bluuebunny/crossref_metadata_2025 huggingface dataset:
Simultaneous bubble sizing using multiple acoustic techniques
Authors: Leighton T. G.
Published: October 2005

There exists a range of acoustic techniques for characterizing bubble populations within liquids. Each technique has limitations, and complete characterization of a population requires the simultaneous use of several, so that the limitations of each find compensation in the others. An experiment is described in which a simple controlled bubble population is subjected to a driving signal at pump frequency, ωp, and a second signal at the imaging frequency, ωi. The population is then simultaneous examined using geometrical scattering, and resonance scattering of the fundamental frequency (ωp), second and third harmonics (2ωp, 3ωp), and combination frequencies (ωi±ωp and ωi±ωp/2). Comparison is made of the ease, accuracy, and speed with which individual techniques measure the population, and what advantages accrue from their simultaneous deployment.
Temperature-related effects in single-bubble sonoluminescence
Authors: Cordry Sean M. , Crum Lawrence A. , Roy Ronald A.
Published: October 2005

Bubbles acoustically levitated in the appropriate underwater sound field can undergo radial motion which causes the bubbles to be luminescent, a phenomenon known as single-bubble sonoluminescence (SBSL). It has been reported [Hiller etal., Phys. Rev. Lett. 69, 1182 (1992)] that cooling the temperature of the water by 20 oC can increase light emission by a factor of 12.5. In this present study, the acoustic energy radiated by SBSL was measured using a needle hydrophone and the number of photons emitted by the bubble was measured with a photomultiplier tube. Comparisons were made between the acoustic and electromagnetic radiation emitted by the bubble for a range of different temperatures and acoustic pressures. Although the number of photons emitted varied strongly with the temperature, the radiated acoustic energy did not. These results suggest that it is the internal gas dynamics and not the bubble dynamics which is responsible for the observed temperature-related effects. [Work supported by the Office of Naval Research.]
Traveling wave impulses in synchronous sonoluminescence
Authors: Seeley Fred B. , Dowling Jonathan P.
Published: October 2005

Observations and measurements are reported of trains of traveling-wave pressure impulses that are coincident with the onset of stable, synchronous sonoluminescence. Each pressure impulse is initiated by a hard collapse of the centered bubble, travels outward to the flask boundary, is reflected, and then reconverges. The converging impulse apparently rebounds from the free boundary of the bubble and the impulse continues traveling outward and inward until it is synchronized with a subsequent collapse. It is hypothesized that synchronous sonoluminescence is produced when this train of spherically symmetric, concentric pressure traveling impulses are synchronized with the driving standing wave. Experimental observations of integral numbers of such impulses for a number of spherical flasks at several harmonics support this hypothesis. Theoretical analyses of these experimental observations and measurements will be presented.
Electrical matching of power transducers for acoustic cavitation applications
Authors: Looten Isabelle , Assaad Jamal , Frohly Jacques
Published: October 2005

Over the last 20 years, a large number of studies have been devoted to acoustic cavitation in liquids. High power transducers are needed to generate cavitation. A transducer working at 500 kHz will be presented. This transducer has been electrically matched using a stainless steel layer welded to a piezoelectric element. Optimal thickness of the matching layer, which is considered as a transmission line, has been found using a Mason’s circuit. The transducer conversion efficiency is experimentally evaluated to determine the acoustic pressure amplitude needed to generate cavitation in a liquid. The cavitation noise recorded with a hydrophone is used to characterize the cavitation state in the fluid. The energy of this noise is correlated to the acoustic pressure amplitude. Then the correlation between cavitation noise energy and chemical reactivity in homogeneous chemistry is also made. The bio-effect of cavitation on E. Coli cells is presented as a function of cavitation noise energy. It is evidenced that cavitation noise energy is an efficient tool to characterize a cavitation state in a fluid and to predict its chemical and bacteriological effects.
Measurements of ultrasonic pulse distortion produced by the chest wall
Authors: Hinkelman Laura M. , Waag Robert C. , Szabo Thomas L.
Published: October 2005

Ultrasonic wavefront distortion produced by transmission through human chest wall specimens was measured. Pulses with a center frequency of 2.3 MHz were received over a 20.00×20.16 mm2 area with a measurement spot size of 0.21×0.40 mm2 after propagation through a chest wall specimen. Secondary wavefronts produced by interactions between transmitted pulses and structures of the rib cage sometimes disrupted the main wavefront and interfered with the determination of wavefront distortion caused by soft tissue inhomogeneities. Differences in arrival time and energy level between 11.60×14.28 mm2 regions of the measured waveforms that did not include secondary wavefronts and references that account for geometric delay and spreading were computed. For 16 different intercostal spaces, the average rms value of the arrival time fluctuations was 21.3 ns with a mean correlation length of 2.50 mm. The energy level fluctuations had an average rms value of 1.57 dB and a correlation length of 1.98 mm. The results indicate that soft tissue inhomogeneities in chest wall specimens significantly distort ultrasonic pulses in the low MHz frequency range, although the magnitude of this distortion is noticeably smaller than that measured for abdominal wall specimens at 3.75 MHz [Hinkelman etal., J. Acoust. Soc. Am. 95, 530–541 (1994)].
Initial measurements of sound propagation through turbulence in a wind tunnel
Authors: Smith Randall W. , Henrichs Russell E.
Published: October 2005

