bluuebunny/crossref_metadata_2025 huggingface dataset:
Stimulus-oriented model for the discrimination of Gaussian noise samples
Authors: Rickert Martin E. , Robinson Donald E.
Published: October 2005

Consider a two-interval same-different task in which listeners are asked to discriminate between trials on which a sample of noise is presented twice and trials on which two different samples are presented. Previous research has used this method to determine the effects of a wide range of stimulus conditions including temporal location of an uncorrelated segment, duration, bandwidth, correlation, and overall level [T. E. Hanna, Percept. Psychophys. 36, 409–416 (1984); S. F. Fallon and D. E. Robinson, J. Acoust. Soc. Am. 92, 2630–2635 (1992)]. The data indicate that discriminability is best when changes occur at the end of the sample and that the ratio of the duration of the target segment to the total duration is independent of overall duration. In this paper, a stimulus-oriented model for discriminating samples of Gaussian noise is developed. The model is a derivative of the equalization–cancellation theory of binaural masking level differences [N. I. Durlach, J. Acoust. Soc. Am. 35, 1206–1218 (1963)] and of Jeffress’ models of monaural masking [L. A. Jeffress, J. Acoust. Soc. Am. 44, 187–203 (1968)]. This approach begins with a cancellation stage in which the waveforms from the two intervals are jittered in amplitude of differenced. Then, the power of the difference waveform is approximated in a manner similar to Jeffress’ leaky integration. Predictions of the model will be compared to the data of Fallon etal. [Work supported by AFOSR.]
Estimation of dynamic forces via modal decomposition of operational deflection shape measurements
Authors: Warwick David C. , Gilheany John J.
Published: October 2005

The results of modal analysis are used to derive a set of modal filters that are applied to operational deflection shape measurements to estimate modal contributions and physical forces for structures subject to multiple, correlated and uncorrelated, external excitations. Singular value decomposition is applied to measured cross spectral density functions to decompose response measurements into contributions associated with each independent external excitation. Generalized and physical forces, coherent to each independent source, are determined from estimated modal parameters. The approach is demonstrated for single and multiple, correlated and uncorrelated, external excitations.
A simple test of the modal strain energy method
Authors: McDaniel J. Gregory , Ginsberg Jerry H.
Published: October 2005

Nashif etal. [VibrationDamping (Wiley, New York, 1985)] present a ‘‘modal strain energy method’’ (MSEM) that has seen increased use in the finite element community to estimate modal loss factors in elastic–viscoelastic structures. The method enables one to predict dynamic response without explicitly accounting for hysteretic damping in the free vibration analysis. Despite its wide usage, there does not seem to have been prior formal analyses of its validity. The presentation will report such a test of MSEM predictions for a two-degree-of-freedom system in which the two masses are connected by dissipative and elastic elements. The evaluations explore the dependence of MSEM on basic parameters characterizing stiffness, inertia, and damping. The main conclusion is that MSEM is very accurate if dissipation within the viscoelastic substructure is sufficiently low. Raising either the inertia or stiffness of this part of the system seems to enhance the accuracy of MSEM for a fixed value of its damping factor.
Quantum chaos methods applied to high-frequency plate vibrations
Authors: Legrand O. , Schmit C. , Sornette D.
Published: October 2005

The first investigation of the quasiclassical regime of thin plate vibrations in the high-frequency regime is presented. Using an efficient numerical scheme to compute many eigenfrequencies of a stadium-shaped plate, it is found that the distribution of level spacings and the spectrum rigidity follow the GOE (Gaussian orthogonal ensemble) random matrix statistics. An asymptotic equivalence between the spectrum of a clamped plate and that of a membrane with a mixed boundary condition is derived. Also, examples of eigenmodes that present scars are present, and their quantization is given. [This work has been published in Europhys. Lett. 18, 101–106 (1992).]
Developing a MIDI pitch detector
Authors: Kim Youngmoo , Everbach E. Carr
Published: October 2005

Recent interest in automated pitch detection [J. Acoust. Soc. Am. 92, 2428–2430 (A) (1992)] has led to develop a device whose purpose is to transcribe the musical lines of single-voice instruments (e.g., flute, trumpet) in a MIDI format using Apple MacintoshTM computers and software. In contrast with other devices requiring rapid digital sampling of the audio signal and extensive computational and digital signal processing resources, this is an essentially analog electronic device based upon a phase locked loop and matched filter that strips off the higher harmonics of the instruments’ waveform. The signal that results is nearly sinusoidal, allowing the use of the Macintosh’s own modest built-in digital sampling capabilities for transcription of the musical line played on the instrument into a MIDI format.
Absorption of sound by noise in one dimension
Authors: Denardo Bruce , Larraza Andrés , Atchley Anthony A. , Dorff Steven
Published: October 2005

