bluuebunny/crossref_metadata_2025 huggingface dataset:
Alternative solutions to high-frequency structural acoustic problems
Authors: Feit David
Published: October 2005

The response of a number of structural acoustic systems is often available in terms of a modal expansion. The low-frequency response is then readily described by the first terms of the series. In the high-frequency limit these modal series are difficult if not impossible to interpret because of the many terms required for convergence. In this presentation we review the methods for obtaining alternative representations for the solutions. These new representations readily lend themselves to physical interpretation because of the very much smaller number of terms required for convergence. Two different problems will be used to illustrate the process. The first one is that of a force excited finite elastic beam undergoing flexural vibrations, while the other considers the same type of excitation applied to an infinite cylindrical shell.
The effects of slope-enhanced shipping noise on the ambient noise field vertical directionality
Authors: Wales Stephen C. , Heitmeyer Richard M.
Published: October 2005

Recent measurements of the ambient noise field vertical directionality have indicated that the noise level is concentrated within ± 20° of the horizontal. Within this region as many as three separate peaks have been observed. Two peaks near ± 15° have been attributed to distant deep ocean shipping, and a peak near the horizontal has been attributed to slope enhancement of ship noise along the continental shelf edge and in the vicinity of oceanic ridges and seamounts. In addition, ships in near-Arctic waters can also provide noise at shallow angles to receivers located in temperate waters as a result of range-dependent refraction. The effects of these mechanisms on the vertical directionality of the noise from shallow sources are considered using a PE propagation model which provides the vertical directionality at a receiving array. It is concluded that continental slope enhancement is a significant source of low-angle noise in many oceanic regions. Some effects of slope enhancement on the noise field horizontal directionality are also discussed.
The SACLANT ASW Research Centre shallow water ambient noise research program
Authors: Wagstaff Ronald A.
Published: October 2005

The SACLANT ASW Research Centre has been investigating acoustic propagation and the omni-directional level of ambient noise in shallow water for more than ten years. The Centre has recently extended this shallow water research program by commencing investigations of the depth dependence and direction of the shallow water ambient noise field. This new effort is in the form of theoretical studies, modeling, measurement, development of a new data acquisition and processing system, and the construction of new equipment. A brief description and some recent results will be given.
Vertical noise distributions in the ocean: Models and measurements
Authors: Williams Robert Bruce
Published: October 2005

A simple noise vertical distribution model is presented for deep ocean environments. The dependent parameters are receiver depth, depth excess, wind speed, and frequency. The vertical distance at which the spatial correlation equals zero depends on receiver depth, and is in the range of 1.5 to 2 wavelengths rather than the usual 0.5 for a uniform noise distribution. Incorporated in the model is the recent wind dependent results of Ross. Measurements taken from FLIP in the Pacific using a 500-m 20-element array are used to compute vertical distributions functions, beam statistics, and the vertical correlation function for selected frequencies. These results are then compared to the model predictions.
Effect of tone location within the noise spectrum on overall loudness, annoyance, and noiseness
Authors: Hellman Rhona , Ashkinaze Barbara
Published: October 2005

Recent evidence indicates that, when tones are centered within broadband noise, small tone-to-noise ratios (+5, +10, +15 dB) consistently increase overall perceived magnitude more than large tone-to-noise ratios (+20 dB and greater) [R. Hellman, J. Acoust. Soc. Am. Suppl. 1 69, S104 (1981)]. Further experiments were conducted using the method of absolute magnitude estimation (AME) to determine the effect of the high-frequency skirt of a low-pass noise on loudness, annoyance, and noisiness judgments. The noise, resembling typical aircraft spectra, was gradually attenuated by 5 dB/ octave above the cutoff frequency at 600 Hz. Results obtained with single tones at 1000, 2000, and 3000 Hz added to the noise skirt are compared to those obtained at 250 Hz. It is shown that when overall SPL is approximately constant, the relationship between perceived magnitude and tone-to-noise ratio depends on the location of the tone within the noise spectrum for loudness and annoyance, but not for noisiness. The obtained data are discussed in relation to the published results of other investigators. [Work supported by NASA-Langley Research Center.]
The effect of pavement roughness on near-field tire noise
Authors: Stusnick Eric , Plotkin Kenneth J.
Published: October 2005

As part of a program to quantify the noise generation mechanisms of heavy-duty truck tires, tire carcass accelerations and near-field sound levels were measured at various vehicle speeds on concrete and asphalt surfaces of different roughnesses as well as on an imbedded, smooth steel plate. The results of this experimental program are described and the effects of surface texture identified. The steel plate measurements are also compared with similar measurements taken using a curved, smooth steel roadwheel. The results of this study will be used to evaluate the realism of roadwheel noise measurements, and to extend to real pavement conditions a set of analytic noise models developed from smooth roadwheel data. Additional experiments on a roadwheel with simulated surface texture are planned. [Work supported by U.S. Environmental Protection Agency under Contract No. 68-01-6243.]
Radiation field of an immersed hollow cylinder driven by a point source
Authors: Flax Lawrence , Ku Chau-Chi , Allen Charles , Dragonette Louis R.
Published: October 2005

