bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of early reflection on players in a concert hall
Authors: Ueno Kanako , Satoh Fumiaki , Tachibana Hideki , Ono Takahiko , Senju Mariko
Published: July 2002

In order to investigate the effect of hall response on players, field measurements on the stage of a concert hall and laboratory experiment using digital simulation technique were performed. In the field experiment, the subject, a professional violinist, was asked to play and to make comments on her acoustical impression of five points on the stage. As a physical measurement, impulse responses were obtained at the same points by using omni-directional loudspeakers as a sound source and an omni-directional microphone and directional microphones as receivers. As a result, it has been found that not only the strength of the early reflections but also their direction influences the subject’s impression. In the laboratory experiment (anechoic chamber), the sound field was modeled and synthesized by using a 13 channel reproduction system; ambient reverberation judged as being natural was provided by simple digital reverberators and different strength and direction of early reflections were obtained by real-time convolvers. For a constant value of reverberation, several conditions with a different level and direction of the early reflections were created. For each condition, the violin player was asked to make similar judgments as in the field experiment. The results of two experiments were examined.
Two-tone suppression of the ultrasound induced startle response in a cricket
Authors: Farris Hamilton E. , Hoy Ronald R.
Published: July 2002

For the ground cricket, Eunemobius carolinus, frequencies >20 kHz elicit an acoustic startle response during flight. No startle responses are elicited by single pulses of low-frequency stimuli. However, simultaneous presentation of a low-frequency signal with ultrasound can suppress the startle response. The effect of frequency on suppression was measured for seven frequencies (3–9 kHz) at four intensities of the startle stimulus (40 kHz): 5, 8, 10, and 12 dB above startle threshold. Suppression was tuned to frequencies near 5 kHz. This effect of frequency on suppression diminished slightly at the higher ultrasound intensities, however. Because suppressor growth (change in suppression dB versus change in 40-kHz dB) was >1 for 5–7 kHz and >1 for 3 to 4, 8 to 9 kHz, equal suppression curves flattened at the highest ultrasound levels. Startle threshold decreases with increases in ultrasound duration, and temporal integration time constants were estimated to be 32 ms. In nonsimultaneous presentations, however, no suppression occurs when the suppressing tone is >2 ms after and >5 ms before the ultrasound stimulus. These times suggest that across-channel integration time is shorter than within-channel integration. [Supported by NIMH.]
Synchrony in cricket calling songs: Models of coupled biological oscillators
Authors: Forrest Timothy , Ariaratnam Joel , Strogatz Steve
Published: July 2002

Snowy tree crickets produce a rhythmic acoustic signal composed of short chirps. The chirp rhythms are very regular and dependent on temperature. When signaling in groups, males synchronize their chirps. The rhythmic signals of these tree crickets were used as a model of a ‘‘biological oscillator.’’ The phase responses of males to single probe stimuli similar to the male calling song were measured. The phase response curves (PRC) of males showed both strong (type 0) and weak (type 1) resetting. PRCs differed depending on amplitude, duration, and frequency of the resetting stimuli. In other experiments, males could adjust their natural periods by as much as 15% when phase-locking (1:1) to an entrainment stimulus. Signaling behavior of males was compared with a simple model of coupled oscillators. The phase resetting was not consistent with the simplest resetting model, in which the male’s phase shift is completed after one cycle of the chirp period. In addition, a simple iteration of the PRC could not simulate the phase-locking observed in the entrainment experiments indicating that the acoustic coupling between males differs from a simple resetting model.
Analysis of free bubble cloud scattering data from the Lake Seneca experiment
Authors: McDaniel J. Gregory , Roy Ronald A. , Gephart Andrew D. , Carey William M.
Published: July 2002

In the fall of 1991, Carey, Roy et al. conducted a series of experiments at the Seneca Lake test facility which measured the frequency-dependent scattering from submerged bubble clouds. Preliminary results reported by Roy et al. [J. Acoust. Soc. Am. 92, 2993–2995 (1992)] showed that certain features of the high-frequency backscatter data were consistent with single-bubble scattering while the low-frequency results were consistent with collective oscillations of the bubble cloud. A monopole resonance scattering peak was evident that scaled with the bubble cloud volume and the mixture sound speed. Additional analysis showed that the evolving target strength of the cloud as it rose through the insonating acoustic beam showed signs of an interference effect [Carey and Roy, Proc. 2nd Euro. Conf. on Underwater Acoust., European Commission, Luxembourg, 207 (1994)] which could explain the differences between calculated and measured scattering strengths. Advanced signal processing and modeling techniques have been developed to enable the removal of experimental artifacts caused by: (1) uncertainties in the range geometry, (2) coherent electrical noise in the processing electronics, and (3) acoustic reverberation within the test volume. The resulting corrected backscattering target strengths will be reported and discussed. [Work supported by ONR.]
High-intensity focused ultrasound transducer design for surgical and hemostatic applications
Authors: Keilman George W. , Kaczkowski Peter J.
Published: July 2002

