bluuebunny/crossref_metadata_2025 huggingface dataset:
Sediment contributions to group velocity in shallow water
Authors: Oakley David W. , Koch Robert A.
Published: January 2006

Dispersion curves are used to examine the effect of sediments on group velocity, and the problem further dissected by a direct look at the relative contributions of the sediment layers to the group velocity integral. The environments of interest have water depths less that 150 m and sediment thickness of the order of 50 m. The range of frequencies considered is between 25 and 600 Hz. A systematic variation of sediment types and velocity profiles will be examined to find features of the dispersion curves which might be used to extract information about the bottom from shot data. In the presence of stable water velocity profiles, gradients in the sound velocity in the sediment can be detected, as can layering, provided such layers are near the water-sediment interface. Highly variable water sound velocity profiles limit information available concerning the sediment to gross features such as sediment type. [Work supported by Naval Ocean Research and Development Activity.]
Estimated spatial coherence from a layered ocean bottom
Authors: Tunnell T. W.
Published: January 2006

In this modeling study subsurface layering effects on the spatial coherence of bottom-interacting sound were investigated. The ocean bottom was modeled as alternating layers of clay and clayey silt. A silty clay bottom was used as a control. Complex reflection coefficients were calculated using a plane-wave multilayer model [G. J. Fryer, J. Acoust. Soc. Am. 63, 35–42 (1978)]. Using a frequency averaging technique, estimates of the spatial coherence were obtained as a function of grazing angle for fixed sensor separation. The results indicated that subsurface layering can seriously degrade the spatial coherence at frequencies above 100–200 Hz. The spatial coherence is considerably less affected by subsurface layering at very shallow grazing angles (10° or less) or very steep grazing angles (75° or greater). [Work supported by NORDA.]
Acoustic exploration of ocean floor properties based on the ringing of sediment layer resonances
Authors: Nagl Anton , Überall Herbert , Yoo Kwang-Bock
Published: January 2006

It has recently been demonstrated [A. Nagl, H. Überall, and W. R. Hoover, IEEE Trans. Geosci. Electron. GE-20, 332 (1982)] that the physical properties of a layered ocean floor may in principle be determined from an analysis of the resonances in frequency, or in angle of incidence, which appear in bottom-reflected acoustic signals. Here, we study the possibility of probing the characteristics of isolated resonances by employing sinusoidal pulse trains of sufficient duration; this contrasts with conventional techniques based on the travel times of short pulses, where many resonances contribute simultaneously to the reflected amplitude. It is found that the resonances manifest themselves by a ringing of the signal, and by a characteristic interference between the specular component and the fields resulting from multiple reflections within a layer. [Supported by the Office of Naval Research and by the College of Marine Studies, University of Delaware, where part of this work was carried out].
Sound generation by a moving laser source
Authors: Berthelot Yves H. , Chotiros Nicholas P.
Published: January 2006

A theoretical and experimental study of moving thermoacoustic sources is presented in this paper. The inhomogeneous linear wave equation for a fluid containing heat sources [P. J. Westervelt and R. S. Larson, J. Acoust. Soc. Am. 54, 121–122 (1973)] is used to derive the acoustic response h(t) of a medium excited by an impulse of light. The pressure radiated by a laser source moving at constant speed over a water surface is then described in terms of a convolution between the impulse response h(t) and the optoacoustic source strength which is proportional to dI/dt, where I(t) represents the laser intensity. In some limiting cases of farfield radiation, the computed pressure waveforms can be compared with previous work [L. M. Lyamshev and L. V. Sedov, Sov. Phys. Acoust. 27(1), 4–18 (1981).] An experimental study is also in progress. The motion of the laser beam over the water surface at velocities up to Mach 2 is achieved by means of a rotating mirror. The laser is excited in the conventional non-Q-switched mode, with a pulse duration of 1 ms. [Work supported by ONR.]
Recognition of famous voices given excerpted vowels, words, and 2-s texts
Authors: Emmorey Karen , Van Lancker Diana , Kreiman Jody
Published: January 2006

The ability of 40 subjects to recognize 25 famous male voices was investigated. Samples were tape-recorded and edited on a PDP-11/34 computer. Three different listening tasks were prepared. Subjects indicated whether they recognized voices given six choices: (1) from 2-s samples; (2) from excerpted words (mean duration 481 ms; and (3) from excerpted and concatenated strings of vowels (mean duration 494 ms). The same voices were used in all tasks. Subjects were divided into two groups. For one group, the tasks were presented in the order 2-s texts, words, vowels. For group two, the reverse order was presented. A two-way ANOVA revealed no effect of presentation order. Subjects correctly identified 61% of the voices they knew (ascertained by a questionnaire) given 2-s texts, 40% of the voices given excerpted words, and 34% given vowel strings. Subjects performed significantly better on the 2-s task than on the word or vowels tasks. There was no significant difference between their performance on the word and vowels conditions. These results show that voices can be recognized given limited amounts of voice information. [Work supported by NIH Grant No. 4-443944-31117.]
A model for the synthesis of natural sounding vowels
Authors: Allen Donald R. , Strong William J.
Published: January 2006