Theoretical and experimental studies are presented of the radiation field of an immersed hollow cylinder driven by a harmonic point force on its inner surface. The exact theory of elasticity and the approximate thin shell theory are used to analyze the behavior of the thin shell. Due to the differences in the basic assumptions which underlie these two theories, their dispersion curves show that they agree at low ka values only. Also, the approximate theory does not include the torsional vibrational mode. The analytic computations of the radiation field are performed to illustrate the difference in both the low and high ka values. The theoretical model was duplicated experimentally by using a mechanical point source excited by a piezoelectric material to drive a thin cylindrical shell of finite length (length ≪ radius) immersed in water. Measurements of the radiated field were taken at near and farfields at ka values between 1 and 5. These results are compared to both the exact and approximate theories.
The influence of signal spectrum on click elicited evoked responses
Authors: Owen Jeffrey , Champlin Craig , Laskowski Randy
Published: October 2005

Click elicited evoked responses have gained widespread clinical use as a measure of the neurological and audiological integrity of the auditory brain stem structures. Typically, the clicks are presented at various intensity levels and the elicited responses are compared interaurally as well as with established norms. This study was conducted to determine the influence of the spectrum of the transduced click on the latency and amplitude characteristics of the averaged response elicited at various intensity levels [Clicks (100-μs square waves) were presented monaurally at 50, 60, 70, and 80 dB nHL]. Spectral analysis of the transduced signals indicated that the frequency response characteristics of the earphones significantly influenced the bandwidth of the signal. Furthermore, one earphone introduced a significant amount of intermodulation distortion into the transduced signal. The influence of the transduced signal on the inter- and intrasubject characteristics of the evoked potential will be presented.
Some properties of an auditory evoked response with a latency range of 10–18 ms
Authors: Klein Alan J.
Published: October 2005

A slow-wave evoked response, possibly a late component of the brainstem response, can be used to estimate hearing sensitivity to low-frequency stimuli [T. Suzuki, et al., Scand. Audiol. 6, 51–56, (1977)]. On human subjects with normal hearing psychophysical pure tone and tone pip thresholds were compared with evoked response thresholds. Frequency specificity of the response was measured with a simultaneous-masking tuning curve paradigm. All tone pips (0.25, 0.50, 1.0, 2.0, 4.0 kHz) had a rise-fall time of 3.0 ms with no plateau and were presented at 40/s. Mean audibility curves for pure tones and tone pips were parallel. The tone pip curve was displaced above the pure tone one by 5–10 dB. The evoked response threshold curve paralleled the psychophysical curves but was displaced above the tone pip curve by 15–20 dB. Tuning curves to signals at 0.5, 1.0, 2.0, and 4.0 kHz suggest that this evoked response is frequency specific at least up to 60 dB sensation level. Tuning curves to signals at 250 Hz had tips in the 350–450 Hz region. In some subjects, evoked response threshold increased by as much as 20 dB during sleep. [Supported by NIEHS].
Examination effects on ac thresholds
Authors: Roche Alex F. , Mukherjee Debabrata , Chumlea W. Cameron
Published: October 2005

Serial ac pure-tone thresholds have been recorded serially at 6-month intervals in 261 normal children aged 6 to 18 years at their first examinations. Data from 1802 examinations have been analyzed by a regression model fitted to all the data, for each frequency in each ear, within sex after excluding examinations at which pathological changes were present. The regression of thresholds on examination order, after removing age effects, shows a significant linear effect but no significant quadratic effect. The examination effect does not differ significantly by sex or ear but varies significantly by frequency (p < 0.004) as shown by an analysis of variance with balanced design and adjustments for sex and ear effects. The examination effects are significantly greater at 4 and 6 kHz (about 0.7 dB/examination) than at 0.5, 1, and 2 kHz (about 0.4 dB/examination). The possibility of separating examination effects due to the influence of habituation, movivation, and changes in noise exposure will be discussed in addition to the relevance of the present findings to the assessment of intervention programs. [Work supported by Contract No. F33615-81-C-0516 from the USAF and EPA.]
Elastic waves in periodically stratified media with interfacial slip
Authors: Schoenberg Michael
Published: October 2005

A periodically stratified elastic media can be replaced by an equivalent homogeneous transverse isotropic medium in the long wavelength limit. The case of a homogeneous medium with equally spaced parallel interfaces along which there is imperfect bonding [M. Schoenberg, J. Acoust. Soc. Am. 68, 1516–1521 (1980)] is a special case of such a medium. Slowness surfaces are derived for all plane-wave modes through the equivalent medium and reflection coefficients for a half-space of such a medium are found. The slowness surface for the SH mode is an ellipsoid. The exact solution for waves in a medium with parallel slip interfaces is found using the matrix method for periodic media [K. Gilbert, J. Acoust. Soc. Am. Suppl. 1 66, S73 (1979)] applied to elastic waves. Explicit results are derived and in the long wavelength limit, shown to approach the results for waves in the equivalent homogeneous medium. Under certain conditions, a half-space of a medium with parallel slip interfaces has a reflection coefficient independent of the angle of incidence and thus acts like an acoustic reducing mirror.
Traveling-bubble cavitation noise
Authors: Hamilton Mark F. , Thompson Donald E. , Billet Michael L.
Published: October 2005