A resurgence in interest in the application of high-intensity focused ultrasound (HIFU) to surgical problems is due in part to significant improvements in imaging modalities for targeting the delivery of ultrasound. The wide variety of potential applications under consideration necessitates a refinement of transducer design to accommodate often conflicting constraints. The need to deliver substantial power to a small target zone requires high focal gain to minimize collateral damage, and yet must be balanced with the need for small transducers in many procedures. In general, the choice of operating frequency, transducer aperture and focal depth, convenient acoustic coupling methods, waveform selection, and amplifier characteristics must all be adjusted to best fit the application. This presentation will discuss such tradeoffs in any HIFU transducer design, and will also address particular techniques for coupling and cooling transducers which deliver hundreds of watts of acoustic power. Transducer efficiencies of over 85% have been routinely achieved by judicious selection of matching layers and tuning networks, while maintaining over 50% relative bandwidth, for center frequencies spanning the range from 1 to 10 MHz. Transducer requirements for array-based systems, motivated by clinical needs, will also be discussed. [Work funded by DARPA/ONR.]
An image-guided ultrasound phased array system for noninvasive surgery
Authors: Ebbini Emad S. , VanBaren Philip D. , Simon Claudio
Published: July 2002

An integrated image-guided therapeutic phased array system for noninvasive surgical applications is being developed. The therapeutic array utilizes piezocomposite transducer technology and operates (therapeutically) at 1 and 2 MHz. It has 64 elements on a spherical shell with a geometric center at 100 mm from its apex. The array was shown to be capable of producing well-defined thermal lesions in tissue media at depths from 40 to 60 mm and to scan therapeutic foci up to ±15 mm from its geometric center. Image guidance is provided by a modified diagnostic ultrasound scanner which, in addition to providing standard B-scan images of the target region, provides real-time images of the temperature rise due to the therapeutic beam. The temperature information is obtained using a correlation based algorithm for echo displacement estimation, which can be directly related to local variation in tissue temperature due to the therapeutic beam. A complete description of the system will be given along with illustrative examples of image-guided tissue ablation and temperature estimation and control. In addition, experimental data demonstrating the use of the therapeutic array in an imaging mode will be presented. [Work funded by NIH Grant CA66602.]
MRI monitoring and control of focused ultrasound surgery
Authors: Hynynen Kullervo , McDannold Nathan , Fjield Todd , Daum Douglas
Published: July 2002

The clinical and animal tests of focused ultrasound surgery have shown significant variation between the effectiveness of the same power sonications. Therefore, it has become important to seek methods to monitor the in vivo ultrasound exposures. One of the most promising methods is the use of magnetic resonance imaging (MRI) to detect the temperature elevation. In this paper the calibration and accuracy of MRI thermometry will be presented. The in vivo mapped temperature distributions allow the thermal exposure of the tissue to be estimated. These estimates have been compared with the tissue coagulation produced in muscle and brain tissues in vivo. The results show that the lesion boundary is predicted with the resolution of the MRI voxels. This has significant clinical value since the MRI thermometry can be used to control the treatment on-line. These experiments allowed comparison of the accuracy of the theoretical models for predicting the temperature elevation and tissue necrosis in vivo. Similarly, the MRI thermometry was used to investigate the temperature buildup during multiple sonications and evaluate the performance of new applicators such as phased arrays in vivo.
Sound quality estimation using hearing sensation
Authors: Kim Soon-Hyob
Published: July 2002

This paper is on a study of objective sound quality estimation by using human hearing sensation. Until now, the sound quality estimation has been done by subjective methods by people. Unfortunately, it depends on environment and condition of the human ear. So it was difficult to tell exactly how sound quality was. This study was performed to make objective estimation of sounds, regardless of the factors. In this paper, six parameters were defined, which are related to the sound quality: loudness, sharpness, fluctuation strength, roughness, pleasantness, and annoyance, and signal processing methods for them were developed. In this way, a simulator was implemented that measures human hearing sensation. To prove objectiveness of the simulator, the simulator results were compared with subjective test results which were given by people. As a result, the average error rates were 8.1% in loudness, 12% in sharpness, 20% in fluctuation strength, 18.5% in roughness, 5.5% in pleasantness, and 19% in annoyance. The overall average error rate was 13.7%, which showed that the simulator is very useful.
Spectrum contrast and noise annoyance
Authors: Preis Anna
Published: July 2002

