bluuebunny/crossref_metadata_2025 huggingface dataset:
Depth-shifting of shallow water guide source observations
Authors: Zurk Lisa M. , Tracey Brian H.
Published: October 2005

In theory, matched field processing offers the significant benefit of higher signal gains and increased localization capability. However, this has not been robustly observed in practice because of inherent uncertainties about details of the shallow water propagation environments which limit the prediction of the channel response. The use of guide sources to directly measure the transfer function between source and receiver arrays has been proposed as a means for reducing mismatch. However, the guide source measurement only provides a measured transfer function at the guide source location. In this paper a method of depth-shifting guide source observations is proposed, making it possible to estimate transfer functions for points in the ocean other than the guide source location. The proposed depth-shifting process does not require knowledge of environmental parameters. The theoretical background for the technique is developed below and its range of applicability is examined
Modifications of the equation for gas bubble dynamics in a soft elastic medium
Authors: Zabolotskaya Evgenia A. , Ilinskii Yurii A. , Meegan G. Douglas , Hamilton Mark F.
Published: October 2005

A model equation for the oscillation of a pressurized gas bubble in a nonlinear incompressible elastic medium [Emelianov et al., J. Acoust. Soc. Am. 115, 581 (2004)] is extended to include effects of surface tension, viscosity, weak compressibility, and confinement by an elastic shell. The significance of this work is that starting from first principles, the full nonlinearity of the incompressible elastic medium surrounding the bubble and forming its shell is taken into account. Measurements of equilibrium radius as a function of external pressure for a gas bubble in a tissue-like gel are also presented. A general approach to including hysteresis is also discussed.
Vibroacoustics of three-dimensional drum silencer
Authors: Huang Lixi , Choy Y. S.
Published: October 2005

When a segment of a rigid duct wall is replaced by a membrane and is backed by a cavity, incident noise induces membrane vibrations and causes noise reflection. The reflection is effective over a broad band in the low-frequency region when a certain high tension is applied on the membrane in the axial direction of the duct. The device is thus called a drumlike silencer. The existing vibroacoustic theory is based on a two-dimensional duct model and the membrane is reduced to a one-dimensional string. This study extends the theory to three dimensions for the duct and two dimensions for the membrane which has all four edges fixed. It is shown, analytically, that the lateral tension is always detrimental to the silencing performance. However, the optimal performance of the one-dimensional string is recovered exactly when the lateral tension on the two-dimensional membrane vanishes despite the very different boundary conditions. The conclusion is validated experimentally, paving the way for the application of the drum silencer in which the cavity is completely separated from the gas flow in the duct.
Synthetic aperture time-reversal communications in shallow water: Experimental demonstration at sea
Authors: Higley W. J. , Roux Philippe , Kuperman W. A. , Hodgkiss W. S. , Song H. C. , Akal T. , Stevenson Mark
Published: October 2005

Time reversal has been shown as an effective way to focus in both time and space. The temporal focusing properties have been used extensively in underwater acoustics communications. Typical time-reversal communication experiments use vertical transducer arrays both to increase the signal-to-noise ratio and decrease the temporal sidelobes created in the time reversal process. Comparable temporal focusing is achieved using a horizontal array. In this paper, synthetic aperture time-reversal communications are accomplished, requiring only two transducers (one transmitter and one receiver). Deriving results from an at-sea experiment, this work confirms the viability of synthetic aperture time-reversal communications.
Dispersion-reducing finite elements for transient acoustics
Authors: Yue Bin , Guddati Murthy N.
Published: October 2005

This paper focuses on increasing the accuracy of low-order (four-node quadrilateral) finite elements for the transient analysis of wave propagation. Modified integration rules, originally proposed for time-harmonic problems, provide the basis for the proposed technique. The modified integration rules shift the integration points to locations away from the conventional Gauss or Gauss-Lobatto integration points with the goal of reducing the discretization errors, specifically the dispersion error. Presented here is an extension of the idea to time-dependent analysis using implicit as well as explicit time-stepping schemes. The locations of the stiffness integration points remain unchanged from those in time-harmonic case. On the other hand, the locations of the integration points for the mass matrix depend on the time-stepping scheme and the step size. Furthermore, the central difference method needs to be modified from its conventional form to facilitate fully explicit computation. The superior performance of the proposed algorithms is illustrated with the help of several numerical examples.
Bulk ablation of soft tissue with intense ultrasound: Modeling and experiments
Authors: Mast T. Douglas , Makin Inder Raj S. , Faidi Waseem , Runk Megan M. , Barthe Peter G. , Slayton Michael H.
Published: October 2005