A special case of a prediction by O. Rudenko and A. Chirkin [Sov. Phys. JETP 40, 945–949 (1975)] is that a small-amplitude monofrequency sound wave will decay as a Gaussian as a result of interaction with finite-amplitude noise, if the waves are all moving in one direction. An experiment to verify this will be discussed. The apparatus includes a 21-m-long, 7-segment, thick-walled aluminum tube, with two high-intensity compression drivers coupled to one end and an absorber at the other end. A simplified perturbative treatment of the problem, as well as possible applications, will be presented. The importance of this system as one in far-off equilibrium [A. Larraza, to be submitted to Phys. Rev. Lett.] will also be discussed. [Work supported by NPS Direct-Funding Program and ONR.]
Sonoluminescence spectra
Authors: Atchley Anthony A. , Carlson J. T. , Gaitan D. Felipe , Lewia S. D. , Maruyama X. K. , Lowry M. E. , Moran M. J. , Sweider D. R.
Published: October 2005

The spectra of picosecond sonoluminescence were measured with two separate instruments (a spectrometer/CCD detector system and a scanning monochrometer/PMT detector system) for bubbles levitated in water and in glycerin/water mixtures. Results of measurements made with the scanning monochrometer/PMT detector system, which required 10 to 15 min to acquire a complete spectrum, agree favorably with those published previously by Hiller etal. [Phys. Rev. Lett. 69, 1182 (1992)]. However, measurements made with the spectrometer/CCD detector system, which required approximately 30 s, indicate that the spectrum continually changes over this time scale, with no apparent changes in the input parameters. [This work was supported in part by the Defense Nuclear Agency and the Office of Naval Research. Portions of this work were performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under Contract number W-7405-ENG-48.]
Temperature distribution and heat transfer from the pulsating bubble in ultrasonic field
Authors: Yang H. , Ryu J. C. , Kwak H. , Hong J.
Published: October 2005

Gas bubble behavior immersed in liquid under a high-intensity ultrasonic field was studied by using a self-consistent model. In this model, the temperature distribution of the gas inside the bubble was obtained by solving analytically the continuity and energy equations for the gas. Also heat transfer between the gas inside the bubble and the surrounding liquid was considered by solving the mass, momentum, and energy equation for the liquid. With this model, the polytropic approximation is no longer required to calculate the internal pressure of the oscillating bubble under ultrasonic field. Under the periodic ultrasonic field with an amplitude of 110 kPa and a frequency of 20 kHz, the temperature of air at the bubble center with equilibrium radius of 20 μm reached as high as 5000 K at the time of bubble collapse. The heat flux from the bubble to the surrounding fluid by conduction is above 10 MW/m2 at this stage. The pressure inside the bubble at this stage is about 10 bar, which is much less than that obtained by a previous model. Calculation results support the hot spot theory, which states that the phenomenon of sonoluminescence is due to chemiluminescence by the high temperature of gas inside the bubble.
The acoustic interaction forces between two fluid spheres in an acoustic field
Authors: Zheng Xiaoyu , Apfel Robert E.
Published: October 2005

An object in a sound field will scatter the incident wave and experience the so-called acoustic radiation force, which is a nonlinear time average effect associated with the incident wave. When two objects are present, the total acoustic radiation force on either object will include the interaction portions due to the other’s scattered field of the primary wave. The acoustic interaction force between two fluid spheres in a plane wave field is investigated by calculating the force on one sphere, which is assumed to be small compared to the center distance between them. Using the method of Yosioka [K. Yosioka and Y. Kawasima, Acustica 5, 167–173 (1955)], a general formula for the radiation force on one sphere is derived that shows dependence on the resonant modes of the other. It is noted that in the radiation force expression there are cross terms involving the primary plane wave and scattered wave. For two small bubbles, this result is the same as the Bjerknes force expression that is obtained by others under the approximation of very long wavelength. Calculations are also done for the case of a standing wave field. [Work supported by NASA through JPL Contract No. 958722.]
Ultrasonic four-wave mixing mediated by a suspension of microspheres in water: Comparison between two scattering theories
Authors: Simpson Harry J. , Marston Philip L.
Published: October 2005

Two ultrasonic pump waves are used to produce a grating in a suspension of 25-μm-diam latex particles. A higher frequency ultrasonic wave is used to probe the established grating to produce ultrasonic Bragg scattering. The scattering depends strongly on the pump waves and is an unusual class of nonlinearity. A previously summarized model of the interaction [H. J. Simpson and P. L. Marston, J. Acoust. Soc. Am. 90, 2244 (A) (1991) and 91, 2351 (A) (1992)] uses an Epstein layer approximation and effective medium approximation. This previous analysis is compared with a Fourier series approximation of the grating and the resulting predicted scattered wave fields. The Fourier series expansion is only valid when the Bragg condition is satisfied, thus giving no information off the Bragg peak. The two models match at higher pump pressures and predict similar onset pressures, but differ slightly in the medium pressure region. Both results are compared to experimentally measured scattering amplitudes for a range of probe frequencies and pump pressures. [Work supported by ONR.]
Burgers’ equation generalized for absorption obeying a power law
Authors: Szabo Thomas L.
Published: October 2005

