bluuebunny/crossref_metadata_2025 huggingface dataset:
Perception of coloration in sound fields in relation to the autocorrelation function
Authors: Ando Yoichi , Alrutz Herbert
Published: October 2005

The perception of coloration was investigated in a sound field composed of a strong primary sound and a time-shifted (±Δt1) weak sound. As source signal a continuous bandpass noise was used. Subjects judged the sensation level of the weak sound in comparison to the situation in which only the primary sound was presented. The results are interpreted by means of the autocorrelation function of the bandpass noise signal.
Simple theory of the effects of medium turbulence upon scanning with an adaptive phased array
Authors: Steinberg Bernard D. , Luthra Ajay K.
Published: October 2005

Medium turbulence, characterized by local variations in propagation speed, limits array size to the order of the correlation distance of the velocity perturbation. Array gain is lost when the array size significantly exceeds that distance. Adaptive beamforming eliminates this size constraint on the array. However, the scanning distance then turns out to be limited, the amount being proportional to the correlation distance and the proportionality constant being a function of the scanning direction. The size and shape of the scanning sector is calculated, along with the number of resolution cells that it contains, both for passive and active sonar systems.
Differential patterns of physiological masking in the anuran auditory nerve
Authors: Megela Andrea L. , Capranica Robert R.
Published: October 2005

Single fibers in the eighth nerve of anurans exhibit varying rates of short-term adaptation in response to long duration tonal stimuli. In this report, we show that the response of an anuran auditory nerve fiber to a short probe tone presented 10–1000 ms after a long duration adapting tone depends on the fiber’s state of adaptation due to previous stimulation. These effects are most pronounced in fibers presumably originating from the amphibian papilla. Within this group of fibers, fast-adapting fibers, which are most sensitive to mid-frequency tones, showed greater response decrement than did slow-adapting fibers, which are most sensitive to low-frequency tones. Fibers tuned to higher frequency ranges, which presumably originate from the basilar papilla, showed response decrements similar to those shown by slow-adapting fibers from the amphibian papilla. These results indicate that anuran auditory nerve fibers, unlike mammalian auditory nerve fibers, are not homogeneous in their sensitivities to the effects of prior stimulation.
Frequency discrimination at 1200 Hz in the presence of high-frequency masking noise
Authors: Nelson David A. , Stanton Mary E.
Published: October 2005

To evaluate the possible contribution of high-frequency hearing to frequency discrimination at lower frequencies, pure-tone frequency discrimination tasks at 1200 Hz, with and without high-frequency masking noise, were performed by two highly practiced normal-hearing listeners. Signal levels ranged from 10 to 80 dB SPL. Spectra of the three high-frequency masking noises ranged from 1.8 to 2.1 kHz, from 2.8 to 3.1 kHz, and from 4 to 8 kHz. The frequency difference limen (DLF) intensity functions, describing DLFs as a function of signal level which were obtained in the presence of high-frequency masking noise, were essentially the same as the DLF intensity functions obtained without masking noise. These results indicate that high-frequency hearing is not necessary for acute frequency discrimination at low and at middle frequencies.
Transient complex and pure tone pitch changes by adaptation
Authors: Hall Joseph W. , Soderquist David R.
Published: October 2005

The effect of pitch adaptation by a complex stimulus was examined in two experiments. In experiment 1, a monaural complex tone pitch change was measured after ipsilateral or contralateral complex stimulus adaptation. While ipsilateral adaptation resulted in pitch changes away from the pitch of the adapting stimulus, no pitch change occurred for contralateral adaptation. The precision of pitch matching was reduced by both ipsilateral and contralateral adaptation. Experiment 2 examined whether the complex tone pitch changes in experiment 1 could be accounted for by pitch changes induced in the pure tone components. Results indicated that changes induced in the pure tone components were too small to account for the complex tone pitch shift magnitudes found in experiment 1. These results support a degree of independence of complex tone pitch from the pitches of the pure tone components. Results also supported pitch extractor specialization for a particular ear of stimulus presentation.
Binaural time/intensity trading
Authors: Nordby Knut , Rosness Ragnar , Skottun Bernt Christian
Published: October 2005

Time/intensity trading functions (Δt/ΔI) were established psychophysically by three subjects for three interaural intensity differences (ΔI) at ten mean intensity levels (?). The sound image of repeating, dichotic, all-pass clicks was centered, using the objective nullity method combined with the method of adjustment. It was found that trading ratios increased with increasing values of ΔI and tended to decrease with increasing ?. It is argued that for intensity induced neural latency (intensity and latency being inversely related) to account for time/intensity trading, a single intensity/latency curve is required. Since, for any particular mean stimulus intensity (?), the trading ratio increases with increasing ΔI, this requirement is not met; indicating that a single peripheral intensity-to-latency mechanism is not sufficient to account for time/intensity trading.
An automated directory listing retrieval system based on recognition of connected letter strings
Authors: Myers C. S. , Rabiner L. R.
Published: October 2005