According to the computational view, the identification of a sound event by the auditory system consists of processing the information it extracts from the temporal pattern and frequency spectrum. The fine structure of the frequency spectrum facilitates, among other things, the determination of the relative amplitudes of the partials. The auditory system uses the values of these amplitudes to compute the total loudness of the sound event by summing the specific loudness of each partial across a set of critical bands. This correlates well with experimental data of perceived loudness. The present study investigates whether the auditory system makes use of other information contained in this spectrum. The tested hypothesis stated that the auditory system detects change in the relative amplitude of the partials. It was assumed that these changes can be traced in experimental data of perceived annoyance of noise. The experimental results show that the best correlation between the reported annoyance and calculated values was obtained for the average absolute value of the second derivative of the weighted specific loudness calculated as a function of the critical-band rate scale. This specific loudness was weighted by the function introduced in sharpness calculation [W. Aures, Acustica 59, 130–141 (1985)].
Detection and discrimination of amplitude-modulated signals in noise
Authors: Chung King , Zeng Fan-Gang , Wright Beverly A.
Published: July 2002

Comodulation masking release demonstrated improved detection of pure-tone signals in amplitude-comodulated noise bands [Hall et al., J. Acoust. Soc. Am. 76(1), 50–56 (1984)]. However, in most real-world situations, signals such as speech sounds are comodulated and noises such as cocktail party and traffic noises are not. Two experiments were designed to examine whether comodulation of signals can lead to improved signal detection in noise. Experiment I used a 2AFC method to measure detection threshold of a 2/3-oct-spaced, five-tone complex in pink noise. The complex tones were either amplitude comodulated or randomly modulated. Results from three normal-hearing listeners showed no difference in detection threshold between amplitude-comodulated and randomly modulated conditions. Experiment II used a method of constant stimuli to measure the psychometric function of discriminating six vowel-like stimuli in pink noise. These vowels consisted of three formant-frequency sinusoids which were unmodulated or amplitude-comodulated or randomly modulated by a 125-Hz sinusoid simulating the voice pitch. While no difference was observed between comodulated and randomly modulated conditions, the psychometric function for the nomodulation control condition was shifted by 4–6 dB toward lower signal-to-noise ratios. A possible explanation is that auditory fibers phase-lock to formant-frequencies of the unmodulated stimuli and to the fundamental frequency of the modulated stimuli.
Attention, rhythmicity, and expectancy
Authors: Jones Mari Reiss
Published: July 2002

It seems plausible that body gestures created by ourselves and other living things may derive from some underlying periodic processes. Motor rhythms are ostensibly measurable. The case for attending having a rhythmic aspect is more challenging, in part because attention is not directly observable. So the question is asked: ‘‘How does an approach that posits internal (nonobservable) oscillators actually explain attention?’’ Three steps are considered. The first considers that attending primarily involves selectivity. Visual attention theories often relate selectivity to space; attention is focused at one place not another. Significantly, few theories of auditory attention exist. But surely in speech and music, attention can operate selectively in time; it can be targeted to one temporal location, not another. The second step requires that nonlinear oscillators describe selective attending in time. That these models deliver is evident in several recent oscillator models, including an elegant one developed by Ed Large. Step three involves connecting oscillator activities to measurable behaviors that reflect attending. Listeners are primed with auditory patterns, only some of which display rhythms predicted to facilitate temporal expectancies accounted for by oscillator entrainment. The talk centers on these experiments, their outcomes, and implications for a theory of dynamic attending.
Models for entrainment of neural rhythms
Authors: Baird Bill
Published: July 2002

Psychological results suggest that motor and perceptual behavior are organized by neural rhythms with periods from seconds to tenths of a second. It appears that their entrainment to external speech and music or to internal motor coordination rhythm is essential for effective performance. It is proposed that theta-alpha sensory-motor cycles (5–15 Hz) form the basis of these rhythms. They generate and entrain rhythmic motor output or temporal perceptual expectancies. It is hypothesized that cortical EEG and event-related potentials (ERPs) reflect thalamic biasing currents. The cortical evoked potential is a 5–15 Hz signal whose peaks and troughs correlate with stages of cortical information processing in sensory-motor tasks. Cortical rhythms are found in visual, auditory, and somatosensory areas as well as the hippocampus and reticular system that entrain to periodic inputs. If the arrival of an auditory stimulus is regular, it has been shown that 5–12 Hz auditory activity becomes phase locked in advance of the target stimulus to the expected arrival time. Our model of rhythmic expectation accounts for this since the theta-alpha rhythmic cycles constitute a fast clock that adjusts phase and frequency to match stimulus arrival, and longer period cycles are derived from this base clock.
Implementation of real-time acoustic communications systems
Authors: Herold David , Nation Robert , Edelson Geoffrey , Will Eric
Published: July 2002

Over the past several years, the field of underwater acoustic (UWA) communications has been focusing on bandwidth efficient phase coherent modulation techniques. In this application, practical communication algorithms, and thus their implementations, are still maturing. In addition to the computer-intensive algorithms used to track and decode these acoustic data, the systems may incorporate compression, coding, and error-detection schemes to provide usable communication links. Several programs are currently underway to utilize these developments in fieldable systems. In this paper, an overview of the signal processing requirements for UWA communications is provided, as well as some constraints placed on these systems by specific applications. The effect of these requirements on overall system design and implementation is outlined.
An adaptive processing structure for integrated active-passive sonars deploying cylindrical arrays
Authors: Dhanantwari Amar C. , Stergiopoulos Stergios
Published: July 2002

