bluuebunny/crossref_metadata_2025 huggingface dataset:
A discrete implementation of a Hankel transform technique for predicting multipole sound propagation over plane, absorbing surfaces
Authors: Hu Z. , Bolton J. S.
Published: October 2005

Many theories are available for predicting sound propagation outdoors; they are usually expressed in terms of sound radiation from a source (e.g., a monopole) that generates a cylindrically symmetric sound field that propagates over a homogeneous, finite impedance plane. However, not all practical noise sources are monopolar in character nor do they necessarily generate azimuthally symmetric sound fields. In this paper, a discrete implementation of a two-dimensional finite Hankel transform technique is described that makes it possible to predict sound propagation from higher-order sources that generate noncylindrically symmetric sound fields: e.g., arbitrarily oriented dipole and quadrupoles. As a result, the proposed technique may prove useful for predicting sound propagation from aerodynamic noise sources place near plane outdoor surfaces. The prediction procedure is based on representing the field of a source as a two-dimensional wave-number spectrum. The wave-number spectrum of the source field is then combined with the reflection coefficient of the impedance plane to yield the wave-number spectrum of the reflected field. The latter component is then added to the direct wave-number spectrum and the result is inverse transformed to give the sound pressure as a function of radius and azimuth angle. Predictions made using the new technique will be compared with experimental results.
Underwater acoustic measurement facilities at NRL/USRD
Authors: Van Buren A. L. , Blue J. E.
Published: October 2005

At the beginning of World War II, the United States recognized the need for establishing systematic methods for calibrating and evaluating sonar transducers and established the Underwater Sound Reference Laboratories. The Underwater Sound Reference Detachment of the Naval Research Laboratory evolved from this beginning and now serves as the focus for underwater acoustic metrology in the United States. It functions as a ‘‘National Bureau of Standards for Underwater Acoustics’’ by providing two types of reference services for a fee. Calibration, test, and evaluation services and standard transducer loan services cover the frequency range of 0.2 Hz to 2 MHz. This paper covers the measurement facilities for carrying out the metrology function and the measurement methods for setting the primary standards and the loan standards. Evaluation of sonar transducers and some of the ongoing research in calibration measurement methodology is also discussed. Finally, some comments are made about calibration system requirements for implementing new measurement techniques.
Fourth-order cumulants and spectra of acoustic data
Authors: Dwyer Roger F.
Published: October 2005

In a recent paper [Dwyer, J. Acoust. Soc. Am. 90, 918–926 (1991)] properties of the Fourier transform of a special case of the fourth-order cumulant were discussed and the results of a transmit–receive experiment presented. The data from this experiment have now been analyzed for more general cases of the fourth-order cumulant and its corresponding spectrum. The paper reviews theoretical properties of fourth-order cumulants and spectra, discusses applications in underwater acoustics, and presents results from acoustical experiments and simulations.
The performance of artificial neural networks in classifying acoustic signatures
Authors: DeMetz Fred C.
Published: October 2005

The performance of feedforward networks employing the backward propagating delta rule for error correction have been tested utilizing simulated acoustic target signatures and noise. The network correct classification and false alarm rates were studied for varying size and composition of the training sets. The effects of signal-to-noise ratio, and fluctuations in the amplitude and frequency of the signal data were also investigated. The practicality of utilizing networks in multistage sonar processors is assessed from the standpoint of normally available training set size, composition, and quality.
Investigating the structure of bowed-string transients by systematic simulation
Authors: Woodhouse James , Schumacher Robert T.
Published: October 2005

Lothar Cremer had a life-long interest in the acoustics of the violin. Growing from Cremer’s work, an efficient simulation algorithm for bowed-string transient motions was developed some 15 years ago and applied to elucidate some of the oscillation regimes the system can support. Work is now in progress to use this algorithm in a more systematic way, to seek physical correlates of the perception that one instrument, or one particular note, is ‘‘easier to play’’ than another. This perception presumably has its origin in the fact that sometimes the required oscillation regime is easy to establish from a wide range of bowing transients, while in other cases a small error of bowing may elicit a different, undesirable, oscillation regime. Using 16 384 parallel processors of a Connection Machine, two-dimensional parameter subspaces are scanned, and pictures produced to show which starting conditions produce the violinist’s required regime, and how long the initial transient is. The effects of varying parameters of the physical model may then be seen. Starting from a simple model due to Cremer, effects of string stiffness, string torsion, and violin body resonances have been studied.
Acoustically cued countermeasures taken by insects in response to predatory bats that hunt with biosonar
Authors: Hoy Ronald R.
Published: October 2005

