bluuebunny/crossref_metadata_2025 huggingface dataset:
Intensity discrimination in forward masking.
Authors: Plack Christopher J. , Viemeister Neal F.
Published: October 2005

Recently, Zeng etal. [F-G. Zeng, C. W. Turner, and E. M. Relkin, Hear. Res. (submitted, 1991)] measured intensity discrimination for 30-ms tone pulses presented 100 ms after a 90-dB narrow-band noise. They found that performance was worse, compared to a control condition without the noise, for medium pedestal levels but not for high or low levels. They suggested that this effect was related to the finding that low spontaneous rate (SR) auditory nerve neurons take longer to recover from adaptation than do high-SR neurons [E. M. Relkin and J. R. Doucet, Hear. Res. (submitted, 1991)]: 100 ms after the noise, the high-SR neurons have recovered while the low-SR neurons still have elevated thresholds. The intensity of a signal falling between the saturation level of the high-SR neurons and the elevated threshold of the low-SR neurons will be poorly determined by the system and the DL will be high. A problem with this interpretation is that subjects may use channels tuned to a different frequency than the signal frequency. Theoretically, it should always be possible to choose a channel for which the signal level is within the dynamic range of the high-SR neurons. In the study reported here, the experiment of Zeng etal. was replicated with a notched noise presented simultaneously with the signal to prevent off-frequency listening. Contrary to predictions, adding the notched noise removed the ‘‘mid-range bump’’ almost entirely. The possible role of suppression in this result will be discussed. [Work supported by NIDCD DC00683.]
Active control of interior noise using piezoceramic actuators.
Authors: Silcox R. J. , Lefebvre S. , Beyer T. B. , Metcalf V. L.
Published: October 2005

Active control of aircraft interior noise has recently received increased emphasis as an effective, lightweight noise control approach. Flight tests have demonstrated 10 to 15 dB of noise reduction using distributions of interior acoustic sources. However, to achieve control over the first three to five blade passage harmonics, actuator numbers ranging from 16 to 32 or more have been used. Additionally, the optimum distribution of actuators changes between those frequencies associated with the first one or two harmonics and the higher harmonics. Recent work at NASA Langley has investigated the use of piezoceramic patches bonded to the shell surface of a large-scale composite fuselage model. These were used as force actuators in an active control system where the interior acoustic pressure was minimized using a least-means-squares algorithm. Results show an 8- to 15-dB global noise reduction for a variety of test conditions. The results are compared for different actuator numbers, locations, and excitation conditions. Generally, it was found that in-plane force excitation is more effective for controlling the required low-order azimuthal modes. Also, frame-mounted actuators were found to be effective under certain conditions. Finally, the implementation of the control system and the transducer arrangement will be related to the mechanisms controlling the noise transmission and radiation coupling.
Bistatic and monostatic scattering results off the coast of Portugal.
Authors: Preston J. R.
Published: October 2005

Estimates of ocean-bottom scattering strengths are presented as a function of range and bearing for a number of monostatic and bistatic geometries achieved during a SACLANTCEN sea trial off the coast of Portugal in September 1990. Area water depths ranged from 200 to greater than 5000 m. The receiver was a horizontal array of 64 elements spaced at 0.5 and 2 m. Source depths were about 100 m and receiver depths ranged from 90 to 150 m. Depth charges were used as sources, as were low-frequency cw pulses and linear FM pulses of various pulse durations and bandwidths. Received reverberation levels and scattering strength values are presented as functions of the estimated scatterer position on area bathymetry maps. Estimates of monostatic bottom scattering strengths versus grazing angle are given using Generic Sonar Model (GSM) to interpret the data. Finally, comparisons of measured reverberation and modeled reverberation are presented using GSM.
A physically motivated simulation technique for high-frequency forward scattering derived using specular point theory.
Authors: Funk Dale E. , Williams Kevin L.
Published: October 2005

A simulation technique using specular point theory (SPT) is developed to examine high-frequency signals forward scattered from a rough surface. SPT results in treatment of the forward scattered signal as a summation of point sources, a result convenient for many simulators. This method is used to derive the spatial coherence for an infinite ensemble of signals forward scattered from random surfaces with Gaussian wave number spectra. The results are compared with those of previously published methods. An SPT single realization procedure is formulated and implemented for frequencies of 30 and 300 kHz using a Gaussian spectrum approximation to the random rough surface. Both the spatial coherence and the temporal structure of finite ensembles of forward scattered signals are compared for the Gaussian case. The relation between the results for infinite and finite ensembles is then examined, and the practical implications and limitations of SPT for simulating forward scattering are discussed. [Work supported by NAVSEA with technical management by NOSC and ONT with technical management by NCSC.]
Surface loss, scattering, and reverberation in the split-step PE.
Authors: Schneider Hans G.
Published: October 2005

