bluuebunny/crossref_metadata_2025 huggingface dataset:
Auditory brainstem response in a neonatal sperm whale, Physeter spp.
Authors: Carder D. A. , Ridgway S. H.
Published: October 2005

A sperm whale neonate, Physeter spp., was stranded near Sabine Pass, Texas in September of 1989. The Marine Mammal Stranding Network of Texas A&M University removed the animal to Sea-Arama Marineworld, Galveston, Texas where it was kept in a large tank for 8 days in an attempt at rehabilitation. During this period, the auditory brainstem response (ABR) was recorded from suction cup sensors on the surface of the head in response to pulses presented (20 and 40 pps) underwater near the right external auditory meatus and lower jaw. These are the first ABR records from a great whale and the first recordings from a neonate of any cetacean species. The ABR waves of this Physeter, in response to pulses ranging in peak frequency from 2.5 to 60 kHz, were similar in appearance to those seen in other mammals, and very similar to those previously observed in other odontocetes [S. H. Ridgway et al., Proc. Natl. Acad. Sci. USA 78, 1943–1947 (1981)]. The ABRs of highest amplitude were those to frequencies of 5, 10, and 20 kHz. Responses to 60 kHz were much weaker but definitely present. Latencies were prolonged compared with ABRs of other juvenile and adult odontocetes.
Measuring auditory filters efficiently
Authors: Dreschler Wouter A. , Leeuw A. Rens
Published: October 2005

Knowledge of the frequency-resolving power of an individual's ear may be helpful in hearing aid selection and in adjustment of multichannel hearing aids. A method using threshold measurements with notched noises, developed by Patterson, has been adopted as the best method. Patterson proved that the filter form can be assumed to be composed of two rounded exponential functions: W(g) = (1 − r) (1 + pg) × exp(− pg) + r, where g is the relative deviation from the filter center frequency for off-frequency listening, p defines the steepness of one of the filter skirts, and r limits the dynamic range of the filter. Up until now, auditory filters have been measured very precisely in conjunction with research requiring many threshold measurements. In clinical work, time is an important factor. For this reason we investigated the effect of a reduction of the number of threshold measurements on fitted filter characteristics. Filter estimates of 33 subjects (normal hearing, sensorineurally hearing impaired, and conductively hearing impaired) for three different measurement conditions have been analyzed. First, thresholds measured with five symmetrical and eight asymmetrical noises determined the parameters of the filter precisely. Second, the parameters were calculated with a reduced number of thresholds. Third, an alternative fitting procedure was employed. The influence of the reduction of the thresholds on the filter parameters, the effects of the alternative fitting procedure, and the need for retest measurements will be discussed.
Finite difference modeling and slowness-time analysis of modes in a submerged steel plate
Authors: Fricke J. Robert , Buggeroer Arthur B.
Published: October 2005

This presentation illustrates one of the capabilities of a numerical laboratory in the study of acoustic-elastic wave interaction. Because of the simultaneous presence of many modes of vibration, multipath, and mode conversion, physical experiments are difficult to instrument well enough to unravel the wave interactions. As an alternative, numerical results from a 2-D finite difference solution to the elastodynamic equations mimic the physical interaction of a transient acoustic pulse with a finite elastic object. In this case the field variables of velocity and stress are computed directly and instrumentation is not an issue. In the experiment presented here, a 500-Hz center frequency pulse insonifies a submerged steel plate with dimensions ≈2λ × λ/20, where λ is the wavelength in steel. Diffractions from the ends of the plate are observed as well as the flexural and longitudinal plate modes that arise from the coupling of acoustic to elastic energy. In addition, radiation of acoustic energy into the water from the ends of the plate is seen when the flexural and longitudinal modes impact from the interior. A fundamental question of the scattering process is how much of the insonifying acoustic energy is converted into elastic energy in the plate. While the plate modes occur simultaneously and overlap in the time domain, they can be separated into isolated regions of the slowness-time domain. The isolation of the modes in this domain enables estimates of the energy partitioning to be made. From a time series recorded just below the midline of the plate, a slowness spectrum clearly shows the flexural and longitudinal modes in isolation. In addition, the continual reflection of these modes from the ends of the plate, i.e., the multipath, is seen as they travel back and forth. Quantitative estimates of energy partitioning are possible from the slowness spectra.
Application of the reciprocity theorem in the problem of an infinite elastic plate
Authors: Rudgers Anthony J.
Published: October 2005