Methods for the bulk ablation of soft tissue using intense ultrasound, with potential applications in the thermal treatment of focal tumors, are presented. An approximate analytic model for bulk ablation predicts the progress of ablation based on tissue properties, spatially averaged ultrasonic heat deposition, and perfusion. The approximate model allows the prediction of threshold acoustic powers required for ablation in vivo as well as the comparison of cases with different starting temperatures and perfusion characteristics, such as typical in vivo and ex vivo experiments. In a full three-dimensional numerical model, heat deposition from array transducers is computed using the Fresnel approximation and heat transfer in tissue is computed by finite differences, accounting for heating changes caused by boiling and thermal dose-dependent absorption. Similar ablation trends due to perfusion effects are predicted by both the simple analytic model and the full numerical model. Comparisons with experimental results show the efficacy of both models in predicting tissue ablation effects. Phenomena illustrated by the simulations and experiments include power thresholds for in vivo ablation, differences between in vivo and ex vivo lesioning for comparable source conditions, the effect of tissue boiling and absorption changes on ablation depth, and the performance of a continuous rotational scanning method suitable for interstitial bulk ablation of soft tissue.
Multichannel time-reversal processing for acoustic communications in a highly reverberant environment
Authors: Candy James V. , Poggio Andrew J. , Chambers David H. , Guidry Brian L. , Robbins Christopher L. , Kent Claudia A.
Published: October 2005

The development of time-reversal (T/R) communication systems is a recent signal processing research area dominated by applying T/R techniques to communicate in hostile environments. The fundamental concept is based on time-reversing the impulse response or Green’s function characterizing the uncertain communications channel to mitigate deleterious dispersion and multipath effects. In this paper, we extend point-to-point to array-to-point communications by first establishing the basic theory to define and solve the underlying multichannel communications problem and then developing various realizations of the resulting T/R receivers. We show that not only do these receivers perform well in a hostile environment, but they also can be implemented with a “1bit” analog-to-digital converter design structure. We validate these results by performing proof-of-principle acoustic communications experiments in air. It is shown that the resulting T/R receivers are capable of extracting the transmitted coded sequence from noisy microphone array measurements with zero-bit error.
Tracking individual fish from a moving platform using a split-beam transducer
Authors: Handegard Nils Olav , Patel Ruben , Hjellvik Vidar
Published: October 2005

Tracking of individual fish targets using a split-beam echosounder is a common method for investigating fish behavior. When mounted on a floating platform like a ship or a buoy, the transducer movement often complicates the process. This paper presents a framework for tracking single targets from such a platform. A filter based on the correlated fish movements between pings is developed to estimate the platform movement, and an extended Kalman filter is used to combine the split-beam measurements and the platform-position estimates. Different methods for gating and data association are implemented and tested with respect to data-association errors, using manually tracked data from a free-floating buoy as a reference. The data association was improved by utilizing the estimated velocity for each track to predict the location of the next observation. The data association was more robust when estimates of platform tilt/roll were used. Other techniques to estimate position and velocity, like linear regression and smoothing splines, were implemented and tested on a simulated data set. The platform-state estimation improved the estimates for methods like the Kalman filter and a smoothing spline with cross validation, but not for robust methods like linear regression and smoothing spline with a fixed degree of smoothing.
Further observations concerning anoxia sensitive negative endolymphatic potentials (EP)
Authors: Kobayashi T. , Marcus D. C. , Thalmann R.
Published: October 2005

It has previously been shown in the guinea pig that the negativity of the cochlear, utricular, and ampullar EP induced by systemic or perilymphatic application of the “loop” diuretic ethacrynic acid (EA) is sharply reduced by ischemia or other types of anoxia. In the cochlea the same phenomenon has been observed with furosemide (FU) and bumetanide (BU). Recently Bosher [J. Physiol. 293, 329 (1979)] reported that he could not detect the anoxia sensitive negative EP following application of EA in the rat. In a systematic series of experiments we have found that this potential is present to a comparable degree in rat and guinea pig, following both systemic and perilymphatic application of EA. The same phenomenon is elicited in the rat by FU, BU, and piretanide. Moreover the potential is present in chinchilla and dog. The anoxia sensitive negative EP thus appears to be a generalized response to “loop” diuretics in mammals. Recently an analogous potential was observed in intoxication with iodoacetic acid [Kobayashi et al., J. Acoust. Soc. Am. Suppl. 1 70, S28 (1981)]. Possible mechanisms involved in the generation of these potentials are discussed. [Supported by NIH.]
Response of an edge-supported circular membrane electret earphone
Authors: Busch-Vishniac Ilene J.
Published: October 2005

In the simplest model of an earphone, sound pressures are generated at the eardrum by adiabatic changes of the volume of air in the ear cavity. In capacitance earphones these volumetric changes result from the dynamic motion of the earphone diaphragm. In the treatment presented here the dynamic behavior of an edge-supported, circular membrane electret earphone is studied analytically in a two-step procedure. First, a general series solution for the static deformation of a foil electret suspended over a backplate is determined. It is possible to determine a stability criterion for the system, which if not met, results in collapse of the foil onto the backplate. Second, a series solution for the dynamic deflection is determined. The dynamic deflection may be divided into a linear response and a distortion response. Both depend on the static deflection. With this analysis it is possible to predict and optimize the response of an edge-supported circular electret earphone.
Experimental constant beamwidth transducer
Authors: Luker L. Dwight , Van Buren A. L. , Jevnager M. D. , Tims A. C.
Published: October 2005

