bluuebunny/crossref_metadata_2025 huggingface dataset:
Analyzing and modeling fractal intensity point processes
Authors: Kumar Anand R. , Johnson Don H.
Published: October 2005

Fractal intensity point processes—doubly stochastic point processes with a fractal waveform intensity process—are required to describe the discharge patterns recorded from the auditory and visual systems. The Fano factor—the ratio of the variance of the number of events in an interval to the mean of this number—captures the self-similar characteristics of the intensity via two quantities: fractal dimension and fractal time. The fractal dimension is the exponent of the asymptotic power law behavior of the Fano factor with interval duration. The fractal time delineates long-term fractal behavior from short-term characteristics of the data. The average rate and self-similarity parameter of the intensity process, absolute and relative refractory effects, and serial dependence all modify the fractal time. To generate fractal intensity point processes, stochastic fractal processes are derived by applying memoryless, nonlinear transformations to fractional Gaussian noise. The intensity’s amplitude distribution in combination with the Fano factor form criteria to choose the transformation that best describes data.
Coherence of acoustic scattering from a dynamic rough surface
Authors: Dowling David R. , Jackson Darrell R.
Published: October 2005

Numerical studies of the angular and temporal coherence of rough-surface acoustic scattering are presented at kh=12, 20, and 32, where k is the acoustic wave number and h is the root-mean-square surface height fluctuation. The computations are based on point-source illumination of a one-dimensional pressure-release Pierson–Moskowitz dynamic rough surface, and the Kirchhoff approximation. In the region near specular, for a source-location grazing angle of 20°, the angular variation of the scattered field coherence is found to predominantly depend on the product of k and a fixed length scale. The computed results show only a mild dependence on kh. For the same geometry, the temporal variation of the scattered field coherence is found to depend predominantly on (g Δt/U)kh, where g is the acceleration of gravity, Δt is the time shift, and U is the wind speed. A general method for scaling the scattered field coherence in terms of k, Δt, U, and the angular separation of the field points is suggested based on the findings. The effects of wind direction and surface-wave frequency cutoff on acoustic scattering are also noted.
On the validity of the wedge assemblage method for pressure-release sinusoids
Authors: Keiffer Richard S.
Published: October 2005

In the past, the wedge assemblage (WA) method for calculating the acoustic scattering from rough, long-crested, or corrugated surfaces has been compared with both experimental data and exact theory with good results. Nevertheless, significant questions about what physics is included in the method and its realm of validity remain unanswered. In this paper, the WA method is applied to scattering from pressure-release sinusoidal surfaces in order to further explore these topics. Comparisons with accurate benchmark calculations are carried out over a broad range of kh and kΛ (k is the acoustic wave number; h and Λ are the amplitude and wavelength of the sinusoid, respectively) indicate that the primary limitation of the WA method stems from its current failure to include multiple scattering effects. It is also shown that quite good agreement with the benchmark can be achieved by a ‘‘diffraction-only’’ WA model even when kh≪1 and ‘‘reflection-like’’ scattering patterns are observed.
Separation of concurrent harmonic sounds: Fundamental frequency estimation and a time-domain cancellation model of auditory processing
Authors: de Cheveigné Alain
Published: October 2005

Signal-processing methods and auditory models for separation of concurrent harmonic sounds are reviewed, and a processing principle is proposed that cancels harmonic interference in the time domain. The principle is first formulated in signal processing terms as a time-domain comb filter. The critical issue of fundamental frequency estimation is investigated and an algorithm is proposed. Tested on a restricted database of natural voiced speech, the algorithm successfully found estimates correct within 3% of an octave for 90% of all frames. Next, the principle is formulated in physiological terms. A hypothetical ‘‘neural comb filter’’ is described, based on neural delay lines and inhibitory synapses, and tested using auditory-nerve fiber discharge data obtained in response to concurrent vowels [A. R. Palmer, J. Acoust. Soc. Am. 88, 1412–1426 (1990)]. Processing successfully suppresses the correlates of either vowel in the response of fibers that respond to both, allowing the other vowel to be better represented. The filter belongs to the class of ‘‘cancellation models’’ for which predictions can be made concerning the outcome of certain psychoacoustic experiments. These predictions are discussed in relation to recent experimental results obtained elsewhere.
Analysis of transient-evoked otoacoustic emissions in normal-hearing and hearing-impaired ears
Authors: Prieve Beth A. , Gorga Michael P. , Schmidt Alicia , Neely Stephen , Peters Jo , Schultes Laura , Jesteadt Walt
Published: October 2005