High-speed films were taken of traveling-bubble cavitation on a Schiebe nose while the accompanying noise signal was recorded. These results showed rebounds to generate almost as much noise as the initial collapse. By counting the number of noise bursts occurring for given noise level and flow parameters, it was found that the noise energy per bubble varies with the cavitation number as roughly σ−x above 10 kHz, but not at all with the free stream flow velocity V∞ between 30 and 40 fps. The spectral energy density was observed to be flat, regardless of σ and V∞, from 10 to 100 kHz. Although maximum bubble radii as functions of σ and V∞ were not adequately measured during this study, it is clear that an understanding of this parameter is critical to any cavitation noise theory. The results from this investigation suggest that one might use the linear noise theories for incompressible fluids when analyzing cavitation noise at sufficiently low frequencies. However, it appears that shock wave noise theories are more appropriate for describing the high-frequency noise energy. [Work supported by NAVSEA.]
Structural response of the SSME fuel feedline to unsteady shock oscillations
Authors: Larson E. W. , Ratekin G. H. , O'Connor G. M.
Published: October 2005

The Space Shuttle Main Engine (SSME) development program experienced two similar appearing fuel feedline failures during the shutdown portion of two engine tests. Due to the extensive damage that resulted, an in-depth investigation was carried out to determine the causes of the failures, as well as establish a design alternative to allow continuation of engine development. Experimental air flow tests using a subscale model were performed with high-frequency pressure instrumentation such that pressure oscillation amplitude, frequency, and spatial characteristics could be determined. The test results led to the conclusion that the SSME was experiencing pressure oscillations of 38 psi at a frequency of approximately 100 Hz occurring over the last 3 ft of the nozzle. These pressure pulses were then used as a forcing function to determine the response of the feedline nozzle assembly using a structural dynamic model. The results were compared with strain data taken from actual tests. Results of this investigation yielded an understanding of the cause of the failures and led to a redesign which exceeds life requirements.
Space Shuttle Model acoustic/overpressure test results
Authors: Jones J. H. , Guest S. H.
Published: October 2005

The SSV's engine-generated acoustics and ignition overpressure environments have been long considered as severe dynamic inputs to a reusable aero-frame structure with a payload located in close proximity to the propulsion systems. The definition of these environments and the noise suppression techniques that are required for SSV launch have been provided from a dynamically scaled hot propulsion model. The scale factor is 6.4% of the Shuttle with the vehicle launch facility with exhaust deflector and duct geometry being simulated. Water injection into the hot exhausts is also scaled for sound suppression for both on-pad and liftoff cases. The environments measured on model are then scaled to provide launch vehicle environments for vehicle, launch facility, and farfield areas. Overpressure environments from SRB ignition are also acquired from over 100 measurements on the vehicle and launch facility. Suppression techniques are being investigated for Western Test Range (WTR) launchers and for thrust augmented configurations of the Shuttle.
The training of rhythm for deaf children in a residential school using exaggerated stress patterns
Authors: Koike Kazunari J. M.
Published: October 2005

Nineteen prelingual deaf children, 8 to 12 years of age, who had poor ability to imitate normal stress patterns, were selected from a residential school which used sign language. These children were evaluated with the Modified Children's Auditory Test (MCAT) for categorizing and imitating monosyllabic, trochaic, and spondaic stress patterns. The test items were presented through headsets, and a vibrator attached at the child's wrist. There was no significant difference between the mean categorization score before and after training; however, the scores were high for both the pre- and post-tests. There was a significant improvement in the imitation scores from the pre-test to the post-test for each pattern. The acoustical analyses of the children's responses revealed: (1) the three acoustical parameters (i.e., amplitude, duration, and fundamental frequency) differed for correct and incorrect responses; (2) incorrect responses had some common characteristics (e.g., long duration of syllables, smaller contrast between syllables, and uncontrolled F0 contour); and (3) the change from incorrect to correct responses varied for some children.
A longitudinal study of the production of contrasts in voice-onset-time by English and Spanish learning children
Authors: Eilers Rebecca E. , Benito Carmen , Oller D. Kimbrough
Published: October 2005

Sixteen infants (half from English-speaking and half from Spanish-speaking communities) were recorded between 6 and 12 months and again at 2–212 years. All utterance initial stop consonants were sorted according to place of articulation. Voice-onset-time was measured using an oscilloscope with an average measurement error of 4 ms. The two year olds were recorded imitating 10 replications of short lag or long lag and lead category stops in a CV nonsense syllable at three places of articulation. Oscillographic measurements of VOT were made of each of these imitations. Results indicate that both groups of infants had similar distributions of VOT with modal values near 0. However considerable spread into both the long lag and lead regions was noted for both groups. By 212 years of age half of the children in each group had “acquired” their native contrast. Most children collapsed the non-native contrast and produced the foreign element at near 0 VOT consistent with the infant production mode. [Work supported by NIMH.]
Computer-steered microphone arrays for conference telephony
Authors: Flanagan J. L. , Shipley K. L. , Nelson J. R. , Johnston J. D. , Bottone P.
Published: October 2005

