bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved compact parametric hydrophone: theoretical and experimental results
Authors: Cotsarc R. D. , Jarzynski J.
Published: October 2005

The performance of a conventional parametric hydrophone is greatly improved by placing a silicone rubber cylinder between the pump and receiver transducers. For example, with 23-cm separation at 15 KHz, efficiency is increased by 21 dB, while simultaneously directivity is improved by a factor of 2.6. These improvements are primarily due to the slow speed of sound in silicone rubber (∼1000 m/sec) which allows the cylinder to behave as a slow acoustic waveguide. We also performed a theoretical analysis of sound propagation in this system for two reasons: to improve our basic understanding of this acoustic system, and to enable future optimization of the geometry. In a manner similar to that of Ryder, Rogers, and Jarzynski [J. Acoust. Soc. Am. 59, 1077 (1976)], we numerically solved the system of equations obtained by coupling the interior surface Helmholtz equation to the integral equation for the cylinder's exterior. The resulting calculated beam patterns are in excellent agreement with those experimentally measured.
Vibration and sound radiation of a time excited plate
Authors: Skudrzyk E. J.
Published: October 2005

The exact solutions for the vibration and the sound radiation of a line excited infinite plate are relatively complex and can only be derived by numerical integrations. These solutions will be interpreted physically, and approximations will be derived by replacing the sum of the mode contributions of a finite plate by an integral. [Work supported by NAVSEA.]
Effectiveness of a baffle in a distributed noise field
Authors: Mohnkern G. L.
Published: October 2005

The noise field created by independent dipole sources uniformly distributed on the surface of the ocean is one of considerable interest for midfrequency SONAR's. The effectiveness of a semi-infinite horizontal baffle in reducing the output noise power of an array in such a noise field was theoretically examined. Diffraction of sound from the distributed sources by the edge of the baffle was included in the model. Analysis showed that the use of a horizontal baffle in the dipole noise field reduced array noise power for linear and planear arrays by 3 or 4 dB. Most of this reduction was due to the baffle obscuring the noise field from the secondary main lobe. For three dimensional arrays, which do not have a secondary main lobe, the reduction in noise power was 1–2 dB. It was also found that the effect of diffraction on the array noise power was usually 1 dB or less.
Transient interaction of an acoustic pulse with a circular platform lying on the surface of shallow water
Authors: Sabbagh Harold A.
Published: October 2005

The transient response of a circular platform that is excited by an acoustic point source is computed by means of a numerical inversion of Laplace transforms. The platform lies on the free surface of a plane-parallel fluid region that overlies an elastic half-space. The point source lies within the fluid region. Because all fluid-elastic boundaries are plane-parallel, we are able to solve the problem by the use of Fourier—Bessel transforms in the spatial domain. The response of the platform is determined by first computing the normal modes of the platform, using two-dimensional finite elements, and this result is then coupled to the layered half-space by means of N-port theory. The effects of varying the fluid-bottom depth and the depth of the point source are presented.
Florida's noise control progam: Past, present, and future
Authors: Borthwick Jesse O.
Published: October 2005

Florida's Noise Control Program had its beginning in 1971, when the Florida Legislature amended the statutory responsibility of the Florida Department of Pollution Control (now Department of Environmental Regulation) to cover noise, as well as air and water pollution. The history of the Noise Control Program is outlined with emphasis placed on major difficulties encountered and significant accomplishments. The status of two existing program elements, motor vehicle noise control and local noise program assistance, which are both supported by a unique low-cost system involving five Florida Universities, is discussed. In closing, the program's overall planning philosophy of defining “excessive” noise, identifying noise sources, and controlling “unnecessary” noise is reviewed.
Noise reduction by a lightweight barrier
Authors: Halliwell R. E.
Published: October 2005

The noise attenuation due to a barrier constructed parallel to a building facade has been studied to test for filling in of sound in the semireverberant space between the barrier and building. The excess attenuation in each 13-octave band from 125 to 4000 Hz was measured and compared with the predictions of Maekawa. Measurements were also done with the barrier in a free-field configuration, remote from the house. Results show that there is negligible filling in of sound and that the excess attenuation agrees well with the Maekawa predictions in both cases. The barrier was relatively light (2.5 kg/m2) and, although the performance was therefore limited by the transmission loss, the maximum excess attenuation of A-weighted levels was found to be greater than 19 dB.
Motorcycle noise in the community—a review
Authors: Walsh John B. , Hagie Roger , Harrison Robin T.
Published: October 2005

Motocycle noise is a subject of public concern at the local, state, and federal levels. The Motorcycle Industry Council (MIC), representing most major motorcycle manufacturers, has sponsored recent community motor vehicle sound level surveys to assess the significance of the impact of motorcycle noise in different communities. We will present the results of these surveys and compare them with survey results of other researchers. We will also discuss the implications of these test results on community noise control strategies.
Psychophysical tuning curves for the goldfish
Authors: Fay Richard R. , Orawski Arthur T. , Ahroon William A.
Published: October 2005

