bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of differential-capacitance accelerometers to underwater acoustic velocity sensing
Authors: Gabrielson Thomas B.
Published: July 2002

The differential-capacitance accelerometer is relatively common in medium- to high-grade commercial accelerometers but has been largely ignored for application to underwater acoustic velocity or acceleration sensors. The differential-capacitance configuration is capable of good long-term stability and exceptional low-frequency noise performance. The effective sensor impedance is determined not by the signal frequency but by the ac bias frequency. The low sensor impedance associated with high-frequency ac bias relaxes the requirements on signal cables. In addition, the critical preamplifier characteristics are those at the ac bias frequency so low-frequency (1/f) noise can be avoided. The differential-capacitance accelerometer does not have an inherent roll-off in response at low frequency so these devices can be used in self-orienting three-axis sensors for deployable systems. In machinery monitoring applications, synchronous detection of the ac-modulated signal yields a high degree of immunity to external interference and is amenable to straightforward multiplexing and optical or rf transmission. This paper summarizes the design principles associated with the differential-capacitance accelerometer through two illustrations: modification of a low-grade commercial product for improved signal-to-noise performance and multisensor multiplexing in the context of acoustic velocity sensing. [Work supported by the Office of Naval Research.]
Fiber-optic flexural-disk accelerometer
Authors: Doller Andrew J. , Reichard Karl M. , Garrett Steven L.
Published: July 2002

A fiber-optic, interferometric accelerometer incorporates a centrally supported flexural disk [U.S. Patent No. 5,368,485 (1994)] to convert vibration into differential strains on two spiral coils of optical fiber bonded to the disk’s top and bottom surfaces. The sensor coils form two legs of a Mach–Zender interferometer, terminated in a 3×3 coupler, whose outputs were used in a passive homodyne symmetric signal demodulator [U.S. Patent No. 5,313,266 (1994)]. A new digital implementation of this demodulation algorithm used fast fourier transforms to perform the necessary algebraic operations on time-windowed data segments, eliminating drifts. The sensor/demodulator system bandwidth was measured from 42 Hz to 5 kHz. A minimum detectable signal of 7 mrad was obtained with a 10-dB signal-to-noise ratio. At the lowest frequency, this corresponded to a dynamic range of 105 dB, which is 9 dB greater than the theoretical maximum for the 16-bit digitizer, due to interferometric conversion of amplitude modulation into frequency modulation. Thick-plate elastic models agreed with measured disk resonance frequencies. The measured sensitivity of 17 rad/g below resonance was less than the theoretical value of 23 rad/g, probably due to imperfect strain transfer through the epoxy adhesive used to bond the fibers to the disk’s surface. [Work supported by a grant from the Office of Naval Research.]
Alternating-current calibration of solid-state gyroscopes by reciprocity
Authors: Gabrielson Thomas B.
Published: July 2002

One of the hot topics in MEMS research is the development of miniature solid-state angular-rate sensors (gyroscopes). These devices have a number of potential applications including navigation systems for divers and unmanned vehicles, interpolators for periods of GPS loss of signal, and automobile skid sensors. For many of these applications, constant-rate (dc) calibrations are not representative of the expected excitations. Fortunately, high-quality ac-rate calibration can be done with an inexpensive apparatus by means of reciprocity. A suspended platform is driven in torsional oscillation by a pair of geophones acting as a force couple. Another pair of geophones is used as an angular velocity sensor. Since both of these transducer pairs are reciprocal, they can be used in conjunction with the device under test to perform a complete reciprocity calibration. The platform produces very smooth ac-rate motion from 1 to 20 Hz at rates of below 0.1 deg (rms)/h to 200 deg/h. The transfer impedance used in the reciprocity calibration is determined by the polar moment of inertia of the platform. This can be determined accurately by adjusting the separation of a symmetrically placed pair of masses and measuring the change in natural frequency. [Work supported by the Office of Naval Research.]
An inexpensive, portable, and rugged system for recording the low-frequency sounds of cetaceans
Authors: Berchok Catherine L. , Gabrielson Thomas B. , Bradley David L.
Published: July 2002

Many studies have been done on the low-frequency sounds of cetaceans. However, few of these studies have involved coincident photoidentification, biopsy, and behavioral observation. In order to make acoustical recordings in conjunction with the regular visual fieldwork done from inflatable boats on the baleen whales of the St. Lawrence, a recording system was designed to meet several requirements. It had to be very inexpensive; light enough to be carried onto the boat each day and deployed by hand; and rugged enough to survive being pounded and soaked when stored on the open boat. The resulting system consisted of two main parts: a recording system made up of DAT recorder, amplifiers, filters, batteries and voltage regulators; and a surface-motion isolation system made up of a spar buoy, omnidirectional hydrophone, cable and damping plate. A mixing circuit allowed for real-time detection of infrasonic signals through a pair of headphones. In addition to the description of the system and its calibration, samples of blue, fin, minke and humpback whale recordings will be presented, and a brief comparison of the system with and without the spar buoy will be shown. [Work supported by a graduate fellowship from NSF.]
Acoustical consulting in the Pacific Northwest: Rememberances of Buzz Towne (1919–1998)
Authors: Chaudiere Herbert , Richards Roy
Published: July 2002