Outdoor experiments of sound propagation through atmospheric turbulence are complicated by the difficulty of making sufficient measurements to fully characterize the flow field. Therefore the authors have initiated a series of experiments in a wind tunnel. The wind tunnel provides a means of creating various inhomogeneous flow fields through which to propagate sound. These wind tunnel flows are more easily measured and characterized than the atmospheric boundary layer. The goal of the experiments is to examine in detail the propagation of sound through increasingly complex flow fields, and to understand the effect of large-scale coherent turbulent motions on sound propagation. This presentation provides an overview of the experimental setup, a discussion of scaling issues, and preliminary analysis of data from the initial experiments. Some of the lessons learned from these initial experiments also will be discussed.
On the turbulence-induced thickening of sonic boom shock waves
Authors: Plotkin Kenneth J.
Published: October 2005

Two well-accepted effects of turbulence on sonic boom shock waves are the presence of random perturbations behind the shock waves, and random thickening of ths shocks themselves. Crow [J. Fluid Mech. 37, 529–563 (1969)] proposed a first-scattering model for the perturbations. This theory has been well accepted. Plotkin and George [J. Fluid Mech. 54, 449–467 (1972)] proposed a second-scattering/energy-balance theory for shock thickening. Pierce [J. Acoust. Soc. Am. 49, 906–924 (1971)] proposed a shock folding theory for thickening, and has recently [AIAA Paper 95-105] proposed a dispersion model. These thickening models present different perspectives, but are consistent with each other. Small-scale experiments by several workers have failed to fully replicate shock thickening, with consequent assertions that either thickening does not occur, or that it does occur but that the various theories are incorrect. It has been found that those experiments do not fully replicate the flight-test conditions, and that formulas from the theories have been applied without testing whether the necessary conditions have been met. A variation of the Plotkin/George theory is presented, which more closely relates that theory to Crow’s perturbation model.
On the influence of turbulence modeling for atmospheric sound propagation
Authors: Blanc-Benon Ph. , Juvé D. , Chevret P.
Published: October 2005

Incorporating random aspects in the numerical simulation of atmospheric sound propagation has led to a much better agreement between experiments and predictions. In particular, the turbulent scattering of sound into acoustic shadows had been demonstrated but some discrepancies still exist. In most of the numerical studies the fluctuations of the refractive index have been considered as scalar and characterized by a single length scale (Gaussian spectrum). However, sound propagation in the turbulent atmosphere is affected by quantities with different tensorial character and different scales. In this paper two possible ways of improving the simulations are investigated: by choosing a better spectral representation of the turbulence (von Karman instead of Gaussian form); by correctly taking into account the vectorial character of wind fluctuations. The turbulence is represented as a set of realizations of a random field generated by a limited number of scalar or vectorial random Fourier modes. Through each individual realization, the acoustic pressure field is computed with a wide-angle parabolic approximation. Ensemble averaging is then performed to obtain the statistical properties of the acoustic field: mean level, standard deviation of the fluctuations. Illustrations will be given for an upward refracting atmosphere, when a deep deterministic shadow zone is present.
Wideband sound propagation in a refractive shadow zone: Tests of turbulence models
Authors: Di Xiao , Gilbert Kenneth E. , Havelock David I. , Stinson Michael R. , Daigle Gilles A.
Published: October 2005

A wideband sound propagation experiment using discrete tones from 40 to 940 Hz has been conducted and analyzed to determine sound-pressure levels in a refractive shadow zone. It was found that at 40 and 90 Hz, the effect of turbulence was negligible. At 210 Hz and above, turbulence effects were significant. From 380 to 940 Hz, the shadow zone levels showed a relatively weak dependence on frequency. To test two turbulence models (Gaussian and Kolmogorov), the experimentally observed levels in the shadow zone were compared with parabolic equation calculations. The parameters of the turbulence models were determined from meteorological measurements. The Gaussian model, which agreed with acoustic data only over a fairly narrow range of frequencies, gave a strong frequency dependence for the levels in the shadow zone. The Kolmogorov model, on the other hand, gave good agreement with experiment over the entire band of frequencies, showing a relatively weak dependence on frequency from 380 to 940 Hz. It was concluded that the Kolmogorov turbulence model, which is consistent with inertial subrange turbulence, is a valid model for outdoor sound propagation predictions over a wide frequency range. The Gaussian model, which overpredicts the frequency dependence, is valid only in a narrow range of frequencies. [Work partially supported by the Army Research Laboratory.]
Further investigations on the propagation of sound over flat rough finite impedance surfaces
Authors: Chambers James P. , Sabatier James M.
Published: October 2005

