bluuebunny/crossref_metadata_2025 huggingface dataset:
Inferring articulatory movements from acoustic data
Authors: Stevens Kenneth N.
Published: October 2005

In recent years, there have been significant improvements in models for predicting the properties of the radiated sound when the time-varying configurations of the vocal tract and laryngeal structures are known. These advances have been especially evident for models of consonant production, for which there are rapid movements of the articulators and consequent rapid changes in the properties of the sound. Experience gained with these models has made it possible to infer articulatory and laryngeal configurations and movements from appropriate measurements of the sound. Several examples are given to illustrate how these inferences can be made. These include: (1) detailed measurements of the changing spectra of frication and aspiration noise at the release of a stop consonant to infer the position and rate of release of the major articulator and the changes in the laryngeal configuration; (2) measurements to indicate the time course of the velopharyngeal opening; and (3) measurements from which the glottal configuration can be estimated. [Research supported in part by the NIH.]
Modified two-mass model for the vocal cords
Authors: Pelorson X. , Hirschberg A. , Auregan Y.
Published: October 2005

The two-mass approximation is often presented as a simple but efficient model for the purpose of numerical synthesis of voiced sounds. However, the quality and the naturalness of the generated signal is still to be improved. A simple modification of the two-mass model is proposed in which the mechanical dynamics of that of two point masses. The movement of these point masses drives a two-parameter curve describing the smooth surface of the vocal folds. This representation allows description of unsteady flow separation within the glottis. A semiempirical boundary layer theory is used to calculate the position of flow separation. This theory is experimentally tested using stationary flow measurements and unsteady flow visualization. Furthermore, computed volume flux and Bernoulli force are presented and compared with classical models. The description also includes an inelastic collision which yields a prediction of an additional volume flux due to the deformation of the vocal folds after the through flux has been stopped by the closure of the glottis. This additional deformation appears to have a significant influence on the voiced sound production.
Recent work on biological choruses in Australian waters
Authors: Cato Douglas H. , McCauley Robert D.
Published: October 2005

Earlier studies of ambient noise in waters near Australia showed that diurnally varying biological choruses were widespread, especially in shallow tropical waters. The most common time of occurrence was between sunset and midnight and the choruses contributed to the frequency band 400 Hz to 5 kHz. Recent work has involved long-term measurements at a fixed location in the Great Barrier Reef with the view to identifying sources and determining the diurnal and seasonal patterns, with shorter measurements at other locations. The measurements show high level choruses over the frequency band 50 Hz to 2 kHz. The substantial lower frequency appears to result from the predominance of fish sources which involve the swimbladder in sound production. The diurnal and seasonal variation is complex, and differs significantly from species to species. There is some evidence of interaction between sources.
Analysis and modeling of the results of ECONOMEX
Authors: Wilson D. Keith , Frisk George V.
Published: October 2005

ECONOMEX was a study of ULF/VLF noise along an eastern US continental shelf/slope region, conducted between January and April 1991. Concurrent measurements of surface wave directional spectra and meteorological parameters were collected as a part of the SWADE experiment. Extended time series of pressure and bottom displacement have now been analyzed, plotted, and compared with predictions based on the local wave spectra. In most cases, the contribution from local sources appears far more significant than distant sources, such as storms. D. H. Cato’s dipole source mechanism [J. Acoust. Soc. Am. 57, 1076–1095 (1975)] agrees well with data from sensors ranging in depth between 450 and 2500 m, but the monopole mechanism is also significant at the shallowest sensor (100 m). A new method for evaluating Cato’s theory is also discussed. The method, since it involves direct evaluation of the dipole source convolution integral, does not require separability of the magnitude and directional dependence of the surface wave spectrum.
Rapid calculation of distant shipping noise in an underwater environment
Authors: Burkhalter Christopher J.
Published: October 2005

Various methods were explored and developed to simulate distant shipping ambient noise without executing very time-consuming sound propagation models for each surface ship contributing to the overall noise levels. The methods were developed with certain things in mind: the effects of various environments between source and receiver, the proximity of the surface ships to the receiver, horizontal directionality, source levels, vertical arrival structure, overall precision and accuracy, and substantial reductions in time for most runs. There was, of course, a direct trade-off between run times and the precision and accuracy of the answer, but because of the inherent randomness of ambient noise, in many cases the control case (i.e., a noise model with propagation model runs for each ship) differed only slightly from the much speedier alternatives developed here. Run times and results for the two methods were compared and analyzed. [Work supported by ONR, NRL, and the Univ. of New Orleans.]
Estimation of the spatial (vertical and horizontal) arrival structure of the undersea ambient noise from towed line array data
Authors: Wagstaff R. A.
Published: October 2005