Robin M. (Buzz) Towne was truly the icon of acoustical consulting in the Pacific Northwest. His intense interest in acoustics led him from a mechanical engineering consultant to a career in acoustics. He formed the first full-time acoustical consulting firm in the Pacific Northwest in 1960 with just one other person, but built the firm to 15 consultants within ten years. The firm continues to prosper today under new leadership, but the legacy of Buzz remains in the minds of those that worked with him and the clients he served. Buzz was a dedicated consultant whose drive for acoustial perfection resulted in many colorful (and often times amusing) confrontations with both staff and clients. This paper recalls some of these incidents, as well as describing a few of his significant consulting projects.
The virtual environment as a musical instrument
Authors: Mooney Jon W. , Rebelo Pedro
Published: July 2002

Naturally occurring acoustic environments helped to formulate ancient man’s musical rituals. Man-made acoustical environments shaped his musical style. Theories of architectural acoustics allowed the design of acoustical environments to suit specific musical styles. Using auralization, man’s acoustic environment can now be changed at will and thus becomes a musical instrument itself. This project was carried out in two steps. In the first, the model and the listener path through the model were selected beforehand, and the music was not processed in real time. In this mode, auralization serves as a post-production mixing technique. In the second step, the musician was in control of his music, the environment and the listener attributes with the auralization feedback in real time. Here, the acoustic environment becomes a true musical instrument. Standard 3D CAD models of environments are imported into the Acoustic Rendering (TM) program which creates impulse responses of the environment as multiple functions of time, frequency, source types, locations and orientations, and listener types, locations and orientations. The musical source is convolved with the appropriate impulse responses and the response is played back through a multispeaker system based on the Dolby (R) Surround Sound Format.
Melodic expectancy in infancy
Authors: Bergeson Tonya R.
Published: July 2002

Based on Eugene Narmour’s model of melodic expectancy, it might be predicted that infants would follow the same patterns of expectancy as do adults, at least with respect to the hypothesized universal principles. In experiment 1, 6- to 7-month-old infants and adults were briefly familiarized with two melodies: one that fulfilled specific expectancies and one that violated expectancies (direction and interval size), according to Narmour’s model. Infants and adults were subsequently required to detect a pitch change in the same location of each melody. Infants were able to detect the change in both melodies, and performance between melodies did not differ significantly. Adults were also able to detect the change in both melodies, but their performance was significantly better in the melody that fulfilled expectations. A confounding of expectation-fulfillment with stream segregation in the original melodies warranted further experiment. In experiment 2, as in experiment 1, 6- to 7-month-old infants detected the changes in both new melodies, and performance across conditions still did not differ. The present findings call into question Narmour’s claim his bottom-up principles are innately specified.
The acoustics of the bawu
Authors: Fetzer Casey A. , Brucker Nicole L. , Shackelford Eric D. , Cottingham James P.
Published: July 2002

The bawu employs a metal free-reed mounted in a bamboo resonating pipe with several finger holes. It is closely related in principle of operation to other Asian free-reed instruments, including the sheng of China, the sho of Japan, and the khaen of Thailand and Laos. In these instruments the reed vibration is strongly coupled to the pipe resonance, which is typically close to the natural frequency of the reed. The bawu, in contrast, employs a pipe resonator of variable effective length (using the tone holes) in which the pipe resonance and sounding frequency are both above the natural reed frequency. The most striking result of this is a significant change in tone quality. Variations in frequency and sound spectrum with blowing pressure have been studied, and some aspects of reed design and construction have been investigated. The relationship between frequency of reed vibration and pipe length has been studied to determine the range of pipe length over which the reed can be made to sound, as well as the amount of frequency shift associated with changes in resonance frequency of the pipe.
Theory of perfectly matched layer for elastic waves and their applications in cylindrical and spherical coordinates
Authors: Liu Q. H.
Published: July 2002

Recently, a general theory of perfectly matched layer (PML) is developed for elastic waves in anisotropic media and is applied to waves in cylindrical and spherical coordinates through an improved scheme of complex coordinates [Liu, J. Acoust. Soc. Am. 105, 2075–2084 (1999)]. As is known for electromagnetic waves, Berenger’s original PML scheme does not apply to cylindrical and spherical coordinates. The straightforward extension of the complex coordinates for elastic waves to cylindrical and spherical coordinates requires extra unknowns for time-domain solutions, wasting computer memory and computation time. The main idea of the improved scheme in this work is the use of integrated complex variables. It is shown that for three-dimensional cylindrical and spherical coordinates, this improved PML scheme requires no more unknowns than in Cartesian coordinates. The number of unknowns can be further reduced through the use of symmetry in the partial differential equations. The PML scheme allows an arbitrary inhomogeneity in the medium, and is suitable for numerical solutions of wave equations by finite-difference, finite-element, and pseudospectral methods for elastic waves in inhomogeneous media with cylindrical and spherical structures. Finite-difference time-domain (FDTD) results are shown to demonstrate the efficacy of the PML absorbing boundary condition.
Measurement of the complex impedance of a bubbly fluid in the vicinity of the bubble resonance frequency
Authors: Wilson Preston S. , Roy Ronald A. , Carey William M.
Published: July 2002

