bluuebunny/crossref_metadata_2025 huggingface dataset:
Turbulent wall pressure at low wavenumbers: Relation to nonlinear sources in planar and cylindrical flow
Authors: Chase David M. , Noiseux Claude F.
Published: October 2005

As a step toward improved modeling of flow noise in underwater acoustic applications, integral expressions are derived that formally relate the wall-pressure amplitude at fixed wavenumber and frequency to purely nonlinear fluctuating Reynolds-stress components. Results are obtained for incompressible and slightly compressible planar and parallel cylindrical flows, the mean flow being approximated as wall parallel. The expressions are developed as expansions in a parameter U∞kx /ω (and also U∞/c in the compressive case) to yield simple relations for the wall-pressure amplitude at low (nonconvective) wavenumbers. The results of Bergeron for the planar case providing this amplitude explicitly as an integral over nonlinear sources are thereby verified, clarified, and extended to a domain where the wavenumber K need not be small relative to the reciprocal thickness of the source layer. By similar expansions applied to the axisymmetric component in the cylindrical case, this wall-pressure amplitude too is expressed as an integral over nonlinear sources. For nonvanishing source amplitudes the wall-pressure amplitude at zero streamwise wavenumber in this case does not vanish with or without compressibility. With inclusion of slight compressibility, in this instance where the wall is infinitely extended in one dimension only, in place of the nonintegrable singularity at the sound wavenumber in the idealized two-dimensional planar case, an integrable, logarithmic singularity is found. Further progress requires modeling the source spectra.
Propagation of elastic surface waves along a cylindrical cavity and their excitation by a point force
Authors: Boström Anders , Burden Anthony
Published: October 2005

The existence of surface wave modes, propagating along an infinite cylindrical cavity in an elastic medium, is established for every integer m, where m is the azimuthal mode number. These waves are analogous to the Rayleigh wave on a half-space, being confined to the immediate vicinity of the cavity. The modes exhibit dispersion and have a cutoff frequency which increases with m, except for the flexural (m = 1) mode which exists at all frequencies. At cutoff the phase velocity is equal to that of the shear waves and decreases, with increasing frequency, to that of the Rayleigh wave. We present results for the group velocities and displacement and stress fields of the modes and also exhibit the effect of various point forces acting near the cavity. In the vicinity of the cavity, not too near the point force, the surface wave contribution dominates the total displacement field.
Impulse studies of double diffraction: A discrete Huygens interpretation
Authors: Medwin Herman , Childs Emily , Jebsen Gary M.
Published: October 2005

A closed-form analytical impulse solution of diffraction by a rigid wedge is interpreted from the point of view of discrete Huygens wavelets emanating from the crest of the wedge. The strengths of these secondary sources and the impulse field diffracted over a second wedge are calculated. Digital Fourier transformation is then used to determine the spectral loss during double diffraction. The technique is applied to a thick plate, an angled wide barrier, and a strip; successful predictions of laboratory experiments are achieved. In principle, the method may be used for any number of diffractions by straight line segments of an extended barrier or scattering surface.
The sounds of honey bees and social wasps are always composed of a uniform frequency
Authors: Ishay Jacob S. , Sadeh Dror
Published: October 2005

The sounds produced by the honeybee Apis mellifera (Apidae) and by the social wasps Paravespula germanica and Vespa orientalis (Hymenoptera, Vespinae) are of a uniform frequency which nevertheless differs in accordance with its purpose. In honey bees, the sound produced by ventilating workers has a frequency of 309 Hz, whereas that produced by the queen (queen piping) has a frequency of 450 Hz. In P. germanica, the sound frequency during ventilation is 194–231 Hz, whereas in V. orientalis, the ventilation and the awakening dance sounds (produced by the workers) and the hunger signal (sounded by the larvae) have a frequency of 118–140 Hz, while the threatening flight occurs at 221 Hz and the dance of workers facing the queen—at 600–637 Hz. All the produced sounds are synchronized to a uniform frequency over a given period, regardless of whether they are produced by a single insect or by an entire group. However, the frequency may change with time, probably owing to fatigue of the producer, and also the intensity of the sound may change, which results in a great variability of the sounds despite their uniform frequency.
Estimation of acoustical energy reflectance at the eardrum from measurements of pressure distribution in the human ear canal
Authors: Stinson M. R. , Shaw E. A. G. , Lawton B. W.
Published: October 2005

At frequencies greater than 2 kHz the acoustic impedance at the human eardrum is an unreliable indicator of the behavior of the middle ear system because of the complicated configuration of the ear canal and tympanic membrane. The energy reflectance at the eardrum, however, when obtained from measurement of the standing wave ratio (SWR) in the canal, is relatively insensitive to irregularities in the anatomical layout at the higher frequencies. Measurements of sound pressure distribution in 13 normal ear canals have been analyzed in a critical manner to provide new values of SWR, with estimates of error, between 5 and 10 kHz. At the higher frequencies these values tend to be appreciably greater than those previously reported. At 8 kHz, for example, the new values of SWR range between 18 and 24 dB as compared with earlier values which are in the vicinity of 13 dB. The correspondingly greater values of energy reflectance (60%–78%, as compared with 40%) are more consistent with known properties (mass, size, vibrational patterns) of the human eardrum. These results are applicable to the development of network models representing the middle ear system.
Statistical properties of responses to dichotic listening with CV nonsense syllables
Authors: Speaks Charles , Niccum Nancy , Carney Edward
Published: October 2005

