bluuebunny/crossref_metadata_2025 huggingface dataset:
Spectro-temporal influence on auditory cortical evoked potential thresholds
Authors: Eddins Ann Clock
Published: July 2002

Previous studies from our laboratory have shown that auditory cortical evoked potential thresholds (N1-P2) decrease with increasing stimulus duration. Similar to behavioral studies of auditory temporal integration, N1-P2 threshold improvement was greater for 1000-Hz than 4000-Hz stimuli. It is unclear whether spectral splatter at short durations contributed to the threshold differences across frequency. The present study investigated spectro-temporal influence on N1-P2 thresholds by manipulating the stimulus rise–fall time, total duration, and stimulus type. Thresholds were estimated in three temporal conditions to compare stimuli with equal rise–fall (2 ms) but different total durations (8, 36 ms), and stimuli with different rise–fall (2, 16 ms) but equal total durations (36 ms). Broadband noise bursts and 1000-Hz tones were used to test each temporal condition. Preliminary results show that thresholds for both noise and tonal stimuli decrease with increasing total duration. No significant differences in threshold were observed as a function of rise–fall time nor were significant differences observed as a function of the stimulus type. The results suggest that N1-P2 thresholds are determined primarily by changes in total duration and that thresholds for short durations at 1000 Hz are not adversely affected by spectral splatter. [Work supported by NSF.]
Contribution to the study of the audiometrical scores sources of 20 variation
Authors: Bruyninckx Marielle , Hamache Saefda , Harmegnies Bernard
Published: July 2002

This paper summarizes the development and the presentation of a discrimination test of the relative height of two pure sounds. Sixty pairs of sounds have been presented to 68 subjects. The elaboration of these pairs was based on a selection of ten initial stimuli that were paired according to three different intervals: octave, 1/3 octave, and 11/24 octave. These stimuli were then presented by pairs to the subjects in a random way, according to an ascending or a descending sequential structure. The aim of this work is to test: whether the paired sounds’ presentation order (ascending or descending) has, or has not, an effect on the subjects’ results; whether the kind of frequential interval is a determining factor in the subjects’ discriminatory abilities; whether the musical education plays a role on performances (in comparing musicians’ and nonmusicians’ performances). Together with measurement of reliability, the results show that: it is easier to discriminate sounds in an ascending structure, whatever the frequential intervals may be; there is no significant difference between 1/3 octave, octave, or 11/24 octave intervals; the musicians present better discriminatory abilities than the nonmusicians concerning the ascending structure pairs, but worse abilities when the structure of the pairs is descending.
Hawkins and Stevens revisited at low frequencies
Authors: Houtsma Adrianus J. M.
Published: July 2002

The classical data on masking of pure tones by white noise [J. E. Hawkins, Jr. and S. S. Stevens, J. Acoust. Soc. Am. 22, 6–13 (1950)] yield a nonmonotonic critical ratio function that increases at low and at high frequencies. Modern bandwidth estimates of auditory filters, however, yield equivalent rectangular bandwidth (ERB) functions that are monotonic with frequency. This apparent discrepancy has sometimes been interpreted as evidence for frequency-dependent detection efficiency in the auditory system. Another possible reason for the discrepancy, however, could be the fact that the classical data were measured with headphones that needed substantial correction at low frequencies to compensate for acoustic leakage. To test this, the Hawkins and Stevens experiment was repeated with Etymotic ER-2 insert phones over a frequency range from 30 to 8000 Hz. An adaptive forced choice, as well as a Bekesy tracking procedure, was used. The resulting critical ratio function shows monotonic dependence on frequency, down to 90 Hz, similar to the ERB function. This appears to make critical ratio data, in principle, consistent with ERB data measured with notched-noise techniques, and largely eliminates the need for a frequency-dependent detection efficiency in the auditory system.
Brake-noise challenge in the automobile industry
Authors: Chen Shih-Emn , Her Jen-Yuan
Published: July 2002

Brake noises generated during vehicle operation are caused by nonlinear structural behavior that is difficult to model analytically. Noises, predominantly contact related, falling in this group can be classified into two categories based on the frequencies at which they occur: (1) brake squeal in kHz ranges; (2) brake moan and groan in 100–300 Hz range. These noises may often be accompanied by structural instability caused by some, if not all, of the following phenomena: (1) lining deformation; (2) negative slope in friction-velocity characteristic; and (3) stick-slip. In addition to the aforementioned phenomena, coupled resonance of brake components is also a necessary condition of the brake-noise generation. Currently, vehicle brake-noise design prevention is still based on a trial and error basis. No reliable design prevention tool is yet established. Although computer simulations were sometimes used to predict the structural instabilities, no clear understanding of the link between structural instabilities and radiated noise has been established. The major challenge to automobile noise control engineers will be to establish a noise radiation model which could identify the influence of the key design parameters on the noise level.
Limit cycle dynamics in prosody
Authors: Cummins Fred
Published: July 2002