The propagation of sound over rough surfaces of finite impedance is investigated. Initial experiments have illustrated the excess attenuation caused by roughness, that is, attenuation above and beyond that caused by geometrical spreading alone. These initial experiments were conducted indoors in a well-controlled setting for sound at grazing incidence. These measurements also show good agreement with Attenborough’s proposed model [J. Acoust. Soc. Am. 95(5), 2838(A) (1994)] that incorporates the effects of roughness into an effective admittance. The purpose of this present work is to find out if these trends persist in the propagation of sound over rough surfaces in a real-world setting. Sound signals will be measured above both rough and smooth agricultural surfaces with varying roughness profiles. Additional measurements will be made to determine the impedance and wave number of the surface as well as the roughness profile in order to examine Attenborough’s model in more detail. [Work supported by USDA.]
Determinants of the perceptual similarity of complex filter shapes
Authors: Zheng Yijian , Watson Charles S.
Published: October 2005

Sounds were created by passing an increasing-frequency 300-ms sawtooth (120–170 Hz) through each of the 15 complex filters. The filters were created by varying two parameters of a pair of overlapping second-order filters (CF: 500 and 1500 Hz). The parameters varied were the width of the upper filter (Q: 1, 3, 8) and the relative amplitudes of the two filter peaks (+12, +6, 0, −6, or −12 dB). Listeners judged the similarity of pairs of these sounds, equated for energy, using a ten-point scale. A multidimensional scaling (MDS) analysis suggested that when Q of the upper filter was low, the sounds were distinguished entirely on the basis of the relative amplitudes of the filters. For high upper-filter Q values, a different intensity-related dimension was the basis for distinguishing among the sounds, which were essentially identical on dimension No. 1. The two dimensions are associated with overall pitch, and with the salience of the high-frequency spectral peak. Various physical models are fitted to the data. [Work supported by NIDCD and by AFOSR.]
Diufhuis pitch and other anomaly pitches
Authors: Lin Jian-Yu , Hartmann William Morris
Published: October 2005

‘‘Anomaly pitches’’ are tonal sensations caused by anomalies in the spectrum of a low-frequency periodic wave, for example, by a missing harmonic [Duifhuis, J. Acoust. Soc. Am. 48, 888 (1970)]. They are immediately heard in the steady state and do not require any reference signal. This paper reports anomaly pitches for both missing harmonics and inverted harmonics. They occur in pulse waves (for any constant phase), in sawtooth waves, in waves with alternating sine and cosine phases, and in waves with Schroeder phase. With a series of missing upper harmonics it is possible to make a virtual anomaly pitch with a missing fundamental. The observations can be compared with the original explanation of the effect by Duifhuis based upon detection of the anomalous harmonic during gaps. Some of the conditions press this explanation to the limit but none has proved fatal. [Research supported by the NIDCD of the NIH.]
Pitch ringing induced by frequency-modulated tones
Authors: Aikawa Kiyoaki , Tsuzaki Minoru , Kawahara Hideki , Tohkura Yoh’ichi
Published: October 2005

It was discovered that specific FM (frequency-modulated) tones induce a ringing of a perceived pitch. A mathematical model was derived to explain this phenomenon. An abrupt change of the slope in a unidirectional FM tone induces ringing of the perceived pitch. The typical ring-inducing FM tone had a piecewise linear frequency trajectory in the log frequency axis with three parts: (1) frequency onset at 1 kHz rising to 0.732 kHz in 200 ms; (2) constant frequency at 1.732 kHz for 200 ms; and (3) frequency rising to 3 kHz in 200 ms. Several listeners reported one to three ringings around the middle part of the piecewise linear sweep. Frequent repetition of the listening test decreased the sensitivity of ringing perception. The ringing phenomenon can be explained by a second-order system as a functional model of sweep tracking. In order to provide experimental evidence for the second-order tracking system, specific values for the natural frequency and the damping factor were estimated. An inverse filter of this system was then constructed and was called the antiringing filter. In a psychophysical experiment, subjects compared the original piecewise sweep tone to that tone processed by the antiringing filter. Results demonstrated that pitch ringing was significantly suppressed by the antiringing filter.
Primary standards and instrument calibration: A national laboratory perspective
Authors: Nedzelnitsky Victor
Published: October 2005