Moore-Head etal. [J. Acoust. Soc. Am. 86, 247–251 (1989)] have published a method to incorporate loss due to rough surface scattering into split-step PE codes. This is an approximate solution that will be discussed regarding the applicability in the presence of sound-speed gradients. The method has been extended by Dozier etal. [in OceanVariabilityandAcousticPropagation, edited by J. Potter and A. Warn-Varnas (Kluwer Academic, Dordrecht, 1991)] to include the incoherent scatter as well. Since this method is based on estimating the angular spectrum at the average sea surface, or more generally at any horizontal interface, it may well be utilized also for bottom roughness and reverberation. A simple scheme is outlined to compute the reverberation from a boundary as a function of range with results being compared to those from ray tracing codes. A more complex scheme for reverberation as a function of time is indicated. Both approaches are applicable for bistatic geometries as well.
Interpretation of structures in bioacoustic sections through the Gulf Stream.
Authors: Olson Donald B.
Published: October 2005

Bioacoustic cross sections through the Gulf Stream as part of the BIOSYNOP program have shown distinctive concentrations of fish and zooplankton in the front. These patterns with scales of order 10 km vary along the Stream in basic agreement with the locations of local frontogenesis and frontolysis associated with meandering. Here a basic model of the structure of Gulf Stream meanders and the frontogenetic process in them will be combined with some simple calculations of particle dispersion in the Stream. The distribution of passive free drifting particles is contrasted to particles that exhibit behavior. Behaviors involving vertical orientation tied to phototatic responses, maintenance of preferred thermal habitat, and horizontal swimming with response to either biological or physical cues are considered. The results of these analyses are used to quantify the influence of meanders on the distribution of organisms and on the manner in which the biome represented by the Stream is maintained.
Effects of wave shape, rise time, and duration on subjective response to sonic booms.
Authors: McCurdy David A.
Published: October 2005

A laboratory experiment was conducted to quantify the subjective response of people to sonic booms having different pressure signatures. The objectives were to (1) determine the effects of wave shape, rise time, and duration on subjective response; (2) assess the ability of different noise metrics to predict subjective response; and (3) compare ‘‘loudness’’ and ‘‘annoyance’’ as subjective response descriptors. The experiment was conducted in a computer-controlled, man-rated sonic boom simulator capable of reproducing user-specified pressure signatures for a wide range of sonic boom parameters. One-hundred fifty sonic booms, representing different combinations of two wave shapes, four rise times, seven durations, and three levels, were presented to each of 72 test subjects. One-half of the subjects made judgments of ‘‘loudness’’ while the other half judged ‘‘annoyance.’’ Analyses of the judgments examine the effects on annoyance and loudness of wave shape, rise time, duration, and level. The ability of different noise metrics to predict annoyance and loudness is also examined.
Effect of a modulated cue on envelope-frequency discrimination.
Authors: Buus So/ren , Pan Chi
Published: October 2005

The purpose of this study was to investigate how correlated or uncorrelated modulation at one carrier frequency (the cue) affects discrimination of envelope frequency at another carrier frequency (the signal). Discrimination thresholds Δfe,DL were measured in four normal listeners using an adaptive procedure with a 3I, 2AFC paradigm. The signal carrier always had a frequency of 2000 Hz and a level of 60 dB SPL. Envelope frequencies were produced by analog multiplication of the sinusoidal carrier by a sinusoid with frequency equal to half the desired envelope frequency fe. The standard signal always had fe equal to 80 Hz. Experiment 1 shows that Δfe,DL is always lower with a correlated cue than with an uncorrelated cue, and in most cases lower than without a cue. On the average, Δfe,DL is about 2 Hz without a cue; with a correlated cue it increases from about 0.4 Hz to about 1 Hz as the cue frequency increases from 2400 to 8000 Hz and is nearly the same for cue levels of 50 and 60 dB SPL. With an uncorrelated cue, Δfe,DL’s decrease from about 10 to 2 Hz. Experiment 2 shows that a cue below or two cues surrounding the signal are as effective as a cue above the signal for a cue-signal carrier frequency ratio of 1.2, whereas they tend to help less and interfere more for cue-signal carrier frequency ratios of 2 and 4. Overall, these results indicate that the auditory system is very effective in comparing envelopes at different carrier frequencies. [Work supported by NIDCD.]
Detecting temporal asynchrony in multitonal complexes.
Authors: Zera Jan , Green David M.
Published: October 2005

In one experiment, the asynchrony threshold for single harmonics and for groups of 3, 5, and 10 adjacent harmonics in a 20-tone harmonic complex was measured. In a second experiment, the asynchrony threshold for a single component in complexes consisting of 5, 10, and 20 logarithmically spaced components was measured. For the standard stimulus, all components of the complex were gated on and off together. An asynchronous stimulus was created by gating a target set, consisting of one or more components, either before or after the remaining components of the complex. Asynchrony was introduced at either the onset or the offset of the complex. The asynchrony threshold was measured as a function of the frequency of the target set. These functions are quite different for the four different asynchronous conditions. In general, however, asynchrony is better detected at the onset rather than at the offset and when the target set starts before or ends after the remaining components. [Work supported by the NIH and a Fulbright fellowship.]
Discrimination of redundant spectral-temporal cues. I. Interindividual differences.
Authors: Espinoza-Varas Blas , Monahan Caroline B.
Published: October 2005