Compared to music, juggling, dancing, etc., speech may seem to be only weakly rhythmic. New experimental evidence suggests, however, that rhythmic constraints on the timing of certain speech events can be quite strong. This is particularly clear when subjects repeat a phrase in time with a periodic stimulus. Mode locking, mode switching, and hysteresis have all been documented, thus showing hallmarks of the hierarchical entrainment among two periodic cycles. These cycles are coextensive with independently motivated prosodic units, the foot (or prosodic word), and the intonational phrase. It appears that this repetition task induces a second-order limit cycle dynamic in each of these units. [Work supported by the Indiana University Graduate School and the Andrew W. Mellon Foundation.]
Comparisons of simultaneous signal reception over long range among hydrophones with unlike acoustic geometries
Authors: Walkinshaw H. M.
Published: July 2002

Propagation measurements were made to six hydrophones installed offshore Bermuda at depths from 430 to 2450 fm. Four were bottomed onslope or at basin depth; two were suspended, one at the sound channel axis and one 30 m above the deep bottom. Both impulse sources (charges detonated at 18 and 240 m) and a continuous wave (cw) transducer towed at 120 m were used. The 800-nm track began 40-nm south of Bermuda at midpoint of the ensemble of hydrophones and ended off St. Thomas beyond the Puerto Rican Trench. The bottom receiver at 430 fm had the lowest transmission loss; the deep basin hydrophone the highest. Arrival order identification from shot processing for all hydrophones showed performance depended on the degree to which the local bottom slope enabled a receiver to intercept both up and downcoming ray paths. Suspension per se was not significant. Energy partition among arrival orders indicated one arrival carried about 50% of received signal strength. About five arrivals were needed before 90% of the total signal was collected, suggesting broad ocean coverage is unavoidably linked to coping effectively with multipath propagation. [Work supported by NavElecs.]
Numerical model for low-frequency sound propagation in inhomogeneous waveguides
Authors: Voronovich Alexander G.
Published: July 2002

Sound propagation in a shallow-water environment can result in the appearance of steep enough rays. Sufficiently accurate treatment of such situations with the help of the parabolic equation (PE) method can be complicated. On the other hand, propagation of low-frequency sound in inhomogeneous waveguides can be conveniently considered in terms of local modes. An algorithm for sound field calculation in the inhomogeneous waveguides was suggested recently [A. Voronovich, J. Comp. Acoust. 4, 399–423 (1996)]. This algorithm is not based on parabolic approximation, it includes backpropagating field, and for 2-D situations is principally exact. Similar to the PE method it is also based on ‘‘marching,’’ however, in this case it proceeds in the backward direction. In contrast to other exact approaches which invoke piecewise constant (‘‘staircase’’) approximation of the inhomogeneous waveguide, this algorithm takes into account the mode interaction within each horizontal step. This allows one to increase the value of the horizontal step significantly making the algorithm very efficient. Generalization of this algorithm for the case of the uneven liquid bottom is considered. It is shown that due to sharp discontinuities at the bottom a bigger number of modes should be taken into account for sufficiently accurate calculations of the field in this case.
Estimation of far-field pressures from geometric near-field measurements
Authors: DiPerna Daniel T. , Corrado Charles N. , Warwick David C.
Published: July 2002

Measurements of radiated noise are often made in the geometric near field of a cylindrical radiator to take advantage of high signal-to-noise ratios. At these ranges the far-field beam patterns are not fully established and the corresponding sound pressure levels cannot be determined via a simple range correction. In this paper, three methods of estimating the far field given measurements primarily made in a horizontal plane are presented. All three methods employ propagator matrices to relate surface field quantities to the near- and far-field pressures. The pressures measured over a segment of the receive array are multiplied by a weighting vector determined from the propagator matrices to minimize the mean square error between the actual and estimated far field. One method represents the surface field as a distribution of monopole sources of unknown strength. This method also employs an image source field representation to attenuate surface bounce contributions. The second method represents the surface field in terms of cylindrical harmonics with unknown modal coefficients employed at discretized axial positions along the cylinder. The third method is formulated using unknown modal coefficients derived from a substitution of the spherical harmonic expression of the free-space Green’s function in the Helmholtz integral equation.
Robust Kalman-based time-varying DOA estimation of impulsive noise
Authors: Kim Han-Su , Sung Koeng-Mo
Published: July 2002

This paper presents the robust Kalman-based method which is modified with a Huber function for estimating time-varying DOA (direction of arrival) under an impulsive noise environment. The Kalman-based algorithm can estimate the proper parameter in the additive white Gaussian noise. But it is well known that the performance of the Kalman algorithm degrades seriously when the input or the estimation error contain impulsive noise (burst outliers) which can arise frequently in many practical applications. The proposed algorithm has the robustness over the impulsive noise by putting bounds to the derivative of its cost function with respect to the estimation error, using Huber function. It is known in the theory of robust estimation that if the influence function is bounded, the estimator is robust. Simulations show that the performance of the proposed algorithm is less vulnerable to the impulsive noise than the conventional Kalman algorithm.
High-frequency acoustic scattering from thermally generated turbulence
Authors: Oeschger John
Published: July 2002