Psychophysical tuning curves were obtained for the goldfish using a classically conditioned respiratory method. Pure tones and 40-Hz-wide noise bands were used as signals, and pure tones were used as maskers. In general, tuning curves are “V”-shaped with Q10 values increasing from about 1 to 9 as signal frequency is increased from 100 to 1000 Hz. However, tuning curves obtained for signal frequencies of 300 Hz or above showed pronounced secondary peaks occurring several hundred Hz above and below the signal frequency. Neurophysiological tuning curves for goldfish saccular neurons [R. R. Fay, J. Acoust. Soc. Am. 60, S80(A) (1976)] show considerably less tuning with Q10's not exceeding about 1.5. This suggests that some additional filtering is occurring in the goldfish auditory system which is based on principles other than those thought to operate in mammalian systems. We suggest that the envelopes of the multipeaked psychophysical curves reflect a tuning mechanism peripheral to the impulse generating processes of auditory neurons, while the peaks themselves are a result of a central neural tuning mechanism. [Work supported by a grant from the NSF to R. Fay.]
Auditory MTF derived with modulated noise
Authors: Weber Daniel L.
Published: October 2005

A sinusoidally amplitude-modulated noise masked a 2-kHz sinusoidal signal. Threshold for the signal was determined as a function of the modulation frequency of the noise for three noise spectrum levels. Estimates of an auditory modulation transfer function (MTF) were obtained using the method described by Buunen (T. J. F. Buunen, Doctoral dissertation, Delft University of Technology, The Netherlands). The estimates of the transfer function have the form of low-pass filters; the cutoff of the filter increases slightly with masker level towards a maximum on the order of 40 Hz. [This research was supported in part by the National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare.]
Analysis of sequential effects in absolute identification of sound intensity for 1000-Hz tone pulses
Authors: Purks S. R. , Lira J. S. , Bralda L. D. , Durlach N. I.
Published: October 2005

When observers identify intensities in large-range experiments, the response in a given trial is affected by stimuli presented previously. The effect of the stimulus in the preceding trial is generally strongest when feedback is available: the given response assimilates toward the preceding stimulus and the variability of the given response is reduced when the preceding stimulus is close to the present stimulus [e.g., M. K. Holland and G. R. Lockhead, Percept. Psychophys. 3, 409–414]. To examine these effects in more detail we analyzed the performance of four listeners who identified 15 intensities spaced over a 56-dB range in an experiment involving roughly 15 000 trials. The stimulus on the preceding trial affect the listener's criteria on the given trial systematically, but has relatively little influence on sensitivity. Thus, the improvement in sensitivity that accompanies the availability of feedback [L. D. Braida and N. I. Durlach, J. Acoust. Soc. Am. 51, 483–502] cannot be explained simply by assuming that the observer uses the preceding stimulus as a reference. [Work supported by NIH and NSF.]
User adaption in operational speaker verification
Authors: Doddington George R. , Hydrick Barbara M.
Published: October 2005

Texas Instruments controls entry to its corporate computer facility by speaker verification. During two and one half years of operation, 0.4 million verifications have been performed for 300 users. Current performance is 99.9% user acceptance with 99% impostor rejection. Initial user acceptance is not as good (99%), but steady-state performance is achieved after 50–100 verifications. Careful user orientation is important, and user adaptation and voice consistency continue to improve over a long period of time. The variance of input speech data for those 36 users (24 men, 12 women) who had been verified at least three thousand times was plotted versns session number. Average variance was 108 at 250 sessions, 105 at 500, 101 at 1000, 96 at 2000, and 93 at 3000 sessions. How do you explain this continued improvement?
Tone space and universals of tone systems
Authors: Hombert Jean-Marie
Published: October 2005

The purpose of this paper is to present a mathematical model which predicts the most likely tone shapes of a tone system. Given the total number of lexical tones the model will output two numbers for each tone. The first number represents the onset and the second number the offset of the tone on a five-point scale. This model is based on the principle of maximal perceptual distance and minimal articulatory difficulty. The parameters measuring perceptual distance and articulatory difficulties were obtained from consideration of previously reported data by other researchers and two recent experiments, The effect of using various measurements of perceptual distance (euclidian, city block, etc.) and various relative weights for articulatory vs auditory factors is also investigated. The predictions made by the model were satisfactorily matched with actual data from more than one hundred tone languages. The notion of “most likely tone shapes” based on a trade off between maximum perceptual distance and minimum articulatory difficulty is very useful for understanding why and how tone systems evolve. [Work supported by NSF.]
Stress correlates in Montreal French
Authors: Yaeger Malcah , Kemp William
Published: October 2005