A model has been developed which is designed to preserve some of the naturalness that is usually lost in speech synthesis. A parameterized function is used to produce an approximation to the cross-sectional area through the glottis. A circuit model of the subglottal and glottal system is used to generate the volume velocity of the air through the glottis from the lung pressure and the time-varying supraglottal pressure. The tract is represented by it input impedance impulse response which can be calculated from the area function of the tract. A convolution of the input impedance impulse response with the volume velocity determines the supraglottal pressure. The equations relating the above two onditions for the volume velocity are solved simultaneously. The output of the model is generated by convolving the resulting glottal volume velocity with the transfer function impulse response of the tract. A comparison is made between vowels synthesized with and without the vocal tract glottal flow interaction. Listening tests showed that those vowles with the interaction were preferred as more natural sounding over those without the interaction.
Pitch encoding using simple unit pitch patterns
Authors: Goudie Kathleen M. , Lin Kun-Shan , Frantz Gene A.
Published: January 2006

In encoding synthetic speech for vocabulary storage and reproduction, current techniques require storing at least five or six bits of coded pitch value per frame. Due to the slow variation of pitch contours, it is possible to describe these contours as a sequence of simple pitch patterns. If each pattern in the sequence is applied to a subunit of the coded phrase or word, each subcontour can furthermore be approximated in terms of simple linear functions. The pitch pattern is selected by picking the best match between the target or natural subcontour and one contour from a library of predefined simple pitch contours. By storing one pitch pattern contour per specific subunit in speech, a considerable savings in vocabulary storage may be achieved. Informal listening tests show that the degradation in speech quality is minor.
Periodic repetition of multi-pulse excitation
Authors: Atal Bishnu S. , Caspers Barbara E.
Published: January 2006

B. S. Atal and J. R. Remde (Proc. ICASSP 82) described a method for determining the multipulse excitation for LPC speech synthesis. We find that, even for reasonably periodic speech waveforms, the secondary pulses in the multipulse excitation do not show similar periodic behavior. What is the influence of this lack of periodicity in the excitation on the quality of synthetic speech? We have investigated this question by introducing controlled periodicity into the multipulse excitation. The excitation was first segmented into individual pitch periods. For every sequence of n pitch periods, the multipulse pattern from the pitch period in the middle of each sequence was then used to repeat the excitation pattern in the other n − 1 surrounding pitch periods. In this process, the overall amplitude envelope of the utterance was left unchanged. We find that as many as 15 periods may be repeated without introducing significant audible distortion in the synthetic speech signal. However, repetition of a single multipulse pattern across all voiced segments of an utterance produced noticeable coloration in synthetic speech. We will discuss further implications of these results in this paper.
The lids of pianos and harpsichords as acoustic transformers
Authors: Corliss Edith L. R. , Corliss Charles H.
Published: January 2006

The lid of a grand piano may be closed altogether on the case, removed, or raised to a fixed position by a stick. Many larger instruments are equipped with a short stick as an alternative to the long stick. Raising the lid to these alternative positions changes the tone color to an extent perceptible to the player and the audience. This effect is measured more readily with a harpsichord because the plucking action is essentially independent of the player's touch. Using a harpsichord built by C. Randall Taylor in 1966, the authors have investigated the effect of adjusting the lid to a number of positions. The change produces measurable alterations in the output. The effect is similar to horn loading on a loudspeaker, and will be discussed from this standpoint.
Responses of gray whales (Eschrichtius robustus) to nonbiological noise
Authors: Dahlheim Marilyn E. , Fisher H. Dean
Published: January 2006

In order to focus on the problem of increasing nonbiological noise in the environment of the gray whale (Eschrichtius robustus) and to answer the question as to how this species uses its acoustic signaling most efficiently, a study was undertaken at Laguna San Ignacio, Baja California Sur, Mexico, in February 1983 to determine the responses of gray whales to projected sound sources. A series of underwater “playback” experiments were conducted. The playback included the projection of nonbiological as well as biological sound sources. The acoustical and behavioral responses of the whales were recorded during pretrial, trial, and post-trial playback periods. Sounds were projected back only during the “trial” periods. With the onset of increased levels of man-made noise, the gray whale's acoustical activities increased, as did the source levels of their calls. Observations on the behavioral activities of these whales in response to increased noise resulted in (1) prolonged dive times and (2) direct movements on the part of the whales away from the transducers. The acoustical and visual responses of the whales appear to differ depending upon the sound stimuli being presented.
Acoustic properties of porous media
Authors: Johnson David Linton , Plona Thomas J.
Published: January 2006

