bluuebunny/crossref_metadata_2025 huggingface dataset:
Flexural resonances in obliquely insonified solid elastic spheroids
Authors: Werby M. F. , Gaunaurd G. C.
Published: October 2005

Form functions ‖ f∞‖ from submerged solid elastic spheroids generated by an obliquely incident plane wave contain a variety of resonance features. Predictions are presented for these form functions obtained by means of the T-matrix method in the frequency band: 2≤kL/2≤24, as the aspect ratio (L/D) varies in the interval: 1.5≤L/D≤5, and the oblique incidence is kept at an angle of 45° with the axis of the spheroid. The lowest of the observed resonances starts to appear at kL/2 values that are approximately inversely proportional to the aspect ratio of the spheroid, a fact which is the converse of that for Rayleigh resonances. To determine the nature of these resonances, the spheroid is assumed to be a free–free Timoshenko beam of (constant) circular cross section and the same L/D as the spheroid, excited into reradiation by the obliquely incident wave. The resonances obtained by this simple Timoshenko-beam model, and those obtained by the T-matrix method agree quite closely at all aspect ratios. The comparison also verified the trend toward lower resonances as L/D increases. Therefore, this study shows that these are flexural (bending) resonances caused by the transverse oscillations of the spheroid as a free–free beam when it is excited by the obliquely incident wave.
Vertical spatial coherence of scattering from the Arctic ice canopy: Comparison of theory with experiment
Authors: McDaniel Suzanne T.
Published: October 2005

The results of experiments to measure the vertical spatial coherence of the high-frequency acoustic field scattered from the Arctic ice canopy are presented. The dependence of the coherence on measurement geometry is found to be in agreement with theoretical predictions based on the method of physical optics. In addition, analyses to isolate the effects of under-ice roughness on the coherence yield results in accord with theoretical predictions.
Reply to ‘‘Comment on ‘A cochlear model for acoustic emissions’ ’’ [J. Acoust. Soc. Am. 8
5, 2217 (1989)]
Authors: Furst Miriam
Published: October 2005

The predictions of the cochlear nonlinear transmission line model of Furst and Lapid [J. Acoust. Soc. Am. 84, 222–229 (1988)] with respect to spontaneous otoacoustic emission (SOAE) are discussed. The experimental data, quoted in Wit’s comment [J. Acoust. Soc. Am. 85, xx–xxxx (1989)] as an indication of the presence of a self-sustained oscillator in the cochlea, are represented as obtained by the model. The model as it stands is shown to be capable of producing realistic SOAE.
A reexamination of the role of wave–wave interactions in ocean noise generation
Authors: Kibblewhite A. C. , Wu C. Y.
Published: October 2005

A close connection between microseisms and ocean-wave activity has been recognized for many years. Various mechanisms have been proposed to explain the interaction, most favored being nonlinear interactions between ocean surface waves. Interest in these processes has increased in recent years as underwater acousticians have extended their investigations to infrasonic frequencies. This contribution builds on a study recently reported that confirmed the role of nonlinear wave–wave interactions at infrasonic frequencies but left some questions unresolved.
Synchronized discharge rate representation of voice-onset time in the chinchilla auditory nerve
Authors: Sinex Donal G. , McDonald Lynn P.
Published: October 2005

Responses of chinchilla auditory nerve fibers to synthesized stop consonant syllables differing in voice-onset time (VOT) were obtained. The syllables, heard as /ga/–/ka/ or /da/–/ta/, were similar to those previously used by others in psychophysical experiments with human and chinchilla subjects. Synchronized discharge rates of neurons tuned to frequencies near the first formant increased at the onset of voicing for VOTs longer than 20 ms. Stimulus components near the formant or the neuron’s characteristic frequency accounted for the increase. In these neurons, synchronized response changes were closely related to the same neuron’s average discharge rates [D. G. Sinex and L. P. McDonald, J. Acoust. Soc. Am. 83, 1817–1827 (1988)]. Neurons tuned to frequency regions near the second and third formants usually responded to components near the second formant prior to the onset of voicing. These neurons’ synchronized discharges could be captured by the first formant at the onset of voicing or with a latency of 50–60 ms, whichever was later. Since these neurons’ average rate responses were unaffected by the onset of voicing, the latency of the synchronized response did provide an additional neural cue to VOT. Overall, however, discharge synchrony did not provide as much information about VOT as was provided by the best average rate responses. The results are compared to other measurements of the peripheral encoding of speech sounds and to aspects of VOT perception.
The measurement of loudness in individual children and adults by absolute magnitude estimation and cross-modality matching
Authors: Collins Amy A. , Gescheider George A.
Published: October 2005

