bluuebunny/crossref_metadata_2025 huggingface dataset:
Speed of sound in real gases. I. Theory
Authors: Zuckerwar Allan J.
Published: October 2005

The simple Laplace formula for the speed of sound in gases is corrected to account for three real-gas effects: molecular degrees of freedom which in equilibrium are not fully excited, deviations from the ideal-gas law, and dispersion due to relaxation processes. These are called the specific-heat, virial, and relaxation corrections, respectively. The specific-heat correction is based on a power-series expansion ofCp0 (specific heat at zero pressure) with respect to temperature. The virial correction is based on a three-parameter formula by Kaye and Laby for the second virial coefficient and a new five-parameter empirical formula for the third virial coefficient. Both are used to derive the corresponding acoustic virial coefficients. The relaxation correction is based on both Landau–Teller and Arrhenius temperature dependencies and inverse-pressure scaling. Using independent handbook data to obtain values for the above three corrections, the theory is capable of yielding sound-speed estimates to high accuracy over a wide range of temperatures and pressures. The theoretical uncertainty is due to the uncertainty in the original data, smoothing process, and truncation error; these are discussed in detail.
The small-amplitude, continuous wave reflected field produced by a spherical source placed at the focus of an ellipsoidal reflector
Authors: Averkiou Michalakis A. , Cleveland Robin O. , Roy Ronald A.
Published: October 2005

Ellipsoidal reflectors are widely used in electrohydraulic lithotripters. The small-amplitude, continuous wave (cw) reflected field of a small spherical source that is placed at the first focus (f1) of an ellipsoidal reflector is investigated with both theory and experiment. This configuration is equivalent to a low-amplitude (linear regime), cw-driven lithotripter. To model the acoustic field reflected from an ellipsoidal reflector, geometrical acoustics is used to define a directivity function at the mouth of the reflector. An equivalent focused source with amplitude shading defined by the directivity function is then assumed as the boundary condition for the linear, lossless parabolic wave equation which is used to diffractively propagate the field outside the reflector. The spherical source is driven with a long tone burst at 470 kHz. The ellipsoidal reflector is made out of nickel and has a rhodium coating. The major and minor radii are 6.2 cm and 3.5 cm, respectively. Good agreement is found between experiment and theory. A useful property of ellipsoidal reflectors is that one can quickly and accurately position the source at f1 and the hydrophone at f2 by a simple iteration technique. [Work supported by NIH.]
Ultrasonic fields in the neighborhood of the central axis of a circular flat transducer
Authors: Imamura Tohru
Published: October 2005

Numerical studies on particle velocity and on sound pressure by circular flat transducers have been carried out, and the leaps of the phase delay of the sound pressure on the axis of the transducer and those of the specific acoustic impedance on it have been investigated [T. Imamura, J. Acoust. Soc. Am.98 , 2876(A) (1995)]. In the neighborhood of the central axis of the circular flat transducer, the leaps of the phase delay of the sound pressure and those of the specific acoustic impedance disappear at points off the central axis. In the very vicinity of the axis, the phase delay of the specific acoustic impedance increases sharply from minus to plus, where the amplitude is the minimum. According to the distance from the central axis of the circular flat transducer, the feature of the phase delay gradually fades out. In conclusion, the ultrasonic field on the axis of a circular flat transducer is the extremity of the ultrasonic field in the neighborhood of it. From these results, particle velocity and specific acoustic impedance of the ultrasonic field are revealed to be very important for analysis.
Analysis of diffracted waves from a wedge by the virtual discontinuity principle of diffraction
Authors: Ueda Mitsuhiro
Published: October 2005

The virtual discontinuity principle of diffraction (VDPD), which gives the representation of a sound field that satisfies both the wave equation and boundary conditions [J. Acoust. Soc. Am. 95, 2354–2362 (1994)], is applied to the analysis of diffracted waves from a rigid wedge in 2-D space. According to VDPD, diffracted waves from the wedge can be expressed as an integral of particle velocity along a half-line that starts from a corner point of the wedge and would pass through an observation point if it was drawn in the reverse direction. Since the particle velocity normal to the line is expressed as the sum of geometrical-optics and near-field components, diffracted waves are also expressed as the sum of waves contributed by the geometrical-optics and near-field components of particle velocity. In this presentation, simple relations expressing the two contributions of diffracted waves are derived and it is shown that the sum of the two contributions agrees well with the rigorous solution of diffracted waves.
Time-domain approaches to the edge diffraction problem: Applications to boxed loudspeakers
Authors: Svensson U. Peter , Andersson Roger , Vanderkooy John
Published: October 2005