The long-wavelength acoustic properties of two-component composites is reviewed and it is shown that in order for such a system to have two distinct longitudinal modes, one component must be a fluid, the other a solid, and each must form its own percolating cluster. The Biot theory, which treats the two displacements on a separate and equal footing, is shown to give an excellent description of a wide variety of such systems which include: the diffusive mode in polymer gels, 4th sound in superfluid/superleak systems, the diffusion of a fluid pressure pulse through a porous solid, and the additional “Slow Wave” recently observed in a variety of water-saturated porous materials. It is shown how one can independently measure all the necessary input parameters and successfully calculate the effect of fluid saturation on the measured speeds. The essential connection between the acoustic properties and the electrical properties of porous solids is made. Finally, it is shown that, in general, standard multiple scattering theories within the single site approximation are intrinsically incapable of giving even a qualitative description of the acoustic properties of such bipercolating systems; the exception is when one component does not percolate as occurs, for example, in a suspension.
Marine sediment acoustics
Authors: Stoll Robert D.
Published: January 2006

The prediction of velocity and attentuation in acoustic waves which propagate through marine sediments is of key importance in many surveillance and exploration techniques. A mathematical model of the sediment must reflect the influence of such parameters as porosity, overburden stress, particle size, and lithification. The general theory of Biot has been used to construct a model which has been successful in estimating propagation characteristics in a wide variety of sediments. Two kinds of viscous damping are included in the model. One deals with the overall motion of the interconnected fluid field with respect to the skeletal frame. The other accounts for local fluid motion near the grain contacts which produces a viscoelastic response similar to the “squeeze film” phenomenon in lubrication theory. Recent experimental data for sandstone, sand, silt, and other sediments show that the various forms of viscous damping produce a frequency dependent Q in virtually all water-saturated sediments. New data are presented for sand and silt in the frequency range of 2–1500 Hz which demonstrates the effects of both kinds of viscous damping. [Work supported by ONR.]
Internal friction and modulus dispersion in fluid saturated porous rock
Authors: Tittman B. R. , Bulau J. R. , Abdel-Gawad M.
Published: January 2006

In the exploration for gas and oil, the interpretation of seismic/acoustic well logging data requires an understanding of the interaction between acoustic waves and rock under in-situ conditions, i.e., combined effects of pressure, temperature, and pore fluid. Our recent lab studies have revealed a significant internal friction peak and an associated modulus dispersion in coconino sandstone when the frequency (88–550 Hz) and/or fluid viscosity (0.0025–13.5 poise) is varied at elevated effective pressures to 3.4 × 107 Pa. The results are consistent with a linear relaxation mechanism involving the flow of a ruscous intergranular fluid with a characteristic time proportioned to fluid viscosity. The liquid “squirt”-type model of O'Connell and Budiansky (1977) predicts a relaxation peak at the value of frequency-viscosity observed in this study. The presentation will discuss the experimental approach, the data, their interpretation, and their application to exploration seismology. [Work supported by Consortium of Petroleum Companies.]
Grain contacts and viscous relaxation
Authors: Murphy William F. , Winkler Kenneth W. , Kleinberg Robert L.
Published: January 2006

A micromechanical model is developed for acoustic attenuation and dispersion in sedimentary materials such as sandstones. The theory decribes the response of two grains in contact to small sinusoidal loadings. Surface energy and fluid saturation are included explicitly. Grain surfaces are microscopically rough and irregular. We postulate that contact between grains forms numerous small solid-solid contacts and that narrow interconnected gaps remain between the surfaces. As the grains oscillate, liquid must be squeezed out of and sucked back into the gaps. The contact relaxation under normal force is hydrodynamic. The theory offers a unified explanation of several heretofore apparently unrelated experimental observations. The resulting equations predict the stiffness and loss as a function of frequency, effective pressure, fluid adsorption, saturation, viscosity, and temperature. Insofar as the micromechanical predictions relate to continuum acoustic properties, the agreement with observation is excellent.
Effects of pressure and fluid saturant on ultrasonic scattering in glass beads
Authors: Winklet Kenneth W. , Murphy William F.
Published: January 2006

Compressional wave phase velocity and attenuation have been measured in packings of unconsolidated glass beads as functions of external confining pressure. Samples were studied when vacuum dry and when saturated with different pore fluids. Pressure/pore fluid combinations were chosen to minimize nonscattering loss mechanisms. Phase velocity exhibits negative velocity dispersion and attenuation is proportional to the fourth power of frequency. Increasing confining pressure (to 15 MPa) significantly reduces the scattering losses (by an order of magnitude at a given frequency in dry glass beads). Decreasing pore fluid compressibility produces a corresponding decrease in the scattering losses. This work shows that theoretical models based on suspensions are not adequate when the grains are interacting to form a solid frame. The present data, along with previous data for fused glass beads, suggest that the scattering strength is related to the contrast between the acoustic properties of the composite and of the grains.
Grain shape and sorting effects on shear wave attenuation in unconsolidated laboratory sediments
Authors: Brunson Burlie A.
Published: January 2006