Twenty-four listeners received 20 dichotic listening runs of 30 pairs of natural CV nonsense syllables per run. Left- and right-ear responses are represented by two partially overlapping normal distributions with equal variance. Observed ear advantages across listening runs are also distributed normally. The means of the distributions of ear advantage are listener specific, but the standard deviations are 10.8%±2.5. The origin of reversals in direction of ear advantage among listening runs is statistical—a small mean/sigma ratio—and approximately six listening runs (180 listening trials) are required to achieve a split-half reliability coefficient of +0.90.
Community annoyance from aircraft and ground vehicle noise
Authors: Kryter Karl D.
Published: October 2005

Data from published noise-annoyance surveys are related to a common measure of noise exposure Ldn. The results provide means for predicting the annoyance (experienced by percentages of people of normal and of supersensitivity) attributable to noise from aircraft and from street and road traffic. Correlations of 0.90 to 0.95 are found between Ldn and percentages of people annoyed by aircraft noise when low, moderate, and higher levels of annoyance are measured for both a broad range (35 dB) and a restricted range (20 dB) of Ldn. Noise from urban street and road traffic is shown to cause less annoyance than the noise from aircrafts when both have the same Ldn as typically measured or estimated for outdoors. The difference, equivalent to a difference of about 10 dB in Ldn, is attributed to acoustical factors that diminish in-and-around-the-home noise dosages from ground vehicular traffic compared to dosages from aircraft operations. Generalized functions showing degrees of annoyance and percentages of U.S. urban population exposed to effective levels of Ldn for aircraft noise and for street and road traffic noise are presented. It is shown that an earlier analysis by Schultz [’’Synthesis of social surveys on noise annoyance,’’ J. Acoust. Soc. Am. 64, 377–405 (1978)] significantly underestimates the annoyance associated with aircraft noise and significantly overestimates the percentages of the U.S. population to be exposed to effective levels of noise from vehicles of transportation.
The field of a focusing source
Authors: Lucas Bernard G. , Muir Thomas G.
Published: October 2005

An analytical description for the field of a focusing source is derived. It is valid for spherically concave sources with small aperture angle and large ka (radius a, wavenumber k.) The solution furnishes easy access to the sound distribution along the axis and in the focal plane, as well as to parameters such as focusing gain, width of the focal spot, and phase shifting in the focal region. Experiments conducted with an f/2 lens coupled to a planar array are discussed. The results support the utility of the analytical model for describing the distribution of sound along the acoustic axis and across the focal plane.
Generalized equations for rectified diffusion
Authors: Crum Lawrence A. , Hansen Gary M.
Published: October 2005

There are at least four different equations present in the literature for the threshold for growth of gas bubbles by rectified diffusion. These various equations have limited regions of applicability and also give significantly different predictions in common regions of applicability. In this paper, a set of general equations are obtained for the growth rate and the threshold for rectified diffusion that apply over a wider range of interest. It is shown that under certain restrictions the previous equations agree with the more general ones given here. Finally, graphical representations of the equations are given showing the degree of approximation and the range of applicability of the specialized equations.
Finite bandwidth corrections applicable to noise spectra shaped by atmospheric attenuation
Authors: Howell G. P. , Morfey C. L.
Published: October 2005

Use of 1/3-octave filters for noise analysis can give a misleading estimate of the actual spectrum, if the latter is steeply sloping. The present paper offers a simple procedure for estimating the true sloping spectrum in such cases. The results enable 1/3-octave data from a broadband source—such as aircraft jet noise—to be more accurately extrapolated to different distances and atmospheric conditions.
Resonant porous material absorbers
Authors: Moore James A. , Lyon Richard H.
Published: October 2005

A theory for the propagation of sound in a resistive porous material is formulated in terms of the bulk elastic properties of the structure of the porous material and the permeating fluid. Impedance relations are developed to describe the acoustic behavior of porous material layers of finite thickness. The acoustic behavior of resistive screens and impervious septa is also characterized. An analytical procedure is outlined for evaluating the sound absorption characteristics of different coating configurations consisting of arrangements of porous material layers, impervious septa, and resistive screens. A novel design configuration is described that achieves optimal sound absorption levels at low frequency in air. The coating is lightweight and also thin in comparison with an equivalent layer of uniform absorbing material. The dynamic behavior of the design is explained in physical terms.
Auditory thresholds of a captive Eastern Pacific bottle-nosed dolphin, T
u
r
s
i
o
p
s spp
Authors: Ljungblad Donald K. , Scoggins Penelope D. , Gilmartin William G.
Published: October 2005

