bluuebunny/crossref_metadata_2025 huggingface dataset:
A brief social history of active noise control in ducts
Authors: Eriksson L. J.
Published: July 2002

Considerable progess has been made in the applicaiton of active noise control in ducts since the pioneering work by Lueg over 60 years ago. These developments will be briefly reviewed with special emphasis on three remaining technical challenges including inadequate transducer output power and signal coherence at frequencies below about 50–100 Hz and high modal content at frequencies above about 500–1000 Hz. Although the potential for improvement remains significant, some problems may be approaching fundamental physical limits. However, widespread application may be more restricted by various social and commercial issues. Among these are the relatively low value that is often placed on noise control and energy savings, the lack of an adequate infrastructure to supply and maintain active noise control systems, and the cultural and business changes required to apply a technology that requires system design, easily demonstrates its performance, and often reveals the noise level of the source. Technological similarities between ANC systems and electronic security systems will be discussed. Social-cultural similarities between these systems and a weapon of warfare, the machine gun, will also be considered [John Ellis, The Social History of the Machine Gun (The Johns Hopkins University Press, Baltimore, 1975)].
Performance and maintenance requirements of active control systems
Authors: Bremigan Cary D.
Published: July 2002

Vehicle designers are continually looking for methods to improve in-cabin noise vibration and harshness (NVH). Active control systems offer a variety of techniques for low-frequency NVH control. Active systems allow the designer to trade between the factors of NVH performance, weight, package space, and cost. Examples of systems are active interior sound control and active-mounts/active-vibration control. The performance of these systems directly impacts the sound and vibration field, to which the operator and passengers are exposed. The system stability and robustness must be monitored and maintained at all times. The focus of this paper will be on active interior systems, highlighting performance and diagnostics. The closed loop control functions found in most active systems present unique opportunities for system maintenance and diagnostics. Several methods for component diagnostics will be discussed. Also, the diagnostic advantages of stand-alone and integrated active systems will be considered.
Simulated wave propagation in elastic environmental flat and sloping waveguides by a finite length ping time-dependent ray trace model
Authors: White Elmer
Published: July 2002

A finite length ping ray trace program (FLPRT) has been extended that is now capable of simulating time-dependent wave motion in a complicated elastic bathymetric waveguide. From the original concept of sound waves being generated from an infinite set of poiny sources, FLPRT expands a finite set into following ray theory including shear and compression logic in a half space. Wave propagation is demonstrated in a constant velocity shallow ocean environment for both flat and sloping bathymetries. Not only is the objective to compare the model-generated transmission loss calculations against those computed by EFEPE, an elastic parabolic equation model by M. Collins of ARL, but also to show the time-generated path of the acoustic waves in both cases. Narrow angle generated pings show different nonmodal characteristics than those generated by wide angle pulses which exhibit fluctuating waves predicted by normal-mode theory. As in all cases, adiabaticity is assumed within each very small incremental time step. A 3–5 min VCR(TV) presentation will be shown demonstrating wave motion in the presence of a flat and wedge half-space exhibiting both shear and compressional waves on the half-space.
Effects of simulated aircraft noise on the behavior and egg production of white leghorn chickens
Authors: Bowles Ann , Berg Erik , Abraham Natalie
Published: July 2002

White leghorn chicken poults (3 weeks and 8 weeks of age) and laying pullets (48 weeks of age) were exposed to a series of simulated jet aircraft overflights. Poultry were exposed in small groups (∼35 birds/pen) in barns equipped with a U. S. Air Force-designed simulation system. For poult experiments, 72 pens were exposed four to six times per day for 4 days. For experiments with laying hens, 60 pens were exposed four times per day for two 5-day blocks over a 2-week period. Level of exposure ranged from 105 dB ASEL down to the ambient noise floor in the barns. Ambient noise was dominated by poultry vocalizations and fan noise (70–85 dBA). Behavior, food and water consumption, mortality, weights (poults), and laying success (hens) were measured for each pen throughout the experiment. Neither poults nor hens responded to simulated overflights with panic flight, piling, or any other hazardous behavior, regardless of exposure level. However, 8-week-old poults picked at one another more often in the most highly exposed pens. Hens exhibited brief, small decreases in laying rate after initial exposure. Over the experimental period, the decrease was not significant. [Work supported by the U.S. Air Force, AL/OEBN, Wright–Patterson Air Force Base (F41624-95-C-6014 DO-C9).]
Comment on “Effects of aircraft overflights on wilderness recreationists” [J. Acoust. Soc. Am. 100, 2909–2918 (1996)]
Authors: Staples Susan L.
Published: July 2002

A psychologist outside the acoustics community considers the findings of Fidell et al. concerning the effects of aircraft overflights on wilderness recreationists [J. Acoust. Soc. Am. 100, 2009–2918 (1996)] in terms of other findings regarding visitor response to aircraft noise in wilderness areas and in light of current decision making about what actions are necessary to protect natural quiet in national parks. The limitations of a one-dimensional dose–response method that relies on annoyance as a global measure of the effect of park noise on visitors are discussed.
High resolution geoacoustic inversion using data from a towed broadband source and a bottom moored receiver
Authors: Holland Charles W. , Osler John
Published: July 2002