Shear wave attenuation measurements were made using ceramic bimorph transducers to excite transverse vibrations in a cylindrical column of unconsolidated sediment. Three different water-saturated sediments were used in an attempt to determine the effects of grain shape and sorting on the frequency dependence of attenuation. The mean grain size of the sediments was held constant while the grain shape and size distributions were varied. The sediment assemblages used in the attenuation measurements included a moderately sorted angular quartz sand, a well-sorted angular quartz sand, and well-sorted spherical glass beads. The moderately sorted sand showed the greatest attenuation over the measurement frequency range of 1–20 kHz. The well-sorted sand and the glass beads showed generally lower attenuation with the beads being the least lossy propagation medium. All three sediments showed evidence of viscous attenuation due to fluid-to-grain relative motion. This mechanism leads to a nonlinear relationship between attenuation and frequency. [Work supported by NORDA.]
Effects of the hydraulic anisotropy and the elastic anisotropy of a porous bottom on the acoustic propagation in shallow water
Authors: Yumamoto Tokuo , Badiey Mohsen
Published: January 2006

The layered anisotropic porous bottom was modeled by the stress-displacement matrix derived from the Biot equations for the anisotropic porous media. The effects on the acoustic mode attenuation of the anisotropy in the permeability and the elastic moduli of sediments were calculated for the realistic range of the physical properties of naturally consolidated sand deposits and the frequency range of 10–3000 Hz. It was found that the anisotropy in permeability has a significant influence on the acoustic mode attenuation while the anisotropy in the elastic moduli has a small influence. [Work supported by ONR.]
Angle-resolved spectroscopy of fluid-filled porous graphite
Authors: Muratore J. F. , Carleton Herbert R.
Published: January 2006

We have investigated the ultrasonic properties of water-saturated porous graphite as a planar sample is rotated in the field of an ultrasonic beam over the frequency range of 0.1–10 MHz. Amplitude spectra are calculated for a range of rotational angles and show effects due to reflection and refraction of the beam, mode conversions, and extensive attenuation and dispersion in the bulk materials. Corrections due to the finite width and diffraction of the beam are to be taken into account to show any shifts in time delay that might affect the accuracy of the data. Energy conversion to a shear mode at “normal” incidence is clearly demonstrated in the time domain signals and shown to account for shifts in apparent amplitude of the longitudinal mode. Our results demonstrate the effectiveness of digital signal processing and selective windowing in FFT analysis in studying the different mechanisms involved in the behavior of such highly dispersive materials subject to elastic wave propagation.
Some personal recollections of early experiences on the new frontier of electroacoustics during the late 1920s and early 1930s
Authors: Massa Frank
Published: January 2006

During this brief presentation, time will be turned back a half-century to permit some personal recollections of early experiences as we explored the new frontiers in electroacoustics. The availability of the vacuum tube for the amplification of weak signals made possible the practical application of a variety of wide-range low-sensitivity transduction techniques for the generation and reproduction of sound. Our training in electrical engineering provided an understanding of electrical measurements and design techniques that we could adapt for new specialized uses during our early stages of acoustic measurements and electroacoustic research. The demands of the new talking picture industry for improved electrical recording and reproduction of sound helped finance the costs of electroacoustic research which resulted in rapid progress in the sound reproduction and recording industry during the early 1930s. In less than a decade the reproduction of sound was transformed from the primitive limited frequency range of the mechanical phonograph to the high quality electrical recording and reproduction made possible by the rapid advances in electroacoustic engineering.
Engineering highlights of the LP record
Authors: Gravereaux Daniel W.
Published: January 2006

For 35 years, the long playing microgrove 3313 rpm disk record has brought the highest fidelity programming of any mass media to the consumer. This is due to the valued efforts of many engineers, scientists, and technicians in the development and implementation of microgroove mastering techniques, cutting and playing transducers, electroplating, stamping techniques, lacquer blanks, cutting styli, mastering lathes, presses, and vinyl formulation. This paper presents a few of the highlights in the engineering of the most standardized sound medium in the world—the LP.
Reminiscing—The stereophonic record
Authors: Roys H. E.
Published: January 2006

The author became active in the sound recording field in the early 1930s and remained active in that field until retirement in 1967. When, in 1957, two slightly different systems of recording stereophonic records were introduced for standardization he was a member of the engineering committee of the Record Industry Association of America and Chairman of the Phonograph Committee of the Electronic Industries Association. The situation was unique in that stereophonic recorders and pickups were not readily available and the choice for standardization had to be based largely upon theoretical considerations. The difference between the two was slight. The V-L system recorded one channel vertically and the other laterally. The 45-45 system recorded both channels vertically, but at a 45° angle with respect to the surface of the disk. Record engineers in Europe gathered and decided in favor of the 45-45 system. Engineers in this country did likewise. Thus for the first time in the history of records a common agreement with respect to standardization was reached prior to mass production.
Influence of reverberation room volume on measured absorption coefficients
Authors: Warnock A. C. C.
Published: January 2006