The classical edge diffraction problem has an exact solution for infinite and truncated wedges. There are no explicit solutions for finite wedges but approximate formulations have been presented, many of which are based on the Kirchhoff diffraction approximation. These methods fail at low frequencies and for certain geometries. A method suggested by Medwin etal . [J. Acoust. Soc. Am. 72, 1005–1013 (1982)] for finite wedges, based on the exact Biot–Tolstoy solution, has proven successful when applied to noise barrierlike geometries. They tentatively propose a method for handling multiple diffraction. In the present paper their method is tested for the application of a boxed loudspeaker, a case where multiple diffraction is clearly evident. Comparisons are made with boundary element calculations. Modifications to Medwin’s method are discussed and other methods, for example, as suggested by Vanderkooy [J. Aud. Eng. Soc. 39, 923–933 (1991)], are discussed as well. Time-domain formulations, such as those discussed here, give insight to the polarity, time delay, and time distribution of the higher-order diffraction components.
Timbre and pitch strength in iterated rippled noise
Authors: Yost William A. , Patterson Roy D.
Published: October 2005

Iterated rippled noise (IRN) produces a perception with both tonal and noisy components, even when high-pass filtered to remove all resolved harmonics. IRN stimuli are generated by cascading ‘‘delay and add’’ networks, where the delay, gain after delay, and number of iterations are the variables that determine the pitch and the perceptual tone/noise ratio. The strength of the tonal component is directly related to the degree of regularity in the fine structure; the strength of the noisy component is inversely related to regularity. Autocorrelation, correlograms, and summary correlograms provide quantitative measures of regularity that explain the pitch and the perceptual tone/noise ratio of IRN stimuli. Experiments with IRN stimuli involving pitch matching, pitch strength discrimination, and masking show that temporal correlation measures provide better explanations of the data than do spectral measures. The perceptual difference between the tonal and noisy components is a timbre distinction; it is also referred to as relative pitch strength. IRN is also an example of streaming in the absence of spectral cues—streaming based on temporal regularity. The main properties of IRN will be illustrated with correlogram videos. [Work supported by NIDCD and DRA Farnborough.]
Time discrimination and amplitude modulation (AM) detection
Authors: Todd Neil P. McAngus
Published: October 2005

The model [N. Todd, ‘‘A theory of the principal monaural pathway I. Pitch and time perception,’’ J. Acoust. Soc. Am. 99, 2491(A) (1996)] proposes also to account for the psychophysics of time by the interaction of a ‘‘sensory memory,’’ in the form of the collective response of cortical bandpass cells, and a ‘‘long-term memory,’’ which is the result of learning in a cortical neural network. Since the time constants of the cortical cells are relatively long, their response to an inferior collicular (ICC) input lasts long after the ICC input has ceased (and hence the form of the sensory memory above). The cortical amplitude modulation response is roughly a Laplace transform of the ICC response envelope, and so is highly dependent on envelope duration. The cortical response thus captures both the pitch and durational properties of the tone. It is shown how this model is able to provide an account of two fundamental aspects of auditory temporal processing: (1) the psychophysical law for time interval discrimination and (2) the psychophysical law for AM detection. The model is further applied to the problem of the ‘‘filled interval illusion,’’ which hitherto has evaded a convincing explanation.
Identifying musical instruments from multiple versus single notes
Authors: Sandell Gregory J. , Chronopoulos Michael
Published: October 2005

These experiments investigated to what degree the identification of a musical instrument depends on change of timbre across total pitch range. Subjects were trained to recognize 12 orchestral musical instruments (natural recordings) by name. Each instrument was represented by a variety of pitches sampled regularly from the standard pitch range of that instrument. The sampling was four notes per octave, effectively forming (in musical terms) a diminished seventh chord arpeggio. First listeners identified the instruments from single note presentations taken from the arpeggios. Results showed that an instrument’s identity is not equally salient across its range of notes, in ways that differ for each instrument. Next listeners were tested on a variable number of notes (N=1,2,...,7) sampled from the arpeggio presented during training in such a way that with increasing N, a greater amount of the arpeggio’s total range was included. Results showed that on average, recognition improved as increasingly recognizable notes (experiment 1) were included in the arpeggio. The relationship between the rate of improvement with N and the recognizability of the single notes is explored. An auditory gestalt called ‘‘macrotimbre’’ is proposed to consider the role across-range timbre changes play in the identification of an instrument. [Work supported by NIH.]
Component mode synthesis method for a large-scale coupled structure–acoustic fluid interaction problem
Authors: Ichikawa Tetsuji , Hagiwara Ichiro
Published: October 2005

A component mode synthesis method capable of estimating acoustic responses efficiently in a coupled structure–acoustic fluid interaction problem is presented. In order to analyze the response in a high-frequency range, a high- and low-order truncatable mode superposition method, namely, the most general mode superposition method by Ma-Hagiwara, is incorporated in the reduction process included in both the formulation of component mode synthesis and solving the superimposed global equation of motion. By truncating lower modes, it becomes possible to analyze a system with fewer degrees of freedom than the existing modal reduction methods. Frequency response analyses of several test problems of damped structures are performed and compared with the multipurpose versatile code, MSC/NASTRAN, to demonstrate the efficiency and versatility of the proposed method.
IZANAGI ocean floor imaging surveys around Japan
Authors: Tokuyama Hidekazu , Yamamoto Fijio , Suyehiro Kiyoshi , Taira Asahiko
Published: October 2005