Towed horizontal line arrays have been used very successfully in the past to acquire data to estimate the horizontal directionality of the ambient noise. Those estimates are commonly called noise roses. A more comprehensive algorithm which estimates the horizontal and vertical arrival structure of the ambient noise from towed line array data has been developed at NRL. The algorithm has been exercised with both simulated and measured data, and the results have been compared to noise roses that have been obtained from the same beam noise data using previous algorithms. The agreement has been good. In addition, the increased dimensionality of the new results has permitted the identification and quantification of spatial ‘‘holes’’ in the noise field that could be exploited by multidimensional arrays to achieve gains well in excess of that which one might expect from adding the independent gains for vertical and horizontal aperture. The algorithm is presented, and some results are discussed. [Work supported by the Office of Naval Research (ONR) and the ASW Environmental Acoustic Support (AEAS) Project.]
Ambient noise measurements in the southern Norwegian Sea
Authors: Kooney S. F.
Published: October 2005

Ambient noise horizontal directionality measurements were made in the southern Norwegian Sea by a towed horizontal line array during March 1992. The measurements were taken at three sites near an oceanographic front. The first site was north of the front, the second site was within the front, and the last site was south of the front. The ambient noise results, omnidirectional levels, and various beam noise statistics are discussed. In general, the low-frequency ambient noise showed approximately 15 dB more noise coming within a broad sector to the east and decreased with increased frequency. Along other azimuths, high levels in the horizontal directionality patterns correlated well with directions in which the bathymetry provided windows for the noise to propagate to the site from distant ships. The beam noise statistics at all three sites showed that the ambient noise possessed a high degree of spatial anisotropy at frequencies below 150 Hz and very little at frequencies of 300 Hz and above. [Work sponsored by the Office of Naval Research.]
Gaussian mixture statistical model of Arctic noise
Authors: Myers R. , Sotirin B.
Published: October 2005

Arctic ambient noise is often stationary and Gaussian for significant periods of time. However, during periods of local ice activity, the ambient noise can become highly non-Gaussian, nonstationary, and exhibit substantial variability in spectral shape. During these periods, the task of characterizing the statistics of the ambient noise is greatly complicated. In many cases, however, the distribution of the noise during the periods of intense ice activity can be modeled as a two-state Gaussian mixture, where the mixture parameters are estimated from the data by searching for the maximum of the likelihood function. A statistical analysis of selected ambient noise collected over a 10-day period during which long-range ambient noise was interspersed with intense, brief periods of local ice noise indicates that the ambient noise was highly Gaussian except during the periods of ice activity. During the periods of ice activity, the distribution of the ambient noise was modeled quite well as a two-state Gaussian mixture.
A dual surface approach to near-field measurements of target strength
Authors: Sartori Michael A. , Clark Joseph A.
Published: October 2005

Using near-field measurements of the pressure field over dual surfaces surrounding an immersed and insonified structure, an estimate of the structure’s target strength can be made. Choosing a cylindrical shaped surface, two measurement arrays enclosing the structure are formed with one array slightly larger than the other. At discrete points over the dual cylindrical shaped surfaces, two pressures are measured, and the pressure and the pressure gradient at these locations result. With the pressure and the pressure gradient, a discretized solution of the exterior Helmholtz integral is solved for the far-field pressure. Using the near-field measurements and this approach, far-field estimations of both radiation problems and target strength problems are possible. Using a rigid sphere as the insonified structure, the target strength problem is modeled and numerically solved using MATLAB. In this paper, an error analysis of this target strength application is presented. The effects on the estimated target strength due to different variables of the dual surface approach will be discussed, some of which include the following: open and closed dual surfaces; differences in the size of the dual surface; and variations on the density of the scanned dual surface. [Work supported by DARPA.]
Video-tape presentation of aerodynamic and respiratory kinematic measures during speech
Authors: Stathopoulos Elaine T.
Published: October 2005

A videotape of aerodynamic techniques for making measurements during speech production will be presented. Equipment shown will be: (1) a circumferentially vented pneumotachograph mask for sensing oral air flow [M. Rothenberg, J. Speech Hear. Res. 20, 155–176 (1977)], (2) a pitot tube for sensing intraoral air pressure, (3) a respirometer for air volume displacements, (4) a rotameter for calibrating airflow, and (5) a U-tube water manometer for calibrating air pressure. Discussion of calibration techniques and possible measurements during speech tasks will be displayed. A short segment of the tape will also demonstrate making simultaneous respiratory kinematic measures with linearized magnetometers using a child subject. Measures of lung volume, ribcage volume, and abdominal volume displacements will be shown. [Research supported by NIH.]
Laboratory and clinical use of the electroglottograph
Authors: Mahshie James J.
Published: October 2005