The theory of a broadband constant beamwidth transducer (CBT) which is based on Legendre function shading of a spherical cap was described in a previous report [P. H. Rogers and A. L. Van Buren, J. Acoust. Soc. Am. 64, 38–43 (1968)]. Theoretical calculations showed the CBT to have uniform acoustic loading, extremely low sidelobes, virtually no nearfield, an essentially constant beam pattern for all frequencies above a certain cutoff frequency, and a flat transmitting current response over a broad band for piezoelectric drive. In this paper we present experimental results obtained for a prototype CBT based on fifth-order Legendre function shading. The transducer is a spherical cap with a diameter of 30.5 cm and a total cap angle of 50 degrees. The spherical cap is an aluminum plate in which 849 lead zirconate-titanate disks, 0.635 cm in diameter and 0.318 cm thick, are arranged in 16 circular bands with each disk isolated from the plate by corprene. Measurements on the CBT showed it to possess very low sidelobes and a nearly constant beamwidth over the frequency range from 20 to 140 kHz and for ambient pressures up to 3.4 MPa.
Shallow-water acoustic research at the Naval Research Laboratory
Authors: Ingenito F. , Wolf S. N.
Published: October 2005

This paper reviews shallow-water acoustic research performed by the Naval Research Laboratory during the past ten years. The earlier work concentrated on acoustic propagation modeling and measurements. Major achievements were the development of techniques to measure the excitation, depth distribution, and attenuation of individual normal modes and successful comparison of the measurements with theoretical predictions. This work culminated in a tested propagation loss model capable of representing the complex conditions characteristic of the shallow-water environment. More recently, a model of wind-generated noise based on the transmission loss model has been developed. This model predicts relative level and spatial coherence of the noise field. The experimental program has been expanded to include measurements of signal coherence, ambient noise level and coherence, and array gain. Examples of these measurements and comparisons with predictions will be presented.
Broadband sound propagation in shallow water
Authors: Akal T. , Jensen F. B.
Published: October 2005

A review of ten years of research in shallow water acoustics at SACLANTCEN is presented. Both experimental and theoretical results are given, with general features of shallow water propagation being emphasized. The experimental basis for this study is an extensive set of shallow water propagation data collected in different coastal areas of the Mediterranean Sea and the eastern North Atlantic. These data, in turn, have been subjected to a comprehensive modeling effort using wave-theory models (normal mode and parabolic equation) in order to identify the fundamental mechanisms governing sound propagation in shallow water. As a result of this model/data comparison we have obtained a better understanding of the complicated frequency-dependent changes in propagation conditions with changing environment, i.e., sound-speed profile, water depth, bottom type, etc. Propagation levels in shallow water are generally found to be highly dependent on bottom type. In particular the coupling of sound into shear waves in the bottom is found to be an important low-frequency loss mechanism. It is also shown that the optimum frequency of propagation in shallow water is strongly dependent on water depth but less dependent on bottom type. This phenomenon will be dealt with in some detail.
Stress and rate effects on articulation
Authors: Tuller B. , Harris K. S. , Kelso J. A. Scott
Published: October 2005

Previous theorizing in speech production has considered variations in syllable stress and speaking rate to be identical transformations of motor activity (e.g., Lindblom, 1963). More recent work, however, suggests that modulations of stress and rate have different acoustic and perceptual effects, and thus may have independent “signatures” in production. The experiments reported here examined these hypotheses. In the first experiment, electromyographic activity from three muscles primarily related to vowel production was examined during utterances whose stress and rate characteristics were systematically varied. The second experiment addressed the same basic question but examined simultaneous electromyographic activity, and movement of the lower lip and jaw. [Work supported by NINCDS and BRSG.]
Prosody and the /š/-/č/ distinction
Authors: Price P. J. , Levitt A. G.
Published: October 2005

Dechovitz [J. Acoust. Soc. Am. Suppl. 1 69, S115 (1981)] has claimed that a silence which cues the /š/-/č/ distinction in many contexts, fails to do so when it coincides with certain syntactic boundaries. We repeated Dechovitz's experiment with a set of four sentences, using four durations of silence, and two prosodic patterns. These sentences were produced by three techniques: cross-splicing of naturally produced utterances, concatenation of nonsense syllables, and synthesis-by-rule. As expected, we found a strong phonetic effect of silence duration in all conditions. For the synthetic condition, we also found a strong effect of the prosodic pattern of the last syllable before the silence. The concatenated syllable condition showed a trend in this direction as well. We found no evidence of a syntactic effect in any of our data. The prosodic effects are, on the other hand, strong and suggest further research into ways by which prosody may help the listener in parsing. [Work supported by NIH.]
Road noise, texture, and skid resistance
Authors: Lokken Edwin C.
Published: October 2005