High resolution geoacoustic models are required for accurate predictions of acoustic propagation and reverberation in shallow water. Our measurement technique employs a towed broadband (400–8000 Hz) source towed near the surface and a moderately deep fixed receiver with source–receiver separations of 0–1000 m. Seafloor reflected data are first processed and inverted in the time domain to get an estimate of interval velocity in each sub-bottom layer. The data are then processed and modeled in the frequency domain to extract sediment layer densities, layer attenuations and velocity gradients. Direct path data are used to calibrate the source. The measurement and inversion technique has been applied at a number of shallow-water sites in the Mediterranean with diverse geo- acoustic properties. The frequency domain processing and modeling techniques will be discussed and the geoacoustic inversion results will be shown for several sites. Azimuthal variability of the geoacoustic models will also be discussed.
Shallow-water geoacoustic inversions of seafloor properties in Spencer Gulf
Authors: Deane Grant B. , Cato Douglas H. , Clarke Paul
Published: July 2002

Preliminary results of an experiment to characterize the geoacoustic properties of the upper few meters of the seafloor in Spencer Gulf, Southwestern Australia, will be presented. The aim of the experiment was to estimate the compressional and shear wave speeds, compressional wave absorption, and sediment density using different inversion techniques and compare the results for consistency. To this end, four measurement methodologies were used, which were: (1) transmission loss measurements, using the support vessel as a moving source, (2) ambient noise coherence measurements, (3) bottom reflectivity measurements, using frequency modulated pings and the sound of imploding light bulbs as sources, and (4) grab bottom samples. The transmission loss measurements show a distinct modal interference structure as a function of source frequency and source–receiver separation, and can be inverted for the average sediment acoustical properties along the source–receiver track. The ambient noise coherence measurements can be inverted for the noise field vertical directional density function, which in turn yields the critical angle of the seafloor averaged over a 5- to 10-km disk. [Work supported by DSTO, Australia, and ONR, USA.]
A new approach to the analysis of acoustic hole fibers
Authors: Üçer Mürvet , Akçakaya Ergül
Published: July 2002

In this work a new effective analysis method is proposed for the acoustic hole fibers of hexagonal crystal symmetry. Interpreting all quantities appearing in the boundary conditions as the state variables, a first-order differential equations system is obtained to investigate the waves in acoustic hole fibers of hexagonal symmetry. This approach makes it possible to analyze hole fibers by the general transmission-matrix technique. By using this method dispersion relations for all modes are easily obtained. This method can also be applied in the analysis of the multilayered cylindrical fiber for which the individual layers have hexagonal symmetric piezoelectric materials. [Work supported by İTÜ.]
Wavelet analysis as a wideband generalization of time-frequency analysis
Authors: Kaiser Gerald
Published: July 2002

The wavelet transform and the windowed Fourier transform are compared. Although these two look quite different in the time domain, they are very similar in the frequency domain. The only difference is that the windowed Fourier transform divides the frequency domain into bands of equal width, whereas the wavelet transform uses frequency bands of constant ratio. This is just how frequency bands occur in practice (in logarithmic rather than linear scale). Since low-frequency bands are narrow while high-frequency bands are wide in this scheme, the Nyquist sampling rates for low-frequency components of the signal are low while those for high-frequency components are high. The sampling rate in wavelet analysis is thus automatically adapted to the frequency range being analyzed. When both the signal and the analyzing wavelet are narrow band, it follows easily that the wavelet transform reduces to the windowed Fourier transform, the analyzing window for the latter being derived from the analyzing wavelet for the former. Therefore wavelet analysis may be viewed as a wideband generalization of ordinary time-frequency analysis, to which it reduces in the narrow-band limit. This view is especially useful in sonar.
Recursive parameter estimation methods: An adaptive filtering perspective
Authors: Douglas Scott
Published: July 2002

This tutorial provides an overview of recursive parameter estimation methods from the viewpoint of the adaptive filtering field. Specific topics to be discussed include gradient versus least-squares techniques, adaptive infinite-impulse response filters, and bias removal methods. Particular emphasis is placed on the analytical behaviors of the algorithms, their estimation characteristics, and their tracking abilities in mildly nonstationary environments. Applications of the methods to identification problems in acoustics are discussed. [This work has been supported by NSF Grant No. MIP-9501680.]
The effects of variability in ear canal geometry and middle ear impedance on noise exposure level
Authors: de Jonge Robert
Published: July 2002