Two recent advances in acoustics technology open new possibilities for improving teleconferencing in large rooms. High-quality, inexpensive electret microphones can be used in sizeable numbers to form controllable arrays, or can be constructed as planar mosaics to which beam-forming computation can be applied. Ever-diminishing cost of digital computation, in the form of microcomputers, makes sophisticated per-channel processing feasible. We describe in this report the design of one-dimensional and two-dimensional microphone arrays, and their control for simple beam-forming by microprocessors. Computation essentially in real-time permits the beam to scan a given conference room space. Detection of speech at any given position can halt the scan and allow the beam to remain in that position until the signal subsides. We give calculated and measured responses for preliminary array designs, and circuit details for beam control by an MC68000 microprocessor. Extension of the technique to more sophisticated processing, such as matched filtering to achieve volume selectivity, is also discussed.
Flight test of a pure-tone acoustic source
Authors: Mueller Arnold W.
Published: October 2005

A unique experiment involving static and flight testing of a pure-tone acoustic source has been conducted. The objectives of the experiment were: to determine if a 4-kHz tone radiated by the source in flight and mixed with broadband aircraft flyover noise, could be measured on the ground with a high degree of statistical confidence; to determine how well a flight-to-static tone radiation pattern comparison could be made to the static radiation pattern; and to determine if there were any installation effects on the radiation pattern due to the flight vehicle. Narrow-band acoustic data were measured and averaged over eight microphones to obtain a high statistical confidence. The flight data were adjusted to an equivalent static condition by applying corrections for retarded time, spherical spreading, atmospheric absorption, ground impedance, instrumentation constraints, convective amplification, and the Doppler shift. The flight-to-static results are in excellent agreement with the measured static data. No installation effects were observed on the radiation pattern.
Interior and exterior resonances in acoustic scattering by arbitrarily shaped targets
Authors: Überall H. , Gaunaurd G. , Tanglis E.
Published: October 2005

The T matrix approach useful to describe classical scattering of acoustic (and other) waves from arbitrarily shaped objects, is here “married” to the resonance scattering theory in order to isolate the (complex) resonance frequencies and widths of fluid-loaded targets of arbitrary geometries. For the case of near-impenetrable (i.e., quasirigid/soft) targets, we split the partial-wave scattering amplitudes into terms corresponding to internal resonances of the elastic object which are caused by creeping waves revolving inside it, plus an apparently nonresonant background amplitude. This background, however, further contains the broad “resonances” caused by external, diffracted (or Franz-type, creeping) waves, together with a geometrically reflected contribution which can be extracted by a saddle point integration. The separation of resonant and background terms is done analytically based on the T matrix method for elastic scatterers of arbitrary geometry. [H. Überall is also at the Physics Department, Catholic University of America; additionally supported by ONR, Code 421.]
Detection of pure tones in quiet and in noise by infants and adults
Authors: Nozza Robert J.
Published: October 2005

Detection thresholds in quiet and in noise were estimated for infants (6 months and 12 months) using the visually reinforced headturn procedure. Test stimuli were 1000- and 4000-Hz pure tones, presented monaurally (TDH-49). In the masking condition, white noise was continually present at the earphone at 63.5 dB SPL (No = 25.5 dB). An adaptive threshold estimation procedure with a 5-dB step size was used. An adult group was run using the same protocol as used for the infant groups. Adult data agree with existing detection estimates. Detection thresholds improve with age in each condition of this experiment. The difference between infant groups is consistent at each frequency in quiet and noise. In quiet, the infants were relatively more sensitive at 4000 Hz while adults were relatively more sensitive at 1000 Hz. In noise, detection thresholds vary with frequency in the same way for all groups. Inferred bandwidths (Sm/No) are much larger for infants than adults. Age-related differences in task performance suggest that nonsensory factors may influence these data.
On the existence and evanescence of FM channels
Authors: Cole Dorothy , Moody David B. , Stebbins William C.
Published: October 2005

Selective adaptation paradigms provide the basic psychophysical evidence for the existence of human auditory channels selectively organized to detect frequency-modulated (FM) signals [e.g., R. H. Kay and D. R. Matthews, J. Physiol. 225, 656–677 (1972); R. B. Gardner and J.P. Wilson, J. Acoust. Soc. Am. 66, 704–709 (1979)]. Adaptation refers to a selective decrease in sensitivity for specific stimuli, following exposure to similar stimuli. Here we report a progressive decrease in adaptation effects following repeated daily experimental sessions in the detection task. Thresholds for discrimination of linear FM upsweeps from pure tones were determined for four human subjects. Adapting intervals contained either FM upsweeps or were silent. Initially all subjects showed an increase in FM detection thresholds following exposure to FM upsweeps—that is, FM thresholds obtained after exposure to FM upsweeps were 2–3 times greater than those obtained after silence. After approximately 20 sessions, thresholds determined after FM upsweeps had decreased to the point where the adaptation effect was no longer significant. The effect could not be reversed by increasing the duration of the adapting stimulus interval or the rate of modulation of the adapting stimuli. These findings raise questions regarding the basic assumptions underlying selective adaptation paradigms. It may be necessary to consider other explanations for the adaptation effect. [Supported by Research Grant BNS-77 19254 from NSF.]
Some frequencies of underwater noise produced by fishing boats affecting albacore catch
Authors: Erickson Gary J.
Published: October 2005