Twelve adults and 11 children (age range 4–7 years) performed absolute magnitude estimation of the apparent lengths of lines and the loudnesses of 1000-Hz tones as well as cross-modality matching between loudness and apparent line length. Consistent with the notion that children and adults have similar impressions of loudness, there were no major differences between the absolute magnitude estimation (AME) and cross-modality matching (CMM) data of the adults and children. A direct comparison between the exponents for loudness by AME and CMM was made when a correction factor was employed to eliminate the effects of idiosyncratic use of numbers from the AME exponents. The results support the hypothesis that, with proper instructions, both children and adults can judge stimuli on an absolute scale. Specifically, for 9 out of 12 adults and 9 out of 11 children, lines and tones assigned the same number in absolute magnitude estimation were judged to be subjectively equal in cross-modality matching.
Dynamic specification of coarticulated vowels spoken in sentence context
Authors: Strange Winifred
Published: October 2005

According to a dynamic specification account, coarticulated vowels are identified on the basis of time-varying acoustic information, rather than solely on the basis of ‘‘target’’ information contained within a single spectral cross section of an acoustic syllable. Three experiments utilizing digitally segmented portions of consonant–vowel–consonant (CVC) syllables spoken rapidly in a carrier sentence were designed to examine the relative contribution of (1) target information available in vocalic nuclei, (2) intrinsic duration information specified by syllable length, and (3) dynamic spectral information defined over syllable onsets and offsets. In experiments 1 and 2, vowels produced in three consonantal contexts by an adult male were examined. Results showed that vowels in silent-center (SC) syllables (in which vocalic nuclei were attentuated to silence leaving initial and final transitional portions in their original temporal relationship) were perceived relatively accurately, although not as well as unmodified syllables (experiment 1); random versus blocked presentation of consonantal contexts did not affect performance. Error rates were slightly greater for vowels in SC syllables in which intrinsic duration differences were neutralized by equating the duration of silent intervals between initial and final transitional portions. However, performance was significantly better than when only initial transitions or final transitions were presented alone (experiment 2). Experiment 3 employed CVC stimuli produced by another adult male, and included six consonantal contexts. Both SC syllables and excised syllable nuclei with appropriate intrinsic durations were identified no less accurately than unmodified controls. Neutralizing duration differences in SC syllables increased identification errors only slightly, while truncating excised syllable nuclei yielded a greater increase in errors. These results demonstrate that time-varying information is necessary for accurate identification of coarticulated vowels. Two hypotheses about the nature of the dynamic information specified over syllable onsets and offsets are discussed.
An auditory basis for the stimulus-length effect in the perception of stops and glides
Authors: Diehl Randy L. , Walsh Margaret A.
Published: October 2005

To investigate possible auditory factors in the perception of stops and glides (e.g., /b/ vs /w/), a two-category labeling performance was compared on several series of /ba/–/wa/ stimuli and on corresponding nonspeech stimulus series that modeled the first-formant trajectories and amplitude rise times of the speech items. In most respects, performance on the speech and nonspeech stimuli was closely parallel. Transition duration proved to be an effective cue for both the stop/glide distinction and the nonspeech distinction between abrupt and gradual onsets, and the category boundaries along the transition-duration dimension did not differ significantly in the two cases. When the stop/glide distinction was signaled by variation in transition duration, there was a reliable stimulus-length effect: A longer vowel shifted the category boundary toward greater transition durations. A similar effect was observed for the corresponding nonspeech stimuli. Variation in rise time had only a small effect in signaling both the stop/glide distinction and the nonspeech distinction between abrupt and gradual onsets. There was, however, one discrepancy between the speech and nonspeech performance. When the stop/glide distinction was cued by rise-time variation, there was a stimulus-length effect, but no such effect occurred for the corresponding nonspeech stimuli. On balance, the results suggest that there are significant auditory commonalities between the perception of stops and glides and the perception of acoustically analogous nonspeech stimuli.
Transient wave propagation in wooden plates for musical instruments
Authors: Molin N.-E. , Jansson E. V.
Published: October 2005

Transient bending waves in three wooden plates are studied. A rectangular flat spruce plate (from a guitar top plate) and two arched violin plates (of spruce and maple, respectively) are impacted by a small ballistic pendulum. The impact point is at the center of the guitar plate and the bridge position of the violin plates. A sequence of holographic interferograms of the events is recorded using a double pulsed ruby laser as the light source. The holographic setup is a standard one. The elliptical shape of the interference fringes shows that wood is strongly anisotropic. The shape of the propagating pulse changes with time, which shows the dispersive behavior of bending waves in plates. A solution of the isotropic Euler plate equation for a flat plate is compared to experimental results of the guitar plate, assuming that this description is adequate along the main axes of this orthotropic plate. The shape of the propagating wave pattern and the elliptical rather than circular shape of the violin imply an interesting coincidence.
Finite amplitude effects in a dual frequency acoustic beam
Authors: Foda M. A. , Ginsberg J. H.
Published: October 2005