The acoustic impedance of bubbly fluids has been investigated and results for mixtures above and below resonance are common in the literature [e.g., A. B. Wood, A Textbook of Sound (Macmillan, New York, 1941)]. Because of the high attenuation encountered at frequencies near individual bubble resonance, traditional standing-wave and pulse propagation methods fail and little information has appeared in the literature for this regime. A new technique was developed to overcome this difficulty. Laboratory measurements of the complex plane-wave impedance of mixtures containing monodispersed air bubbles and water have been obtained for frequencies spanning the individual bubble resonance frequency. The experiments were conducted in a thick-walled water-filled tube, piston driven at one end and terminated with a bubbly fluid at the other end. This arrangement allows for operation near the bubble resonance frequency, since high attenuation is not encountered inside the waveguide itself. In addition, the standard transfer function method [J. Y. Chung and D. A. Blaser, J. Acoust. Soc. Am. 68, 907–921 (1980)] can be utilized, which results in broadband complex-valued impedance measurements. Results over a range of frequencies (low kHz) and void fractions with known size distributions will be presented and compared to existing theory. [Work supported by ONR.]
Oscillation of bubbles released from needles in natural and artificial sediments
Authors: Velea Doru , Hickey Craig , Sabatier James M. , Kolaini Ali
Published: July 2002

The acoustical characteristics of bubbles differ significantly in sediments as compared to those in sediment-free water. To examine this effect, an experiment has been designed by releasing bubbles from a needle/hydrophone assembly inside saturated natural and artificial sediments. Observations show that the resonance frequency of these bubbles released from needles in the sediment decreases and their total damping coefficient increases significantly compared to bubbles released from needles in sediment-free water. For example, a bubble with a radius of 2.5 mm in water has a resonance frequency of approximately 1.3 kHz and a quality factor of approximately 30. These parameters reduced to approximately 800 Hz and 2 for a similar bubble in a natural sediment with a mean particle size of 30 μm. Theoretically the total damping coefficient of an oscillating bubble in water consists of the thermal, acoustic and viscous contributions. Another dissipation factor, the Darcy damping, is found to be dominant in acoustic emissions of bubbles in sediments. This term accounts for the interaction forces between the liquid and the porous skeleton. The theoretical predictions of the total damping coefficient of bubbles in sediments (in the rigid matrix approximation) are discussed and the results are compared with experimental observations.
A highly efficient system for wave number frequency analysis using an slv in an underwater housing
Authors: Boober Walter H. , Abbott Phillip
Published: July 2002

The development of a water tight housing with an optical quality acrylic window allows for greater range of adaptation to imposed constraints for vibration analysis underwater. Most systems for such analysis utilize tanks with windows, or fiberoptic probes requiring carefully controlled rigging and positioning methods. Use of the underwater housing gains a range of freedom from many of the barriers which can inhibit or seriously limit the aforementioned methods for underwater vibration analysis. Utilizing this unique system it was possible to instrument, rig, position, test, and do an onsight cursory evaluation of wave number frequency on a 4.0 m long×533 m diameter cylinder. A 4.5-kg maximum force shaker was installed axially on an internal bulkhead. Approximately 2.43 m of the shell was free-flooded and 1.26 m filled with lime. The shaker was situated in the cavity separating the two sections. The cylinder was suspended vertically from a rotator and centered in 10 m of fresh water. The slv was positioned at approximately 9 m from the shell allowing for a 3.3-m axial scan of the shell.
Vibroacoustical preventive method for non-destructive testing and evaluation of rotative bladed systems
Authors: Gelman Leonid M. , Udovenko Lyudmila N.
Published: July 2002

Method uses spectral component parameters of vibroacoustical noise of systems as features. Estimation of mentioned parameters allows evaluation of the levels of mechanical and aerodynamic loadings of rotative bladed systems. Experimental results with aircraft gas turbine engine are presented.
How infants’ word segmentation abilities are affected by talker variability
Authors: Jusczyk Peter W. , Houston Derek M.
Published: July 2002

To begin building a lexicon, infants must extract, encode and store the sound patterns of words from fluent speech. Recent investigations suggest that infants begin this process at about 7.5 months of age [Jusczyk and Aslin (1995)]. Of course, to be useful in word recognition, lexical representations must endure in memory and generalize to tokens produced by different talkers. Investigations of infants word segmentation abilities have generally focused on items produced by a single talker. We have begun to investigate the extent to which infants are able to generalize their representations of words across different talkers. Our findings suggest that the ability of 7.5-month-olds to generalize across talkers are initially limited, but improve considerably over the next three months. Moreover, in contrast to the widely held view that representations of the sound structure of words are abstract prototypes, our results suggest that infants may encode information about talker characteristics into their representations. We discuss the development of these capacities, the conditions that promote generalizability across talkers, and the implications of these findings for understanding the growth of the lexicon. [Work supported by NICHD, NIDCD, and NIMH.]
Transducer-positioning system scanning around an aquatic for measurements of target strength
Authors: Ishii Ken , Sawada Kouichi , Miyanohana Yoichi
Published: July 2002