The results of a laboratory experiment are presented for the case of high-frequency broadband multistatic acoustic scatter from a thermally generated buoyant plume. The dominant scattering mechanism is changes in the relative compressibility, which is related to the temperature difference from ambient. Far-field weak scattering theory is used to describe the scattering process. This results in a simple relationship between the complex acoustic scatter and the one-component, three-dimensional Fourier transform of the temperature field measured at the scattering producing Fourier component K, defined as the Bragg wave number. This wave number is the magnitude of the difference wave vector between the scattered and incident wave vectors. Theory predicts for measurements made in the same scattering direction that spectral estimates for overlapping Bragg wave numbers be identical. Utilizing data collected from simultaneous multiple bistatic configurations with parallel Bragg wave vectors yields a more fully resolved spectral estimate of the scattering producing temperature field. A time series of the spectral estimate of the turbulent temperature field is shown for a three-channel bistatic common Bragg direction measurement. The results indicate agreement between the spectral estimates in the regions of overlapping Bragg wave numbers, validating the theoretical description. The time series also shows strong, yet highly variable nulls in the wave-number spectrum of the turbulence. [Work supported by ONR.]
Target size measurements via specular echo spectrum
Authors: Mathieu Jerome , Schweitzer Patrick , Tisserand Etienne , Weber Serge , Gauthier Serge
Published: July 2002

Ultrasound principles actually used to determine experimentally the size A of solid targets are based on measurement of scattering attenuation. The principal limit of this method comes from the difficulties in identifying excess attenuation due to scattering. This paper presents a new method to determine the size A of a target by means of specular echo spectrum. When an immerged (in water) target is insonified with a very brief ultrasound pulse, the backscattered echo contains two parts temporally distinguishable. The first part is the specular echo. The specular echo target spectrum St depends on the form function F and A, but also of the measuring chain response. So this method includes a gauging step which consist to calculate the spectrum Sb of a block’s echo. It is also showed that Sb/St (which is noted Fmes) is proportional to F in the bandwidth measuring chain B. The comparison of Fmes and F gives the bandwidth B in terms of KA, where K is a known wave number. Thus A is deduced by comparing Fmes and F. The most interesting advantage of this method is its independence towards attenuation. Some results are presented.
Turbidity in future high-frequency sonar performance models
Authors: Richards Simon D. , Brown Niven R. , Leighton Timothy G.
Published: July 2002

Current sonar performance models are incapable of accurately predicting the performance of high-frequency sonars in highly variable turbid coastal waters. There is therefore a requirement for improved models incorporating the additional effects in such environments. Turbid coastal waters are characterized by relatively high levels of suspended particulate matter, the presence of which leads to increased attenuation through viscous absorption and scattering, leading to a significant reduction in the detection range of high-frequency active sonars at moderate concentrations. The additional attenuation mechanisms have been incorporated into a propagation-loss model and the effect on detection range has been investigated. The additional attenuation processes are influenced by the ambient temperature, pressure, and salinity, and the effects of these parameters on the total attenuation in seawater containing suspended mineral particles has also been investigated. The results presented demonstrate that the effects of suspended particulate matter should be included in future high-frequency sonar performance prediction models in turbid environments. Temperature is found to be an important factor influencing the attenuation, and the local temperature should therefore be used in performance calculations. [Published with the permission of the Controller of Her Britannic Majesty’s Stationery Office.]
Experimental verification of the deformed cylinder scattering model and its application for the calculation of backscattering from fish
Authors: Sawada Kouichi , Ye Zhen , Furusawa Masahiko
Published: July 2002

The dorsal aspect target strength pattern of straight cylinders made of polystyrene (EPS) are measured and compared with the deformed cylinder scattering model (DCM) proposed by Ye [Zhen Ye, J. Acoust. Soc. Am. 102, 877–884 (1997)] in the range of the tilt angle from −50° to 50°. Both experiments and the theory agreed very well for the wide range of tilt angle. The deformed cylinder model is also applied to predict the target strength pattern of Ayu (Plecoglossus altivelis) which is a river fish with an open swimbladder. The dorsal target strength of Ayu is measured by keeping it in alive condition. Then its swimbladder’s shape is observed using a soft x-ray system and digitized. Digitized data is used for the calculation on the basis of the deformed cylinder model and also the shape of the swimbladder is reproduced carving a rectangular solid of EPS by hand. The measured TS pattern of alive Ayu, the physical EPS model of swimbladder, and the DCM calculation agreed very well. Expanded polystyrene is a useful material to verify the scattering theory of the gas model and can become an artificial fish model with a swimbladder. Scattering from a complicated shape as a fish is predictable using DCM.
New experimental characterization of a resonance: Identification of the mode number using the Argand diagram and the GTD approach
Authors: Derible Serge , Conoir Jean-Marc , Izbicki Jean-Louis , Rembert Pascal
Published: July 2002