Acoustic energy introduced by fishing vessels into the water has been measured and analyzed. Catch records have been obtained for those boats whose acoustic characteristics are known. Averaging procedures were applied to catch records to obtain a meaningful average catch rate. This average catch rate is correlated with the spectrum of sound introduced into the water by the boat. A negative correlation between catch rate and frequencies above 1500 Hz has been established. Spectral peaks above 1500 Hz are attributed to propeller shaft bearings.
Comment on ’’Weak shock solution for underwater explosion shock waves’’ [J. Acoust. Soc. Am. 62, 1412–1419 (1977)]
Authors: Persson B.
Published: October 2005

It is pointed out that the results derived by Rogers can be obtained more simply using the 1956 calculations of G. B. Whitham [J. Fluid Mech. 1, 290 (1956)]. (AIP)
A theoretical study of the effects of various laryngeal configurations on the acoustics of phonation
Authors: Titze Ingo R. , Talkin David T.
Published: October 2005

Simulation of glottal volume flow and vocal fold tissue movement was accomplished by numerical solution of a time-dependent boundary value problem, in which nonuniform, orthotropic, linear, incompressible vocal fold tissue media were surrounded by irregularly shaped boundaries, which were either fixed or subject to aerodynamic stresses. Spatial nonuniformity of the tissues was of the layered type, including a mucosal layer, a ligamental layer, and muscular layers. Orthotropy was required to stabilized the vocal folds longitudinally and to accomodate large variations in muscular stress. Incompressibility and vertical motions at the golttis played an important role in producing and sustaining phonation. A nominal configuration for male fundamental speaking pitches was selected, and the regulation of fundamental frequency, intensity, average volume flow, and vocal efficiency was investigated in terms of variations around this nominal configuration. Parameters which were varied consisted of geometrical factors such as length, thickness, and depth, factors for shaping the glottis, as well as tissue elasticities, tissue viscosities, and subglottal pressure. Since nonlinear stress–strain properties were not included, subglottal pressure did not produce a pronounced effect upon fundamental frequency under these somewhat idealized conditions. F0 rasing correlated strongly with increased tension in the ligament, and somewhat with increasing tension in the vocalis. F0 lowering correlated with increase in vocal fold length when the tensions were held constant, but not with increase in vocal fold thickness. Vocal intensity and efficiency are shown to have local maxima as the configurational parameters are varied one at a time. It appears that oral acoustic power output and vocal efficiency can be maximized by proper adjustments of longitudinal tension of nonmuscular (mucosal and ligamental) tissue layers in relation to muscular layers. Quantitative verification of the ’’body-cover’’ theory is therefore suggested, and several further implications with regard to control of the human larynx are considered.
Individual differences in the perception of dichotic chords
Authors: Efron R. , Yund E. W. , Divenyi P. L.
Published: October 2005

A new method was employed to measure the changes in the strength of ear dominance in the perception of dichotic chords as a function of stimulus intensity. The results of the first experiment, where the right and left tones were of equal intensity, revealed striking individual differences in the way the ear dominance of five subjects changed as the intensity of the chords was varied over a 60–dB range—no two subjects exhibiting the same pattern of behavior. Since, within the context of the model of Yund and Efron [J. Acoust. Soc. Am. 62, 607–617 (1977)] these individual differences could result from right–left asymmetries in the subject’s intensity-response (I-R) transduction mechanisms, a second experiment was performed in which the two tones had different intensities. From the results of the second experiment the shape of the I-R function for each ear could be computed. Using these I-R functions as parameters, the model accurately predicted the idiosyncratic changes of ear dominance observed in the first experiment. The right-left asymmetries in the I-R functions also account for previously reported idiosyncratic changes in ear dominance as a function of the frequency difference between the two tones of the dichotic chord.
Sound production by workers facing the queen in V
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Authors: Ishay Jacob S. , Hochberg Yosef
Published: October 2005

In nests of Vespa orientalis, sounds are produced both by the larvae (hunger signal) and the adults. Adult workers mainly produce solid borne sounds by tapping the abdomen tip against the rim of the comb. Among these distinct series of tapping sounds is that produced by one or several workers facing the queen as she rests between oviposition sessions. Statistical analysis of 25 series of such taps shows that consecutive taps in a given series tend to be associated in one of the following combinations: (a) much frequency autoassociation, and little amplitude autoassociation; (b) much amplitude autoassociation. It seems that in (a), the tapping is executed in a manner resembling radio frequency modulation (FM), while in (b) it resembles radio amplitude modulation (AM).
Comments on Book Review of H
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t [J. Acoust. Soc. Am. 65, 554–555 (1979)]
Authors: May Daryl N.
Published: October 2005