Since 1989 the Ocean Research Institute at the University of Tokyo has started deep sea floor imaging surveys around Japan by using IZANAGI, which was developed by cooperation between the Ocean Research Institute, the University of Tokyo and Seafloor Surveys International, Inc. It is characterized by an interferometric sidescan sonar, towed at a shallow depth, typically 100 m below the sea surface at a speed of up to 10 kn (5 m/s). Two sets of transducer arrays are mounted on each side of the tow fish, transmitting 11 kHz on the starboard side and 12 kHz on the port side. They operate simultaneously at transmitting, but individually at receiving. The range of swath width can be varied from 20- to 1 km. A sidescan image is composed of 1024 pixels per one side of the swath; thus for a 10-km swath each pixel has a constant width of 5 m. Total coverage of our surveys is, so far, approximately 100 000 km2 from various geotectonic areas in the seas around Japan. The main objective of our surveys is to clarify detailed ocean floor topography which represents slope failure, active faults related to large earthquakes in the deep sea, sedimentary structure related to surface sediments transportation, and submarine volcanoes.
Remote sensing of seafloor geoacoustic and geotechnical parameters using an expendable penetrometer
Authors: Akal Tuncay , Stoll Robert D.
Published: October 2005

A free-fall penetrometer based on existing XBT technology and able to sense deceleration upon impact with the seafloor has been developed and tested at a wide variety of different sites containing sediments varying from very soft mud to compact sand. When the probe impacts the bottom, there is rapid deceleration controlled by the shear strength of the sediment followed by a period of damped oscillation at a frequency that is dependent on the geoacoustic properties of the near-bottom strata. Extensive laboratory and field testing carried out over the past 3 years has established a convincing relationship between the characteristics of the deceleration signature (maximum deceleration, rate of change of deceleration, depth of penetration, etc.) and the physical properties of the sediment. By deploying the penetrometer at a wide range of sites where ‘‘ground truth’’ was simultaneously determined using quasistatic cone penetrometer tests, sampling and in situ measurement of wave velocity, it has been possible to develop a variety of correlations relating the deceleration signature to geotechnical and geoacoustic parameters such as undrained shear strength, shear-wave velocity, and porosity. [Work supported by the ONR and the SACLANT Centre.]
Synoptic fine-scale surveys of the seafloor with the new Deep Tow instrument package
Authors: deMoustier Christian P.
Published: October 2005

Over the past 3 years, a multisensor digital Deep Tow vehicle has been developed at the Marine Physical Laboratory to carry out fine-scale measurements near the seafloor down to 6000 m depth. The suite of sensors include: a pair of 110-kHz side-looking sonars, a 4-kHz sub-bottom profiler, a 40-kHz obstacle avoidance sonar, a 12-kHz navigation sonar, a 23.5-kHz up-looking sonar, a CTD, a transmissometer, a magnetometer, a complement of still and TV cameras, and a 100-kHz multibeam echo-sounder. The latter provides fine-scale swath bathymetry and acoustic backscatter imagery of the bottom over a swath roughly 60 deg wide. All the sensor data are digitized in the vehicle and are telemetered to the ship over a standard 0.680-in. electromechanical tow cable at bit rates between 500 and 1000 kb/s depending on the length and condition of the cable. Examples of the data collected during sea trials and during deep-water search operations are presented.
The Naval Research Laboratory’s high-frequency multimode towed vehicle
Authors: Miles Ronald T. , Smith Richard , Brown Robert A. , Stanic Stephen J. , Eckard J. Dan
Published: October 2005

To obtain high-resolution measurements of acoustic spatial variability in shallow water (SW) and very shallow water (VSW) over a wide range of environmental conditions, the Naval Research Laboratory has developed a highly stable multimode underwater vehicle that can be towed and its depth and attitude controlled via commands from the towing vessel. The vehicle was configured with manual and semiautonomous control systems, data acquisition and communications systems, and an acoustic sensor system for measuring acoustic variability in water depths from 20 to 100 ft. Two high-frequency (20- to 600-kHz) arrays were mounted flush on the sides of the tow body and operated in either broad-beam mode or ‘‘phased-beam’’ mode using the latest ‘‘Doily’’ technology developed at ARL Penn State. In ‘‘phased-beam’’ mode the arrays form sine and cosine shape functions, with the beam steer angle dependent on frequency of operation. Through selection of tow speed and pulse repetition rate, the scattering characteristics of the same area of ocean bottom are simultaneously measured over a wide range of frequencies. Technical details of vehicle design and operation and some results from a high-frequency experiment conducted during 1996 are presented.
Ocean floor mapping using a forward-looking, high-resolution array
Authors: Medeiros Michael R. , Carpenter Robert N.
Published: October 2005