A major dilemma facing highway engineers and designers is in providing a balance between traffic noise and highway safety. Amount of skid-resistant texture applied to the pavement is a major influence on surface noise level. With concrete pavement, texture consists of shallow transverse grooves. Transverse-textured concrete may be noisier than random-textured bituminous surfacing for any given texture depth. However, the concrete surface is more effective in maintaining high-speed skid resistance. Studies conducted in England show that a single linear relationship exists between tire noise level and effectiveness of texture in terms of change in BFC (braking force coefficient), a measure of skidding resistance. For the same level of skid resistance, a bituminous surfacing with 2.0-mm texture depth emits the same level of noise as concrete surfacing with 0.8-mm texture depth. It is thus possible to specify separate texture depths for concrete and bituminous surfaces with the knowledge that not only are they equivalent in terms of road safety, but also that each will emit roughly equal tire noise levels.
Mechanism of the sharp vibration maximum without wave reflection in the cochlea
Authors: Zwislocki J. J.
Published: October 2005

The recently discovered sharp vibration maximum of the basilar membrane at the best frequency is difficult to reconcile with the reflectionless traveling wave that is implied by the empirical data. Theory based on the long-wave approximation and corresponding numerical computations show that wave reflection should take place. The apparent paradox is resolved by representing the cochlea as a transmission line and investigating its characteristic impedance. The appropriate differential equation has been derived previously (Zwislocki, 1953). It is valid for all wavelengths found in the cochlea. The investigation reveals that, in the presence of sufficiently short waves prevailing around the vibration maximum, the characteristic impedance remains practically constant. It is independent of the rapid variation of the impedance of the basilar membrane. Since wave reflection depends on variation of the characteristic impedance, no wave reflection should be expected. The constancy of the characteristic impedance also strongly enhances the vibration maximum, so that the amplitude increases as the square of the amplitude expected from longwave theory. [J. Zwislocki, “Wave motion in the cochlea caused by bone conduction,” J. Acoust. Soc. Am. 25, 986–989 (1953)]. [Work supported by NIH.]
An active model for sharp tuning and high sensitivity in cochlear mechanics
Authors: Neely Stephen T. , Kim D. O.
Published: October 2005

Some recent in vivo measurements of cochlear-partition motion [Sellick et al., J. Acoust. Soc. Am. (in press); Khanna and Leonard, Science (in press)] indicate that when physiological disturbance to the cochlea is minimized, basilar-membrane displacement shows very high sensitivity and sharp tuning similar to that of single cochlear nerve fibers. We have developed an active model of cochlear mechanics which simulates this sharp tuning and high sensitivity; each point of the partition is represented in our model by a linear fourth-order mechanical system which includes a negative damping component as a local source of mechanical energy. The model is solved in the time domain numerically, using a finite-difference method. The solution is stable in the sense that all transient responses decay with time. Basilar-membrane displacement of the model shows excellent agreement with the sharp tuning of single cochlear nerve fibers and the high sensitivity of recent in vivo measurements of basilar-membrane displacement. With changes in the parameter values of the model affecting the internal energy release, the model also simulates the vulnerability of the sharp tuning and high sensitivity of basilar-membrane motion. The performance of our active model should help establish the presence of a similar active mechanism in the cochlea. [Work supported by NIH grants.]
Determination of cochlear receptor potential characteristics by pseudorandom noise
Authors: Dallos Peter , Santos-Sacchi Joseph , Lutz William
Published: October 2005

We have utilized computer-generated ternary M sequences of the inverse repeat type [C. Swerup, Biol. Cybern. 29, 97–104 (1978)] for measuring the amplitude and phase characteristics of various cochlear potentials. Recordings were made from guinea pig cochleas. Recording sites included scala media, various locations within the fluid spaces of the organ of Corti, inner sulcus, supporting cells of the organ of Corti, and both inner and outer hair cells. Frequency response characteristics at various stimulus levels obtained with noise stimuli are compared with those derived from tone-burst responses. It is demonstrated that the response properties are well represented by results obtained with pseudorandom noise stimulation. [Work supported by NINCDS.]
Room acoustics for the hearing impaired
Authors: Plomp R. , Duquesnoy A. J.
Published: October 2005

Experiments have shown [A. J. Duquesnoy and R. Plomp, J. Acoust. Soc. Am. 68, 537–544 (1980)] that the Speech Transmission Index (STI), derived from the modulation transfer function, can be used to describe the combined effect of noise and reverberation on speech intelligibility by hearing-impaired subjects. Every 3-dB hearing loss for speech in noise (elevation of the speech-reception threshold in terms of S/N ratio re speech-reception threshold for normal-hearing subjects) can be compensated for by an increase of 0.1 in STI. For an auditorium or classroom, this increase can be obtained by reducing the reverberation time with not less than 58%. Since many hearing-impaired subjects have hearing losses. for speech in noise larger than 3 dB, we may conclude that they need very low reverberation times.
The development of the outer- and middle-ear system
Authors: Saunders James C. , Kaltenbach James A.
Published: October 2005