The electroglottograph is a device that enables monitoring of variations of vocal fold contact by measuring motion induced variations in impedance of neck tissue in the area of the vocal folds. Electroglottography represents one of the few noninvasive methods available for obtaining useful information about the vibratory patterns of the vocal folds. Since its initial description [Fabre, Bull. Acad. Med. (1957)], the electroglottograph has become an increasingly popular clinical and research tool, providing insight into numerous phonatory characteristics including vocal fundamental frequency (f0), the extent of vocal fold abduction during phonation, and alterations in laryngeal height during voicing. The purpose of this video presentation is to describe and demonstrate electroglottography, and to examine its use in the clinic and laboratory. The video will: (1) explain the principle of operation of the electroglottograph; (2) demonstrate setup and use of the device; (3) describe attributes of the electroglottograph signal; (4) demonstrate commercially available hardware and software designed to analyze the electroglottograph signal; and (5) describe clinical and research applications of the electroglottograph. The relative strengths and limitations of the device will also be described.
Masking can explain the effects of notched noise on forward-masked intensity discrimination
Authors: Zeng Fan-Gang
Published: October 2005

Plack and Viemeister [J. Acoust. Soc. Am. 92, 1902–1910 (1992)] investigated the role of ‘‘off-frequency’’ listening in a nonmonotonic intensity discrimination function under forward masking, in which a midlevel hump was originally reported for 25-ms sinusoidal standards presented 100 ms after an intense masker [Zeng etal., Hear. Res. 55, 223–230 (1991)]. Plack and Viemeister used a notched noise to prevent off-frequency listening and found that the notched noise removed or severely reduced the midlevel hump. A problem with the use of a notched noise in their experiment is that the level of the notched noise increases as a function of the standard level, introducing on-frequency masking in the form of elevated thresholds. They measured intensity discrimination at sensation levels between 10 and 14 dB, independent of the standard level. In the present study, the experiment of Plack and Viemeister was replicated with a narrow-band (800–1200 Hz) noise presented simultaneously with the sinusoidal standards to produce threshold elevations similar to the equivalent notched noise conditions. Presumably, the narrow-band noise does not prevent off-frequency listening, but severely reduces the midlevel hump in a fashion similar to the notched noise. This result suggests that the effects of notched noise on forward-masked intensity discrimination are mainly due to the on-frequency masking. The possible role of excitatory and suppressive masking at the auditory nerve level will be discussed. [Work supported by NIH.]
Diminished response to acoustic transients in aged rodents
Authors: Ison J. , Bowen P. , Barlow J. , Taylor M. , Walton Joseph P.
Published: October 2005

The startle reflex to an intense noise burst (S2) is depressed if weak transients (S1) precede S2. Noise pips and gaps in noise carriers preceded S2 at various lead times in young and old CBA/J mice. Old mice differed from young in three ways: (1) reflex amplitudes were lower; (2) prepulse thresholds for inhibition were raised, especially for high frequency pips; and (3) inhibition appeared at later lead times. Inhibition thresholds, but not its slowed development, were remedied with a stronger S1. Comparable effects were seen in the F344 rat. Single units in inferior colliculus in the mice showed that the aged IC had lost sensitivity to weak pulses. Minimal gap thresholds (1–2 ms) did not vary with age, but the younger animals had more units with lower gap thresholds. The reduced behavioral thresholds of the weak S1 likely result from the presbycusislike sensitivity changes. The slow onset time of inhibition may reflect the reduced size of the population of transient-sensitive units. [Work supported by NIH Grant No. AG09524 and the RICHS.]
Temporal pattern perception in the goldfish: Methods and models
Authors: Fay Richard R.
Published: October 2005

How goldfish perceive temporal patterns of acoustic clicks was investigated using a stimulus generalization paradigm with classical respiratory conditioning. Fish were conditioned to suppress respiration to trains of high-pass-filtered clicks with periodic inter click intervals (ICI). Five groups of animals were conditioned using ICIs between 4 and 25 ms, and then tested for response to eight novel ICIs between 4 and 25 ms. Response magnitude to novel ICIs (generalization) is a monotonic decreasing function of the difference between the conditioning and test ICIs. In further experiments, test stimuli consisted of temporally jittered periodic ICIs, and various pseudorandom ICI distributions. A model predicting the magnitude of generalization to these patterns was developed assuming that generalization is proportional to the number of ICIs common to conditioning and testing stimuli, and that the internal representation of ICIs has a variance predicted from discrimination data. Evidence was obtained that ICIs are analyzed, but that ICI representation is not necessarily congruent with that for pure tones of the same period. [Work supported by a Center Grant from the NIH NIDCD.]
Edge pitches of complex tones obtained at high frequencies
Authors: Kohlrausch Armin , Houtsma Adrianus J. M. , Kloos Sebastiaan J.
Published: October 2005

The upper edge pitch of harmonic complex tones was matched by adjusting the frequency of a sinusoidal comparison tone. Complexes with upper-edge frequencies between 2 and 8 kHz and fundamental frequencies of 50, 100, and 200 Hz were synthesized by adding all harmonics with equal amplitudes and with zero phases. Tones and intertone gaps had durations of 500 ms. Stimuli were presented diotically through Etymotic ER-2 insert earphones at a sound-pressure level of 60 dB. Five subjects performed ten matches for each complex, from which the standard deviation (s.d.) was calculated and expressed as percentage of the edge frequency. The s.d. generally increased with the edge frequency and with the fundamental frequency. For 50-Hz fundamental, the s.d. was only a factor two larger than in a sine-on-sine match, and four of the five subjects could perceive the edge pitch up to 8 kHz. For higher fundamental frequencies, more and more subjects lost the pitch percept at high edge frequencies, and for 200 Hz only one subject consistently matched the edge pitch at 8 kHz. The results emphasize the role of temporal processes in the perception of edge pitch as well as the importance of phase locking at the frequency of the edge component.
Phase sensitivity in psychoacoustical and physiological experiments
Authors: Vranić-Sowers S. , Versnel H. , Shamma S. A.
Published: October 2005