In this paper we describe a system which is capable of recognizing spoken spelled names from a directory of names. These names are spelled in a connected fashion, i.e., without any pause between letters, over a dialed-up telephone line. This system uses a level building dynamic time warping algorithm to perform a time registration between the input speech and a sequence of letters drawn from isolated word templates. The initial result of the matching procedure is a string of letter classes. Letter classes are formed by breaking the alphabet up into groups of acoustically similar letters. The directory of names is also sorted by letter classes. After the input string is classified into letter classes, a second pass is performed to determine the optimally matching name. This system was tested on four talkers each of whom spoke a given set of 50 names. The names were spoken at both a deliberate and at a normal talking rate. Recognition was performed in both a speaker-trained and a speaker-independent manner. The directory consisted of about 18 000 names drawn from the Bell Laboratories directory. Recognition accuracies of 99% and 91% were achieved for speaker-dependent recognition using the deliberate talking rate and the normal talking rate, respectively. Recognition accuracies of 94% and 88% were achieved for speaker-independent recognition for the two talking rates.
Dichotic identification of complex sounds: Absolute and relative ear advantages
Authors: Lauter Judith L.
Published: October 2005

Dichotic identification of a variety of complex sounds was studied in seven listeners. Analysis of individual listeners’ scores shows that there are significant individual differences in terms of absolute ear advantage for a given sound, while comparison of such differences across stimuli reveals agreements among individuals as to relative ear advantages, when both magnitude and direction of ear difference are considered. This agreement can be expressed in terms of a ’’relative ear advantage continuum.’’ The experiments also indicated that ear advantages can show good reliability over as much as six months’ time.
Sound transmission loss of gypsum wallboard partitions. Report ♯2. Steel stud partitions having cavities filled with glass fiber batts
Authors: Green David W. , Sherry Cameron W.
Published: October 2005

Using the data bank of the acoustics laboratory of Domtar Research, statistical equations based on density are derived for predicting the sound transmission loss and sound transmission class of double leaf wall partitions. The partitions are constructed from gypsum wallboard, light gauge steel studs, and have glass fiber batts (R–7) in the cavity space. The results predicted, using these equations, are found to be in good agreement with results on similar assemblies tested at other laboratories. The equations are used to illustrate the effect of surface density, steel stud size, and method of board attachment on sound transmission loss. The effect of adding glass fiber batts (R–7) to the cavity space is shown to depend upon the surface density of the partitions. Assuming equal surface densities, no improvement in STC was noted for partitions having unbalanced construction. The results, predicted for simple partition construction, are compared to test data for partitions constructed using resilient channels and for multiple rows of steel studs.
Forward masking as a function of frequency, masker level, and signal delay
Authors: Jesteadt Walt , Bacon Sid P. , Lehman James R.
Published: October 2005

The forward masking of a sinusoidal signal by a sinusoid of the same frequency was investigated for frequencies ranging from 125 to 4000 Hz. Forward masking in dB is proportional to both masker level and log signal delay at each frequency. More forward masking occurs at very low frequencies than at high frequencies, given equal-sensation-level maskers, and masked thresholds are greater at low frequencies than at high frequencies given equal-SPL maskers. The data can be described equally well by assuming that the difference in forward masking as a function of frequency is due to a change in the time course of recovery from masking or to a change in the growth of masking at each signal delay. The frequency effect is not large enough to change the interpretation of forward-masking data in studies of suppression or psychophysical tuning curves.
The minimum detectable duration of auditory signals for normal and hearing-impaired listeners
Authors: Irwin R. J. , Purdy Suzanne C.
Published: October 2005

The minimum detectable duration of a brief burst of noise and a brief gap in a noise were measured by the two-alternative forced-choice method. For all listeners the minimum detectable duration of a burst was shorter than the minimum detectable duration of a gap at equal signal-to-noise ratios. For 12 listeners with normal hearing, the average minimum detectable duration of a burst with a 10-dB signal-to-noise ratio was 1.2 msec, whereas the average of a gap at the same signal-to-noise ratio was 4.2 msec. Nine of ten hearing-impaired listeners required longer durations, whether for bursts or gaps, than the average of normal listeners. These nine impaired listeners had slower time constants than any of the normal listeners. Both the rise and decay of auditory sensation in the impaired listeners were therefore abnormally slow.
Solution of an inverse, elastic-wave scattering problem
Authors: Baker George A.
Published: October 2005

A method is developed which in principle solves the inverse, elastic-wave scattering problem for scatterers of spherical symmetry which are described as a continuous variation of the material parameters of the isotropic, homogeneous, solid, host medium.
Propagation of spinning acoustic modes in partially choked converging ducts
Authors: Nayfeh A. H. , Kelly J. J. , Watson L. T.
Published: October 2005

A computer model based on the wave-envelope technique is used to study the propagation of spinning acoustic modes in converging hard-walled and lined circular ducts carrying near sonic mean flows. The results show that with increasing spinning mode number the intensification of the acoustic signal at the throat decreases for upstream propagation. The influence of the throat Mach number, frequency, boundary-layer thickness, and liner admittance on the propagation of spinning modes is considered.
Synthesis-based recognition of continuous speech
Authors: Paliwal K. K. , Rao P. V. S.
Published: October 2005