Insectivorous bats detect and hunt down their prey by means of ultrasonic biosonar signals and some insects have evolved ultrasound-sensitive ears to detect bats and to take evasive action. This has been known since the early 1960s, largely due to the pioneering work of K. D. Roeder, who documented the interactions between bats and moths, that hear ultrasound. Since then, studies of the auditory behavior of insects have revealed that ultrasound hearing has evolved in at least five orders of nocturnally active, flying insects and it is suspected that it serves to detect the biosonar signals of bats. In spite of the taxonomic diversity (unrelatedness) of these insects, all insects that hear ultrasound have evolved a tympanal hearing organ with particular and characteristic ‘‘design features’’ in their structure and function. When some of these insects are stimulated with ultrasound during tethered flight, they exhibit short latency startle responses that appear to be escape behavior, ranging from directional steering to cessation of wingbeat. It is clear that the predatory relationship between bats and their insect prey has resulted in the evolution of evasive behavior in insects, made possible by the evolution of a hearing organ sensitive to ultrasound.
Phonotaxis in crickets: Investigations of the mechanisms of acoustic signal recognition and localization
Authors: Doherty John A.
Published: October 2005

Cricket phonotaxis behavior provides a useful model system for understanding underlying neural processes of sound temporal pattern recognition and localization. It is assumed that both sound recognition and localization has occurred when a female cricket undergoes phonotaxis towards a singing male. Phonotactic tracking by the female cricket can be turned on or off by altering certain temporal components of the male calling song. Synthetic song playback experiments demonstrate that some temporal components are more important than others in eliciting phonotaxis behavior. In several cricket species that produce continuous trills or repeating four-pulse chirps, sound pulse repetition rate is of primary importance. The effects that other temporal properties have on phonotaxis sometimes are evident only when the pulse rate is made less ‘‘attractive’’ by moving its value outside of its natural range. Some of these other relevant temporal properties include pulse duration, chirp repetition rate, and pulse and chirp duty cycles. Neurophysiological studies have identified some of the neural correlates to these behavioral results. It is not known how the processes of sound recognition and localization are interrelated in the auditory nervous system. Behavioral studies are currently underway to determine the roles of different calling song temporal properties in these processes.
Acoustic and laryngographic measurements of primate vocalizations
Authors: Brown Charles H. , Brown Fritz E. , Santos K. Leigh , Dagenais Paul A.
Published: October 2005

Simultaneous acoustic and laryngographic recordings were made of 176 blue monkey (Cercopithecusmitis) vocalizations. Four classes of periodic vocalizations were identified. In class I calls the rate of phonation ranged from 547 to 1211 Hz. The acoustic output of class I calls was harmonically related to the rate of phonation and ranged from approximately 1 to 9 kHz. Class II signals exhibited a reduced amplitude in the Lx signal consistent with the loft register of phonation. The rate of phonation of class II calls ranged from 1289 to 2177 Hz. The acoustic spectrum of these tonal signals was composed of harmonically related bands. The frequency of the lowest band equaled the frequency of phonation. Class III calls exhibited attributes in the Lx wave that were consistent with the idea of different surfaces of the vocal folds vibrating at different rates. In some calls the putative low-frequency source oscillated at about 850 Hz, and the putative high-frequency source oscillated at about 4200 Hz. The fourth class of signals resembled class I calls except that the signal was emitted as a series of pulses or trills. [Work supported by NIDCD.]
Absolute and relative pitch perception by a bottlenose dolphin (T.truncatus)
Authors: Ralston James V. , Gage Kathryn F. , Harris Jeffrey G. , Brooks Sean P. , Herman Louis M.
Published: October 2005

It was previously reported [Ralston etal., J. Acoust. Soc. Am. Suppl. 1 84, S77 (1988)] that a dolphin appeared to perceive relative pitch in sequences of four pure tones. At any point in those studies, all stimuli were pitch transpositions of one of two contours. The dolphin generally whistled after presentation of one contour and remained silent after presentation of the other contour. Recent analyses have examined whistle probability, whistle latency, and whistle duration as a function of the absolute pitch of stimuli. Generally, as the absolute pitch of the stimuli increased, the probability of whistling increased and the whistle latency decreased. The combined results suggest that the dolphin judged both the absolute and relative pitch of the stimuli. Consistent with Ridgway etal. [J. Acoust. Soc. Am. 89, 1967 (A) (1991)], the present results also suggest that whistle responses provide a sensitive index of perceptual processing and are an appropriate modality in choice response paradigms with dolphins.
Aliasing and sampling criteria for higher-order correlations
Authors: Pflug Lisa A. , Ioup George E. , Ioup Juliette W.
Published: October 2005

While sampling data at a Nyquist frequency equal to the highest frequency present in the data (critical sampling) is sufficient to prevent aliasing in both the data and the discrete-time autocorrelation calculated from the data of a bandlimited energy signal, the sampling requirements for the avoidance of aliasing in higher-order correlations are not necessarily the same. They depend on whether one samples the continuous-time autobicorrelation or autotricorrelation directly, for which critical sampling is sufficient, or whether these quantities are calculated from sampled data, in which case it is not. For the latter, the sampling interval for the autobicorrelation must be no greater than two-thirds the interval associated with critical sampling, and no greater than one-half for the autotricorrelation. Numerical calculations of autobicorrelation and autotricorrelation zero-lag values corresponding to spectral area and volume, as well as bispectral contour plots, for example, bandlimited deterministic signals, are presented as illustrations. Spectral and convolutional masking filters which remove aliasing in higher-order correlations calculated from critically sampled data are presented. Differences in frequency content for rectified signals and in aliasing for autocorrelations sampled directly or calculated from sampled data are also discussed. [Work supported by ONR/NRL-SSC.]
Two-dimensional cross correlation of reverberation data
Authors: Canales L. , Harris J. , Yoerger E. J. , Caruthers J. W.
Published: October 2005