At the 116th Meeting of the Acoustical Society of America, an equivalent-network representation of an elastic plate was reported [A. J. Rudgers, “Equivalent-network representation of an infinite elastic plate subject to plane-wave excitation,” J. Acoust. Soc. Am. Suppl. 1 84, S184 (1988)]. The circuit equations describing this network are identical to the equations arising from the theory of linear elasticity that describe the two-dimensional elastic behavior of an infinite plate subject to arbitrary plane-wave excitation at its surfaces. It was noted that gyrators are required in the equivalent network, in order to make the network obey the equations of linear elasticity theory. The presence of gyrators in the equivalent network, however, implies that the elastic plate is a nonreciprocal system, with the nonreciprocal effects being associated with elastic mode conversion at the plate surfaces. Because the appearance of nonreciprocal effects in the elastic-plate problem is unexpected and, perhaps, surprising, it is useful to examine the question of reciprocity from a more general standpoint—from a standpoint that does not require one to consider any particular equivalent-network representation of the plate. The present work reports the application of a general version of the reciprocity theorem in the plate problem.
Experimental measurement of structural power flow on L-shaped plates subjected to mechanical and acoustic excitation
Authors: Cuschieri J. M.
Published: October 2005

Analytical results on the structural power flow through an L-shaped plate subjected to mechanical and acoustic excitation have been presented in previous ASA meeting papers. To verify some of these results, experimental measurements have been performed on a similar L-shaped plate as used in the anaytical studies. Two sets of experimental results have been obtained. One set is for simulated results that show the discrepancies created by the selected measurement schemes. The second set of results is for actual measurements that use a four-accelerometer measurement scheme. In the case of the acoustic excitation, measurements were also performed of the acoustic intensity incident and reradiated from the two components of the L-shaped plate. The results of this experimental analysis show that there is good agreement between the measured experimental results, the simulated experimental results, and the analytical results. The accuracy of the measured data as compared to the analytical data is very much influenced by the type of measurement scheme that is selected to perform the measurements. [Work supported by NASA Langley Research Center.]
Vibroacoustic behavior of point-driven and cavity-backed circular plates with general boundary conditions
Authors: Cheng L. , Nicolas J.
Published: October 2005

This paper discusses the vibroacoustic response of point-driven circular plates coupled to a cylindrical hard-walled cavity. Particular attention is paid to the modeling of the boundary conditions of the plates. It is an extension of the previous work [L. Cheng and J. Nicolas, J. Acoust. Soc. Am. Suppl. 1 87, S136–S137 (1990)] in which a circular plate was modeled as part of the structure. The plate is assumed to be elastically supported by rotational and translational springs along the edge. With this model, both classical and intermediate cases can be easily simulated only by making different combinations of the elastic parameters. A variational formulation associated with Rayleigh-Ritz procedure is used for the plate by choosing simple polynomials as trial functions. For the cavity, the Green's function based on cavity modes is adopted. Numerical results are presented to address the following topics: (1) effect of the classical boundary conditions of the plates and its interpretation; (2) consequences of the elastic supporting on the cavity sound field; and (3) some guidelines for the design of such systems in practice.
A new formulation for the sound radiation in a heavy fluid from a rectangular plate with elastic boundary conditions
Authors: Berry A.
Published: October 2005

This paper considers the dynamic response and acoustic radiation of a fluid-loaded, baffled, rectangular plate elastically restrained against deflection and rotation along the four edges. Classical methods using in vacuo plate eigenfunctions to formulate the fluid-structure coupling are essentially limited to the simply supported case, and lead to considerable difficulty, both theoretical and numerical. The proposed approach employs a variational formulation coupled to a Ritz method for the structural motion. Choosing simple polynomials to generate the set of trial displacement functions and expanding the acoustic Green's function of the unbounded fluid medium in MacLaurin series allows an analytic solution for both the resistive part and the reactive part of the radiation impedance. In essence, the method furnishes a decomposition of the radiator in monopoles,dipoles,…,2n-upoles. The analytic solution of the fluid-structure coupling greatly improves the computation costs and generality is gained for the boundary conditions of the plate, as compared to available methods. The convergence of the method is illustrated in the case of simply supported, clamped, free, and guided plates immersed in water. The effect of mass addition and stiffening is also investigated.
Vowel length and pitch in Yavapai
Authors: Thomas Kimberly D.
Published: October 2005

Yavapai has been reported to have three distinctive vowel lengths [Shaterian, unpublished dissertation, 1983]. In order to test this hypothesis, approximately ten tokens from the purported short, long, and extra-long categories were measured using a standard digital spectrograph. Duration measurements showed 100 to 150-ms difference between short, long, and extra long. Analysis of variance (ANOVA) was performed in order to confirm the significance of three phonetic vowel lengths. Pitch contours were measured on the same triplets to determine if one or more of these lengths were predictable from pitch. Contours were represented by measuring the onset, midpoints, and offsets from narrow-band spectrograms. Here, ANOVA confirmed that the pitch contours of short, long, and extra-long length categories did not significantly differ from each other. Syntactic category is thought to play a role in predicting the long length category [Munro, personal communication, 1990]. However, roots involving different syntactic categories have the long length vowels. In such cases, the durations and pitch contours are similar. Thus the data show that the three phonetic lengths cannot be predicted from either pitch or syntactic category.
Attention to spectral and temporal cues in vowel perception among native speakers of Arabic and English
Authors: Munro Murray J.
Published: October 2005