The paper details the development and implementation of an adaptive processing structure for integrated active–passive sonars deploying cylindrical arrays. The main concept includes decomposition of the computationally intensive multidimensional beamformer into two simple modules, which are line and circular array beamformers. Thus, the multidimensional beamforming process can now be divided into coherent subprocesses which lead to efficient implementation in real-time sonar systems. Furthermore, the application of spatial shading to reduce the side-lobe structures can now be easily incorporated. Moreover, the new approach makes the implementation of adaptive schemes in multidimensional sensor arrays practically achievable. The proposed adaptive processing concept has been implemented in an integrated active–passive real-time sonar deploying a cylindrical array. Real data results from the adaptive and conventional beamforming outputs of the cylindrical array sonar system demonstrate the superior performance of the adaptive beamformer in suppressing the reverberation and cluttering effects in active sonar applications. Moreover, for passive sonar applications, the adaptive processing provides substantially improved angular resolution performance as compared with that of the conventional beamformer. Both these two performance improvements for a cylindrical array sonar are of particular importance for mine hunting operations.
Sound ranging of impulsive sources in air
Authors: Ferguson Brian G.
Published: July 2002

A passive sound ranging method based on wavefront curvature is described where the impulsive sound of a rifle firing is received at three spatially separated collinear sensors. Estimating the differential time-of-arrival (or relative time delay) of the acoustic wavefront at each pair of adjacent sensors enables the range and bearing of the source to be estimated. The temporal variability in the polar coordinates of the source is presented for real data and the system errors affecting the accuracy of the measurements are discussed. The time delay estimation technique is then applied to the passive ranging of an impulsive sound source located in the far field, where the wavefront curvature technique is no longer appropriate as the arriving wavefront is planar. For the plane-wave arrival case, the range of the sound source is estimated from the angle-of-arrival estimates at two widely spaced known locations. The source position estimated by the acoustic method is compared with the source position determined by standard surveying methods. The nonstationary behavior of the sound propagation medium leads to variability in the source localization parameters which is presented for the acoustic data collected during artillery firings.
Pulse propagation in random media
Authors: Dacol Dalcio K.
Published: July 2002

Wave propagation in randomly fluctuating media is a problem of continuing interest in ocean acoustics. Usually the work done in this field is carried out in the frequency domain since there are powerful techniques to study wave scattering in the frequency domain, while time-domain formulations are notoriously more difficult to use and obtain results. Nevertheless, our intuition about wave phenomena is much better when discussing such phenomena in a space-time formulation than in a space-frequency formulation. In this presentation wave propagation in a weakly and randomly fluctuating medium is discussed entirely within the space-time formulation. McDonald and Kuperman derived from the wave equation an approximate time-domain progressive wave equation which is the equivalent in the space-time formulation of the well-known parabolic wave equation in the space-frequency formulation. A path integral representation for the solution of this equation is used here to study wave propagation in random media. The weakly inhomogeneity assumption yields an approximate evaluation of the path integral for the Green’s function thus allowing an analysis of the time-dependent statistics of acoustic fields propagating through random media. [Work supported by ONR.]
Elimination of branch cuts from the normal mode solution using gradient half-spaces
Authors: Westwood Evan K. , Koch Robert A.
Published: July 2002

A method for eliminating the branch cuts and branch line integrals from the normal mode solution to the range-invariant acoustoelastic wave equation has been developed and implemented. In the usual normal mode formulation, evaluation of the vertical wave number in the ocean waveguide’s lower half-space involves a square-root operation and gives rise to a branch point at the critical angle. When the Pekeris cut is chosen, energy steeper than the critical angle is represented by leaky modes, and lateral-wave energy near the critical angle is represented by the branch line integral. When a mode lies near the branch cut, the branch line integral can be significant at all ranges. Branch line integrals are cumbersome to compute, and, for range-dependent problems, cannot be included in adiabatic and coupled-mode algorithms. By inserting a (small) positive attenuation gradient in the lower half-space, the plane wave solution is replaced by a complex-valued Airy function solution, the branch point is eliminated, the Pekeris branch cut is replaced by a series of modes, and the leaky modes become bounded at infinite depth. Implementation and applications of this approach using the normal mode model ORCA are given. [Work supported by ONR 321OA.]
Improving a practical broadband adiabatic normal mode model by including untrapped modes
Authors: Koch Robert A. , Westwood Evan K. , LeMond Julienne E. , Knobles David P.
Published: July 2002