We have impressionistically determined the meaningful stress categories for Spontaneous Montreal French. These categories are distinguished by variations of F0, amplitude, and syllable duration. Sentential stress is realized phonetically as reduced fundamental and amplitude, but increased duration of the final syllable. In contrast, comma stress is realized as raised amplitude and either (a) raised F0 with no durational increment (“emphatic stress”), or (b) a fall—rise contour with some durational increment (“list intonation”). In all cases we find [similarly to Klatt, J. Phonet. 3, 159 (1975); Kloker, J. Acoust. Soc. Am. 57, S33 (A) (1975)], the word preceding the stressed word is lengthened. We analyzed the interaction of stress with syntax and with variable phonological realization of certain segments. Whereas the durational and pitch correlates of stress appear fairly constant across all eight of our speakers analyzed in depth to date, the influence of stress on consonant cluster retension and on rate and trajectory of diphthongization of monophthongs is determined by social factors. [Research funded by Killam Grant: Conseil des Arts.]
“I don't WANT to see her grease gun fittings”—Do post-nuclear accents occur in English?
Authors: Vanderslic Ralph
Published: October 2005

Encoder subjects hears, for each item, a disambiguating context such as either “Mac has some cover stories,” or “Max is covering some stories,” followed by the cue “Let's go and see them/him.” Subjects' task was to respond emphatically and negatively in the form “I don't WANT to go and see Mac's/Max cover stories.” These responses were recorded on tape and played to decoder subjects, whose task was to repeat the target phrases in citation form—i.e., with disambiguating accentuation. According to received prosodemic theory, decoders should reliably recover the structures given to encoders, whose responses would, ex hypothesi, carry the same “stress” distinctions, merely realized at weaker “levels.” In fact, however, the patterns given to encoders and those elicited from decoders failed to show significant (above chance) agreement. This finding is interpreted as support for the theory of “binary” suprasegmental features [R. Vanderslice and P. Ladefoged, Language 48, 819–838 (1972)], which claims that the feature ACCENT does not occur postnuclearly (i.e., the intonation contour, in this case CADENCE, begins with the last accented syllable of the sense group), and thus predicts exactly the loss of prosodemic contrast observed in these cases. The tune in question, with leftward “shift” of the sentential accent to the emphatic word WANT, must not be confounded with one also having EMPHASIS (and thus typically highest pitch) on WANT, yet with unshifted sentence accent on either cover or stories. The latter, disambiguating, tune is superficially similar but systematically distinct. It should also be noted that the “binary” prosodic features can, mutatis mutandis, be viewed as singularly elements (morphons) in a Cognitive-Stratificational account of English suprasegmentals.
Modeling of durational patterns in reiterant speech
Authors: Liberman M. Y.
Published: October 2005

In a paper presented at the 1976 ASA fall meeting, Liberman and Streeter [J. Acoust. Soc. Am. 60, S27 (A) (1976)] in which a nonsense syllable is substituted for each of the original syllables of a target phrase) shows stable durational patterns, influenced by the stress and constituent structure of the target phrase, and relatively unaffected by its segmental makeup. In the present paper, a model of durational patterns in reiterant speech is described, and used to argue that English stress patterns maintain their phonetic reality even when they are not differentiated by pitch.
On S duration: a case for surface and underlying representation
Authors: Ingrisano D. , Weismer G.
Published: October 2005

Attempts to detail minimum/maximum intrinsic durational characteristics of phonetic segments and thereby deduce underlying phonemic correspondence is complicated by several factors (stress, number of syllables, syntax, nature of carrier phrase, orthography, etc). The objectives of this study were twofold: (a) to determine minimum/maximum durational characteristics of [s] while systematically permuting lexical and sentential stress, morpheme and syllable location, and syntax, and (b) to examine the hypothesis that an underlying double [s] may account for longer [s] durations observed in the first member of stimulus pairs such as misstep vs. mistake [Klatt, J. Speech Hear. Res. 17, 51–63 (1974)]. In order to control orthographic effects, subjects participated in two experimental conditions which consisted of Delayed Imitation and Reading of target phonemes embedded in sentential material. The responses of 20 subjects were tape recorded, and duration data were derived from oscilloscopic displays under consistent segmentation criteria. Results are discussed relative to intrinsic durational characteristics of [s], the influence of phonemic representation upon the temporal structure of [s], and the influence of orthographic effects on the study of durational phenomena.
Speech production measured of speech perception: replications and extensions
Authors: Porter R. J. , Castellanos F. X.
Published: October 2005

In the early 1960's, Chistovitch and her colleagues used rapid shadowing (vocal reaction time) and manual reaction time to explore the perceptual processing of speech. Two ingriguing aspects of their data were the relatively fast vocal reaction times and the subjects' tendency to begin articulatory responses before all of the acoustic cues for consonants were presented. These results, among others, support the classic notion of an intimate link between perceptual analysis of speech signals and the mechanisms of control in speech production. The study to be reported replicates and extends some of Chistovitch's paradigms using modifications designed to eliminate possible sources of confounding. Results tend to support the conclusions of the Russian researchers and point to the additional ways in which the modified procedure might be used in exploring phonetic decoding. [Supported by NIH and the Sloan Foundation.]
Ultrasonic activation of stabilized gas bodies at frequencies in the lower megahertz range
Authors: Miller D. L. , Byborg W. L.
Published: October 2005