Native speakers of “quantity” languages such as Arabic must learn to attend to duration cues that distinguish certain spectrally similar vowel pairs. It is hypothesized in the present study that native Arabic speakers of English will show an overall greater sensitivity to duration differences between vowels than will speakers of English and they will tend to perceive certain vowel contrasts in their L2 in terms of temporal properties, even when such temporal cues are secondary ones. Results of two perceptual experiments will be discussed. In the first. native English and native Arabic speakers identified a synthetic English beat-bit continuum consisting of six spectral and six durations steps. In the second, the same subjects were trained to identify synthetic exemplars of two French vowel categories, which differed in both quality and duration. Between-, and within-group differences in attention to the two types of cues will be discussed.
The role of F1 amplitude in producing nasal percepts
Authors: Huffman Marie K.
Published: October 2005

A decrease in F1 amplitude is one of the most consistent acoustic consequences of nasal coupling. Despite the consistency of this effect, its importance for the perception of nasality has been given little attention. Listener judgments of the nasality of naturally produced oral and contextually nasalized vowels were evaluated in light of a time-varying analysis of relative F1 amplitude (A1-H1). Both average A1-H1, and change in A1-H1 over time, appear to correlate with nasality judgments. The nasalized vowels sometimes judged as oral were those that had larger A1-H1 values overall, more like those of oral vowels. On the other hand, the oral items sometimes judged as nasal did not have lower overall A1-H1 values; rather, they showed a marked decrease in A1-H1 over the course of the vowel, a pattern that was not observed for the oral items consistently judged as oral. Comparable experiments were designed using synthetic stimuli, which provide a control for pitch, vowel quality, and vowel duration differences that might have been present in the natural speech stimuli. Our results highlight the role of dynamic information in the perception of nasality. [Work supported by NIH.]
Resonance versus source characteristics in perceiving spectral continuity between vowels and consonants
Authors: Kingston John , Diehl Randy , Kluender Keith , Parker Ellen
Published: October 2005

Using nonspeech analogs of VCV sequences modeled as a gap between square waves, Parker et al. [Percept. Psychophys. 39, 129–142 (1986)] showed that pulsing in the gap makes the gap sound shorter. This interaction may underlie the common covariation between closure voicing and closure duration in intervocalic stops. However, the gap duration judgments only depended on pulsing when the analog's F0 fell into and rose out of the gap, implying that to influence perceived gap duration, pulsing must be spectrally continuous with the flanking sounds. Extending this result to speech stimuli is difficult because both F1 and F0 fall into and rise out of voiced stop closures. In the present experiment, the contribution to spectral continuity of independently varying constant, falling-rising and rising-falling F1 and F0 patterns are compared with single formant vowel analogs. These nine spectral patterns flanked gaps varying from 20–120 ms in 10-ms steps. Pulsing produced significantly more short gap judgments when F1 fell and rose, and also produced more short gap judgments when F0 fell and rose, but neither the main effect of F0 nor its interaction with F1 was significant. Spectral continuity between the vowel analogs and pulsing appears to depend more on resonance than source characteristics. [Work supported in part by the College of Arts and Sciences, Cornell University.]
Contextual effects in the perception of naturally produced vowels
Authors: Tajchman Gary N. , Bush Marcia A.
Published: October 2005

Vowels excised from the phonetically and dialectically rich DARPA TIMIT acoustic-phonetic database [L. Lamel et al., Proc., DARPA Speech Recognition Workshop, Rpt. No. SAIC-86/1546, 100–109 (1986)] were presented to listeners in an identification task. The identification data were gathered both to serve as a performance benchmark for a set of automatic speech recognition experiments, and to investigate some of the acoustic and linguistic factors that influence the perception of naturally produced vowels. Vowels were presented to listeners in isolation (i.e., no context), in CVC context and in syllabic context. Differences in percent correct were calculated between no-context and context conditions, where correct was defined as agreement with vowel transcriptions supplied with the TIMIT database. Preliminary analyses of the identification data indicate that: (1) overall improvements in identification accuracy were comparable for both CVC and syllabic contexts (approximately 11%, on average, above the overall no-context identification accuracy of 60%); (2) improvements were approximately four times larger for lax vowels than for tense vowels; and (3) identification consistency among listeners was greater than between listeners and the “correct” phonetic transcription. Acoustic analyses of the vowel tokens that are currently being performed, in order to identify spectral and/or durational attributes that correlate with the identification data.
Cognitive processing in the perception of speech
Authors: Bradlow Ann R. , Kingston John
Published: October 2005