When an axisymmetric, bifrequency transducer mounted in a rigid baffle is excited at acoustic Mach numbers that are a relatively large fraction, the result is a dual frequency sound beam that exhibits harmonic and intermodulation distortion. The present analysis of this problem develops a perturbation solution based on a wave equation that consistently accounts for nonlinearity and diffraction. The linearized problem is described by a King integral for the sound beam at each primary frequency. Asymptotic analysis using Laplace’s method of integration is used to find the second-order potential. The method of renormalization then leads to a uniformly accurate expression for the acoustic pressure. A technique for improvement in computational efficiency is developed by interfacing the King integral predictions to a farfield model for quasispherical waves. Propagation curves for parametric arrays obtained from the model compare favorably with experimental observations.
A bistatic, high-frequency, under-ice, acoustic scattering model. I: Theory
Authors: Bishop Garner C.
Published: October 2005

A model is described that has been developed to evaluate the scatter produced by a high-frequency acoustic pulse that originates from a stationary and arbitrarily located source; is incident on and scattered from an under-ice surface characteristic of pack ice regions of the interior Arctic; and is detected by a stationary and arbitrarily located receiver. Measured, two-dimensional, under-ice, acoustic profile data and several empirical results that relate various geometric parameters of large-scale under-ice relief features (e.g., ice keels) are used to construct a three-dimensional, under-ice surface model consisting of first-year ice keels and sloping, flat ice regions. A first-year ice keel is modeled as an ensemble of randomly oriented ice blocks on a planar surface inclined at some slope angle with respect to a horizontal plane at sea level. Ice blocks are modeled as layered, viscoelastic solids with smooth rectangular faces or facets. A region of flat ice is modeled as a smooth planar surface whose slope angle is less than some arbitrary minimum slope angle. The Helmholtz–Kirchhoff integral equation and the Kirchhoff approximation are used to evaluate the scattered pressure field. Time is partitioned into bins and, beginning at the bin corresponding to the time the scattered pressure field of each scattering facet arrives at the receiver, the scattered pressure field is added coherently in all bins spanning the temporal duration of the incident pulse.
Could temporal order differences underlie 2-month-olds’ discrimination of English voicing contrasts?
Authors: Jusczyk Peter W. , Rosner Burton S. , Reed Marjorie A. , Kennedy Lori J.
Published: October 2005

Previous studies have shown that infants discriminate voice onset time (VOT) differences for certain speech contrasts categorically. In addition, investigations of nonspeech processing by infants also yield evidence of categorical discrimination of temporal-order differences. These findings have led some researchers to argue that common auditory mechanisms underlie the infant’s discrimination of timing differences in speech and nonspeech contrasts [e.g., Jusczyk et al., J. Acoust. Soc. Am. 67, 262–270 (1980)]. Nevertheless, some discrepancies in the location of the infant’s category boundaries for different kinds of contrasts have been noted [e.g., Eilers et al. (1980)]. Because different procedures were used to study the different kinds of contrasts, interpretation of the discrepancies between the studies has been difficult. In the present study, three different continua were examined: [ba]–[pa] stimuli, which differed in VOT; [du]–[tu] stimuli, which differed in VOT but which lacked format transitions; nonspeech formant onset time (FOT) stimuli that varied in the time that lower harmonics increased in amplitude. An experiment with adults indicated a close match between the perceptual boundaries for the three series. Similarly, tests with 2-month-old infants using high amplitude sucking procedure yielded estimates of perceptual category boundaries at between 20 and 40 ms for all three stimulus series.
Comments on ‘‘Earphones in audiometry’’ [Zwislocki e
t a
l., J. Acoust. Soc. Am. 8
3, 1688–1689 (1988)]
Authors: Killion Mead C. , Villchur Edgar
Published: October 2005

The Zwislocki et al. [‘‘Earphones in Audiometry,’’ J. Acoust. Soc. Am. 83, 1688–1689 (1988)] Letter to the Editor states that insert earphones have some unresolved technical problems, such as limited frequency response, limited dynamic range and power handling capability, intersubject variability, and hygiene safety. In evaluating circumaural earphones, Zwislocki et al. say that the lack of a standard coupler disqualifies them for audiometry. Since this letter carries the weight of a CHABA committee recommendation, these issues are commented on herein. Section I was written primarily by Mead Killion and Sec. II primarily by Edgar Villchur. For brevity throughout, the authors of the Zwislocki et al. letter will be referred to as ‘‘the authors.’’
On the analysis of acoustic resonance measurement
Authors: Ewing M. B. , Trusler J. P. M.
Published: October 2005

A new and more efficient iterative algorithm is described for fitting amplitude and phase information determined with an acoustic resonator to a theoretically predicted function of the drive frequency. The method, which takes account of background, offers the same accuracy as the best previous technique but requires only about one-sixth of the computation time.
A structured gradient algorithm for adaptive beamforming
Authors: Godara L. C. , Gray D. A.
Published: October 2005