The physiological and psychophysical experiments in vision [R. L. De Valois and K. K. De Valois, SpatialVision (Oxford, New York, 1990)] indicate the existence of cortical cells that are tuned to a particular frequency of a sine wave grating. In present psychoacoustical experiments, listeners’ sensitivity to changes in phase of a sinusoidal ripple (in frequency domain, 41 components) was measured for different ripple frequencies and phases. The results were interpreted on the basis of responses to the same stimuli recorded from units of the primary auditory cortex (AI) in the anaesthetized ferret. Since phase sensitivity is associated with the asymmetry (or, ratio of excitatory and inhibitory portions) of cell’s response area, which varies along the isofrequency axis [Shamma etal., ‘‘Organization of response area of ferret primary auditory cortex,’’ J. Neurophysiol. (in press, 1993)], similar variations are expected for the phase sensitivity. The phase detection for any arbitrary stimuli (seen as a Fourier series) might be predicted from the corresponding results in single-ripple frequency sounds. Prediction for the spectral peak stimuli described in [Vranić-Sowers and Shamma, ‘‘The representation of spectral profiles in the auditory system,’’ J. Acoust. Soc. Am. (submitted, 1992)], is discussed. [Work supported in part by AFOSR and NRL.]
Cochlear nucleus neural mechanisms preserve complex- sound feature encoding in the presence of background noise
Authors: Frisina Robert D. , Walton Joseph P. , Karcich Kenneth J.
Published: October 2005

Rapid sound amplitude changes—amplitude modulation (AM)—are important features of communication sounds like speech, and play a role in other perceptual phenomena including sound localization and pitch perception. Some cochlear nucleus (CN) neurons preferentially amplify AM information, relative to their auditory-nerve (AN) inputs [Frisina etal., Hear. Res. 44, 99–122 (1990)]. An important question from scientific and clinical perspectives is: How does the remarkable ability of some CN neurons to process AM change when stimuli are presented in more realistic acoustic environments containing background noise? To address this, single-unit recordings were made from 105 CN neurons and 43 AN fibers of 17 anesthetized chinchillas. Results indicate: (1) Depending on a sound’s intensity and AM frequency, a continuous wideband background noise decreased, preserved, or enhanced a unit’s ability to encode AM relative to quiet; (2) in most cases, background noise reduces the average response to AM; (3) the synchronous response to AM (fundamental frequency response) decreased in units that decreased their AM coding, and generally increased in units that preserved or enhanced encoding of AM in noise; and (4) some of these effects of noise on CN AM processing can be explained by alterations in AN AM coding at moderate sound levels, but enhancement of CN AM coding at high-sound levels appears to be mediated primarily within the CN. [Supported by NIH-NIDCD Grant No. R29 DC00408-05 and the International Center for Hearing & Speech Research—RICHS.]
Detection and discrimination of mixed modulation signals at low-modulation frequencies
Authors: Edwards Brent W. , Viemeister Neal F.
Published: October 2005

Modulation detection thresholds were obtained for a fixed phase difference between the carrier and sidebands and for a fixed amplitude ratio between the lower and upper sidebands. These are three-component signals that, in general, contain both amplitude and instantaneous frequency fluctuations. In a manner similar to Moore and Sek [J. Acoust. Soc. Am. 92, 3119–3131 (1992)], psychometric functions were obtained for pure AM detection and for pure FM detection separately, and predictions made for the thresholds of the general three-component signals. The best fit to the data was obtained when the d’s for AM and FM were added in a linear manner, i.e., d’TOT=d’AM+d’FM. Thresholds for discrimination were then obtained for both AM and FM signals. The standard was a three-component signal with fixed carrier phase and modulation depth set to the detection threshold measured in the first experiment. Discrimination thresholds were elevated and were independent of the standard’s carrier phase, i.e., the ratio of AM to FM in the standard. This implies a common decision statistic for both AM and FM signals near threshold. [Work supported by NIDCD Grant No. DC00683.]
Detection of mixed modulation at 6 kHz
Authors: Sek Aleksander , Moore Brian C. J.
Published: October 2005