Interindividual differences in speech-processing ability of hearing-impaired listeners have been attributed to differences in the ability to process residual sets of highly redundant speech cues (e.g., Walden, 1984). This paper describes interindividual differences in listeners’ ability to discriminate redundant increments in the frequency and duration of pure tones. The stimuli comprised pairs (T1, T2) of 1500-Hz, 80-ms, 66-dB SL tones separated by a 60-ms silent interval [B. Espinoza-Varas, J. Acoust. Soc. Am. 74, 1687–1694 (1983)]. In a three-interval, 2AFC task, listeners discriminated a ‘‘standard’’ pair (interval 1) from a ‘‘comparison’’ pair (interval 2 or 3) containing increments in the duration (ΔT) of T1 and/or in the frequency (ΔF) of T2. Discrimination thresholds were interpolated from psychometric functions for ΔT alone, ΔF alone, and combinations of ΔT and ΔF. In highly trained listeners with normal hearing sensitivity (n=8), three main patterns of performance were observed: (a) multicue processing with accurate discrimination for both ΔT and ΔF (n=2); (b) single cue processing (selective attention) with accurate discrimination for only one kind of increment, usually ΔT (n=4); and (c) chance discrimination for both ΔT and ΔF (n=2). There are large interindividual differences in listeners’ ability to attend to and discriminate redundant increments in frequency and duration. [Work supported by OCAST Grant HSO-005 and Presbyterian Health Foundation.]
General characteristics of the finite element and boundary element methods.
Authors: Bernhard Robert J.
Published: October 2005

Numerical methods can be characterized by the basis used, the criterion of fit used, and the approximations to the variational formulation which must be made to implement the numerical approximation. Finite element methods usually use a polynomial basis and the criterion of fit is a domain integral variational statement. The boundary element methods usually use a free-space Green’s function as a basis. The criterion of it is usually a collocation method for satisfying a boundary integral equation for discrete specified boundary conditions. For both the finite element and boundary element methods, discretization, numerical mapping, and integration procedures are potential sources of significant error. The characteristics of structural acoustic applications of both the finite element and boundary element methods will be identified and contrasted to analytical methods. It will be demonstrated that numerical methods and analytical methods have different strengths and weaknesses and that the methods should be considered complementary.
Design of ultrasonic composite horns using finite element analysis.
Authors: O’Shea Kevin
Published: October 2005

The design of ultrasonic composite horns tuned to resonate at 20 kHz in an axial mode is investigated. Composite horns use a back driver that is a tuned half-wavelength at 20 kHz. Fastened mechanically to the back driver are discrete front drivers that are also tuned members. The positioning of the front drivers along the back driver face significantly impacts the performance of the overall horn. The effect of this positioning is examined using finite element analysis (FEA). Horn surface uniformity, for both the back and front drivers, and frequency distribution for the composite horn is looked at for various front/back driver combinations. Based on the FEA iterations an optimum front/back driver configuration is prescribed and prototyped. Results from the FEA are compared with experimental data from the composite horn.
Side-branch resonators for controlling industrial pressure blower noise.
Authors: Watson Eric T. , Hoover Robert M.
Published: October 2005

Process industries commonly use fans and pressure blowers that operate at pressures of 5 psig and flow rates around 5000 cfm. These fans and blowers often create some of the highest localized sound levels in an industrial environment. Centrifugal blowers create blade passage tones that produce intense sound levels in the range of 150–160 dB(A) at the outlets, due to high-pressure volume flow and blade passage rate. A case study is presented to show the effectiveness of the old idea of the side-branch resonator in dramatically reducing the fundamental frequency of the blade passage tone [W. H. Ihde, Noise Control Eng. 5(3), 131–135 (1975)]. Fundamental tone reductions of 25–30 dB have been observed in laboratory mock-ups for a single side branch, and a reduction of 36 dB has been observed in a practical industrial application using two side branches. For constant-frequency tones, the side-branch resonator offers an inexpensive alternative to active noise control, and is effective at very intense sound levels and extreme temperatures.
Construction of a hands-on museum exhibit on physical acoustics by high school students.
Authors: Bertucci Tony , Van Doren Thomas W.
Published: October 2005

High school students at the LBJ Science Academy constructed a hands-on acoustic levitation exhibit for Discovery Hall, an interactive science museum in Austin, Texas. In addition to the levitation apparatus itself, the exhibit includes posters that explain fundamental principles associated with acoustic levitation, e.g., vibration, resonance, standing waves, radiation pressure, etc. The project was sponsored by the Acoustical Society of America through an initiative of the Committee on Education in Acoustics to involve high school students in science projects based on acoustics. A review of the project will be presented in this paper. (The donation of a loudspeaker by JBL is also gratefully acknowledged.)
Loudness of tones that continuously change in level: Range-level effects.
Authors: Schlauch Robert S.
Published: October 2005