If a group of industrial workers is uniformly exposed to a particular noise level, each person develops a different amount of hearing loss. The reasons for individual differences in susceptibility to noise are not entirely clear, but might relate, in part, to variability in ear canal acoustics and middle ear impedance. This variability alters the sound field to eardrum SPL transformation, effectively changing the magnitude of the exposure, and potentially producing differences in hearing loss. To study these effects, a computer simulation was created from an electrical analog model of the middle ear and a network representation of the ear canal. The model predicts how variation in ear canal geometry (length and diameter) and middle ear load impedance influences the eardrum SPL, both for individuals wearing hearing protector devices (‘‘leaky’’ earplugs) and for the unprotected ear. The model also estimates the amount of attenuation offered by the earplug and the amount of conductive hearing loss created by changes in the middle ear. Therefore, it was possible to evaluate whether changes in exposure levels would likely result in hearing loss, given the amount of protection offered by either earplug attenuation or conductive hearing loss.
Visualization of transient acoustic wave scattering from targets with thin shells
Authors: Crighton David G. , Vartiainen Markku J.
Published: July 2002

The objective of this work is to gain qualitative and quantitative understanding of acoustic wave scattering from thin shells. Near-field solutions for a pulse excitation are obtained and plotted in a time series. The visualization demonstrates development of transient edge scattering, at close range, of a target that incorporates thin shells and sharp edges. The demonstration is of wide interest and in that, the advantages of the adopted time domain formulation become apparent. Within the calculation technique, pressure difference across the shell has been obtained by the point collocation procedure, based on a boundary integral equation solution for thin shells. The near-field solution is solved from the pressure difference through the classical Helmholtz equation of retarded potentials. The transient scattered field on a plane has then been visualized with a general meshing program. Objects employed include a flat circular disc, a flat rectangular disc, an open cone, and a thin-walled cylinder. Some of the calculations have been verified by comparing the harmonic response, which has been obtained via Fourier deconvolution of the transient far-field transfer function, with existing analytical solutions or experimental results.
Backscattering enhancement from leaky Rayleigh waves on the flat end of a tilted solid cylinder: Observations and Gaussian beam model
Authors: Gipson Karen , Marston Philip L.
Published: July 2002

The circular end of a tilted solid cylinder in water was illuminated by high frequency sound. When the angle of incidence was close to the Rayleigh wave coupling angle, a leaky Rayleigh wave was launched which reflects from the rim. The reflected wave passes through a focus which lies on a diameter of the cylinder, and a significantly attenuated leaky wave subsequently reflects back along the diameter from the opposite rim. The radiation from the focused initial reflection was observed to produce a large backscattering enhancement having a far-field amplitude significantly greater than for reflection from a rigid sphere having the same diameter as the cylinder [K. Gipson, Ph.D. thesis, Wash. State Univ. (1998)]. This enhancement was modeled by approximating the leaky wave as a focused Gaussian beam and approximating the initial surface and far-field amplitudes using a variation of a method previously described [P. L. Marston, J. Acoust. Soc. Am. 102, 1628–1638 (1997)]. One of the principal curvatures of the outgoing wavefront vanishes so the enhancement is associated with a far-field caustic. The theory should be applicable to other flat circular targets. [Work supported by the Office of Naval Research.]
Meridional ray amplitudes for high-frequency backscattering from water-filled tilted finite cylindrical shells
Authors: Morse Scot F. , Marston Philip L.
Published: July 2002

Impulse response measurements have previously shown that the backscattering by moderately thick tilted finite cylindrical shells is enhanced when phase matching to a supersonic meridional leaky wave occurs [Morse et al., J. Acoust. Soc. Am. 103, 785–794 (1998)]. Above the coincidence frequency phase matching to the meridional a0 leaky Lamb wave occurs for a range of high tilt angles far from broadside incidence and yields large backscattering enhancements. The results of high-frequency tone burst measurements for water-filled shells are presented and compared with an approximate ray theory. In each case the peak backscattered amplitude for the initial meridional ray is several times larger than the reflection from a rigid sphere having the same radius as the cylinder. Amplitudes for the water-filled shell are generally less than one-half those for the corresponding hollow shell, but can still be understood using ray theory [P. L. Marston, J. Acoust. Soc. Am. 102, 358–369 (1997)]. Multiple internal reflections within the fluid cavity in the meridional plane give rise to regularly spaced enhancements in the time domain, some of which can be several times larger than the signal for the initial meridional ray. [Research sponsored by the Office of Naval Research.]
SEA modeling and analysis of stowage bin noise isolation and reduction
Authors: Li Jianyong , Serati Paul
Published: July 2002

The statistical energy analysis method is applied to the noise prediction and analysis of large passenger airplane stowage bin isolation. The purpose is to reduce the cabin noise generated from the external turbulent boundary layer and transmitted from the stowage bins via their supports. AutoSEATM is adopted for the modeling and analysis of the coupled structural-acoustic problem where the connection between the structural fuselage and the stowage bins is represented and implemented by a coupling loss factor (CLF). A significant amount of noise level reduction can be achieved by using elastomeric rod ends to replace the metallic rigid connection between the structural fuselage and the stowage bins. It is also possible to obtain a significant amount of weight reduction using the stowage bin isolators instead of the blanket applied to the cabin crown. Some analysis results have shown good agreement with flight test data. This modeling and analysis provides an effective way of reducing cabin noise for large commercial airplanes without any weight penalty. Economic gains will be obtained from both noise reduction and weight saving. [Support for this effort from B. Cimerman of Vibro-Acoustics Sciences, Inc. and Evan B. Davis of Boeing is gratefully acknowledged.]
Perception/production asymmetries in the acquisition of phonological categories
Authors: Hemphill Rachel
Published: July 2002