Previously [B. C. J. Moore and A. Sek, J. Acoust. Soc. Am. 92, 3119–3131 (1992)], psychometric functions were measured for the detection of amplitude modulation (AM) alone and frequency modulation (FM) alone, using a 1-kHz carrier and a modulation rate of 10 Hz. Detectability (d’) was then measured for combined AM and FM, with modulation depths selected so that each type of modulation would be equally detectable if presented alone. Significant effects of relative modulator phase were found. Further, d’ for combined AM and FM was better than would be predicted if the two types of modulation were coded completely independently. However, the phase effects were not correctly predicted by excitation pattern models. Moore and Sek suggested that the good performance for combined AM and FM may have occurred because FM is coded by changes both in excitation level and in phase locking. This idea was tested by repeating the earlier experiment with a carrier frequency of 6 kHz, a frequency where phase locking does not occur. The pattern of results was similar to that obtained for the 1-kHz carrier. [Work supported by The Royal Society and the MRC, UK.]
Scattering from a thin spherical shell: Higher-order Lamb waves
Authors: Sammelmann Gary Steven , Hackman Roger H. , Werby Michael F.
Published: October 2005

The acoustic scattering from thin spherical shells is marked by the existence of the thickness quasiresonance in the high-frequency regime. This quasiresonance is due to the existence of a region of negative group velocity surrounding the first symmetric Lamb wave. This article presents results on the existence of higher-order quasiresonancelike phenomena, and it considers the effects of Poisson’s ratio on the quasiresonance. Pole trajectories in the complex ka plane are exhibited for the first dozen modes on a spherical shell. This analysis reveals the existence of regions of negative group velocity surrounding higher-order Lamb waves. A time domain representation of the contributions of higher-order Lamb waves to the scattered field is presented. This analysis reveals the early time arrival nature of the thickness quasiresonance as reconstructed from the poles in the complex ka plane.
Scattering from submerged elastic shells and the characterization of resonances at coincidence frequency: A consensus view
Authors: Werby Michael F. , Hackman Roger H. , Überall H. , Sammelmann Gary Steven
Published: October 2005

In the neighborhood of coincidence frequency for submerged shells (the frequency at which the flexural phase velocity for a plate or shell equals the phase velocity of the speed of sound in the ambient fluid), very large returns are observed which typically include large amplitude narrow spiked returns superimposed on a broad Gaussian shaped return. Each of us as well as the French group (M. Talmant and G. Quentin, University of Paris, 7) have ventured an interpretation of these events for which the interpretations are fairly consistent with some minor variations in detail. As in any new study, differing language was employed. This presentation offers a consensus view of the event along with proposed language for future use.
Time-frequency domain processing of acoustic echoes from elastic shells in water
Authors: Gaunaurd G. C. , Strifors H. C.
Published: October 2005

Acoustic echoes have been studied from submerged elastic shells in either the frequency or the time domains in a number of earlier works. They are now studied and processed in the combined time-frequency (t−f) domain, using both idealized and realistic incident pulses. In a first analysis, (Gaussian) time-windowed Fourier transforms are used, and later, pseudo-Wigner distributions (PWD) are used, and applied to the cases of both ideal and realistic incident pulses. These echo processing techniques extract in various ways the time evolution of the resonances that the target in question may contain within the chosen (broad) operational band. Suitable choice of viewing windows and carrier frequencies serves to generate (t−f) domain displays in which clearly recognizable resonance features become evident. These can then be linked to particular target characteristics. The adjustable widths of the time windows control the amount of detail in the displays. The resulting three-dimensional plots will be shown in an informative colorized format for various cases dealing with elastic shells in water. This will illustrate the target-ID or target characterization merits of this approach, over those obtainable from the usual (monostatic) sonar cross sections.
Stop-band and passband behavior of ribbed cylinders
Authors: Clark Joseph A. , Sartori Michael A.
Published: October 2005

As observed through an experimental analysis, the presence of ribs in a cylinder produces two types of stop-band and passband behavior. One type of stop-band and passband behavior concerns the passage of waves along the cylinder. Depending on frequency, energy from a vibrational source will either pass along a ribbed cylinder or be stopped by the ribs. A second type of stop-band and passband behavior involves the radiation of vibrational energy to the far field, which is also dependent upon frequency. These two types of behavior have been observed experimentally on an immersed cylinder 5 ft. in length, 1 ft. in diameter, and with 30 ribs. Exciting the cylinder in an n=0 circumferential mode with an internal array of shakers, the cylinder’s radiation was measured at 180 positions along the cylinder’s length with a hydrophone located in the cylinder’s evanescent near field. Measurements of two cylinders (one with ribs and one without ribs) were made and were processed to obtain position—frequency and wave number—frequency plots. Using these plots, the stop-band and passband behavior that can be attributed to the ribs will be presented as features of wave propagation along the cylinder and as radiation effects in the far field. The experimental results will also be compared with a numerical analysis of an infinite cylinder with periodically spaced ribs. [Work supported by ONT.]
Three-process model of auditory-nerve fiber tuning curve shapes
Authors: Javel Eric
Published: October 2005