Until now, the mode n of vibration of an immersed cylindrical shell, associated to the reemission of a peripheral wave, using an incident quasimonochromatic plane wave is performed by carrying out the method of isolation and identification of resonance. The new method proposed here involves only the FFT of the whole pressure signal backscattered at normal incidence by the shell, normalized using the FFT of the incident wideband signal. At a resonance frequency, corresponding to an unknown value of n, the background phase φexp is measured from the Argand diagram of the scattered pressure. It corresponds to the argument of the pressure at the resonance frequency. The geometrical theory of diffraction allows us to connect the background phase φGTD to the mode number n. This mode is then deduced by minimizing the difference between φexp and φGTD. Experiments are carried out for A and S0 resonances. Then, with a single backscattered signal, it is possible to obtain the frequency, the width, and the mode of the resonance.
Characteristic of a semiburied object in shallow water
Authors: Yang Shi-e , Li Xiukun
Published: July 2002

The impulse reflection of a semiburied object is strongly complicated due to a multipath channel effect in a shallow-water environment, and usually also mixed with unavoidable bottom reverberation. An efficient method of signal processing in order to obtain necessary characteristics of the object, which can be used for object identification, is discussed, and several experimental examples are given.
How listeners find the right words
Authors: Cutler Anne
Published: July 2002

Languages contain tens of thousands of words, but these are constructed from a tiny handful of phonetic elements. Consequently, words resemble one another, or can be embedded within one another, acoustics not withstanding. The past few years of psycholinguistic research have seen repeated confirmation that the process of spoken-word recognition by human listeners involves activation of multiple word candidates consistent with the input, and that these candidate words actively compete with one another. Current models of the word-recognition process are computationally explicit and can accurately reproduce the experimental results, as will be demonstrated by simulations with the SHORTLIST model, operating on a realistic vocabulary of 26 000 words. Activation and competition, however, do not exhaust the range of procedures which human listeners can call upon to find words in speech. My colleagues and I have recently established that listeners are sensitive, at an early, prelexical stage of speech processing, to constraints on what could potentially be a word of the language. Furthermore, cross-linguistic comparisons—of English, French, Japanese, and Sesotho—suggest that these constraints are not tailored to the characteristics of a particular vocabulary, but are universal.
European prediction models for building acoustics
Authors: Gerretsen Eddy
Published: July 2002

About 8 years ago work started in the European standardization organization (CEN) to create prediction models for several acoustic aspects in building: airborne sound transmission, impact sound transmission, facade sound transmission, facade sound radiation, and the noise caused by technical equipment. The main aim is to provide the link between the acoustic performance of products and elements, as measured by standardized laboratory measurement methods, and the performance in the realized buildings. So far the prediction models for the first four aspects are (almost) finished. The work on the part concerning equipment noise has yet to start, handicapped as it is by a lack of available knowledge in this area. The chosen approach for the models on airborne and impact sound transmission applies separate independent transmission paths between rooms, which can be shown to be a first-order estimation of a SEA approach. For these models a new quantity has been introduced to characterize the structure-borne sound transmission at junctions of building elements. Further work is focusing on the description of measurement methods to determine this quantity and on verification of the models in order to indicate more precisely their reliability in predicting the acoustic performance of buildings.
Flanking paths between walls and lightweight wood frame floors using statistical energy analysis
Authors: Nightingale T. R. T. , Steel J. A.
Published: July 2002

Previous work has examined flanking paths from a floor/ceiling assembly to a load-bearing wall (where the floor joists were oriented normal to the supporting wall). It was shown that beams at the joint (plates and joist header) must be considered when predicting transmission at this type of joint. The dominant flanking path was from the floor deck to the supporting wall which reduced the apparent sound insulation from FSTC 59 to 53. The path from the upper to the lower wall was insignificant. This paper presents the results of a similar study that examined flanking paths from a nominally identical floor/ceiling assembly to a non-load-bearing wall (where the joists were parallel to the joint axis). Measured velocity level differences and apparent sound insulation are compared to the load-bearing wall configuration. Flanking paths involving a non-load-bearing wall are shown to have no appreciable impact. Joint models are presented using both standard wave methods and dynamic stiffness methods. The joint models are incorporated into a statistical energy analysis model of the system. Measured and predicted results for the two joint configurations are compared and show good agreement between 100–3150 Hz.
Owner/builder perspective of the impact of trains on performance halls for Benaroya Hall, Seattle
Authors: Clapham Andrew
Published: July 2002