In every advanced industrial nation, urgent needs for accurate, impartial measurement capabilities without unnecessary duplication of laboratories have led to the establishment of a national primary metrology and standards laboratory. These laboratories conduct international comparisons of calibrations and measurements intended to demonstrate sufficiently close agreement, or to reveal and to resolve unexpected discrepancies, among results from different nations. Such comparisons must precede, accompany, and continually sustain agreements regarding legal metrology and product conformity assessment, which are essential to the fair and successful conduct of international trade. These laboratories also provide scientific and technical support to the development of international standards, as well as the domestic standards of their respective individual nations. A national laboratory typically meets the critical needs of that nation’s private and public calibration laboratories for state-of-the-art measurement services through an instrument calibration hierarchy comprising direct or implied chains of ‘‘traceability’’ to the national laboratory. Selected, consequential international comparisons of electroacoustical calibrations from national laboratories are discussed. Examples of research in acoustical metrology at NIST and the measurement services provided to its customers are described.
Calibration: The legal perspective
Authors: Aldrich Robert W.
Published: October 2005

Several federal agencies have developed regulations to protect employees from health hazards in the workplace by establishing time-weighted average exposure limits. In order to ensure that exposures remain within acceptable limits, regulations have also included criteria for conducting accurate sampling. Accurate measurements of exposure can be obtained only when the instruments used are functioning properly and have been calibrated to the manufacturer’s specifications. Inaccurate measurements can lead to not only incorrect or unrepresentative worker sampling, but also can result in ineffective action by the employer if it becomes necessary to take corrective actions to reduce exposures to allowable levels. As a result, from a legal point of view, measuring instruments must be properly calibrated and maintained before they are used to measure worker exposures. In addition, the issue of instrument accuracy is important because courts have determined that in order for measurements to be considered ‘‘legally certain,’’ they must be accurate to within a 95% confidence.
Acoustic instrument performance verification—The manufacturer’s perspective
Authors: Blick Jonathan M.
Published: October 2005

The calibration and testing of acoustical instruments by a manufacturer is primarily a quality control function. Design parameters are differentiated from production test parameters during the design phase. Design parameters are inherent in the final product and may or may not be tested during production. Production testing is performed to ensure product uniformity within tolerances set by the manufacturer, many of which are dictated by national and international standards. Type testing by a third party is often used as a means of verifying compliance to standards, often at the request of customers. Independent testing is also beneficial as a means of verifying in-house test procedures.
Instrumentation calibration: The user/consultant’s perspective
Authors: Wilson George Paul
Published: October 2005

Accurate and supportable measurements of noise levels require the user/consultant to frequently ‘‘calibrate’’ acoustical instrumentation, usually under ‘‘field’’ rather than laboratory conditions. Field use calibrators are subject to a variety of environmental and use conditions, but must maintain accuracy and have calibrations traceable to NIST standards. In many instances the measurement data are used as facts in litigation or to establish compliance with ordinances and applied standards. Other uses include comparison with measurement data by others, with previous data and with projections. A description of calibration and verification methods employed by consultants is presented along with an assessment of their effectiveness. Also, presented are comments on the need for education of users in the use and significance of instrument calibration and the requirement for frequent ‘‘traceable’’ confirmations of calibration. Of particular importance is the concept and use of a system calibration which includes all relevant instrumentation components.
Instrument calibration: The hearing conservationist’s perspective
Authors: Michael Kevin L.
Published: October 2005

The audiometer is a critical element of the hearing conservationist’s daily routine. The measurement of hearing thresholds with an instrument that is out of calibration can result in errors in permanent records, loss of work time due to retesting, and potential legal action. Subjective audiometer calibration must be part of the hearing conservationist’s daily procedure. Calibration of the industrial audiometer must be performed at specified intervals at an appropriate laboratory. Factors related to the calibration procedure including cost, thoroughness, standards and the differences between calibration of industrial and clinical equipment are of interest to the hearing conservationist. Related issues including ambient room noise in the test booth, computer-based audiometry and the field measurement hearing protector attenuation must also be considered.
Horizontal refraction tomography for nonadiabatic propagation
Authors: Voronovich A. G. , Shang E. C.
Published: October 2005

A scheme of acoustical tomography of the ocean based on measurements of horizontal refraction angles associated with different acoustic modes has been developed recently [A. G. Voronovich and E. C. Shang, J. Acoust. Soc. Am. (to be published)]. Retrieving the 3-D structure of meso- scale inhomogeneities of sound speed proceeds in this case in two steps: (1) determining propagation constants of different modes in the horizontal plane (2-D linear tomography), and (2) retrieving sound-speed profiles basing on a known set of propagation constants at each horizontal point (1-D nonlinear tomography). This tomography scheme was successfully tested in a numerical simulation based on an assumption of adiabaticity of acoustic propagation. ‘‘Splitting’’ of the inverse problem into two stages appeared to be very effective computationally. The present investigation extends this tomography scheme for the situations when the mode’s interaction should be taken into account. Now, retrieving the set of propagation constants proceeds iteratively and includes data on sound-speed profiles found at the previous step. For a relatively weak mode interaction which can be considered in a perturbative manner iterations converge after a few steps and the inversion scheme remains very effective. Typical parameters of mesoscale inhomogeneities which can be handled by this iterative approach are estimated. [Work supported by ONR.]
Inversion of broadband multitone data from the Yellow Shark experiments
Authors: Gerstoft Peter , Hermand Jean-Pierre , van der Leij Taco
Published: October 2005