The hearing threshold of a bottle-nosed dolphin from the Eastern Pacific was tested using behavioral response techniques. The animal responded to signals ranging from 2 to 135 kHz, but did not respond to higher frequency signals (136–160 kHz) despite repeated trials. The range of greatest sensitivity was between 25 and 70 kHz with peak sensitivities at 25 and 50 kHz. This measured hearing threshold is compared to frequency responses and sensitivities previously reported for other cetaceans.
The effect of range dependence on acoustic propagation in a convergence zone environment
Authors: Henrick R. F. , Burkom H. S.
Published: October 2005

The effect of a range-dependent environment, typified by fronts or eddies, or convergence zone intensities is investigated. An analytical approach is taken to examine vertical redistribution of acoustic energy resulting from explicit changes in sound channel structure and from implicit effects of horizontal sound-speed gradients. Under certain oceanographic conditions, such a redistribution is shown to lead to catastrophic signal losses at all ranges for receivers at fixed depths. A generalized Snell’s law in a range-dependent environment is derived and then utilized to identify regions where such losses may occur. It is shown that large changes in transmission result only when horizontal sound-speed changes evaluated over a ray path are not small compared with the amount of sound-speed depth excess. Several examples are presented illustrating the theory using parabolic equation numerical simulations. A method is also presented to predict expected signal losses as a function of source position in an eddy or front.
The modulated ultrasonic whistle as an acoustic source for modeling
Authors: Hutchins D. A. , Jones H. W. , Vermeulen P. J.
Published: October 2005

A compound modulated whistle source has been developed which produces broadband sound of high intensity in air over the 16 to 160-kHz frequency range. The development and characteristics of a prototype whistle source are described, and the details given of the final whistle design. A compound source of three such whistles is shown to have an adjustable frequency spectrum, of particular application to modeling experiments.
Tonal masking and frequency selectivity for the monaural and binaural hearing systems
Authors: Yama Mark F. , Small A. M.
Published: October 2005

A series of masking experiments was performed with the aim of comparing frequency selectivity for the monaural and binaural systems. The masking stimulus used in this study combined a sinusoid, which was gated simultaneously with the signal, with a continuous broadband noise. Signal frequency was fixed at 500 Hz. In one condition, the tonal masker and noise were interaurally in phase and the signal was phase reversed. In a second condition, noise, tonal masker, and signal were presented to one ear alone. Signal thresholds were obtained as a function of masker frequency for these two conditions. After making an appropriate selection of noise levels, masking functions for the monaural and binaural system conditions were found to agree closely except for a region about their tips where the binaural condition was more detectable. Two possible interpretations of these results are discussed. Either the monaural and binaural systems contain filters each which have similarly shaped skirts, or the frequency selectivity observed under both diotic and dichotic conditions (for large frequency separations of masker and signal) reflect the operation of a common peripheral filter.
Detection of interaural differences of time in trains of high-frequency clicks as a function of interclick interval and number
Authors: Hafter E. R. , Dye R. H.
Published: October 2005

Listeners were asked to detect interaural differences of time in trains of 4000-Hz clicks as the interclick interval (ICI) was varied from 10 to 1 ms and the number of clicks in a train (n) was varied from 1 to 32. Plots of log interaural threshold versus log n produce straight lines whose absolute slopes decrease toward 0.0 with decreasing ICI. These results are shown to fit a saturation model which argues that as the click rate increases, the evoked neural activity moves from a response that is tonic toward one which is more phasic. The need to postulate neural compression is based in part on the fact that the three most commonly cited models of the limitations imposed by high frequency—reduction in the depth of modulations due to narrow-band filtering within the auditory system, neural refractoriness, and nonindependence of successive samples of internal noise—do not predict a change in slope with rate.
The role of the seabottom attenuation profile in shallow water acoustic propagation
Authors: Mitchell Stephen K. , Focke Karl C.
Published: October 2005

The effect of the seabottom upon acoustic propagation in the frequency range from 20 to 2000 Hz in shallow water is analyzed. In particular, the role of depth and frequency variations of attenuation is considered. The point of view that attenuation in the seabottom varies linearly with frequency and changes with depth is taken. Normal mode calculations which demonstrate the interplay between depth variations of attenuation and the frequency dependence of propagation loss and mode attenuation coefficients are presented. It is shown that, if in the course of data analysis, attenuation were erroneously constrained to be constant with depth, then a nonlinear estimate for frequency dependence of attenuation could result. Calculations based upon attenuation profiles from the geophysical literature are compared with reported propagation loss data from the acoustics literature.
Relative hazard of weapons impulses
Authors: Price G. Richard
Published: October 2005