An adiabatic normal mode model that neglects untrapped mode contributions will give inaccurate transmission loss predictions for environments with bottom slopes when modes transition between being trapped and untrapped. For example, initially untrapped, but strongly excited, modes that subsequently become trapped away from the source may contribute significantly to water column fields. Results of Tindle and Zhang [Oceans ’93 Proceedings, I-81] show that including untrapped modes in an adiabatic description significantly improves transmission loss predictions for the ASA benchmark wedge problem. A practical implementation of an adiabatic broadband propagation model for both trapped and untrapped modes will be described. Difficulties associated with the transition region between trapped and untrapped modes near the critical angle will be discussed, and the results of inserting a gradient in the lower half-space to solve the problem will be presented. [Work supported by ONR.]
Application of adaptive filter in influence extraction
Authors: Veerabhadraiah S.
Published: July 2002

The very-low-frequency ocean ambient noise changes from place to place and time to time drastically due to various factors like thermal agitation, sea state, traffic, seismic factors, and biological activity, wind speed, etc. The surface and underwater mobiles generate an influence signal within the same frequency band of ambient noise but with extremely low magnitude. The influence signal gets buried in the high ocean ambients, yielding an extremely low signal-to-noise ratio, and are as such indistinguishable in the original time traces. In certain applications, perfect localization of such mobiles is extremely essential for extracting the influence signal buried in ocean ambients. This can be done using a self-optimizing adaptive filter known as a LMS (least mean square) filter. The filter automatically adjusts its parameters with the arrival of each new ambient sample with a superior convergence rate at an appropriate step size. This technique, discussed in the paper, has been developed and successfully implemented to extract the desired signal from high ambients. Some sample graphical outputs depicting a combination of signals buried in ambient and extracted signal at the filter output. Necessary theory, a flowchart for implementing the LMS algorithm, and hardware realization of the same are also included in the paper.
Backscattering by layered media: Modeling and comparison with data
Authors: Guillon Laurent , Lurton Xavier
Published: July 2002

Deep-water multibeam echosounders provide bathymetry data and acoustical images, the latter being sometimes difficult to interpret. Indeed, due to the size of the wavelength used (about 10 cm), the wave’s penetration into the seafloor is not negligible and the internal geological structure of the seafloor must be taken into account in the acoustical modeling. A model for backscattering by layered media is proposed here for trying to explain the acoustical response of such geological configurations. It is based on the concept of ‘‘equivalent input backscattering strength’’ through a multilayered stratified lossy medium. Each fluid layer may feature a continuous variation in acoustical parameters (sound velocity, density, and attenuation) and generates volume backscattering. The backscattering strengths provided by the sediment finite volume and by an underlying basement are affected by various effects inside the upper layer stack : refraction, attenuation, and interferences. Synthesizing the classical approaches of backscattering (interface and volume) and transmission in layered media, this model allows one to discuss the various components and effects featured in the resultant backscattering strength. It is finally compared to acoustical data recorded in areas where some ground truth is available.
Subcritical penetration into a viscoelastic solid due to interface roughness: Laboratory experiment and perturbation theory model
Authors: Mellema Garfield R. , Ewart Terry E. , Williams Kevin L.
Published: July 2002

The propagation of acoustic energy into sub-bottom sediments at grazing angles below the compressional critical angle has been well documented and various mechanisms to explain this propagation have been proposed. Due to the complexity of the in-situ environment the propagated energy might not be the result of a single mechanism, but a sum of a combination of several mechanisms. In order to better consider the validity of one of the more prominent mechanisms, rough surface scattering, a simplified laboratory environment has been constructed in which to make measurements of penetration due to interface roughness. In this environment, the sediment has been replaced by a homogenous viscoelastic solid. To preserve the uniformity of the solid, both the transmitter and the receiver are located in the water column, where their radiation patterns are well characterized. Use of an automated positioning and measurement system and a large interface area ensures that the series of measurements are both repeatable and statistically meaningful. A perturbation theory model has been constructed for comparison with the measurements. In the experiment its accuracy is evaluated as the surface roughness is increased through the limit of perturbation theory. [Work supported by ONR.]
Vibration isolation design for Benaroya Hall
Authors: Wilson George P.
Published: July 2002

Location of the new Seattle Concert Hall, Benaroya Hall, directly over an existing Burlington Northern railroad tunnel required development of a very effective vibration and noise isolation system. The first step in the design was to measure the ground-borne vibration and noise levels from trains via boreholes at the site and in the basement levels of nearby buildings located over the tunnel. From the measured vibration, the expected sound level in the performance space was projected for comparison with the criterion established for acceptable level and inaudibility. This comparison determined the amount and frequency range for the reduction required. The degree of reduction of structure-borne noise required determined that the design required two parts, a massive foundation mat for coupling loss and an isolation system with 4-5 Hz effective natural frequency and full reduction over a wide frequency range. Achieving the needed attenuation required a structure with very high mechanical impedance and isolators which provide a low acoustical impedance over a broad frequency range, leading to the use of heavy concrete structure and natural rubber isolation bearings. Details of the design parameters and materials are presented along with results from measurements with the completed isolation system and partially completed hall.
Three-dimensional computer modeling of biosonar emission in the common dolphin
Authors: Aroyan James L.
Published: July 2002