A microscopic gas body is stabilized against diffusion if it exists in a hole at the surface of a solid. Certain membranes sold commercially for filters (e.g., polycarbonate membranes prepared by Nuclepore Corp.) provide holes of micron dimensions, and under suitable conditions air remains trapped in these holes when they are immersed. The gas bodies so formed are suitable for strong activation at frequencies of 1–10 MHz. Experiments have been done in which suspensions of small particles are subjected to ultrasound in the presence of various membrane configurations. When the suspension can be viewed through a microscope during irradiation it is found that movements of suspended particles are visible near the gas-filled pores even at pressure amplitudes as low as 0.1 bar. The movements are apparently a result of radiation force and acoustic microstreaming, such as are expected near a pulsating gas bubble. In experiments with biological suspensions it is found that significant changes are produced at relatively low intensity levels. A film will be shown. [Work supported by the NIH through grant GM08209.]
Acoustic excitation of capillary oscillations in levitated liquid drops
Authors: Marston P. L. , Apfel R. E.
Published: October 2005

Capillary oscillations of liquid drops suspended in a host liquid are of interest as a method for measuring the interfacial tension between superheated and normal liquids. Furthermore, they may provide a method of enhancing heat and mass transfer across the interface. We have developed a sensitive method using optical interferometry for detecting drop shape oscillations. Microliter hydrocarbon drops are levitated in water with a 51-kHz acoustic standing wave [see, e.g., paper UU9 by R. E. Apfel at this meeting]. A 700 kHz acoustic wave is applied using the same transducer. The latter wave is modulated at a low frequency such that the square if its pressure is proportional to (1 + sin2πft) where f ≃ 200 Hz. It has a radiation pressure on the drop surface proportional to (1 + sin2πft) which excites the shape oscillations. Oscillations are detected when f is approximately the frequency predicted by viscous theory for the maximum amplitude of quadrupole oscillations. [Work supported by The American Chemical Society Petroleum Research Fund.]
A measure of relative randomness in the acoustic emission from a cavitating medium
Authors: Sketch M.
Published: October 2005

As transducer power is slowly raised during cavitation experiments with tap water, the magnitude of fluctuations about a “mean” pressure waveform varies considerably. Neither mean square pressure nor frequency domain measurements emphasize these fluctuations which seem to dominate the time domain observation. In general, instantaneous pressure measured in a cavitating medium lies between the traditional extrema of “random” and “deterministic.” Informational entropy provides a measure of relative disorder, or randomness. Knowledge of the amplitude probability distribution is, however, required. Variance, conceptually related to entropy and similar in definition, may be more simply instrumented as a difference between mean square and square of the mean (absolute value) pressures. The equivalence of statistical and time averages (ergodicity) is assumed. Normalizing with respect to mean square pressure renders the parameter “absolute value normalized variance”—AVNV—amplitude independent. AVNV has provided experimental information on gaseous and vaporous cavitation development not revealed in either time or frequency domain measurements, as well as correlation with cavitation related processes. The parameter may be useful in such diverse applications as the detection of boiling in nuclear reactors or cardiac arythmia surveillance.
Intensity discrimination with three signal ensembles
Authors: Stiegel M. S. , Bilger R. C.
Published: October 2005

Detection of beats in the envelope of a 1000-Hz pulsed carrier was compared to discrimination of intensity differences obtained by in-phase addition to determine if they give comparable measures. Beats were generated by two methods, amplitude modulation and addition of a second sinusoid. For a 500-msec signal, data were obtained for 2, 4, and 8 beats. A 2IFC procedure was used to generate psychometric functions on three normal-hearing subjects at four carrier levels (15, 30, 45, and 60 dB SPL). All three ensembles provided results that exhibit the “near miss” to Weber's law when examined as masking data. The actual difference in power (or energy) between the signal and the nonsignal interval at differential threshold was appreciably smaller for beat detection than for increment detection. It is unlikely that this small difference in incremental energy is the basis for beat detection. When east in terms of the ΔE/E of Reisz [R. R. Riesz, Phys. Rev. 31, 867–875 (1928)], the data for beat detection reflect slightly poorer discrimination than those for increment detection. The differences between beat and increment detection will be discussed in terms of models of audition.
Temporal integration of loudness under various conditions of contralateral stimulation
Authors: Ahaus W. H. , Stokinger T. E.
Published: October 2005

A study was conducted to investigate the effect an ongoing auditory stimulus presented to one ear might have on loudness summation in the opposite ear. This knowledge would be relevant in interpreting the results of experiments employing simultaneous dichotic loudness balances to measure, for example, perstimulatory adaptation. Three experienced listeners matched the loudness of variable-duration (0.01–3.0 sec), 1-kHz sinusoids to the loudness of a 1-sec, 1-kHz sinusoid presented at 60 dB SPL, using a transformed up/down procedure. These loudness-summation functions were obtained under each of five contralateral-stimulation conditions: silence (control condition), continuous 60-dB SPL white noise, and continuous 1-kHz pure-tone stimulation at 75, 60, and 45 dB SPL. The presence of a contralateral stimulus had no real effect on the shape of the loudness-summation function. [Work supported by the Veterans Administration.]
Temporal integration of combined tone glides
Authors: Cullen J. K. , Collins M. J.
Published: October 2005