The loudness of tones that increase and decrease continuously in level was studied. In a magnitude-estimation task, ten subjects estimated the loudness of continuous and gated 1000-Hz tones that increased and decreased continuously in level in 180 s. Two ranges of stimulus level were used: 30–70 and 50–90 dB sound-pressure level (SPL). For the low-level conditions, the results are essentially identical to those of Canevet and Scharf [J. Acoust. Soc. Am. 88, 2136–2142 (1990)], who restricted their stimulus range to these levels. Tones that increased in level changed in loudness as a function of SPL at a slower rate than tones that decreased in level. For the high-level conditions, the same result was obtained, but the magnitude of the difference among conditions is smaller. Loudness balances, which are not affected by number biases, were used to measure the magnitude of the differences among a subset of the conditions. The average difference in loudness for extreme conditions at the lowest level is 9 dB. This result lends additional support to the notion that the observed effect is due to sensory adaptation.
Measurements of acoustic wave scattering due to sea bottom roughness and sub-bottom sound-speed fluctuations.
Authors: Turgut Altan
Published: October 2005

An eight-element hydrophone array and an omnidirectional source were used for the bottom scattering measurements within the frequency range of 2–20 kHz. The reverberant tail of a Ricker pulse or a gated cw pulse were used for the backscattering measurements. Volume fluctuations of sound speed were measured as deep as 5 m by a newly developed source and hydrophone array penetrators. The penetrators were deployed 5–10 m apart to obtain a tomographic image of vertical cross section of sub-bottom. A nonlinear ray tracing and inversion scheme was used to calculate the sub-bottom sound-speed fluctuations and two-dimensional wave-number spectra. Penetration depths of the acoustic signals were also measured by using the same system. Preliminary results of the measurements of bottom backscattering and sub-bottom sound-speed fluctuations indicate that sub-bottom volume scattering may dominate the bottom roughness scattering in case of large fluctuations of sub-bottom sound speed and large penetration depths.
Description and classification of seafloor terrains using two-dimensional spectra models of bathymetry.
Authors: Fox Christopher G.
Published: October 2005

A two-dimensional spectral model of bathymetry developed by Fox and Hayes [Rev. Geophys. 23(1), 1–48 (1985)] is applied to gridded sea beam data from the central Juan de Fuca Ridge in the northeast Pacific Ocean. Parameters of the model corresponding to (1) isotropic (nondirectionally dependent) roughness, (2) anisotropic (directionally dependent) roughness, (3) orientation of the anisotropic component, and (4) spectral rolloff (∼fractal dimension) are derived by fitting the model surface to two-dimensional amplitude spectra of bathymetry determined on a regular grid over the study area. Each term of the model is individually mapped and compared to ground truth data from SeaMARC-I sidescan sonar imagery. Parameters of the model clearly define the contrast between constructional volcanic terrain (rough, isotropic, with high fractal dimension) and tectonic extensional terrain (smoother, anisotropic, with low fractal dimension). An agglomerative, hierarchical cluster analysis is applied to the data, independent of spatial information, to delineate groups of spectra with similar characteristics. Distinct, mappable regions, corresponding to volcanic and tectonic provinces, are objectively determined. Also, coherent subregions of consistent spectral properties occur within the larger volcanic/tectonic divisions. The classification of large data sets, such as the entire Juan de Fuca Ridge system, can best be accomplished through the use of apriori techniques, such as k-means clustering, which requires the input of predefined characteristics for bathymetric provinces.
Determination of fine-scale bottom roughness using combined optical and acoustical sensing.
Authors: Stewart W. Kenneth
Published: October 2005

Seafloor characterization work in progress at the Deep Submergence Laboratory takes advantage of a multiscale suite of optical and acoustic sensors deployed from towed and remotely operated vehicles. A long-term goal is the automated segmentation and classification of undersea terrain. Fine-scale data of small areal extent are used in the interpretation and ground truthing of coarser, larger scale data sets, which in turn are applied to other measurements of increasing scale and decreasing resolution: Camera and laser bathymetry are used for the ground truthing of high-frequency (e.g., 200–500 kHz) swath-bathymetric sidelook sonars; both optical and precision acoustical data serve for the interpretation and validation of intermediate-frequency sidelook data. Under development is an iterative technique, with the goal of improving classification results. At the first iteration, knowledge of sensor and seafloor geometry is combined with acoustic backscatter data to estimate a regional scattering function. This function is then applied to the raw amplitude data for removal of a deterministic component that depends on the bottom slope. The resultant map of acoustic albedo is segmented, a local scattering function is estimated within each segment, and the process is repeated until a measure of convergence is satisfied.
Seafloor bottom roughness at meter to decimeter scales from acoustic side-looking sonar imagery combined with stereo photography.
Authors: Ryan William B. F. , Pratson Lincoln
Published: October 2005