Cat auditory-nerve fiber tuning curves were fitted by a three-process model consisting of an acoustic resonance (for tuning curve ‘‘tails’’), a skewed function formed by subtracting two exponentials (for basilar membrane resonances), and a Gaussian function (for the active gain responsible for sharp tuning). Thresholds were taken as the sum of pressures provided by the two resonances, multiplicatively enhanced in a spatially dependent manner by the active gain. Fits were generally excellent. ‘‘Tails’’ possessed center frequencies (1–3 kHz) and minima (60–80 dB SPL) that varied from animal to animal and depended on fiber CF. Basilar membrane resonances possessed average minima of 30–50 dB SPL in low-threshold fibers, tuning that increased in sharpness with CF or threshold, and center frequencies that were typically lower (for CFs ≳1 kHz) or higher (for CFs <1 kHz) than the center frequencies of the associated active gains. Average active gain magnitude in low-threshold fibers increased smoothly from <10 dB in low-CF fibers to ≳40 dB in high-CF fibers, and was reduced or absent in most high-threshold fibers. The average spatial extent of the active gain was remarkably constant at 1 mm regardless of gain magnitude, fiber CF, or threshold sensitivity. [Work supported by NIDCD.]
Characterizing auditory filter nonlinearity at 2 kHz
Authors: Rosen Stuart , Baker Richard J.
Published: October 2005

Although it is well known that psychoacoustically measured auditory filters broaden with increases in level, it is not yet clear what aspect of the acoustic stimulus controls this nonlinearity—that is, whether the change in bandwidth is controlled primarily by the level of the probe or masker. Therefore, a new method has been developed for fitting filter shapes to notched-noise data in which filter parameters depend explicitly on signal level (probe or masker). By applying this technique to notched-noise data in which both fixed-probe and fixed-masker paradigms have been used at a range of levels, it was possible to show that models in which filter parameters depend on probe level fit the data considerably better than models in which filter parameters depend upon masker level. Furthermore, it was possible to describe the nonlinear changes in auditory filter bandwidth at 2 kHz with only five parameters, allowing the implementation of reasonably realistic computational nonlinear auditory filters whose shape depends on their output. [Work supported primarily by the Medical Research Council (UK), with important contributions from the Hearing Research Trust.]
A comparison of peripheral and ‘‘attentional’’ auditory filters
Authors: Neff Donna L. , Dethlefs Theresa M. , Jesteadt Walt , Lutfi Robert A.
Published: October 2005

The relation between peripheral and ‘‘attentional’’ filters was explored in simultaneous masking for eight normal-hearing listeners. Thresholds for a sinusoidal signal at 1000 Hz were measured as a spectral gap in a masker was progressively widened. For peripheral filters, the masker was a notched noise and a one-parameter ROEX model was used to describe filter properties. For ‘‘attentional’’ filters, the maskers were multicomponent complexes of two or ten components of random frequency content, and the ROEX model was again applied. Indices of peripheral filter width did not distinguish listeners who showed large versus small effects of masker uncertainty in the ‘‘attentional’’ filter conditions. Indices of peripheral processing efficiency, however, were poorer for listeners showing large uncertainty effects, as were measures of both the width and processing efficiency of presumed ‘‘attentional’’ filters. An alternative analysis of the ‘‘attentional’’ filter data will examine whether component entropy or relative variance [R. A. Lutfi, J. Acoust. Soc. Am. (to be published)] can account for the decline in masking observed as the spectral gap in the masker is increased. [Work supported by AFOSR and NIDCD.]
Noise production by turbulent flow over an unscreened measurement microphone
Authors: Morgan Scott , Raspet Richard
Published: October 2005

In previous work, it has been shown that the wind noise in an unscreened microphone placed in a low-speed turbulent flow is caused by the turbulence intrinsic in the flow [S. Morgan and R. Raspet, J. Acoust. Soc. Am. 92, 1180–1183 (1992)]. The theory of pressure fluctuations in a turbulent flow as related to wind noise in an unscreened measurement microphone is discussed in this paper. A Poisson’s equation for fluctuation pressure in terms of mean and fluctuation velocity derivatives with respect to spatial dimensions results from the theory. This implies that the mean and fluctuation velocities must be known at every point in space in order to solve for the fluctuation pressure at a given point; however, through comparison of theory with experimental data, it is shown that the fluctuations in the boundary layer near the microphone where velocity gradients are very large provide the major source of wind noise. An approximation method for estimating the contribution of this ‘‘local interaction’’ is also discussed.
Determination of the properties of air-filled porous media using level difference and probe microphone measurements
Authors: Frederickson Carl K. , Sabatier James M. , Raspet Richard
Published: October 2005