This paper reports on three experiments [J. Ohala and D. Feder, J. Acoust. Soc. Am. Suppl. 1 80, S110 (1986)], designed to show that inferencing occurs commonly in speech perception. This challenges the direct-realist theory [C. A. Fowler, J. Phon. 14, 3–28 (1986)] that claims that speech perception is direct, and not mediated by any cognitive processes. A preliminary experiment showed that the category boundary between [i] and [u] shifts toward [u] next to a bilabial C, and toward [i] next to an alveolar. This boundary shift recurs in V1CV2 stimuli in which the C was masked by white noise. (V1 varies between [i] and [u]; V2 is always [a].) These masked stimuli were presented in blocks where the medial C was always either [b] or [d], which allowed the masked consonant to be “restored” based on the audible consonant in the unmasked stimuli. In the second experiment, 80% of the stimuli in each block had either [b] or [d], and the remaining 20% had the contrasting place. In the third experiment, the 20% minority contained [g]'s. In both cases, the vowel category boundary should exhibit an effect of the place of the 80% “context” stimuli. With [b] or [d], the place of the 20% minority should also effect the [i]-[u] boundary, but [g] should not shift the boundary because listeners would expect [g], unlike [b] and [d], to vary with vowel backness. Preliminary analyses indicate thai expectation participates jointly with direct acoustic analysis in speech perception.
Support for the feature “Expanded”: An MRI analysis of Akan +/−ATR vowel pairs
Authors: Tiede Mark K.
Published: October 2005

The Akan language has a harmony system bifurcating its vowel inventory into two complimentary sets. Previous work by Lindau [J. Phon. 7, 163–176 (1979)] has shown that these sets are distinguished by tongue root position (ATR) and larynx height, and she proposed a feature “Expanded” to characterize the relevant difference in phayrngeal volume. Lindau's measurements were based on cineradiographic tracings of the sagittal midline only; the purpose of the current study was to exploit magnetic resonance imaging to obtain (axial) images of cross sections through the pharynx for vowels in the contrasting vocal tract configurations. Sagittal and axial image data were obtained for three vowel pairs: /i/:/ɪ/,/e/:/ɛ/, and /u/:/ɷ/. Subjects were scanned while phonating continuously with constant pitch and vowel quality, with a recording of the target vowel playing continuously through an earphone. A sound recording was made of vocal output to verify subjects remained on target. The results obtained show that Akan does rely on tongue root advancement and a lowered larynx for the harmony contrast, but also show that pharyngeal lateral width varies systematically as well. This confirms Lindau's observation that pharyngeal volume rather than tongue root position alone is the distinguishing characteristics. [Work supported by NIH Grant DC-00121.]
Modeling air-to-water sound transmission using standard numerical codes of underwater acoustics
Authors: Chapman David M. F. , Ellis Dale D. , Thomson David J.
Published: October 2005

In a recent paper [D. M. F. Chapman and P. D. Ward, J. Acoust. Soc. Am. 87, 601–618 (1990)], it was shown that a normal mode underwater acoustic propagation code can be modified to model air-to-water sound transmission simply by altering the mode excitation coefficients. These new coefficients are the exact wave-theoretic expressions for the air-to-water transmission problem. Herein, it is shown that if the height of the source above the surface is sufficiently small, then the air-to-water transmission problem can be approximated accurately by replacing the source in air with a source in water at a depth d ≪ λ below the surface, where λ is the acoustic wavelength in water. For a distant receiver in water, both the true source in air and the effective source in water exhibit nearly identical dipole radiation patterns. Although the effective directivity of the two sources is the same, the source strength is not. The correct transmission loss due to a source in air can be recovered from the transmission loss computed for a shallow source in water by adding the quantity 20 × log10 (ka d), where k s is the wave number in air. Using this approach, numerical results for three standard underwater acoustic models (normal mode, multipath expansion, parabolic equation) will be compared to benchmark results provided by the SAFARI model for a generic air-to-water transmission example.
Accuracy of the pressure release bottom approximation for normal modes in shallow water
Authors: Rayborn Grayson H. , Barker Barry I. , Ioup George E. , Ioup Juliette W.
Published: October 2005

Previous investigators have recognized that an approximation may be made to the eigenfunctions and eigenvalues for a Pekeris waveguide such that the eigenfuncfions end in a node at an effective pressure release bottom below the actual bottom. A simple graphical derivation of the approximation is presented and the accuracy of the approximation for the marine sediments found to be typical of bottoms along the continental shelf is investigated. For a water column capable of supporting up to 74 modes, the approximation results in errors in the vertical wave number of less than 0.25% for all modes for all bottom types. This modest error indicates that the approximation should be useful in modeling various problems. [Work supported by NOARL and the Navy/ASEE Summer Faculty Fellowship Program.]
The manifestation of transmission and reflection in Hamilton's principal function for rigorous ray tracing
Authors: Floyd Edward R.
Published: October 2005

Hamilton's principal function for rigorous ray tracing is shown to manifest reflection and transmission at a step in a piecewise-constant index of refraction. The first and second derivatives of Hamilton's principal function are continuous across the step. This specifies the generator of the motion, Hamilton's principal function, which is sufficient to describe propagation including the bifurcation of the incoming wave function into the reflected and transmitted wave functions at the step in the index of refraction. This alternative description is consistent with the contemporary description determined by matching the wave function and its first derivative at the step in the index of refraction.
Propagation in a stratified medium with an extension of the circle diagram
Authors: Hudimac Albert A.
Published: October 2005

