bluuebunny/crossref_metadata_2025 huggingface dataset:
Response-related patterns in discrimination of FM narrow-band noise
Authors: Qian Jinyu , Richards Virginia
Published: October 2013

Noise stimuli were used to investigate weighting patterns for detecting dynamic frequency changes. For one stimulus set, a tonal glide was modulated by a narrow band of noise (gliding narrow-band noise, GNBN, condition). For the second set, the glide was preceded and followed by steady-state tones before modulation (SS condition). The task was to indicate whether the stimulus had a frequency glide or not. Weighting patterns (as a function of time) were derived for each subject based on a linear classification model. First, the deviation of the instantaneous carrier for each stimulus was calculated and then weighted by the squared envelope of the stimulus. This was followed by the linear classifications of the squared-envelope-weighted deviation of instantaneous carrier (SEWDOIC) according to the subjects responses [A. Ahumada, J. Vis., 2, 121–131 (2002)]. The weighting patterns were consistent across subjects although individual differences in pattern details were observed. The comparison between the patterns from the GNBN and SS conditions indicates the use of dynamic information rather than only comparing the beginning and ending frequencies, consistent with Lyzenga et al. [J. Acoust. Soc. Am. 116, 491–501 (2004)]. Similar weighting patterns were also estimated when the center frequency of the stimuli was random.
Suppression of sports chants through delayed feedback of sound
Authors: van Wijngaarden Sander J. , van Balken Johan S.
Published: October 2013

A novel approach for disrupting offending chants at sporting events is proposed, based on attacking synchronization between individuals. Since timing is crucial for coordination between chanters, disruption of timing is expected to be effective against chants. Delayed auditory feedback is known to disrupt timing in individuals; hence, delayed feedback may also be effective in a group context. It is shown that the timing of individuals joining in with sports chants can be severely disrupted by also presenting an artificially delayed version of this chant. This effect is reduced if the individual is given more cues (direction, fidelity) to differentiate between original chant and distracter. Unsurprisingly, the effectiveness also depends on delay time and the target-to-distracter ratio. The feedback signal has to be at least as loud as the original chant, and the delay should be greater than 200 ms. Conventional auditory feedback shows a pronounced peak in effectiveness around 300 ms. Such a peak does not occur here; up to approximately 1 s, effectiveness increases monotonically with delay time. Field experiments show that it may be hard to implement the approach suggested here in practice, since the required feedback signal levels tend to lead to instability of the feedback loop.
Nondestructive inspection of in-service pipelines by guided ultrasonic waves
Authors: M. Tavossi Hasson
Published: October 2013

Ultrasonic techniques for inspection of pipelines are investigated, using them as channels for guided ultrasonic waves. The current standard method for pipe inspection requires sending a rotating probe inside the pipe and measuring the wall thickness by pulse-echo technique. The inside wall of the pipe should therefore be accessible, clean, and smooth. These requirements limit the applicability of this method. The inconvenience of the above method can be removed by the guided wave technique that uses the pipe itself as a waveguide. In the guided wave technique the waves are not reflected from the inside surface of the pipe and they do not have the restrictions mentioned above. It is well known that dispersion of ultrasonic guided waves occurs in the wall of the pipe. As the waves propagate along the length of the pipe, different modes travel at different speeds. Selection of an appropriate mode for the transmitted waves is used to detect various flows in the pipelines. These flaws include wall thinning, pitting by corrosion, or cracks. High-frequency ultrasonic transducers in the range of 10 to 20 MHz are used for this purpose. Theoretical results are discussed and compared with the experimental findings on the ultrasonic nondestructive in-service pipe inspections.
Time-reversal imaging for structural monitoring
Authors: Derveaux Gregoire P. , Papanicolaou George , Tsogka Chrysoula
Published: October 2013