The Seattle Symphony began planning for a new concert hall in early 1987 at a location near their existing venue, the Seattle Opera House. During funding negotiations with The City of Seattle in 1992, the City made it clear that they wished to have the new facility located in their downtown core area. They offered a site that had many added challenges. These included being in the flight path of Sea-Tac International Airport; being alongside the Metro transit tunnel which is to accommodate light rail; being located in the heart of a very active city; and finally being located directly above the twin track railroad tunnel that runs north to south through the city center. In order to achieve the desired acoustical quality for the 2 500-seat main auditorium and 540-seat recital hall, not only for performances, but also for digital recording, a number of innovative design and construction techniques were required. These ranged from a massive foundation slab above the tunnel, to construction of a vibration isolated building within a building, which is supported on natural rubber isolation bearings. The challenges of designing and constructing this unique building will be presented.
Train and rail transit noise in cinemas and theaters: Case studies
Authors: Asselineau M.
Published: July 2002

Train and subway noise unfortunately often turns out to be part of the show in theaters and cinemas of large cities, as the history of rail lines construction, or simply the urban planning, brought them close together. This paper aims to submit and discuss a few case studies, involving both rehabilitation and new construction projects, that feature cinema and performance facilities located near underground and suburban lines, main lines, or even high-speed lines. Those case studies, which range from real success to total failure, outline the architectural and technical context of the situation and discuss the sound and vibration levels measurements, as well as the technical solutions that were applied to the construction. It turns out that in rehabilitation projects, while the client may be willing to improve the acoustics, structural limitations can often be encountered, while in new projects there often is a need to convince the client of the importance of vibration control.
An onboard acoustic data logger to record biosonar of free-ranging bottlenose dolphins
Authors: Nowacek Douglas P. , Tyack Peter L. , Wells Randall S. , Johnson Mark P.
Published: July 2002

An acoustic data logger has been developed which utilizes a two-channel DAT recorder housed in aluminum and attached to the dorsal fin. The recorder has a flat frequency response from 10 Hz to 14 kHz, and each tape can store 120 min. The first suction-cup hydrophone (sensitivity −205 dB) was placed 10 cm posterior of the blowhole, and the second 20 cm below the lateral base of the dorsal fin. The anterior ‘‘high-frequency’’ hydrophone, designed to record echolocation signals, has unity gain and a one-pole 10-kHz high-pass filter. The ‘‘ambient’’ hydrophone located at the base of the dorsal fin has +18-dB gain and a one-pole 1-kHz high-pass filter. To obtain echolocation recordings the ‘‘high-frequency’’ hydrophone was filtered through a simple demodulator in one of the deployments. The package includes VHF radio transmitters for tracking the animal and recovering the package after it releases via corrosible magnesium links. The package was attached to temporarily restrained animals which, after release, were followed to record behavioral data while the recorder logged acoustic activity. During the two successful deployments to date the logger recorded animal vocalizations, surfacing events, the sounds of passing boats, and hydrodynamic sounds produced by the animal’s fluke strokes. [Work supported by ONR, OVF, SeaGrant-WHOI.]
Possibilities for small-scale emission tomography of bubble plumes in shallow water
Authors: Smirnov Ivan P. , Khil’ko Alexander I. , Elmore Paul A. , Caruthers Jerald W.
Published: July 2002

Bubble plumes, created at the sea surface by breaking waves, emit sound in a broad range of frequencies. Based on the spatial and temporal characteristics of the emitted sound, emission tomographic reconstruction of the noise source distribution and evolution may be possible. It is shown that the space/time variables needed for the reconstruction process can be estimated from the coherence function of the radiated noise. The effectiveness of the reconstruction procedure when noise is present is estimated theoretically by the following physical model: (1) the location and time of bubble creation is assumed to be random and statistically independent, (2) the spatial distribution of the noise in the cloud, the spatial structure of the cloud, and the coherence function of the noise are described by a Gaussian distribution, (3) the sizes of the sources are much smaller than the size of the acoustic fields, and (4) the observation distance is much greater than the size of the sources. The requirements for the reconstruction process and the possible limitations of the method are discussed.
Mechanistic studies of ultrasonically enhanced transdermal drug delivery
Authors: Farrell J. M. , Mitragotri S. , Theis S. , Kost J. , Langer R.
Published: July 2002

The transdermal route of drug delivery offers a noninvasive and painless alternative to more traditional routes such as injections. However, its applicability is limited to only a handful of drugs due to the low permeability of the skin. It has been demonstrated that low-frequency ultrasound significantly enhances transdermal transport of a variety of drugs (sonophoresis). There is strong experimental evidence to suggest that cavitation plays a key role in this enhancement, although it is not clear which cavitational effects are primarily responsible for the transport. Cavitation can affect transdermal transport in at least two ways: It can induce changes in skin structure, creating pathways or channels for molecules to diffuse across and/or it can induce convective transport across the skin. An experimental system has been developed to assess contributions due to each of these phenomena individually. Although the data are insufficient to eliminate a role for convective processes, these experiments clearly indicate that stuctural changes in the skin play an important, and probably primary, role in enhanced transport.
Controlled environment for reciprocity calibration of condenser microphones
Authors: Wong George S. K. , Wu Lixue
Published: July 2002