A system for remote sensing of ocean bathymetry using a forward-looking sonar is being developed. The system combines a wide-angle transmit beam (for full volume coverage) with multiple, steered, narrow receive beams for object localization. Sample bathymetry data were collected in Narragansett Bay, RI using a 10-ms-duration, 3-kHz bandwidth, linear stepped FM transmit sonar pulse, centered at 87 kHz. Bathymetry results compare favorably with a sidescan of the test area [M. R. Medeiros and R. N. Carpenter, Proc. IEEE AUV-96, pp. 185–191]. In addition to bathymetry the system returns an echo level map which can, after correcting for system gains, transmission loss, and grazing angle, provide a measure of bottom backscatter. The system is currently under investigation at the Naval Undersea Warfare Center, Division Newport, for use as a bottom detection and collision avoidance forward-looking sonar for unmanned underwater vehicles.
Some nonuniqueness issues for MFP geoacoustic inversion
Authors: Tolstoy A.
Published: October 2005

Nonuniqueness is an insidious problem for all inversion methods, and it appears to be particularly virulent for the shallow water geoacoustic applications. For such scenarios the combination of many unknowns (from a few to many dozens) plus the nature of the solution space (which can be highly nonconvex and rippled) results in potentially untenable problems. This work will discuss MFP efforts via simulated data to address (1) the hunt for the ‘‘true’’ solution, (2) the suppression of false solutions via broadband processing (incoherent as well as coherent) and via multiple, distributed sources, and (3) the evolution of problem difficulty with increases in the number of problem parameters and with errors in ‘‘known’’ parameters. [Work supported by ONR.]
Development of a sonar system for ocean bottom profiler
Authors: Medeiros Diane , Antonelli Lynn
Published: October 2005

A mechanism for inobtrusive sub-bottom profiling in adverse ocean floor environments is being developed. Profiling of the ocean bottom has been accomplished using attenuation and relaxation time methods based on dispersion characteristics of chirp sonar pulse reflections developed by Precision Signal, Inc. [LeBlanc et al., J. Acoust. Soc. Am. 91, 116–126 (1992)]. Sediment classification data, using a 20-ms FM chirp sonar pulse in the frequency range of 2–10 kHz, were collected in Narragansett Bay, RI, and compared with core samples [LeBlanc et al., J. Acoust. Soc. Am. 91, 107–115 (1992)]. Results indicate a high correlation between the core-determined sediment properties and the estimates obtained from acoustic measurements to depths of 20 m. This sonar technique is to be implemented using converted torpedo sonar hardware adapted for use by Naval Undersea Warfare Center, Division Newport. The Ocean Bottom Profiler will consist of transmitters, receivers, data storage, and transmission systems of versatile and robust design, which can be adapted for use in towed, ship-mounted, and free-running survey vehicles.
Possibility of reconstruction layered bottom parameters in the shallow sea by the range-frequency dependencies of losses
Authors: Fokina Margarita S. , Fokin Vladimir N. , Sharonov Georgy A. , Kerzhakov Boris V.
Published: October 2005

In this work the opportunity to use range-frequency dependence of losses (RFDL) for restoration of the acoustic characteristics of the marine bottom is discussed. RFDL and dependence of optimum propagation frequency (OPF) (the frequency, at which losses are minimum) from a sound-speed profile, and characteristics of the layered bottom (impedance, attenuation of longitudinal and share waves in the bottom, sediment layers thickness) are analyzed. For numerical simulation of sound propagation in shallow water, a normal-mode method was used. Numerical simulation has shown that the optimum frequency of sound propagation in shallow water is rather sensitive to the acoustic characteristics of the upper sediment layers. In this work the opportunity to use RFDL and OPF for reconstruction of characteristics of the sea bottom and creation of acoustic model of the bottom in a wide range of frequencies is discussed. For experimental measurement of RFDL in shallow water, a method of broadband pulsing probing was used. The signal was received by autonomous bottom modules. The satisfactory agreement of experimental measurements with the results of numerical simulation confirms this opportunity of reconstruction of the bottom in shallow water by RFDL. [Work supported by RFFI Project N 96-02-18944.]
Free-field calibration of ‘‘1/2-in.’’ microphones
Authors: Fujimori Takeshi
Published: October 2005

A precise free-field calibration system of type LS2 microphones by the reciprocity technique is proposed. A source and a receiver microphone are each attached to a cylinder of 1/2 in. diameter, respectively, and the cylinders are set up perpendicularly at the center of the anechoic room. The output voltage of the receiver microphone and the input voltage of the source microphone are measured by an FFT analyzer, and the frequency transfer functions are averaged to improve the signal-to-noise ratio. To reduce the influence of the disturbing reflections in the anechoic room, the gating technique is adopted. Values for the position of the acoustic centers of MR112 microphones were measured by two methods—gating and conventional. The uncertainty of the values by the gating method was less than by the conventional method.
Uncertainty analysis of primary and secondary microphone sensitivity calibrations
Authors: Frederiksen Erling
Published: October 2005