The constrained least-mean-square (LMS) algorithm uses a noisy estimate of the required gradient to adaptively estimate the weights of an optimal antenna array. The gradient is estimated by multiplying the array output with the array receiver outputs. An alternative scheme for estimating the required gradient is proposed in this paper. The new scheme uses a structured estimate of the array correlation matrix to estimate the gradient. This structure reflects the structure of the exact array correlation matrix and is obtained by a spatial averaging of the elements of the noisy array correlation matrix used in the standard algorithm. It is shown that the estimated gradient is unbiased and the array weights converge to the optimal weights in the mean sense. Furthermore, the weights estimated by the structured gradient algorithm are less noisy than those estimated by the standard algorithm.
Flow velocity field tomography using multiple ultrasonic beam detectors and high-order correlation analysis
Authors: Jhang Kyung-Young , Sato Takuso
Published: October 2005

A new method for tomographic reconstruction of a two-dimensional (2-D) velocity field that consists of a set of curved streams with corresponding constant curvatures along each stream with statistically independent fluctuations is proposed. In this method, five ultrasonic beams, which are arranged in proper positions and directions, are used as the line detectors and the fifth-order correlation analysis is applied to the detected data. In this case, the information about each stream is transformed into a corresponding peak in the fifth-order correlation space. Hence, the velocity field can be reconstructed by finding flow parameters from the measured correlation data in connection with the geometries of the measuring system. The usefulness of this method is confirmed by computer simulations as well as experiments that are carried out by using a 4.5-MHz ultrasonic wave system.
Analysis of wave motion in even- and odd-dimensional acoustic media using Radon transform
Authors: Carrion Philip M. , Foster Douglas J.
Published: October 2005

In this paper, a solution to the acoustic wave equation using a Radon transform is analyzed. It is shown that the application of the Radon transform leads to the fundamental concept of the Huygens’ rings in multidimensional acoustic spaces. It is also shown that Huygens’ rings occur in odd-dimensional spaces and determine the localization of acoustic waves in space. It is proved that in even-dimensional spaces, the concept of Huygens’ rings is no longer valid and thus breaks down the local distribution of acoustic waves in space. These statements are demonstrated by using a numerical example treating an inhomogeneous acoustic medium.
Applications and time-domain solution of higher-order parabolic equations in underwater acoustics
Authors: Collins Michael D.
Published: October 2005

A higher-order parabolic equation and the corresponding higher-order time-domain parabolic equation are derived from a Padé series and solved numerically. These models provide accurate solutions for problems involving very-wide-angle propagation (e.g., propagation in the nearfield or over a hard ocean bottom); propagation in domains in which sound-speed variations are large (e.g., propagation in deep water, deep within the ocean bottom, in high-speed ocean bottoms, and possibly of different wave types); and propagation out to very long ranges. The possibility of modeling elastic wave propagation with a similar approach is considered.
Application of the method of moments to acoustic scattering from multiple bodies of arbitrary shape
Authors: Rao Sadasiva M. , Raju P. K.
Published: October 2005

The method proposed in this paper provides a computational technique for solving acoustic scattering problems associated with arbitrarily shaped, three-dimensional bodies. In particular, using the free-space Green’s function along with the associated boundary conditions on the surface of the body, integral equations to calculate the velocity potential and the exterior field of the scattering body are derived. The equations are then solved by approximating the scatterers by planar triangular patches and using the method of moments. Test cases are shown involving single and multiple bodies of spherical, cylindrical, and cubical geometry. The method presented in this paper is novel, simple, and efficient and yet general enough to obtain the sonic fields scattered by multiple arbitrarily shaped bodies oriented in random fashion.
Waves in a gel-saturated porous solid
Authors: White J. E. , Wang Ke Xie
Published: October 2005

A treatment of waves in a viscoelastic gel filling a rigid cylindrical cavity shows that, when the wall of the cavity executes axial motion, resonances occur at certain frequencies characterized by large displacements and high energy loss. Application of these results to shear waves in a ‘‘porous solid’’ consisting of parallel tubes in an elastic skeleton produces attenuation that is orders of magnitude greater for gel saturation than for fluid saturation. The mechanism of energy loss is applied to a more realistic pore geometry by repeating the derivation of the Biot theory with addition of a small shear rigidity to the saturating phase. Calculations show that attenuation and dispersion are greatly increased for compressional waves, type-II dilatational waves, and shear waves. Even so, the computed decrements are not substantially larger than the decrements measured for typical porous rocks.
Attenuation of sound in marine sediments: A review with emphasis on new low-frequency data
Authors: Kibblewhite Alick C.
Published: October 2005

In many situations, the acoustic properties of the bottom are important, and considerable effort has been directed at their elucidation over the whole frequency range of interest to underwater acoustics. At low frequencies, experimental measurement of these properties is particularly difficult and uncertainty exists in the values of some key parameters. The determination of compressional and shear wave attenuation has been especially challenging and it is not surprising that debate has persisted as to the magnitude of this property and its overall dependence on frequency at low frequencies. This paper attempts to examine this question through a review of the relevant literature from rock mechanics and underwater acoustics, with a special emphasis on low-frequency data.
Pressure variation above a layer of absorbing material and impedance measurement at oblique incidence and low frequencies
Authors: Allard Jean F. , Champoux Yvan , Nicolas Jean
Published: October 2005