Arguments in favor of a theoretically based damage-risk criterion (DRC) for intense noise [G. R. Price, J. Acoust. Soc. Am. 69, 171–177 (1981); 66, 456–465 (1979); J. Acoust. Soc. Am. Suppl. 1 62, S95 (1977)] are further developed here to make a crucial prediction. Based on measured spectral differences, it was predicted that rifle impulses would cause permanent threshold shifts at approximately 9 dB lower peak pressures than cannon impulses. In contrast, DRCs in use in the world predict that the cannon would be more hazardous than the rifle by 7 to 10 dB. Electrophysiological measures of sensitivity were used in 38 cats (76 ears) which were exposed to 60 impulses, approximately 3 s apart, at various peak pressures, from either a rifle or a 105-mm Howitzer. Hearing changes were followed until recovery was complete (2 months). Permanent threshold shifts began at about 140 dB for rifle impulses and 150–155 dB for cannon impulses, confirming the prediction and supporting the contention that there is a spectrally dependent critical level for the ear at high intensities. Implications for present DRCs and future risk assessment schemes are discussed.
Cochlear microphonic responses to acoustic clicks in guinea pig and their relation with microphonic responses to pure tones
Authors: Echeverría Eugenio L. , Robles Luis W.
Published: October 2005

Cochlear microphonic (CM) responses to acoustic transient stimuli were studied at the three more basal turns of the cochlea in the guinea pig. The responses to rarefaction and condensation pressure pulses of less than 100-μs duration were recorded using the differential electrode technique. In some animals the CM response to pure tones was recorded at the same position at which the transient response was obtained. The transient responses recorded at the three turns of the cochlea displayed a damped oscillation at a frequency consistent with the values of cutoff frequency already known for the electrode positions. Some of the responses were significantly less damped than click responses previously reported. There was a good correlation between the cutoff frequency in the frequency response curve and the frequency of oscillation in the transient response for recordings obtained at the same position in the cochlea. A nonlinear effect was observed for changes in stimulus intensity. There was a less than proportional decrease in amplitude of the initial part of the damped oscillation for a decrease of the stimulus intensity, while the late part of the response behaved almost linearly. This nonlinearity observed in the CM transient response could not be explained by a nonlinear characteristic of the sort reported in the basilar membrane of the squirrel monkey by Robles et al. [J. Acoust. Soc. Am. 59, 926–939 (1976)]; rather it seems to be a saturation nonlinearity similar to the one known for sinusoidal stimulation.
Tuning curves and pitch matches in a listener with a unilateral, low-frequency hearing loss
Authors: Florentine Mary , Houtsma Adrianus J. M.
Published: October 2005

Psychoacoustical tuning curves and interaural pitch matches were measured in a listener with a unilateral, moderately severe hearing loss of primarily cochlear origin below 2 kHz. The psychoacoustical tuning curves, measured in a simultaneous-masking paradigm, were obtained at 1 kHz for probe levels of 4.5-, 7-, and 13-dB SL in the impaired ear, and 7-dB SL in the normal ear. Results show that as the level of the probe increased from 4.5- to 13-dB SL in the impaired ear, (1) the frequency location of the tip of the tuning curve decreased from approximately 2.85 to 2.20 kHz and (2) the lowest level of the masker required to just mask the probe increased from 49- to 83-dB SPL. The tuning curve in the normal ear was comparable to data from other normal listeners. The interaural pitch matches were measured from 0.5 to 6 kHz at 10-dB SL in the impaired ear and approximately 15- to 20-dB SL in the normal ear. Results show reasonable identity matches (e.g., a 500-Hz tone in the impaired ear was matched close to a 500-Hz tone in the normal ear), although variability was significantly greater for pitch matches below 2 kHz. The results are discussed in terms of their implications for models of pitch perception.
Distortion of finite amplitude ultrasound in lossy media
Authors: Haran Michael E. , Cook Bill D.
Published: October 2005

A form of Burgers’ equation is used to derive an algorithm for calculating harmonic generation by a continuous plane wave of ultrasound propagating in a nonlinear, lossy, nondispersive medium. The algorithm accounts for attenuation that is not quadratically related to the frequency of the wave. Attenuation strongly affects the rate of harmonic production. The effect of variations of the relationship between attenuation and frequency is shown. Biological tissue is an example of a highly lossy medium where the attenuation does not increase with the square of the frequency. Calculations for several types of tissue and biological fluids are presented that show, for certain conditions, finite amplitude distortion is possible.
On the calculation of normal mode group velocity and attenuation
Authors: Koch Robert A. , Penland Cecile , Vidmar Paul J. , Hawker Kenneth E.
Published: October 2005

The group velocity for a normal mode can be calculated without invoking a finite difference approximation requiring a second eigenmode calculation. The reciprocity relation is employed in a derivation of the normal mode group velocity and attenuation coefficient. The group velocity thus calculated is more accurate than a comparable finite difference approximation. Arbitrarily arranged layers of solid and fluid media are considered.
Response of K. D. Kryter to modified comments by T. J. Schultz on K. D. Kryter’s paper, ‘‘Community annoyance from aircraft and ground vehicle noise’’[J. Acoust. Soc. Am. 7
2, 1243–1252 (1982)]
Authors: Kryter Karl D.
Published: October 2005