An acoustic phonemic recognition system for continuous speech is presented. The system utilizes both steady-state and transition segments of the speech signal to achieve recognition. The information contained in formant transitions is utilized by the system by using a synthesis-based recognition approach. It is shown that this improves the performance of the system considerably. Recognition of continuous speech is accomplished here in three stages: segmentation, steady-state recognition, and synthesis-based recognition. The system has been tried out on 40 test utterances, each 3–4 s in duration, spoken by a single male speaker and the following results are obtained: 5.4% missed segment error, 8.3% extra segment error, 52.3% correct recognition using only steady-state segments, and 62.0% correct recognition using both steady-state and transition segments.
Multiplexer using a Lamb wave transducer dependent on terminal condition
Authors: Toda Kohji
Published: October 2005

A new type of Lamb wave device with three transducers for multiplexing is described. The performance of a Lamb wave transducer, at the central part of the device, is strongly affected by the electrical termination. The transducer consists of three electrode groups, two electrodes of which are interdigital, having a phase difference of one-quarter wavelength of the Lamb wave. The use of diodes as voltage-controlled resistors for electrical termination makes it possible to realize a multiplexer. The device is operable for an amplitude-modulated input signal as well as a continuous wave input signal.
Some observations of echolocation clicks from free-swimming dolphins in a tank
Authors: Poché Lynn B. , Luker L. D. , Rogers P. H.
Published: October 2005

Echolocation signals have been observed from Atlantic bottlenose dolphins in a concrete tank lined with anechoic wood panels. These clicks have spectral peaks in the 100- to 130-kHz range, which is an uncommonly high-frequency range for echolocation in tanks. Similar signals were observed when the lining was removed from the tank. Ambient noise measured in the tank contained no appreciable energy in the 30- to 60-kHz band. Use of such high-frequency energy by dolphins for echolocation in tanks does not appear to be a consequence of either high noise level or reverberation environment.
Tactile communication of speech. I. Comparison of Tadoma and a frequency-amplitude spectral display in a consonant discrimination task
Authors: Snyder J. C. , Clements M. A. , Reed C. M. , Durlach N. I. , Braida L. D.
Published: October 2005

Consonant discrimination experiments were performed comparing Tadoma and an Optacon-based, frequency-amplitude, spectral display. The results of these experiments, which employed common subjects and procedures, indicate that Tadoma is substantially superior for discriminating consonant pairs that differ in voicing or place of articulation, but not for discriminating pairs that differ in manner of articulation. The overall superiority of Tadoma revealed in these consonant-discrimination experiments should not be generalized to all spectral displays.
On extending Biot’s theory of low-frequency acoustic scatter about a rough fluid–rigid interface to more general acoustic media
Authors: Menke William , Richards Paul G.
Published: October 2005

We extend Biot’s [J. Acoust. Soc. Am. 44, 1616–1622 (1968)] boundary conditions for multiple scatter at low frequencies to a medium consisting of a fluid wholespace containing a layer of spherical fluid inclusions. At low frequencies the layer of inclusions has a scattering effect equivalent to that of a set of linear boundary conditions acting on the center of the layer. These boundary conditions are of order kτ, where k is the wavenumber and τ is a measure of the size of the inclusions. The boundary conditions predict that a normally dispersed acoustic boundary wave can propagate along the plane of inclusions for specific acoustic contrasts between inclusions and wholespace. When the acoustic contrast is small the boundary wave exists only when the compressional velocity of the inclusions is slower than that of the wholespace. When the contrast is large, boundary waves exist on some layers of high-velocity inclusions as well.
Acoustic streaming reversal by a finite amplitude sound wave in a non-Newtonian fluid
Authors: Powell R. L.
Published: October 2005

Theoretical predictions are presented for the steady secondary flows (acoustic streaming) produced by the propagation of a finite amplitude planar acoustic wave in a non-Newtonian fluid. The constitutive equation governing finite amplitude acoustic wave propagation in quiescent non-Newtonian fluids is derived and consists of an integral expansion of the constitutive functional. Each successive term of the expansion is higher order in a small parameter related to the amplitude of the propagated wave. The linear term of the expansion governs infinitesimal wave propagation and the quadratic term governs nonlinear effects. These equations are used to study the acoustic streaming caused by the propagation of a finite amplitude planar acoustic wave in a channel which has a width greater than that of the acoustic wave. The results show that because of nonlinear viscoelastic effects, the direction of the streaming can be opposite to that found for Newtonian fluids.
Thermal hysteresis in acoustic resonators
Authors: Casperson Lee W. , Davis Lloyd M. , Harvey John D.
Published: October 2005

In some applications of piezoelectrically driven acoustic resonators, the power dissipated in the resonating material may be sufficient to significantly change the temperature and hence the resonance frequency. A straightforward analysis shows that this effect can lead to severe hysteresis and thermal bistability. This model is in agreement with experiments that have been performed using a fused silica acousto-optic modulator.
Measurement of vibrational relaxation time of oxygen between 475° and 675°K using an acoustic resonant technique
Authors: Feng I-an , Lee Mark C.
Published: October 2005