One assumption that has driven the development of phonological models is the idea that a single underlying representation (UR) exists in the mind such that talkers draw on it in both producing and perceiving speech. Data from a wide range of linguistic research suggest mismatches in phonetic and phonological abilities between perception and production which would be incompatible with the single UR model. The research reported here was specifically designed to test whether changes in perceptual categorization behavior would influence speech production abilities in a manner consistent with a single UR. Twenty native speakers of English were taught to categorically perceive a three way voicing contrast in synthetic bilabial stop consonants which varied only in VOT [after Pisoni, Alsin, Perey, and Hennessey, JEP: HPP 8(2), 297–314 (1982)]. Perception and production tests were administered following training. Subjects showed the ability, which improved with training, to categorically identify the three-way voicing contrast. Subsequent acoustic and perceptual analyses showed that they were unable to produce the contrast correctly, producing no difference, or manipulating acoustic variables other than VOT (vowel duration, vowel quality, nasalization). These results are explained in terms of separate expressive and receptive representations and the implications for perception/production mappings discussed.
Attentional effects of variability in phonetic context
Authors: Nusbaum Howard C. , Francis Alexander L.
Published: July 2002

Understanding how listeners cope with variability in the acoustic patterns of phonetic categories is a basic theoretical problem. Our previous research has suggested that talker and speaking rate variation slows phoneme recognition and increases cognitive load whereas amplitude variation does not. The present study examines the effect of varying phonetic context. Previous research has shown that varying phonetic context slows phoneme recognition. Using the same method as in our previous studies, we also found recognition slows when there is variation in phonetic context. In a second study, cognitive load was manipulated using a number recall task with lists varying in length. Consonant recognition performance was measured with a constant vowel context and when vowel context varied. Both conditions were tested with a low cognitive load and a high cognitive load. Our previous experiments demonstrated that talker and rate variability interact with cognitive load to slow phonetic recognition. The results of the present study will be compared with the results of prior work on talker and rate variabilty. The implications of these findings for the role of attention in theories of speech perception will be discussed.
An acoustic imaging system for the concurrent measurement of suspended sediment concentration and particle velocity
Authors: Adams A. E. , Hinton O. R. , Valentine E. M. , Tweedy A. D.
Published: July 2002

This paper presents work on a system providing concurrent concentration and two-dimensional (2-D) particle velocity measurements on suspended sediments in water. The paper shows how one-dimensional methods for independent measurement of sediment concentration and particle velocity can be combined and extended to provide the concurrent 2-D information. An experimental system is described in which suspensions of 0.5-mm diameter sand are illuminated by acoustic burst signals of 1-MHz frequency from two transducers. The relevant theory for determining sediment concentration and particle velocity is presented. The system geometry provides for the illumination of a 5-cm3 volume at ranges of up to 1.1 m, although longer ranges are possible. Results are presented for concurrent concentration and particle velocity measurements for a falling curtain of sediment, and these are shown to be consistent with predicted values. The measurements have sufficient resolution, and can be made sufficiently rapidly, to investigate short time-scale phenomena in hydraulics, such as the effect of wave dynamics on sediment transport. The method presented could form the basis of an instrument giving sequenced acoustic images of the transport phenomena occurring within an observed volume.
Direct and continuous measurement of depth-dependent reflection coefficients of Rayleigh waves for surface discontinuity: Normal slot
Authors: Kim Byoung-Geuk , Lee Sekyung , Enoki Manabu , Kishi Teruo
Published: July 2002

A new method and principle were presented for the continuous measurement of the depth-dependent reflection coefficient of Rayleigh waves or their pulse interacting with various surface discontinuities. The method was to record the reflection echo amplitudes for varying depth during scanning the Rayleigh wave pulse with a small lateral beam width along a surface discontinuity with a small slope in depth. In the experiments using a declined slot and intensively focused Rayleigh waves, the coefficients were continuously measured with quite good reproducibility in the range of 0.05<d/λ (slot-depth/Rayleigh wave wavelength) <2.57. In 0.05<d/λ<1.4, the results showed good agreement with other experimental results that had been determined by conventional method [L. J. Bond, Ultrasonics 71, 71–77 (1979); M. Hirao et al., J. Acoust. Soc. Am. 72, 602–606 (1982); H. M. Frost et al., Proc. Ultrason. Symp. IEEE (1975), 604–607] as intermittent point-to-point data and several numerical results [L. J. Bond, Ultrasonics 71, 71–77 (1979); R. J. Blake and L. J. Bond, ibid. 28, 214–228 (1990); M. Munasinhe, Ph.D. thesis, McGill University, Canada 1973; A. K. Mal and L. Knopoff, Bull. Seismol. Soc. Am. 55, 319–334 (1965)]. Especially, in the extremely shallow range of 0.05<d/λ<0.3, the reflection coefficients, showing quite good agreement with the numerical estimation, were measured while any other experimental data for slots or down steps have not been reported in 0.05<d/λ<0.25. It was shown that the new method could be used to evaluate more conveniently and quantitatively the depth or depth profile of various surface features in the long-wavelength or shallow-depth region of about 0.05<d/λ<0.5.
Response distributions in intensity resolution and speech discrimination
Authors: Schouten M. E. H. , van Hessen A. J.
Published: July 2002