The developmental changes in interaural distance, pinna size, and ear-canal dimensions will be noted in a variety of species. The contribution of these changes to sound diffraction about the head interaural distance and ear canal resonance will then be explored. We will suggest that the acoustic properties of the neonatal outer ear exert an influence on sound input to the TM at frequencies substantially higher than that found in the adult. Consequently, the outer-ear system in the very young neonate may contribute only minimally to hearing ability. The late stages of development in the middle-ear conductive apparatus show wide variations among species, but within a given species there is remarkable synchrony in the maturation of the ossicles, TM, middle-ear muscles, and the tympanic cavity. Evidence of functional middle-ear development will be summarized from human, hamster, and chick. We will consider the idea that middle-ear maturation plays a significant role in determining many of the patterns of development seen in more central regions of the auditory system. [Work supported by the Deafness Research Foundation.]
Determining speech intelligibility in industrial environments
Authors: Powell John G. , Sutherland Louis C.
Published: October 2005

Application of the speech transmission index to determination of speech intelligibility in indoor industrial environments is described. Equations suitable for engineering use are presented. The effects of reverberation in the direct field of the speech source are accounted for. Presbycusis effects are included in the equations, allowing, for example, calculation of the source level required for 95% of the 40-year-olds to attain 97% speech intelligibility. The effects of high ambient noise and hearing protection devices are also described. Effective room volume is required in the calculation. In a building cluttered with machinery, pipes, etc., the effective volume may be a fraction of the physical volume, or one or more of the classical six surfaces may be missing. A practical method of measuring effective volume is described.
Sensitivity of predicted effectiveness of a paging system to design criteria
Authors: Sutherland Louis C. , Glaretas Constantine , Powell John G.
Published: October 2005

The expected effectiveness of an industrial paging system for presentation of emergency messages has been evaluated in terms of sentence intelligibility (SI). The evaluation was based on the Speech Transmission Index concept developed by Houtgast and Steeneken [J. Acoust. Soc. Am. 67, 318–326 (1980)]. Changes in SI were evaluated for 17 paging system locations with nominal signal-to-noise ratios ranging from −21 to +15 dB and reverberation times ranging from 0.3 to 1.6 s. The change in signal level required to achieve a design goal of 90% and 97% SI was evaluated as a function of (1) the average age of the listeners (30 or 40 years), (2) the percentage (50% or 90%) of this age group who would achieve the desired SI, and (3) the number of message repetitions. The primary result is to point out that the influence on required signal level of message repetitions was found to be at least as important as the other factors. This influence is not included in the usual engineering methods for evaluating communication systems. Conflicts between alternate prediction models for the effect of message repetition according to current signal detection theory and earlier experimental work are considered.
Voicing effect on vowel duration is not an absolute universal
Authors: Mitleb Fares
Published: October 2005

A familiar model of the linguistic analysis of speech tends to describe speech in terms of the segment units of phonetic transcription under the assumption that nondiscrete physical properties of speech can be derived from the discrete elements by universal rules of performance. Thus it is widely accepted that vowels are universally longer before voiced consonants than before voiceless ones; for example, in English tab and tap, the vowel is obviously longer in the first. A spectrographic test of Arabic minimal pairs by eight Arabs, however, revealed that Arabic did not exhibit a difference in vowel duration as a function of the segmental “voicing” feature. Yet to further support this finding another spectrographic test of English minimal pairs spoken by eight Arabs revealed that they had considerable difficulty learning the novel temporal implementation for the English “voicing” feature. These results disprove the assumption of current linguistic analysis that nondiscrete physical properties of speech sounds are “supplied by universal rules” that speakers do not need to learn. Instead we propose that nonsegmental differences exist between the temporal structures of languages that must be accounted for in the linguistic analysis of each language and must, apparently, be learned by second language learners to sound like speakers of the target language. [Research supported by Yarmouk University.]
Speakers' ability to control vocal tract output: I. Phrase-level utterance duration
Authors: Weismer Gary , Cariski Denise
Published: October 2005

The aim of this line of research is to gain a better understanding of the kinds of control speakers can bring to bear on various types of vocal tract output. In the present studies, the ability of speakers to “control” phrase-level utterance durations is explored under a variety of conditions. Speakers are asked to reproduce utterance durations with reference to (1) a self-generated model (that is, an internal standard) and (2) an external model; within this variable of model type, utterance length is varied. Central tendency and dispersion characteristics of total utterance durations as well as within-phrase segment durations are examined and evaluated relative to hypotheses derived from the general motor behavior literature. [Work supported by NIH Program Project NS 13274.]
Spectral spread of high-frequency surface reverberation
Authors: McDaniel Suzanne T.
Published: October 2005