This letter is in response to comments made by T. J. Schultz [J. Acoust. Soc. Am. 72, 1243–1252 (1982)] with respect to a paper by K. D. Kryter [J. Acoust. Soc. Am. 72, 1222–1242 (1982)].
Acoustic and perceptual indicators of emotional stress
Authors: Streeter L. A. , Macdonald N. H. , Apple W. , Krauss R. M. , Galotti K. M.
Published: October 2005

Tape recordings of telephone conversations of Consolidated Edison’s system operator (SO) and his immediate superior (CSO), beginning an hour before the 1977 New York blackout, were analyzed for indications of psychological stress. (SO was responsible for monitoring and switching power loads within the Con Ed network.) Utterances from the two individuals were analyzed to yield several pitch and amplitude statistics. To assess the perceptual correlates of stress, four groups of listeners used a seven-point scale to rate the stress of SO and CSO from either randomized vocal utterances or transcripts of the randomized utterances. Results indicated that whereas CSO’s vocal pitch increased significantly with increased situational stress, SO’s pitch decreased. Listener ratings of stress from the voice were positively related to average pitch. It appears that listeners’ stereotype of psychological stress includes elevated pitch and amplitude levels, as well as their increased variability.
Theoretical framework for spectrum analysis in ultrasonic tissue characterization
Authors: Lizzi Frederic L. , Greenebaum Michael , Feleppa Ernest J. , Elbaum Marek , Coleman D. Jackson
Published: October 2005

An analytic model is described for application in ultrasonic tissue characterization. The model is applicable to clinical broadband pulse echo systems. It treats spectra derived from received echo signals and relates them to physical tissue properties. The model can be applied to deterministic tissue structures (e.g., retinal detachments, larger blood vessels, and surface layers of the kidney) and to stochastic tissue structures (e.g., various tumors). The beam patterns included in the model are those generated by focused transducers typically used in high-resolution clinical ultrasound. Appropriate calibration procedures are also treated; these are needed for interpretation of absolute spectral parameters. The results obtained with the analytic model have been used to design a digital processing system and the associated techniques which are now being applied during examinations of the eye and abdominal organs. The results have proven useful in interpreting data from various types of tissues. To illustrate the application of these results, representative clinical data, obtained from the digital system, are presented for two types of tissue architectures. The first case is a detached retina representing a deterministic structure characterized by well-defined thickness and reflection coefficients. The second case is asteroid hyalosis and represents a stochastic entity in which the positions of small scattering particles are best described in statistical terms, and characterization is accomplished by means of normalized power spectra.
Intensity variance of spherical waves in anisotropic media
Authors: Schulkin Morris
Published: October 2005

The solution to the problem of determining the intensity variance in the forward direction for spherical waves propagating in an anisotropic medium of Gaussian correlation oblate spheroids has not yet been reduced to elementary functions. However, the solution is known for asymptotic limits at zero range and at very long range where the anisotropic terms are separable in both cases. The author shows that anisotropic terms are also separable for the intensity variance of plane waves at the point where the variance depends on the square of the range. A new anisotropic component is found in this way. He also computes the ratio of the intensity variance for plane waves to that of spherical waves at all ranges in a random medium of Gaussian correlation spheres. Applying this ratio to the plane-wave anisotropic solution yields useful estimates for the variance of spherical waves in Gaussian anisotropic media in the region where the variance depends on the square of the range for both small and large anisotropy.
Automated digital benchtop calibration system for hydrophone arrays
Authors: Luker L. Dwight , Zalesak Joseph F. , Brown Craig K. , Scott Richard E.
Published: October 2005

A calibration system is described which can measure the complex sensitivity and directivity patterns of hydrophone arrays, such as sonobuoy arrays, in which the hydrophone elements are individually accessible. These arrays are often deployed over a great distance in the ocean. Calibrating them under free-field conditions would be an extremely difficult task. The system described here allows for their calibration on a benchtop. The entire calibration system is controlled by a computer and requires minimal operator intervention. The computer algorithm is also applicable to hydrophone arrays which do not have individually accessible elements. Results are presented which compare measured directivity patterns with theoretical directivity patterns calculated from the measured complex sensitivities of the individual array elements.
Growth of forward masking for sinusoidal and noise maskers as a function of signal delay; implications for suppression in noise
Authors: Moore Brian C. J. , Glasberg Brian R.
Published: October 2005