The review of Handbook of Noise Assessment contains factual errors here corrected.
Temporary threshold shift from transportation noise
Authors: Kabuto Michinori , Suzuki Shosuke
Published: October 2005

Temporary threshold shifts (TTS), induced by recordings of aircraft noise, road traffic noise, and interior railroad car noise, were examined to estimate the auditory effects of these typical environmental noises. The aircraft noise used was of a Boeing 747 landing, recorded adjacent to the end of a runway. Six hours of binaural exposure to the noise, presented every 2 min at a maximum A-weighted level of 97 dB (slow response), developed a TTS2 at 4 kHz of 1.0±2.7 (SD) dB as the mean value for the 57 better ears of 19 subjects on three successive days. The road traffic noise was recorded on a road where traffic volume was 49.5 (26.8 heavy) vehicles per min, and the interior railroad car noise was in a car commonly utilized for commuting. These two noises, reproduced with duty cycles of 4 min 7 s and 3 min 4 s, respectively, induced, after 6 h of exposure, a TTS0.5 at 1.5 kHz and a TTS2 at 4 kHz of almost the same degree at each sound level (A weighted) of 75, 85, and 90 dB, in L50. The TTS0.5 were 0.5, 2 and 3 dB, and the TTS2 were −0.5, 3.5, and 5.5 dB, on the average, for the better ears of three to four persons, which indicates especially that 75 dB for the road traffic noise and 70 dB for the interior railroad car noise are the maximum sound levels which may fail to develop significant TTS even at 4 kHz. The present results lead to the conclusion that affected populations may have TTS induced by road traffic noise but that little effect is likely due to aircraft noise or interior railroad car noise.
Vibrations of a plate with an elastic constraint of eccentric circular part
Authors: Nagaya Kosuke
Published: October 2005

In this paper, a method for solving vibration problems of a viscoelastic plate having an eccentric circular constraint is presented. The frequency equation in a complex form for the plate with arbitrary shape is obtained. Numerical calculations are carried out for two cases of a circular plate with an eccentric circular stepped surface and a circular plate on an eccentric elastic foundation. The nondimensional natural frequencies and the logarithmic decrements are given for these plates.
Tone-segregation by phase: On the phase sensitivity of the single ear
Authors: Kubovy Michael , Jordan Ray
Published: October 2005

A monaural complex tone is synthesized from 12 harmonically related pure tones, played in phase. In each of 12 segments, one of the tones (the target) is played out of phase so that the sequence of targets is increasing or decreasing in frequency. If the target is at least 30° out of phase, the targets are perceptually segregated. This tone-segregation by phase raises doubts concerning several current theories of pitch perception. The phenomenon is conjectured to be caused by the ear’s nonlinear compressive transfer characteristic or by a temporal analysis of the stimulus.
Partial masking in the monkey: Effect of masker bandwidth and masker band spacing
Authors: Moody David B.
Published: October 2005

By means of a behavioral procedure in which equal response latency to tone onset was used to derive loudness matches, differential effects of masker spectral composition on loudness growth were determined using Old World monkeys as subjects. The maskers ranged from wide-band noise to pure tones and included noise bands separated on the frequency continuum by notches. In two of the determinations in which masker bandwidth was varied, there was a clear suggestion that loudness increased more rapidly as masker bandwidth decreased. In the remaining three determinations, there was no evidence of a bandwidth effect. In five of six determinations, in which the separation between masking bands was a parameter, loudness increased somewhat more rapidly in the presence of a wide-separation masker. These results suggest that, although spread of excitation in the cochlea may contribute to the growth of loudness, its role may be less significant than has generally been assumed. Data are also presented which relate the rate at which masked tones increase in loudness to the amount of the threshold shift.
Children’s understanding of monosyllabic nouns in quiet and in noise
Authors: Elliott Lois L. , Connors Suzanne , Kille Elaine , Levin Susan , Ball Karlene , Katz Debra
Published: October 2005

A four-alternative, forced choice adaptive procedure was used to measure the lowest intensity at which children could identify monosyllabic nouns that had been standardized to be understandable (at comfortable listening levels) to inner city, 3-year-old children. Results showed no age-related performance changes when the words were presented against a 12-talker babble or against filtered noise. In quiet, however, performance improved between the ages of 5 and 10 years. Performance of children with learning problems was poorer than performance of children achieving normal school progress, even though clinical measures of auditory sensitivity showed no differences. Results are discussed in terms of ’’semantic closure’’ skills of children.
Invertibility of a room impulse response
Authors: Neely Stephen T. , Allen J. B.
Published: October 2005

When a conversation takes place inside a room, the acoustic speech signal is distorted by wall reflections. The room’s effect on this signal can be characterized by a room impulse response. If the impulse response happens to be minimum phase, it can easily be inverted. Synthetic room impulse responses were generated using a point image method to solve for wall reflections. A Nyquist plot was used to determine whether a given impulse response was minimum phase. Certain synthetic room impulse responses were found to be minimum phase when the initial delay was removed. A minimum phase inverse filter was successfully used to remove the effect of a room impulse response on a speech signal.
Thickness-shear vibrations of a beveled AT-cut quartz plate
Authors: Sinha Bikash K. , Stevens Daniel S.
Published: October 2005