The estimation of forward model parameters—geometric, geoacoustic, and ocean sound-speed—by the inversion of acoustic field observations is considered. During autumn ’94 and spring ’95 an exhaustive set of broadband acoustic data and environmental data was obtained over a shallow-water area in the Mediterranean Sea [Hermand etal., ‘‘The Yellow Shark Broadband Inversion Experiments’’ (to be published)]. In this paper, inversion results of a mildly range-dependent transect southeast of the Island of Elba are presented. The inversion is carried out from multitone data (in the frequency band 200–1600 Hz) received on a 62-m vertical array from a fixed acoustic projector deployed at different ranges (4.5–15 km). Hydrographic data measured during the acoustic transmissions and coring and seismic profiling of the sediments along the acoustic track are utilized to control and verify the inversion process. Global optimization through a directed Monte Carlo search based on genetic algorithms and the Bartlett objective function is applied. All geometric parameters are well determined and also a range-dependent geoacoustic model and the ocean sound-speed profile are estimated. The use of observations at multiple frequencies provides considerable stability for the estimated parameters.
Investigation of Lamb waves in copy paper using laser ultrasonics
Authors: Johnson Mont A. , Berthelot Yves H. , Brodeur Pierre , Gerhardstein Joe
Published: October 2005

At present, the paper industry lacks an on-line, noncontact quality control system. Several studies indicate that there are strong correlations between paper strength and elastic stiffness properties. These elastic properties or elastic coefficients can be determined by measuring the velocities of propagation of various ultrasonic waves. Lamb waves, for instance, propagate in paper and appear to be sensitive to paper strength. Experiments have been conducted with a laser-based system to both generate and detect ultrasonic Lamb waves in copy paper. Results obtained regarding the relationship between the generation laser spot size, power density, and ultrasonic signal strength are presented. Paper damage is assessed at the generation spot. Phase velocity dispersion curves are produced for those modes that have sufficient signal-to-noise ratio. These dispersion curves are then compared to those predicted by ortotropic plate theory. [Work supported by OIP-GT.]
High-power ultrasound measurement
Authors: Wong G. S. K. , Wu L.
Published: October 2005

A system for the absolute measurement of high-power ultrasound in the range from 0.5 to 30 W is described. The theory of the system is based on measuring the ultrasound radiation force exerted on a conical-float suspended in water. The system is fully automated with the aid of the IEEE-488 bus under the control of a computer. Measurement procedures and an uncertainty audit representing a confidence level of approximately 95% are presented.
Determination of acoustic center correction for type LS2aP condensor microphones
Authors: Wagner Randall P. , Nedzelnitsky Victor
Published: October 2005

Acoustic center corrections for microphones are necessary for accurate free-field calibration by the reciprocity technique. Such corrections for several pairs of the relatively new type LS2aP microphone [IEC Std. 1094-1: 1992] were obtained by utilizing the theoretical inverse relationship between the sound pressure amplitude at the receiving microphone and the distance between the acoustic centers of the source and receiving microphones. For a nominally 10-V sinusoidal rms excitation of the source microphone, source-to receiver voltage ratios were measured with a dynamic signal analyzer at 500-Hz intervals in the extended frequency range (2 to 50) kHz. This procedure allowed all the data for a microphone pair to be gathered within several hours as a function of microphone diaphragm separation at 10-mm intervals from 101 to 311 mm. At each frequency, these ratios were corrected for atmospheric effects, including attenuation of sound, and then fit to a straight line (ratio versus diaphragm separation. Acoustic center corrections were calculated from the derived values of the fit parameters. These corrections agree with appropriately scaled values [IEC Publication 486-1974] for ‘‘1-in.’’ microphones with recessed diaphragms. Physical phenomena that cause small deviations from the linear fits will be discussed along with uncertainty estimates, and effects of spatially truncating data.
Evaluation of seafloor backscattering strength measured on the Florida continental shelf
Authors: Rogers Andrew K. , Yamamoto Tokuo , Kuru Murat , Rapids Brian
Published: October 2005

Recent experiments off the east coast of Florida have measured bottom backscattering strengths for several bottom types at frequencies of 7.5 and 15 kHz. Backscattering strengths are presented as a function of frequency, grazing angle, and azimuthal angle. Coincident with the backscatter measurements, forward scattering measurements and three-dimensional cross-well tomography experiments were conducted to quantify the sediment field. The data and analysis of these are presented in a companion paper given at this conference [Rapids etal., J. Acoust. Soc. Am.]. A newly developed scattering model [Yamamoto, J. Acoust. Soc. Am. (to be published)] has been employed to model the backscattering data. Using the results from the three-dimensional cross-well tomography as input, this model is found to be in good agreement with the data taken. Inversion of the data for sediment descriptors such as aspect ratio, compressional wave velocity fluctuation spectral intensity and spectral exponent, and dip structure has been made, yielding values similar to those obtained wih the insitu measurement by cross-well tomography techniques. These modeling results are detailed in this paper and their significance is discussed. [Work supported by ONR.]
Arctic ice roughness measurements and implied sound propagation losses
Authors: Ozard John M. , Todoeschuck John P.
Published: October 2005