Measurements of the ratio of the acoustical pressures at two points above a sample of typical glass wool are performed for various angles of incidence and various distances from the sound source to the sample. The measurements are compared with predictions made using a recent model, and are used to estimate the surface impedance of the material at oblique incidence. It appears that, for the material studied, surface impedance measurements are possible for frequencies as low as 300 Hz and angles of incidence between 0° and 75°, as long as the source–sample distance is larger than half the sound wavelength in air.
Ray theory solution for finite amplitude effects in a two-dimensional hard-walled waveguide
Authors: Shu Kun-Tien , Ginsberg Jerry H.
Published: October 2005

Ray theory and perturbation analysis are combined to analyze the cumulative growth of nonlinear effects resulting from excitation of a single nonplanar mode in a two-dimensional waveguide whose walls are rigid. The first-order (linear) signal is decomposed into a pair of obliquely propagating planar waves. The signal associated with each ray is required to satisfy the inhomogeneous second-order wave equation. A single ray emanating from its source is followed to its first incidence at one wall, and the reflection of such a ray is determined by requiring that incident and reflected rays combine to satisfy the hard-wall boundary condition. The method of images then leads to a generalization of the result to the case of a ray that undergoes multiple reflections. Nonuniform validity of the ray signal determined in this manner is corrected by the method of renormalization, which leads to the conclusion that a ray behaves like a simple nonlinear planar wave, except that the propagation distance is measured by tracing the ray back to its source. The overall signal at a specified field point is determined by superposing the signals associated with the two rays that intersect at that location. The result is shown to be in complete agreement with earlier modal analyses of the same problem, provided that the frequency is sufficiently low to inhibit resonant energy transfer between nearly parallel rays. Although the analysis is less direct than that used previously, it yields physical insight into the distortion process not previously available.
Variational principle for scattering by a baffled cavity-backed membrane
Authors: Lamb G. L.
Published: October 2005

The reflection of a plane sound wave by an infinite plane baffle containing a circular aperture spanned by a membrane that is backed by a closed cylindrical cavity is investigated theoretically. A variational expression for the amplitude of backscattered radiation at normal incidence is derived and results based upon this expression are compared with those obtained by others using the method of matched asymptotic expansions.
Forward-masking properties of multicomponent signals in normal and hearing-impaired subjects
Authors: Kim Munah , Turner Christopher W. , Relkin Evan M.
Published: October 2005

The forward-masking properties of inharmonic complex stimuli were measured both for normal and hearing-impaired subjects. The signal threshold for a 1000-Hz pure-tone probe was obtained for six different maskers, which varied in the number of pure-tone components. The masking stimuli consisted of 1, 3, 5, 7, 9, or 11 components, logarithmically spaced in frequency surrounding the signal and presented at a fixed level of 80 dB SPL per component. In most normal-hearing subjects, the threshold for the probe decreased as the number of masking components was increased, demonstrating that stimuli with more components tended to be less effective maskers. Results from hearing-impaired subjects showed no decrease in threshold with increasing number of masking components. Instead, the thresholds increased as more components were added to the first masker. These results appear to be consistent with suppression effects within the multicomponent maskers for the normal subjects and a lack of suppression effects for the hearing-impaired subjects. The results from the normal-hearing subjects are also consistent with ‘‘across-channel’’ cuing.
Measurements of acoustic phase stability in Loch Linnhe, Scotland
Authors: Gough Peter T. , Hayes Michael P.
Published: October 2005

The temporal phase stability of the acoustic environment is vital to the formation of a synthetic aperture. Acoustic phase stability measurements were made of the water in Loch Linnhe, Scotland over a period of several days. The phase stability was estimated from a sequence of phase measurements made over periods of 1 and 15 min. Over periods of a minute, it was found that the standard deviation of the fluctuations around the mean phase was 10°. Moreover, for frequencies in the band 15–30 kHz, the standard deviation was independent of frequency. This implies that the standard deviation measured is limited by the measurement accuracy of the experiment rather than a measure of the actual acoustic stability of the medium. Consequently, it is concluded that the acoustic phase stability is better than 10° for all frequencies and that the path-length variation due to medium fluctuations is smaller than 6 mm in a total acoustic path of 130 m.
The fictitious eigenvalue difficulty in the T-matrix and the BEM methods for exterior wave scattering
Authors: Shaw Richard Paul , Huang S.-C.
Published: October 2005