The first two experiments were designed to determine whether mutual suppression in broadband noise increases in strength with increasing overall level. In experiment I masking functions (signal threshold versus masker level) were measured in forward masking as a function of the delay time of a 10-ms signal, both for a broadband noise masker (low-pass filtered at 8 kHz) and for sinusoidal maskers at 1, 2, and 4 kHz. In the latter case the signal frequency equaled the masker frequency. For short signal delays the masking functions were steeper for the sinusoidal masker than for the noise masker. At longer delays the slopes for both masker types decreased and the slopes for the two masker types became more nearly equal. In experiment II we investigated the effect of gating a low-level noise cue with the sinusoidal masker. At the longer signal delays the masking functions had equal slopes for the broadband noise masker and the sinusoidal masker with cue. At short signal delays the masking functions for sinusoidal maskers may be ‘‘artificially’’ steepened, since the subject lacks an effective cue to distinguish the signal from the masker. The equal slopes at longer delays indicate that mutual suppression of the components within a broadband noise does not increase in strength with increasing overall level. In experiment III we attempted to estimate the magnitude of mutual suppression in a broadband noise by comparing masking functions for a broadband noise and for a noise whose bandwidth was 20% of the center frequency. The suppression was estimated to be about 2 dB at 4 kHz and 8 dB at 2 kHz. A simple mathematical expression, suggested by Jesteadt et al. [J. Acoust. Soc. Am. 71, 950–962 (1982)], was found to give an accurate description of the amount of masking produced by the broadband masker as a function of masker level and signal delay.
An examination of the composite-roughness scattering model
Authors: McDaniel Suzanne T. , Gorman Arthur D.
Published: October 2005

A perturbation technique is applied to derive a composite-roughness theory for acoustic scattering from the sea surface. The leading term in the expansion obtained is the well-known result obtainable using ad hoc arguments. Higher order terms are evaluated to assess their contribution to the high-frequency monostatic backscattering strength of the sea. It is concluded that the leading term in the perturbation expansion provides an excellent approximation.
The origin of tonality and a possible explanation of the octave enlargement phenomenon
Authors: Ohgushi Kengo
Published: October 2005

It is known that the subjective octave is slightly larger than the physical octave (=2) for a variety of tones. This paper presents a new idea about the physiological origin of tonality, and a new theory founded on recent knowledge of the auditory physiology, to explain the octave enlargement phenomenon for pure tones. The theory’s predictions of the subjective octave agree well with psychophysical data.
Flue organ pipes: Adjustments affecting steady waveform
Authors: Nolle A. W.
Published: October 2005

Adjustable flue organ pipes are used in studying the phase and amplitudes of harmonics relative to the fundamental for various horizontal positions of the upper lip, and the behavior of the spectrum as the mean jet velocity is changed in the range 5 to 39 m/s. An analog–digital electrical oscillator with two resonant circuits and a switchlike feedback characteristic resembling that suggested by Fletcher for flue pipes is also studied; biasing in the feedback circuit is analogous to displacing the pipe lip relative to the jet. Phase of a pipe harmonic relative to the fundamental changes approximately 180° at the amplitude minimum of the harmonic, as the lip is displaced horizontally, and slowly elsewhere. The electrical analog gives similar results. For each pipe model there is a ‘‘saturation’’ value of supply pressure (jet velocity) above which the fundamental amplitude is nearly constant. Evidence of phase locking of free-edge signals to the pipe oscillation is found. With a broad beveled lip, pipe oscillation can occur without the jet entering the pipe.
The audio spotlight: An application of nonlinear interaction of sound waves to a new type of loudspeaker design
Authors: Yoneyama Masahide , Fujimoto Jun-ichiroh , Kawamo Yu , Sasabe Shoichi
Published: October 2005

This work was done to devise a new type of loudspeaker. The theory for sound reproduction of this loudspeaker is based on nonlinear acoustics of sound wave interaction in air. A finite amplitude ultrasound wave that can be amplitude modulated by any audio signal is radiated from a transducer array into air as the primary wave. As a result, an audio signal is produced in the air because of the self-demodulation effect of the AM sound wave due to the nonlinearity of the air. It is possible to get a flat characteristic of reproduced sound pressure by using an equalizer. In some fundamental experiments the characteristic of the reproduced sound pressure is not quite flat due to an imperfect transducer array. Improvement of the transducer makes it possible to get a flat characteristic. A special feature of this loudspeaker is its very sharp directivity pattern, which makes it possible to realize a sound spotlight.
The role of spectral cues in discrimination of voice onset time differences
Authors: Soli Sigfrid D.
Published: October 2005