A technique of time stretching time-series data is applied to reverberation time sequences beamformed from a multielement horizontal receiving array. For different, but nearby, array locations, beams that are scattered off a common area should be highly correlated. The correction method applied here maps each beamformed time series such that common scatterers coincide in position on a 2-D grid. The method uses an average pilot signal and 2-D cross correlations to stretch the time series in a way similar to static corrections in surface seismic processing. This process requires multiple iterations and the average pilot signal is recalculated between iterations. This method was applied to the aforementioned data from five different array locations using an average pilot signal. The results showed a high degree of correlation among the time series. The results are compared with available bathymetry to determine if scattering events can be matched with bottom features. [Work supported by ONR.]
Multichannel deconvolution through simulated annealing
Authors: Smith James F. , Finette Steven
Published: October 2005

A deconvolution algorithm based on simulated annealing has been developed that allows the extraction of the source time series from passively sensed multichannel data measured on an array. The algorithm is general, different cost functions and annealing schedules can be easily implemented allowing various environmental conditions to be treated in an optimal fashion. The algorithm is intrinsically parallel, fast, and requires no assumptions about the initial form of the source time series. The intrinsic parallelism of the algorithm allows an excellent compromise to be reached between stability of the solution and rate of convergence of the simulated annealing process. Tests using simulated data constructed by convolving a known signal with a theoretical Green’s function and then adding Gaussian white noise have been conducted. Excellent reconstructions of the source time series have been achieved for cases of high and low signal-to-noise ratio. This methodology is being tested on deep ocean data obtained in a multipath environment. Results from simulations and experimental data will be discussed. [Work supported by ONR and NRL.]
Facilities and underwater test capabilities at the Naval Surface Warfare Center, Dahlgren Division Detachment, Fort Lauderdale (NSWCFLDET)
Authors: Bond Anthony D.
Published: October 2005

The Detachment controls an underwater test site extending from shore to a water depth of 2000 ft. Using a dedicated range support vessel and remotely operated underwater recovery vehicle known as TONGS, the Facility maintains an underwater field of cables and acoustic instrumentation. The cable field consists of coaxial, multiconductor, and fiberoptic cables terminating in water depths from 60 to 1800 ft. Attached to cable ends are acoustic ranging systems for active underwater target tracking, acoustic beacons, acoustic projectors, array test sites, and volumetric arrays for experiments in passive target tracking. Additional cable sites are maintained to test acoustic systems for other range users. Improvements to the Facility have been made as a result of more stringent accuracy requirements. New generation, three-dimensional, acoustic tracking arrays provide more accurate tracking data against submerged targets. Precision sonar systems and computer positioning interface on TONGS allows precise determination of bottom unit positions even in deep water. New telemetry gear enables high data rate transmission of acoustic information.
Causality analysis in broadband feedforward controlled systems
Authors: Burdisso R. A. , Vipperman J. E. , Fuller C. R.
Published: October 2005

In recent years, adaptive feedforward control algorithms have been successfully implemented to attenuate the response of systems under persistent inputs, such as single and multiple tones and random signals. System causality is not an issue when the excitation is sinusoidal because of its deterministic nature. However, causality is a very important factor in broadband control. Although significant deterioration in the performance of acausal control systems have been reported in the literature, analytical tools are virtually nonexistent to predict the behavior of broadband controllers. The main objective of this research is to develop an approach to investigate system causality. A formulation is presented to address the effectiveness of a control configuration as a function of the filter size, delay time, and dynamic properties of the structure. The technique is illustrated in a simple numerical example and the results are also corroborated experimentally. [Work supported by Office of Naval Research.]
The active control of point acoustic sources in a half-space
Authors: Cunefare Kenneth A. , Shepard Steve
Published: October 2005

Analytical analyses of active noise control applications generally neglect the presence of nearby reflective surfaces, such as a ground plane. This paper examines the impact of the presence of a nearby reflective plane on the active control of sound radiated by a number of point sources. It is shown that when the sources to be controlled are within one wavelength of the reflective plane, be it rigid or pressure release, that the plane can significantly impact the control versus control under free-field conditions and with the same source separations. The orientation of the noise sources and the control sources with respect to each other and to the plane also significantly influences the control. For sources more than one wavelength away from the reflective plane, the use of the simpler free-space analysis yields acceptable results as compared to using the more complex half-space analysis.
A simulation study of the relation between vocal tract movement and energy changes in restricted frequency bands
Authors: Wu Y. , Porter R. J. , Trahan R. E. , Riemer T. E.
Published: October 2005