The crestal area of the East Pacific Rise is comprised of a volcanic terrain of very young age. Imagery obtained with a bilateral side-looking sonar operating at 30 kHz across swaths of 1 to 5 km in width portrays a hummocky seabed consisting of mounds, pits, fault escarpments, and fissures. Because the sonar was towed at altitudes <10% of the swath width, much of the seafloor insonification is at relatively low grazing angles. Consequently, seafloor relief of low amplitude is capable of casting acoustic shadows. The high signal-to-noise performance of the sonar permits the shadows to be reliably detected during signal processing. Shadow widths, when combined with grazing angle, are estimators of local seafloor feature relief. In the same terrain, stereo photographs exist. Each stereo pair covers roughly 10 square meters of the seabed. The parallax geometry for each picture is scaled with laser beams. The films are scanned at a picture element resolution of 2 mm. Using region matching techniques, local relief is extracted. The scaling relationships between the relief (wavelengths and heights) measured from the photographs and that extracted from acoustic shadows will be discussed and compared to that extracted from multibeam echo sounders.
Distribution of sediments on a rough seafloor.
Authors: Jordan Thomas H. , Webb Helen
Published: October 2005

Sedimentation is the primary modifier of the small-scale topographic roughness generated by volcanic and tectonic processes in the vicinity of ridge crests. In this study, the effect of sedimentation on the statistical properties of seafloor roughness is quantified. The objectives are threefold: (1) to produce three-dimensional, geologically realistic models of seafloor structure for the numerical modeling of acoustic scattering, (2) to describe sedimentation as a nonlinear smoothing filter so that its effects on topographic data can be removed, thereby facilitating the study of ridge-crest processes, and (3) to set up inverse problems for utilizing topographic data in the investigation of post-depositional sediment transport. An efficient numerical algorithm has been developed for modeling the sediment distribution on very rough models of seafloor topography, based upon a cellular-automaton description of sediment-particle kinematics. The algorithm is applied to realizations of the five-parameter Goff–Jordan bathymetric model, from which the effects of sedimentation on the two-point and three-point correlation functions of seafloor topography are calculated. Variations in the kinematical parameters of the cellular automaton on the isopach structures and topographic statistics are investigated.
A simple method of calculating IACC and its utilization for measurement in a concert hall.
Authors: Nakajima Tatsumi , Yoshida Jun , Ando Yoichi
Published: October 2005

Cross-correlation values using a dummy head for 1/1 octave bandpass noise (125 Hz–8 kHz) and for each single sound direction were measured. Summing up the measured values with the weighting of the sound energy spectrum of a source signal, the interaural cross-correlation function (IACC) for the stational noise and nonstational music as well as speech is calculated. Calculated results are compared with the measured values obtained in the Boston Symphony Hall. Agreement with measured results is satisfactory for stationary noise and also for music. Thus the presented method of calculating IACC can be utilized for any sound source in a concert hall. Also discussed is the correspondence between the measured IACCs and the results obtained by a simulation of the sound field using the plan and cross sections of the hall.
Low-frequency measurement of porous material characteristics.
Authors: Champoux Yvan
Published: October 2005

Accurate measurement at low frequency for the surface impedance, the characteristic impedance, and the propagation constant of porous materials is studied in this work. The recent round-robin test program [ASTM Committee E33, Res. Rep. No. RR:33-1006 (1989)] has confirmed that at 250 Hz and below, the results of scattering are very important. In this study, new techniques have been adapted or developed to improve the low-frequency measurement obtained with a modified standing wave apparatus. Two microphones are used for the surface impedance and it is shown that a third one, located in a cavity behind the material, is required for the measurement of the characteristic impedance and the propagation constant of thick samples of high flow resistivity. Extension tubes are used to adjust the microphone spacings and to provide the required calibration cavities. Accurate measurements were obtained down to 50 Hz for different ‘‘model materials’’ and ‘‘real porous material,’’ some having real and imaginary part of the surface impedance of the order of 30 ρc. For the model materials, experimental results are confronted with theoretical predications. Comparison with the two-microphones technique [ASTM E 1050] will be presented for rigid frame materials. Problems associated with the mounting of soft materials will also be addressed.
Active control of sound radiation due to subsonic wave scattering from discontinuities on fluid-loaded plates. I: Far-field pressure
Authors: Gu Y. , Fuller C. R.
Published: October 2005

Active control of sound radiation due to subsonic wave scattering from discontinuities represented by a line constraint or by a uniform reinforcing rib positioned on a fluid-loaded infinite plate is analytically studied. The mathematical models are based on the plate vibration and sound radiation due to a line force or a line moment solved in the spectral k domain. For simplicity, the far-field pressure is estimated by the stationary phase approach. Feed-forward control is achieved by adding secondary line forces applied to the plate near the discontinuity. The amplitudes of control forces are determined by the optimal solution of a cost function that integrates the far-field radiated acoustic intensity in a semicylindrical space around the discontinuity. The results show that for subsonic incident waves, high reduction in radiated pressure due to spectral wave scattering at the discontinuities is possible with two active control forces located near the discontinuity. The amount of sound reduction as well as the residual directivity pattern is shown to depend upon the number and location of the control forces.
Theory of long wavelength acoustic radiation pressure
Authors: Löfstedt Ritva , Putterman Seth
Published: October 2005