Recent absorption measurements in four rooms ranging in volume from 16 to 250 m3 suggest that the measured coefficients depend on the logarithm of the room volume; i.e., smaller rooms give smaller coefficients. Similar effects are suggested by round robin measurements in other countries. Absorption coefficients are also found to depend on the decay rate in the reverberation room without the specimen. These results will be presented and their implications with respect to standard tests will be discussed.
Simpler realization of ear simulators using tuning stubs instead of Helmholtz resonators
Authors: Schroeter Juergen
Published: January 2006

The Zwislocki- and the IEC711- ear simulators are the widely accepted standard devices whenever a mechanically stable representation of the human ear impedance is needed, e.g., for earphone calibration. Though the design of these simulators is rather complex [see Burkhard, J. Audio Eng. Soc. 25, 1008–1015 (1977) for some related problems], they were not intended to reveal “correct” results above 10 kHz. Recently measurement techniques for obtaining ear impedances data up to 20 kHz have become available [Joswig, Acoust. Soc. Am. Suppl. 1 69, S14 (1981) and Hudde, Acoust. Soc. Am. 73, 24–31, 242–247 (1983)]. To construct an ear simulator for high frequencies we studied the effect of closed-end stubs of small diameter to replace the lumped-parameter resonators used so far. These stubs do not require any special damping material. The geometrical tolerances are high. An a priori error estimation is possible during computer simulation. Predicted and measured results agree well enough to make a posteriori fine tuning redundant.
Characteristics of the FFP to tonal stimuli
Authors: Resnick S. B. , Heinz J. M. , Bookstein E. W. , Pagano R. V.
Published: January 2006

The FFP to tone bursts of 12.8-ms duration was measured over a 51-ms period using multichannel recording for seven normal-hearing adults. Averaged response waveforms based on 8192 trials were obtained at each of seven frequencies (between 312 and 1250 Hz) at each of four signal levels (10, 30, 50, and 70 dB nHL). The averaged waveforms then were subjected to various analyses including bandpass filtering (using digital filters centered at the test frequency and its second harmonic), spectral analyses for selected post-stimulus intervals and cross correlation (with the input stimulus). Preliminary review of the data provides evidence of the presence of the FFP at signal frequencies yielding the largest response and of marked alterations in response complexity as a function of stimulus frequency and level. Results of more detailed analyses and comparison of the FFP with responses to clicks and click trains will be presented. [Work supported by NINCDS.]
Speech understanding of older adults: A preliminary study
Authors: Elliott Lois L. , Lyons Laura , Busse Lu Ann
Published: January 2006

Forty-two normal older adults, aged 60–75 years, were tested on a battery that included the Speech Perception in Noise (SPIN) test, conventional, and experimental pure tone sensitivity, the W-22 test in quiet and noise, open- and closed-set identification of synthesized syllables that differed in the place of articulation feature, syllable discrimination, the Block Design subtest of the WAIS and the Concept Formation subtest of the Woodcock-Johnson Psychoeducational Battery. Results showed considerable variability on all measures. Only performance on the W-22 Test in noise and sensitivity at 4 kHz were significantly related to absolute levels of performance on low- (LP) and high-predictability (HP) SPIN test sentences. No test variables were significantly related to relative performance on HP and LP sentences. The differing patterns of results for different subjects of this homogeneous sample having excellent language skills suggested that: (1) a larger study in which linguistic abilities were systematically manipulated might produce a different outcome and (2) data for 400–500 similar older adults might show significant but differing patterns of processing auditory stimuli, particularly in the extent to which cognitive processes contribute to listening. [Work supported, in part, by NSF.]
Phase estimation for transfer function of multi degree-of-freedom-systems
Authors: Lyon Richard H.
Published: January 2006

The use of statistical estimates for vibratory response is now a well-established procedure using the methods of SEA. It has generally been assumed that while one could estimate the average response in frequency bands, statistical methods can say little about the phase of response. But the phase is very important in some applications of transfer function analysis, such as waveform reconstruction, and it would be very desirable to have procedures for estimating transfer function phase on the basis of general structural features in the way that SEA uses such features for estimating average response. Some recent developments in the estimation of the phase of structural transfer functions show promise that phase can be estimated from general system parameters. The use of phase information in waveform reconstruction and the role of these new developments in designing inverse filters for such reconstructions are reviewed.
An approach to the statistical energy analysis of complex systems
Authors: DeJong Richard G.
Published: January 2006

The principles of SEA have been used to formulate a procedure to analyze the dynamic response of complex systems. This procedure allows for individual components of a system to be modeled separately and then combined with other components to construct a complete system model. An analysis is presented that shows that the requirement for a high modal density in each component can be relaxed under certain conditions which allows the procedure to be used at lower frequencies. The procedure has been implemented in a computer program, and some examples of its application and comparisons to measurements are given.
Conference microphone with adjustable directivity
Authors: Flanagan J. L. , Kubli R. A.
Published: January 2006