Temporal integration of tone glides in frequency ranges corresponding to first and second formant regions of speech were reported at the previous meeting of the Society [M. J. Collins and J. K. Cullen, Jr., J. Acoust. Soc. Am. 60. S48 (A) (1976); Nabelek, J. Acoust. Soc. Am. 60, S48 (A) (1976)]. These studies demonstrated a slower rate of integration for tone glides for fixed frequencies, with an asymmetry between functions for rising and falling glides. The current investigation extends these observations to combined tone glides in the frequency ranges 200–700 and 1200–1700 Hz. Integration of all possible glide combinations was investigated for durations of 5–120 msec. Results indicate an asymmetry in the integration functions for sets where both glides rose and both glides fell, with mixed glide sets yielding intermediate functions independent of which glide rose or fell. Thresholds for detection suggest partial summation occurs across glide components even though instantaneous frequency values are separated by more than a conventional critical band. [Work supported in part by NIH and the Sloan Foundation.]
Memory for auditory, sequences by monkeys: determination of pro- and retroactive interference
Authors: Dewson James H.
Published: October 2005

Several Old World monkeys (M. fascicularis) have demonstrated their ability to remember, after delay intervals of many secs., various sequences of acoustic stimuli. Both the nature of a given sequence as well as the order of the two elements which comprised it were shown routinely by the animals to have been retained at >90% correct response levels during months of daily test sessions [J. H. Dewson III, Acoust. Soc. Am. 57, S11 (A) (1975)]. Detailed analysis of the errors made on this complex conditional match-to-sample task reveals the effects on memory of strong proactive interference (PI) when the elements of a sequence are of equal (0.5 sec) duration. By selectively altering the relative durations of the two elements, the situation can be reversed to one in which retroactive interference (RI) is clearly shown. This demonstration of PI and of RI in individual animal subjects, obtainable within single testing sessions, provides an indication of basic similarity of memory processes across the primate order.
Latent components of evoked potentials related to phonological and semantic features of verbal stimuli
Authors: Papanicolaou A. C. , Molfese D. L.
Published: October 2005

Neuroelectric correlates of phonological and semantic features were identified using Principal Components analysis on scalp recorded evoked potentials. Sixteen repetitions of four stimulus phrases The/bi/, The/si/, To/bi/, and To/si were presented to subjects while evoked potentials to the /bi/ and /si/ stimuli were recorded over the temporal sites of both hemispheres. Eight averaged evoked potentials (AEPs) were obtained from each subject [i.e., 4 stimuli × 2 hemispheres]. AEPs from 28 subjects were factor-analyzed treating AEP amplitudes at 146 equidistant time points as variables. The analysis resulted in 21 orthogonal factors accounting for 91% of the total variance. Matching the factors or components to the experimental conditions was accomplished by submitting the scores computed for each AEP on each factor to a 2 (hemispheres) by 4 (stimuli) ANOV, [Molfese, Nunez, Seibert, and Ramanaiah, Ann. N.Y. Acad. Sci. (1976)]. Several components corresponding to phonological and semantic features were identified in that their scores differed reliably for both /bi/ vs /si/ stimuli independently of semantic context and for noun versus verb instances of either stimulus.
Signal processing for a shipborne noise and vibration monitoring system
Authors: Hackett D. W. , Hirschfield G. A.
Published: October 2005

OTI has developed and is producing a shipboard signal processor for interfacing noise and vibration sensor signals with a digital computer and narrow-band spectrum analyzer. The Monitoring System Signal Processor (MSSP) provides for 144 accelerometer and 6 hydrophone inputs, as well as A/D rand D/A conversions of auxiliary dc, ac, and discrete signals. The MSSP scans the input channels and conditions the incoming signals which are then fed through a bandpass filter and selector. The selected band is connected to a variable gain amplifier. The scaled analog data are low-pass filtered, sampled, and converted to digital format. A block of 2048 digital samples are then stored and block transferred to the computer. The computer transfers the data to a separate spectrum analyzer for narrow-band frequency conversion and 13 octave band generation. The computer provides for storage of threshold values for various ship speed ranges, and generates alarms and displays for operator action when these limits are exceeded. The system can be reconfigured to incorporate the frequency transform function into the MSSP. In conjunction with a small computer and suitable peripheral equipment this would comprise a compact NVM system for shipboard or industrial applications. [Work supported by NAVSEA and NAVSEC under Contract N00024-75-C-7217.]
Eardrum representation in middle-ear acoustical networks
Authors: Shaw E. A. G.
Published: October 2005