Vibrational relaxation times of O2–He, O2–CO2, and O2–H2 mixtures have been measured using a resonant chamber method between 475° and 675°K. This temperature range lies in the gap between the bulks of previous data obtained using acoustic and shock tube methods. Data analyses were carried out by a novel computer techique. Data for pure O2 were obtained by extrapolating that of mixtures to zero impurity concentrations. Our data agree with previous acoustic results at 473° and 573°K and shock tube results at 700°K. The temperature dependence of the vibrational relaxation time for pure O2 was compared to the theories of Landau and Teller [Physik. Z. Sowjetunion 10, 34 (1936)]; Schwartz et al. (SSH) [J. Chem. Phys. 20, 1591 (1952)]; and Parker [J. Chem. Phys. 34, 1763 (1961); 41, 1600 (1964)]. The simple Landau–Teller theory has shown better agreement with experimental data than that of SSH and Parker for the case of O2–O2, O2–He, and O2–H2 collisions.
Forward masking by enhanced components in harmonic complexes
Authors: Viemeister Neal F. , Bacon Sid P.
Published: October 2005

The audibility of a given target component in certain spectral complexes can be considerably increased by exposure to the complex with the target component deleted. This ’’enhancement effect’’ can be observed under a wide variety of conditions and presumably reflects frequency-specific adaptation: the frequency region around the target frequency is not adapted during the exposure and hence is relatively more sensitive. Data from the present study indicate that an enhanced component in a harmonic complex produces more forward masking of a sinusoidal probe than when that component is not enhanced, i.e., an enhanced component behaves as if it were physically more intense. This suggests that the adaptation process underlying the enhancement effect produces an increase in gain in the unadapted frequency region. This increase might result from a decrease, due to adaptation, of suppression of the unadapted region.
ORing loss data for square law detectors followed by an ORing device and an accumulator
Authors: Struzinski William A.
Published: October 2005

A mathematical model is developed to compute the ORing loss for square law detectors followed by an ORing device and an accumulator. The ORing loss is computed for a deterministic signal in Gaussian noise for a detection probability of 0.5 and false alarm probabilities of 10−2, 10−3, 10−4, and 10−6. The ORing loss is computed as a function of the number of channels ORed and the number of samples in the accumulator. It is concluded that the ORing loss increases with an increase in the false alarm probability and with an increase in the number of channels ORed.
Acoustic streaming in superfluid helium
Authors: Rooney J. A. , Smith C. W. , Carey R. F.
Published: October 2005

Quantitative measurements of acoustic streaming velocity in liquid helium as a function of sound intensity (up to the cavitation threshold), frequency (1, 3, and 10 MHz), and temperature (1.43 K?T?2.19 K) are reported. A transition to superfluid turbulence, several flow regions and flow fluctuations are observed. Comparison with the predictions of the second-order Khalatnikov two- fluid hydrodynamic equations indicates good functional and quantitative agreement.
A technique for detecting the ipsilateral acoustic reflex
Authors: Margolis Robert H. , Wilson Richard H. , Van Camp Karel J.
Published: October 2005

A technique was explored for detecting the ipsilateral acoustic reflex using one acoustic signal (226-Hz tone) both to elicit the reflex and to measure the impedance of the ear. By eliminating the presentation of two acoustic signals to the same ear, artifactual responses that result from interactions between two signals are avoided. The method provided reflex threshold estimates for five normal subjects that averaged 99.8 dB SPL, in close agreement with previously reported data. A sixth subject, with otosclerosis, showed no evidence of a reflex. With some refinement, the method could become a quick, reliable measurement procedure that avoids some of the problems of conventional methods.
Density of myelinated nerve fibers in the chinchilla cochlea
Authors: Bohne Barbara A. , Kenworthy April , Carr Charles D.
Published: October 2005

Baseline values for the density of myelinated nerve fibers at 11 locations in the chinchilla cochlea were obtained as a prerequisite for studying the relationship between sensory cell degeneration and spiral ganglion cell loss. Myelinated nerve fibers were counted within the osseous spiral lamina near the habenulae perforata. The data were expressed as myelinated nerve fibers per inner hair cell (MNF/IHC). Since the vast majority of the afferent fibers innervate the inner hair cells and since the percentage of myelinated efferent fibers at the level of the osseous spiral lamina is estimated to be quite small, MNF/IHC is a useful value which will permit the comparison of data from normal and damaged specimens. An average density of 9.4 MNF/IHC was found at the apex. This rose to a peak of 18.8 MNF/IHC in the first turn and then decreased to 14.2 MNF/ IHC in the round window region. The standard deviations at the different locations ranged from 0.8 to 1.5 MNF/IHC.
Array beam response in the presence of amplitude and phase fluctuations
Authors: Quazi Azizul H.
Published: October 2005