In this paper the assumption of an equal, Gaussian distribution of the response to each stimulus in an experiment, an assumption which has to be met if d′ is to be estimated by calculating the difference between z(H) and z(FA), is tested for two different sets of stimuli: 1000-Hz tones differing in level only, and a continuum of stop consonants, obtained by full spectral interpolation between /p/, /t/, and /k/. Response distributions were measured directly by means of a form of non-numerical magnitude estimation, in which subjects had to indicate the position of each stimulus on a quasi-continuous rating scale. It could be shown that, in general, all distributions were sufficiently unimodal, but that their variances differed. The consequences for the calculation of d′ are unlikely to be serious.
A modified modal frequency spacing method for coating characterization
Authors: Wang Z. , Li X. , Cheeke J. David N.
Published: July 2002

A modified modal frequency spacing (MMFS) method is developed, which can be used to directly evaluate the coating density ρc and the longitudinal velocities of the substrate and of the coating, VLS and VLc, based on the measured cutoff frequency data. Numerical simulation results showed that the error in evaluating VLS and VLc is less than 0.4% and is less than 4% in ρc compared with the input data.
Sound exposure level of railway bridge noise
Authors: Makarewicz Rufin , Koga Jun-ichi
Published: July 2002

A train is considered to be a homogeneous line source; therefore, the concept of the linear density of the A-weighted sound power, WA, is used. The process of noise generation on a bridge is characterized by the product, α⋅WA, and that beyond a bridge by β⋅WA, where α≫β. Geometrical spreading is considered to be the only wave phenomena that governs noise propagation. The theory presented here requires measurements at two locations in the vicinity of the bridge in question and makes possible the calculation of the sound exposure level, LAE. The obtained experimental values are consistent with the theoretical values.
Profiling the perceptual suppression of partials in periodic complex tones: Further evidence for a harmonic template
Authors: Brunstrom Jeffrey M. , Roberts Brian
Published: July 2002

The basis for the perceptual cohesion of periodic complex tones was investigated. In experiment 1, 2–4 consecutive components (harmonics 6 and above) were removed from a 14-harmonic complex and replaced with a sinusoidal “probe,” located at one of a set of regularly spaced positions spanning the gap. On each trial, subjects heard a complex tone followed by an adjustable pure tone in a continuous loop. Subjects were better able to match the pure tone to the probe when the probe did not coincide with a harmonic position. Minima in “hit rate” were more pronounced when harmonic probes were in positions adjacent to other harmonics than when they were not. These findings suggest that the pitch of each in-tune partial was actively suppressed by a template whose influence attenuated with distance from regions of consecutive harmonics. In experiment 2, the partials on either side of the spectral gap were harmonics of different fundamental frequencies. Hit-rate minima corresponding to both fundamentals were found, indicating an upward and downward spread of suppression, and also demonstrating the concurrent operation of two templates. The results confirm recent findings in support of template models, and are consistent with the idea that partial-pitch suppression underpins harmonic fusion.
Wave decomposition of the vibrations of a cylindrical shell with an automated scanning laser vibrometer
Authors: Kil Hyun-Gwon , Jarzynski Jacek , Berthelot Yves H.
Published: July 2002

Elastic waves propagating in a cylindrical shell have been detected by an automated scanning laser vibrometer designed to record both in-plane and out-of-plane surface motion over the surface of the shell (32 points axially and 32 points circumferentially). The structure was freely suspended in air and excited radially by a shaker at a single frequency, either below or above the ring frequency of the shell. A wave vector analysis of the data was performed with a fast Fourier transform and an overdetermined modified extended Prony method. The results clearly show the presence of longitudinal, shear, and flexural waves above the ring frequency. In addition, the Prony method reveals the presence of evanescent waves due to mode conversion of the propagating waves near the ends of the shell. Below the ring frequency, two types of in-plane waves and flexural waves were identified. The results are in excellent agreement with predictions from the dispersion curves for thin shells.
High-frequency acoustic waves reflection on seafloor
Authors: Drevet Claire , Sessarego Jean-Pierre , Brussieux Marc
Published: July 2002