We investigate time-reversal imaging with distributed sensors in order to locate localized damage in a structure. Given a configuration of transducers, we assume that a full response matrix for the healthy structure is known. It is used as a basis for comparison with the response matrix that is recorded when there is damage. We have carried out a numerical experiment with the wave equation in two dimensions. The healthy structure is a domain containing many scatterers. We want to image two pointlike defects with the help of 12 sensors regularly distributed. Because of the complexity of the environment, the traces have a lot of delay spread and travel time migration does not work well. Instead the traces are back-propagated numerically in the medium, assuming that we have some knowledge of the background. Since the time at which the back-propagated field will focus on the targets is unknown, we compute the Shannon entropy of the image and pick the time where it is minimal. The TV norm proves also a good indicator. Thanks to the superfocusing property of time reversal in a highly scattering medium, this algorithm works well: it gives reliable and stable results.
Noise robust bandwidth extension of telephone speech for mobile and landline communications
Authors: Sathyendra Harsha M. , Uysal Ismail , Harris John G.
Published: October 2013

The present day telephone infrastructure limits the bandwidth of telephone speech to 300–3400 Hz, whereby conversational speech falls mostly within 50–8000 Hz. The ensuing band-limited narrow-band (NB) speech has a considerable loss in sound quality, in terms of naturalness and intelligibility. The purpose of bandwidth extension (BWE) is to utilize the receiver end NB speech and to add relevant frequency information to the missing low and high frequencies. This novel BWE algorithm utilizes the linear source filter model, which separates NB speech into two roughly independent components, the excitation and the spectral envelope. These components are then extended and convolved together to attain reconstructed wideband (RWB) speech. Excitation extension involves harmonic reconstruction for voiced frames and some modulations and filtering steps for unvoiced frames. Spectral envelope extension utilizes a Gaussian mixture model trained via the expectation maximization algorithm, which is involved in the mapping of NB noise robust features to the corresponding RWB features. Noise analysis is used to isolate the best feature set for real world applications. Results from a subjective listening test indicate this algorithm has an improvement in sound quality, while having the lowest known distortion metric among other speaker independent bandwidth extension algorithms.
Detection of vowels in long-term speech-shaped noise
Authors: Liu Chang , Eddins David A.
Published: October 2013

The method of calibration is a critical issue in studies of vowel identification in noise, especially when manipulating speech-to-noise ratio. Common methods focus on stable estimates of the intensity or sound pressure level for specific speech sounds. However, vowels with the same sound pressure level often differ in both loudness, when presented at supra-threshold levels, and audibility, when masked detection thresholds for the vowel stimuli are measured. In the present study, detection thresholds for 12 isolated American-English vowels naturally spoken by three male and three female talkers were measured for young normal-hearing listeners in the presence of a long-term speech shaped (LTSS) noise. The duration of the vowels was equalized to 170 ms. The spectrum of the LTSS noise was identical to the long-term average spectrum of a 12-talker babble. The LTSS noise was present at 70 dB SPL. Thresholds for vowel detection showed distinct pattern as a function of the vowel category that was similar across listeners and talkers. This indicates that certain vowels were more audible than others, regardless of listeners and talkers. To account for the vowel-detection thresholds in noise, various analyses including comparisons of excitation patterns and estimates of specific loudness will be considered.
Enhancement of spectral modulation frequency in acoustics and identification of vowels
Authors: Eddins David A. , Liu Chang
Published: October 2013

The pattern of intensity variations across audio frequency can be represented as a series of spectral modulation frequencies. Selectivity for spectral modulation frequency in the auditory system has been demonstrated by physiological and psychophysical studies, suggesting that auditory perception of complex sounds might be based on spectral envelope channels. The present study investigated the effects of enhancing spectral modulation frequency on vowel acoustics and vowel identification. Twelve naturally spoken American-English vowels by three female talkers served as the standard stimuli. Various spectral modulation frequency regions of the standard vowels combined with a long-term speech-shaped (LTSS) noise were enhanced. Identification performance for the vowels presented in LTSS noise with and without spectral modulation frequency enhancement was estimated for seven young normal-hearing listeners. Vowels were presented at a sensation level of 3 dB in the LTSS noise (70 dB SPL). Results indicated that vowel identification performance was improved on average by 4%–6% over the 12-vowel categories for spectral modulation enhancement between 1.0 and 2.5 cycles/octave. Acoustic analysis suggested that the improved vowel identification as a result of the global spectral modulation enhancement may be due to increases in the spectral contrast of individual formants.
Effects of spectral slope on perceived breathiness in vowels
Authors: Landera Mario A. , Shrivastav Rahul
Published: October 2013