Transient-evoked otoacoustic emissions (TEOAEs) were measured in 113 normal-hearing and hearing-impaired ears to examine repeatability within a test session, which TEOAE parameter (level, TEOAE level-to-noise or reproducibility) best identified hearing loss and if the TEOAE separated into frequency-specific bands identified hearing loss in a corresponding frequency region. TEOAEs and stimulus levels were found to be very repeatable. For broadband TEOAEs, TEOAE level, TEOAE-to-noise, and % reproducibility were found to identify hearing loss equally well, based on measurement of the area underlying relative operator characteristic curves. Analysis for frequency-specific bands showed that separation of normal-hearing and hearing-impaired ears depended on frequency, with best identification at 2000 and 4000 Hz, identification at 1000 Hz slightly worse, and virtually no separation between normal-hearing and hearing-impaired ears at 500 Hz. Again, all three parameters were essentially equal in identifying hearing loss. Subjective evaluations of presence or absence of TEOAEs was highly correlated between two judges, with good agreement for TEOAEs at 1000, 2000, and 4000 Hz. The findings from this study suggest that TEOAEs will be valuable for clinical use because of their repeatability and identification of hearing-impaired ears.
The spectral shaping of neural discharges by refractory effects
Authors: Edwards Brent W. , Wakefield Gregory H. , Powers Nick L.
Published: October 2005

It has previously been shown that post-stimulus time (PST) histograms have autoregressive properties, which implies that the neural firings have spectral components that are determined by these properties. The expected power spectral density of neural discharges is derived when the process is firing at a constant rate (similar to tonal stimulation at CF with no phase locking). Although the unconditional intensity of the process is not time varying, the spectrum exhibits prominent spectral peaks. The effect of histogram bin size, stimulus intensity, and refractory effects are examined with respect to spectral shape and it is shown that stimulus intensity determines the magnitude of spectral peaks while refractory duration determines the peak locations. The effectiveness of predicting the spectrum is demonstrated with eight-nerve data and point process simulations.
Deformation and location of an acoustically levitated liquid drop
Authors: Tian Yuren , Holt R. Glynn , Apfel Robert E.
Published: October 2005

A theoretical method to determine the location and static deformation of an acoustically levitated liquid drop in air is presented. The interaction between drop and sound field, involving nonspherical acoustic scattering and drop volume variation, is the crux of this analysis, which is valid for drops with aspect ratio as large as 2. Numerical calculations are presented of drop shape and location as functions of sound pressure, surface tension, and drop volume in both gravity (1g) and gravity-free (0g) environments. The numerical results agree well with our experimental measurements and those of other researchers.
Acoustic scattering from a rough sphere
Authors: Jansson Per-Åke
Published: October 2005

The scattering of a plane acoustic wave from a random rough sphere is studied using the null field approach. The starting point is an integral representation derived from the Helmholtz equation. The incident field, the scattered field, and the free-space Green’s function are all expanded in terms of suitably chosen basis functions. In this way a relation between the incident and the scattered fields is obtained, which is expressed by the transition matrix (T matrix). The scattered field is expanded in a power series of a small parameter, namely the product of the wave number and the root-mean-square height of the irregularities. Analytical expressions for the leading terms of the series have been calculated. In particular, ensemble averages of the far-field amplitude and the scattering cross section have been determined. As the analytical results are somewhat complicated, some numerical results are presented. Numerical computations of higher-order terms indicate that the convergence of the series is satisfactory as long as the root-mean-square height is small compared to a correlation length describing the average distance between the peaks of the surface.
Further analysis of target strength measurements of Antarctic krill at 38 and 120 kHz: Comparison with deformed cylinder model and inference of orientation distribution
Authors: Chu Dezhang , Foote Kenneth G. , Stanton Timothy K.
Published: October 2005

Data collected during the krill target strength experiment [J. Acoust. Soc. Am. 87, 16–24 (1990)] are examined in the light of a recent zooplankton scattering model where the elongated animals are modeled as deformed finite cylinders [J. Acoust. Soc. Am. 86, 691–705 (1989)]. Exercise of the model under assumption of an orientation distribution allows absolute predictions of target strength to be made at each frequency. By requiring that the difference between predicted and measured target strengths be a minimum in a least-squares sense, it is possible to infer the orientation distribution. This useful biological quantity was not obtainable in the previous analysis which involved the sphere scattering model.
Low-frequency Arctic reverberation. I: Measurement of under-ice backscattering strengths from short-range direct-path returns
Authors: Hayward T. J. , Yang T. C.
Published: October 2005

Under-ice scattering strengths in the backward direction were measured in April 1989 during the CEAREX 89 field experiment in the Norwegian-Greenland Sea using a large-aperture (1200-m) vertical hydrophone array and 1.8-lb SUS explosive sources. Scattering strength estimates for frequencies of 24–105 Hz are presented as a function of scattering angle (2.5°–40° grazing), averaged over incident angles in the range 10°–15° grazing. The corresponding (monostatic) backscattering strength is found to be approximately 10 dB below that reported by Milne [J. Acoust. Soc. Am. 36, 1551–1556 (1964)] for data collected at approximately the same time of year in 1962 near the Canadian Archipelago. The results are compared with scattering functions derived from a Burke–Twersky model [J. Acoust. Soc. Am. 40, 883–895 (1966)], which represents the ice ridges as rigid elliptical half-cylinders. The variations of the measured scattering strength with both scattering angle and frequency are well fitted by this model for scattering angles below 20° grazing.
Application of ray theory with beam displacement to three-dimensional sound propagation in a wedge-shaped ocean
Authors: Avudainayagam K. V. , Anand G. V.
Published: October 2005