Several delphinid species are known to possess a highly sophisticated and adaptable biosonar system, yet the exact acoustic mechanisms involved in signal generation, emission, and reception remain poorly understood. Recently, a novel computational approach was utilized in an investigation of the acoustical mechanisms of dolphin biosonar. Three-dimensional acoustic simulation techniques and a new method for mapping acoustic tissue properties from x-ray computed tomographic data were applied to models of the forehead and lower jaw tissues of the common dolphin, Delphinus delphis. This approach proved highly effective in studying the detailed processes of biosonar emission and reception in this animal. The results of the investigation which concern the emission system of this dolphin will be presented. These results include: (1) the common dolphin’s skull plays the predominant role in beam formation; (2) the melon contributes significantly to narrowing of the emitted beams; (3) the melon behaves as a waveguide and a lens in the biosonar signal emission process; (4) the results of both inverse simulation and forward extrapolation programs suggest that the biosonar signal source tissues lie within a small volume of the soft tissues of the right nasal passageway.
Matched-field processing of baleen whale vocalizations using calibrated environmental models
Authors: Thode Aaron M. , D’Spain Gerald L. , Kuperman William A.
Published: July 2002

During the 1997 Marine Mammal Vocalization (MMV) experiment conducted by the Scripps Marine Physical Laboratory last September, J15 source tows were conducted in a highly range-dependent environment northwest of San Nicolas Island in the Southern California Bight region. The tows consisted of eight radial tracks ranging from 1 to 6 nautical miles from the research platform FLIP, along all cardinal directions. Among the signals broadcast were low-frequency combs (18–110 Hz), middle-frequency combs (50–200 Hz), FM downsweeps (900 to 50 Hz over 9 s), and an Eastern Pacific type A blue whale recorded during the 1996 MMV experiment. Multiple CTD casts were also taken, and a bathymetric database was obtained from the National Oceanographic Service. All these data are used to calibrate matched-field processing environmental models, which are subsequently applied to find the location in 3D space of a series of blue whale vocalizations. [Work sponsored by ONR.]
Feasibility of monitoring bowhead whales with a vertical line array
Authors: Heaney Kevin D. , Mikhalevsky Peter N.
Published: July 2002

As part of the ACOUS trans-Arctic acoustic propagation experiment, a vertical line array will be deployed off Pt. Barrow, Alaska in the summer of 1998. The array will be cabled to shore and will be capable of real-time recording of acoustic frequencies from 20 to 500 Hz. This array will provide scientists the opportunity to record bowhead whale songs in real time from hydrophones spanning the water column. Currently, the bowhead whale census is taken during the spring migration from the edge of ice leads. The feasibility of doing a Fall census, when the sea is relatively free of ice, will be presented. Recordings of bowhead whale songs, and simulations of localization using the vertical array will be presented. Using varying bathymetry and sono-buoys, to add to the horizontal resolution of the array, 3D localization of vocalizing whales should be possible.
Enhancement of ultrasound-mediated transfection with cavitation micronuclei
Authors: Greenleaf James F. , Bolander Mark E.
Published: July 2002

Many methods are available for transferring foreign genes into mammalian cells (transfection). The advantages of ultrasound-mediated transfection are that it can be controlled in both space, by focusing, and time, by exposure. It was tested whether ultrasound-mediated gene transfection in cultured immortalized human chondrocytes would be enhanced using artificial cavitation nuclei in the form of Albunex®. Here 1.0 MHz ultrasound transmitted through the bottoms of six-well culture plates containing media with green fluorescent protein reporter gene plasmids at a concentration of 40 μg/ml and Albunex® at 50×106 bubbles/ml produced a peak transfection efficiency of about 50% of the living cells when exposure was 4×105 P spatial average peak pressure (SAPP) for 20 mins. Using these parameters, transfection efficiency increased linearly with ultrasound exposure pressure with a transfection threshold observed at a SAPP of 105 P. Adding fresh Albunex® at 50×106 bubbles/ml prior to sequential one second 3.2 or 4.0×105 P exposures increased transfection efficiency by 15% for each of three consecutive exposures. Efficient in vitro and perhaps in vivo transfection appears possible with ultrasound providing both temporal and spatial control over the transfection process.
Defects of bilayers generated by ultrasound
Authors: Malghani M. S. , Yang Jie , Wu Junru
Published: July 2002