Previous studies have indicated that breathiness is correlated with changes in spectral slope as well as aspiration noise [Klatt & Klatt, ‘‘Analysis, synthesis, and perception of voice quality variations among female and male talkers,’’ J. Acoust. Soc. Am. 87, 820–857 (1990)]. In a recent study, Shrivastav and Pinero [Shrivastav & Pinero ‘‘Effect of aspiration noise and spectral slope on perceived breathiness in vowels,’’ J. Acoust. Soc. Am. 117, 2622 (2005)] observed that varying spectral slope resulted in minimal changes on the perceived breathiness for synthetic vowels. However, the stimuli tested in this experiment included a relatively narrow range of spectral slope variation. The goal of the present experiment was to verify the role of spectral slope on the perception of breathiness by testing stimuli that had a wider range of variation in spectral slope. Ten voices (5 male and 5 female) were synthesized using a Klatt synthesizer. Each of these was manipulated to generate two continua varying in their spectral slope from −3 to −30 dB/octave. One continuum had a constant cutoff frequency of 500 Hz, while the other continuum had a cutoff frequency between the second harmonic (H2) and the third harmonic (H3). Ten listeners judged the degree of breathiness using a 7-point rating scale. Preliminary results suggest that spectral slope has minimal effect on the perception of breathiness in synthetic vowels. [Research supported by NIH/R21 DC006690.]
Minimizing occlusion: An evaluation of open-fit versus deep-canal fit hearing aids
Authors: Vasil Kristin A. , Cienkowski Kathleen M.
Published: October 2013

Individuals with good low-frequency hearing and poor high-frequency hearing may complain that when wearing hearing aids, their voice sounds boomy or hollow [B. C. Grover and M. C. Martin, Audiology 18, 335–350 (1979)]. This is known as the occlusion effect. This effect occurs due to an improvement of bone-conduction responses when the ear canal is covered or blocked [D. P. Goldstein and C. S. Hayes, J. Speech Hear. Res. 8, 137–148 (1965)]. The purpose of this study was to determine the degree of measured and self-rated occlusion for hearing aids that attempt to minimize occlusion by utilizing open-fit or deep-canal fit designs. Measured occlusion was calculated from aided and unaided real ear responses obtained while subjects vocalized [i]. Self-ratings were acquired using an occlusion effect scale. Results showed that open-fit and deep-canal fit hearing aids differ in degree of measured and self-rated occlusion. Hearing aids with open-canal characteristics had less measured occlusion, according to real ear measures, than the deep-canal fit device. Self-ratings of occlusion were correlated with objective real ear measures. For deep-fitting devices, optimum insertion depth had to be reached in order for maximum occlusion reduction to be achieved. [Work supported by a grant from Vivatone LLC.]
Normalizing pitch variability in intoxicated speech
Authors: Hanke Ryan , Purnell Thomas
Published: October 2013

Intoxicated speech studies have shown mixed results with respect to prosodic characteristics. Both an overall F0 rise [Hollien et al., J. Acoust. Soc. Am. 110, 3198–3206 (2001)] and F0 lowering [Johnson et al., Phonetica 47, 215–237 (1990)] have been observed under intoxication. These conflicting findings may be due to increased F0 fluctuations at various levels of intoxication and use of inconsistent prosodic domains, such as averaging over entire sentences or utterances. If phonetic analysis takes into account prosodic boundaries, then models will account for appropriate prosodic rises and falls [Taylor, J. Acoust. Soc. Am 107, 1697–1714 (2000)]. This paper reports an analysis of recordings of both intoxicated and control subjects. Speech samples are analyzed at sober and three lev-els of intoxication. Of particular interest are the prosodic patterns at the often unreported descending limb of intoxication, which displays the widest range of variability in behavior. Use of F0 parameter extraction, stylization, and rotation methods over appropriate prosodic domains factors out spurious variation at different intoxication levels. Evaluation of this normalization procedure is reported with respect to both within- and across-subject variation. Implications for the analysis of normal, intoxicated, and disordered speech are discussed.
Propagation in highly range-dependent shallow-water waveguides with elastic sediments and beach interactions
Authors: Collis Jon M. , Siegmann William L. , Collins Michael D.
Published: October 2013