In an earlier paper [S. T. McDaniel and A. D. Gorman, J. Acoust. Soc. Am. Suppl. 1 69, S70 (1981)] it was shown that high-frequency surface reverberation was due to the presence of a layer of subsurface bubbles. In this paper, expressions are obtained that directly relate the spectral spread of the scattered signals to the ocean waveheight frequency spectrum. For frequencies above 20 kHz, the spectra are found to be Gaussian. A normalized spectral spreading width is defined, and its dependence on oceanographic and systems parameters is discussed. A comparison with representative acoustical data confirms the theoretical predictions. [Work supported by ONR.]
Numerical technique to simulate time dependence of a scattered wavefield in a region of correlated but nonstationary scatterers
Authors: Larry T. L.
Published: October 2005

First-order acoustic scattering from a nonstationary distribution of scatterers has been simulated in the form of a complex basebanded time sequence. First- and second-order statistics of the medium are used to produce realizations of the scattered wavefield. Contributions from different points are explicitly correlated. Statistical studies on the time sequences can be related to the spatial correlations of the scatterers.
Noise control for offshore drilling facility
Authors: Ying S. P. , Boyd R. T.
Published: October 2005

A detail noise survey was conducted on a large offshore oil rig with three drilling machines. The coherence function technique was used to identify noise sources in the equipment rooms, the control room, the radio room, the offices and the crew's living quarters. It was found that the major noise sources were diesel engine generators, mud pumps, air conditioners, ventilation systems, etc. The structure-borne noises which were generated by engine generators and air conditioners propagated into the control room, the radio room, the offices and the living quarters through steel structures. Because this offshore facility will be operated in the North Sea, the noise levels should comply with the United Kingdom Department of Energy Guidance. Noise control recommendations were provided for the above mentioned areas and the work place on the drilling floor where the noise levels exceeded the criteria specified in the UK DOE's Guidance. The recommendation included the installation of vibration isolaters and silencers for the noise sources. These were successfully implemented. Acoustical treatments of a few special areas were suggested for further noise reduction.
Community noise exposure guide for large wind turbine systems
Authors: Hubbard H. H. , Stephens D. G. , Shepherd K. P.
Published: October 2005

Procedures are described for evaluating human exposure to wind turbine noise. They are based on noise and noised induced vibrations at the receiver location and make use of results of recent full scale noise measurements and of laboratory studies of human response to wind turbine noise; as well as information contained in the available literature on noise induced house vibrations and noise propagation in the atmosphere. The findings are believed to apply to the design and sitting of future large wind turbine systems as well as for assessing the noise environment of existing systems. [Work supported by the NASA-Lewis Research Center and the Department of Energy.]
Annoyance caused by propeller airplane flyover noise
Authors: McCurdy David A. , Powell Clemans A.
Published: October 2005

Two laboratory experiments were conducted to examine the annoyance response of people to the noise of propeller airplane flyovers and to assess potential method of quantifying that annoyance. In each experiment, 64 subjects judged the annoyance of recordings of propeller and jet airplane operations presented at D-weighted sound pressure levels of 70, 80, and 90 dB in a testing room which simulates the outdoor acoustic environment. The first experiment examined 11 propeller airplanes with maximum takeoff weights greater than or equal to 5700 kg. The second experiment examined 14 propeller airplanes weighing 5700 kg or less. Five jet airplanes were included in each experiment. Perceived noise level predicted annoyance better than A-, D-, or E-weighted sound pressure level. Corrections for tones greater than or equal to 500 Hz generally improved prediction ability for the heavier propeller airplanes. Tone corrections generally degraded prediction ability for the light propeller airplanes. Duration corrections improved prediction ability for the heavier propeller airplanes and degraded prediction ability for the light propeller airplanes. The effect on prediction ability of critical band corrections to perceived noise level varied.
Variation of B/A with 1/c for several liquids
Authors: Hagelberg M. Paul
Published: October 2005

In a recent paper [B. Hartmann, J. Acoust. Soc. Am. 65, 1392ndash;1396 (1979)] a thermodynamic-molecular model is provided for the roughly straight line relationship between the nonlinearity parameter (B/A) and the inverse sound velocity (1/c) known as Ballou's rule. When B/A is studied as a function of 1/c for a given liquid, by varying pressure and/or temperature, a straight line relationship is found in most cases. Results will be presented for several normal liquids as well as for water which, while it is anomalous as expected, proves especially interesting.
Synaptogenesis and first coding in the developing cochlea
Authors: Pujol Remy
Published: October 2005

The development of synapses clearly differentiates the two kinds of cochlear receptors: Inner (IHC) and outer (OHC) hair cells. An adultlike pattern of innervation can be seen very early below the IHCs: Both afferent and efferent (mainly axodendritic) synapses are formed before the onset of function. At the OHC level, drastic changes occur: Numerous afferent dendrites retract as the large efferent endings arrive and synapse with the hair cell. This synaptic OHC remodeling coincides with maturation of compound action potential (AP) parameters, such as the “S” shape of the input-output curves and the sharpening of AP tuning curves. Two major points can be emphasized from these findings. First, ontogeny brings other evidence for two separate efferent systems. The one maturing first is mainly connected with afferent dendrites issuing from the IHCs and is probably responsible for the inhibitory effect on the AP, which can be observed as soon as the first AP can be recorded. The other efferent system matures slowly and synapses mainly with the OHCs. This leads to the second point about the timing coincidence which tends to link the late development of the OHCs and their efferent synapses with the maturation of discriminative physiological properties of the cochlea.
Functional development within the cochlear nuclei
Authors: Brugge John F.
Published: October 2005