Transdermal drug delivery is handicapped by the low skin permeability caused by highly ordered structure of lipid bilayers in the outer human skin layer. It has been reported that ultrasound can increase the permeability of human skin [S. Mitragotri, D. Blankschtein, and R. Langer, Science 269, 850–853 (1995)]. The enhancement was attributed to acoustic cavitation but the underlying physical mechanism is not fully understood. As a model, dipalmitoylphosphatidylcholine (DPPC) lipid bilayers are insonicated by ultrasound of two submegahertz frequencies (168 and 707 kHz). The free-field spatial peak pressure amplitudes of both are measured to be 6×105 Pa. Bilayer defects, which have average diameters of tens to hundreds of nanometers and can be detected by an atomic force microscope, are generated within less than 0.5 min. The number of the defects grows with time. The defect growth rate at the 168-kHz frequency is about 3.5 times that at the 707-kHz frequency.
Design and properties of face to face couplers for microphone comparison calibration
Authors: Frederiksen Erling
Published: July 2002

This paper describes the design and properties of microphone comparison calibration couplers. In 1988 Bruel and Kjaer introduced a sound level calibrator with a built-in reference microphone which, via a feed-back system, controls the sound pressure in its coupler cavity. This was a significant step in the direction of more stable calibrators. The same calibrator presented another new principle. The microphone to be calibrated and the reference are placed face to face in such a short distance that their diaphragms see essentially the same sound pressure which is produced by a rotational symmetrical source. This mounting was found to improve the accuracy and to increase the upper frequency limit of the new calibrator by more than five times in comparison with previous calibrator configurations. Today IEC-TC29 prepares an international standard for comparison calibration of working standard microphones. The method of this standard uses the special symmetrical mounting of the source and the microphones. The paper describes results obtained with some experimental couplers which are made in this connection in order to analyze the calibration accuracy and optimize the frequency range. The couplers are mainly intended for comparison of sensitivity magnitude but may also be used for comparison of phase response characteristics.
Influence of the weight of mutes on tones of a violin family
Authors: Kishi Kenshi
Published: July 2002

The phrase ‘‘con sordino’’ is used for the score of a violin family to indicate the use of a mute. The mute is used to reduce the volume of the violin tones and change their tone quality. This paper examines the influence of the weight of mutes on tones of a violin using the spectral envelopes of the violin tones. Violins with and without mutes were played by a skilled player in an anechoic chamber to produce tone samples which were then recorded on a DAT recorder. Using the tone samples, the time variances of the fundamentals and spectral envelopes obtained by FFT analyses were examined. The force transfer function of a cello bridge with mutes installed, which is used for convenience, was measured. From these examinations and analyses, we made the following observations: (1) the higher the order of harmonics, the lower their relative sound pressure levels compared with that of the fundamental and (2) the level differences between the peaks and dips of the spectral envelopes are reduced as the weight of a mute is increased.
Behavior of real violin strings, mechanically bowed
Authors: Pickering Norman C. , Kerr Michael P.
Published: July 2002

Traditional methods of evaluating various types of strings for bowed instruments have relied almost exclusively on subjective impressions of expert players. In the real world, busy professionals rarely have enough time or objectivity to provide string designers and manufacturers with precise information. Furthermore, such opinions are affected by factors unrelated to the stings themselves, and are subject to change in ways that are often difficult to relate to the design details of the product being tested. The use of a well-designed bowing machine makes it possible to amass quantities of data on specific strings, enabling string makers to discover the characteristics that are favored by professional artists. Data is obtained for strings having cores of gut, synthetic polymers, monofilament, and stranded steel. By varying bow force, velocity, and distance from the bridge an envelope of usable combinations is accurately determined. Time for development of Helmholtz waveform partial by partial, average frequency variation as well as cycle-by-cycle period variation, and overall spectral distribution can all be determined with good repeatability. Driving strings magnetically instead of by bowing permits frequency determination of individual partials, an indication of string flexibility or lack of it. This work has led to new string designs, incorporating new materials and manufacturing processes.
A new way of reducing self-sustained flow noise
Authors: Henry Reni A. , Sakout Anas , Coiret Alex L. , Hamdouni Aziz
Published: July 2002

Vortex shedding from shear layers may be driven by the resulting acoustical field. In order to achieve noise reduction, the feedback loop is broken down with the help of auxiliary secondary flows that are created by means of minor geometrical modifications. Experiments have been conducted on a flow through two close orifice plates in a cylindrical duct: they have brought forward the possibility of reaching stable paths of flow bifurcations where an important noise reduction is obtained in a large range of flow rates. By creating a suitable interaction between the main shear layer of the confined jet and thin auxiliary shear layers, noise reduction takes place in a range of 20–40 dB. The latest result is the following: due to the stability of the flow bifurcation path that can be reached, such a level of noise reduction is maintained in a large range of flow conditions. Moreover, by choosing an adequate path, noise reduction takes place for flow conditions where intense tones would be present if these flow conditions were to be reached through conventional means. It may be emphasized that such methods are costless, compared to some sophisticated active control methods.
Identification of sources of tire/pavement interaction noise
Authors: Ruhala Richard J. , Burroughs Courtney B.
Published: July 2002