Designs are given for fixed-steered line-array microphones suitable for teleconference applications. The steering is arranged so that the array can be located out of line-of-sight of the conferees. The directivity pattern of the transducer can be selected to give effective spatial coverage for a variety of conference conditions. Additionally, the designs utilize acoustic summation and anti-aliasing filtering. They require only an inexpensive electret element as the transducer. Theoretical responses are calculated and plotted on an Apple II computer. A prototype model is fabricated, and experimental measurements, made under free-field conditions, are shown to compare satisfactorily with the theoretical responses.
Echolocation in Harbour seals: Maybe they can do it after all
Authors: Renouf Deane
Published: January 2006

Though there is indirect evidence to indicate that various species of seals are capable of some form of echolocation, all previous attempts at an experimental demonstration of sonar capacities have met with negative results. I have obtained the following circumstantial evidence that Harbour seals can echolocate: (1) During three breeding seasons I have observed apparently healthy blind adult harbour seals including females which have successfully raised pups. (2) When visual cues are reduced, harbour seals make click vocalizations similar to those of animals which are known to echolocate. (3) They are able to find live fish in total darkness, producing clicks while doing so. (4) One seal trained to retrieve a ring which he first had to find in a 10-m-diam tank performed as well in the dark as in daylight, but clicked only when he could not use vision. I obtained a more rigorous demonstration of Harbour seal sonar when I was able to train an animal to discriminate between two visually identical rings which differed in acoustic impedance. When the acoustical properties of the rings were made equal, the animal was no longer able to distinguish between them. Very faint single or doublet clicks were recorded during the animal's performance, and it is suggested that quiet distinct signals may have been appropriate in an enclosed tank when the objects to be discriminated were suspended close to the enclosure's walls. The reasons why the training procedures used in this demonstration were successful are discussed, and the limitations of the conclusions which can be drawn from such results are outlined.
Energy partitioning and optical-to-acoustic conversion efficiency during laser generation of underwater sound
Authors: Pierce Allan D.
Published: January 2006

Two mechanisms (thermoacoustic and ablative) are considered with regard to how much optical energy is eventually transformed into sound. The analysis of the former begins with a fluid dynamic analysis of the generation of entropy and acoustic modal fields taking into account viscosity and thermal conduction. The acoustic modal field satisfies the Westervelt-Larson inhomogeneous wave equation while the entropy modal field satisfies a transient heat conduction equation with similar source term. The derivation demonstrates that the Westervelt-Larson equation is valid under much broader circumstances than was previously asserted by Bozhkov and Bunkin. The bulk of the absorbed optical energy goes into the entropy mode, but the acoustic portion can be enhanced if the spatial and temporal dependence of the energy deposition resembles a solution of the wave equation, such that initially generated waves are continually pumped by the source. An upper limit to the conversion efficiency is of order (β/ρcp)pmax, where β is coefficient of thermal expansion and pmax is maximum attained (by source pumping) acoustic pressure in the source region. Ablation generates sound because of the recoil force acting on the surface when evaporated material jets off; the corresponding acoustic radiation efficiency is estimated using a model proposed by Bunkin et al. [JETP Lett. 13, 341–343 (1971)]. [Work supported by ONR.]
Models of fluid structure interactions to optimize acoustics performance of sonar systems
Authors: Larcher Jacqueline , Parot Jean-Marc , Berhault Jean-Paul
Published: January 2006

In sonar systems, the interaction of transducer elements with the inner dome cavity and the boundary layer with the dome structure affect the overall acoustic performance of the system in terms of aberrations and self-noise. Simple mathematical models have been derived to represent both phenomena. For acoustic aberrations resulting from coupling between the transducer and the acoustic cavity plus dome structure, an analytic numerical model has been used to identify significant technological parameters controlling the performance. A statistical energetic model describes coupling between the hydrodynamic boundary layer, the dome dynamic structural behavior and the inner sonar cavity. Experimental data have been collected on full scale and model sonar structures representing realistic excitation and loads conditions. Results of theoretical models and experimental data show good agreement on the effects of cavity modes and area mass for acoustic aberrations and of dome structural dynamic properties for hydrodynamic self-noise.
Filter characteristics of low-frequency cochlear nerve fibers as determined by synchrony response patterns to two-component signals
Authors: Greenberg Steven , Geisler C. Daniel , Deng L.
Published: January 2006