The Zwislocki network gives a good account of middle-ear function in normal and abnormal ears up to 2000 Hz [see J. Acoust. Soc. Am. 34, 1514 (1962)]. At higher frequencies, however, the input impedance of the network remains capacitive which is evidently at variance with the anatomy of the human eardrum and ear canal. The fraction of tympanic membrane which is tightly coupled to the malleus, while large at low frequencies, is clearly quite small above 4 kHz. As a first approximation this system can be described as a pair of rigid pistons with compliant coupling. The proper representation of such a system requires the introduction of an ideal transformer into the middle-ear network. An area ratio of 4:1 is suggested. With this modification the reactive component of network impedance becomes positive at high frequencies, as required. It remains to be shown that the impedance magnitude, also, can be reconciled with the available experimental evidence.
Place mechanism underlying frequency analysis in the toad's inner ear
Authors: Capranica R. R. , Moffat A. J. M.
Published: October 2005

The inner ear of toads has two distinct auditory organs. One of these, the amphibian papilla, gives rise to fibers which have a distribution of best excitatory frequencies (BEF's) while the fibers from the other organ, the basilar papilla, all have very similar BEF's. We recorded responses from single fibers from each of these organs in response to paired clicks in which in the interclick interval was varied systematically. Each fiber showed a firing probability which varied cyclically with interclick interval, indicating that the system impluse response within each organ is a damped oscillation. Furthermore the period of the firing probability curve of each fiber was equal to the reciprocal of its BEF. These results demonstrate that in the amphibian papilla frequency analysis is based on a place mechanism whereas the basilar papilla is a simply tuned resonant structure. [Supported by NIH.]
Scalar timing control in spontaneous speech
Authors: Anderson S. W. , Podwall F. N.
Published: October 2005

Phonological phrases were detected and segmented into syllables from the ongoing digitized oscillogram (low pass, 2 kHz) by a PDP-12 computer, utilizing a minimum interphrase silence of 200 msec, vowel onset and offset criteria of ±6 dB within a 20-msec window. Subjects spoke freely on three topics, 5 min per topic. Significant scalar timing (σ/μ=k) for phrase duration was found by stepwise regression analysis across the three topic samples. This timing control was determined to be neither a cumulative syllable count phenomenon, nor a general articulatory rate change (Allen, 1973). Rather, phrase variance within topic remained quite stable regardless of syllabic length, and the scalar changes between samples were unaccompanied by corresponding shifts of stress unit duration. Mean durations of initial, medial, and final stressed vowels in four of the six subjects were well fitted by Lindblom and Rapp's (1973) vowel-length contour equation, which presets vowel lengths in a phrase on the basis of the syllable count. The scalar property has often been found in studies of temporal estimation (Gibbon, 1977). Our results suggest that human phrase length is determined by estimation from a preplanned template, rather than by summing syllabic units of typical durations.
Relative contributions of diffraction, facet reflections, and interference to the field backscattered by a randomly rough surface
Authors: Novarini J. C. , Medwin H.
Published: October 2005

In a previous communication [J. C. Novarini and H. Medwin, J. Acoust. Soc. Am. 61, S37–S38(A) (1977)] near-grazing acoustical shadowing was discussed in terms of the results of a computer model study of boundary-diffracted waves. This work has been extended to clarify the contributions due to diffraction as well as facet reflections from long-crested surfaces having a Newmann-Pierson spectrum. The technique shows the importance of wave height and facet reflection with interference near normal incidence contrasted with wave slope and diffraction away from normal. Results are shown for backscattering strength as a function of frequency and angle of incidence for wind speeds of 5, 10, and 20 m/sec. [Work supported by ONR and the Research Council, Naval Postgraduate School.]
Preliminary investigation of reflectivity from the basalt-water interface
Authors: Diachok Orest , Dicus Ronald L.
Published: October 2005

Ocean bottom reflectivity was measured as a function of grazing angle and frequency using explosive signals and omnidirectional hydrophones at a sediment-free site on the Mid-Pacific Rise. The bathymetry at this site, which had been previously surveyed by the Scripps Institute of Oceanography using deep-towed instrumentation, is characterized by strong azimuthal anisotropy. Reflectivity measurements were made along directions parallel and normal to the axis of the rise; the resultant bottom-reflected signals were processed for bottom loss. To illustrate the relative magnitudes of the dominant effects of this particular type of ocean bottom on the reflection process, the results of the reflectivity computations are discussed in terms of the observed dependence on frequency, grazing angle, and the elastic and roughness parameters of the basalt.
Prototype model for volume backscatter strength in the upper ocean caused by light-sensitive biological scatterers
Authors: Saenger R. Alfred
Published: October 2005

It is known that biological scatterers in near-surface sound-scattering layers often tend to follow isolumes. By assuming a distribution of preferred isolumes tracked by the scatterers, exponential attenuation of downwelling light intensity with depth, and a uniform depth-invariant backscatter cross section for each scatterer, a theoretical model for volume backscatter strength S(z) can be derived. Thus, if truncated normal, log-normal probability density functions are assumed to describe the distribution of preferred isolumes, then S(z) is a quadratic function of exp(αz); z, where α is the optical extinction coefficient. Despite the simplicity of the physical assumptions, these two particular models together provide a good phenomenological description of a number of experimental midnight and mid-day 3.85–15.5-kHz profiles obtained at the Ocean Acre site near Bermuda. [Work supported by Naval Material Command.]
Reverberation below the wind-mixed layer at 87.5 kHz
Authors: Kaye G. T.
Published: October 2005