A four-tube model of the vocal tract was used to investigate the relationship between systematic variations in tube-segment diameter and changes in energy within different frequency regions. The hypothesized near linear relation between changes in displacement and changes in energy was observed for some frequency regions. This result suggests that tracking of energy changes within select frequency bands might provide rather direct information on the kinematics (and, perhaps, the kinetics) of the articulators. Implications of the result for the evaluation of articulatory abnormalities as well as for theories of speech perception will be discussed.
Quantitative characterization of vowel formant transitions
Authors: Talley Jim
Published: October 2005

This paper presents an acoustic study of vowel formant dynamics and the analysis methods that were developed to carry it out. The main goal of the described study was to bring quantitative, acoustic evidence to bear on competing theories regarding the source(s) of vowel identity specification [W. Strange, J. Acoust. Soc. Am. 85, 2081–2087 (1989)]. A set of 40 CVC syllables are studied: symmetric voiced stop (/bVb/, /dVd/, /gVg/) and ‘‘neutral’’ (/hVd/) contexts × the ‘‘monopthongal’’ vowels of Midwestern American English (/i,i,e,eh,æ,Λ,u,u,o,a/). Three male speakers (speaking normally) contributed two repetitions each. Voice pulse by voice pulse tracks of the first three formant frequencies were measured using GEMS [J. Talley, J. Acoust. Soc. Am. 90, 2274 (A) (1991)] and LPC. PEACC, a new technique for speech coding using exponential pieces, was then applied to the trajectories to automatically segment them into transitions and characterize the segments in terms of intuitive parameters−Δf (‘‘locus-to-target’’ distance), Δt (duration), α (curvature), and f0 (‘‘target’’ frequency). This paper discusses the resulting data’s characteristics and the results from analyzing initial and final transitions with respect to intracategory similarity and intercategory distinctiveness using a variety of interesting category boundaries. [Work supported by NSF.]
A cross-linguistic validation of locus equations: Are there ‘‘phonetic hot spots’’ in CV acoustic space?
Authors: Sussman Harvey M. , Ahmed Farhan , Hoemeke Katherine
Published: October 2005

A previous study [Sussman etal., J. Acoust. Soc. Am. 90, 1309–1325 (1991)] of American English CV coarticulation showed a remarkably linear relationship between onset frequencies of F2 transitions (plotted along the ordinate) in relation to midvowel target frequencies (plotted along the abscissa) in CVC tokens with initial /bdg/ followed by ten medial vowels. Slope and y intercept of regression functions (‘‘locus equations’’) fitted to these coordinates systematically varied as a function of stop place. Discriminant analyses, using as predictor variables, slope and y intercept, yielded 100% correct classification of stop place categories. Locus equations provide a systematic lawfulness to coarticulatory variation and a relationally invariant phonetic index for stop place classification. The present study extends the metric to three additional languages−Thai, Cairean Arabic, and Urdu. Resulting scatterplots were extremely linear and varied as a function of stop place. Plotting slope Xy intercept yields a derived map of CV phonetic space with which to relationally compare 2, 3, and 4-stop place languages. Within-language stop place contrasts were consistly divergent in CV space. Variability of labial, alveolar/dental, and velar coordinates across five languages showed fairly broad clustering of stop place categories, rather than narrowly focused ‘‘phonetic hot spots.’’ The data are discussed in relation to quantal and adaptive dispersion theories. [Work supported by NSF.]
Evidence for bistability in the region of perceptual boundaries
Authors: Case Pamela , Tuller Betty , Kelso J. A. S. , Ding Mingzhou
Published: October 2005

Examples of the nonlinear relationship between acoustics and speech perception abound in the literature, most notably in the investigations of categorical perception. However, the dynamics of this relationship have been virtually ignored. In previous work, it has been reported that systematic variation of a single acoustic parameter in an identification task revealed evidence of signature properties of nonlinear dynamical systems including hysteresis effects and bistability [Tuller etal., J. Acoust. Soc. Am. 89, 1997 (A) (1991)]. In the present work, the relative stability of the alternative percepts is explored by manipulating the number of stimulus repetitions. Near the perceptual boundary, an increased number of stimulus repetitions maximized the frequency of observed spontaneous changes in perception. This suggests that perceptual change with sequential variation of an acoustic parameter results from loss of stability of the original percept. Thus perceptual dynamics, not solely acoustic stimulus information, determines perception of speech categories. [Work supported by NIDCD and NIMH.]
Effect of token variability on discrimination between vowel sounds II
Authors: Ronan D. E. , Uchanski R. M. , Braida L. D.
Published: October 2005