This paper is a study of the influences of random fluctuations of phase and weighting factors (or errors in these parameters), and element failures on beam gain, main beamwidth, and directional accuracy of main beam axis and side-lobe level. It summarizes results of investigations into the influences of random errors on beam-response-related parameters. We shall present design guidelines for rectangular planar array (composed of M N-element linear arrays) subject to random phase and weighting errors, and element failures. We shall also discuss what precautions are necessary in designing to achieve a specific beam-forming performance, which deals with beam gain, beamwidth, beam direction and average and peak side-lobe levels. The analytical results is compared to computer simulated beamforming performance whenever possible for the purpose of validation.
Measurement of acoustic intensity in the presence of one-dimensional fluid flow
Authors: Comparin Robert J. , Rapp John R. , Singh Rajendra
Published: October 2005

This paper presents the results of an analytical and experimental investigation of the measurement of acoustic intensity in the presence of mean fluid flow. The investigation was necessitated by the fact that an acoustic intensity measurement technique with mean fluid flow is not available. Munro and Ingard [J. Acoust. Soc. Am. 65, 1402–1406 (1979)] have developed a formulation for this problem; but no experimental data or verification is given. In this paper, two independent formulations for acoustic intensity in a duct with mean fluid flow using the two-microphone cross-spectral density method are developed. In order to evaluate and compare our formulations with the Munro and Ingard expression, we have conducted an experiment for the case of one-dimensional, irrotational, isentropic mean flow in a duct over 0–0.15 Mach range and for frequencies from 300 to 800 Hz. All these formulations yield similar values for acoustic intensity, within experimental errors. Although it is still premature to draw definite conclusions regarding the significance of additive terms to the nonflow acoustic intensity, some insight based on our preliminary experimental results has been gained.
Correlation of the effects of grazing flow on the impedance of Helmholtz resonators
Authors: Walker B. E. , Charwat A. F.
Published: October 2005

Measurements of the acoustic impedance of a two-dimensinal Helmholtz resonator, i.e., a cavity coupled to the environment through a high-aspect ratio slot are presented as a function of the velocty of a steady flow above the orifice of the resonator. The structure of the unsteady flow above the orifice is outlined from hot-wire measurements. A simplified model of it is proposed and analyzed, leading to a successful correlation of both the resistance and the reactance of the resonator.
Backscattering of acoustic waves by randomly rough surfaces of elastic solids immersed in water
Authors: de Billy M. , Quentin G.
Published: October 2005

In this paper we study the angular variations of the mean total intensity of ultrasonic waves backscattered by randomly rough surfaces of elastic solids immersed in water. The potential method constitutes the starting point of the theoretical approach. The calculations have been done for a normal distribution of heights and a Gaussian autocorrelation function. The roughness of the samples varies from 8 to 110  μm. The experiments have been done at discrete frequencies up to 10 MHz such that the roughness parameter g( = k21h2γ2) has values ranging from 10−2 to 90. A comparison of the experimental curves and theoretical calculations shows good agreement for incident angles of 40° or less. Another significant feature of this experiment is the increase of the backscattered intensity at the Rayleigh angle for k1 h<1.
Resonance frequency shift of an acoustic chamber containing a rigid sphere
Authors: Leung E. , Lee C. P. , Jacobi N. , Wang T. G.
Published: October 2005

The resonance frequency shift of an acoustic rectangular chamber due to the presence of a rigid sphere has been measured for l = 1,2 modes as a function of sphere size and position. The frequency shift is the results of volume exclusion and wave scattering. An analytical Green’s function calculation was used to explain the data, providing excellent agreement between the measured and the calculated values. Also reported are similar measurements for a thin disk and the ratio of second harmonic to fundamental pressure as a function of sphere position. The measurement shows that the sphere reduces the first harmonic content, with sharply peaked suppression minima at specific sphere positions.
Rare-earth iron ’’square ring’’ dipole transducer
Authors: Cohick Susan M. , Butler John L.
Published: October 2005

A rare-earth iron magnetostrictive transducer in the form of a ’’square ring’’ has been constructed to operate in a dipole mode as well as in an omni mode. The outer diameter of the transducer is 6.5 in. (0.1651 m) and it resonates at 2.0 kHz in the omni mode and 2.4 kHz in the dipole mode.
Acoustic features of infant vocalic utterances at 3, 6, and 9 months
Authors: Kent Raymond D. , Murray Ann D.
Published: October 2005

Recordings were obtained of the comfort-state vocalizations of infants at 3, 6, and 9 months of age during a session of play and vocal interaction with the infant’s mother and the experimenter. Acoustic analysis, primarily spectrography, was used to determine utterance durations, formant frequencies of vocalic utterances, patterns of f0 frequency change during vocalizations, variations in source excitation of the vocal tract, and general properties of the utterances. Most utterances had durations of less than 400 ms although occasional sounds lasted 2 s or more. An increase in the ranges of both the F1 and F2 frequencies was observed across both periods of age increase, but the center of the F1–F2 plot for the group vowels appeared to change very little. Phonatory characteristics were at least generally compatible with published descriptions of infant cry. The f0 frequency averaged 445 Hz for 3-month-olds, 450 Hz for 6-month-olds, and 415 Hz for 9-month-olds. As has been previously reported for infant cry, the vocalizations frequently were associated with tremor (vibrato), harmonic doubling, abrupt f0 shift, vocal fry (or roll), and noise segments. Thus, from a strictly acoustic perspective, early cry and the later vocalizations of cooing and babbling appear to be vocal performances in continuity. Implications of the acoustic analyses are discussed for phonetic development and speech acquisition.
Vibrations of cross-shaped, I-shaped, and L-shaped membranes and plates
Authors: Irie Toshihiro , Yamada Gen , Ashida Kengo
Published: October 2005