Generally, measurement microphone calibrations consist of a relative frequency response calibration and a sensitivity calibration made at a reference frequency, 250 Hz or 1 kHz. As these frequencies are also the main calibrator operation frequencies, they are the most important calibration frequencies for microphones. The paper describes uncertainty of sensitivity calibrations at these frequencies. DPLA (Danish Primary Laboratory of Acoustics) makes primary calibrations by the pressure reciprocity technique in accordance with IEC 1094-2. The uncertainty of these calibrations influences the secondary calibrations performed by DPLA customers like the B&K Calibration Service Centres which perform comparison calibrations. Within recent years Primary Calibration Laboratories in Europe have taken several steps to reduce their calibration uncertainty. This uncertainty is related to the measurement of electrical transfer impedance of coupled microphones and other physical parameters, in addition to other factors such as calculation software and the operator. Also, the uncertainty of environmental sensitivity correction factors contributes significantly to the overall uncertainty of the measurement chain. Therefore, some coefficients are determined individually. The paper describes the weight of uncertainty components and resulting uncertainties. Today, ISO9000 and IEC/TC29 increase the need for uncertainty analysis.
Frequency response for measurement microphones: A question of confidence
Authors: Gramtorp Johan , Frederiksen Erling
Published: October 2005

For many applications it is important to know the frequency response of the measurement microphone. There are a number of methods available for determination of the frequency response of a microphone. Some of the methods are described in IEC standards, namely, 1094-2 and 1094-3. For the special laboratory standard microphones, as described in LS1P and LS2P (IEC 1094-1), it is possible to have a primary calibration at a national calibration laboratory. Most of the other measurement microphones are normally calibrated using the electrostatic actuator calibration method. The actuator response is measured, and the free-field corrections supplied by the microphone manufacturer are added. From most manufacturers no information about the uncertainty on the determination of the actuator response and the free-field corrections has been available. A complete set of uncertainty values for actuator responses and free-field corrections for the new Brüel & Kjær Falcon Range microphones will be presented and discussed.
Interaction of body-worn measurement microphones with the undisturbed sound field
Authors: Giardino Dennis A. , Seiler John P.
Published: October 2005

The undisturbed sound field (the sound field that exists without the worker present) is the reference for many damage-risk criterions. The introduction of the worker and a body-mounted microphone perturbs the sound field. The resultant sound field measurement differs from that of the undisturbed sound field. A number of researchers have examined microphone placement effects, however, these have only been conducted at limited azmithual angles in free field. A series of experiments was conducted to explore the interaction of a bodily worn measurement microphone, including the reflections and shielding effects, with the undisturbed field in both reverberant and free sound fields. New data are presented with respect to microphone placement information for 10-deg angle increments for a cohort of various size subjects (male and female). The new microphone placement data were incorporated into a previously published mathematical model to determine the accuracy of a measurement conducted with a body-worn noise dosimeter. Results indicate that body-worn acoustical instruments are accurate to within ±2.0 dB with respect to the undisturbed sound field provided the microphone is located on the shoulder of the most exposed ear.
Use of reciprocity to characterize ultrasonic transducers in air above 100 kHz
Authors: Anderson Michael J. , Liu Xu
Published: October 2005

The three-transducer free-field reciprocity calibration technique has been extended to apply to ultrasonic transducers operating in air at frequencies above 100 kHz. The reciprocity method was extended to apply to this frequency range by correcting for attenuation, which is severe in air, and for diffraction. Validation of the extended reciprocity calibration technique was performed by comparing experimental measurements of receive and transmit sensitivity over the frequency range 100–500 kHz with predictions obtained from a mathematical model for the test transducers and calibration system. It is believed that these are the first measurements of absolute sensitivity to appear in the technical literature for transducers operating in this frequency range in air. Receive and transmit sensitivity measurements obtained with the extended reciprocity calibration technique agreed to within 2.5 dB of model predictions. The location of the resonance peaks in the sensitivity measurements had a maximum difference of 7% from those inferred from measurements of transducer admittance and those predicted by the transducer model. It was concluded that both the extended reciprocity calibration technique and the experimental model were accurate to within this level of discrepancy.
Experimental investigation of a low flow-noise microphone
Authors: McGuinn R. S. , Lauchle G. C.
Published: October 2005

Attenuation of flow-induced pseudonoise from the pressure signal of a microphone placed in a flow field was experimentally performed by coupling the output from a hot-wire anemometer with that of the microphone (called a hot-mic for brevity). A pinhole microphone and a hot-wire sensor located just upstream of the pinhole opening were placed in a well-defined, low-speed turbulent flow in a rectangular duct. Controlled acoustic noise, both random and time harmonic, was superimposed on the flow noise by aspeaker source located near the entrance of the duct. Experiments proved that significant flow-noise attenuation is achievable by adaptively filtering the hot-wire signal using a least-mean-square algorithm before subtracting it from the microphone signal. Broadband flow noise is attenuated 20 dB or more at frequencies below 100 Hz and the resulting hot-mic spectra more closely resemble those of the uncontaminated microphone over an even greater frequency range. Moreover, the resulting signal from the hot-mic retains the acoustic pressure information of interest, making the hot-mic an ideal ‘‘sensor‘‘ for use in active noise control applications where the sensing or error microphone must be placed in a flow field. [Work sponsored by the United Technologies Research Center.]
Hearing damage risk assessment by a personal noise dosimeter using a portable digital audio tape recorder
Authors: Ito Akiyoshi
Published: October 2005