Uchanski etal. [J. Acoust. Soc. Am. 90, 2254 (A) (1991)] reported significant sensitivity differences between discrimination experiments in which each vowel was represented by only four tokens (utterances) and experiments in which the same four tokens were embedded in a larger set of 16 tokens. In present experiments, the set size was fixed at 8 but the specific tokens representing one vowel were changed while those representing the other vowel were fixed. Listeners attempted to discriminate between the vowels /ae/ and /ah/ occurring in distorted [M. R. Schroeder, J. Acoust. Soc. Am. 44, 1735–1736 (1968)] /h/–V–/d/ syllables. Sensitivity was found to be more highly correlated (ρ≊0.8) across conditions for a given subject than across subjects for a given condition (ρ≊0.5). This suggests that each subject weighted the available discrimination cues in a fairly stable fashion across conditions, but that the weights varied from subject to subject. Multiple regression analyses indicate that sensitivity can be accounted for by a small set of physical parameters of the undistorted syllables: F2, F0, and syllable duration.
Some observations of women’s and children’s F2 frequencies: anatomical considerations and coarticulatory effects
Authors: Nittrouer Susan , McGowan Richard S.
Published: October 2005

One controversy concerning children’s speech is whether they coarticulate more, less, or about the same as adults. A confounding factor in studies addressing this issue is that vocal tract morphology varies with age and sex: Ratios of pharyngeal to oral cavity length are smallest for children, largest for men, and intermediate for women. Consequently, differences among men’s, women’s, and children’s F2s should be greater for front unrounded than for back unrounded vowels [G. Fant, SpeechSoundsandFeatures (1973)]. Pharyngeal and oral cavity lengths and F2s for /i/ and /ɑ / at vowel center of CV syllables were compared for women and 3-year-olds, with men serving as a reference. Results showed that children’s F2s did not differ from those of women as much as would be predicted based on anatomical considerations. This finding was used to evaluate the magnitude of children’s anticipatory coarticulation. It was found that F2s of children’s /i/ and /ɑ / differed more from those of women at voicing onset than at vowel center, suggesting that children were coarticulating more. Two other findings supported this conclusion: (1) Ratios of F2i to F2ɑ were more similar for children at voicing onset and at vowel center than they were for women at these two locations; and (2) ratios of F2 at voicing onset to F2 at vowel center for a given vowel were closer to 1.00 for children than for women. [Work supported by NIH.]
Navajo vowels and universal phonetic tendencies
Authors: McDonough Joyce , Ladefoged Peter , George Helen
Published: October 2005

Navajo is one of the comparatively few languages in the world in which there are said to be four vowel qualities, [i,e,ɑ ,o]. Data from nine speakers of Navajo show that when the vowels are represented in terms of their formant frequencies, they are not approximately equidistant as predicted by Lindblom’s dispersion hypothesis, in that [i] and [e] are too close together. What is also not predicted by this hypothesis is that the vowel [o] has a greater variance than the other vowels. There are two possible reasons for the greater variance of back vowels. On the one hand, considering the vowel space as a triangle, the high back corner could be less sharp than the high front or low back corners, allowing high back vowels to be in various locations that are all well dispersed from [ɑ ] and [i]. On the other hand, high back vowels could be less well defined in articulatory-acoustic terms; [i] and [ɑ ] are more in accord with Stevens’ quantal hypothesis in that they have vocal tract shapes that can be somewhat varied while two formants remain close together, but there is no obvious high back quantal vowel.
Active structural acoustic control of cylinder radiation with piezoelectric actuators and PVDF sensors
Authors: Clark Robert L. , Fuller Chris R.
Published: October 2005

An aluminum cylinder, measuring 1.22 m long with a wall thickness of 2.77 mm and a diameter of 0.254 m, was configured with two rigid end caps and instrumented with piezoceramic actuators and polyvinylidene fluoride (PVDF) sensors for narrow-band active structural acoustic control. All tests were performed in an anechoic environment. In the first test case, the cylinder was driven with a shaker on one end cap, exciting the ‘‘accordion mode’’ of the structure. Significant levels of sound radiation (90 dB) from the end caps were observed in this mode of vibration and the piezoceramic actuators were more than sufficient for controlling the structural acoustic response, yielding 35 dB of global attenuation. In the second test case, the cylinder was driven radially to excite the (0,1) mode of the cylinder as well as higher-order modes to demonstrate the capability of the piezoceramic actuators for controlling the structural acoustic response of the ‘‘breathing mode’’ as well as higher-order cylinder modes. Results from this preliminary study suggest that piezoceramic actuators and PVDF sensors are viable transducers for creating an adaptive/sensory structure for active structural acoustic control on cylinders. [Work supported by ONR.]
Output nonlinearities of cochlear hair cells can account for the diversity of rate-intensity functions of mammalian auditory-nerve afferents
Authors: Chatterjee Monita , Zwislocki Jozef J.
Published: October 2005

Rate intensity (RI) functions of afferent auditory-nerve fibers of mammals are known to depend on frequency deviations from the fibers’ best frequencies (BFs) and also on their BF thresholds. The functions become flatter as either the frequency is increased from below BF to above BF or the fibers’ thresholds increase. In the latter case, the functions cover an extended range of SPLs. It is shown empirically that both relationships can be accounted for by two kinds of nonlinearity found in the alternating receptor potentials of the hair cells, in particular, inner hair cells (IHCs), one producing amplitude compression, the other, a lowering of BF as SPL is increased. Past models of fiber RI functions seem to have relied on the first nonlinearity. The second nonlinearity suggests that, at a given cochlear location, fibers with relatively high thresholds have lower BFs than fibers with relatively low thresholds, and that the hard saturation of the latters’ RI functions may have a cochlear origin. [Work supported by NIDCD and DiCarlo Fellowship.]
Intervocalic stop consonant representation in the chinchilla auditory nerve
Authors: Narayan S. Shyamla , Beehler Donna J. , Sinex Donal G.
Published: October 2005