The natural frequencies (the eigenvalues of vibration) and the mode shapes are presented for cross-shaped, I-shaped, and L-shaped membranes and simply supported plates. An irregularly shaped membrane is formed on a rectangular base membrane by fixing several segments. The reaction forces acting on the edges of an actual membrane are expanded into Fourier series with unknown coefficients, and homogeneous equations for the coefficients are derived by the restraint conditions on the edges. The natural frequencies and the mode shapes of the actual membrane are determined by calculating the eigenvalues and eigenvectors of the equations. The numerical values obtained for membranes can be immediately converted into those of simply supported plates by the dynamical analogy between membrane and plate.
Distinctions between boundary and distributed damping in a waveguide with a cutoff frequency
Authors: Smith P. W.
Published: October 2005

The precise, closed-form solution for response of a finite one-dimensional waveguide with cutoff (string on an elastic foundation) is examined for cases where damping is either uniformly distributed or concentrated in the ends. No marked spatial concentration of response at the driven point is found unless the damping is distributed and also the wave attenuation in one round trip through the system is large. Increased dispersion, as frequency approaches the cutoff, increases the round-trip attenuation caused by distributed viscous damping, but it decreases the attenuation caused by boundary damping (at the ends of the waveguide).
Acoustic radiation from fluid-loaded elastic plates. II. Symmetric modes
Authors: Woolley Barry Lee
Published: October 2005

A mathematical method for extending equations of motion to include higher order symmetric modes is presented and discussed. This method is illustrated by the development of equations of motion for the first two and the first three symmetric modes of plate vibration. The form of the Lyamshev plate equation of motion is used as a starting point for the development of the new equations. Transmission through an infinite elastic plate is calculated for developed plate equations of motion incorporating four antisymmetric and three symmetric modes of plate vibration.
Parametric acoustic source with an endfire primary projector
Authors: Moffett Mark B. , Konrad William L.
Published: October 2005

A new type of parametric acoustic source configuration utilizes an endfire projector for the primary beam. This configuration shows promise for those applications requiring a projector having small frontal area, e.g., a source to be towed. A small endfire projector consisting of 20 half-wavelength elements at 30 kHz in line with 20 half-wavelength elements at 35 kHz was built and tested at NUSC’s Dodge Pond and Seneca Lake test facilities. Difference-frequency data at 5 kHz, as well as 3 and 7 kHz, are presented. Although the source levels are in agreement with the theory, the measured beams are narrower than predicted, even though accounting is made for the nonideal nature of the primary beams. This discrepancy could be due to a primary-beam phase effect. An aperture factor for endfire projectors is calculated.
Acoustic surface wave pulses and the ringing of resonances
Authors: Überall H. , Gaunaurd G. C. , Murphy J. Diarmuid
Published: October 2005

The resonance scattering theory, developed by us earlier, furnishes poles of the scattering amplitude of acoustic or other types of waves in the complex frequency plane which have been explained in terms of resonances of circumferential waves. Analogous poles in electromagnetic scattering theory were analyzed by the ’’Singularity Expansion Method’’ (SEM). It is shown here for the case of sound scattering from an impenetrable sphere that the residue sum over an appropriate subset of the complex-frequency poles will lead to the synthesis of a given, repeatedly circumnavigating individual circumferential wave (or pulse).
Scattering of two-dimensional elastodynamic waves by a rigid plane strip or a plane crack of finite width: The transition matrix
Authors: van den Berg Peter M.
Published: October 2005

The diffraction of time-harmonic, vertically polarized, elastic waves by a two-dimensional plane obstacle is investigated theoretically. The plane rigid strip and the plane crack of finite width are considered in detail. For these particular obstacles the transition matrix has been obtained using a boundary-integral-equation technique. It is shown that some symmetry considerations lead to a separation of the even and odd parts of the fields. Taking complete sequences of Chebyshev polynomials, an expansion of the fundamental unknown quantities at the obstacle has been obtained in such a way that each member of the expansion satisfies the elastodynamic conditions at the edges of the obstacle. This choice of the expansion functions then leads to a rather simple form of the transition matrix. In the derivation of the transition matrix we avoid the evaluation of singular integrals for the so-called Q-matrix elements.
Nearfield of a large acoustic transducer, Part I. Linear radiation
Authors: Garrett Greer S. , Tjo/tta Jacqueline Naze , Tjo/tta Sigve
Published: October 2005