The transducer-positioning system has been designed in order to measure acoustic target strength (TS) of fragile and unstable in shape aquatic targets such as a squid. It is characteristic that directivity of TS is measured while making a transducer scan a fixed target suspended in the water. This system is loaded in the electric flatcar on the top of a tank. The distance between a transducer and a target is 3.65 m. A transducer moved from −45 to +45 deg in rotation around a target. The minimum unit of set value for a destination is 1 mm. Furthermore, a Laser pointer has been installed so that it becomes easy to observe a point where an axis of ultrasonic beam passes through a target when a target is prepared for suspension. The Laser pointer is set up in exchange for a transducer and is adjustable three-dimensionally. The situation between a transducer and a target, precision of positioning, and specification required for acoustic measurement system are described in this paper.
Key acoustical issues associated with the renovation and restoration of the Southern Theatre, Columbus, Ohio
Authors: Kahn David W. , Eligator Ronald T.
Published: July 2002

For an acoustics designer of performing arts facilities, the renovation and restoration of a landmarked facility can be frustrating, as there are rarely opportunities to alter the original architecture, and therefore alter the original acoustics. The Southern Theatre renovation and restoration was somewhat unique with respect to the extent to which the theater interior was altered to address code issues, and to incorporate HVAC systems. The Southern Theatre originally opened in 1896. The stagehouse, main floor, and second balcony were rebuilt as part of the renovation. The second balcony, which originally had a separate entrance from the street, was redeveloped to incorporate contemporary theater seating, as well as some additional technical support spaces including control rooms and new lighting positions. With the wide scope of the renovation came the opportunity to introduce some important acoustic improvements. Among the key issues discussed are the acoustical design of a unique silent air supply system, and design of an unusual enclosure for music ensembles that develops the lower volume of the stagehouse as a partially coupled reverberation chamber.
Noise isolation problems in the renovation of old urban factory buildings for residential use
Authors: Campanella Angelo
Published: July 2002

Special noise isolation problems arise when renovating old urban industrial buildings into apartments, condominiums, and hotels under the historic preservation rules. The living environment created should experience — as result of outdoor noise — not more than a maximum of 55 dBA in sleeping and living rooms. In addition, common walls and floor/ceilings should have sound isolation values of STC50 (apartments) to STC55 (condominiums) if at all possible. The ceilings of many rooms and loft spaces are often the exposed slatted wood or bottom of the floor above. This must be preserved in appearance, disallowing ceiling surface noise sound isolation treatment. Floor/ceilings should have impact sound isolation values of IIC50 (apartments) to IIC55 (condominiums) if at all possible. Window sound isolation is primarily selected for measured maximum noise levels caused by local truck traffic and emergency vehicle warning sirens on the basis of octave band noise and transmission loss values. The thicker window required must be compatible with existing metal or wood window frames. Test results and design concepts for some improved and preserved existing old commercial masonry urban structures will be presented.
Application of waveguide invariants to analysis of spectrograms from shallow water environments that vary in range and azimuth
Authors: D’Spain Gerald L. , Kuperman William A.
Published: July 2002

The waveguide invariant summarizes in a single scalar parameter the dispersive propagation characteristics for a given environment. An expression is derived for the invariant in shallow water environments where the bottom bathymetry varies with range and azimuth. It then is applied to the interpretation of broadband, single-element spectrograms collected during SWellEx-3, a shallow water acoustics experiment off the coast of San Diego. The unusual behavior of the interference patterns seen in the spectrograms from this experiment during the transmission of a 75–150 Hz pseudo-random noise sequence by a source towed over range-varying bottom bathymetry is well matched by the model predictions. [Work supported by ONR, Code 321US.]
Computed time-reversing array retrofocus azimuth size in a dynamic bottom-varying shallow-water sound channel
Authors: Dungan Michael R. , Dowling David R.
Published: July 2002

A time-reversing array (TRA) can retrofocus acoustic energy to the location of its original source even when the acoustic environment is complex and unknown. However, vertical TRA performance in the azimuth direction is entirely determined by variations in the water column and bathymetry. Predictions of TRA retrofocusing performance in this study are made with a parabolic equation code (RAM by M. D. Collins). In addition to the sensitivity of TRA retrofocusing to time variation in the water column of a shallow-water sound channel, this study addresses the azimuth size of the retrofocus. Interestingly, the azimuthal retrofocus size decreases with increasing range when internal waves are present. However, azimuthal retrofocusing is degraded as the acoustic propagation from the TRA is influenced by internal-wave dynamics within the water column. The range at which the effect of bottom variability on the retrofocus azimuth size matches that of internal waves is characterized. The internal waves are based on measured oceanic statistics drawn from the SWARM ’95 experiment. Retrofocusing results are presented for a variety of ranges and acoustic frequencies. [Work supported by the Office of Naval Research, Ocean Acoustics.]
Current criteria for selection of articles for publication
Authors: Pierce Allan D.
Published: July 2002