Ray theory with beam displacement (RTBD) has been developed to evaluate the acoustic field in three dimensions in a wedge-shaped ocean with a lossy fluid bottom. An algorithm for tracing eigenrays in three dimensions is described. A procedure for determining the location of caustics in three dimensions is also presented. It is shown that the density of caustics reduces with increasing bottom attenuation. Sharp spurious peaks appear in the acoustic field in the vicinity of caustics. These caustic-related peaks can be readily identified and smoothed out, and no further corrections would be necessary in most situations of practical interest. Agreement between the smoothed RTBD solution and the ‘‘exact’’ two-way coupled-mode solution is quite good for the two-dimensional problem of up-slope propagation in the ASA benchmark wedge with a penetrable lossy bottom. Numerical results for the three-dimensional problem are presented for several bottom slopes and directions of propagation.
Quantitative reconstruction of internal density distributions from laser ultrasonic data
Authors: Lu Yichi , Goldman Jeffrey A. , Wadley Haydn N. G.
Published: October 2005

An ultrasonic method has been investigated for the quantitative recovery of density distributions of porous bodies similar to those produced by pressure-assisted sintering of powders. It relies upon the strong relationship between the ultrasonic velocity and the density of a porous body. Noncontact laser-generated/interferometrically detected ultrasound has been propagated along ray paths in a planar cross section of model samples and ultrasonic time-of-flight projections obtained. Two approaches have been explored for reconstructing the internal velocity (and thus density) distribution from the projection data. The first approach was a standard convolution backprojection algorithm used frequently in computerized tomographic reconstruction. A combination of ray bending (due to refraction by the velocity gradient within the sample), noise in the projections, and practical limits upon the number of projections that can be obtained have all adversely affected the reconstruction quality of this method. The second approach explored a (nontomographic) nonlinear least-squares approach. It utilized a priori information about the general functional form of the velocity (density) distribution (which is available from predictive models of the densification process) and gave significantly better results for samples with simple geometry even when projection data were sparse.
Optimization of location and amount of viscous damping to minimize random vibration
Authors: Neubert Vernon H.
Published: October 2005

A novel procedure is presented for minimizing random vibrations of a linear, elastic structure by optimizing the size and location of viscous damping devices, with a constraint on the total amount of damping available. Viscous damping, represented symbolically by dashpots between structural nodes, can be achieved practically by using fluid devices or magnetic eddy-current devices. The problem is developed as a nonlinear optimization problem. Nonproportional damping is considered. Since the mean-square response depends on the modal damping ratios, first, the sensitivities, or partial derivatives, of the modal damping ratios with respect to the system damping parameters are discussed. The sensitivities are sometimes negative, which means that simply increasing the size of some dashpots could increase response. Second, the sensitivities of the mean-square amplitudes to the system damping parameters are determined and used to minimize the response. A two-parameter example is presented for a ten-bar truss for which the optimum parameters are found by a modification of the method of steepest descent. The problem was solved using the program tpsens, developed as part of this study. A ten-parameter optimization is also described, which was accomplished by coupling tpsens with conmin, an available NASA fortran program for constrained function minimization.
In-situ estimation of an acoustic source in an enclosure and prediction of interior noise by using the principle of vibroacoustic reciprocity
Authors: Kim Bong-Ki , Ih Jeong-Guon
Published: October 2005

The volume velocity of an acoustic source can be widely used in determining the vibroacoustic transfer functions, in measuring the acoustic transfer impedances, and in finding the generated power of an acoustic source. Several techniques utilizing special experimental devices have been proposed for this purpose, including the laser velocimetry, the internal pressure measurement, and the face-to-face electroacoustic measurement. However, for a source in an enclosure with flexible walls, the vibroacoustic coupling should be considered, especially in the case of a loudspeaker source that has low internal mechanical impedance. The present method, which uses the principle of vibroacoustic reciprocity, can give a reasonable estimation of the transfer functions and can be used in determining the volume velocity of a source in situ. Because the present method does not require a special facility or the information on the source surface vibration, the method can be applied to any irregularly shaped source in a flexible enclosure. With the obtained vibroacoustic transfer functions, the interior noise field in an enclosure can be predicted by vectorial summation when the boundary points are excited by uncorrelated dynamic forces. The predicted internal pressure in an enclosure is in good agreement with the measured internal pressure even in the presence of sound absorbers inside the enclosure.
The active control of point acoustic sources in a half-space
Authors: Cunefare Kenneth A. , Shepard Steve
Published: October 2005