Burgers’ equation applies to finite-amplitude waves propagating in a medium with absorption that has a quadratic frequency dependence. Numerical solutions of a modified Burgers’ equation have been obtained in the frequency domain for other types of losses; however, a complete set of time domain nonlinear equations corresponding to power law attenuation has not been available. Power law attenuation is defined by the equation, α(ω)=α0‖ω‖y, where α0 and y are arbitrary real constants, and ω is angular frequency. Blackstock [J. Acoust. Soc. Am. 77, 2050–2053 (1985)] has suggested that Burgers’ equation could be generalized if an appropriate operator L could be found such that the equation could become pz−L*p=Bppτ, where p is pressure, B is a constant, τ is delayed time, and the subscripts denote derivative operations. The L operators have been derived based on a new causality principle and parabolic wave equations for power law loss. The resulting time domain equations extend Burgers’ approach to finite amplitude propagation in media with arbitrary power law absorption.
Pitch, masking, and Ohm’s law for hearing
Authors: Malzan Jerry
Published: October 2005

Ohm’s law for hearing asserts that psychological phenomenon of pitch can be identified with the physical phenomenon of frequency. More precisely, the assertion is that perceived pitches are precisely those appearing in the Fourier spectrum of a periodic vibration having all frequencies in the audible range. Experiment shows, however, that both parts of this if and only if statement are false. Pitches may arise without a corresponding frequency (the ‘‘pitch’’ problem) and pitches may be absent when there is a corresponding frequency (the ‘‘masking’’ problem). Here an attempt is made to deal with these problems simultaneously, using only the fact that the ear is a short-time analyzer, rather than the long-time analyzer that Ohm’s law for hearing would require. The model used is quite simple, requiring only one parameter, and is in reasonable accord with experimental results. Residue pitch is computed in the time domain, while other pitches are computed in the frequency domain with the possibility, however, of masking. [Work supported by NSERC.]
Spectro-temporal enhancement measured by loudness matching
Authors: Fantini Deborah A. , Summerfield Quentin , Palmer Alan R.
Published: October 2005

If one member of a series of equal-amplitude harmonics starts a few hundred milliseconds after the others, it may be ‘‘enhanced’’ and stand out perceptually. Viemeister and Bacon [J. Acoust. Soc. Am. 71, 1502–1507 (1982)] demonstrated that components produce more forward masking when enhanced than when present in a harmonic series without enhancement. Thus, enhancement appears to involve an increase in the internal level of a component. The present study was conducted to determine whether this result is also found in a loudness-matching task. Stimuli were derived from a harmonic series with a fundamental of 200 Hz. A 500-ms adaptor consisted of the series without the 1.8-, 2.0-, and 2.2-kHz components. A 100-ms standard included the 2-kHz component. Subjects heard the standard in the left ear followed by an identical 100-ms sound (the ‘‘comparison’’) in the right ear. They matched the loudness first of the background components and then of the 2-kHz component between the comparison and the standard. Preceding the standard by the adaptor reduced the loudness of the background components by 2 dB and raised the loudness of the 2-kHz component by 5 to 15 dB relative to the background components. Thus, loudness matching, like forward masking, demonstrates that enhancement increases the internal level of a component, but shows also that the levels of the background components are reduced.
Detecting asynchrony of a single component with synchronous and asynchronous standards
Authors: Zera Jan , Green David M.
Published: October 2005

Detecting asynchrony in either the temporal onset or offset of individual components in a multicomponent complex was investigated. A synchronous standard was constructed with all components having the same duration and starting and stopping simultaneously. The asynchronous standard was constructed by linearly delaying successive components of a complex, either at onset or at offset. The signal was created by altering the temporal position of a single component of the complex, either at onset or offset, relative to its temporal position in the synchronous or asynchronous standard. Thresholds were measured at onset or offset both for harmonic signals and for complexes in which the components were logarithmically spaced in frequency. For the onset condition in either the harmonic or logarithmic complex, the thresholds for detecting the asynchrony of a single component were greatly increased when the standard was asynchronous as opposed to synchronous. For the offset condition, the thresholds were not greatly affected by whether the standard was synchronous or asynchronous. [Research supported by NIH, AFOSR, and a Fulbright fellowship.]
Root locus equations for the vibrating diaphragm model of jet-pipe action
Authors: Elder S. A.
Published: October 2005

The vibrating diaphragm model of jet-pipe action described in an earlier paper [S. A. Elder, J. Acoust. Soc. Am. 96, 2411 (A) (1992)] has been extended by the development of root locus equations for laminar and turbulent half-jet resonators, which allow solution for the shear wave propagation constant at resonance, and estimation of the oscillation amplitude. The ‘‘force-drive’’ term in the pipetone system is shown to be associated with the inertia of the separated shear layer, with power being delivered to sustain the oscillation whenever the inertial force has a component in phase with sound particle velocity in the pipe mouth. Turbulent boundary layers thus produce corresponding larger driving force, for the same frequency and jet speed, since they tend to be thicker and so possess larger inertia. [Work partially supported by U.S. Naval Academy Research Council.]
Acoustics of a Chinese hand-exercise ball
Authors: Mansell Edward R. , Rossing Thomas D.
Published: October 2005