Principal publication selection criteria currently used by the Editors of the Journal are reviewed and discussed. Emphasis is given to those criteria that may be less well known and which could be controversial. One example is the criterion that research papers should represent a significant advance in our understanding of acoustics.
Relations between acoustic measures and the intelligibility of speech for children using cochlear implants
Authors: Uchanski Rosalie , Torretta Gina , Geers Ann , Tobey Emily
Published: July 2002

Speech was recorded from approximately ninety 8- and 9-year-old children who had used a cochlear implant for 4–6 years. Each child produced two sets of sentences for two separate purposes. First, 36 McGarr (McGarr, JSHR, 1983) sentences were recorded for subsequent intelligibility testing by listeners with normal hearing. Second, 11 newly constructed sentences were recorded for acoustic analysis. Acoustic measurements included: (1) VOTt−VOTd: average voice-onset time for word-initial /t/ minus that for /d/; (2) F2i−F2ɔ: average second formant frequency for /i/ minus that for /ɔ/; (3) vow/word: average ratio of vowel-to-word duration; and (4) differences in spectral moments for /s/-/∫/: mean, skewness, and kurtosis. The relation between individual acoustic measures and intelligibility will be presented. In addition, attempts to predict intelligibility from a linear combination of these acoustic measurements will be discussed. [Work supported by NIDCD.]
Acoustic design for University of Southern California, Annenberg School of Communications, lecture hall remodel
Authors: Gillan Fiona , Sevener Nathan
Published: July 2002

In 1998, the redesign of the 250-seat lecture hall at the USC Annenberg School of Communications was undertaken to update the aesthetics of the 1974 design and meet the modern functional requirements of the University. Primary uses of the hall were to be lectures, audiovisual presentations, and panel discussions. The existing fan-shaped space had a concrete ceiling, plastered concrete side walls, and a concave rear wall with a slatted wood acoustic finish. The existing reverberation time (RT60) was 0.95 s at mid-frequency, but there was a sense of over-reverberance and a lack of speech clarity. This was attributed to focusing by the curved rear wall and to excessive bass reverberation. The acoustic design targets included a modest reduction of the mid-frequency RT60, a significant reduction of the bass reverberation, and mitigation of the effects of focusing, as well as a maximum noise level of NC30 for the new HVAC system. Simple materials, including gypsum board wall linings, fabric wrapped panels, and acoustic foam in inconspicuous areas, were used to achieve cost effectiveness. Acoustics and architecture were fully integrated for efficiency of design. The project, completed in 1999, was an acoustic and architectural success. [Architectural Design by Siegal Diamond Architecture.]
Results of an acoustic normal-mode analysis of SESAME II data, and conclusions on internal wave activity
Authors: George Jacob , Field Robert L.
Published: July 2002

An acoustic normal-mode analysis has been used to examine the effect of internal waves (IWs) both at the receiving array and along the path of acoustic transmission in SESAME II data (year 1996; off the coast of Scotland). Power transfer from lower to higher modes has been observed to occur only intermittently. The sound-speed profiles (SSPs) at the receiving array during these occurrences are found to be nearly identical. Fourier analysis has revealed that a prominent peak in the frequency band 39–47 cycles/day in the acoustic reception at 800 Hz corresponds to a similar peak in the same frequency band in the thermal data at the receiver. That coincidence was investigated through normal-mode analysis, IW time delay between two nearby vertical arrays of thermal sensors, and a cylindrical wavefront model. The results show that the two peaks could not have been caused by the same IW. Therefore, the IW responsible for the acoustic peak should have originated farther north. [Work supported by ONR and NRL.]
2DOF model applied to the violin octet A0 and A1 cavity modes
Authors: Bissinger George
Published: July 2002

An optimized 2DOF model for the A0 and A1 cavity modes [E. A. Shaw, J. Acoust. Soc. Am. 87, 398–410 (1990)] has been used to estimate these frequencies for the Hutchins–Schelleng violin octet. The 2DOF model is notable because it predicts coupling between the A0 and A1 cavity modes [G. Bissinger, J. Acoust. Soc. Am. 104, 3608–3615 (1998)]. This coupling reduces the volume dependence of the A0 mode. 2DOF predictions of A0 frequencies are compared with measurements made on the four largest members of the octet during the course of rib-height modifications [C. M. Hutchins, J. Acoust. Soc. Am. 92, 639–650 (1992)]. Comparisons with new A0 and A1 measurements for the octet will also be made. [Work supported by NSF DMR9802656.]
A complexity measure for musical scales
Authors: Sevgen Alpar
Published: July 2002