Thickness-shear vibration modes of a beveled AT-cut quartz plate have been analyzed from an equivalent three-dimensional equation of motion. This equation has recently been applied in the analysis of plano-convex contoured quartz crystal resonators by Tiersten and Smythe, and has been derived from the dispersion relation obtained in the course of an investigation on overtone modes of coupled thickness–shear and thickness–twist vibrations of trapped energy resonators with rectangular electrodes. Calculations based on the analysis have been shown to have excellent agreement with experimental results. The analysis accounts for the anisotropy, piezoelectricity, and mass loading effects due to the electrodes. The solution for a beveled quartz strip is expressed in terms of Bessel functions of the order ±1/3, and the eigenfrequencies are obtained for harmonic thickness and anharmonic lateral overtones for a given bevel angle and thickness-to-length ratio of the linearly tapered crystal strip. Both the clamped and free-edge boundary conditions are considered.
Inhomogeneous waves and the plane-wave reflection coefficient
Authors: Frisk George V.
Published: October 2005

The importance of knowledge of the plane-wave reflection coefficient R for a horizontally stratified medium at complex angles of incidence ϑ=π/2−iα (α≳0) is established. It is shown that for a point source, when the combined source/receiver height is less than one-quarter wavelength, these inhomogeneous plane waves can make significant contributions to the reflected field. But irrespective of source/receiver height, they are important when normal modes are excited in slow speed regions of the bottom via inhomogeneous–pure wave conversion, thus giving rise to poles in the reflection coefficient. The theory of inhomogeneous plane-wave reflection is examined within the context of conservation of energy, and an expression for the intensity of these waves is derived. It is shown that although ‖R‖ is bounded by unity for real incident angles, it can be unbounded for complex angles without violation of energy conservation. A general asymptotic result for R for large horizontal wavenumber is also derived. The computation of R for inhomogeneous waves is illustrated for three canonical bottom examples: (a) impenetrable, (b) isovelocity fluid, and (c) isovelocity fluid layer overlying an isovelocity fluid half-space.
The equivalence of bottom loss and mode attenuation per cycle in underwater acoustics
Authors: Tindle C. T.
Published: October 2005

The attenuation of a normal mode in one mode cycle distance and the reflection loss of a plane wave incident on the ocean bottom at the equivalent ray angle are shown to be numerically equal for deep isovelocity water over an arbitrary layered bottom. The effect of a varying sound speed in the water and of changing the number of modes is examined. The results are used to derive a new invariant expression for the mode cycle distance.
Acoustic propagation in random oceans using the radiation transport equation
Authors: Wilson H. L. , Tappert F. D.
Published: October 2005

A new theoretical approach to the modeling of acoustic propagation in randomly fluctuating oceans has been developed based on radiation transport equations which describe the evolution of the mutual coherence function of the acoustic pressure field. A general computer program has been developed to implement this theory for a large class of scattering models, including volume scattering by random internal waves and rough surface scattering by fully developed seas or long wavelength ocean swells. The radiation transport code at present deals with CW signals in two spatial dimensions and is used to calculate transmission loss. It has been applied to the problem of surface duct propagation with special emphasis on modeling the scattering out of the duct by random fluctuations and below-duct ensonification. Comparisons have been made to a set of experimental data reported by Pedersen and Gordon [J. Acoust. Soc. Am. 37, 105–118 (1965)], with generally excellent results.
The vibrations and radiated noise associated with a constrained spherical shell in response to a turbulent boundary layer excitation
Authors: Garrelick Joel M.
Published: October 2005

An analysis is presented of a constrained, fluid-loaded, thin spherical shell subjected to a random pressure field associated with a turbulent boundary layer (TBL) excitation. The constraint is modeled as an axisymmetric, radially oriented impedance ring and the TBL is defined in terms of a cross-spectral density. Numerical results are generated for the spectrum density of the shell response as well as for the associated radiated pressure field. It is shown that under the assumption of an effectively delta function-like correlation length for the TBL pressure field, the constraint can have a far greater effect on the radiated pressure than on the overall response of the shell itself.
Effect of masker level on detection of a tone in pseudorandom noise
Authors: Raab David H. , Bernstein Richard S.
Published: October 2005

Masking of a tone by a sample of pseudorandom noise was studied as a test of Poisson-counting models of auditory detection. The noise waveform did not change throughout the experiment and the 1000-Hz signal was added to the masker in fixed ’’phase.’’ Three different samples of noise were utilized. Masking functions for three listeners showed that the signal-to-noise ratio at masked threshold did not change as the level of masker was increased from 30 to 80 dB SPL. The finding of Weber’s Law for these stimuli is not predicted by Poisson transduction models of detection.
The spectral content of the cochlear microphonic measured in scala media of the guinea pig cochlea
Authors: Hubbard Allyn E. , Mountain David C. , Geisler C. Daniel
Published: October 2005