The representation of intervocalic voiced and voiceless stop consonants in the chinchilla auditory nerve was studied. Acoustic characteristics of intervocalic stop consonants differ from those of stops in other positions. The stimuli (/ita/, /ida/, /uta/, and /uda/ as spoken by male and female talkers) were presented at 30 and 60 dB SPL. At both stimulus levels, discharge rates of most neurons decreased during the consonant closures. For the voiceless consonant /t/, discharge rates usually decreased to the spontaneous rates. For the voiced consonant /d/, the low-frequency neurons continued to respond to the ‘‘voice bar’’ during closure. At 60 dB SPL, the release for all sounds elicited increases in the discharge rates of the higher CF neurons. At 30 dB SPL, the release did not elicit rate increases above the rate during closure in any CF region. At both stimulus levels, the onset of voicing after the release nearly always elicited discharge rate increases. Neurons with CFs below 2 kHz were most likely to respond to voicing. [Work supported by DC00341 to DGS.]
Cochlear noise damage: Empirical evidence for the origin of the ‘‘half-octave shift’’
Authors: Zwislocki Jozef J. , Zhang Minsheng
Published: October 2005

The phenomenon of ‘‘half-octave shift’’ between the frequency of the damaging sound and the frequency of the greatest sensitivity loss, whether measured behaviorally or neurally, is well known. A more detailed analysis of the data suggests that, for small to moderate losses, the greatest morphological damage corresponds to a shift of about one octave and that the shift of maximum sensitivity loss tends to be smaller. It is now possible to account for these relationships on the basis of intensity series of hair cell transfer functions obtained before and immediately after exposure to damaging noise. Before exposure, the response maximum gradually moves toward lower frequencies, as SPL is increased. After exposure, it is shifted toward lower frequencies even at relatively low SPLs, and its dependence on SPL is reduced, both effects becoming more prominent with increasing sensitivity loss. In the presence of severe loss, the shift reaches one octave, and its dependence on SPL is abolished altogether. [Work supported by NIDCD.]
Sources of variability in the ear’s response to impulse noise
Authors: Price G. Richard
Published: October 2005

It is commonly observed in impulse noise experiments that hearing loss data are highly variable. The explanation implicitly accepted is that the ear is just inherently variable at very high sound pressures. However, calculations of hazard with a mathematical model of the ear [G. R. Price and J. T. Kalb, J. Acoust. Soc. Am. 90, 219–227 (1991)] indicate that the details of pressure histories of the impulses themselves may be the source of much of the variability. The model calculates the transfer of energy from the free field to displacements of the basilar membrane. ‘‘Hazard’’ is modeled as the sum of the peaks of upward displacement of the basilar membrane (in microns) raised to the 2.5 power. Weapons impulses (105-mm howitzer) with the same peak pressures and highly similar pressure histories (which would be rated as equally hazardous by traditional damage-risk criteria) nevertheless produced hazard calculations that varied by a factor of 2 or 3 in a completely deterministic ‘‘ear.’’
Dynamics of self-interaction of two spontaneous otoacoustic emissions suppressed by a pulsed external tone
Authors: Murphy W. J. , Tubis A. , Talmadge C. L.
Published: October 2005

The level of a spontaneous otoacoustic emission (SOAE) during recovery from suppression by an external tone sometimes exhibits a prominent overshoot before settling down to its natural value. This overshoot may be explained in terms of the suppression of the SOAE by a neighboring higher frequency emission which is slowly recovering from suppression by the external tone. This phenomena has been investigated using a pulsed suppressor tone (Talmadge etal., 1990) and averaging the amplitude envelopes of the emission for successive presentations of the suppressor. One simple version of the dynamics involves a Van der Pol oscillator with an effective external tone of the form, Λ(1−e−Γt)cos(ωt). This form simulates the recovery from suppression of the higher frequency SOAE. This model has been used to extract from the data estimates of the time constants for the recovery from suppression of an emission that exhibits the overshoot phenomena. More elaborate models involving the coupling of two Van der Pol oscillators (e.g., Wit, 1990) are also considered.
On using dispersion characteristics to actively control transient broadband signals
Authors: Dimitriadis Emilios K. , McCoy John J.
Published: October 2005