In previously described work, the circle diagram technique was extended to propagation whose characteristic impedance was approximated by a step-wise variation or was imaginary. This paper describes an extension in which the point impedance is found by solving a generalized Riccati equation. A normalized impedance is used so that one diagram can be applied to a class of variations. The solution is given by two orthogonal families of curves: curves of constant phase and curves of constant standing-wave ratio. The field can be obtained by a simple integration of an associated differential equation. The magnitude of the field can be obtained from a simple algebraic formula for the intensity. A simple solution is obtained for the case of a layer in which the variation of the characteristic impedance is linear; by a simple transformation, the impedance diagram is a bipolar plot. A brief connection between the graphical and analytic methods is made.
Uses of RASTI to assess speech intelligibility
Authors: Lubman David
Published: October 2005

Now an IEC Standard, RASTI provides an objective physical method for assessing speech intelligibility under conditions of steady noise and/or reverberation. Continued growth of the technique's usefulness depends in part on four conditions: (a) users' ingenuity and willingness to find appropriate applications and to share results; (b) instrument manufacturers' ingenuity and willingness to provide new or enhanced features; (c) continued research by speech and hearing scientists extending applicability to new domains; and (d) rapid incorporation into standards. In this spirit the author highlights his experiences consulting with RASTI by discussing six projects undertaken over a 4-year period: (1) a condominium clubhouse whose occupants complained of poor speech intelligibility unhelped by the sound system; (2) a major performing arts center in which RASTI scores were compared before and after changing the sound system in an effort to improve speech intelligibility; (3) SCIF (secret compartmentalized information facility) rooms in which RASTI was used for locating sound leaks, evaluating speech privacy, and setting masking noise levels; (4) headset evaluation; (5) assessment of automobile interior communication; and (6) an electronic countermeasures application rank ordering voice jammer effectiveness.
Signal processing for interferometric fiber sensors
Authors: Kersey Alan D.
Published: October 2005

Interferometric sensors have been shown to be highly sensitive devices for the measurement of a number of physical fields including acoustic pressure, magnetic field, vibration, strain, acceleration, temperature, and rotation. A wide range of “signal processing” techniques for use with fiber interferometers has evolved over the past decade that addresses issues such as passive demodulation, absolute measurand sensing, multiple wavelength interrogation, polarization control, noise reduction, and multiplexing of sensor arrays. This paper will discuss these generic issues as they relate to a broad range of possible application areas for interferometric fiber sensors.
Multimode fiber optic sensors
Authors: Cuomo Frank W. , He Gang
Published: October 2005

A theoretical approach useful in the design of multimode optical fiber sensors is described. An intensity distribution function is derived when assuming that a multimode optical fiber is illuminated by a light source that can be approximated by infinite uniangular beams carrying equal power. The analysis is carried out further to predict sensor response, detection threshold, and dynamic range. Several experiments are discussed to verify the validity of the intensity function as an accurate model in realistic sensor design. In particular, the model is applied to the evaluation of optical fiber lever sensors, such as the optical fiber microphone and underwater acoustic transducers.
Hot topics in acoustical oceanography
Authors: Farmer David M. , Worcester Peter F.
Published: October 2005

The ocean is transparent to sound and nearly opaque to electromagnetic radiation. Remote sensing of processes in the ocean interior therefore depends in large measure on acoustic techniques. Measurements of travel times, Doppler shifts, and intensity fluctuations of probe signals transmitted through the ocean or backscattered from it yield information on ocean temperature and current fields, surface and internal waves, and fauna and other particulates that scatter acoustic signals. The study of acoustic sound generated by natural processes yields information on wind, rain, surface waves, ice, whales and other fauna, and undersea earthquakes and volcanic eruptions. Currently active and exciting research areas include: (i) the study of ocean surface processes using scattered and ambient sound, (ii) acoustic global ocean monitoring of ocean temperature, (iii) Arctic acoustics, including the study of ice dynamics using ambient sound, (iv) acoustic measurement of ocean structure at a variety of scales, and (v) biological acoustics.
Hot topics in physical acoustics
Authors: Bass Henry E.
Published: October 2005

Three general topics continue to present new challenges to the physical acoustics community. The general topics are physical characterization of matter, nonlinear phenomena, and studies of systems far from thermodynamic equilibrium. In this presentation specific examples currently of interest in each of these general areas will be discussed in more detail. (1) Acoustic properties of quasiperiodic structures being studied in one and two dimensions may provide insight into techniques for describing the physical properties of quasicrystals. The discovery of high-temperature superconductors opens an entirely new class of materials for ultrasonic characterization. Ultrasonic studies of both classes of these materials will help understand their behavior at the microscopic level. (2) Nonlinear phenomena have long been studied by people in physical acoustics. In the last decade, the rest of the physics community has discovered nonlinear behavior and has developed numerical treatments of such behavior very rapidly. We now live in a community dominated by philosophical discussions of chaos and the profound significance of the transition to chaos. Acoustic systems provide easily controlled and easily envisioned examples for this emerging science. (3) Studies of thermoacoustic engines have rekindled interest in systems far from thermodynamic equilibrium. The thermoacoustic prime mover provides a ready example of acoustic wave amplification. The significance of these discoveries and developments are only now beginning to emerge. The presentation of “hot” topics in physical acoustics could not be complete without comments on the need for young scientists to pursue the problems discussed to this point. Our community does not now have very effective ways to introduce graduate students and young scientists to these research problems. In the next few years, however, some alternative approaches to educating our replacements will be explored.
Response of an array of hydrophones embedded in an elastomer layer to a modified Corcos turbulent wall pressure spectrum
Authors: Ko Sung H. , Schloemer Howard H.
Published: October 2005