The purpose of this research is to study the acoustic waves reflection on seafloor in very shallow water in the frequency range 200–700 kHz. Effectively previous operations of detection of proud objects using sonar imagery showed problems in this environmental context caused by a superficially modified sediment structure and an insonification closed to ‘‘critical angle.’’ A study has been done with experimental data collected in a tank (at scale ‘‘one’’) on calibrated sand. This approach eases control of a lot of acoustical and geophysical parameters. Mono- and bistatic scattering measurements are recorded. Temporal broadband signals are analyzed by Fourier transforms. Results are compared with various theories. It especially emphasizes the Biot propagation model and a composite roughness model. The input sediment structure parameters are debated with discussion about their influence on seafloor reflection. Concerning the nontotal internal reflection below critical angle, the debate is not yet closed and expected additional data experiments on acoustic wave field inside the sediment itself would allow us to understand the mechanism of acoustic waves propagation in very shallow water and extract better models fitting experimental results.
A concept for remote acoustic monitoring of solitons generated in straits
Authors: Chin-Bing Stanley A. , King David B. , Warn Varnas Alex , Zingarelli Robert A.
Published: July 2002

A search algorithm for resonance anomalies (SARA) has been developed to predict possible resonance frequencies of shallow-water soliton packets as they travel through straits. The algorithm relies on characteristics that accompany large losses due to acoustic wave-soliton interactions: (a) acoustic mode conversions; (b) large signal losses within a narrow band of acoustic frequencies; and, (c) large transmission losses due to strong couplings between lower-order propagation modes and higher-order, bottom-interacting modes. The SARA algorithm has been verified using oceanographic data from the Strait of Messina. As a remote acoustic sensor, the SARA algorithm could be used in an ‘‘inverse mode’’ to predict key oceanographic parameters (e.g., predominant horizontal spatial wave numbers and travel speeds) of those soliton packets that produce large acoustic losses. The parameters would initialize a primitive shallow-water soliton model that generates soliton simulations. The SARA algorithm could be used in a forward fashion to validate the soliton simulations. The concept exploits the unique sloping bathymetry of straits, where natural mode stripping can occur around the sills that generate the solitons. Details will be discussed and computer simulations will be presented that illustrate the feasibility of the approach. [Work supported by ONR/NRL and by a High Performance Computing DoD grant.]
Acoustical studies on steel pans: the role of the skirt
Authors: Hansen Uwe J. , Rossing Thomas D.
Published: July 2002

Previous studies [Rossing et al., Phys. Today 49(3), 24–29 (1996)] showed that skirt vibration amplitudes were about 20–40 dB less than amplitudes of the struck note area, and therefore the skirt contributes in a minor way to the total sound level. Nevertheless, the skirt has many resonances of its own and contributes to the timbre of the played instrument, as can be easily heard by damping the skirt. Using electronic TV holography, modes of vibration of steel pan skirts have been recorded when the note area is driven sinusoidally at various frequencies and amplitudes. The modes have varying numbers of nodal meridians and nodal circles, much like those observed in bells and especially in drum shells [Rossing et al., J. Acoust. Soc. Am. 92, 84–94 (1992)]. Effects of the skirt modes on the sound spectra of the steel pan are discussed. a)On leave from Indiana State University, Terre Haute, IN.
Arching and rib height in the 2DOF network model of violin cavity resonances
Authors: Bissinger George
Published: July 2002

The 2DOF network model of violin cavity A0 and A1 resonances [E. A. G. Shaw, J. Acoust. Soc. Am. 87, 398–410 (1990)] has been augmented by explicitly incorporating arching and rib height as parameters. Arching was simulated with 26 scaled wedge, block, corner and truncated-corner volumes; rib height was incorporated after accurately determining the cross-sectional area in the plane of the cavity. Optimized f-hole inertances, C-bout inertance length, partial volumes, and division parameters [G. Bissinger, J. Acoust. Soc. Am. 101, 3144 (1997)] were used for all calculations. Calculated A0 and A1 mode frequencies and upper bout/lower bout pressure ratios all decrease with increasing rib height or arching with the notable exception of A1 frequencies, which increase with increased arching.
Vibroacoustic properties of a composite harp soundboard
Authors: Preissner Curt , Royston Thomas J.
Published: July 2002

The concert harp has survived through the years much as it was in the 18th century; the construction is still labor intensive, the performance variable, and the durability questionable. These problems can be attributed to the most important part of the harp, the soundboard. Harp soundboards are constructed of spruce wood, which is adversely affected by time, temperature, humidity, and handling. An investigation is underway to replace this fragile sitka spruce soundboard with a more durable material while maintaining acceptable sound quality. The soundboard, a sitka spruce laminate, is already anisotropic; thus, it lends itself to replacement by a carbon fiber reinforced plastic (FRP) laminate. Experimental modal analysis was used to determine vibratory properties of two harp soundboards and uniform spruce beams. Finite element models (FEMs) of the spruce soundboard and beams were developed. The beam FEM aided in the application of laminate theory to determine the lamina stacking sequence to construct a similar composite beam. After experimental verification of the FRP beam, this understanding was applied to construct a FEM of the fiber soundboard. Techniques used to develop and analyze the FRP harp soundboard will be presented.
The auditory effects of a deployment—An individual’s experience
Authors: Garman Janet C.
Published: July 2002