Most current transient signal control techniques are based on system identification and subsequent control of a discrete model. Estimation uncertainties, and also modal coupling via excitation, control, or damping determine the limits of successful control. The alternative suggested here, is based on apriori obtaining the ‘‘effective’’ dispersion characteristics of a chosen wave-propagation path. The dispersion induced by a complex waveguide may be determined by measuring a broadband pulse at the intended control-sensor and control-actuator locations. The technique of windowed Fourier transform is employed to deduce the ‘‘effective’’ dispersion curve(s) for said path. In a control situation, the sensed transient is computationally propagated in time-frequency space to the control location. The controller subsequently alters the time-frequency impedance characteristics of the control location to optimally achieve the desired control objectives. Numerical experiments are here described for two different beam structures. Laboratory experiments are suggested and their implementation discussed. Finally, issues of structural discontinuities, wave-mode conversion, and, very importantly, computational speed requirements are addressed.
Wave-number analysis of active structural acoustic control of sound transmission through a panel
Authors: Mathur Gopal P. , Tran Boi N.
Published: October 2005

Active control of sound transmission through elastic structures, such as panels using structural inputs, has received considerable attention in recent years. The active control technique of improving structural transmission loss (TL) by applying control forces directly to the transmitting structure using single or multiple piezoelectric actuators mounted on the structure rather than using acoustic canceling sources is known as active structural acoustic control (ASAC) method. This paper presents results of experimental investigations of ASAC method in improving the TL of a panel. Wave-number analysis was employed to understand the mechanism of improving the TL of a panel using multiple piezoceramic actuators. Experiments were conducted to measure near-field sound radiation from a baffled panel (dimensions: 1.75 m×1.14 m×1.27 mm) subjected to acoustic excitation for both with and without active control conditions. The active control of the panel TL was achieved by four piezoceramic actuators mounted on the panel. An array of four microphones placed about 1 m away from the panel were used as error transducers for a multiple-input multiple-output active control system. The transmitted acoustic field was measured by a two-dimensional array of microphones (array size: 22×14). The wave-number frequency spectra of the sound field were obtained by implementing Fourier transforms on the spatial domain data. Sound intensity measurements were also made to determine improvements in panel transmission loss.

Comparison of measured wave-number spectrum for the active control condition with that of baseline (without control) showed that sound radiation from the acoustically fast lower-order modes at low wave numbers is significantly reduced. Results from the near-field acoustical holographic measurements will also be discussed. The relative reduction in sound power levels due to ASAC estimated from the near-field holographic measurements compared very well with those obtained from sound intensity measurements.
New formulation of the fast field programs for anisotropic sound propagation through a windy atmosphere above ground
Authors: White Michael J. , Li Y. L.
Published: October 2005

Two new fast field programs (FFP) have been developed for numerical computation of anisotropic sound propagation through a windy atmosphere above ground. The first new FFP can be used to compute the near- and far-field sound pressures and use a two-dimensional fast Fourier transform with iterative refinement. The second new FFP is based on a far-field approximation requiring only a one-dimensional transform. For typical values of wind speed, this new expression shows that the component of wind perpendicular to the direction of propagation has little or no effect on propagation. However, for sound propagating into or with the wind, the wind should be treated as a flow, rather than as a perturbation on the intrinsic sound speed. The differences between the effective sound-speed model and the wind flow model appear as phase errors for high angle modes. In cases of ducted propagation with very few modes, the differences in levels are most significant. When many modes contribute to the level, the phase errors in the high angle modes are not as important and the effective sound-speed model is fairly accurate.
Methods of allowing for linear gradients within fast field layers
Authors: Taherzadeh Shahram , Attenborough Keith
Published: October 2005

At large ranges or at higher frequencies, it is necessary to incorporate a large number of isovelocity layers to achieve tolerable accuracy in fast field calculations. This has a predictable effect on computation time. There is a standard solution in terms of Airy functions that allows for a linear gradient within each layer. This paper presents a preliminary investigation of an alternative form of solution that involves Hankel functions of complex order. These arise from a transformation of the depth-separated wave equation into a form of Bessel’s differential equation. Results have been obtained for a low-frequency case and are compared with results from the standard form in terms of Airy functions.
Changing roles in the cochlea: Bandpass filtering by the organ of Corti and additive amplification on the basilar membrane
Authors: Goldstein Julius L.
Published: October 2005

The classical role of the basilar membrane in cochlear sound analysis is being reassessed on the basis of quantitative models of cochlear nonlinear responses and biophysical evidence for tonotopically organized tuning by outer hair cells. It is hypothesized that the primary function of cochlear bandpass filtering is performed by the organ of Corti, whose nonlinear responses to stapes signals are collected by the basilar membrane. Bilateral nonlinear signal processing characteristics for the organ-of-Corti filters are quantified with a new feedback reconfiguration of the multiple-bandpass nonlinearity (MBPNL) model [J. Goldstein, Hear. Res. 49, 39–60 (1990)]. The basilar membrane is modeled classically, but its role is hypothesized to be analogous to the transmission-line collector of a distributed amplifier. Traveling waves on the basilar membrane provide a means for coherent addition of responses to a given tone from different organ-of-Corti filters. Computations with the model using biophysical knowledge of the density of outer hair cells and the tonotopic map yield a maximum distributed gain of 43 dB, which agrees with known data. Bilateral nonlinear transduction in the cochlear model is responsible for an I/O response versus level for tones that compresses at much lower sound levels than the isolated organ-of-Corti filter, also consistent with data. These results encourage further modeling research with our working hypothesis that redefines the roles of basilar membrane and organ of Corti in cochlear function. [Work supported by NIDCD Grant No. DC00737.]
Structural acoustic laboratories at NRL in Washington, DC
Authors: Houston B. H.
Published: October 2005