Equally tempered scales with N semitones and M notes and interval structures n={n1,n2,...,nM}, where nk is the number of semitones between the notes tk and tk+1, possess the following properties: Each distinct interval structure n corresponds to a multiplet of N scales. Members of a multiplet can be labeled by a set of integers {c}, modulo N, called scale labels. Each scale label is the difference between the number of sharps and flats occurring in that scale and is unique within the multiplet if N and M are relative primes. This labeling does not differentiate between different scale structures.To do this, complexity is introduced as the sum of the number of sharps and flats occurring in a scale. For N=12 and M=7, out of 462 possible scale structures, the major scale and its cyclical permutations, called modes, have the minimum complexity which allows the practical use of the key signatures in music. Complementary scales where notes and no notes are interchanged have the same complexity. The minimum and maximum complexity scales occupy the opposite ends of the energy spectrum under the force laws ±nα (α≠0), between the notes of a scale.
Modeling the temporal response of auditory nerve fibers with a leaky integrator
Authors: Nakamoto Kyle T. , Smith Rita L. , Berg Bruce G.
Published: July 2002

A leaky integrator model (e.g., bandpass filter, followed by half-wave rectification and a low-pass filter) describes the temporal response of auditory nerve fibers presented with multicomponent, periodic sounds. It is shown that the spectra of the leaky integrator output closely resemble the spectra of period histograms obtained from published studies. Five parameters define the model: a time constant defining the cutoff frequency of the low-pass, one-pole filter, a parameter representing internal noise, and three parameters describing the initial asymmetric roex(p) filter (center frequency, low- and high-frequency skirts). For high intensities, an algorithm was introduced to represent saturation of the fiber. In most cases, the model accounted for more than 90% of the variance. Parameter estimates are consistent with known characteristics of auditory nerve fibers: (1) the low skirt of the initial filter was shallower than the high-frequency skirt, (2) increases in intensity were accompanied by shifts in the center frequency of the initial filter, and (3) bandwidth of the initial filter increased with intensity. With respect to the nonlinearity, square wave and full wave rectification were found to be implausible alternatives.
Modeling of tire/road interaction
Authors: Kropp Wolfgang
Published: July 2002

In order to reduce tire/road noise a deep understanding of the noise generation mechanisms involved is required. The key to reach this understanding is a correct model of the interaction between a tire and a rough road. This includes the modeling of normal and tangential contact between tire and road and the modeling of the wave propagation in the tire. A tire model is presented, which includes the radial, lateral, and tangential motion of the tire. The tire is modeled as a double-layered plate where the two layers are formulated by the general field equations including external tension. The tire model also takes into account the local deformation of the rubber surface due to external forces. This allows for solving directly the contact problem applying Green’s functions (i.e., impulse response functions) of the vibrating body. The model also takes into account the coupling between adjacent points at the surface of the tire. Numerical results will be presented for both the tire model and contact model.
Waveguide modeling as a tool for fitting a hearing aid
Authors: Szwoch Grzegorz , Czyzewski Andrzej , Kostek Bozena
Published: July 2002

A physical modeling method is used to develop a model of the acoustical elements of a hearing aid and to examine its properties. This model enables one to design an acoustical element having desired frequency characteristics, thus providing the acoustical system well fitted to the individual patient’s needs. The acoustical system of the hearing aid is treated as a waveguide—a long and narrow tube. Modeling methods similar to the ones applied to human vocal tract synthesis are used. The system is divided into several cylindrical sections. Physical phenomena present in the acoustical system (wave reflections, frequency-dependent damping, etc.) can be implemented directly in the model. By adjusting the parameters of the model, one is able to examine acoustical properties of various systems, having different shapes and dimensions. This method may be helpful for the audiologists during the process of hearing aid fitting.
Articulatory speech synthesis and the analysis of boundary conditions
Authors: Huang Jun , Levinson Stephen , Slimon Scott , Davis Don
Published: July 2002

In this work, a computational fluid dynamics (CFD) approach was used to model the unsteady fluid flow in idealized human vocal tracts. The speech waveform synthesis was based on the slightly compressible Reynolds-averaged Navier–Stokes (RANS) equations. A K-epsilon turbulence model has been used to represent the effects of turbulence. The vocal tract geometry was determined from the mid-sagittal cut through the three-dimensional vocal tract shape. The moving vocal tract shapes during the speech articulation were estimated using interpolation technique. The excitation signal for the simulation was accomplished by specifying a time-varying area at the inlet to the bottom of the pharyngeal cavity and a sawtooth waveform was used to represent the area variation in time. Different boundary conditions were applied at the inlet of the vocal tract. One is based on specifying the volume velocity and the other is based upon specifying the particle velocity, respectively. We will further analyze the effects of different boundary conditions using an analogy of transmission line T-network. Finally, we will present the waveform and spectrum of some synthesized voiced sounds based on the above CFD approach and boundary conditions. [This work was supported by Motorola and NSF.]
Design and development of software tool for high-power sensor array design
Authors: Joseph P. M.
Published: July 2002