Exterior time-harmonic wave scattering by finite obstacles in infinite domains has been studied extensively by both boundary element methods (BEM) and transfer-matrix (T-matrix) methods. The former is essentially a local discretization numerical approach, while the latter is basically a global ‘‘eigenfunction’’ expansion approach and thus these two approaches represent in some sense an ‘‘alpha and omega’’ of approximation solution method. Since these are both based on a Helmholtz integral equation formulation, which is known to fail at certain eigenvalues of a related interior problem, one could expect corresponding failures in these approximate methods. Such failures are well known in the BEM literature; they are recognized in principle but are essentially ignored in practice in the T-matrix literature. This paper studies this disparity through a simple example where the T-matrix approach is seen to fail over such a narrow frequency band near the interior eigenvalues that finding such failures in a standard solution procedure using discrete frequency values is highly unlikely. However, a related eigenfunction expansion method yields the same broadband failure as found in BEM indicating that this is not simply a result of eigenfunction versus element accuracy.
Directional sensitivity of sound-pressure levels in the human ear canal
Authors: Middlebrooks John C. , Makous James C. , Green David M.
Published: October 2005

Changes in sound pressures measured in the ear canal are reported for broadband sound sources positioned at various locations about the subject. These location-dependent pressures are one source of acoustical cues for sound localization by human listeners. Sound source locations were tested with horizontal and vertical resolution of 10°. Sound levels were measured with miniature microphones placed inside the two ear canals. Although the measured amplitude spectra varied with the position of the microphone in the ear canal, it is shown that the directional sensitivity at any particular frequency of the broadband stimulus is independent of microphone position anywhere within the ear canal. At any given frequency, the distribution of sound pressures as a function of sound source location formed a characteristic spatial pattern comprising one or two discrete areas from which sound sources produced maximum levels in the ear canal. The locations of these discrete areas varied in horizontal and vertical location according to sound frequency. For example, around 8 kHz, two areas of maximum sensitivity typically were found that were located laterally and were separated from each other vertically, whereas, around 12 kHz, two such areas were found located on the horizontal plane and separated horizontally. The spatial patterns of sound levels were remarkably similar among different subjects, although some frequency scaling was required to accommodate for differences in the subjects’ physical sizes. Interaural differences in sound-pressure level (ILDs) at frequencies below about 8 kHz tended to increase monotonically with increasing distance of the sound source from the frontal midline and tended to be relatively constant as a function of vertical source location. At higher frequencies, however, ILDs varied both with the horizontal and with the vertical location of the sound source. At some frequencies, asymmetries between the left and right ears in a given subject resulted in substantial ILDs even for midline sound sources. These results indicate the types of horizontal and vertical spatial information that are available from sound level cues over various ranges of frequency and, within a small subject population, indicate the nature of intersubject variability.
The acoustic behavior of the fish-catching bat, N
o
c
t
i
l
i
o l
e
p
o
r
i
n
u
s, during prey capture
Authors: Hartley David J. , Campbell Karen A. , Suthers Roderick A.
Published: October 2005

Many bats change the acoustic parameters of their echolocation calls in a deliberate manner during prey capture. Attempts to quantify these changes have been either of limited scope or subject to potentially severe errors due to an inadequate consideration of the directionality of both the bat and the recording microphone. Therefore, the echolocation pulses emitted by two N. leporinus have been recorded as they approached and captured stationary prey, with the microphone positioned in such a way that the structure of the pulses incident upon the target could be determined. The results of this study show that: (1) during the last 1.5 m of the approach, N. leporinus reduces the intensity of emitted pulses by 6 dB per halving of distance, so that the intensity incident upon the target is constant; (2) at a point in the pulse train that corresponds to the position of the hypothesized tracking phase of echolocation, N. leporinus selectively reduces the intensity of the frequency-modulated (FM) fundamental so that the FM pulse component is predominantly second harmonic; and (3) a high degree of temporal overlap occurs between the FM component of emitted pulse and echo when N. leporinus is within 0.4 m of its prey.
The acoustical input impedance of excised human lungs—Measurements and model matching
Authors: Hudde Herbert , Slatky Harald
Published: October 2005

The input impedance at primary bronchi of excised human lungs was measured in the frequency range from 2–5000 Hz. For the measurements, a self-developed acoustic impedance head and a narrow-band measuring system with sinusoidal excitation were used. The lungs were inflated and deflated by using an arrangement called respiratory state controller. The impedances were thus measured at different states of lung inflation. An already existing mathematical model was developed further to cover not only fairly inflated lungs, but also deflated ones. The parameter sensitivity of this model is investigated. The acoustomechanical parameters of the model were fitted to match the impedances measured. It turns out that some of these parameters are hardly calculable. The values given in this paper were chosen to agree with the measurements and to be physically reasonable. Although the measurements were performed at primary bronchi, the model is able to predict also impedances at the top end of the trachea (at different respiratory states). This impedance is useful for speech signal processing applications. The model prediction of the trachea impedances agrees well with previous results of other authors.
The application of a fractal model to the scattering of ultrasound in biological media
Authors: Javanaud Clarissa
Published: October 2005

