increases from 27 dB-cc/ g-cm to 66 dB-cc/g-cm when the pH of the blood is increased from 7 to 8 at an oxygen saturation of 95%. This result compares favorably with the data for humans which show that, under physiological conditions favoring sickling, the specific absorption at 15 MHz is around 60 dB-cc/g-cm. It was also found that ultrasonic absorption starts to increase at oxygen saturation around 50% at high pH and does not change appreciably at physiological pH. [Work supported by NSF grant DAR-8018415 and NIH grant HL26871.]
Ultrasonic measurement of threshold temperature for irreversible cutaneous burns
Authors: Cantrell John H. , Goans Ronald E.
Published: October 2005

Knowledge of the “in vivo” threshold temperature for thermally induced dermal necrosis is important to the understanding and assessment of the total burn injury. The recently developed ultrasonic pulse-echo system for assessing thermal injury [R. E. Goans, J. H. Cantrell, Jr., and F. B. Myers, Med. Phys. 4, 259–263 (1977); J. H. Cantrell, Jr., R. E. Goans, and R. L. Roswell, J. Acoust. Soc. Am. 64, 731–735 (1978)] was used to obtain quantitative “in vivo” measurements of the depth of cutaneous burns experimentally induced in anesthetized Yorkshire pigs. The burn depth as a function of burn time and surface temperature of the porcine skin was measured. The data were used in the solution of the one-dimensional heat diffusion equation with appropriate boundary conditions to obtain the temperature at which irreversible thermal damage to the skin tissue occurs. Our calculated threshold temperature of 68° is within the range of values (60°C–72°C) previously reported using nonacoustic techniques. The implication of the present measurement to the quantitative assessment of the accumulated damage rate process is discussed.
Impedance modeling of acoustic absorbing materials for aircraft engine applications
Authors: Dean Lee Wallace , Patrick William P.
Published: October 2005

A review of conditions under which impedance is a useful concept in solving the problem of wave propagation in a duct with flow is presented with illustrative examples. Organized procedures for modeling single and multiple degree of freedom configurations both of the lumped and distributed parameter type are discussed, and data and model predictions are compared for some specific configurations. Assumptions usually made in the modeling process are pointed out, and the effect of the assumptions, particularly on the comparisons with data, are evaluated. Improved impedance models, developed more recently, are reviewed and compared with previous models and with impedance tube data. Included in the discussion are models for bulk absorber materials compatible with aircraft-engine environments.
Theoretical approach to predicting sound attenuation in liquid flow ducts
Authors: Ko Sung H.
Published: October 2005

A theoretical model for predicting the sound attenuation in a liquid-filled duct lined with a viscoelastic material is discussed. The viscoelastic liner is a rubber-like material that has a loss factor associated with the shear modulus. In the analysis the liner is assumed to be in perfect contact with the rigid duct wall. The viscoelastic liner is characterized by Lamé constants and the material density. The fluid in the lined duct is assumed to be inviscid, and is characterized by the fluid density and the speed of sound in the medium. The derivation of the eigenvalue equation is based on the theory of elasticity, the acoustic wave equation in the presence of fluid flow, and standard boundary conditions. The eigenvalue equation was solved numerically for a given duct geometry, the liner configuration, the liner material properties, and the fluid flow velocity. Then the sound attenuation was obtained by using the calculated eigenvalues. [Work supported by NUSC.]
Nonlinear phenomena in flow duct acoustics
Authors: Nayfeh Ali H.
Published: October 2005

A number of experiments have demonstrated that considerable reductions in the noise emitted by turbofan engines can be accomplished with the use of a choked or partially choked inlet. Using the wave-envelope technique to examine the linear acoustic equations in variable-area ducts carrying near sonic flows shows that they are invalid when the mean Mach number approaches unity because of the presence of a singularity in these equations. Numerical results show that the Mach numbers at which the two-dimensional equations become invalid are smaller than the Mach numbers at which the one-dimensional equations become invalid. The variation of the area tends to refract upstream propagated symmetric waves toward the centerline of a circular duct. This refraction intensifies considerably the centerline pressure. The intensification increases with increasing frequency and mean Mach number but decreases with increasing the real part of the wall admittance. A spectral method is used to analyze the nonlinear one-dimensional equations. The results in a converging-diverging duct carrying near sonic flows show that the nonlinearity produces higher harmonics and an acoustic-streaming component and results in the reduction of the amplitude of the emitted fundamental frequency. The reduction increases with increasing sound intensity and mean Mach number. Beyond critical conditions, an unsteady shock develops.
Acoustic pulse propagation in a convergent-divergent duct carrying a subsonic mean flow
Authors: Handler Robert A. , Taylor David W.
Published: October 2005

An acoustic pulse excitation technique was used to measure the transmission coefficient and reflection coefficient of a convergent-divergent duct carrying subsonic compressible flow. The duct consisted of a rapidly convergent nozzle section followed by a conical diffuser whose length and angle of divergence were varried. The throat Mach number was varied from zero to nearly one and the energy of the upstream incident pulse was principally in the 50–700 Hz range. The results indicate that for throat Mach numbers approaching one, the transmission coefficient decreased by as much as 10 dB below the zero Math number case. The decrease in the transmission coefficient was observed exclusively in a band of frequencies below the no-flow quarter wavelength frequency of the duct. A one-dimensional finite element transfer matrix calculation gave qualitative agreement with the principal observations. [Work supported by Donaldson Company, Minneapolis, MN, and has been submitted in partial fulfillment for the degree of Doctor of Philosophy at the University of Minnesota.]
Cochlear partition displacement patterns to frequency varying signals
Authors: Shore Susan E. , Cullen John K.
Published: October 2005