Level difference measurements have been used to determine three properties of air filled porous media; porosity, tortuosity, and flow resistivity [Soil Sci. Soc. Am. J. 54, 658–672 (1990)]. These can be used to find the characteristic acoustic impedance of a porous medium. It can be shown that the level difference measurement alone does not contain enough information to uniquely determine more than two of these properties. A second measurement is needed to determine one of the properties. A probe microphone can be used to determine either the flow resistivity or the tortuosity; either of which can then be used in the level difference calculation to determine the other two properties. An experiment has been performed to determine the viability of this combined technique for characterizing the ground. Probe microphone measurements were made in a container of 0.526-mm glass beads. This same size of bead was then used in level difference measurements. As the beads are spherical the porosity is known. Values of flow resistivity and tortuosity obtained from both the level differences and probe microphone measurements agree fairly well. [Work supported by the US Department of Agriculture.]
Neural network supporting auditory-vocal integration in singing
Authors: Perry David W. , Alivisatos Bessie , Evans Alan C. , Meyer Ernst , Petrides Michael , Zatorre Robert J.
Published: October 2005

Although much is known about the auditory nervous system, in both man and nonhuman primates, and about the neural substrates for vocal production, particularly in nonhuman primates, relatively little is known about how these two systems are integrated in vocal behavior. The present study used positron emission tomography with magnetic resonance imaging to investigate regional changes in blood flow during the performance of a rudimentary singing task by 12 healthy right-handed volunteers. When activation during the repetetive singing of a single target pitch was compared to that during passive auditory stimulation with complex tones in the same frequency range, a widely distributed network of activated brain regions was observed. Some regions of activation were plausibly explained by the auditory stimulation of self-vocalization (right medial geniculate body and right primary auditory cortex), while others were clearly related to the act of vocalization (periaqueductal grey, subcallosal anterior cingulate gyrus, supplementary motor area, cerebellum and primary motor face region, bilaterally). Finally, the neuroanatomical connections of the mid-dorsal insula, activated bilaterally, and of the dorsomedial thalamus are suggestive of a particular role in auditory-vocal integration. It is proposed that auditory-vocal integration, both in singing and in speech, involves complex neural interconnections between many of the above regions.
What OSHA is doing to minimize the effect of radio interference on acoustical instruments
Authors: Feldman Raymond F.
Published: October 2005

Acoustical instruments are more susceptible to radio interference than many users find acceptable. Degraded performance caused by electromagnetic fields is called electromagnetic susceptibility (EMS). In the past, performance standards for acoustical instruments, and all industrial hygiene instruments in general, have not adequately addressed this problem. EMS deficiencies can range from subtle deviations to gross errors in sound measurements. It has even been reported, that EMS has caused audiometers to malfunction and blast the ears of patients with sound levels of 80 and 90 dBA. The OSHA Cincinnati Laboratory has been working to reduce EMS effects on sound instruments that are used by OSHA and MSHA. Manufacturers are being persuaded to meet EMS performance specifications for instruments which these agencies purchase. These requirements assure the instruments will operate properly in industrial and mining environments. In 1992, ASA established an ANSI/ASA working group to write an EMS standard for acoustical instruments.
An application of matched-field processing to the determination of under-ice reflection coefficients and other parameters using long-range, low-frequency data
Authors: Livingston E.
Published: October 2005

Average low-frequency under-ice reflection coefficients were estimated from long-range Arctic data (FRAM IV) by matched-field processing techniques (Livingston and Diachok, 1989). The method is a straightforward application of optimization using multiple thresholds over a finite set of parameter values, and will be described and discussed with regard to its advantages, disadvantages, and appropriate problem settings. The performance of this method in problems of determining sound-speed structure, optimum replica mode number, and several other types of parameters will be analyzed. In particular, the possible application of the method to the determination of bottom reflection coefficients is considered.
Waveform analysis of seafloor Scholte waves
Authors: Nolet Guust , Dorman LeRoy M.
Published: October 2005

A new method of nonlinear waveform inversion to model Scholte waves has been tested. Synthetic displacements were computed for an explosive source at the ocean bottom for frequencies up to about 2.5 Hz. At the distance range of interest (<1 km) only the first few modes of the Scholte waves are present, with most energy in the fundamental mode. Linear perturbation theory is used in our scheme to predict changes in wave number produced by changes in the model. This theory degenerates at those frequencies where modes can escape the sediments and where the phase velocity changes suddenly from approximately 0.1 to 1.5 km/s. The step length for wave-number changes were limited to deal with this problem. This did not noticeably degrade convergence. The method was tested on observed waveforms from an experiment at Deep Sea Drilling Project site 469. This site is at 3.8-km water depth just off the Patton Escarpment, about 300 km west of San Diego. The seismic velocities there are quite uniform laterally. The surficial shear velocity is about 30 m/s. [Work supported by ONR.]
Similarity judgments of fifth-spaced tones and dyads thereof
Authors: Parncutt Richard
Published: October 2005