For precision reciprocity calibration of condenser microphones it is necessary to operate the calibration apparatus under a controlled environment such that fluctuations in pressure, temperature, and relative humidity are reduced to a minimum. The design, implementation, and performance of a highly stable environmental chamber for calibration of microphones and instruments is discussed. For reciprocity microphone calibrations, the system enables resolution of better than 0.001 dB.
Modal analysis of violins and cellos
Authors: Rossing Thomas D. , Roberts Mark , Bynum Eric , Nickerson Laura
Published: July 2002

Normal modes of bowed string instruments are determined by the coupled motion of the top plate, back plate, enclosed air, ribs, neck, fingerboard, etc. Normal mode testing has traditionally been done using sinusoidal excitation, either mechanical or acoustical, although modal testing with impact excitation is a fast, convenient way to determine the normal modes of an instrument. Holographic interferometry provides the greatest detail about mode shapes, but the best understanding of the normal modes of an instrument results from application of more than one testing method. The normal modes in a cello are found to be quite similar to the corresponding modes of a violin, although they may appear in a different order in frequency. Modal frequencies in one cello were found to occur at 0.29 to 0.43 times the corresponding mode frequencies in a violin.
A normal-mode-based model of violin radiation
Authors: Bissinger George
Published: July 2002

A simple physical vibration–radiation model based entirely on experimental modal analysis can successfully predict the spatially averaged radiative properties of a bridge-excited violin measured with a rotating microphone array. The energy transfer from bridge excitation to acoustic radiation is modeled using (a) the measured transfer mobility Y(ω) to characterize energy transfer from the bridge to the corpus, and (b) the radiation efficiency Reff, calculated from a boundary element program for each normal mode to characterize the energy transfer from the corpus to the air. This model provides string-specific radiation predictions and allows one to make quick estimates of the averaged acoustical effects of violin adjustments or modifications which would be expected to change Y(ω) but not Reff, e.g., bridge trimming. Extensions of the model and future applications and directions for its application will be discussed.
Radiation mechanisms of a violin with known modal characteristics
Authors: Wang Lily M. , Burroughs Courtney B.
Published: July 2002

Multiplanar near-field acoustic holography (NAH) involves reconstructing the surrounding radiated sound field from measurements of the complex pressure on at least four intersecting planes enclosing a source [L. M. Wang and C. B. Burroughs, J. Acoust. Soc. Am. 100, 2654(A) (1996)]. After a brief review of the multiplanar NAH technique, results from applying the algorithm to a bowed violin (Hutchins’ SUS295) are shown for each open string. An open-frame mechanical bowing apparatus, which has been previously described, is used to excite the violin [L. M. Wang and C. B. Burroughs, J. Acoust. Soc. Am. 99, 2502(A) (1996)]. Areas of significant radiation on the violin structure are identified. Measurements are also compared to results from modal analyses previously performed on the same instrument. [Work supported by NSF Graduate Fellowship, Bell Laboratories GRPW Grant, and AAUW Selected Professions Dissertation Fellowship.]
Occupational noise measurement standard: ANSI S12-19
Authors: Goodwin Richard
Published: July 2002

This standard provides procedures for the measurement of occupational noise exposure from all types of noise; e.g., continuous, fluctuating, intermittent, and/or impulse/impact. Measurements may be reported as sound level with corresponding duration, time-weighted average sound level, and/or noise dose. This standard provides for the measurement of the noise exposure of individuals and can be extended to represent groups performing similar activities. It can also be used to measure the noise exposure from a given job or activity. This standard does not provide procedures for the measurement of occupational noise exposures attributable to the rise of earphones or telephone receivers. This standard presents recommended practices for utilizing instrumentation such as a sound level meter, noise dosimeter, integrating sound level meter, and acoustical calibrators. Guidelines are provided for measurement conditions such as the acoustical environment, measurement activities, and operational variations. The parameters surrounding the noise and its impact on the selection of instrumentation is presented. Specific guidelines for using a sound level meter, a noise dosimeter, and an integrating sound level meter are presented. Guidelines for documentation and reporting of the measurement of occupational noise exposure are specified.
Unusual jobs require unusual methods for noise exposure measurement
Authors: Barry John P.
Published: July 2002