The transmitting and receiving characteristics of sonar transducer arrays depend on various factors like its geometry, number of elements, source strength, relative phases of the elements, etc. An array with narrow main beam and low sidelobes is desirable for a variety of applications. But, these are conflicting requirements. One of the requirements can be achieved only at the cost of the other. It is the designer’s choice to select the parameters depending on the nature of application. Due to mechanical and electrical limitations, the measured array parameters are found to differ from the theoretically formulated ones, especially at higher drive levels. An array design package has been developed and presented in this paper for predicting the optimum array, based on the requirements of the user, taking into account various high-power electrical and mechanical limitations. In order to make the package more user friendly, the array design software has been split into different modules, each carrying out a specific task like array shape selection, element shape selection, power level selection, mode selection, etc.
Microfluidic device for amplification of ultrasonic pressure waves with application to MEMS hydrophones
Authors: Pascual Daniel N. , Compton Debora A. , Bifano Tom G. , Cleveland Robin O. , Pierce Allan D.
Published: July 2002

A micro-electro-mechanical systems (MEMS) device has been developed to amplify the fluid motion associated with ultrasound waves in water. Sound waves were sensed by the displacement of a small silicon membrane. Two structures were used in association with the membrane to increase the membrane motion: an acoustic horn and an acoustic resonator. An acoustic horn typically provides moderate signal gain across a broad bandwidth. An acoustic resonator provides significant gain in a small frequency band. Horns and resonators were constructed in bulk (100) silicon using KOH etching. Measurements of the membrane motion, in response to ultrasound in the 1- to 5-MHz range, were made with a laser Doppler velocimeter (LDV). Horn gains were measured to be on the order of 5 over the bandwidth used. Resonator gains of up to 3 were measured with a Q of 4. The LDV measurements also demonstrated that the membrane has a modal response which may be undesirable for the detection of acoustic waves. Both the horn and resonator structures have the potential to increase the sensitivity of most types of MEMS based acoustic sensors.
Focusing of acoustical shock waves at a caustic cusp
Authors: Coulouvrat François
Published: July 2002

This paper investigates theoretically the focusing of weak acoustic shock waves at a caustic cusp. Near the cusp, a diffraction boundary layer is introduced; its characteristic length scales are determined based on the Pearcey function which governs the linear acoustic field. With these adequate variables, the nonlinear wave equation is then shown to reduce to the KZ equation. The proper matching to the geometrical acoustics approximation provides the complete boundary conditions for any transient signal, so that the problem is numerically tractable. A similitude is found for an incoming step wave, and is compared to focusing at a smooth caustic. The linear approximate solution is obtained in the general case. Application for an incoming N-wave to simulate sonic boom superfocusing is also discussed.
Consonant recognition in noise with temporal cues: I. Effects of temporal envelope enhancement on identification performance
Authors: Apoux Frederic , Lorenzi Christian , Berthommier Frederic
Published: July 2002

This study sought to determine whether consonant identification performance in noise can be improved by applying an expansive nonlinearity to the temporal envelope of the speech stimuli. Consonants in /a-consonant-a/ context were processed through four broad bandpass filters, half-wave rectified and lowpass filtered at 500 Hz to extract the temporal envelope from each band. The envelope from each band was used to modulate a band-limited noise. In each band, the temporal envelope was either left intact or expanded by raising it to the power 1.414 or 2. Three signal-to-noise ratios (S/N) were used: −6, 0, and +6 dB. Twelve young normal-hearing listeners were tested twice in each condition, one week apart, using a forced-choice paradigm. Overall, identification performance increased with S/N and training. For each S/N and testing session, small but consistent improvements in identification performance of 2%–6% were observed when raising the envelopes to the power 1.414 or 2. Information transmission analysis performed on the aggregate confusion matrix showed that improved identification with expanded envelopes was mainly due to an increase in the reception of voicing.
The emergence of cross-modal complex temporal-processing abilities in children
Authors: Wright Kelley M. , Weisenberger Janet M. , McDonnell Jennifer D.
Published: July 2002

Studies of temporal processing of multi-item visual, auditory, and tactile stimulus sequences in children with central auditory-processing disorders have shown considerable variability even among the children in the normal control group, suggesting that some aspects of complex temporal processing may continue to develop throughout childhood. In the present study, two experiments were performed. In the first, groups of normally developing children aged 8, 10, 12, and 14 years were tested with three-item sequences of auditory tones (analogous to the pitch pattern sequence test widely used in assessing central auditory-processing abilities), sequences of colored boxes, and sequences of tactile vibrations presented to different locations on the forearm. Children were asked to identify the sequence presented. Results showed significant improvements in performance with age, with most of the difference between the 8- and 10-year-old groups. A second experiment examined younger children, aged 6, 7, and 8 years, with slightly modified versions of the same tasks. Again, a significant improvement in performance with age was observed. These improvements were evident for all sensory modalities, although overall performance levels were highest for the visual task and lowest for the tactile task. Results are discussed in terms of more general development of perceptual and cognitive abilities in childhood. [Work supported by NIH.]
A kinship with unusual auditory perception
Authors: Daly D. B. , Daly D. M.
Published: July 2002