Accurate and efficient prediction of propagation over realistic models of elastic sediments has been achieved recently using parabolic equations. A major advance is the variable rotated parabolic equation solution [Outing et al., J. Acoust. Soc. Am. 115, 2579 (2004)], which allows treatment of variable bathymetry. The bathymetry is modeled as a series of constant slopes, and within each region the parabolic equation is solved in a coordinate system aligned with the interface. This approach has been benchmarked against analytic solutions and laboratory data. The variable rotated parabolic equation has been extended recently to solve problems involving variable topography (when the elastic sediment rises above the surface of the ocean). For these problems the surface boundary is modeled by a series of constant slopes. In this presentation we show how the transition from air-water to air-sediment surface boundary conditions, such as in beach environments, can be handled to high accuracy. In addition, an improved treatment of the boundary conditions at the air-sediment interface is described. Finally, procedures for handling elastic sediment interfaces of nonconstant thickness, along with range-dependent bathymetry, are developed and benchmarked. [Work supported by the Office of Naval Research.]
A near-field solution for underwater acoustics; a finite-difference solution to the Helmholtz equation
Authors: de Groot-Hedlin Catherine
Published: October 2013

A finite-difference method is derived for the frequency-domain acoustic wave equation as expressed in cylindrical coordinates. L’Hopital’s rule is used to transform the singularity at r=0 into a determinate form. The resulting finite difference frequency domain (FDFD) algorithm can be used to solve for sound intensities in complex models that may include high material contrasts and arbitrary bathymetry. Solutions obtained using this method are presented and compared to wide-angle parabolic equation solutions and analytic solutions, where available. Four models are examined: a uniform half-space, a waveguide with a rigid bottom boundary, an upslope wedge with a source in the ocean column, and a downslope wedge with a source below the seafloor. Comparison with analytic results indicates that the FDFD method accurately solves for the acoustic wave-field at all propagation angles and is more accurate than the wide-angle parabolic equation method at low radial distances from the source. The FDFD method is more accurate in situations where high angle scattering occurs near the source.
Bistatic invariance principle for multi-static active geometries
Authors: Zurk Lisa , Quijano Jorge , Rouseff Dan
Published: October 2013

The invariance principle describes the spatial interference patterns resulting from the coherent addition of propagating normal modes in the ocean channel. The relationship simplifies propagation structure into a scalar invariant which is approximately unity for many shallow-water environments. For passive sonar geometries (i.e., source to receiver) this valuable relationship has been extensively explored and applied to the interpretation of passive lofargrams. In active bistatic geometries, a transmitted pulse travels over two distinct propagation pathways (i.e., source-to-target and target-to-receiver). Assuming a distributed network (i.e., long-range propagation), each of these paths in isolation would produce interference patterns as dictated by the invariance principle. However, for bistatic active applications, the received pulse is a product of both propagation paths and a target-dependent scattering matrix which introduces mode coupling. For broadband waveforms, the question arises as to whether there is an observable interference pattern for a moving source. In this presentation, a derivation of the bistatic invariance principle is presented and discussed. Simulation results for the predicted time-frequency structure in a shallow-water channel are presented for specific sensor geometries and choices of target scattering matrix. Implications for application to multi-static active target tracking are presented in a companion paper.
John W. Kopec at Riverbank
Authors: Moyer David
Published: October 2013