Cases of hyperacusis and tinnitus have been reported after the sudden, loud noise blast and instantaneous air pressure rise of airbag deployment. This presents a serious problem as hyperacusis is a disabling and devastating disorder in which everyday noises are painfully loud. The ears also lose their dynamic range. Hyperacusis drastically alters one’s life. It may end careers, place enormous stress on personal relationships, severely limit social and athletic activities and interfere with communication. Hyperacusis sufferers often cannot attend family gatherings, movies, parties, sports events, weddings, and places of worship even using hearing protection. Many cannot use household appliances or power tools. Traveling is difficult. They walk a thin line between overprotection and underprotection. Overprotection causes their hearing to become even more sensitive and underprotection can exacerbate the accompanying tinnitus and worsen the hyperacusis. This paper presents the author’s experience with all of the aforementioned issues and how as a result, her life has changed. The question arises whether one should be required by law to place their auditory system in such jeopardy from an airbag which by its own name, supplemental restraint system, concedes it is only an additional safety device with the seat belt being the main form of protection.
Bubble-based pump for small channels
Authors: Yuan H. , Prosperetti Andrea
Published: July 2002

In the small liquid handling devices that the new silicon manufacturing technologies render possible the problem arises of pumping the liquid through small channels. In this study the possibility of using vapor bubbles generated thermally at suitably spaced time intervals for this purpose is explored theoretically. In the current version of the model the bubbles are one-dimensional ‘‘slices’’ of vapor in which a prescribed law of variation of the internal pressure with time is prescribed. This represents a simplified model of the switching on and off of microheaters embedded in the channel walls. When the thickness of the bubble falls below a certain value, the bubble is removed and that portion of the channel available for flow. It is shown that, with a suitable timing of the application of heat, a net pumping flow can be generated. The effects of liquid viscosity and surface tension are also included in the model and shown to be important in determining the pumping action. Some initial results in which the bubbles are modeled as spheres will also be presented. [Work supported by the Air Force Office of Scientific Research.]
A study of optoacoustics at the vaporization threshold of liquid carbon disulfide
Authors: Cheyne Stanley A. , Long John M.
Published: July 2002

An optoacoustic technique was used to investigate the vaporization mechanism in liquid carbon disulfide. The amplitude of the acoustic signal varied linearly up to the boiling point where, at that point, the slope of the amplitude versus laser energy curve increased, indicating an increase in optoacoustic conversion efficiency. It was observed that vapor bubbles did not appear until well after the boiling point of the liquid. After achieving the boiling temperature, the propagation time of the acoustic signal increased with a maximum delay of 255 ns. This maximum correlated with the formation of a vapor bubble, suggesting that the delay was possibly due to the acoustic wave propagating in a gaseous medium within the excitation zone where the sound speed was slower.
Localization of sounds presented over headphones in ambient noise
Authors: Ericson Mark A. , Bolia Robert S. , Nelson W. Todd
Published: July 2002

Sounds produced in everyday environments often interfere with other sounds. In aerospace and industrial environments the interfering sounds are typically diffuse and mask the desired sound. Relatively few studies have addressed the effects of noisy environments on auditory localization perception. Most localization experiments use stimuli presented in the free field, without maskers or with one directional masker. A few studies [Hirsh, J. Acoust. Soc. Am. 22, 196–200 (1950); Mershon and Lin, Ergonomics 30, 1161–1173 (1987)] have measured auditory localization perception in reverberant environments. However, in these studies both the signal and maskers were produced in the reverberant environment. With virtual audio systems becoming widely available, many applications will likely involve listening to directional sounds over headphones while immersed in a high-intensity diffuse noise field. The current study examines the effect of bandlimiting various frequency regions of a directional noise signal presented over headphones in the presence of ambient noise. The four signal regions include: (1) 0.1 to 1 kHz; (2) 1 to 4 kHz; (3) 4 to 8 kHz; (4) 8 to 16 kHz. Results from this study have implications for the design of directional audio displays in high-noise environments.
Optimal transducer placement for active control of sound transmission through an aeroelastic plate
Authors: Smith G. Clark , Clark Robert L.
Published: July 2002

The optimal locations of colocated transducers for static and dynamic output feedback control of sound transmission through an aeroelastic plate are investigated. The model of a convected fluid loaded plate coupled to a cavity is presented. The physical dimensions and parameters of the model are chosen to approximate a small commercial aircraft. Development of two optimization approaches is discussed in detail. The first method uses the Sequential Quadratic Programming nonlinear optimization algorithm to minimize the H2 Norm of the complete system from the disturbance inputs to a weighted sum of cavity acoustic potential energy and feedback control signal energy. The second method utilizes a simple line search routine to maximize a measure of system controllability. Case studies optimizing a control system with one and three sensoriactuator transducers are presented for external flow speeds varying from Mach 0.1 to Mach 1.1. Results show the variation in optimum transducer placement for both the static and dynamic control systems over the range of flow speeds considered. A comparison of the optimal placement determined by each optimization approach is also given. [Work suported by NSF Career Program CMS-9501470.]
The role of grazing waves in sound transmission through a finite plate
Authors: Masyukov Valerij A.
Published: July 2002