Although most highway noise is due to radiation from rolling tires, the dominant sources of tire/pavement interaction noise remain largely unknown. In this study, near-field acoustical holography (NAH) is used to visualize the acoustic field of a rolling tire on outdoor pavement surfaces. Since NAH measurements are conducted in the near field, areas of maximum radiation from the tire may be localized with a much finer resolution than with conventional measurements. Planar NAH is used to scan planes along the side, front, and rear planes of the tire. A scanning mechanism will be attached to an automobile trailer for measurements of tire noise under realistic conditions and procedure as developed in earlier results [R. J. Ruhala and C. B. Burroughs, SAE 972047 (1997)]. Several types of tires are evaluated, including blank tire, tire with even spaced transverse grooves, tire with only circumferential grooves, and a production passenger car tire. The tires are tested on both smooth and rough pavements, and at several speeds. The results will provide further insight into the sources and mechanisms of tire/pavement interaction noise. [Work supported by Goodyear, DOT, and GM.]
Modeling of tangential contact forces
Authors: Larsson Krister , Barrelet Stephane , Kropp Wolfgang
Published: July 2002

The main noise source from vehicles at speeds greater than 50 km/h is the tires. To reduce traffic noise it is therefore necessary to understand the noise generation mechanisms in the contact between tire and road. The paper presents an improvement of an earlier developed acoustic rolling model concerning a smooth tire rolling on a rough surface. This model consists of three steps. First, the radial contact forces between road and tire are calculated. These forces give the vibrations of the tire, which finally give the sound radiation from the tire. A method to include the tangential forces into the rolling model is the topic of this paper. To do this, the influence of the tread blocks on the force transmission from the road to the belt of the tire has to be known. A FEM-model of one tread block is made in order to determine its dynamical properties. A simplified model of the block is established, by only taking into account the two lowest modes in the frequency range of interest (i.e., up to 3 kHz). This simplified model is included in the existing contact model to give the response of the tire due to tangential or radial excitations.
Instrumentation for the measurement of occupational noise exposure: Past, present, and future
Authors: Kuemmel Theodore J.
Published: July 2002

The instruments used to measure occupational noise exposure have all evolved from the basic sound level meter. Variation of the sound fields and the dynamics of the measurement environment raised questions about the validity and accuracy of occupational noise exposure measurements. Measurement practice and instrumentation have evolved significantly to overcome the limitations inherent in the measurement of sound levels. Modern microprocessor based instruments which automatically compute noise exposures have dramatically improved the validity and accuracy of occupational noise exposure measurements. Today many of the measurements of occupational noise exposure can be reliably replicated. This paper addresses the challenges faced when attempting to assess occupational noise exposure, and their influence on the development of occupational noise exposure measurement instrumentation. The influence of technology, regulation, and standards on instrument development is also addressed.
Sound exposure profiling: A noise exposure assessment alternative
Authors: Hager Lee D.
Published: July 2002

Assessment of worker sound exposure based on incremental task sound levels has a history dating back to the earliest days of recognition of noise as a hearing hazard. Sound exposure profiling (SEP) uses current technology to compile task-based sound measurements to model long-term risk of exposure to hazardous noise. SEP is an alternative to full-shift dosimeter techniques for sound exposure assessment. The methodology offers the advantage of providing additional information about noise sources and how worker interaction with noise sources results in long-term risk of exposure. SEP has been adopted by several major corporations as their corporate strategy for assessment of worker noise exposure, and is supported in ANSI S12.19-1996, ‘‘Measurement of Occupational Noise Exposure.’’ This paper will described SEP and its application in industry.
Sonochemistry of aqueous solutions: EPR and spin trapping studies of radical intermediates
Authors: Riesz Peter , Misik Vladimir
Published: July 2002

The primary free radical species produced in the sonolysis of aqueous argon-saturated solutions (i.e., H, OH, and O2–) and in N2-containing aqueous solutions (H, OH, O2–, NO) can be identified by electron paramagnetic resonance (EPR) combined with spin trapping. The EPR experiments using cadmium(2+) ions as hydrated electron scavengers show that no detectable level of hydrated electrons is formed in the sonolysis of argon-saturated water at neutral pH. The temperature dependence of the semi-classical treatment of the kinetic isotope effect for H and D formation by O–H and O–D bond scission in 1:1 H2O–D2O mixtures was used to estimate the effective temperatures (2000–4000 K using phenyl t-butyl nitrone spin traps) in collapsing cavitation bubbles. At low concentrations of nonvolatile solutes (e.g., acetate ions, amino acids, and sugars) only radicals formed by H-abstraction were observed. At high concentrations, pyrolysis radicals such as methyl radicals from acetate, amino acids, and sugars could also be spin trapped. For volatile organic solutes, the effect of the vapor pressure of the solute on the effective value of gamma (the ratio of Cp/Cv) in the cavitation bubble is the major determinant of radical yields.