Reverberation below the wind-mixed layer was observed from R/P FLIP with an 87.5-kHz echo sounder with a 1° acoustical beam and a source level of 227 dB//μ Pa. The reverberation was composed primarily of discrete scatterers with target strengths ranging from −38 to −73 dB. Densities varied from 0.05 to 50 scatterers per 1000 m3. It is shown that swimbladder fish, squid, and siphonophores have sufficient acoustical strengths to be discrete scatterers at this frequency; zooplankters like euphausiids and copepods do not have sufficient strength to be observed as individuals with this system. A midnight vertical migration was noted that corresponded with the passage of a rain squall. [Work supported by the Advanced Research Projects Agency and the Office of Naval Research.]
Rough surface scatter Doppler measurement by impulse probing
Authors: Zornig J. G.
Published: October 2005

In order to obtain rapid repeatable measurements of the frequency spreading produced by scattering of acoustic signals from a wind-ronghened surface, a measurement technique has been developed for use in conjunction with a model tank. The technique uses pre-emphasized impulsive probing signals to sample the scatter channel transfer function at a rate in excess of the Nyquist rate for fading. A large number of measurements at a variety of frequencies, beam patterns, and geometries have been made. These measurements are highly repeatable and precise. They show a variety of phenomena including upward and downward skewing of the Doppler spectrum, harmonics of the surface temporal spectrum, and a generally Gaussian spreading at high Rayleigh parameters. In general they are not in agreement with current predictive theories, but represent an excellent set of reference measurements against which to measure the effectiveness of future theoretical refinements. [Support: ONR (480), Naval Electronic Systems Cmd. (320).]
Calculation of the scattering from a ribbed cylinder by means of finite-element methods
Authors: Barach D. , Benthien G. W. , Gonzalez Manuel A.
Published: October 2005

The modeling of a large structure using finite elements, for the purposes of calculating radiation and scattering, is severely limited by the size of the matrices which must be inverted. In this paper, we investigate the application of the general theory of periodic structures [L. Brillouin, Wave Propagation in Periodic Structures (McGraw-Hill, New York, 1946), 2nd ed.] to the scattering of acoustic waves from a ribbed cylinder. This theory, when combined with finite-element methods, provides us with a powerful analysis technique. Results are presented on the backscattered pressure levels and structural displacements. The relationship between the normal modes of the structure and the displacements produced by an incident plane pressure wave are discussed. [Work supported by NOSC Internal Research Fund made available by the Director of Navy Laboratories.]
Effect of lamb-type waves on the form function of thin cylindrical shells
Authors: Dragonette Louis R.
Published: October 2005

The relationship between the reflection form function of thin cylindrical shells and circumferential waves is discussed. Specifically, the influence of two circumferential waves, which exhibit properties similar to those of the lowest-order Lamb modes, are considered. The form function is shown to give direct information about the phase of the specular reflection, with respect to the incident wave; the velocity of the “symmetric Lamb-type” circumferential wave; and the attenuation of the circumferential wave due to radiation into the water. Also, readily observable from the form function is the onset of the coincidence frequency for the excitation of the “asymmetric Lamb-type” circumferential wave.
Acoustic transients from planar axisymmetric vibrators using the impulse response method
Authors: Stepanishen F. R.
Published: October 2005

In the present paper an approach is presented to evaluate the transient near- and farfield pressures which result from the specified time-dependent velocity of a finite axisymmetric vibrating planar surface. The surface may represent the vibrating face of a disk transducer or it may represent the vibrating surface of a membrane or plate. The approach is based on expanding the velocity of the vibrator as a summation of radially dependent functions with time-dependent coefficients. The time-dependent pressure at any point in the field is then expressed as a summation of convolution integrals which involve the time-dependent coefficients and generalized impulse responses [P. Stepanishen, J. Acoust. Soc. Am. 49, 1628–1639 (1971)]. Applications of the approach to study the time-dependent pressure field which results from the axisymmetric motion of a disk transducer, membrane, and plate are discussed and numerical results are presented for specific cases of interest. [This work was supported by NIH.]
Fluid-loaded plate: Three real roots?
Authors: Stuart A. D.
Published: October 2005