Analysis of active noise control applications generally neglect the presence of nearby reflective surfaces, such as a ground plane. The research presented in this paper examines the impact of the presence of a nearby reflective plane on the active control of sound radiated by a number of point sources. It is shown that when the sources to be controlled are within one wavelength of the reflective plane, be it rigid or pressure release, that the plane can significantly impact the control versus control under free-field conditions with the same source separations. The orientation of the noise sources and the control sources with respect to each other and to the plane also significantly influences the control. For sources more than one wavelength away from the reflective plane, the use of the simpler free-space analysis yields acceptable results as compared to using the more complex half-space analysis.
Finite amplitude standing waves in harmonic and anharmonic tubes
Authors: Gaitan D. Felipe , Atchley Anthony A.
Published: October 2005

Finite amplitude standing waves have been studied in closed tubes filled with air and driven by a piston at frequencies near 200 Hz. The tubes were driven at resonance generating standing waves with amplitudes of up to 160 dB re: 20 μPa. The main objective was to measure the dissipation of energy by the fundamental frequency and the higher harmonics, as well as by other nonacoustic mechanisms. A formulation developed by Coppens and Sanders [J. Acoust. Soc. Am. 58, 1133–1140 (1975)] using a single nonlinear equation to describe standing waves in cavities of arbitrary resonance frequencies and quality factors was used successfully to predict the higher harmonics. In addition, the effect of detuning the tubes on the energy dissipation was measured in tubes with variable cross sections. It was found that the detuned tubes effectively suppress the energy transfer into (and energy dissipation by) the higher harmonics. It was also found that expanding rather than contracting the cross section of the tubes minimized the dissipation of energy through nonacoustic mechanisms.
Optimal array configurations for a Bartlett beamformer in an Arctic environment
Authors: Huston R. D.
Published: October 2005

Optimal or near-optimal array configurations for a vertical array in a shallow-water Arctic environment were determined using a Bartlett matched-field beamformer. A normal mode model was employed to calculate the acoustic field for a range-independent waveguide, and a simulated annealing (SA) algorithm was implimented to solve the combinitorial aspect of this problem. The cost function was designed to minimize sidelobes and the mainlobe width in the ambiguity surface, with the objective of optimizing the localization accuracy of the Bartlett beamformer. Exhaustive searches, which are possible for arrays with up to five hydrophones, confirmed the accuracy of array configurations from the SA method. An analysis of the range dependence of these solutions compares the localization accuracy from optimal and conventional uniform arrays for 8, 16, and 32 hydrophones at source ranges between 10 and 40 km.
The importance of memory when predicting annoyance on the basis of equal energy
Authors: Luz George A.
Published: October 2005

In 1981, CHABA published a report showing the annoyance for a 24-h day–night average sound level from sonic booms/blasts (measured with C) to increase at a faster rate than that from transportation noise (measured with A). In 1979, Luz and Lewis presented a theoretical argument that this difference was due to a difference in the loudness functions for the different noise sources. In 1992, Schomer etal. provided experimental proof for these differing loudness functions. A radical implication of Schomer etal.’s demonstration is that the equal energy rule is inappropriate for the assessment of heavy weapons noise and other types of explosions. A more conservative approach is that the equal energy rule is a description of human memory for the annoyance of noise. Using examples from past studies, an attempt is made to define the limits over which memory can be expected to conform to the equal energy rule.
The apparent duration of the restored speech segments
Authors: Tsuzaki Minoru , Kato Hiroaki , Tanaka Masako
Published: October 2005

To investigate how the auditory mechanism restores the noise-replaced speech segments, the apparent durations for the perceptually restored speech were measured. The results were obtained that supports the hypothesis that the subjects restore the ‘‘missed’’ part of speech based on the internal template whose temporal structure corresponds to the ‘‘original’’ sample. The threshold of duration discrimination was measured using an up-and-down two-interval task. In one interval, a ‘‘standard’’ stimulus was presented that had the temporal structure of the natural sample. In the other interval, a ‘‘comparison’’ was presented in which the third mora was either lengthened or shortened. There were four conditions in a two-factorial design. The first factor was the noise replacement in the comparison, depending on whether the part of the modified segment in the comparison was replaced by a noise. The second factor was the noise replacement in the standard. In the lengthening direction, only the noise replacement in the comparison resulted in the increment of the discrimination threshold irrespective of the noise replacement in the standard. This suggests that only the noise replacement in the modified part is effective in the perceptual judgment of the durations.
Matched-mode processing (MMP) vertical slice tomography
Authors: Shang E. C. , Wang Y. Y.
Published: October 2005

For a practical global scale ocean acoustic thermometry system, information given by vertical slice tomography might be the most fundamental outcome because 3-D mapping is difficult in such a case. Usually, vertical slice modal tomography gives only the ‘‘range-averaged’’ information. Moreover, the ‘‘range-averaged’’ information of sound-speed profile or temperature profile has bias due to the nonlinearity of acoustic travel time. In this talk, the bias has been discussed and the possibility of estimation range-dependent information by using a ‘‘differential’’ MMP vertical slice tomography scheme is investigated. Some numerical simulations will be presented. [Work supported by DARPA and NOAA.]
Application of a maximum-likelihood processor on acoustic backscatter for the estimation of the seafloor roughness parameters
Authors: Michalopoulou Zoi-Heleni , Alexandrou Dimitri
Published: October 2005