The tuning and filter characteristics of cochlear nerve fibers, as conventially determined by stimulation with single-component signals, are usually intensity level-dependent. Shifts in characteristic frequency and significant deterioration of frequency selectivity are often observed at supra-rate-saturation intensities. In the present study relatively level-invariant estimates of characteristic frequency (CF) and frequency selectivity were obtained for low-frequency (<3 kHz) cochlear fibers in the cat via stimulation with two (equi-amplitude)-component signals. Characteristic frequency was estimated by on-line analysis of the fiber's synchrony response pattern to a two-component signal whose bandwidth was approximately 10%–20% of the unit's CF. Estimates of fiber CF remained relatively constant over a 60 to 80 dB range of intensities. Frequency selectivity (for a two-tone complex) was determined by setting either the upper or the lower signal component equal to the unit CF and varying the frequency of the second component over an octave range. Two-component signals provide a considerably higher estimate of a fiber's frequency selectivity than is commonly observed using single-component stimuli. [Research supported by NIH.]
Acoustic response properties of units in dorsal cochlear nucleus of unanesthetized, decerebrate gerbil
Authors: Voigt Herbert F.
Published: January 2006

Single unit recordings were made in the dorsal cochlear nucleus (DCN) of unanesthetized, decerebrate Mongolian gerbils. Access to the gerbil DCN was obtained using a newly described approach [Frisina et al., Hearing Res. 6, 259 (1982)]. Single units, recorded with 3M NaCl filled micropipette electrodes (20 Mohm typical), were classified into three types (II, III, or IV) based on their responses to best frequency (BF) tone bursts and their rates of spontaneous discharges. Type II units have little or no spontaneous activity and are excited by BF tones at all levels above threshold. Type III units are also excited by BF tones at all levels above threshold, but have spontaneous activity rates that exceed 2.5 spikes/s. Type IV units are excited over a narrow range of sound levels near BF threshold, but are strongly inhibited at higher levels. Thus all unit types found in the unanesthetized, decerebrate cat DCN [Young and Brownell, J. Neurophysiol. 39, 282 (1976); Young and Voigt, Hearing Res. 6, 153 (1982)] are also found in gerbil. [Work supported by NIH.]
Music of the animals
Authors: Carterette Edward C. , Shipley Carl
Published: January 2006

We examine the question and some possible answers of whether animals make and appreciate music. We take as the material of music such aspects as pitch, intensity, timbre, texture, harmony, frequency modulation, and duration as well as rhythm which is just the interaction of all these aspects in structured patterns. Our answer is that a lot of God's chillun got rhythm.
Comparison of acoustic experience of studio recordings and live concerts
Authors: Sotiropoulou Alexandra G. , Fleming David B.
Published: January 2006

It has been common in recent years to use recorded music in the investigation of subjective qualities of concert hall acoustics. The object of this paper is to compare experimental results from recorded music evaluations and live concert evaluations. A list of 54 opposite labels describing acoustic qualities of concert halls were used at the poles of bipolar rating scales in the evaluation of studio recordings. The raw judgments were analyzed by factor analysis and five independent factors were produced, namely body, clarity, tonal quality, extent, and proximity. The validity of these results was then tested in the environmental complexity of live concert conditions. To this end 27 scales were evolved to represent the previously obtained factors and were used at three live concert evaluations. Four to five independent factors were produced depending on the concert situation. Four of these factors, namely body, clarity, tonal quality, and proximity had also previously emerged; two factors which emerged only in the live concerts were spaciousness and intimacy [A. G. Sotiropoulou et al., Proc. Inst. Acoust., Edinburgh (1982)]. These results show that there are independent sets of acoustic qualities (factors) common to the studio recordings used in this study and to live concerts.
Music performance acoustics and room shape: An investigation employing an images model of room acoustics
Authors: Edwards Nicholas A.
Published: January 2006

Critical listeners often observe that rectangular (shoe box) rooms have “better acoustics” for music than fan shaped rooms of similar size. In this paper we examine the relationship between room shape and some physical aspects of souns fields in the room. The tool for our analysis has been a geometric acoustics (images) model implemented on a microcomputer. Three-dimensional impulse responses have been computed for some simple fan-shaped, reverse-fan-shaped, and rectangular rooms. Various means of graphical display are used to point out those trends in the time and space distributions of the impulse response that are tied to the fundamental shape of the room. Lateralization of the souns field and development of the reverberant field are two acoustical processes in particular that have their roots in the architecture of the space. Drawing on the past two decades of research into the influence that the direction of arriving sound has on listener perceptions and preferences for music, we identify links between the “sound” of a room and its shape.
Mathematical and computational issues in the deconvolution of a finite-length wavelet from a room impulse response under noisy conditions
Authors: Walsh John P.
Published: January 2006

The theoretical and computational issues which arise in the design and use of algorithms for digital deconvolution are discussed. Derivation of room impulse responses from measurements made using source signals which do not exhibit delta function behavior, under noisy conditions imposed by both the ambient conditions on-site and finite precision in the application of the deconvolution filter, form the focus of the paper. The genealogy of these methods in the literature of time series analysis, geophysical signal processing, and digital image restoration is described.
Binaural interaction in hearing impaired listeners
Authors: Gabriel Kaigham J.
Published: January 2006