Results are reported of an investigation of the nearfield of a large circular transducer (182-cm diameter, and composed of 364 smaller elements operating in water at 11–16 kHz, and with parametric generated difference frequencies in the range 0.5–5 kHz). Linear radiation is considered in this paper (Part I), whereas parametric radiation is discussed in a related paper (Part II). Amplitude and phase are measured at various distances and compared with calculations based on a simplified integral representation of the field obtained by Naze Tjo/tta and Tjo/tta [J. Acoust. Soc. Am. 68, 334–339 (1980)], as a solution of the parabolic approximation of the Helmholtz equation. Comparison is also made with an exact on-axis calculation. The main results are (1) the transducer radiates as a piston with a uniform velocity distribution, (2) the integral solution represents an adequate description of the observed sound field. It provides a simple method to obtain general properties of the field as well as numerical results by computing a simple (line) integral. (3) Within the same approximation scheme, formulas are presented for the case of axial symmetry, from which the field of an amplitude or phase shaded source can be calculated from a simple (line) integral. (4) From this, it is further shown how the farfield (amplitude and phase) can be calculated readily from the nearfield measurements.
Segmental durations in connected speech signals: Preliminary results
Authors: Crystal Thomas H. , House Arthur S.
Published: October 2005

The data base, methods for a study of the durations of phonetic units in connected speech, and some preliminary results are described. From readings of two scripts by many talkers, two sets of seven talkers each were selected, based on total reading time, to form a fast group and a slow group of talkers. Using computer graphics and digital playback procedures, the recordings were segmented into breath groups and pauses, and the first four sentences in each script were segmented into phones. The hold and release (that is, plosion and/or frication) portions of stops were identified and measured; less than 50% of the stops included releases. To establish the usefulness of the data base, the first-order statistics of the phonetic segments were determined, and a variety of durational characteristics were compared to existing reports. Analysis of number of breath groups, phonation time, and pause characterized the difference between so-called average fast and average slow talkers; however, no script-independent measure of these variables was found which would accurately predict the classification of individual talkers. The mean durations of various phonetic categories showed essentially the same percentage change when the fast and slow talkers were compared. Preliminary analyses of contextual influences on durations showed some expected changes, and also indicated that certain traditional predictions may not hold for informal connected speech. Gamma functions were fitted to the distributions of durations of various gross categories.
A method for reducing multipath artifacts in ultrasonic computed tomography
Authors: Meyer C. R. , Chenevert T. L. , Carson P. L.
Published: October 2005

Estimates of ultrasonic attenuation based on first-order or moment spectral estimators are often confused by multipath propagation effects. The magnitude of error in attenuation estimates due to multipath for the frequency shift technique is described. A parametric model of multipath propagation effects on the frequency spectrum is introduced and an optimization technique is used to estimate the coefficients of the model. The attenuation estimation performances of the model estimation technique, the frequency shift technique, and a cepstral liftering technique are compared.
Dynamic stability of orthotropic annular plates under pulsating radial loads
Authors: Tani J. , Doki H.
Published: October 2005

The effect of the polar orthotropic material property on the parametric resonance of clamped annular plates is investigated theoretically. The pulsating radial forces with the same period act along both the inner and outer edges of the plate. The problem is reduced to that of a finite degree-of-freedom system with the Galerkin procedure, the stability of which is examined by using Hsu’s method [J. Appl. Mech. 30, 367–371 (1963)]. The instability regions of both principal and combination resonances are determined for a wide range of exciting frequencies with the effect of the static uniform compression taken into consideration. It is found, among others, that the wavenumber dependence of the dynamic stability is changed remarkably by the variation in the polar orthotropic material property.
Forward masking of diotic and dichotic clicks by noise
Authors: Hanna Thomas E. , Robinson Donald E. , Shiffrin Richard M. , Gilkey Robert H.
Published: October 2005

The first experiment reported here measured thresholds for clicks in forward masking as a function of the masker level and as a function of the temporal relation of a 6-kHz low-pass noise masker to the click (300-msec duration with a 20-msec temporal gap or 10-msec duration with a 5-msec gap). Also varied were the spectral content of the click (low-pass filtered at 1 or 5 kHz) and the interaural phase of the click (0 or π). The difference in frequency content had no effect on the amount of masking for the 300-msec masker, while with the 10-msec masker greater masking was found for the 1–kHz click. This combination (1 kHz, 10 msec) was also the only one to produce Masking Level Differences (MLDs) when the click was presented dichotically. A second experiment investigated the effects of combining the maskers used in the first experiment. Additional masking (above that predicted by an energy sum) was found, as has been reported elsewhere [Penner and Shiffrin, J. Acoust. Soc. Am. 67, 617–627 (1980)]. However, the magnitude of this additional masking was decreased for certain conditions. These data conflict with the predictions of additivity of masking obtained from a model proposed by Penner and Shiffrin and suggest that modifications to that model are needed. The results of both experiments can be explained by assuming that two processes are acting in forward masking [Duifhuis, J. Acoust. Soc. Am. 54, 1471–1488 (1973)].
Formulation of the maximum signal-to-noise ratio array processor in beam space
Authors: Gray D. A.
Published: October 2005