Pairs of steel balls, 3–4 cm in diameter, have been used in China as hand exercisers since the time of the Ming dynasty. Often a sounding device, consisting of a coil spring and a small steel ball, is placed inside the balls to produce a rather delicate tinkling sound as the balls are moved in circles in the hand. It is claimed that the balls can produce sounds ‘‘which are like the whistling of a dragon and singing of a phoenix.’’ The sound spectrum shows many strong partials up to 10 kHz or higher. The most identifiable pitch of G5 results from a partial at 773 Hz.
Scaling of bells
Authors: Sathoff H. John , Rossing Thomas D.
Published: October 2005

The fundamental frequency of a bell has roughly the same dependence on thickness and diameter as flexural vibrations in a circular plate, and thus in designing a bell chime or ensemble of bells, it would be possible, in principle, to scale all dimensions proportional to 1/f. Tonal considerations often dictate otherwise, however, and in practice different scaling laws are found in ensembles of large and small carillon bells, church bells, handbells, and ancient Chinese bells that have been studied.
Acoustics of ChoirchimesTM
Authors: Canfield Gregory H. , Rossing Thomas D.
Published: October 2005

Tuning-fork resonators, useful in acoustics lecture demonstrations [T. D. Rossing, J. Acoust. Soc. Am. 92, 2401 (1992)], can vibrate in a wide variety of modes. The Malmark ChoirchimeTM, consisting of a closed-end tuning-fork resonator with an attached handbell clapper, has become a popular musical instrument. The modes of vibration of two ChoirchimesTM, tuned to A3 and A4, are described. The observed modes can be classified into five categories: parallel bending, symmetric bending, out-of-plane bending, parallel torsional, and symmetric torsional. The lowest symmetric bending mode radiates a strong fundamental, which is greatly enhanced by the resonance of the tube, resulting in a sound spectrum in which the fundamental dominates (the next partial is generally 20 dB or more below the level of the fundamental).
Increasing the depth of field in holographic interferometry
Authors: Fystrom Dell O. , Rossing Thomas D.
Published: October 2005

Holographic interferometry is widely used to determine the modes of vibration in a wide variety of objects, such as musical instruments. Use of two or more object beams is a convenient and inexpensive way to increase the depth of field (or coherence volume) in holographic interferometry. This technique was used, for example, to make time-average holograms of the inside and outside surfaces of a vibrating drum shell simultaneously.
Hearing recovery in neonatal chicks after exposure to intense pure tones
Authors: Saunders James C. , Adler Henry J. , Doan Daryl E.
Published: October 2005

Neonatal chicks exposed to a 120-dB SPL pure tone at 0.9 kHz for 48 to 200 h exhibited a severe loss in auditory function. The growth and recovery of hearing loss was traced with a variety of peripheral evoked-potential and single-cell recordings. The growth of threshold shift and the loss of frequency selectivity reached asymptotic levels after 40 h and then remained constant to 200 h. At 0 days of recovery the magnitude of threshold shift in the most affected frequencies was 55–60 dB and tuning curves showed a 50% loss in selectivity. Nearly complete recovery of sensitivity and selectivity was noted 12–15 days post exposure. Severe recruitment was also seen in functions relating sound level to evoked-potential amplitude or single cell rate-intensity functions. The abnormal coding of intensity returned to normal within 3 days. The loss in function was associated with significant cochlear damage, and recovery was associated with considerable cochlear repair. The repaired cochlea, however, does not have a normal appearance. It remains to be explained how auditory function can completely recover in a cochlea with severe permanent structural defects. [Work supported by the NIDCD, PLHRF, and NOAR.]
Experimental radar-activated hazing system
Authors: Weber Richard A. , Filas Barbara A.
Published: October 2005

Migrating birds often use mine tailing facilities during migration, especially in arid areas throughout the west. Process chemicals in tailing facilities can adversely affect birds that use the facility as a resting and feeding location. Traditional audio hazing techniques have been ineffective because birds become habituated to the devices’ continuous and regular sound production. This project involved development and testing of a radar-activated bird deterrent system to haze birds away from tailing facilities. The system was tested at a mine tailing facility in northeastern Nevada. It was designed to provide radar coverage over a tailings facility and to automatically activate several audio hazing devices when a bird entered a specified zone. The theory behind such a system is that hazing is much more effective while birds are still in flight. Audio hazing devices activated included a stereo system, fire alarm, propane cannons, and a device designed and built by Knight Piesold to launch firecracker-like cartridges. Data were collected during the fall of 1990 and spring of 1991. The data collected shows that the system has promise as a method to haze migratory birds away from the tailings facility.
Effects of simulated aircraft noise on hearing, food detection, and predator avoidance behavior of the kit fox, Vulpes marotis
Authors: Bowles Ann E. , Francine Jon K.
Published: October 2005