A fifth-spaced tone (FST) is a complex tone whose partials are equally spaced in log frequency at intervals of a musical fifth (seven semitones, frequency ratio ∼2:3) across a broad frequency band (like Shephard tones, but with fifths instead of octaves). The perception of single FSTs (monads), and dyads of FSTs spanning the intervals M2 (two semitones, frequency ratio ∼8:9) and m3 (three semitones, ∼5:6), was investigated by asking ten musicians and ten nonmusicians to rate the similarity of all pairwise combinations of monad, M2 dyad, and m3 dyad. Sequential intervals ranged from 0 to 6 semitones (i.e., all possible intervals in the chromatic scale). Results were compared with predictions according to the theories of virtual pitch [Terhardt etal., J. Acoust. Soc. Am. 71, 679–688 (1982)] and pitch commonality [R. Parncutt, Harmony: APsychoacousticalApproach (Springer-Verlag, New York, 1989)]. The salience of virtual pitches by comparison to spectral pitches in monads and dyads of FSTs was found to be consistently lower than predicted by the models. [Work supported by NSERC Canada.]
Listener performance under variations in signal content
Authors: Schultz Martin , Kah Tan
Published: October 2005

Signal detection theory holds that performance can be modeled under conditions of physical specification of signals and systems, with no attention given to signal informational content. By contrast, Shannon [Bell Syst. Tech. J. 30, 50–64 (1951)] proposed that performance is open to coding influences and, therefore, may vary with signal content. This study examined performance of subjects for three-element sequences wherein the content varied systematically from words, to nonword, vocal system outputs, to speech-patterned noises. Signals formed a twenty sequences closed set, randomly selected and delivered with equal probabilities. Subjects were trained prior to experimental runs to a 90% criterion but probably not to asymptotic performance, using trial-by-trial feedback. All signal elements were represented by multiple tokens and all signals were of equal power and duration. Training was accomplished in the ‘‘clear,’’ signal/noise ratio was an experimental variable and both training and experimental conditions were self-paced. Subjects were paid for performance throughout. Results are discussed from several theoretical perspectives.
A developmental study of the perception of onset spectra for stop consonants in different vowel environments
Authors: Ohde Ralph N. , Haley Katarina , Voperian Houri K.
Published: October 2005

The purpose of this study was to assess the perceptual role of integration and dynamic time-varying spectral cues for stop consonants in children and adults. Stop-consonant syllables were synthesized in the context of two vowels, /i, ɑ /. These syllables were synthesized with and without bursts, and contained formant motions and/or formant onset frequencies appropriate for each stop-consonant place of articulation. In addition, syllable duration varied between 10 to 46 ms. Children at five age levels, 4, 5, 7, 9, and 11, and a control group of adults were trained to identify the consonant as either /b/, /d/, or /g/. Preliminary findings indicate that dynamic time-varying spectral changes are not essential for accurate identification of stop consonants across all contexts. The results also show that the integration of noise bursts and formant onset frequencies, and syllable duration improve identification of alveolar and velar stops, particularly for children. The findings will be discussed relative to: (1) the differences between children and adults in processing integration and dynamic time-varying spectral cues, and (2) the developmental role of stimulus duration in the perception of stop consonants. [Work supported by NIH, DC00464.]
Acoustic correlates of phonetic prototypes: Velar stops
Authors: Davis Katharine , Kuhl Patricia K.
Published: October 2005

Studies on vowels by Kuhl and her colleagues have shown that certain stimuli in a vowel category are rates as ‘‘better exemplars’’ (prototypes) than others. The present study extends this work to consonants. Ten adult speakers of American English recorded 20 different words with initial velar stops before the vowel /æ/. These 200 tokens were digitized and edited to include only two pitch periods of the following vowel in addition to the initial consonant. The resulting stimuli were presented to 8 adult subjects who were asked to rate their ‘‘representativeness’’ as members of the voiced or voiceless category (1=poor, 7=excellent). Acoustic parameters of the stimuli were correlated with subjects’ ratings to determine which variables (including voice onset time, burst duration, burst locus, etc.) had the most effect on subjects’ goodness judgments. Initial results [K. Davis and P. K. Kuhl, Proc. ICSLP, 495–498 (1992)] showed that VOT was strongly correlated with perceived category goodness. Now additional acoustic cues have been included and multiple regression analyses have been used which show effects of VOT, aspiration amplitude, and fundamental frequency of the following vowel in certain cases. The present study also investigates the response of Hindi speakers to the identical stimuli when judging goodness according to Hindi voicing categories.
Cue interaction in an intervocalic voiceless affricate/fricative contrast
Authors: Rosen Stuart , Darling Angela M. , Faulkner Andrew , Huckvale Mark
Published: October 2005

The distinction between intervocalic voiceless affricates and fricatives is a useful one for studies of cue interaction in speech for two main reasons. First, there are at least three temporal cues that are known to interact in this contrast (the duration of the silence preceding the frication, the rise time of the frication, and the duration of the frication). Second, there have been a number of claims that auditory processes may play a crucial role both in the perception of some of the individual cues (in particular, rise time), and in accounting for the interaction of some cues (in particular, silence duration and rise time). New empirical data is presented from a multifactorial identification experiment (involving the simultaneous variation of silence duration, frication rise time and frication duration) and the extent to which various theories of affricate/fricative perception can account for the observed results is examined. [Work supported by the Joint Council Initiative in Cognitive Science/HCI (UK).]