A general formulation of the radiation force exerted on an object by a long wavelength sound field is developed in terms of an asymptotic multipole expansion. In various limits, the results of King [Proc. R. Soc. London, Ser. A 147, 212 (1934)], Gorkov [Sov. Phys. Dokl. 6, 773 (1962)], and Yosioka and Kawasima [Acustica 5, 167 (1955)] are recovered. In addition, the existence of a spectrum of monopole and dipole radiation force resonances is demonstrated which occur when the bulk modulus of the object is small compared to that of the surrounding medium. Near standing wave resonances, the bulk viscosity is shown to play an essential role in determining the force. For traveling waves, the bulk viscosity can lead to the dominant contribution to the radiation pressure even in the limit of zero frequency. For soap bubbles, the leading-order contribution to the radiation pressure is shown to be quadrupolar.
Gender recognition from speech. Part II: Fine analysis
Authors: Childers D. G. , Wu Ke
Published: October 2005

The purpose of this research was to investigate the potential effectiveness of digital speech processing and pattern recognition techniques for the automatic recognition of gender from speech. In part I Coarse Analysis [K. Wu and D. G. Childers, J. Acoust. Soc. Am. 90 (1991)] various feature vectors and distance measures were examined to determine their appropriateness for recognizing a speaker’s gender from vowels, unvoiced fricatives, and voiced fricatives. One recognition scheme based on feature vectors extracted from vowels achieved 100% correct recognition of the speaker’s gender using a database of 52 speakers (27 male and 25 female). In this paper a detailed, fine analysis of the characteristics of vowels is performed, including formant frequencies, bandwidths, and amplitudes, as well as speaker fundamental frequency of voicing. The fine analysis used a pitch synchronous closed-phase analysis technique. Detailed formant features, including frequencies, bandwidths, and amplitudes, were extracted by a closed-phase weighted recursive least-squares method that employed a variable forgetting factor, i.e., WRLS-VFF. The electroglottograph signal was used to locate the closed-phase portion of the speech signal. A two-way statistical analysis of variance (ANOVA) was performed to test the differences between gender features. The relative importance of grouped vowel features was evaluated by a pattern recognition approach. Numerous interesting results were obtained, including the fact that the second formant frequency was a slightly better recognizer of gender than fundamental frequency, giving 98.1% versus 96.2% correct recognition, respectively. The statistical tests indicated that the spectra for female speakers had a steeper slope (or tilt) than that for males. The results suggest that redundant gender information was imbedded in the fundamental frequency and vocal tract resonance characteristics. The feature vectors for female voices were observed to have higher within-group variations than those for male voices. The data in this study were also used to replicate portions of the Peterson and Barney [J. Acoust. Soc. Am. 24, 175–184 (1952)] study of vowels for male and female speakers.
Periodicity and pitch perception
Authors: Pierce John R.
Published: October 2005

There has been experimental evidence pointing to at least two pitch mechanisms, the first involving low-order harmonics that are resolved along the basilar membrane, and the second a periodicity mechanism that depends only on the repetition rate of the time waveform on the basilar membrane. If this time waveform is derived from repeated bursts of sinusoidal tone, the second mechanism might be the sole pitch mechanism. It is found that this can be so up to rates as high as 250 bursts of 4978-Hz tone per second. The stimuli used are periodic patterns of equally spaced tone bursts, with either successive tone bursts in the same phase, or every fourth tone burst 180° out of phase with respect to the rest. Up to a critical transitional rate of tone bursts a second, the two sequences sound exactly the same, despite their different fundamental frequencies and frequency separation of harmonics. Critical rate data are given for sinusoidal bursts of seven different frequencies. Critical rates appear to be closely related to the critical bandwidth. Pitch matching appears to be consistent with these observations; it is on rate below the critical rate and can be on fundamental frequency above the critical rate.
Counterintuitive reversals in lateralization using rectangularly modulated noise
Authors: Hafter Ervin R. , Shelton Brian R.
Published: October 2005

Listeners were required to detect an interaural delay of 37.5 μs in the modulation envelope of a pulse-modulated noise. The noise carrier had a bandwidth of 1000 Hz and a center frequency (fc) that varied from 550–9600 Hz. The modulation frequency was either 250, 500, or 1000 Hz and the pulse widths were either 100, 200, or 400 μs. For certain combinations of fc and pulse widths, unexpected results occurred when the side of the perceived image did not agree with the side stimulated first. Lateralizations of these stimuli were found to oscillate from the leading side to the lagging depending on the number of cycles of the carrier falling within a single pulse, seemingly indicating the importance of the stimulus’ fine structure. Furthermore, conditions that either limited the bandwidth of the stimuli or masked portions of its spectrum show that the oscillations depended on information in the low-frequency regions. A cross-correlation model that emphasizes both the positive and negative peaks in the cross-correlations functions is shown to describe the basic phenomena.
Lateralization of rectangularly modulated noise: Explanations for counterintuitive reversals
Authors: Stern Richard M. , Zeppenfeld Torsten , Shear Glenn D.
Published: October 2005