The maximum signal-to-noise ratio (SNR) processor as formulated by Edelblute et al. [J. Acoust. Soc. Am. 41, 199–206 (1967)] has proved extremely useful in the analysis and interpretation of sonar data. In a known noise field this processor uses an optimum set of weights (or shading coefficients) derived from the crosspower spectral matrix of receiver noise outputs. In this paper an alternative maximum SNR processor is derived. This processor transforms the outputs of a conventional frequency domain beamformer in such a way that the SNR in the transformed beam is maximized. Expressions for the transformation (i.e., the complex beam weights) and the resulting array gain are derived. Some general properties of the beam space formulation are discussed and conditions for its equivalence to the element space formulation of Edelblute et al. are determined. Examples using both simulated and sonar data are given to compare the beam and element space formulations.
Attenuation and dispersion effects of nonequilibrium molecular processes on acoustic waves in cylindrical tube
Authors: Peng William W.
Published: October 2005

Attenuation and dispersion effects of nonequilibrium molecular processes on acoustic waves in a cylindrical tube are studied. Both internal energy transfer and molecular transport processes are included in the linearized gasdynamic equations and the rate equations for two vibrational modes of energy. A finite Hankel transform technique is employed to solve the system of partial differential equations. General expressions for attenuation factor and wavenumber are given in closed form for the case of high Reynolds number. The limiting cases of molecular equilibrium and infinite Reynolds number are also obtained and compared with results from previous investigations. Applications of the theory to CO-N2 mixtures at both room and high temperatures are given and compared with the simplified formulas.
Sound velocity and related properties of marine sediments
Authors: Hamilton Edwin L. , Bachman Richard T.
Published: October 2005

New laboratory measurements of sediment properties in cores from the Bering Sea, North Sea, Mediterranean Sea, equatorial Pacific, and other areas, have been combined with older measurements and the results, with statistical analyses, are presented (for various sediment types in three general environments) in tables, diagrams, and regression equations. The measured properties are sound velocity, density, porosity, grain density, and grain size; computed properties are velocity ratios (sediment velocity/water velocity) and impedance. Mineral-grain microstructures of sediments are critical in determining density, porosity, and sound velocity; compressibility of pore water is the critical factor in determining sound velocity. New regression equations are provided for important empirical relationships between properties. Corrections of laboratory values to sea-floor values are discussed. It is concluded that sound velocity and density are about the same for a given sediment type in the same environment in any ocean if porosity is about the same. Given the mean size of mineral grains, or average porosity, of a sediment, the average sound velocity can be predicted within 1% or 2% in most environments. Comparisons with recent in situ measurements validate the laboratory measurements.
Scattering by slender bodies of revolution
Authors: Junger M. C.
Published: October 2005

The pressure scattered by slender bodies of revolution irradiated by a plane wave at ‘‘beam aspect’’ is formulated in a manner which relaxes the assumptions underlying the Kirchhoff analysis. While the latter stipulates that area elements scatter as though located in planar baffles, the present theory assumes that the baffles are cylindrical, i.e., that one rather than two radii of curvature is infinite. The theory gives good results in the resonance and Rayleigh regions as well as in the short-wavelength limit even for bodies whose aspect ratio is only two.
High-resolution imaging for systems with small apertures
Authors: Lee Hua , Wade Glen
Published: October 2005

The resolution of an imaging system is usually limited by the size of the receiving aperture. Here, we introduce a method that achieves high resolution for systems with small apertures and rejects ghost images caused by object elements outside the region of interest. The method utilizes a set of orthogonal basis functions to perform accurate pattern recognition. The orthogonal basis functions are generated from the received patterns corresponding to point objects at various target positions by using the Gram-Schmidt orthogonalization algorithm. This method can be applied to general imaging systems for resolution improvement as long as they are linear.
Clipping degradation in a system used to detect time-periodic variance fluctuations
Authors: Hurd H. L.
Published: October 2005

Studies of the effects of nonlinear distortion have typically determined certain properties of the process, y(t)=f[x(t)], where f(⋅) is some nonlinear transfer function under consideration. The property commonly sought is its associated spectral density function or, equivalently, its correlation function. In this paper a particular type of degradation from nonlinear distortion is considered; x(t) is assumed equal to s(t)+n(t), where n(t) is wide-sense stationary and s(t) is a nonstationary process, independent of n(t), with zero mean and periodically fluctuating variance. It is found that the performance is not degraded when limiting is slight, but severe limiting tends to prevent detection of the variance fluctuations.
Acoustical spectroscopy of violins
Authors: Arnold Eric B. , Weinreich Gabriel
Published: October 2005

The normal modes of the violin system are investigated by studying its response to external excitation by an incident sinusoidal sound wave of variable frequency. Appropriate transducers are used to sense the vibration of wood, air, and strings. The data are analyzed by computer to yield information on the complex eigenfrequencies and eigenfunctions of the various normal modes. Methods of minimizing errors due to resonances outside the frequency window are discussed. Some representative results are shown.