The objective of this work is seafloor characterization using a method that takes advantage of the statistical properties of bottom reverberation and employs maximum-likelihood estimation to obtain estimates for the seafloor parameters. The Helmholtz–Kirchhoff model for backscatter is here used to link the angular dependence of backscattering strength to the correlation properties of the seafloor roughness. The suggested estimation procedure is applied on simulated backscatter data and on real data recorded over Horizon Guyot and Magellan Rise by the bathymetric system Sea Beam. The real data estimation results are compared to curve fitting estimates acquired by the same data sets presented by Moustier and Alexandrou [J. Acoust. Soc. Am. 90, 522–531 (1991)]. [Work supported by the Office of Naval Research, Code 1125GG, through Contract No. N00014-93-I-0049.]
Coarticulatory information in word recognition: A phonetic priming study
Authors: Rossi Robert , Burton Martha , Jongman Allard , Sereno Joan
Published: October 2005

A series of experiments was conducted to investigate whether subphonemic coarticulatory information affects spoken word recognition. A phonetic priming paradigm was used in which isolated fricatives served as primes for target words beginning with a fricative. In particular, prime fricative segments ([s]i and [s]u), representing [s] excised from the vowels [i] and [u], respectively, were used as primes for the targets [si] and [su]. Acoustically similar prime conditions (prime and target fricatives had similar coarticulatory information) were contrasted to acoustically dissimilar prime conditions (prime and target fricatives had contrasting coarticulatory information). Preliminary results show that there was no difference in identification between targets that were preceded by similar as compared to dissimilar primes. Interestingly, however, target identification was speeded when preceded by an identical prime-target match, that is when the prime and target fricatives were the exact same tokens. Results will be discussed in terms of the role of subphonemic information in word recognition.
Alternative scoring systems for the modified distinctive features difference test [DFD(m)]
Authors: Anderson Penny A. C. , Jamieson Donald G.
Published: October 2005

The modified distinctive features difference test [Cheesman etal., Proc. Int. Conf. on Spoken Lang. Processing (1992)] measures the ability to identify the 21 dominant English consonants in an /(inverted vee) / context. The test contains 84 stimuli (21 sounds, each spoken by four speakers of Central Canadian English). Target sounds are normally presented in a noise background. The possibility that the sensitivity of the test increases when listener’s DFD(m) confusion errors are scored was examined in terms of phonetic features rather than in the more traditional, whole-item terms. Several alternative scoring approaches were examined: the classical place, manner, and voice distinction and those systems used by Chomsky and Halle (1968), Miller and Nicely (1955), and Feeney and Franks (1982). Scoring using a phonetic feature system does offer certain advantages over whole-item scoring. [Work supported by NSERC and the Ontario Ministry of Health.]
Distribution of sound levels for consonants and vowels within individual frequency bands
Authors: Turner Christopher W.
Published: October 2005

While it has been long known that vowels are, in general, more intense than consonants in naturally spoken speech, this statement is based upon the overall sound levels of the phonemes. The purpose of the present study was to determine the sound levels of consonants and vowels within individual frequency bands, with potential application to the provision of consonant audibility to hearing-impaired patients via amplification. The NST speech materials were digitized and subjected to 1/3 octave-band analysis in contiguous 23-ms samples. The samples were then classified as vowels or consonants, based upon waveform and spectral analysis. A large majority of the samples were vowels, reflecting their greater duration. The long-term consonant spectrum was flat, in contrast to the more familiar low-pass shape of the traditional speech spectrum. In the higher-frequency bands, consonant levels were in many cases more intense than the vowels. [Work supported by NIDCD Grant No. 00377.]
Approximate methods for shallow water acoustics with solid sea beds
Authors: Zhang Z. Y. , Tindle C. T.
Published: October 2005

The reflection properties of representative shallow water solid sea beds can be reproduced by several simple approximations. An ‘‘equivalent fluid’’ with real parameters can be found provided the shear wave speed in the bottom is less than about 600 m/s. An equivalent fluid with complex density is useful if the shear wave speed is less than about 1000 m/s. A perfectly reflecting boundary placed at a ‘‘complex effective depth’’ gives a very simple approximation, again for shear speeds up to 1000 m/s. The acoustic field at long ranges is determined by reflection at low grazing angles and is reproduced well by all three approximations. In all cases algebraic expressions are given for the various parameters. If the complex effective depth is matched to each mode by iteration it provides a rapid means of finding exact normal mode eigenvalues for both the trapped and leaky modes. All normal modes are leaky for a soft solid sea bed and have complex parameters even when there is no attenuation.
Effect of extended training on /r/ and /l/ identification by native speakers of Japanese
Authors: Yamada Reiko A.
Published: October 2005