John Kopec’s tenure at Riverbank as manager, supervisor, and chief liaison engineer during an active time of architectural and noise control related testing by manufacturers as well as trade associations made for some interesting challenges and client interactions. The author hopes to collect material from a broad range of interested parties to contribute to both aspects. A brief review of some of the 20-plus publications and presentation attributed to Kopec will also be provided.
Spatial release from aerial masking in a harbor seal
Authors: Holt Marla M. , Schusterman Ronald J.
Published: October 2013

Spatial release from masking (SRM) occurs when a signal and masker are spatially separated, resulting in improvement of signal detection relative to when they are spatially coincident. Harbor seals feed in the water but haul out on land for a variety of activities. There have been no SRM investigations conducted on harbor seals in air. In this study, SRM was measured at 1, 8, and 16 kHz in a harbor seal (Phoca vitulina) who had to detect an aerial tone in the presence of an octave band of white noise centered at the tone frequency. While the masker always occurred in front of the subject (0 deg), the tone occurred at 0, 45, or 90 deg in the horizontal plane. Absolute thresholds were also measured at these angles to account for differences in hearing sensitivity based on source azimuth. Current data show that the largest masking level differences (MLDs) of 7 dB occurred at 1 kHz when the signal was projected at 90 deg. MLDs reported here on an amphibious carnivore are larger than those measured under water, are consistent with measurements collected on terrestrial animals, and have important implications for noise effects on free-ranging animals.
Auditory feedback of vocal production in budgerigars using earphones
Authors: Osmanski Michael , Dooling Robert
Published: October 2013

There is considerable interest in understanding the mechanisms whereby auditory feedback (AF) enables a bird to learn and to produce a stable vocal repertoire. In the free field, budgerigars (Melopsittacus undulatus) show evidence of a Lombard effect, an increase in the intensity of their contact calls in the presence of background noise. They also adjust the frequency of their calls to compensate for pitch-altered AF. Here, we extend these findings using earphones to more precisely determine the role of AF in vocal production. Budgerigars were fitted with small head-mounted earphones and were trained to produce contact calls for food reinforcement in the presence of altered AF; alterations included noise and changes in call amplitude, frequency, and spectrotemporal structure (e.g., reversed calls). Results show that budgerigars produce compensatory changes to perturbations in AF. For example, these birds increase the amplitude of their vocal productions in the presence of noise (Lombard effect). They also reduce the level of vocal output when provided with amplified feedback of their own vocalizations. [Work supported by NIH Grant DC-00198 to R.J.D., NIH grant DC-04664 to R.J.D., and NIH Grant DC-006766 to MSO.]
Vector sensors—over 40 and still hot
Authors: Hines Paul C.
Published: October 2013

Acoustic vector sensors and gradient arrays have been in use in underwater acoustics for more than 4 decades, so one may wonder why they are featured in a session entitled ‘‘Hot Topics.’’ The reason lies in the recent resurgence in their use. This, in turn, is due primarily to major advances in engineering and signal processing that have been applied to these devices. Historically, theoretical gains have been difficult to achieve with these sensors due to their susceptibility to uncorrelated noise. That is to say, the very process of making a localized measurement of the vector acoustic field lowers the signal-to-noise ratio, relative to a simple pressure measurement. However, with today’s advances in design, manufacturing, and digital signal processing, high-quality performance can be achieved in a very small package size. Moreover, the current interest in these devices is not limited to underwater acoustic applications; rather, it extends across a number of technical areas within the acoustics community. This presentation will begin with a brief introduction to the theoretical foundation and history of these devices. Then, some current applications in both underwater and airborne acoustics will be highlighted.
Extracting coherent information from cross correlations of random wave fields
Authors: Sabra Karim G.
Published: October 2013