The prediction of transmission loss is a long-standing problem in Arctic sound propagation. Some earlier estimates failed to predict the observed losses by a factor of 2. These estimates used levels of ice roughness that were believed to be characteristic of the Arctic. A 1400-km long profile of upward looking sonar from near northern Greenland to the vicinity of the Pole was examined. The statistics of the ice roughness are not stationary over this profile. The ice is rougher near the shore. Thus the transmission loss would vary over the profile depending on the roughness. A range of transmission losses that bracket observed values was found.
Theoretical prediction of the natural frequency of electrostatic ultrasonic transducers
Authors: Ge Li-Feng , Finkelstein L.
Published: October 2005

Electrostatic airborne ultrasonic transducers with an air-gap structure are widely used in automatic ranging, acoustic imaging, NDE, etc., so that there is an increasing need to develop a reliable model for their optimal design. A Helmholtz resonator model and a plate-under-tension model were presented successively in recent years, but both are still not very satisfactory. In this paper, an electrostatic transducer is treated as a thin plate supported by an air spring, in other words, its diaphragm is viewed as a plate situated on an air cushion. An interesting point revealed by this model is that its fundamental frequency stems from the air-gap spring, and the higher resonant frequencies are caused by the combined contributions of the bending stiffness of the diaphragm, in-plane tensile forces applied to the diaphragm, and the air-gap stiffness. The model is applied to predict the natural frequency of a typical V-grooved transducer with a 8-μm-thick Mylar diaphragm and a 0.5-mm pitch air gap. The first resonant frequency predicted by this model is 50.8988 kHz, and its nominal measured values are 51 kHz and 52 kHz, respectively, as reported by some researchers. [Work supported by the UK Royal Society.]
Micromachined ultrasonic transducers (MUTs): Theory and experiment
Authors: Ladabaum Igal , Khuri-Yakub B. T. , Spoliansky Dimitri
Published: October 2005

The successful modeling and fabrication of capacitive ultrasonic air transducers is reported. Emission and reception in air at 11.4, 9.2, and 3.1 MHz is demonstrated. Furthermore, transmission experiments through air–glass–air (70 dB of signal loss) at 3.8 and 5.1 MHz are reported. The transducers are made using surface micromachining techniques, which enable the realization of center frequencies ranging from 1.8 to 11.6 MHz. A theory explaining both the static and dynamic operation of the devices is presented. In addition to agreeing well with the experiments, the theory predicts that displacements on the order of 10−3 angstroms (with potential for 10−5 angstroms) are detectable with a 20-dB signal-to-noise ratio. Such detection sensitivity is shown to yield air transducer systems capable of withstanding over 100 dB of signal attenuation, a figure of merit that has significant implications for ultrasonic imaging, nondestructive evaluation, gas flow and composition measurements, and range sensing. [This work has been supported by a grant from ONR.]
Smart area actuator with integrated accelerometer array
Authors: Klunder Joseph A. , Corsaro Robert D.
Published: October 2005

This paper describes the design and evaluation of a very low cost high-sensitivity accelerometer included in a large area actuator. Recently MSI has begun commercial production of a 1-3 composite transducer material using an injection molding approach. This actuator material consists of a large number of transducer rods, which would typically be combined to form an actuator. NRL recognized that an incidental number of these rods could instead be converted for use as an imbedded accelerometer array, at little additional cost. This paper describes the design and performance of accelerometers formed using this process, and issues related to their proximity to the actuator. Such combination transducers are particularly needed in active control and smart-materials applications, but additionally would find use in advanced underwater, aerospace or robotic sensing applications.
Identification of a space noise control model and active noise control
Authors: Zhong Yan Jiong , Yue Kai , Zhang Zhen Shan
Published: October 2005

In order to get the mathematic model of a noise control system in space, which is the impulse response of a speaker–microphone system, a square impulse modulated by a single frequency signal has been used. In the paper, a pseudorandom correlation identification method is used to get the impulse response of a MIMO speaker microphone system in the spatial field. The dynamic process and the time delay of sound waves in the spatial field and speaker coils are presented exactly. The model is used for digital simulation and a space sound experiment using a developed adaptive filter algorithm presented by the authors which is the recursive algorithm with interlacing cycle and increasing phase. The sampled noise signal from the motor driver cabin is used as the input of the system. The simulation and the experiment have proved the correctness of the model and the effectiveness of the developed adaptive fillter algorithm.
Transmission and reception performance of multilayered transducer structures
Authors: Powell David J. , Ting Robert Y. , Howarth Thomas R.
Published: October 2005