The implications of a fractal model of medium structure for the angular dependence of the ultrasonic differential scattering cross section and for the frequency dependence of the total ultrasonic scattering cross section are explored. The results for the differential scattering cross section agree well with published experimental values for liver and those for the total scattering cross section are not inconsistent with the literature data.
Formant frequencies of choir singers
Authors: Ternström Sten , Sundberg Johan
Published: October 2005

The four lowest formant frequencies were measured in eight members of the bass section of a good amateur choir under two conditions: (1) when reading the text of a poem aloud; and (2) when performing the same text as a song. Certain formant frequency differences were observed that were similar to those previously found between professional singers’ spoken and sung vowels. In singing, the intersubject scatter of the three lowest formant frequencies was smaller, and the fourth formant was lower.
Detection and discrimination of synthetic English vowels by Old World monkeys (C
e
r
c
o
p
i
t
h
e
c
u
s, M
a
c
a
c
a) and humans
Authors: Sinnott Joan M.
Published: October 2005

Abilities to detect and discriminate ten synthetic steady-state English vowels were compared in Old World monkeys (Cercopithecus, Macaca) and humans using standard animal psychophysical procedures and positive-reinforcement operant conditioning techniques. Monkeys’ detection thresholds were close to humans’ for the front vowels /i–I–q–1–W/, but 10–20 dB higher for the back vowels /v–a–c–U–u/. Subjects were subsequently presented with groups of vowels to discriminate. All monkeys experienced difficulty with spectrally similar pairs such as /v–a/, /q–1/, and /U–u/, but macaques were superior to Cercopithecus monkeys. Humans discriminated all vowels at 100% correct levels, but their increased response latencies reflected spectral similarity and correlated with higher error rates by monkeys. Varying the intensity level of the vowel stimuli had little effect on either monkey or human discrimination, except at the lowest levels tested. These qualitative similarities in monkey and human vowel discrimination suggest that some monkey species may provide useful models of human vowel processing at the sensory level.
Detection of noise with rippled spectra by the Atlantic bottlenose dolphin
Authors: Au Whitlow W. L. , Pawloski Jeffrey L.
Published: October 2005

A dolphin was required to discriminate between rippled and nonrippled noise projected by an underwater transducer. Random noise was summed with its delayed replica to produce noise having ripples separated by 1/T Hz in the frequency domain, where T is the delay time. Three different experiments were conducted in which a dolphin was required to discriminate rippled and nonrippled noise using both cos+ and cos− stimuli. In the first experiment, the dolphin detected the cos− rippled stimulus at a correct response level of at least 75% for delays between 15 and 500 μs, and the cos+ rippled stimulus for delays of 13 to 190 μs. In the second experiment, the dolphin’s sensitivity to rippled noise was measured by attenuating the delayed replica for different delays. The dolphin was most sensitive for a delay of 100 μs. Its sensitivity at 100 μs was 5 dB better for the cos+ than the cos− stimuli. In the third experiment, broadband cos+ noise was also filtered in different 1/3 octave bands to determine if the animal’s sensitivity to rippled noise was a function of the center frequency of the noise. The dolphin’s performance was relatively constant as a function of center frequency. The overall results suggest that dolphins may be able to perceive time-separation pitch (TSP).
Correlations between sound field characteristics and subjective ratings on reproduced music sound quality
Authors: Tannaka Yasuaki , Koshikawa Tsuneji
Published: October 2005

The partial-space power, a sound field property for a loudspeaker, was newly defined in order to obtain general characteristics including on-axis sound pressure and total-space power. For typical loudspeakers, it was confirmed that the partial-space-power frequency response reflects the principal features, dips, peaks, and gradients of space-averaged sound-pressure frequency response in ordinary rooms. An all-inclusive listening test was performed with six subjective rating scales for ten loudspeakers. Then, the correlation between the sound field characteristics and the subjective rating data were examined. The sound dispersion as well as the frequency response seems to correlate with most normally employed subjective rating scales used in listening tests.
The running autocorrelation function of different music signals relating to preferred temporal parameters of sound fields
Authors: Ando Yoichi , Okano Toshiyuki , Takezoe Yoshitaka
Published: October 2005

This paper defines the minimum value of the effective duration of the running autocorrelation function of a music signal used in subjective preference testing. A short duration signal, which may relate to ‘‘psychological present,’’ is more suitable for calculating the most preferred time delay of the single reflection than is the long-time autocorrelation function. This fact is found particularly when passages of Japanese music are being played, which include a wide-range-noise component at the very beginning of the signal and the so-called ‘‘MA.’’ MA is a stationary sound passage without any rapid movement. This paper also shows that, for subsequent reverberation time, a flat frequency response may be in the range of preferred conditions. Such preferred conditions may be calculated by the minimum effective duration of the running autocorrelation function of source signals after passing through the A-weighting network.
Analysis of two-dimensional acoustic scattering from periodic structures using a hybrid source model
Authors: Boag Amir , Leviatan Yehuda , Boag Alona
Published: October 2005