For a time harmonic, locally excited fluid-loaded plate, the characteristics of the acoustic radiation and driving point admittance responses are determinable from an inverse integral transform whose integrand has five roots or singularities in the complex wave number domain. The roots of the integrand correspond to the zero of the specular acoustic impedance of the fluid loading plus that of the plate (Za+Zp). Generally only one of these roots is considered purely real, while the other four exist as two complex conjugate pairs. Physically this real root represents a clinging wave that propagates unattenuated parallel to the plate-fluid interface. One pair of the complex conjugate pair represents a reactive near-field phenomena that radiates no energy away from the plate surface. The other pair of complex conjugate roots each represent progressive waves that exponentially grow in the direction perpendicular to the plate surface: Above the coincidence frequency these roots are directly related to the resistive, farfield radiation losses from the plate. This paper will show that in certain frequency ranges below coincidence, and for certain plate-fluid combinations, the latter two complex conjugate roots become two distinct purely real roots. The significance of these two additional real roots on the radiation field and the driving point admittance will be discussed.
Underwater sound absorption characteristics of various species of wood
Authors: Lauchle G. C. , Barge F. A.
Published: October 2005

In this experimental investigation, the acoustic absorption characteristics of various species of wood, rubber, and wood/rubber composites were determined under low hydrostatic pressure and over the frequency range 10–50 kHz. The test samples, including white pine, douglas fir, redwood, fir plywood, Saper-Trubber, and bubble rubber were typically 4 ft sq and tested in a 948-gal semianechoic water tank. A tone-burst technique was used to minimize extraneous signals resulting from wall and surface reflections. The standing wave pattern was measured in front of each sample at discrete frequencies. From the standing wave pattern, and from the classical theory of waveguide propagation, the complex reflection factor, material longitudinal phase velocity, and attenuation per unit depth were determined as a function of frequency. It was found that the absorption characteristics of all woods improved as the moisture content increased to the saturation point. Redwood exhibited the best characteristics and this was improved by approximately 50% when backed by a 1/4-in. layer of Saper-T sound absorbing rubber. Fir plywood did not have the lowest reflection factor, but did exhibit the smoothest frequency response of the woods evaluated.
Current practices and future trends in the processing of airplane flyover noise data
Authors: Stouder Donald J.
Published: October 2005

Airplane flyover noise testing techniques have grown in complexity and sophistication during the past several years. This growth has resulted in substantial increases in the variety and quantity of data acquired in support of flyover noise test programs. In addition to the basic measured noise levels, large amounts of data describing airplane/engine performance, space position, and sound-path meteorological conditions are also acquired. Data processing procedures and techniques were developed to efficiently integrate these large quantities of flight test data onto a single computer tape, which can be easily used for analytical studies. The methods have been optimized to provide visibility of data validity, and to provide sufficient flexibility to accommodate the unique data requirements of each test program. The data processing cycle has been highly automated using both small- and large-scale digital computers. Near-term advances in data processing techniques discussed include (1) increased use of statistical analysis techniques using integrated subroutines, (2) advanced narrow-band spectrum analysis techniques for improved noise source description, and (3) increased use of automated error detection and correction techniques.
Comparisons of noise monitor data from California airports
Authors: Lane S. R. , Procunier Richard
Published: October 2005

Aircraft noise measurements were made adjacent to airport monitoring system microphone stations at five California airports and compared to corresponding noise levels indicated by the airport system. In addition, aircraft noise levels were measured simultaneously at various heights above ground level to determine the effect of microphone height on noise data reported by airport monitoring systems. Takeoff and approach noise levels for identified DC-9 aircraft were then compared at two airports and differences in results were evaluated. In general, the airport monitoring systems reported high levels than indicated by precision sound level meters, even though the microphone height effect should cause monitoring system output to be less than sound level meter data. Also, significant differences were found between DC-9 noise levels at the two different airports.
Effectiveness of linguapalatal place cues for a deaf speaker
Authors: Fletcher Samuel G. , Hasegawa A. , McCutcheon M. J. , Gilliom J. , Schwartz A.
Published: October 2005

The effectiveness of linguapalatal contact place cues were examined in a study of a profoundly deaf adult speaker. A 96-electrode pseudopalate was used to sense linguapalatal contact during utterance of isolated sounds, words, and short sentences. Contact was displayed by an LED array bounded by the maxillary teeth. Initial shaping procedures were directed toward establishing the/t, s, ∫/ sounds. The repertoire was then expanded to include contrating posterior plosives and the afficate /t∫/. Some attention was given to establishing high front vowels. Tongue contact patterns attained on the goal sounds from 20 treatment sessions approximated those of “normal” speakers. Pre- and postintervention intelligibility tests on nontreatment words indicated correct placement of the consonant sounds in over 80% of their occurrances. Physiological and perceptual characteristics of the changes will be discussed. [Supported by NIH Grant NS-11852-02 and HEW Grant RSA 16-P5680 7/4-11.]
Noise control considerations in the modernization of a Boston subway station
Authors: Kleinschmidt Klaus
Published: October 2005

The primary concern in the modernization program for the Park Street subway station was the intense wheel squeal on the sharply curved tracks (radii as small as 45 ft) at one end of the upper platform. Secondary concerns are reduction of the exposure of patrons to rolling and braking noise on the upper and lower levels. Measurements of existing acoustical conditions and typical noise levels of trains are described. The noise control treatments presently being installed and the anticipated reductions will be discussed. The practical performance characteristics required of acoustical materials for subway stations will also be summarized.