With the diversity of the American workplace, the one size fits all approach cannot accommodate every occupational noise exposure measurement challenge. This is precisely why ANSI Standard S12.19-1996, ‘‘Measurement of Occupational Noise Exposure,’’ permits different measurement criteria and a variety of instrumentation and methodologies. The Occupational Safety and Health Administration (OSHA) and the Mine Safety and Health Administration (MSHA) use employee-worn noise dosimeters almost exclusively to document alleged violations of the occupational noise standards. However, employers and consultants may use any method that properly identifies those employees who need to be included in a hearing conservation program and that relates the noise exposure with the risk of occupational hearing loss and the effectiveness of hearing protection devices. Some environmental and operational hearing loss and the effectiveness of hearing protection devices. Some environmental and operational problems that affect occupational noise measurement are temperature, humidity, rain, wind, radio, magnetic and microwave interference, intrinsic safety, and the presence of hazardous materials. To illustrate effective handling of these measurement problems, the methodologies used in the occupational noise exposure assessment of operating municipal departments will be discussed.
The effects of organic compound doping in single-bubble sonoluminescence
Authors: Ashokkumar Muthupandian , Grieser Franz , McNamara William B. , Suslick Kenneth S. , Matula Thomas J. , Frensley C. Allen , Crum Lawrence A.
Published: July 2002

Controlled experiments have been conducted to ascertain the effects of doping with organic compounds on single-bubble sonoluminescence (SBSL) in water. Previous experiments with multi-bubble sonoluminescence (MBSL) indicate that millimolar additions of alcohols quench the sonoluminescence intensity [Ashokkumar et al., J. Phys. Chem. (in press)]. For a given concentration of alcohol, the degree of quenching apparently depends on the hydrophobicity of the alcohols. Similar results are observed in SBSL, using Ethanol, 1-Propanol, and 1-Butanol [intensity quenching measurements of 1-Butanol agrees with those of Weninger et al., J. Phys. Chem. 99 (1995)]. Spectra and radius-time measurements are obtained for these systems. Further experiments with weak organic acids and bases, which change their neutrality with pH, are also being conducted. The results and possible interpretations will be discussed. [This research supported by DOE, NSF, and the ARC.]
Auditory objects of attention
Authors: Darwin C. J. , Hukin R. W.
Published: July 2002

Although interaural time differences (ITDs) are the dominant cue for the lateralization of complex sounds, they are remarkably weak at grouping together simultaneous sounds. Experiments are reviewed which explore the relationship between this observation and auditory attention. A small difference in ITD between two sentences spoken in the same voice is sufficient to allow a listener to say which of two target words occurred in the attended sentence, even when the two sentences are resynthesised to have the same fundamental frequency. By contrast, a large difference in ITD does not allow a listener to exclude a single harmonic from a target steady-state vowel within an attended sentence. The results can be explained by assuming that listeners are not able to attend directly to frequency components that share a common ITD. Rather, listeners attend to the direction of auditory objects, whose frequency composition is determined by grouping cues such as onset time and harmonicity, and whose lateral position is determined from the lateralization cues of the component frequencies. [Work supported by UK MRC.]
Finite-element modeling of the vibroacoustic behavior of poroelastic materials
Authors: Bouhioui Hamid , Hodgson Murray
Published: July 2002

Porous materials are widely used nowadays as part of the insulation systems in the automotive industry or as effective sound absorbers in other areas, such as architecture. Their complex dynamic behavior is due to the various interaction phenomena within the elastic porous material. Such materials have been effectively modeled thanks to the original work of Biot. In the work reported here, the classical Biot theory for elastic porous materials is used for the development of a new three-dimensional finite element. While the finite-element development remains classical, a new numerical implementation is proposed. This new approach allows very fast computation times compared to the approaches existing in the literature. The finite element developed is general and suitable for any type of finite-size, extended-reaction porous material, with any boundary conditions. Comparisons are made using solutions found in the literature, along with a fine analysis of different aspects of the vibroacoustic behavior of porous materials.
The development of phonetic perception in the first year of life
Authors: Polka Linda
Published: July 2002

There is considerable evidence that language-specific influences on speech perception begin early in life with attunement to different aspects of language structure emerging at different ages in the first year. With respect to segmental units, cross-language research has focused on the perception of syllables differing in a single consonant. This talk will focus on research investigating developmental patterns in cross-language vowel perception in the first year of life. A series of experiments exploring vowel perception in English-learning and German-learning infants as well as English-speaking and German-speaking adults will be presented. The results provide further insights into the emergence of language-specific influences and also reveal language-universal perceptual biases that infants bring to the task of vowel perception. Implications of these findings with respect to the early development of phonetic perception and vocal production will be addressed. [Work supported by NSERC.]
Developing sensitivity to native language sound patterns
Authors: Jusczyk Peter W.
Published: July 2002

During the second half of their first year, English-learning infants begin to show sensitivity to the structure and organization of native language sound patterns. In particular, they give evidence of recognizing the phonetic, phonotactic, and prosodic characteristics of native language words. Moreover, their sensitivity to these features of native language sound organization appears to play a critical role in infants’ ability to segment words from fluent speech. Evidence for the use of this language-specific information in word segmentation by infants will be presented. In particular, we will focus on changes in the development of word segmentation abilities between 7.5 and 10.5 months of age. In addition, findings will be considered that suggest infants’ representations of the sound patterns of words are detailed both in terms of the phonetic properties and indexical features that they include. [Work supported by NICHD and NIMH.]
Numerical analysis on inversed bottom geoacoustic models for predicting a shallow-water acoustic field
Authors: Jin Guoliang , Zhang Renhe
Published: July 2002