The binaural hearing abilities of four sensori-neural loss listeners were tested in four experiments: (1) interaural time discrimination, (2) interaural intensity discrimination, (3) interaural correlation discrimination, and (4) binaural detection experiments. All tests were conducted on each subject using third-octave bands of noise centered at 250, 500, 1000, 2000, and 4000 Hz. “Binaural Audiograms” can be obtained by plotting the ration of normal discrimination jnds to measured discrimination jnds versus frequency on a log-log scale. In general, the frequency dependence of binaural hearing loss, so defined, appears unrelated to the frequency dependence of hearing loss as measured by current monaural audiometric techniques. Furthermore, impairements of interaural time discrimination are independent of impairments in interaural intensity discrimination. Finally, the MLD alone was not related to loss of interaural time or intensity sensitivity. Two of the subjects tested showed elevated NoSπ and NoSo thresholds, poor interaural time and intensity discrimination but a “normal” MLD. [Work supported by NIH Grant NS10916.]
The extension of binaural crosscorrelation modelling by a mechanism of lateral inhibition
Authors: Lindemann Werner
Published: January 2006

To model the stationary and dynamic behavior of the binaural system we present an extension of the well-known binaural crosscorrelation models which is based on a lateral inhibition mechanism along the crosscorrelation axis. The running interaural crosscorrelation is calculated by counting spike coincidences in frequency bands. The resulting neural activity distribution is fed into the lateral inhibition mechanism. The required EE and EI gates can be combined in different ways to optimize the performance of the model. A wide field of psychoacoustic lateralization and localization data can be explained very effectively. For Example, interaural phase as well as interaural level differences are evaluated in order to model lateralization as well as time-intensity trading. For nonstationary signals the model can explain the law of the first wavefront and related psychoacoustic effects. The model parameters are matched to the psychoacoustic data by choosing optimal time constants of the spike firing process, the spike coincidence window, and the inhibition mechanism. Some model results will be presented graphically in the form of “neural activity patterns.” [Work supported by the Deutsche Forschungsgemeinschaft.]
Parametric acoustic conversion in ocean sediments
Authors: Yoon Suk Wang , Griffy Thomas A.
Published: January 2006

The interaction of acoustic waves from a parametric acoustic array at a water-sediment interface has been studied theoretically. This investigation was motivated by the observation of better penetration of acoustical energy into sediments using a parametric acoustic array rather than a conventional source [T. G. Muir, C. W. Horton, Sr., and L. A. Thompson, J. Sound Vib. 64, 539 (1979)]. In order to treat the nonlinear interaction of sound waves in a sediment, the inhomogeneous elastic wave equation for a solid was solved. One effect of the nonlinear terms in this equation is the coupling of compressional and shear waves. The separation of the coupling effect is shown. The primary waves from a parametric source are expected to excite Stoneley waves along the water-sediment interface. The Stoneley waves are assumed to serve as a source for parametric acoustic conversion in the sediment. The analytic solutions of the inhomogeneous wave equation are spherical waves modified by an angular dependence in the amplitude. [Work supported by ONR.]
Farfield decomposition of acoustic waveforms in a fluid-filled borehole
Authors: Kurkjian Andrew L.
Published: January 2006

In acoustic well logging, a transient acoustic source is placed within a mud-filled borehole for the purpose of exciting refracted compressional and shear waves in the surrounding formation. We model the downhole environment by an infinite fluid-filled cylinder surrounded by an infinite solid formation. An isotropic point source is placed on the axis of the hole and an exact solution for the field in the hole is obtained in the frequency-wavenumber domain. Space-time waveforms are obtained by numerically transforming this solution. The waveforms consist of compressional and shear refracted waves plus modes, which are guided by the hole. In this paper we numerically compute these individual components of the field. The modes are obtained by locating poles and evaluating residues. The refractions are obtained via numerical branchcut integrations. A vertical branchcut is used which converges rapidly but only gives accurate results in the farfield.
Fundamental frequency characteristics of southern Vietnamese phonemic tones in mono- and disyllables
Authors: Seitz Franz
Published: January 2006

Fundamental frequency (F0) trajectories were measured for 87 Vietnamese monosyllables and 72 disyllables using a computer program which employs autoregressive spectral modeling with cepestrally based periodicity estimation. The study addresses the issue of invariance versus context-dependency of the F0 patterns associated with the five phonemic tones; variability of pattern as a function of proximate tones, as well as segmental composition of the utterance, was examined. The findings are compared with those of the definitive acoustic phonetic studies of Vietnamese tones to date [M. S. Han, U.S.C. Studies in the Phonology of Asian Languages VII (1969); M. S. Han and K-O. Kim, J. Phonet. 2, 223–232 (1974)]. The present test utterances, unlike those of previous studies, were selected on the criterion of phonotactic representativeness. Han's canonical representations of the tones' F0 patterns are corroborated in the case of monosyllables, with little effect from segmental composition. Disyllables involving sonorant consonants at the syllable juncture, however, do not have F0 patterns that are sequences of two canonical trajectories. The F0 pattern characteristics of these signals are discussed.