It has been reported (1) that being exposed to the American English (AE) speaking environment in adulthood has less of an effect on the perception of AE /r/ and /l/ sounds for native speakers of Japanese than experience at younger ages, and (2) that laboratory training of those sounds on adult-Japanese has little effect. Recently, however, Logan etal. [J. S. Logan etal., J. Acoust. Soc. Am. 89, 874–886 (1991)] and Lively etal. [J. Acoust. Soc. Am. (1993)] showed that identification training with natural tokens produced by multiple talkers was effective in improving Japanese listeners ability to identify /r/ and /l/. In the present paper, the effect of extended training was examined. Subjects were adult native speakers of Japanese with no experience in living abroad. The training procedure was identical to Lively etal.’s procedure, except that subjects were trained for 45 sessions and were given two midterm tests. The results showed that (1) most of the subjects, even those whose score was around 60% in the pre-test, improved to more than 85% correct in the post-test, (2) some of the subjects kept improving throughout the 45 training sessions, while the others met asymptote with less training, and (3) the training effect in all the subjects generalized to the identification of new words produced by both familiar and unfamiliar talkers. The results are discussed in the context of recent theories of perceptual learning and development of phonological categories. [Work supported by ATR.]
Profile analysis in the spectro-temporal domain
Authors: Houtgast T. , Bronkhorst Adelbert W.
Published: October 2005

In this study on energy profile discrimination, the basic sound consists of five Gaussian-shaped tone pulses (wavelets). The choice of the timing and the frequencies of the individual wavelets is such that they are always arranged in a linear array in the log(f)-t spectrogram, with the orientation of the array as an important parameter (horizontal, vertical or any oblique orientation). An additional parameter of these five-wavelets arrays is the mutual separation between the wavelets. For a given orientation and separation, the reference sound contains all five wavelets with equal energy, while in the target sound the (relative) energy of the middle wavelet is reduced: The just-detectable decrement of the middle wavelet is determined with a standard adaptive 2AFC procedure, including a roving-level paradigm. This form of profile analysis with the present five-wavelets arrays shows that (1) the performance is better with a purely temporal pattern (horizontal array) than with a purely spectral pattern (vertical array), and (2) for some specific oblique orientations of the array the performance is extremely poor, with just-detectable decrements of the middle wavelet of the order of 20 dB.
External system modeling: An approach to minimizing vibroacoustic model sizes for design evaluation
Authors: Gardner B. K. , Bolton J. S.
Published: October 2005

Numerical vibroacoustical models of dynamic systems can easily become so large that they are impractical when used to analyze alternative system designs. Hence, when evaluating designs for single sub-components of a large system, the analysis is often limited either to that sub-component combined with idealized boundary conditions, or to the sub-component and a small portion of the rest of the system (i.e., the exterior system). In this paper a technique, based on the receptance method, is presented that allows a model of the complete system to be replaced by a complete model of the sub-component combined with a minimal model of the exterior system. Thus the insitu dynamics of a particular sub-component may be evaluated without having to solve the entire system. This approach allows sub-component designs to be assessed quickly so that the merits of many potential designs may be evaluated. The assumptions required by this approach are: steady-state conditions, linearity, and that the forces acting on the external system are unaffected by changes in the sub-component. The external system model may be obtained either numerically or experimentally. The proposed approach is demonstrated here analytically using a system of beam-like elements.
Acoustics of bass handbells
Authors: Rossing Thomas D. , Mansell Edward R.
Published: October 2005

Handbells tuned to frequencies below 100 Hz radiate inefficiently, since their fundamentals lie several octaves below the coincidence frequency for bending waves. In order to obtain a higher radiation efficiency and thereby enhance the sound of bass handbells, Malmark has created a new bell design using aluminum rather than bronze. The acoustical properties of two G1 bass handbells, one of aluminum and one of bronze, are compared. The aluminum bell radiates an enhanced fundamental, as expected, and a much stronger third harmonic as well. Both bells radiate a strong sixth harmonic, which is attributed to parametric radiation from the (3,0) mode, which is tuned to three times the fundamental frequency [T. D. Rossing and H. J. Sathoff, J. Acoust. Soc. Am. 68, 1600 (1980)]. The aluminum bell not only gives an enhanced bass tone, but it is considerably lighter and easier to handle than the bronze bell.
Sonic boom/animal stress project report on elk, antelope, and Rocky Mountain bighorn sheep
Authors: Bunch Thomas D. , Workman Gar W.
Published: October 2005

The animal/noise project was initiated as a result of a proposed extension of the Air Force Gandy supersonic range (MOA) in western Utah and eastern Nevada. The research was conducted at the Utah State University Green Canyon Ecology Center, and at Gold Hill, in the desert of northwestern Utah. The experimental animals included elk, antelope, and Rocky Mountain bighorn sheep. These animals were instrumented with heart rate and body temperature transmitters, which were surgically implanted in the animals. The animals were released in large enclosures, and in some cases were released to the wild for disturbance tests. This was done to determine effects of various disturbances on heart rate and to establish a baseline physiologic database of normal heart rate and body temperature. The animals were subjected to various types of disturbances, including people on foot, motorcycles, four-wheeled vehicles, fixed wing aircraft, helicopters, and F-16 jet aircraft flown subsonic and supersonic, etc. These projects indicated that animals habituated to most disturbance factors in a short period of time. The exceptions included people on foot who entered the research enclosures where the animals were kept; fixed wing aircraft at low levels of flight; and helicopter flights at low elevations near the animal enclosures. The animals habituated to subsonic and supersonic jet overflights after about four passes over the animals. This habituation seemed to be permanent, as these same animals did not respond when tested at a later date.
A generalized beamformer based on a spatial bispectrum
Authors: Sullivan Edmund J. , Edelson Geoffrey S.
Published: October 2005