The bottom reflection coefficient as a function of the grazing angle is calculated for a liquid bottom with depth-dependent sound velocity, density, and attenuation. The bottom geoacoustic parameters of a simplified model, which describes only the depth dependence of sound velocity and treats the density and attenuation as the depth independent, are derived from the bottom reflection coefficients by the least-squares fit. The inversion accuracy in reproducing an acoustic field in the water column is tested by the performance of matched field processing, the sound propagation losses, modal group velocities, and modal eigenvalues for numerical examples. In general, the test results are good for single frequencies, but degrade for broader frequency bands. The possible distortion of the depth dependence of sound velocity from the inversion under the simplified model is discussed.
Geophysical measurements on sediment cores and geoacoustic modeling
Authors: Thomson Philip P. , Dunlop John I. , Neissen Frank
Published: July 2002

Geophysical measurements on marine sediments cores have considerable interest and importance in underwater acoustics and marine geophysics. A series of studies on geoacoustic properties of marine sediments have been conducted and modeled on the samples from Australian continental shelves by the technique developed by UNSW. More works were carried out on cores from North Atlantic ocean basins at the Alfred Wegner Institute in Germany by using a multisensor core logger (MSCL). MSCL is a logging device which enables a number of geophysical measurements such as p-wave velocity, gamma ray attenuation, and magnet susceptibility on marine sediment cores encased in cylindrical plastic core liners. A pair of compressional wave transducers at 250 kHz is used to measure dilatational velocity and a gamma ray source and detector are used to measure attenuation in the cores. A comparative study of physical properties measured by a MSCL system and UNSW technique has been applied to a wide range of frequencies and modeled with modified Biot–Stoll theory.
Comparison of the performance of global optimization methods with perturbative methods in the estimation of ocean bottom properties from multifrequency data
Authors: Rajan Subramaniam D.
Published: July 2002

During 1988 a series of acoustic propagation experiments was conducted in the Hudson Canyon area off the coast of New Jersey. It included synthetic aperture experiments in which a source transmitting multiple tones was towed toward/away from a vertical array of receivers. By this means, a two-dimensional structure of the acoustic field was obtained at eight different frequencies. This data set is used to estimate the bottom acoustic properties using global optimization approaches such as simulated annealing and genetic algorithm and to compare their performance with that of perturbative methods, which because of their simplicity have some advantages over the global methods.
Offshore geoacoustic inversions using sounds from land vehicle activity
Authors: D’Spain Gerald L. , Kuperman William A. , Dorman LeRoy M. , Berger Lewis P. , Hodgkiss William S.
Published: July 2002

Land-based vehicle activity can be clearly detected and tracked by underwater acoustic sensors located outside the surf zone. This capability has been demonstrated with nearshore seismoacoustic data collected during the Marine Physical Lab’s Adaptive Beach Monitoring (ABM) program. The purpose of this paper is to demonstrate how the sounds from these land vehicles can be used to perform inversions for the offshore geoacoustic properties, somewhat akin to the use of Vibroseis in geophysical exploration. The event of interest here is where four tracked vehicles traveled down the beach at a speed of 10 m/s, creating signal beam levels that exceeded background levels by 35 dB in the 30- to 70-Hz band. The signal-to-background noise ratio in single element spectra also is sufficiently high that these vehicles can be used as sources of opportunity. The datum for the inversions is the strong frequency dependence of the phase velocity of the arrivals in this frequency band. Forward modeling is performed with a parabolic equation (PE) code written by Mike Collins. Results are compared to those obtained from the offshore arrivals of broadband detonations conducted on the beach. [Work supported by ONR, Code 32.]
Marine mammal ears: An anatomical perspective on underwater hearing
Authors: Ketten Darlene R.
Published: July 2002

Analyzing structure and function in specialized ears can produce new insights into fundamental hearing mechanisms and lead to technological advances. Research into dolphin echolocation is a classic example. Recently, however, concerns over anthropogenic sounds in the oceans pushed us to develop a broader knowledge of marine mammal hearing, and, in the last five years, hearing research on marine mammals expanded considerably. The resulting data on their hearing, ear anatomy, and vocalizations suggest that marine mammal ears are more diverse and complex than previously expected, with acoustic capabilities spanning infra to ultrasonic ranges. Seals are amphibious hearers with middle and inner ears similar to land carnivores, while the ears of whales are strikingly different and are adapted exclusively to hearing underwater. Consistent with high sound speeds in water, specialized fats, not air-filled canals, conduct sound to the ear, and both middle and inner ears are located well outside the skull. Vestibular components are reduced, consistent with cervical fusion related to hydrodynamic body shapes; but their cochlear components, particularly the auditory fibers, are hypertrophied. Neural hypertrophy may be adaptive for high background noise, but may also be related to exceptional signal processing mechanisms in both infra and ultrasonic whales.