The influence of spectral cues on discrimination peaks in the region of the phonetic voicing boundary was examined. The discriminability of voice onset time (VOT) differences of the same temporal magnitude was assessed using stimuli from labial and velar consonant–vowel VOT continua that differed in the timing of spectral changes associated with the first formant (F1) transition, and in the location of the phonetic boundary. Subjects were initially given labeling tests and fixed-standard AX and all-step discrimination tests on both series. Half the subjects then received all-step discrimination training on one series and half received training on the other series. Finally, all subjects were again given the labeling and discrimination tests on both series. Just noticeable differences (jnds) in VOT were estimated from the all-step functions before and after training. Initial jnds showed that VOT discrimination was most accurate around the voicing boundary on the two continua, where differences in F1 onset frequency accompany variations in VOT. jnds on both series decreased significantly after training, although these regions of greater sensitivity remained. No evidence was seen of increased sensitivity around ±20-ms VOT, as expected if auditory processing constraints were influencing temporal order judgments. Comparisons of post-training jnds within and across series indicated that spectral components of VOT, primarily F1 onset frequency differences, exert a substantial influence on discrimination, and, along with other spectral cues provided by source differences at stimulus onset, can account for the discontinuities in discrimination often reported in research with VOT continua. Large phonetic effects also were seen in the initial performance of all subjects: jnds decreased consistently as standards drew nearer the voicing boundary. However, these effects were absent in the final jnds for most subjects. Implications of these findings for the understanding of basic auditory and attentional processes in speech perception are discussed.
Nonlinear mixing of surface acoustic waves propagating in opposite directions
Authors: Kalyanasundaram N.
Published: October 2005

The parametric mixing of two modulated surface acoustic waves propagating in opposite directions is studied with reference to nonlinear signal processing applications by the coupled mode theory of nonlinear surface waves. In the case of propagation in opposite directions the combination frequency waves generated out of the nonlinear interaction of the two primary waves and their harmonics with one another do not satisfy the phase-matching condition. Hence there exists no mode coupling between the primary waves. At the same time the amplitude of each combination frequency wave is proportional to the product of a harmonic amplitude of one of the interacting waves with a harmonic amplitude of the other wave. The variation of these harmonic amplitudes as functions of the slow scale variables are governed by two sets of coupled amplitude equations, each set pertaining to one primary wave and its harmonics. It is further shown that, in addition to surface wave modes, there also exist bulk wave modes in a certain range of values of the primary wave frequency ratio. The paper concludes with indicating the relevance of the present study to the acoustical implementation of nonlinear signal processing operations like convolution, correlation, etc.
Temporal gap detection in noise as a function of frequency, bandwidth, and level
Authors: Fitzgibbons Peter J.
Published: October 2005

Temporal gap resolution is measured with Békésy tracking procedure and filtered noise stimuli in the frequency range below 6000 Hz. Stimulus parameters include high-pass and low-pass cutoff frequency, band center frequency, bandwidth in a 2-oct range, and signal level in the low-to-moderate intensity range. The pattern of results indicates that gap resolution improves with an increase in stimulus frequency in a manner that can be described by a linear function with a slope of about 2 ms/oct. This relationship applies to signal levels greater than 25–30 dB SL. A linear trend also describes gap threshold as a function of the empirical critical bandwidth within the same frequency range. Implications of the results for simple functional models of temporal processing are examined.
Psychophysical studies evaluating the feasibility of a speech processing strategy for a multiple-channel cochlear implant
Authors: Tong Y. C. , Blamey P. J. , Dowell R. C. , Clark G. M.
Published: October 2005

This paper reports further psychophysical studies on a multiple-channel cochlear implant patient evaluating the feasibility of a speech processing strategy which converts the acoustic fundamental frequency to electric repetition rate, the second-formant frequency to electrode position, and the acoustic amplitude to current level. The first four studies evaluated the use of a special pulse pattern to minimize the loudness variation with electric repetition rate. The chosen pulse pattern consisted of multiple pulses occurring in the first half of each repetitive period (MPP) in contrast to the more conventional pattern with a single pulse per period (SPP). The results showed that MPP approximately equalized the loudness variation with repetition rate. The dynamic range of current, the pitch variation with repetition rate, and the difference limens for repetition rate were found to be similar for MPP and SPP. Two other studies investigated interaction between electrode position and repetition rate (RR). The first of these showed that the patient could make use of information provided by rising or falling RR trajectories superimposed on individual electrodes or electrode trajectories as an indicator of the direction of intonation variation. The second of these studies showed that the dissimilarities amongst the hearing sensations produced by steady-state stimuli differing in electrode position and repetition rate were characterized by two perceptual components, relating to the two electric parameters, respectively.
Generation of acoustic waves by an impulsive line source in a fluid/solid configuration with a plane boundary
Authors: de Hoop Adrianus T. , van der Hijden Jos H. M. T.
Published: October 2005

The space–time acoustic wave motion generated by a two-dimensional, impulsive, monopole line source in a fluid/solid configuration with a plane boundary is calculated with the aid of the modified Cagniard technique. The source is located in the fluid, and numerical results are presented for the reflected-wave acoustic pressure, especially in those regions of space where head wave contributions occur. There is a marked difference in time response in the different regimes that exist for the wave speed in the fluid in relation to the different wave speeds (compressional, shear, Rayleigh) in the solid. These differences are of importance to the situation where the reflected wave in the fluid is used to determine experimentally the elastic properties of the solid.
Propagation of Love waves on a cylindrical earth model
Authors: Chattopadhyay A. , Mahata N. P.
Published: October 2005