Multilayered transducer structures offer the potential for greater performance in terms of increased radiated acoustic power and improved reception characteristics. In earlier work, a unidimensional modeling approach was presented, that was shown to provide a means of accurately predicting the in-air electrical impedance characteristics of a range of different laminated transducer structures [J. Acoust. Soc. Am. 97, 3299(A) (1995)]. These prototype devices have since been encapsulated within polyurethane rubber ready for in-water acoustic testing. This paper presents a theoretical and experimental analysis of both the transmission and reception performance characteristics of this group of multilayered devices. The effects of intermediate bondlines and electrode layers will be considered in terms of changes to both the device’s sensitivity and its resonant frequency. Transducer performance will be assessed via the standard figures of merit, TVR and FFVS, in conjunction with its pulse-echo transient response. Theoretical predictions from the unidimensional model are in good agreement with experimentally obtained values. The polyurethane encapsulant was found to have detrimental effects on overall transducer performance. Beam profiles for the laminated devices have been recorded experimentally and are compared to the responses of their single-layer counterparts. [Work sponsored by the Office of Naval Research.]
A reinforced Neoprene rubber boot for the barrel-stave flextensional projector
Authors: Jones Dennis F.
Published: October 2005

The Class I barrel-stave flextensional projector is a lightweight and compact underwater sound source that is well-suited to low-frequency sonar and oceanographic applications. By modifying a few of the parts used in the Class I projector, a high-power Class II or broadband Class III barrel-stave projector can be constructed, which is testimony to the versatility of the basic barrel-stave design. These projectors require gaps, between adjacent staves, that are sufficiently wide for free-stave vibration at the operating drive levels and water depths. Gap widths of about 1 mm are typical. A rubber boot is stretched over the projector to inhibit the ingress of seawater through the gaps. However, since the gap widths and boot wall thicknesses are similar, the boots can be forced into the gaps by hydrostatic pressure, causing significant variations in the projector performance parameters with water depth [D. F. Jones and M. B. Moffett, J. Acoust. Soc. Am. 93, 2305(A) (1993)]. To minimize these variations, a new rubber boot with reinforcements in the vicinity of the gaps has been fabricated and tested on a Class II barrel-stave projector. Measured results showing performance stability with depth are presented.
Shear hysteresis of rock at intermediate strains
Authors: Bonner Brian P. , Aracne-Ruddle Chantel , Shew Cindy
Published: October 2005

Rocks with appropriate microsctructure are nonlinear with hysteresis in the strain range 10-6 to 10-3 while showing little permanent damage during deformation. Nonlinear effects alter strong motions produced by earthquakes and explosions and may lead to new methods for relating the mechanical properties of rock to microstructure and transport properties. Results of laboratory torsion experiments will be presented to demonstrate that various nonlinear responses appear when granite and sandstone samples are driven in harmonic motion at low frequencies with increasing amplitudes. Modulus reduction, amplitude-dependent attenuation and harmonic generation occur and depend on microstructural parameters, including microfracture density and pore fluid content. Friction and adhesion at internal surfaces and the deformation of fluid phases in pores all play a role in these observed phenomena. Numerical constitutive models which include micromechanics are being developed to simulate nonlinear behavior for comparison with experiment. [Sponsored by OBES geosciences and performed under the auspices of the U. S. DOE by LLNLL under Contract W-7405-ENG-48.]
Thermodynamical aspects of modeling the mechanical response of granular materials
Authors: Elata David
Published: October 2005

In many applications in rock physics, the material is treated as a continuum. By supplementing the related conservation laws with constitutive equations such as stress-strain relations, a well-posed problem can be formulated and solved. The stress-strain relations may be based on a combination of experimental data and a phenomenological or micromechanical model. If the model is physically sound and its parameters have a physical meaning, it can serve to predict the stress response of the material to unmeasured deformations, predict the stress response of other materials, and perhaps predict other categories of the mechanical response such as failure, permeability, and conductivity. However, it is essential that the model be consistent with all conservation laws and consistent with the second law of thermodynamics. Specifically, some models of the mechanical response of granular materials proposed in literature, are based on intergranular contact force-displacement laws that violate the second law of thermodynamics by permitting energy generation at no cost. This diminishes the usefulness of these models as it invalidates their predictive capabilities. [This work was performed under the auspices of the U.S. DOE by Lawrence Livermore National Laboratory under Contract No. W-7405-ENG-48.]
Reflections on the nonlinear equation of state in rock based on experiment
Authors: TenCate James A.
Published: October 2005