Four kit foxes were captured south of Gila Bond, Arizona, in an area not overflown by aircraft. Hearing thresholds were measured by startle inhibition with a San Diego Instruments Startle Recording System. Shaped 200-ms tone bursts ranging from 100 Hz to 40 kHz in octave steps were delivered using a step-up, step-down procedure. Startle responses were elicited by a 40-psi air puff 30 ms in duration following 100 ms after the tone burst and startle intensity and latency were measured. Threshold at best frequency lay between −10 and −15 dB re: 20 μPa at 2–4 kHz and declined rapidly below 1 kHz and above 20 kHz. Foxes were trained to identify simulated prey and predator noise at the minimum level required for detection. Latancies to respond were measured in the absence and presence of simulated aircraft noise, simulated by recordings of F-4 fighter aircraft played for 40 min at 96 dB re: 20 μPa with onset rate of 25 dB/s. Foxes were also exposed to aircraft noise for 3 h while asleep during the day. Results available to date indicate that foxes can detect test signals and respond in the presence of aircraft noise; latencies to response are altered during tests but not after; and no changes in activity are detected during daytime exposures.
Marine turtle auditory behavior
Authors: Moein S. , Lenhardt M. , Barnard D. , Keinath J. , Musick J.
Published: October 2005

Auditory capacities of the Atlantic Loggerhead (Carettac. caretta) were assessed to develop a sound repelling system to be used in dangerous areas. To estimate sensitivity, auditory brain-stem responses (ABRs) were recorded in ten animals to clicks and tones (250, 500, 750, and 1000 Hz). Animals, removed from water, had electrodes implanted subcutaneously. Stimuli were presented to eardrum with a vibrator. Consistent responses occurred within the first 10 ms after stimulation, not unlike that recorded in nonmarine forms. ABR waveforms increase in latency with stimulus attenuation. Prior to ABR recording, sound-induced head movements were noted in most, but not all animals. Sound-induced swimming was also observed. A flight response within the artificial environment of a small tank may not predict natural behavior, hence animals will be placed in a saltwater pen and the experiments repeated with a sound source away from the animal. Finally animals fitted with transmitters will be released in the lower Chesapeake Bay. After settling into a selected area, they will be approached by a moving sound projector to determine if this sound induces flight.
Resonance frequency and damping constant of a spherical gas-vapor bubble in an infinite medium
Authors: Mao Yi , Crum Lawrence A. , Roy Ronald A.
Published: October 2005

The resonance frequency f0 and damping constant δ for free volume oscillations of a spherical bubble in an infinite medium are derived from the linearized, fundamental equations of fluid dynamics. There are three possible modes (acoustic, thermal, and mass diffusion) of wave propagation that satisfy the governing equations for the gas–vapor mixture inside the bubble. Outside it, only the acoustic and thermal diffusion modes need consideration because gas diffusion across the bubble surface into the liquid appears negligible for free oscillations. The parameters f0 and δ are values such that the boundary conditions can be satisfied. The dependence of f0 and δ on bubble size, ambient pressure, and temperature is examined. When a bubble contains a high concentration of gas, the values of f0 and δ agree with the results of Devin [J. Acoust. Soc. Am. 31, 1654–1667 (1959)]. When the concentration of vapor is high, it is found that there exists only one resonance frequency for free oscillations [compare the results of R. D. Finch and E. A. Neppiras, J. Acoust. Soc. Am. 53, 1402–1410 (1973)]. [Work supported by ONR.]
Direct measurements of the sound speed in the oceanic surface bubbly layer
Authors: Lamarre Eric , Melville W. Kendall
Published: October 2005

It is well known that wave breaking events create a bubbly layer a few meters thick below the water surface. The most important characteristic of this shallow channel is its sound-speed profile. Results are presented from two recent field experiments in which the sound-speed profile was directly measured in the first few meters below the surface for frequencies in the range 5–40 kHz. Preliminary results in moderate sea states (wind speeds less than 10 m/s) indicate that significant departures from the sound speed in bubble-free water occur in a shallow [O(1 m)] layer and are intermittent in time. Two dominant time scales are present. A fast time scale associated with the surface waves, which advect the bubble clouds horizontally with respect to the buoy; and a slow time scale O(100 s). Sound-speed reductions up to 150 m/s have been observed at 50-cm depth with 10-min means well above the 5 to 15 m/s previously cited in the literature. Other results including ambient sound, acoustic attenuation, and upward looking sonar measurements of the bubble clouds will be discussed. [Work supported by ONR.]
Sensitivity of modal amplitudes to warm surface mixed layers in the Greenland Sea
Authors: Pawlowicz Rich , Jin Guoliang , Lynch James F. , Worcester Peter
Published: October 2005

Six near-surface acoustic transceivers were moored in the Greenland Sea in an array approximately 200 km in diameter from October 1988 to August 1989. Transmissions with a center frequency of 250 Hz and a bandwidth of 100 Hz were made at 4-h intervals over most of the array, resulting in a multipath structure of early ray arrivals and later near-surface modal arrivals. During February and March the almost isothermal temperature profile resulted in an arrival pattern with the later arriving lower-order modes have greater amplitude. However, from mid-April onwards the pattern changed dramatically as amplitudes of the lowest-order mode became far smaller, and slightly earlier arriving modes became somewhat louder. At the same time, net surface fluxes changed sign, so one expects the formation of a shallow warm surface mixed layer (although the somewhat sparse historical data suggests that warm surface mixed layers are not seen for at least another month). One explanation for the amplitude changes is that modal coupling is induced by horizontal variations in the depth of this warm layer. a)On leave from Shanghai Acoustics Laboratory.
ATOC—New Zealand receiver site survey and acoustic test
Authors: Bannister R. W. , Guthrie K. M. , Kay J. S. , Bold G. E. J. , Johns M. D. , Tan S. M. , Tindle C. T.
Published: October 2005