Craig, while investigating vibrotactile sensation for blind readers, encountered several individuals with extraordinary perceptual ability [Science 196, 450 (1977)]. We report a two-generation kinship (three polyglots) with extraordinary ability to classify certain sets of synthetic acoustic stimuli. With sets of three or four formant /ge/-/ye/ which controls typically identify as containing two or three sounds (/e/, /ge/, /ye/), the mother and son could distinguish as many as six classes of sounds; the father could distinguish five. The additional classes involved stimuli with brief transitions; one class encompassed control transition durations. Each individual could also classify these same stimulus sets using two or three classes; these results were homogeneous (p<0.0001) with the results from a population of 45 age/gender-matched controls. These results require fine-grained differences in rate or duration of basilar membrane movements be represented in auditory cortex.
Thresholds for second formant transitions in front vowels
Authors: Goodman Shawn , Kewley-Port Diane
Published: July 2002

Formant dynamics in vowel nuclei contribute to accurate vowel classification in English. This study examined listeners’ ability to discriminate dynamic second formant transitions in female vowels /i, I, e, ε, æ/. Acoustic measurements were made from the nuclei (20% to 80% of vowel duration) of vowels in /bVd/ context in short sentences. Based on measurements along with informal listening, natural sounding vowel nuclei were synthesized. Synthesis parameters were selected to yield 12 discrimination conditions: initial frequency value for F2 (2525, 2272, or 2068 Hz), slope direction (positive or negative), and duration (110 or 165 ms). F0 and F1 were both steady-state. Stimuli with steady-state F2s were compared to those in which final frequency varied. Five listeners were tested under adaptive tracking using a modified 2AFC task with feedback to determine ΔF, the threshold for frequency extent (the difference in frequency between the initial and final F2 values). Analysis showed that initial frequency, slope direction, and duration all contributed to significant differences in ΔF. Results indicated that listeners attended to differences in frequency extent (Hz), not formant slope (Hz/s). Formant extent thresholds were 3 to 18 times smaller than extents measured in the natural speech tokens. [Work supported by NIHDCD-02229.]
The obligatory use of vowel duration in speaking rate normalization
Authors: Measer Kathleen M. , Sawusch James R.
Published: July 2002

Speech segment duration varies with speaking rate and phonetic identity. This study explored how listeners normalize for speaking rate when variation in segmental duration was a result of phonetic identity. Listeners identified the initial consonant in series that ranged from ‘‘beat’’ to ‘‘wheat’’ and ‘‘bead’’ to ‘‘weed.’’ Even though the endpoints of the series were spoken at the same speaking rate, the vowel duration in ‘‘bead’’–‘‘weed’’ was longer than ‘‘beat’’–‘‘wheat.’’ Luce and Charles-Luce [J. Acoust. Soc. Am. 78, 1949–1957 (1985)] showed that vowel duration is an acoustic correlate of final stop voicing. Even though the vowel duration difference was an acoustic correlate of the final consonant voicing, listeners responded to the series as if vowel duration variation were also a cue to speaking rate. Listeners gave more /b/ responses to the ‘‘bead’’–‘‘weed’’ series. These data are inconsistent with models of perception in which acoustic correlates are uniquely assigned to sources in speech production. Instead, speaking rate normalization appears to be an early, autonomous process and the perceptual utilization of duration information for multiple aspects of speech perception may be obligatory. [Work supported by NIDCD Grant No. RO1DCOO219 to SUNY at Buffalo.]
On idiolectal differences in speaking rate: A comparison of spontaneous and read speech
Authors: Remez Robert E. , Barnes Janelle , Shoretz Dalia , Chatav Maya , Piorkowski Rebecca
Published: July 2002

Individuals who share a dialect nonetheless differ consistently in phonetic expression. The origin of such idiolectal differences has been sought in sociolinguistically and in physiologically motivated accounts. Our study focused on characteristic differences in the habitual rate of speech production within a dialect, aiming to calibrate the contribution of neuromuscular constraint in idiolect differences. We sampled and analyzed the temporal characteristics of spontaneous and read speech produced by a set of adolescent female talkers from Brooklyn, New York. Spontaneous speech was elicited by open-ended questions, while the Farm Script was used as the text for production of read speech at comfortable and at rapid rates. Overall, the rate of rapid read speech was correlated with the rate of comfortable spontaneous speech and comfortable reading, indicating a clear contribution of neuromuscular constraints to characteristic differences in speech rate. However, some talkers exhibiting the ability to produce rapid speech at the fastest rates adopted comfortable speaking rates at the slower end of the distribution. In light of these findings, we doubt that idiolectal differences in speaking rate can be accountable solely by appeal to differences between individuals in agility of oral articulators. [Work supported by NIH DC00308.]