A study was made of a theoretical model for evaluating turbulent boundary layer pressure fluctuations received by an array of rectangular hydrophones embedded in a layer of elastomer. The theoretical model considered in the present study is a plane elastomer layer backed with an infinite plate of finite thickness; the other side of the layer is exposed to turbulent flow. The transmitted flow noise was calculated with an empirically modified model of the Corcos turbulent wall pressure spectrum and was characterized by the frequency spectral density. The results presented here are numerical calculations of flow noise reductions, which are given relative to the noise levels computed for the flush-mounted point hydrophone. Effects of the elastomer layer thickness, the backing plate thickness, the hydrophone dimensions, and the array dimensions on noise reduction are provided.
Problems of representation in computer music
Authors: Moore F. Richard
Published: October 2005

Impressive advances have been made over the past 3 decades in the storage, processing, and synthesis of musical sound. Despite these technological improvements, relatively little has been learned about essential musical processes. Without similar improvement of understanding of musical processes, the potential of this new technology to support advances in the expressive power of music could be wasted on providing equivocal substitutes for traditional instruments. This speculative talk will concentrate on identifying essential unknowns about music with an eye toward developing a musical technology around the notion of their exploration.
Noise exposure from demolition derbies
Authors: Suter Alice H.
Published: October 2005

Today's world of recreation offers a variety of opportunities for noise exposure. Demolition derbies are a popular activity at midwestern county fairs, where afficionados can attend two or three a week during July and August. A survey of three events yielded A-weighted sound levels in the grandstand varying from 60 dB to over 100 dB, depending on the activity and the proximity to the “pit.” Dosimeter readings for a 212-h event showed an Leq of 87 dB(A). Typical durations of these events do not appear to pose significant hearing hazards to members of the audience unless they are also exposed to other noisy hobbies or occupations. The drivers' noise exposures, however, are another matter.
Detection of wind noise artifacts in outdoor noise measurements
Authors: Sneddon Matthew , Silvati Laura , Fidell Sanford
Published: October 2005

Outdoor recordings made in low ambient noise conditions are susceptible to wind noise artifacts associated with turbulence around microphones. Even the use of large windscreens may not always eliminate such artifacts. For certain purposes, such as characterizing nonindigenous noise intrusions in outdoor recreational settings, additional measures are necessary. Signal-processing algorithms for rejecting wind noise artifacts, based on setting simultaneous thresholds for average derivatives in several frequency regions, can be effective in obtaining unbiased estimates of ambient levels.
Relationship of second harmonic absorption coefficient to nonlinear attenuation of the fundamental
Authors: Woodsum Harvey C. , Pridham Roger G.
Published: October 2005

Woodsum [J. Sound Vib. 69, 27–33 (1980)] proposed a method for suppressing the saturation that arises from the distortion of a finite-amplitude wave during propagation. The method is based on the introduction of an agent into the medium that selectively absorbs the second harmonic of the fundamental. While the validity of the proposed method is not in question, the method of analysis used in the original paper was based on numerical solutions of coupled nonlinear equations, which offered no simple intuitive explanation for the effect. Derived here is a simple, intuitive, analytical solution for the amplitude of the fundamental, which supports the previous result and which is valid for a medium having arbitrary dissipation and dispersion properties. The original conclusion is generalized to include saturation reduction via introduction of dispersion as described by Zablotskaya and Soluyan [“A Possible Approach to the Amplification of Sound Waves,” Soy. Phys. Acoust. 13, 254–256 (1967)].
A time domain computer algorithm for solving the KZK equation
Authors: Lee Yang-Sub , Hamilton Mark F.
Published: October 2005