Possible New Zealand receiver sites for the ATOC experiment have been investigated. A suitable site requires a water depth of 2000 m at a distance of 30 nm or less from the coast and an unobstructed acoustic path to California. A detailed site surveyed and an acoustic trial were conducted in September 1992. In the acoustic trial a series of 1.8-kg SUS charges was detonated off the California coast. Good signals were received in New Zealand at a distance of 10 360 km.
Enhancement of hydrodynamic flow noise by the regulation of air bubbles in a turbulent water jet
Authors: Korman Murray S. , Crum Lawrence A.
Published: October 2005

An experiment is performed to show that the near-field hydrodynamic flow noise (generated by a submerged water jet) is enhanced when the turbulent flow is modified to become a two-phase flow containing air bubbles. Pressure spectra, in the band 5–5000 Hz, are measured using a digital spectral analyzer from signals generated by a hydrophone placed at the axial and radial position (Z=4D and R=4D) from the nozzle exit diameter, D=0.635 cm. An amplification factor, G=∫ptwo-phase2 df/∫psingle-phase2 df, is measured as a function of the gross void fraction β of the air bubbles. Here, we measure β to be the ratio of gas volume flow rate (through the bubblemaker located at the nozzle entrance) to the water volume flow rate, Qg/Qw. The amplification G is measured as a function of β by keeping Qw constant (the nozzle velocity U=13.8 m/s) and varying Qg. Results show that G∼β2 and G∼20 at β=0.0065. The mean-squared pressure fluctuation p2≡∫ptwo-phase2 df is measured as a function of U by keeping Qg fixed and varying Qw. Results show that p2∼Um, where m=3.6, 4.3, and 4.7 for Qg=50, 86, and 136 sccm, respectively. [Work supported by NCPA.]
Signal parameter estimation via transfer matrix analysis
Authors: Cho Woon Hyun
Published: October 2005

A new algorithm is developed for estimating the delay times and spectra in mixed wave fields. The algorithm is applicable to a spatial and temporal data window in which more than two events are present. In implementing the method it is assumed that data are recorded at equispaced hydrophones located in a spatial window in which the delay times are constant. Application of a least-squares criterion reduces the mathematics to an eigenvalue problem. The eigenvalues are complex, and their magnitude determines the frequency-dependent SNR. The phase is a linear function of frequency with a slope that determines the delay time over unit hydrophone spacing. The input data consist of the cross-power spectra between subarrays that contain the same numbers of elements and are shifted by zero or one hydrophone separation. Examples illustrate the application of the algorithm to synthetic data.
Use of the vector Bragg wave-number scattering condition to measure turbulence
Authors: Goodman Louis , Szargowicz Diane , Oeschger John , Letcher S. V. , Hebda Peter
Published: October 2005

Acoustic scattering that satisfies the far-field Born approximation leads to a simple linear relationship between the scattered pressure field and the scattering field, namely the two are Fourier transform pairs. A set of laboratory experiments have been devised to exploit this relationship for the case of scattering from a turbulent field. Data are taken in a multiple scattering angle configuration such that the Bragg wave-number vector associated with each scattering angle pair is in the same direction. Use of broad bandwidth source and receiver transducers (250 to 750 kHz) then allows a three-dimensional fully resolved wave-number spectra of the turbulent field to be estimated. Results are presented for scattering from a turbulent buoyant plume. The data can also be used to examine the validity of the fundamental assumption of the far-field Born approximation.
Dynamic mechanical properties of violin wood and the tone qualities of violins. I: Audiofrequency complex shear compliance, modulus, and shear sound velocity and attenuation measurements
Authors: Fitzgerald Edwin R. , Hutchins Carleen M. , Hutchins Morton A.
Published: October 2005

Values of complex shear compliance (J*=J’−iJ‘), modulus, (G*=1/J*), and shear sound velocity and attenuation have been measured over a continuous frequency range from 10 to 10 000 Hz for samples of spruce and maple wood used in the construction of six violins. Measurements were made with an automated electromagnetic transducer system in which samples are sheared while clamped between stainless steel blocks. [E. R. Fitzgerald, Proc. Am. Chem. Soc. Div. Polymeric Mater. Sci. 60, 573–578 (1989); E. R. Fitzgerald, U.S. Patent 5,081,870 (1992)]. Four wood samples were measured for each finished violin, viz., samples of spruce and maple with and cross grain. As reported earlier, values of the shear parameters vary with frequency and grain orientation, but also with moisture content and the clamping force on the sample faces while they are vibrated in shear [E. R. Fitzgerald, J. Acoust. Soc. Am. 89, 1927(A) (1991)]. The details of the mechanical spectra of the six sets of samples vary, but, in general, several sharp, microstructural compliance modes are superimposed on broad retardation spectra [E. R. Fitzgerald, J. Acoust. Soc. Am. 33, 1305–1314 (1961)]. Comparisons among the six sample sets are made for the same clamping force at 20 °C and 52% R.H.
Measurement of flow rate past a clarinet reed
Authors: Chen Fang-Chu , Weinreich Gabriel
Published: October 2005