Air sound transmission loss (TL) of a finite elastic plate, placed in an infinite rigid baffle, is computed with regard to, first, a lack of near-grazing waves in incident sound field and, second, diffractive three-dimensional expansion of the sound field radiated by forced bending waves of the finite plate. It is shown that both effects lead to the lack of near-grazing sound waves in transmitted sound field what in turn appreciably increases TL compared with diffuse field and infinite plate. Below coincidence, especially at low frequences, the second effect usually predominates over the first. At coincidence, in contrast, the first effect always prevails and results in an increase of both TL and limiting frequency. Above coincidence, both effects are always negligible. The computations are compared with numerous measurements of various authors for glass panels of different dimensions and satisfactorily explain the well-known excess of experimental TL values over infinite-plate theory at and below coincidence. Nevertheless the familiar integration formula for infinite plate may be successfully used for finite panels with the only difference that the limiting integration angle of incidence becomes depending on acoustic wave number.
The influence of acoustic and semantic information on phoneme categorization in sentences
Authors: Borsky Susan , Shapiro Lewis P. , Tuller Betty , Langford Christina G. , Faber C. Sue , Wolf Kellie A.
Published: July 2002

In spoken language, local acoustic information is frequently consistent with more than one phoneme. This study investigates the influence of acoustic and semantic information on phoneme categorization as a sentence unfolds in time. Ten target stimuli forming a Goat-to-Coat continuum were created from natural speech by manipulating the voice onset time of the initial consonant. These stimuli were embedded in biased sentences such as: Goat-biased: The busy dairyman forgot to milk the (Goat/Coat) in the drafty barn. Coat-biased: The careful tailor hurried to press the (Goat/Coat) in the cluttered attic. A cross-modal interference task showed immediate effects of acoustic information; effects of semantic information appeared 450 ms later. A cross-modal identification task showed immediate sentence context effects for ambiguous mid-range stimuli while identifications 450 ms later showed context effects for endpoint stimuli. A word monitoring study showed immediate context effects throughout the acoustic parameter range. These data support an account of auditory sentence comprehension in which semantic information does not immediately and automatically influence phonological analysis of an acoustic signal; contextual influences occur over time or when a task or situation requires explicit judgment about the identity of a stimulus. [Work supported by NIMH, Grant No. MH42900, and NIH, Grant No. DC00494.]
Acoustic characteristics of American English vowels produced by Floridian female speakers
Authors: Bielec Katherine C. , Grainger Amanda D. , Strange Winifred , Trent Sonja A. , Nishi Kanae
Published: July 2002

The present study analyzed the temporal, spectral, and dynamic acoustic characteristics of 11 American English (AE) vowels /i, ɪ, e, ε, æ, ʌ, ɑ, ɔ, o, ᴜ, u/. The stimuli were produced by 22 monolingual female adult speakers from Florida. The vowels were embedded within the hVd consonantal context in a carrier phrase. Acoustic measurements included vowel duration, fundamental frequency, temporal midpoint and dynamic information. LPC formant contours were measured by the 25%, 50%, and 75% points of the vocalic nuclei. A perceptual vowel identification task was included in the study. Twenty Floridian female adult listeners categorized the 253 vowel stimuli using an interactive, self-paced computer program. Results of acoustic vowel space, spectral movement, discriminant function analysis, and perceptual identification will be presented. [Work supported by NIDCD.]
Acoustic correlates of articulatory prosodic strengthening in Korean
Authors: Cho Taehong
Published: July 2002

Recent articulatory studies [e.g., Keating, Cho, Fougeron, and Hsu (1998), forthcoming] using electropalatography have shown that consonants are generally produced with greater linguopalatal contact in domain-initial positions. This effect, known as articulatory prosodic strengthening, is generally cumulative: the higher the prosodic position, the more linguopalatal contact. The goal of this paper is to test for acoustic correlates of any such articulatory variations in Korean consonants /n,t,th,t*/ in prosodic positions (Utterance-, IP-, AP-, Word- and Syllable-initial), so that eventually the perceptual significance of such correlates can be tested. Results show that the higher domain-initial positions are associated with longer VOTs; longer ‘‘total’’ voiceless duration in closure; lower rms burst energy in stops but with substantial inter-speaker/consonantal variations; lower % of voicing during closure; and lower acoustic energy for nasal /n/. In addition, vowels in domain-initial CV were not found to be necessarily longer in a higher position whereas vowels in domain-final positions were. Linear correlations between each of the acoustic parameters and the articulatory magnitude (linguopalatal contact) will also be discussed. All in all, this study shows that articulatory strengthening in Korean does produce reliable acoustic correlates, which mark off prosodic positions in the speech signal. [Work supported by NSF.]