A number of years ago Hafter and Shelton [J. Acoust. Soc. Am. Suppl. 1 68, S16 (1980), Hafter and Shelton, J. Acoust. Soc. Am. XX, ▪▪–▪▪ (1991)] demonstrated that diotic bandpass noise that is multiplied by a dichotic pair of periodic rectangular gating functions could be strongly perceived toward the ear receiving the signal with the gating function that is lagging in time. These results were surprising because sounds presented with interaural time delays (ITDs) are normally perceived toward the ear receiving the signal that is leading in time. In order to better understand these counterintuitive phenomena an analytical expression for the cross-correlation function of these gated-noise stimuli is derived, and it is shown that many of the general properties of the data can be accounted for by considering only the properties of this function. The lateralization of the gated-noise stimuli is compared to predictions of three types of models of binaural signal processing: models based on the cross-correlation function of the entire signal, models based on the interaural group delay or phase delay at low frequencies, and the position-variable model, which is based on the response of the peripheral auditory system to the stimuli. It is shown that the observed lateralization results, including the unexpected reversals and various frequency effects, can be explained without further assumption by an extended implementation of the position-variable model [Stern and Colburn, J. Acoust. Soc. Am. 64, 127–140 (1978)]. The cross-correlation functions of the original stimuli can also be related to the lateralization data, but in a much less natural fashion. It is argued that models based on the interaural group delay of the original stimuli will not describe the observed results, although low-frequency phase delay is qualitatively consistent with the observed lateralization phenomena.
Probability distributions of interaural phase and level differences in binaural detection stimuli
Authors: Zurek P. M.
Published: October 2005

Probability distributions of interaural phase and level differences are derived for the stimuli used in many studies of binaural detection and interaural-correlation discrimination. Example distributions are shown and summary plots give the standard deviations of these distributions as functions of signal-to-noise ratio.
Evaluation of a principal-components tactile aid for the hearing-impaired
Authors: Weisenberger Janet M. , Craig James C. , Abbott Grayson D.
Published: October 2005

Principal component analysis, a statistical data reduction technique which can be used to eliminate redundant information, has shown promising results as a speech coding strategy in auditory perceptual studies. The present study describes the development, modification, and evaluation of a principal components-based tactile aid for speech perception by the hearing-impaired. In this device, the first two principal components of an input speech signal were displayed on two-dimensional arrays of vibrators contacting either the fingertip or the forearm. Initial testing of the device with closed-set recorded speech tokens showed fair recognition performance, reaching 57% for three consonants and 56% for four vowels. Modifications to the processor algorithm designed to improve vowel recognizability resulted in higher levels of performance (66% for eight vowels). A real-time prototype was constructed implementing the revised algorithm. Live-voice testing was conducted with six normal-hearing subjects, three of whom had previous training with the Queen’s University vocoder, a multichannel tactile vocoder that has shown promising results. Performance of these ‘‘trained’’ subjects for both single-item and connected speech tasks was excellent, equalling levels obtained with the Queen’s vocoder. These results suggest that a principal components design may be a promising alternative to a vocoder strategy for a tactile aid. Results for the ‘‘naive’’ subjects did not reach the levels attained by the trained subjects, a finding partially attributed to the short training period available to the naive subjects. The higher level of performance for the trained subjects, together with the similarity of performance for the principal components aid and the Queen’s vocoder for these subjects, suggests that they were able to transfer previous learning with the Queen’s vocoder to the principal components device.
Central, auditory mechanisms of perceptual compensation for spectral-envelope distortiona)
Authors: Watkins Anthony J.
Published: October 2005

The spectral envelope is a major determinant of the perceptual identity of many classes of sound including speech. When sounds are transmitted from the source to the listener, the spectral envelope is invariably and diversely distorted, by factors such as room reverberation. Perceptual compensation for spectral-envelope distortion was investigated here. Carrier sounds were distorted by spectral envelope difference filters whose frequency response is the spectral envelope of one vowel minus the spectral envelope of another. The filter /i/ minus /q/ and its inverse were used. Subjects identified a test sound that followed the carrier. The test sound was drawn from an an /itch/ to /qtch/ continuum. Perceptual compensation produces a phoneme boundary difference between /i/ minus /q/ and its inverse. Carriers were the phrase ‘‘the next word is’’ spoken by the same (male) speaker as the test sounds, signal-correlated noise derived from this phrase, the same phrase spoken by a female speaker, male and female versions played backwards, and a repeated end-point vowel. The carrier and test were presented to the same ear, to different ears, and from different apparent directions (by varying interaural time delay). The results show that compensation is unlike peripheral phenomena, such as adaptation, and unlike phonetic perceptual phenomena. The evidence favors a central, auditory mechanism.
Effects of the pattern of spectral spacing on the perceptual fusion of harmonics
Authors: Roberts Brian , Bregman Albert S.
Published: October 2005