A personal noise dosimeter was newly developed using a commercially sold portable digital audio tape recorder (DAT) and an electret condenser microphone. The method allows one to measure noise fluctuations during working hours at octave or one-third-octave band levels. From these exposure data, the critical band level for a noise-induced temporary threshold shift (NITTS) was estimated. The fluctuation of an NITTS induced by that noise exposure during working hours could thus be estimated by means of the formulas of NITTS growth and the unit step function method. This dosimeter is expected to contribute to more precise hearing risk assessment using estimated NITTS values. Especially, the maximum NITTS values that appeared during noise exposure could be useful to quantitatively evaluate the effect on hearing of noise controls, such as noise reduction at sound sources, shortening of exposure time by taking rests, or wearing ear protectors. Therefore, this technique will be widely applicable in different workplaces and could contribute to promoting more effective noise control of various types.
Issues in longitudinal analysis of hearing conservation data bases
Authors: Prince Mary M. , Smith Randall J. , Gilbert Stephen J.
Published: October 2005

Several hearing conservation programs (n=15) from a cross-section of U.S. industries were examined to test whether there are greater rates of change in hearing levels in relation to increasing cumulative noise exposure during the period of audiometric follow-up. The analysis also examined whether rates of hearing loss were lower among workers who wear hearing protection relative to workers who do not. These 15 audiometric databases had a total of 15 794 workers with 62 095 audiograms. Differences in a linear combination of 1–4 kHz biaural hearing levels of consecutive audiometric tests were examined using mixed effects models to account for correlated, repeated observations on individuals. These differences were modeled as a function of cumulative noise, gender, race, hearing protection use, age, learning effects, and baseline hearing level (measured after 14 h of quiet time). Analyses were conducted for the combined and individual databases. The analysis indicates there is significant heterogeneity among the databases. This heterogeneity by database complicates further analysis and makes interpretation of model results difficult. These difficulties will be highlighted with recommendations for data needed to evaluate hearing conservation effectiveness.
Occupational tinnitus
Authors: Gabriels Pam
Published: October 2005

This paper focuses on noise exposure and its relationship to tinnitus. In a study of 38 725 Western Australian workers exposed to occupational noise, 28% reported tinnitus. As more studies identify occupational noise exposure as the major cause of tinnitus, it will be necessary to look carefully at ways of introducing information about tinnitus into hearing conservation programs without unnecessarily alarming workers and employers and initiating a flood of claims for compensation. There exists a need for universally accepted disability standards for tinnitus and better education concerning tinnitus for both workers and employers.
Low-frequency improvement for hearing protection devices
Authors: Arenas Jorge P. , Munita Juan A. , Monsalve Ana M. , Salazar Ana M.
Published: October 2005

The use of hearing protection devices has become a common measure of noise control in working environments. An efficient device must shield the receiver against the sound energy radiated from the noise sources in a wide range of frequencies. If the hearing protection made available is not potentially effective in preventing on-the-job excessive exposures, then the hearing conservation program will not achieve its goal of adequately protecting the noise exposed population. However, the commonly used hearing protection devices do not have a significant effect on low-frequency noise. The objective of this work is to develop an electronic device following the concepts showed by Conover’s design based on superposition. The sound is decomposed by filtering, processing, and inverting in the ear channel. It must be noted that low-cost electronic components were used, allowing it to be incorporated in hearing protectors which had already been made. Improvement of insertion loss is calculated by means of standardized procedures in order to estimate practical applications, reduction in dB(A), and transfer functions in frequency domain. The performance of conventional hearing protectors used in industrial-noise control can be improved in some cases (low frequency), producing a significant increase in IL. [Work supported by ACHS.]
‘‘Medium-weighted dose’’ (MWD) of noise as method of estimation of long protracted noise
Authors: Menshov Alexander A.
Published: October 2005

For the estimation of A-weighted occupational noise level in several countries (Russia, Ukraine, and so on) use of dose of noise yields a single number and allows one to demonstrate the excess above the sanitary standard. Onedose is equal to the value of the standard level at work: −80, at rest: −40, and at sleep: −30 dBA. Increasing the level of noise by 3 dBA will increase one dose by a factor of 2 (two doses), at 6 dBA the increase is by four times (four doses), and so on. The principle of the dose approach spread to community noise. This allows one to estimate community noise after work in another two periods of 24 h of rest (8 h) and sleep (8 h). It was proposed to estimate a consistent occupational and community noise by a ‘‘medium-weighted dose’’ (MWD) of noise during one day (24 h) [A. Menshov, J. Acoust. Soc. Am. 96, 3274(A) (1994)]. This method may be used for estimating long protracted noise during a week, month, or year. The sum for a MWD of noise is computed according to each day (24 h) of the week, each week of the month, and each month of the year divided by the total time. The quantity of MWD of noise for each week, month, or year takes into account the absence of the occupational noise on holidays and on vacations. The calculation of MWD of noise over a complete year is very important for agriculture.
Plasma diagnostics and sonoluminescence
Authors: Lepoint T. , Lepoint-Mullie F. , Avni R.
Published: October 2005