A time domain computer algorithm for solving the KZK (Khokhlov-Zabolotskaya-Kuznetsov) nonlinear parabolic wave equation is being developed for pulsed, axisymmetric, finite-amplitude sound beams. The sound beams may be weakly focused. A coordinate transformation is introduced in the KZK equation [Hamilton et al., J. Acoust. Soc. Am. 78, 202–216 (1985)], and the resulting parabolic equation is integrated once analytically with respect to time. The diffraction and thermoviscous dissipation terms are integrated numerically with implicit backward finite-difference methods, and the Earnshaw solution [Pestorius and Blackstock, J. Acoust. Soc. Am. 53, 383 (1973)] is used to account for the nonlinearity. Weak shock theory may be incorporated in the algorithm. Numerical results for several limiting cases are compared with analytical solutions. Comparisons are also made with numerical results obtained with a frequency domain computer algorithm for solving the KZK equation [see, e.g., Berntsen, in Frontiers of Nonlinear Acoustics—12th ISNA, edited by Hamilton and Blackstock (Elsevier, London, 1990), pp. 191– 196]. [Work supported by the Office of Naval Research and the Texas Advanced Research Program.]
Surface grating contribution to the mixing of reflected ultrasonic beams: Approximate analysis
Authors: Marston Philip L. , Simpson Harry J. , Kargl Steven G.
Published: October 2005

Consider the reflection of a converging vertical ultrasonic beam of frequency f1. The beam is incident from below on a free surface of a liquid and after reflection comes to a focus in the liquid at a distance z below the surface. Now consider the consequences of introducing a second beam of frequency f2≪f1, which is incident at a moderate angle θ with respect to the vertical. It is generally realized that sum and difference frequency waves may be generated from nonlinear interaction in the volume of beam intersection. The present analysis is concerned, however, with a second interaction mechanism: the diffraction of the f1 beam from the traveling surface displacements induced by the reflection of the f2 beam. The displacements are restrained by the liquid's bulk modulus. A quasilinear approximation, analogous to the Raman-Nath approximation for the diffraction light from ultrasonic beams, predicts the formation of focused ± 1 diffraction orders of frequency f1 ± f2. If this grating mechanism is considered alone, the ratio of the ± 1 order amplitude to that of the zero order is approximately p/p0≈J1(s)/J0(s), s≈4|p2|(ρc2)−1(f1/f2)cos θ, where |p2| is the amplitude (in the absence of a surface) of the f2 wave and ρ and c are the density and sound speed of the liquid. If s≪1, then p/p0≈s/2. The foci associated with the ±1 orders are shifted laterally a distance≈z(sin θ)f2/(f1 ± f2). Ordinary volume mixing processes may also produce contributions of similar magnitude. [Work supported by ONR.]
Further remarks on nonlinear second sound in superfluid helium
Authors: Cramer M. S. , Sen R.
Published: October 2005

Second sound waves in the vicinity of the high-temperature zero of the Khalatnikov (quadratic) steepening parameter are considered. The critical role of the dependence of the superfluid density on the counterflow velocity is delineated. Use of a theoretical estimate due to Khalatnikov yields excellent qualitative and quantitative agreement with measured signal speeds.
Waves on fluid-loaded cylindrical shells: Systematic expansions based on full elastodynamic equations
Authors: Pierce Allan D. , Manley Martin G.
Published: October 2005

Further work is reported for the canonical model of an elastic coaxial cylinder, with inner radius R − 12 h and outer radius R + 12 h immersed in a compressible fluid, with the full set of elastodynamic equations, rather than a simplified shell model, used as a starting point for analysis. This dynamical system admits wave solutions of constant angular frequency ω, in which all of the appropriate field variables vary with azimuthal angle φ and axial coordinate x through a common factor eikxxeinφ with n = kyR not necessarily being an integer. One seeks simplified expressions for the dispersion relation F(ω,kx,ky) = 0 and for the polarization relations that determine the ratio of the complex amplitudes of displacements and stresses on the middle surface of the shell, and on the outer and inner surfaces. Systematic exact analytical (not numerical) expansions of the dispersion relations and the polarization relations in powers of parameters (such as h/R) are derived by a procedure that involves use of a computer-assisted symbol manipulation program and concepts of modern algebra. Alternate parameterizations are discussed and explored for incorporation of fluid loading into the expansion scheme, with appropriate assignments of the relative order of magnitudes of dimensionless groups, compared with that of the a priori small h/R. The other groups include, for example, the ratio of the fluid mass per unit area in a slab 1 wavelength thick to the shell mass per unit surface area. The parameterization presumes kxR and kyR are of the order of unity (neither small or large), but makes no initial assumption for the magnitude of the angular frequency. [Work of ADP is supported by ONR and by the William E. Leonhard endowment to Penn State Univ.; work of MGM is supported by the PSU Applied Research Laboratory Exploratory and Foundational Research Program.]
Trills and taps in variation
Authors: Inouye Susan Banner
Published: October 2005

Many of the world's languages have an r sound that is described as a tongue-tip trill. In many cases, the trill is also said to have a tap as a positional variant. However, in other cases, the trill is reported in all positions in a word. Closer examination of descriptions and/or of audio recordings of several languages suggests this universal generalization: The trills always have a tap variant. At least 31 languages all show some variation between a trill and a tap. The generalization holds even for languages in which the trill contrasts with a second r sound. This paper first documents this claim and then considers in more detail whether the trill-tap variation is consistent in two of the languages. Data will be presented from Indonesian (one r phoneme, a trill), and from Palauan (two r phonemes, a trill and a tap), taking into account rate of speech and segmental context. Preliminary data suggest that the tap is most likely in intervocalic position and at fast speaking rates. Furthermore, the trill variant in these conditions has fewer contacts. The implications of this relationship between trills and taps will be discussed.
Acoustic data signaturing using cyclic correlations derived from the Wigher distribution
Authors: Wilbur JoEllen , McDonald Robert J.
Published: October 2005