Harmonic relations are important in the perceptual fusion of frequency components, but other factors can influence how much any given harmonic is integrated into a complex tone. This study considers whether the pattern of spectral spacing can act as such a factor. A complex tone consisting only of odd-numbered harmonics has a regular harmonic spacing of twice the fundamental frequency. The addition of a single even-numbered harmonic will locally disrupt this regular pattern. If harmonic relations alone limit the perceptual integration of the added harmonic, it should be as well integrated into the complex as its odd-numbered neighbors. Subjects were required to ‘‘hear out’’ one of the components of the complex and either to rate its perceived clarity (experiment 1) or to judge its pitch in relation to a pure tone 6% higher or lower in frequency (experiment 2). For a fundamental of 100 or 200 Hz, but not 400 Hz, the even harmonic generally could be heard out more easily than its odd neighbors. It is proposed that the poorer integration of the even harmonic at low fundamentals may result from a cross-channel comparison of amplitude-modulation rates at the output of the auditory filterbank.
Gap detection in multiple narrow bands of noise as a function of spectral configuration
Authors: Grose John H.
Published: October 2005

This study sought to differentiate between the effect of stimulus bandwidth and the effect of number of activated auditory channels on gap detection in narrow bands of noise. The aim was to clarify the role of across-frequency analysis in temporal processing. Experiment 1 established that when total noise bandwidth is held constant at 100 Hz, gap detection improves as stimulus energy is distributed to both lower and higher frequencies. Experiment 2a showed that the effect was smaller, or was absent, when the cumulative stimulus bandwidth was increased from 100 to 200 Hz. Experiment 2b confirmed that the benefit of spectral dispersion for the narrower cumulative bandwidth also held for a higher frequency region. The results suggest that in conditions where the cumulative stimulus bandwidth is relatively narrow and, concomitantly, gap detection is relatively poor, there is an advantage in dispersing the stimulus across a number of auditory channels. The advantage for the distribution of energy across a range of auditory channels may be offset when the spectral spacing of bands exceeds a critical value.
Form function dependence on rigidity and mass
Authors: Gaumond Charles F. , Dragonette Louis R.
Published: October 2005

The backscattered form function of an infinite cylinder becomes very small at a certain value of thickness for values of the dimensionless frequency ka<1. This phenomena is examined by deriving the equations of motion in terms of the overall mass and compressibility of the cylinder within a thin shell approximation. The value of the form function is determined for the most part by the first two terms in the normal mode expansion. These two terms are of comparable magnitude. Additionally, each of these two terms is shown to depend primarily on either the mass or compressibility of the cylinder. Cancellation of these two terms occurs at the value of thickness for which the backscattered form function is very small.
The acoustic scattering by a submerged, spherical shell. III: Pole trajectories in the complex-k
a plane
Authors: Hackman Roger H. , Sammelmann Gary S.
Published: October 2005

Previously, a fundamentally oriented analysis was presented of the complex-ka plane pole structure of the S matrix for a thin spherical shell for 0<ka<100 [Sammelmann et al., J. Acoust. Soc. Am. 85, 114–124 (1989)]. In this analysis, it was concluded that fluid loading the first antisymmetric mode of the shell in vacuum had a rather violent effect; the mode bifurcated into two distinct modes near the coincidence frequency. In this article, the relationship of the poles of the diffractive modes of impenetrable spheres and the eigenfrequencies of the shell in vacuum to the modes of the fluid-loaded shell are precisely established by studying the complex-ka plane trajectories of the S-matrix poles under variations of the material parameters of the shell. The evolution of these modes are also examined as the shell thickness is varied from 2% to 50% of the outer radius of the shell. It is found that the limit of an elastic solid is not approached smoothly and that modal reorganizations similar to the bifurcation phenomenon noted above is a common occurrence. The implications of this behavior are examined for both the complex-ka, real-l and the real-ka, complex-l pictures.
The thin-shape breakdown (TSB) of the Helmholtz integral equation
Authors: Martinez R.
Published: October 2005

Many numerical implementations of the Helmholtz integral equation exist today that can predict routinely the field scattered by a volume-holding body. One such object is the ellipsoidal ‘‘core’’ of a typical airborne or submerged vehicle stripped of its thin appendages, i.e., stripped of its finlike control surfaces, etc. The reason for these omissions has often been an inherent limitation of the cited modeling tools rather than a rational dismissal of the potential effect of these neglected appendages on the complete body’s expected scattering cross section. The limitation of existing techniques is this: The standard form of Gauss’ theorem on which they are based, that leads to the Helmholtz integral, becomes meaningless when the thickness of the shape addressed tapers down to zero even over only part of the structure. This paper exposes analytically the fundamental cause of this thin-shape breakdown (TSB), and in the process derives an alternate boundary element formulation for its cure.