Plasma diagnostic techniques are applied to single- and multibubble sonoluminescence (SBSL and MBSL). In the case of SBSL the electronic temperature (Te) and density (Ne) are deduced on basis of the spectrum of an Ar bubble in water [the recording by R. Hiller et al., Science 226, 248 (1994)]. This analysis, based on the emission continuum, reveals that the intracavity sonoluminescent medium behaves as a sparklike plasma highly charged with energy (Te=20 000 K; Ne=1025 m−3). In the case of MBSL (Ar bubbles in water), the method of the ratio ‘‘intensity of a line/intensity of the adjacent continuum’’ is used in order to determine Te. The higher the ultrasonic frequency, the hotter the bubble interior is. Two scenarios are analyzed (plasmas with a degree of ionization 〈or〉 1%) and the order of magnitude of Ne is estimated. The conditions associated with multibubble systems appear to be of the same kind as those associated with SBSL, with a lesser degree of intensity, however. The possibility is discussed that local thermodynamic equilibrium (LTE) or partial LTE is reached. [Work supported by F.N.R.S., Belgium.]
Hydrodynamic simulations of an imploding bubble
Authors: Moss William C. , Clarke Douglas B. , White John W. , Young David A.
Published: October 2005

Numerical solutions of the hydrodynamic equations of motion for a collapsing bubble have shown that shock waves can be generated during the collapse. It has been shown that these shock waves can supply and remove energy from the center of the bubble rapidly enough to account for the picosecond duration flashes that are observed experimentally. However, these solutions have not included energy loss mechanisms, so the calculated temperatures are excessively high. More accurate numerical simulations are discussed that (i) model the shocked gas as a plasma with distinct ion, electron, and radiation temperatures, and (ii) include energy losses by ion conduction, electron conduction, and radiant energy transport. As an example, a sonoluminescing bubble of deuterium is considered, whose sinusoidal driving amplitude is enhanced by a small pressure spike. Although the calculated radiation and electron temperatures are only tens of eV, the calculated peak ion temperatures are a couple hundred eV (≊2 000 000 K), which may be sufficient to initiate a very small number of thermonuclear reactions at the center of the bubble. [Work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.]
Sonoluminescence and the convective/diffusive transport of heat and mass
Authors: Szeri Andrew J.
Published: October 2005

A new model is presented for the gas dynamics within a bubble at conditions that lead to the phenomenon of sonoluminescence. The spherically symmetric Navier–Stokes equations with variable properties are solved together with momentum and energy equations in the liquid. Calculations are presented for bubbles of argon, helium, and xenon in liquid water. The first main result is that, in contrast to recent models of air bubbles in water, there are no sharp shocks focusing at the origin of the bubble. An alternative mechanism for energy focusing in noble gas bubbles is proposed that is consistent with a smooth onset of sonoluminescence with increasing acoustic forcing, as observed in experiments. The second main result concerns an observed correlation between sonoluminescence intensity and the thermal conductivity of the gas, which suggests that heat transfer plays a dominant role in the focusing of acoustic energy. It is shown instead, that mechanical effects associated with the molecular mass of the gas figure prominently in determining the peak temperatures and pressures in strongly forced bubbles. Finally, mass transfer into and out of the bubble is examined using a special nonlinear form of Henry’s law.
A new hypothesis on single-bubble sonoluminescence
Authors: Prosperetti Andrea
Published: October 2005

Attention is drawn to the fact that the very mechanism that traps a bubble in a standing acoustic wave causes it to execute an oscillatory translational motion in the direction of gravity. A bubble driven below resonance will move up during the collapse phase and down during the expansion phase. A bubble translating and collapsing develops a jet in the direction of motion. It is hypothesized that sonoluminescence is due to the collision of this jet with the other side of the bubble surface. The mechanism of light emission is a ‘‘fracture’’ process of the liquid that initially cannot respond by flowing due to the very short rise time of the applied pressure. The picosecond duration of the light flash is the time it takes for the microjet overpressure to be relieved by reflection from the microjet free surface. Several other observed features of sonoluminescence (such as noble gas and temperature sensitivity, anomalous mass loss process, effect of surfactants) can also be explained, at least qualitatively. [Work supported by the Office of Naval Research.]
Sonoluminescence: Discussion of some new experimental results
Authors: Kondic Ljubinko , Chan C. K. , Yuan Chi
Published: October 2005