Measurements were made of the propagation of 1-D nonlinear waves (i.e., Young’s mode) in a bar of Berea sandstone 3.8 cm in diameter and 1.8 m long. Both waveforms (time domain) and spectra (frequency domain) were measured. The experimental results were then compared with waveforms calculated from a numerical scheme based on the simple wave solution for 1-D waves in rock using a classical nonlinear equation of state. The numerical solution is written in MATLAB and runs quickly on a small personal computer. Attenuation was added by propagating the waveform a small distance, transforming the waveform into the frequency domain, and applying the attenuation, and then transforming back into the time domain and propagating the new waveform. The same method was applied earlier for nonlinear propagation of a sound wave in a tube of air by Pestorius and Blackstock. The experiments and simulations clearly demonstrate that a classical nonlinear equation of state is incomplete or inappropriate for describing or modeling nonlinear propagation in sandstone. Results from another model (Van Den Abeele, paper 2aPA8) suggest the same conclusions. [Work supported by OBES/DOE through the University of California.]
The model describing the higher-order elastic constants of solids with cracks
Authors: Sutin Alexander M. , Nazarov Veniamin E.
Published: October 2005

There are many experimental data showing that third-order elastic constants of solids with cracks can be anomalously high and can exceed these parameters for homogeneous solids more than a thousand times. Here a physical model of a medium with cracks is suggested to explain such high nonlinearity. The model is based on the assumption that the stress applied to a single crack is the same as that applied to the whole body, that is valid for a low concentration of cracks. The crack behavior was described using the model in which a crack can be presented as an elastic contact of two rough surfaces, pressed one to another under the action of internal stresses in the surrounding solid. The nonlinear behavior of a crack is due to the contact area changing when the crack is undergoing stress or extension. Linear and nonlinear elastic constants of the medium with cracks are calculated; it is shown that in this medium negative values of Poisson’s ratio and anomalously high values of the third-order constants are possible.
Noise discriminability. I. A comparison of the effects of temporal position and bandwidth
Authors: Rickert Martin E. , Robinson Donald E.
Published: October 2005

In previously reported work [S. F. Coble and D. E. Robinson, J. Acoust. Soc. Am. 92, 2630–2635 (1992); M. E. Rickert and D. E. Robinson, J. Acoust. Soc. Am. 93, 2386(A) (1993)] listeners discriminated among trials consisting of eiether two identical samples of noise or two nonidentical samples. Nonidentical samples were generated by replacing a segment of noise presented during the first interval with a new segment. Although the long-term power spectrum of the segments was the same, the temporal position at which segments were replaced had a significant effect on discriminability: performance was best when changes occurred at the end and was poorest when changes occurred at the beginning. In the present study the effects of temporal position were measured under two spectral conditions. In one condition, noise samples were identically filtered (100–3000 Hz or 455–655 Hz) for the entire stimulus duration (50 ms). The effect of temporal position is reduced with narrow-band stimuli but is not eliminated. In a second condition, the bandwidth was varied within each sample such that one segment was wideband (100–3000 Hz) and the other narrow band (455–655 Hz). Overall performance with mixed stimuli (1) is similar to that with pure wideband noise when the uncorrelated segment is wideband, and (2) is similar to that with pure narrow-band noise when the uncorrelated segment is narrow band. [Work supported by AFOSR.]
The relationship between binaural fusion and binaural interference
Authors: Dye Raymond H.
Published: October 2005

A stimulus-classification paradigm was used to examine the extent to which judgments of the laterality of 753-Hz targets were influenced by distractors of different frequency. On each trial, the target was presented with one of ten different interaural differences as was the distractor. Each test interval was preceded by a diotic presentation of the target alone. During a block of 100 trials, each combination of target-distractor interaural differences was presented once. The relative weights given to the target and the distractor were assessed by the slope of the best linear boundary between left and right responses. Data were collected for conditions in which the cues were interaural differences of level or time. For all conditions for which target and distractor weights were obtained, binaural interference was measured by determining threshold interaural differences for conditions in which the target was presented alone and in the presence of a diotic distractor. For most subjects, greater interference was obtained when the distractor was at a frequency that was given great weight, although the frequencies weighted most heavily for interaural differences of time were not the same as those weighted heavily for interaural differences of level. [Work supported by NIH.]
Temporal masking of amplitude modulation detection with a wideband noise carrier
Authors: Sheft Stanley , Yost William A.
Published: October 2005

Thresholds were measured for detecting amplitude modulation (AM) of a gated wideband noise signal that was either immediately preceded or followed by a modulated noise masker. The signal AM rate was 2.5, 5, 10, or 20 Hz and the masker AM rate ranged from 2.5 to 40 Hz. Signal duration was 200 or 400 ms and masker duration was 400 ms. The maximum elevation in signal AM detection thresholds due to the presence of masker modulation ranged across subjects from roughly 4 to 10 dB with the amount of masking generally greatest when the signal and masker AM rates were either close or the same. The extent of tuning in the modulation domain was broad in both the forward and backward masking conditions. When not modulated, the masker can be viewed as a fringe of the signal carrier. Separate conditions evaluated the effects of carrier fringes on signal AM detection. At low AM rates, the addition of either the forward or backward fringe benefitted AM detection. These results suggest that the decrement in low-rate AM detection due to carrier gating is not solely attributable to the neural onset response and short-term adaptation. [Work supported by NIH and NSF.]