The bispectrum is the expected value of the third-order cumulant of the data sequence of a signal in either space or time. Much analysis based on the bispectrum has already been carried out in the time domain, where information regarding the stationarity, linearity, and Gaussianity of the signal series can be analyzed. In this paper, it is shown that these concepts can be directly applied to the spatial domain, resulting in a generalization of the standard k-ω beamformer. It is shown that the ability of the bispectrum to indicate nonstationarity in the data series allows this generalized beamformer to account for nonplanar aspects of the incoming signal wave front, thereby allowing for source localization in which bearing and range estimation evolve in a self-consistent framework. Thus bearing estimation and wave front curvature ranging appear as special cases. It is also shown that the technique is applicable to the analysis of more complicated propagation scenarios such as normal mode propagation.
Experimental determination and theoretical prediction for the frequency compromise in bowed string and wind instruments
Authors: Boutillon Xavier , Faure Charles-Auguste
Published: October 2005

In musical instruments, eigenfrequencies of resonators (strings, pipes) are generally not strictly harmonic. When the oscillation is sustained by means of an external nonlinearity (bow,reed) the harmonic frequencies of the vibration cannot fully coincide with these eigenfrequencies. The notion of reactive power balance brings a new insight on the frequency compromise for a given spectrum. On the violin, flattening of the pitch when the bow pressure increases may be explained and quantitatively predicted by this sumrule [X. Boutillon, J. Acoust. Soc. Am. 90, 754–763 (1991)]. Measurements of the frequency compromise (without and with flattening) will be presented on a bowed string and compared with theoretical predictions. Experimental results shed light on one aspect of the rosin friction curve between the bow and the string. The same approach is relevant on wind instruments and might give information on the reed dynamical properties. [Work supported by CNRS and French Ministry of Culture.]
Psychoacoustic models of group signal detection
Authors: Sorkin R. D. , Dai Huanping
Published: October 2005

A number of auditory scientists have proposed models for the multi-channel signal detection task: an observer must detect a signal that has components in several partially correlated channels (spectral, spatial, or temporal). This task has been reframed as a group detection problem: an array of observers must detect a signal by combining the observations of the individual detectors. It is shown how the performance of the ideal group detection system depends on the number of detectors, the correlation among detector observations, and the distribution of individual sensitivities. Also considered are some cases where the group decision is based on the binary outputs of the individual detectors. The results are applicable to a variety of different types of group detection systems. [Work supported by AFOSR.]
Age-related changes in mechanoreceptor-specific vibrotactile thresholds for normal hands
Authors: Brammer A. J. , Piercy J. E. , Nohara S. , Nakamura H. , Auger P. L.
Published: October 2005

Mechanoreceptor-specific vibrotactile perception thresholds have been measured at the fingertips using the tactometer [A. J. Brammer and J. E. Piercy, in Proc. UK Informal Group Meeting on Human Response to Vibration, Buxton (September 1991)]. Thresholds were obtained from the left and right hands of healthy male white-collar workers, aged from 25 to 73 years, without signs, symptoms, or history of neurological disease, or of exposure to vibration. Groups were formed from: (1) oriental professionals (mean age 34±5.9 years, N=24); (2) occidental professionals (mean age 40±5.0 years, N=18); and (3) oriental workers (mean age 62±5.6 years, N=24). A preliminary analysis of the data suggests that there is little effect of age on thresholds mediated by the SAI and FAI receptors. Thresholds mediated by the FAII receptors decreased in sensitivity at a average rate of 2.6 dB per decade increase in age. There are also a tendency for the SAI and FAI receptor thresholds in groups 1 and 3 to be more sensitive than those in group 2.
Age-related changes in mechanoreceptor-specific vibrotactile thresholds with exposure to hand-transmitted vibration
Authors: Coutu-Wakulczyk G. , Brammer A. J. , Piercy J. E.
Published: October 2005

Mechanoreceptor-specific vibrotactile thresholds have been determined at the fingertip of the third finger (both hands) of manual workers using the tactometer. Age-related changes in thresholds were examined in 82 hands exposed to vibration, which were classified according to the Stockholm Workshop Stages of the hand-arm vibration syndrome (HAVS), and 38 unexposed hands. The age of subjects ranged from 19 to 54 years, and the exposure to vibration ranged from 2 to 27 years. Thresholds from asymptomatic, unexposed persons were employed to separate the influence of aging from that due to vibration exposure. A preliminary analysis of the data suggests that age does not influence the development of either the sensorineural symptoms or vascular signs of HAVS, a finding of consequence to the management of workers’ activities in the workplace.
Undercooling and solidification of acoustically levitated molten drops
Authors: Ohsaka Kenichi , Trinh Eugene H.
Published: October 2005