The effects of different radial inhomogeneities on the propagation of Love waves over a circular cylindrical surface have been discussed and distinctly marked on the dispersion curves. It is interesting to note that the phase velocity due to an assumed type of inhomogeneity becomes larger or smaller than that for a homogeneous layer according to whether the value of kh is more or less than 0.625. Using the above deduction and the perturbation technique, the modified dispersion equation of Love waves in a nonhomogeneous crustal layer with corrugated surface has been obtained. For different values of perturbation and inhomogeneity parameters the values of kh have been plotted against c/β0. It has been pointed out that by proper matching of the observational data with theoretical dispersion curves, the length of the corrugation as well as the inhomogeneous character may be obtained.
Effects of perilymph viscosity on low-frequency intracochlear pressures and the cochlear input impedance of the cat
Authors: Koshigoe Shozo , Kwok Wai-Kwong , Tubis Arnold
Published: October 2005

Cochlear model calculations are shown to be in reasonable agreement with recent low-frequency measurements of intracochlear pressures and the cochlear input impedance of the cat [V. Nedzelnitsky, J. Acoust. Soc. Am. 68, 1676–1689 (1980); T. J. Lynch, III, V. Nedzelnitsky, and W. T. Peake, J. Acoust. Soc. Am. 72, 108–130 (1982)]. Included in the cochlear model are perilymph viscosity, the measured variation of the area of the scala vestibuli with distance from the stapes [P. Dallos, J. Acoust. Soc. Am. 48, 489–499 (1970)], and finite impedance of the round window membrane. The WKB approximation and its extension to the low-frequency region is used in order to exhibit explicitly the dependence of the model results on the cochlear parameters.
Effects of adsorbed films on gas bubble radial oscillations
Authors: Glazman Roman E.
Published: October 2005

Adsorption films’ mechanical properties are discussed. With regard to a problem of bubble oscillations in a surfactant solution, dynamical boundary conditions at the bubble wall are modified by including a new term to account for a normal force component caused by dilational elasticity of an adsorbed film. Consequently, the Rayleigh–Plesset equation acquires a term which affects the restoring force of bubble oscillations. A linearized theory (for small-magnitude oscillations) is developed which shows that the film dilational elasticity induces a change in the mean radius and a shift in the natural frequency of bubble oscillations. These effects become extremely important when a capillary component 2σ/R0 accounts for at least 20% of the total pressure inside the bubble.
Perception of intervocalic stop consonants: The contributions of closure duration and formant transitions
Authors: Tartter Vivien C. , Kat Donna , Samuel Arthur G. , Repp Bruno H.
Published: October 2005

Acoustic analyses of vowel–consonant–vowel (VCV) utterances indicate that they generally include formant transitions from the first vowel into a period of closure (VC transitions), and transitions out of the closure into the second vowel (CV transitions). Three experiments investigated the perceptual importance of the VC transitions, the CV transitions, and the closure period in identification of medial stop consonants varying in place of articulation. Experiment 1 compared identification of members of synthetic VC and CV continua with those from VCV series made by concatenating corresponding VC and CV stimuli using various closure durations. Experiment 2 examined identification of VCV stimuli constructed with only VC, only CV, or both VC and CV transitions; again closure duration was systematically varied. Experiment 3 correlated CV and VC identification with identification of VCV stimuli. Neither closure duration nor formant transition structure (i.e., only VC, only CV, or both) had an independent effect on identification. Instead, the formant structure and closure duration together strongly affected stop identification. When both VC and CV transitions were present, the CV transitions contributed somewhat more to identification of medial stops with short closures, than the VC transitions did. With longer closure durations, neither set of transitions appeared to determine perceived place of articulation in any simple way. Overall, the data indicate that the perception of a medial consonant is more than simply a (weighted) sum of its parts.
Intelligibility of VCV segments excised from connected speech
Authors: Schmidt-Nielsen A.
Published: October 2005

Confusions between pairs of intervocalic consonants excised from connected speech were investigated under several conditions of speech degradation: digital voice processing, noise, and bandpass limiting. The distribution of the types of errors that were made, e.g., voicing, nasality, place of articulation, differed from those made on citation form syllable-initial consonants. Intervocalic consonants that were taken from word-initial position scored higher with no degradations than those taken from word-medial or word-final position, but the medial and final segments suffered less under mild degradations than did the initial ones.
Experimental manipulation of speaking rate for studying temporal variability in children’s speech
Authors: Smith Bruce L. , Sugarman Michael D. , Long Steven H.
Published: October 2005

Children’s speech timing is often more variable than adults’. In the present study, two hypotheses that have been proposed to account for this observation are considered. One claims that children do not have neuromotor control capabilities comparable to adults. The other suggests that the greater variability is a statistical consequence of children’s longer segment durations. These two hypotheses were examined by having children and adults speak at both faster and slower rates than normal. Within-group comparisons across different rates and between-group comparisons for similar durational values were made from spectrographic measurements. Results indicate that both statistical and neuromotor factors seem to contribute to the greater variability commonly observed in children’s speech.