A method of moments solution is presented for the problem of two-dimensional acoustic scattering of a plane wave from a general piecewise homogeneous periodic structure. The reduction of the general problem to a consideration of the fields over a suitably selected period, referred to as the unit cell, is facilitated by the Floquet theorem. The solution then uses fictitious spatially periodic and properly modulated strip sources to simulate the fields in homogeneous regions crossed by the unit cell boundaries and fictitious filamentary sources to simulate the fields in homogeneous regions completely enclosed within this cell. The fields radiated by the strip sources are represented in terms of Floquet modes. Finally, the simulated fields are forced to obey the continuity conditions for the pressure and the normal component of the velocity at selected sets of points on the boundaries among the regions within the unit cell. The procedure is simple to implement, rapidly converging, and is applicable to structures of arbitrary smooth cross section. Acoustically rigid and soft regions are also treated within the general procedure. Results are given and compared with available data and with an analytic approximation.
Three-dimensional finite element analysis of waves in an acoustic medium with inclusion
Authors: Teng Yu-Chiung
Published: October 2005

By using the pressure field as the basic unknown variable, 2 three-dimensional acoustic finite element algorithm computer codes, viz., ACOU3.A and ACOU3.B, have been implemented. Code ACOU3.A is designed for the uniform-grid space discretization such that the storage of the global pseudostiffness matrix is reduced to a single column vector of ‘‘27’’ elements, applicable to any inhomogeneous media. Likewise, code ACOU3.B is designed for the irregular-grid space descretization and possesses the same feature of a reduced global pseudostiffness matrix of ACOU3.A. By using ACOU3.A, three 30×30×30-element models, including (i) a half-space, (ii) a half-space with a 10×7×5-element inclusion, and (iii) a half-space with a 10×2×5-element inclusion, where the inclusion has the physical property different from the half-space, were investigated. In order to demonstrate the third-dimension effects on wave propagation, the above posed three-dimensional problem was reduced to the equivalent axial-symmetric and two-dimensional finite element models. By using a full three-dimensional algorithm, the amplitude of the reflected waves carries the information of the third-dimension thickness of the inclusion, which cannot be obtained by either the axial-symmetric or the two-dimensional approximations.
On the origin of the anomalies in the reflected ultrasonic spectra from periodic surfaces
Authors: Mampaert K. , Nagy P. B. , Leroy O. , Adler L. , Jungman A. , Quentin G.
Published: October 2005

This letter discusses the physical origin of the sharp minima observed in the reflection spectrum of normally incident ultrasonic waves from periodic free solid and solid–liquid interfaces. It is shown that Rayleigh wave generation along the surface does not necessarily produce a corresponding minimum in a reflected spectrum unless some mechanism of energy loss is involved as well.
Determination of the acoustic nonlinearity parameter in biological media using FAIS and ITD methods
Authors: Gong Xiu-fen , Zhu Zhe-ming , Shi Tao , Huang Jian-hong
Published: October 2005

Two methods for determination of the acoustic nonlinearity parameter B/A in biological media are presented. One is the finite amplitude insert-substitution method (FAIS), considering the influence of both the sound attenuation of samples and the diffraction of the transducer on the experimental measurement. The other is the improved thermodynamic method (ITD), based on the measurement of phase shifts in the acoustic wave due to the change of ambient pressure. The nonlinearity parameter B/A has been measured for various biological solutions and soft tissues using these two methods. Some results of dependence of B/A values on the concentration and temperature are also presented here.
Impedance characteristics of transducers and reciprocity calibration
Authors: Ge Li-Feng
Published: October 2005

This paper investigates impedance characteristics of electrodynamic-type and piezoelectric-type transducers. The inherent relation between mechanical impedance of a mass load and electrical impedance of the transducing element of transducers is revealed. The substance of reciprocity calibration is just to utilize the impedance inversive property of both types of transducers so that one can determine the mechanical quantities (force and velocity) by measuring electrical quantities, which can be measured conveniently and accurately. According to the theory, for high-frequency calibration, mass values in the reciprocity calibration formulas should be replaced by their equivalent masses rather than static mass values, because the mechanical impedances of mass loads will be remarkably changed due to the stress wave effect. Making the correction can improve calibration accuracy by about one-half order of magnitude.
An optimal PE-type wave equation
Authors: Berman David H. , Wright Evan B. , Baer Ralph N.
Published: October 2005

A one-way wave equation is presented with the following properties. (1) For low angles and small sound-speed variations, it reduces to the standard parabolic approximation. (2) It allows a split-step solution. (3) The rays associated with this equation are exactly the rays of the Helmholtz equation in a range-independent environment. It is in the last sense an optimal one-way wave equation. Results of the split-step solution of this equation are presented and compared to normal-mode calculations and results of another modification of the standard parabolic equation, which was given by Thomson and Chapman [D. J. Thomson and N. R. Chapman, J. Acoust. Soc. Am. 74, 1848–1854 (1983)].