Recent experiments have achieved the single bubble sonoluminescence (SBSL) innondegassed water. Theoretical discussion of these new experiments is presented. First, the stability analysis of the radial bubble oscillations with respect to surface instabilities is given. It is found that the growth of unstable surface modes might be responsible for the experimentally observed oscillations in the SL emission. Second, the previously developed theoretical model is employed in order to explain these new experimental data for the SL radiation. This model is based on the production of the shock waves in a collapsing bubble. Furthermore, strong response of the intensity of the SL radiation on small changes of some of the experimental parameters is discussed. The agreement between the theory and the experiment is found to be very good, considering the complexity of the problem and a variety of physical and chemical processes involved. Finally, the methods for enhancing the effect of SL are discussed and the suggestions for further experimental and theoretical research presented. [Work partially supported by DOE.]
A new formulation of bubble dynamics for sonoluminescence
Authors: Yasui K.
Published: October 2005

A new model of bubble dynamics is constructed for the study of the recently discovered single-bubble sonoluminescence (SBSL). In the model, the effects of nonequilibrium evaporation and condensation at a bubble wall and that of thermal conduction both inside and outside a bubble are taken into account. Numerical calculations are performed under a condition of SBSL and that of non-light-emission. The most important point in this study is the calculation, including the effect of nonequilibrium evaporation and condensation at bubble wall for the first time in the studies of SBSL. The results reveal that the effect is considerable on bubble dynamics. It is clarified that the partial pressure of water vapor in a bubble differs considerably from the saturated vapor pressure at the collapse of the bubble. It is also clarified that the liquid temperature at the bubble wall increases considerably at collapse due to the thermal conduction and the latent heat of intense condensation. It means that chemical reactions take place not only inside a bubble but also outside a bubble. Rates of chemical reactions in a bubble are also numerically calculated including the effect. The results of this study are also important in the study of sonochemistry.
Temperatures of supersonic cavities
Authors: Fukushima Kenji
Published: October 2005

Among a variety of characteristic features of the sonoluminescence phenomena, especially interesting is how high temperatures can be reached by a supersonic cavity. It is widely believed now that high temperatures such as 105 K may be attained even under the experimental conditions of sonoluminescence. The dynamics of a supersonic cavity are simulated to determine the upper bound of temperatures reached by a gas content of the cavity. That is not to say that one should start with a realistic model to get quantitatively reliable results. To be specific, consider an air bubble in water. The compressibility of water, diffusion of air molecules through the bubble wall, condensation and evaporation of water, heat conduction, thermal radiation from a hot spot, phase transition from a gas to a plasma phase, and so on are taken into account. By use of the model, temperatures of the hot spot are calculated. Moreover, optimum values of supersonic parameters, i.e., amplitude and frequency, are searched for to get high hot-spot temperatures. Eventually the tendency is pointed out that the larger values of amplitude and in particular the smaller values of frequency are preferable to attain the higher temperatures. It is then concluded that there is a possibility of the temperatures reaching 106 K or more.
Tracking and glimpsing speech in noise: Role of fundamental frequency
Authors: Assmann Peter F.
Published: October 2005

Listeners with normal hearing can communicate successfully in noisy and reverberant conditions that distort temporal and spectral cues in the speech signal. Recent work has sought to identify auditory grouping processes that contribute to this ability. One property that has received attention is the fundamental frequency of voicing (F0). During voiced speech the pulsing of the vocal folds gives rise to a pattern of amplitude modulation in the waveform and harmonicity in the spectrum. When two or more voices compete for the attention of the listener, momentary differences in F0 can contribute to voice segregation in at least three ways. First, periodicity or harmonicity in the composite signal provides a basis for grouping together signal components that stem from a target voice. Second, waveform interactions generate moment-to-moment fluctuations in the signal-to-noise ratio that enable listeners to ‘‘glimpse’’ the acoustic features of the target voice. Third, time-varying changes in F0 provide a basis for tracking properties of the voice over time. The contributions of each of these processes to the perceptual segregation of speech from competing sounds will be reviewed. [Work supported by NIH/NIDCD.]
A simple grammar of auditory stream formation
Authors: Nakajima Yoshitaka , Sasaki Takayuki
Published: October 2005

A simple ‘‘grammar’’ is proposed to describe how ‘‘auditory subevents,’’ i.e., onsets, terminations, fillings, and silences, are connected perceptually. A rapid increase of sound intensity in a certain frequency range serves as a perceptual clue of an onset, whereas a rapid decrease serves as a clue of a termination. A thick distribution of sound energy for a certain duration in the time–frequency plane indicates a filling (or fillings), and a thin distribution of energy for a certain duration after a thicker part indicates a silence (or silences). The auditory system seems to interpret these clues according to the grammar, which allows three patterns of ‘‘auditory events’’: (1) an onset followed by a silence, (2) an onset and a filling followed by another onset, and (3) an onset, a filling, and a termination followed by a silence. Clearer clues and contexts facilitate the formation of auditory events. The proximity principle works when onsets and terminations are organized into an ‘‘auditory stream,’’ which is defined as a chain of auditory events and silences. Silences also obey the grammar. In order to avoid any violation of the grammar, the auditory system sometimes neglects or reuses clues of auditory subevents, or adds subevents.