The auditory system continues to develop well into postnatal life. In the cat, the discharge properties of neurons in the cochlear nuclei, the first synaptic stations in the auditory pathway, undergo marked changes during the first few postnatal weeks when these structures, as well as those peripheral to them, are completing their morphologic development. The structural changes in these parts of the auditory pathway are accompanied by changes in neuronal threshold, firing rate, frequency selectivity, dynamic range, and in the timing of the unit discharge. Many of these changes reflect the development of structures peripheral to the cochlear nuclei, including the middle ear, cochlea, and auditory nerve. Others are likely the result of maturation of neuronal circuits within the cochlear nuclei. Not all functional properties recorded in a given neuron reach maturity at the same time. Those functional properties that emerge prior to the onset of normal auditory sensitivity would appear to be largely under genetic control. Other functional properties appear later in life and, therefore, their development may come under the influence of the acoustic environment. [NIH Grant HDO3353.]
Acoustic streaming reversal by a finite amplitude sound wave in a non-Newtonian fluid
Authors: Powell Robert L.
Published: October 2005

Theoretical predictions are presented for the steady secondary flows (acoustic streaming) produced by the propagation of a finite amplitude planar acoustic wave in a non-Newtonian fluid. The constitutive equation governing finite amplitude acoustic wave propagation in quiescent non-Newtonian fluids is derived and consists of an integral expansion of the constitutive functional. Each successive term of the expansion is higher order in a small parameter related to the amplitude of the propagated wave. The linear term of the expansion governs infinitesimal wave propagation and the quadratic term governs nonlinear effects. These equations are used to study the acoustic streaming caused by the propagation of a finite amplitude planar acoustic wave in a channel which has a width greater than that of the acoustic wave. The results show that because of nonlinear viscoelastic effects, the direction of the streaming can be opposite to that found for Newtonian fluids. [Work supported by NSF.]
X-ray microbeam study of velic movement
Authors: Condax I. D.
Published: October 2005

A radio-opaque pellet attached to the surface of an articulator and tracked with a computerized x-ray microbeam allows generally accurate observation of the coordination of several vocal organs during speech. In cases where specific details about a single articulator are sought, the possibility of artifacts in the signal cannot be neglected. As a case in point, the movement of the velum is studied in detail. A number of minor artifacts are identified. As one example, some movement in the pellet most likely results from contact between the pellet and the posterior pharyngeal wall, not from movement of the velum per se. The magnitude of the movements attributable to artifacts is small relative to the total range of movement. Removing the effects of the artifacts allows conclusions to be drawn about the movement of the velum. As one example, descending and ascending paths of the velum appear to be slightly different. [The work reported here was performed at Bell Laboratories, Murray Hill, NJ 07974.]
Jaw movements during increasingly rapid articulations of single syllables: Implications on speech motor control
Authors: Nelson W. L. , Westbury J. R.
Published: October 2005

A previous study of jaw movements in normal speech [W. L. Nelson, J. Acoust. Soc. Am. Suppl. I 68, S32 (1980)] suggested that the speech motor control process resulted in a relationship between movement time, distance, and peak velocity which implied (1) some adaptation to the physical effort required for the movement, and (2) that the force limit effective during speech was considerably below that which the jaw muscles are capable of producing. More recent measurements of jaw displacement, velocity, and EMG activity made during accelerated repetitions of the syllables /ja/ and /sa/ substantiate the previous results, and show evidence of recruitment of different muscles as the repetition rate increases.
Discrimination of rise time in nonspeech signals: Is it categorical or noncategorical?
Authors: Kewley-Port Diane , Pisoni David B.
Published: October 2005

Previous studies have reported that rise time at the onset of a sawtooth waveform may be discriminated in a categorical-like manner under some experimental conditions or according to Weber's law under other conditions. In the present experiments, rise time discrimination was examined with both the traditional ABX paradigm and an adaptive tracking procedure. Rise time varied from 0 to 80 ms in 10-ms intervals at the onset of a one second duration sawtooth signal. Discrimination functions were not categorical in the ABX task. This result was true even for subjects who practiced labeling the endpoint stimuli as “pluck” and “bow” before discrimination. In the adaptive tracking procedure, the Weber fraction obtained from the JND's of rise time was constant above 20-ms rise time. The results from the two paradigms were then compared by predicting a JND for rise time from ABX discrimination by means of the underlying psychometric function. Using this analysis, the apparently categorical discrimination results from previous studies were shown to be quite similar to the results observed in this study. Our results demonstrate clearly that rise time discrimination follows Weber's law. [Supported by NINCDS grant NS-12179.]
Pitch discrimination with very brief stimuli
Authors: Howse W. R. , Elfner L. F.
Published: October 2005