The relation of the air flow through a clarinet mouthpiece to the pressure difference across it and the size of the read opening has been investigated by connecting the mouthpiece to an air reservoir that is pumped to a partial vacuum and allowed to fill through the mouthpiece. The pressure in the reservoir is measured ten times per second until atmospheric pressure is restored. In principle, the rate of change of pressure determines the rate of air flow, so that the desired relationship is obtained. One difficulty comes from an ignorance of the reservoir air temperature, since completely adiabatic conditions cannot be assumed. Another is that the rate of change of pressure is sometimes too large to assure internal equilibrium of the reservoir gas. There is a plan to eliminate the first difficulty by adding an independent temperature sensor, and to alleviate the second by using a larger reservoir. Preliminary measurements, including comparison with results in the literature, will be presented. [Work supported by NSF.]
The relation between age of L2 learning (AOL) and degree of perceived global foreign accent
Authors: Flege James E. , Munro Murray J. , MacKay Ian R. A.
Published: October 2005

Degree of accent was assessed in five English sentences spoken by 243 Italians who immigrated to Canada between the ages of two and 22 years (an average of 12 Ss in each of 21 AOL subgroups). The Ss’ average age was 44 years (range: 25–56); their average length of residence in Canada was 31 years (range: 14–44). All Ss responded to a language-background questionnaire (LBQ) that provided information regarding age or arrival and length of residence in Canada, frequency of L1 and L2 use, self-estimated L1 and L2 pronunciation and comprehension abilities, strength of concern for pronunciation, imitation/musical ability, and motivation to learn English. The sentences were rated for degree of accent using our standard technique by ten native English Canadians. The results are presented of a multiple regression analyses relating the various LBQ variables to the foreign accent scores, and report on tests of two hypotheses: (1) foreign accents first emerge at an AOL of about 7 years; and (2) intra-subject and inter-subject variability in L2 pronunciation accuracy increases systematically as a function of AOL beyond the age at which foreign accents first emerge. [Work supported by NIH.]
Sonority contrasts dominate young infants’ vowel perception
Authors: Lacerda Francisco
Published: October 2005

Three groups of normal Swedish infants were tested on their ability to discriminate equal (in Bark) sonority (high/low) and chromacity (front/back) vowel contrasts. The infants were 2–3, 6–7, and 10–11 months old, living in monolingual Swedish environments. The 2–3 month olds were tested using the high-amplitude sucking technique. The older infants were tested with the head-turn procedure. One of the vowel pairs provided a [ɑ ]/[̂] sonority contrast, that was conveyed only by a 1.8-Bark difference in F1. The other pair was a [ɑ ]/[a] chromacity contrast, in which the vowels differed also by 1.8 Bark but in this case along F2. In spite of the procedural differences, the results show that the three groups of subjects could detect the sonority contrast but that no reliable discrimination could be inferred for the corresponding chromaticity contrast. [Work supported by The Bank of Sweden Tercentenary Foundation, Grant No. 90-0150.]
Do infants remember voices?
Authors: Jusczyk Peter W. , Hohne Elizabeth A. , Jusczyk Ann Marie , Redanz Nancy J.
Published: October 2005

Recent research on infants’ representation of speech typically focuses on linguistic features such as phonetic and prosodic cues. However, speech also carries information about things such as emotional tone and talker identity. To what extent do infants extract and remember such information from the speech signal? The present study asks whether infants preserve information about talker identity when they encode information from speech. Infants 7.5 to 8.25 months old were exposed to recordings of stories read by the same talker for 10 days in a 2-week time period. Two weeks later, the infants were tested in a head turn preference procedure. The stimuli were lists of words from the stories. Half of the lists were produced by the original talker; the other half by a novel talker. The infants listened significantly longer to the familiar voice suggesting that they developed a representation of that voice. An ongoing study is investigating whether infants actually listen longer to familiar words from the stories or to novel items of the same phonetic complexity and lexical frequency. [Work supported by NICHD.]
Holographic array processing in the presence of ambient noise
Authors: Al-Kurd Azmi A. , Porter Robert P.
Published: October 2005

A holographic array processing (HAP) algorithm is presented for source localization in a nonhomogeneous medium. Conventional array processing algorithms, such as matched field processing, require precise knowledge of the medium between the source and the receiving array. The holographic array processing method relaxes this stiff requirement and calibrates the integrated effect of the medium between a reference (virtual) array near the source, and the receiving array. Using conjugation and averaging techniques at the receiving array an image of the source wave front at the location of the virtual array is reconstructed without explicit knowledge of the characteristics of the medium. The target signal is measured at the receiving array while a reference source is deployed in the vicinity of the target and allowed to transmit at incremental depths. In this paper it is assumed that the ocean is to be horizontally stratified and range dependent. The target’s signal is observed at the receiving array in the presence of additive, spatially correlated ambient noise. In the reconstruction step the volume of the ocean in the vicinity of the target is scanned. Both the maximum likelihood method (MLM) and the conventional Bartlett processor are used to estimate the reconstructed field near the target by comparing the virtual image of the wave front with a weighting function that depends on the replica field from the test source. In a noise-free situation, the magnitude of the reconstructed field is greatest at the location of the target. The detection criterion of the noisy signal is based on maximizing the intensity of the reconstructed field as a function of range and depth.
Holographic array processing using truncated arrays
Authors: Al-Kurd Azmi A. , Porter Robert P.
Published: October 2005