Cochlear microphonic recordings from 10 guinea pig cochleas were used to infer cochlear partition displacement patterns to frequency varying signals. Rate-dependent differences between rising and falling sweeps were predicted on the basis of delay-line characteristics of the cochlear partition. The frequency responses of three basal turn locations were assessed using puretones of different frequencies. Tone sweeps with different frequency change rates (i.e., frequency endpoints were kept constant and duration was varied) were generated near the “best-frequencies” of these regions. Responses to sweeps obtained from each electrode location were summed and the time of occurrence of cochlear microphonic maxima and minima from each location was measured relative to the other locations. The results indicate that inferred cochlear partition displacements to falling frequency sweeps occur sequentially at different points along the partition. Corresponding rising-frequency sweeps cause displacements more closely spaced in time. Displacement pattern differences occurred only at high rates of change. At low rates, cochlear partition displacements for the rising sweep disperse in time, showing the sequential pattern obtained with falling sweeps. [Work supported by NIH.]
Indoor noise level limits for residential areas affected by transportation noise
Authors: Birnie Susan E. , Hall Fred L.
Published: October 2005

Noise criteria for buildings are often set on the basis of expected annoyance levels, which in turn may be seen as a function of activity interference, particularly speech or sleep disturbance. The relationships between various physical measures of noise, reported activity interference, annoyance due directly to the activity interference, and overall annoyance are as yet not clear. This paper describes a probabilistic model linking these variables, and presents a preliminary test of the model using a small data set. Houses exposed to road traffic noise and aircraft noise were chosen. At each house, detailed noise measurements were taken simultaneously outside and inside the house, using two real time one-third octave band analyzers. In addition, a member of the household was asked about activity interference around the house, and about overall annoyance. These data permit feasibility tests of the model, which will later be tested on a more extensive data set. If successful, the model will help to identify acoustical insulation requirements for different noise environments, as well as permitting identification of those aspects of outdoor noise which lead to indoor speech interference and annoyance. This in turn is essential information for setting indoor noise criteria.
Method for evaluating trends in airport noise impacts
Authors: Konheim Arnold G. , Bassett David A.
Published: October 2005

A method was developed for determining the area exposed to airport noise by J. Watson Noah, Inc. for the CAB. Based upon the relationship between the magnitude of a contour area and the number of aircraft operations at an airport, the method permits the rapid estimation of the area contained within the Ldn = 65-dB contour. This paper discusses the validity of applying this method to various size airports and its use in determining trends in noise impact at airports.
Enforcement of a quantitative noise ordinance
Authors: Manuel John , Krajewski Chris , Butko Leo , Fumerton David
Published: October 2005

Quantitative community noise ordinances are currently implemented in only a few municipal jurisdictions around the world. Comparative studies conducted by the Ontario Ministry of Environment show that significant differences exist in philosophy, law and measurement procedures between these jurisdictions, leading to varying interpretations of the allowable background (baseline) noise level for a given place and time of day. For legal purposes, the degree and quality of the offending noise excess above the allowable background (baseline) level must be determined quantitatively if this type of local community ordinance is to be enforced. Techniques for quantitative investigation of nuisance complaints due to common noise sources in the local community are discussed. Measurements, using some of the latest types of sound level measuring devices, are analyzed to suggest a rational solution to the problem.
Speaker independent isolated word recognition for a 129-word airline vocabulary
Authors: Wilpon J. G. , Rabiner L. R. , Bergh A.
Published: October 2005

Previous research at Bell Laboratories has been shown that a reliable act of speaker-independent word reference templates for a speech recognition system can be obtained from a population of talkers using sophisticated statistical clustering techniques. These studies have investigated a 39-word alpha-digit vocabulary and a 54-word vocabulary of computer terms. In this talk, automatic clustering procedures are used to create reference tokens for a 129-word vocabulary of airline reservation terms. To obtain the word reference templates, a two-stage training procedure was used. First each of 100 talkers (50 men, 50 women) used the robust training procedure of Rabiner and Wilpon to provide a single, reliable pattern for each vocabulary word. Second the set of automatic clustering procedures placed each word token into one of several word clusters and produced one reference pattern per cluster. A set of 20 new talkers were used to test the procedure. Several length normalization procedures were incorporated into the testing procedure. Recognition accuracies on the order of 90% were obtained for the 20 talkers. These results are comparable to ones obtained from a speaker-dependent study done previously on the same vocabulary.
Effect of reference set selection on speaker dependent speech recognition
Authors: Li Zongge , Alleva Fil , Reedy Raj
Published: October 2005

Presented here for a speaker dependent system, is an algorithm which chooses a reference template for each word in the vocabulary from a set of N exemplars. The goal of the algorithm is to produce a reference set that minimizes the worst matching behavior and total error over the N sets of exemplars. The results of the experiments presented here show a reduction in the average error rate from 16.4% to 10.2% over a set of 4 male speakers and 4 female speakers.
Directory listing retrieval using spoken connected letters and a level building DTW algorithm
Authors: Myers C. S. , Rabiner L. R.
Published: October 2005

At Bell Laboratories, a system for retrieving directory listings based on recognition of spoken spelled names (with isolated letter input) has been developed. The system can be used in either a speaker trained mode or in a speaker independent mode, and the overall name accuracy is quite high in either case. In this talk we discuss an extension of the system to the recognition of connected sequences of letters for the specification of the name. The recognition and search procedures had to be modified since no clear segmentation into individual letters was possible. The level-building DTW algorithm of Myers and Rabiner was used to provide letter distance scores, and a modified Aldefeld search procedure was used to find name candidates. Name recognition accuracies on the order of 95% were obtained in tests of the system with four talkers saying 50 names at two talking speeds for both speaker trained and speaker-independent modes.