Discrimination of pitch of very brief stimuli was measured in two experiments using a two interval forced choice paradigm in which subjects indicated the stimulus complex that contained events less disparate in pitch. Stimuli were samples of sinusoids gated for 2, 4, 6, or 8 cycles. Estimates of minimum discriminable frequency difference (df/f) were made for 63, 125, 250, 500, 1000, and 2000 Hz. Results indicate that low-frequency pitch discrimination with brief stimuli is not adequately described by a simple frequency-time trading relationship of the form c = df ⋅ dtx. Results also indicate that for frequencies up to 1000 Hz the spectral modes of pitch perception are less appropriate than temporal models.
Repetition pitch with a continuously gliding rigid spectal envelope
Authors: Hartmann W. M.
Published: October 2005

The noise stimulus for repetition pitch has a spectral envelope consisting of an unlimited number of identical broad peaks. The frequency spacing between the peaks is 1/τ, the reciprocal of the repetition time. With appropriate digital techniques it is possible to cause the spectral envelope to glide slowly and indefinitely along the frequency axis, while maintaining a constant envelope shape and peak spacing. The pitch generated by this stimulus does not ascend or descend indefinitely, as in the illusions of Risset and Burns. Instead, there are several pitches, which follow repetitive sawtooth patterns. One pitch glide follows the pattern conjectured by F. A. Bilsen [Acustica 17, 295–300 (1966)], with a discontinuity from about 1/τ, ± 12% to 1/τ ∓ 12% near the cos− condition. Another pitch, heard for some positive spectral glides, has a discontinuity near the cos+ condition, beginning at 1/2τ and rising to 1/τ. There are sometimes other gliding pitches, not necessarily weaker than the above, for which we have no ready explanation. [Work partially supported by the NSF and the NIH.]
Tapping to repeated noise
Authors: Limbert Chrichton , Patterson Roy D.
Published: October 2005

When a sample of white noise is played cyclically the listener hears continuous noise with a periodicity superimposed upon it. Listeners were asked to tap in time to repeated-noise samples that were 0.25, 0.5, 1.0, or 2.0 s in duration; a run consisted of 100 taps. There were sixteen individual noise samples at each duration and each condition was replicated four times over two weeks. Listeners also tapped to trains of 20 ms pips that repeated every 0.25, 0.5, 1.0, or 2.0 s. The pip data are highly consistent across both listeners and replications; the tap occurs at the start of the pip. The relative standard deviation decreases with increasing cycle time. For the longer noise samples the standard deviation matches that of the pips; for the shorter samples it is approximately double that of the pips. In the vast majority of cases the tapping is consistent and occurs at one specific point in the noise. For some noise samples the tapping point shows a measure of consistency over replications and across listeners; for others there is little consistency.
A different look at the anechoic wedge
Authors: Warnaka Glenn E.
Published: October 2005

Anechoic wedges are conventionally installed with the tapered point of the wedge pointing toward the test space and with the flat base of the wedge either against a rigid wall or separated from the wall by an air gap. A comparative investigation has been carried out in which the wedges were first conventionally oriented and then turned 180° so that the points of the wedges faced the wall. These comparative tests were performed in reverberation rooms both here and in Europe and also in two different impedance tubes. The results are extremely interesting. They tend to indicate that a “reversed” anechoic wedge can give a lower cutoff frequency than when conventionally oriented. Some possible explanations are offered for the measured performance.
The 1981 ocean tomography experiment: Preliminary results
Authors:   The Ocean Tomography Group, Spindel R. C.
Published: October 2005

Preliminary results from a 1981 test ocean acoustic tomography experiment are presented. The system, deployed in the southern North Atlantic, consisted of four moorings with acoustic sources and five moorings with acoustic receivers in an approximately 300 km square array centered at 26 °N, 70 °W. Travel time variations of pulse-like signals transmitted from each source to each receiver were measured so that principles of time-of-flight tomography could be used to image the intervening sound speed field in three dimensions. Temporal and spatial sampling rates were chosen to measure mesoscale variability. Three CTD surveys and data from moored current meter and precision temperature-pressure recorders provided a conventional picture of mesoscale features in the experiment area. The experiment demonstrates the feasibility of ocean acoustic tomography.
Theory and technique of violin radiativity measurements
Authors: Weinreich Gabriel
Published: October 2005

The radiativity parameters comprise a quantitative specification of the sound field produced by a violin per unit force amplitude applied to the bridge by the vibrating string. A careful theoretical definition of these quantities makes possible absolute physical measurements that can be related to details of the violin's mechanical structure. Guided by such a definition, we have built a system that can make precise radiativity measurements over a large frequency range in a matter of minutes. The violin is mounted in a small nonreverberant chamber and is excited acoustically by a specially designed broadband signal digitally generated by a computer in real time. The same computer simultaneously samples the response of the violin and of some calibrating microphones. The amplitudes and phases of the corresponding spectral functions are then computed. A number of applications will be discussed. [Work supported by NSF.]