The Physical Acoustics Branch at NRL operates three main laboratories in its prosecution of structural acoustics and related experimental programs. These laboratories serve as the Navy’s principle experimental capability for conducting small scale scattering and radiation studies in water; they are also used for developing advanced sensor technologies such as interferometric fiber optic strain sensors and for conducting some large scale studies. The most recent of these capabilities to come about is NRL’s new LSA (Laboratory for Structural Acoustics) which has several unique features. The heart of this new lab is a one-million-gallon, vibration isolated, temperature-controlled cylindrical tank. It is equipped with two in-water robotic scanners that possess 1-mil repeatability over their 14-×8-×8-ft work spaces, thus allowing for the acquisition of highly precise near-field holographic scattering and radiation data. The NRL laboratories are also equipped with state-of-the-art line and planar sources that allow for the uniform ensonification of test structures, as well as with near-field projection codes for reconstructing surface pressures, normal components of velocity, and far-field information. All laboratories are fully networked and supported by physically independent data acquisition systems that are rigorously maintained to uniform hardware and software standards.
Lecture demonstrations in acoustics
Authors: Atchley Anthony , Keolian Robert , Bolen Lee , Crum Lawrence , Korman Murray , Kuhl Patricia , West James , Blassengame Robin , Campbell Nicole , Dunn Brien , Gordon Sharla , Thomas Timothy , Walker Kim
Published: October 2005

A series of lecture demonstrations in acoustics will be given to students from various levels of the New Orleans School System. Attendance and participation by members of the Society are welcome.
Simple demonstrations with tuning forks
Authors: Rossing Thomas D. , Russell Daniel A.
Published: October 2005

Several old [Lord Rayleigh, Philos. Mag. 13, 316–333 (1907)] and new [Rossing etal., Am. J. Phys. 60, 620–626 (1992)] demonstration experiments using tuning forks are illustrated. These include nonlinear motion of the stem, radiation of the second harmonic, effect of a baffle, and the behavior of bent and loaded forks.
Complex adaptive systems in music
Authors: Rosenboom David
Published: October 2005

Ways of producing, controlling, and understanding the perception of complexity−particularly as a reflection of natural evolution−is very important in contemporary music composition and is a continuous thread in the author’s works. A series of generative models for composition based on characteristics of complex adaptive systems are surveyed. These focus on the creation and organization of musical units in formal, hierarchical structures. Often, these structures contain enfolded shapes or patterns exhibiting properties of self-similarity. Of primary importance in these dynamical models is feedback from either presumed or measured processes in perceptual organization. Various parameter space portraits of their resulting behavior may contain differentiations or separations resembling those of chaotic attractors. Some of the phenomena discussed include: catastrophic bifurcations in perception during continuous transformation of patterns or shapes; pattern attractors in rhythmic organization; iterative transformation with shaping functions producing controlled complexity and enfolded self-similarity; self-organization and spontaneous generation of musical forms; and speculations on the implications of algorithmic information measures for understanding the perception of musical complexity.
An investigation of fractal sounds and their musical implications
Authors: Gionfriddo Thomas A. , Heinz Brett , Celmer Robert D.
Published: October 2005

Just as there are fractals in the visual realm, there can be fractal waveforms produced in the acoustic domain. An investigation based on Schroeder’s work [J. Audio Eng. Soc. 37, 795 (1987)], sought to digitally generate waveforms using the Weierstrass function (time domain), as well as the Fibonacci, Golden Mean, and other spectra constructed with constant frequency ratios. Subsequent perceptual studies of these fractal sounds exhibited unusual pitch trends as a result of musical transposition. The implications of the seemingly paradoxical pitch changes in light of the waveform’s self-similarities will be discussed and demonstrated.
The Seneca Lake sonar test facility, Dresden, NY
Authors: Carlton Lynn F. , Elias Nelson
Published: October 2005

The Seneca Lake sonar test facility at Dresden, NY, is a field station of the Naval Undersea Warfare Center, Division Newport, RI, headquartered in Washington, DC. Open year-round, the facility business is to test and evaluate single-element hydrophones and transducers up to large complex sonar arrays and systems. The work at the station supports major Navy laboratories, universities, and civilian contractor programs requiring underwater measurements to water depths of 150 m, fixed geometry ranges to 3.8 km, and load handling requirements to 220 tons. A description of the land base, vessel complement, and barge facilities is given. Several small and large scale programs that have used the facility are discussed in detail to illustrate the station capabilities. An in-depth discussion is made of the modern measurement systems and ancillary mechanical and electrical equipment permanently available at the facility for project support. Chronic logistic, technical, and operational problems with appropriate solutions are presented.