A hybrid discrete-Wigner distribution/autoregressive moving average (DWD/ARMA) cyclespectrum estimator is developed and applied to signaturing of nonstationary acoustic returns. The ARMA effects a high resolution mapping from the time-frequency Wigner plane to the cyclespectrum. The hybrid estimator is used to characterize cyclic correlations hidden in conventional spectral estimators that prove useful to signal source identification and to signal and noise decomposition. The ARMA performs the high resolution needed in the cycle-frequency domain to characterize the signal source. The autoregressive model provides resolution, inclusion of the moving average into the model reduces noise sensitivity. The results of the hybrid DWD/ARMA cyclespectrum estimator are integrated into the development of a signature identification system and tested on sonar data. [Work supported by a NAVCOASTSYSCEN's Independent Research project sponsored by the ONR.]
Fabrication of near-field calibration arrays
Authors: Tims Allan C. , Young Allan M. , McCleary Alan D.
Published: October 2005

This paper covers the practical aspects of implementing near-field calibration arrays, given a specific set of shading values and array aperture. Methods of selecting and calibrating the active elements are presented, as are shading methods and testing techniques for individual lines and arrays. A special emphasis is given to the recent fabrication of a large near-field array.
Perceptual factor and the use of geminates in Japanese words borrowed from English
Authors: Takagi Naoyuki , Mann Virginia
Published: October 2005

There exists a systematic correspondence between English words of (C1) V1C2({C3/V2}) syllable structure and Japanese loan words when C2 is a voiceless stop. When V1 is + tense, the corresponding Japanese vowel is long and the following consonant is single. When V1 is — tense, the Japanese vowel is short and the consonant is geminate. However, when an optional C3 is a stop, the Japanese consonant is single, and when V2 exists, the Japanese consonant can be either single or geminate. To test the hypothesis that this correspondence has a perceptual basis, 18 native speakers of Japanese were presented with nonsense words (C1 = /g/, V1 = /i,i:, u,u:/, C2 = /p,t,k/, C3 = /s,t/, V2 = /ə/) uttered by two native English speakers. The subjects chose which of four Katakana representations sounded closest to a given stimulus: S(hort)V + S(ingle)C, SV + G(eminate)C, L(ong)V + SC, LV + GC. The results point to a perceptual basis for the orthographic regularity. The correlations between perceptual responses and VD, SD, VD/SD further suggest that the duration of vocalic segments is the most prominent cue for the consonant as well as vowel length judgment.
Bistatic ocean surface scattering strength estimation
Authors: Culver Richard Lee , McDaniel Suzanne T.
Published: October 2005

A computationally straightforward algorithm for computing high-frequency bistatic ocean surface scattering strength has been developed as part of an effort to simulate ocean reverberation for bistatic geometries (transmitter and receiver not collocated). The algorithm implements the Kirchhoff approximation for near specular angles and composite roughness theory for angles away from the specular. The absorption and scattering effects of subsurface bubbles are also modeled [S. T. McDaniel, in Sea Surface Sound (Kluwer, Dordrecht, 1988)]. A parameter controlling the rolloff of the near-specular term is used to determine the transition point for the near-specular to nonspecular term. For high frequencies, the effects of bubbles are found to dominate except for near-specular scatter. Reverberation simulations made using the bistatic surface scattering strength algorithm are compared to high-frequency bistatic reverberation measurements.
The feasibility of using long-range acoustics as a measure of global ocean warming
Authors: Forbes Andrew M. G.
Published: October 2005

The SOFAR channel in the ocean has been known for decades to be an efficient acoustic waveguide. Military applications of long-range acoustic transmissions using the SOFAR channel for communications and detection have been many, but scientific applications that capitalize on its acoustic properties have, until recently, been few. For ranges between source and receiver of order 1000 km, acoustic tomography yields the maximum return of information about both horizontal and vertical ocean structure but this sophisticated technique does not rely on the existence of the sound channel. Over megameter ranges, however, higher acoustic modes are scattered and absorbed so that only the lowest, slowest modes survive as near-axial waves in the sound channel. Following the reinterpretation in 1988 by Munk et al. of data from a long-range acoustic experiment conducted in 1960 (between Perth, Australia and Bermuda), Munk and Forbes (1989) proposed to further develop the technique for use in measuring path-averaged ocean temperatures. They intend to simply measure travel times of lowest mode signals simultaneously along many different megameter paths (refracted geodesics). They predict that, if sufficiently long time-series of such data are gathered, then many different spatial and time scales of ocean temperature variability will be captured and identified. These range from diurnal to decadal scales, including the signature of the often-predicted global warming. A feasibility test of this idea is scheduled for early 1991.