Undercooling of a liquid prior to the nucleation of a solid is necessary for producing novel microstructures including metastable phases that are not formed by conventional solidification processes. Because containerless techniques such as acoustic levitation are capable of achieving a high undercooling level of liquids, they are under consideration as possible techniques for material processing on Earth and in space. For an application of acoustic levitation on Earth, however, there is a strong concern that ultrasound may prematurely initiate the nucleation of the solid and prevent further undercooling in experiments designed for the study of solidification in the deeply undercooled liquid. An experiment using a model material with a single axis levitation system shows an effect of ultrasound as the occasional nucleation of the solid at low undercooling levels. This premature nucleation may be explained by thermodynamic considerations which predict an increase in effective undercooling of the liquid upon the collapse of cavities. [Work supported by NASA.]
Minimally intrusive occupied hall measurement techniques
Authors: Allen Jont B. , Kirkegaard Dana L. , Puria Sunil
Published: October 2005

With high-powered portable computers and digital signal processing boards it is possible to make high-quality, broadband impulse response measurements that are minimally intrusive to audience and performers. In January 1992 the authors designed a stimulus for measurements at Symphony Hall, Boston that permitted stimulus levels near or below the audience’s masked threshold. Synchronous averaging of the response increased the signal-to-noise ratio and minimized inaccuracies due to random audience and performer movement. Subsequent measurement sessions in Davies Symphony Hall, San Francisco and the Academy of Music, Philadelphia provided the opportunity to fine-tune the stimulus type, number of averages, and various source characteristics, including: spectrum, level, directionality, and placement relative to intrusion upon audience and performers. Source directionality and placement were selected to optimize convolution with recordings of solo violin. Typically, measurements are made at levels above the masked threshold following a brief announcement. There are interesting exceptions when occupied hall measurements can only be made at levels near or below the masked threshold. In either case, occupied hall measurements must be designed to minimize the intrusion upon the concert setting, particularly when working with major symphony orchestras.
Presbyacusis: An overview
Authors: Mills John H.
Published: October 2005

Presbyacusis is defined operationally as age-related hearing loss. It is a common problem and will become even more prevalent in the future. Age-related histopathological changes have been discovered at nearly every location in the aging auditory system from the external ear to the cochlea to the auditory brainstem and temporal lobe. Even for a given person, histopathology can be observed at multiple sites. Moreover, for individual human subjects it remains difficult, if not impossible, to separate age-related hearing loss from hearing loss caused by exposure to noise and other ototoxic agents (sociocusis), or from hearing loss caused by other disease processes (nosoacusis). Most of the research on presbyacusis can be placed into three categories: cross-sectional epidemiologic (audiometric surveys) studies; clinical studies with the emphasis on histopathology of the cochlea, psychophysics, and speech perception; and most recently, there have been a number of efforts to develop an animal model (mouse, rat, gerbil) of the aging human ear. Highlights from these research efforts will be presented with a focus on evoked potentials and masking in aging human and animal subjects. [Work supported by NIH DC00422.]
A comparison of synchronous and asynchronous analysis of speech
Authors: Jensen Grant J. , Strong William J.
Published: October 2005

Speech having a high signal-to-noise ratio and digitized at 16 kHz was used for the comparison. An ‘‘ideal’’ synchronous analysis was obtained by handmarking the speech events—voicing periods, plosive bursts, and so on. An asynchronous analysis was obtained from 25-ms Hamming windowed segments of speech stepped at 7.5-ms intervals. In both cases the speech sample—event or windowed segment—was Fourier transformed and displayed in a ‘‘trispectral’’ space. The synchronous analysis produced erratic event-to-event spectra for short voicing periods. The asynchronous analysis produced erratic segment-to-segment spectra for long voicing periods. It also tended to smear short-duration, transitional features. Various examples of trispectral plots obtained from the two methods will be shown for comparison.
Alternative procedures for spectral estimation
Authors: Kheirallah Issam , Jamieson Donald G.
Published: October 2005

This paper compares four alternative procedures for estimating the acoustical characteristics of speech and other complex signals: the fast Fourier transform (FFT), two autoregressive techniques (the autocorrelation and modified covariance methods), and the Cone–Kernel method. All four techniques are now widely available to researchers in Version 4.0 of the CSRE (Canadian Speech Research Environment) software system. FFT spectral estimates are characterized by many known tradeoffs: good frequency resolution is obtained at the expense of good time resolution, and vice versa. Autoregressive methods overcome some of the inherent limitations of the FFT method, but still use a quasi-stationary approach to analyze nonstationary signals such as speech. The Cone–Kernel method offers the opportunity for both good frequency and good time resolution, and cancels many of the cross terms that have made it difficult to interpret previous approaches based on the Wigner distribution. Examples of applying the various analysis procedures to signals will be shown, including situations where the Cone–Kernel approach facilitates the interpretation of certain details of the speech signal.