Imperfect knowledge of the salient characteristics of the propagation medium limits the performance of acoustic array processors at long ranges in the ocean. Holographic and phase conjugation techniques can be used to diminish the range integrated effect of the medium and reconstruct the wave front in the vicinity of a scatterer or other signal source. Then, using a backpropagation technique, which focuses sound at the position of the unknown source, the location of the source can be determined. In deep water, the idealistic situation of having a receiving array and reference source that span the water column is prohibitively complex. In this paper the effect of truncating both the receiving and virtual arrays on the performance of the holographic array processing algorithm is presented. The analysis was carried out using normal mode theory, and the simulation for a range-dependent ocean was performed using a wide angle PE (parabolic equation) code, FEPE. It is shown that the holographic array processing algorithm is more sensitive to the length of the virtual array than to the length of the receiving array.
Broadband localization and deconvolution
Authors: Yang T. C.
Published: October 2005

An algorithm is presented for detecting and localizing a passive broadband signal in an underwater acoustic waveguide. The processor estimates the modal spectrum of a broadband signal for source localization; as a consequence, the source spectrum and signature (time domain waveform) are estimated. (Broadband modal decomposition is the equivalent of time domain deconvolution for source signature extraction.) In addition to the usual lofargram, a frequency-depth plot is proposed to display a broadband signal. Source localization is conducted in the frequency domain by summing the (range and depth) ambiguity functions over the signal bandwidth. Sidelobes are suppressed in broadband processing if the signal has sufficient bandwidth. Coherent summation of the ambiguity functions yields the expected time-bandwidth gain if source signature is known (the extended matched filter processing). Numerical simulations are shown for an Arctic waveguide. The processor works for transient as well as continuous broadband signals.
A normal-mode based approach for localization of transient signals
Authors: Jesus S. M.
Published: October 2005

Normal-mode modeling is a well-accepted representation for acoustic signals propagating in a number of environmental conditions. Detection of the spatial normal-mode structure makes possible signal localization enhancement against the noise that has no spatial structure. A simple algebraic argument allows one to separate the vector subspace that contains the signal from the vector subspace that contains the noise and to obtain a narrow-band estimate of the source location [S. M. Jesus, Signal Process. 28, 117–122 (1992)]. This subspace splitting algorithm has been extended for localizing broadband transient signals assuming that the signal only has a normal-mode structure. It is shown with synthetic data that the proposed broadband algorithm outperforms both the generalized minimum variance and the conventional processors. As an example, this processor has been used to localize short transient pulses collected in a 120-m depth shallow water area with a 62-m aperture vertical array. The experimental results show that stable and accurate localizations could be obtained during long time intervals. This shows that the sound field, received over a given frequency band, is relatively stable over time and is in agreement with the predictions given by a standard normal-mode propagation model.
Synthetic aperture processing of a moving cw sound source in a range-dependent underwater environment
Authors: Lawrence Thomas N. , Bedford Nancy R.
Published: October 2005

Synthetic aperture processing is a method of extracting horizontal wave numbers from recordings on one hydrophone. Such an approach has been previously suggested; most recently by Collins etal. [J. Acoust. Soc. Am. 92, 2366(A) (1992)], who proposed single hydrophone matched-field processing. A similar method was used by Frisk etal. [J. Acoust. Soc. Am. 86, 1928 (1989)] to derive bottom properties from data. The experimental method requires that a source (or receiver) move at a constant depth and a constant velocity with respect to a fixed receiver (or source). The moving source thus sweeps out a synthetic aperture with range, and array element recordings are processed by means of a Fourier transform of complex pressure with range, yielding the wave-number spectrum (or modal eigenvalues) over the chosen aperture. A series of overlapping apertures over the source track shows the evolution of the wave-number spectrum with the change in source–receiver range. Using a vertical array, estimations can be made for mode depth functions over the aperture of the array, mode attenuation, and mode eigenvalues with source range, i.e., those parameters needed for matched-field processing. Comparisons will be made to low-frequency acoustic data from a range-dependent environment. Experimental results will be compared with parameters obtained from an adiabatic normal mode model.
Sound-speed profiles from vertical array data
Authors: Berman David H.
Published: October 2005

Provided mode amplitudes are uncorrelated with one another, it is possible to extract sound-speed information from the covariance of the pressure field along a vertical array [D. H. Berman and S. N. Wolf, J. Acoust. Soc. Am. 91, 2447(A) (1992)]. Conditions under which modes are in fact uncorrelated will be discussed here. In addition, a method for correcting effects of array tilt will be presented. The main difficulty of the extraction scheme is that second derivatives of the covariance are required. Various attempts at smoothing data, including fitting the covariance matrix to Pekeris normal modes will be described. The method will be applied to covariance matrices assembled from data gathered near San Diego in 1985. [Work supported by U. S. Naval Research Laboratory.]