Cochlear microphonic (CM) in response to low-frequency tonal stimuli, measured as a function of sound-pressure level (SPL) in scala media of the guinea pig cochlea, was averaged and Fourier analyzed. The slope of the amplitude of the Nth CM harmonic versus sound intensity in log–log coordinates was approximately N (1?N?5) in the first three cochlear turns, but notable variations on such a slope rule were found to apply to CM in turn I. CM harmonic phases plotted versus SPL were found to group into two distinctive categories expressly delimited by whether the order of the harmonic was even or odd. Some difference between CM recorded between scala media and scala tympani and recorded between scala media and the animal’s neck could be attributed to neural contamination. We also found CM in its saturation region to have a hysteretic relation to the input sound pressure. At high sound levels, large, physiologically produced acoustic harmonics existed at the animal’s eardrum. Our data support an asymmetrical, saturating, single-valued nonlinearity as a model for CM generation at low sound levels. At higher sound levels a different, more complex, hysteretic nonlinearity seems mandatory.
BSR (wave V) and N1 latencies in response to acoustic stimuli with different bandwidths
Authors: Kramer S. J. , Teas D. C.
Published: October 2005

Shortlatency averaged responses to 0.02–6 kHz broadband (BB) and 2 kHz narrow-band (NB) filtered clicks were recorded from the ear canal and the vertex of five adults with normal audiograms. Response latencies to the signals presented in quiet and with masking noise were compared. For constant spectrum level, the low-frequency limit of the masking noise was systematically increased to 6 kHz. The upper-frequency limit was always 8 kHz. For signals at 40 dB HL, the latencies of wave V and N1 decreased as the lower limit of the noise was raised and nearly equaled the latency for the signals presented in quiet. For signals at 70 dB HL, the latency in quiet was much less than that observed for all noise conditions, i.e., frequencies above 8 kHz would be required to interfere with the signal-dependent synchronous neural activity. Similar effects were measured for both wave V and N1, but the analysis of wave V–N1 latency intervals suggested a possible signal dependency.
Maximum entropy array processing
Authors: Skinner D. P. , Hedlicka S. M. , Matthews A. D.
Published: October 2005

Results of a simulation study of the application of the complex one-dimensional maximum entropy spectral analysis algorithm to the problem of localizing and resolving discrete targets using a linear array are reported. Of particular interest in this study were the errors in bearing esitimation and statistical stability of the estimated array response. The rms error in the source bearing estimates was observed to increase with decreasing signal-to-noise ratio (SNR), when the model order (p) approached the number of array elements (N=31), and when the source of interest was not well separated from adjacent sources. Typical rms errors observed for isolated sources (for p?N/3) ranged from 0.02λ/D at an SNR of 17 dB to 0.5λ/D at −9 dB. The statistical variability and number of spurious peaks in the array response were observed to increase rapidly as p approached N. At SNR less than 0 dB the array response, even when averaged over 50 independent data sets, indicated numerous spurious sources when the model order was large. The equivalent number of degrees of freedom (df) of the array response, estimated as twice the square of the average divided by the variance of the response, were calculated and compared with df=N/p as conjectured by Parzen and demonstrated (asymptotically) by Kromer. Parzen’s conjecture was consistent with the observed results for p≪N, but was found to be very optimistic at high model orders. It was also found that for the given array parameters the spatial response to an individual point source increases in width in the presence of nearby targets as well as with decreasing signal-to-noise ratio; and while the spatial response to a single point source is typically much narrower for maximum entropy processing, the minimum angular separation required for the resolution of adjacent sources is only slightly less (roughly a factor of one-half) than that of a conventional beamformer even at relatively high (17 dB) signal-to-noise ratios.
Analytic expansion technique for ambient-noise directionality determination
Authors: Yen N.
Published: October 2005

A new technique, based on the formation of the noise field, has been developed to determine ambient-noise directionality in relation to a line array. A computing algorithm is derived from the assumption that the cross-spectrum function of a noise field is analytic and can be expressed in terms of a superposition of plane waves. The angular resolution of the noise field obtained with this approach is not limited by the finite length of the array’s aperture. A simulated noise field and actual sea data are used in illustrative examples for comparison with conventional methods.
Flexural vibrations of certain full and annular composite orthotropic plates
Authors: Greenberg J. B. , Stavsky Y.
Published: October 2005

The uncoupled equation of motion for the flexural displacement of an orthotropic composite circular plate having symmetric lamination is presented. A numerical method is employed to calculate the symmetric and nonsymmetric vibrational frequencies of full and annular composite plates subjected to a variety of boundary conditions. Effects produced by lamination interchange and fiber reversal are discussed; in particular, certain laminations are capable of producing a higher fundamental frequency than either of the constituent materials alone can attain. For annular plates it is found that for certain lay-ups the fundamental frequency derives from a nonsymmetric mode. Finally, pinhole-center annuli are examined and, for a free inner edge, a comparison is made with corresponding full-plate frequencies.