The random nature of noise and scattered fields tends to suggest limited utility. Indeed, seismic or acoustic fields from random sources or scatterers are often considered to be incoherent. Nevertheless, it has been shown that it is possible to extract information from random noise fields of a type that would typically be associated with a coherent process. An estimate of the Green’s function (or impulse response) between two points can be obtained from the cross correlation of ambient noise recorded at these two points. Recent theoretical and experimental studies in ultrasonics, underwater acoustics, and seismology have investigated this technique in various environments and frequency ranges. These results provide a means for passive imaging using only the ambient noise field, without the use of active sources. The coherent wave-fronts emerge from a correlation process that accumulates contributions over time from noise sources whose propagation paths pass through both receivers. Results will be presented from experiments using ambient noise cross correlations for the following applications: (1) localization and synchronization of unconnected acoustic receivers; (2) passive tomography of the seismoacoustic environment; and (3) studies of marine and airborne structures embedded in turbulent flow.
Measurements of sound leaks or ‘‘hot spots’’ and their effect on the architectural speech security of closed rooms
Authors: Gover Bradford N. , Bradley John S.
Published: October 2013

A new measurement procedure has been developed that accurately indicates the degree of speech security (speech privacy) of a closed office or meeting room. The procedure first determines the attenuation from an average sound-pressure field within a source room to single receiving points outside the room. These average-to-spot attenuations are used to predict transmitted speech levels outside of meeting rooms, which along with the background noise levels are used to derive a reliable indicator of the audibility or intelligibility of speech at the receiving points. A key aspect of the approach is that a localized weak spot in an otherwise highly insulating partition can be identified and assessed. Investigations were carried out as to the severity and detectability of different types of sound leaks intentionally introduced into an otherwise ‘‘good’’ wall separating two reverberation chambers. Steady-state and impulse response measurements of received pressure were made at a distance of 0.25 m from the wall. In addition, a highly directional beamforming microphone array was used in an effort to quickly locate the position of potential leaks. An overview of the measurement procedures will be presented, including discussion of the severity of several types of ‘‘hot spots,’’ such as holes, penetrations, and electrical boxes.
Thirty-minute concert: Human-space-factory and Rojo
Authors: Tutschku Hans
Published: October 2013

Human space-factory: The sound sources for this composition are derived from sung and spoken human sounds and from recordings in factories. Piano sounds serve as a pitched connection between the two sound worlds. The eight-channel space is used not only to place and to move the sounds, but to form a link between the sound families; by changing their position in space, the sound qualities transfer from one source to another. The three parts of the composition describe different densities: human sounds in an energetic space. The eight-channel electroacoustic composition is presented in a 5.1 mix; production: studio Musiques et Recherches Ohain; duration: 11.49 min; year: 1999; dedicated to Annette vande Gorne. Rojo plays with the imagination of simultaneous musical activities throughout the world. Recorded memories from several trips combine and exchange their qualities. Sometimes they change into huge sound masses, and occasionally their original environment is preserved. The composition creates an imaginary ritual, sourrounding the listeners, in which many sources meet and play together. The eight-channel electroacoustic composition is presented in a 5.1 mix; production: KlangProjekteWeimar (2004); commissioned by Radio Berlin Brandenburg; duration: 15.06 min; year: 2004; dedicated to Jonty Harrison.
Differences in whistles of bottlenose dolphins between two populations in southeastern Australia
Authors: Lemon Michelle , Cato Douglas H. , Harcourt Robert
Published: October 2013

The acoustic repertoires of two populations of Indo-Pacific bottlenose dolphins, Tursiops aduncus, have been studied in comparison with surface behaviors in southeast Australia. These populations are largely genetically differentiated and geographically isolated, one being in Port Stephens and the other in Jervis Bay about 300 km to the south. Ten variables were measured from the fundamental frequency of 200 whistle contours from each population, recorded in various behavioral contexts. Principal component analysis revealed significant differences between the populations. The Port Stephens dolphin population have less complex whistles of a higher frequency than those in Jervis Bay. Although significant differences were observed in phonation rates between behaviors at either site, there was no interaction between site and behavior. The genetic difference and degree of isolation of the populations suggest that cultural drift may play a part in the differences in whistles between sites. Ambient noise measured during observations showed significant differences between sites, but the measurements did not fully sample the range of ambient noise and differences are small compared to the expected temporal variation.
Verified passive acoustic detection of beaked whales (Mesoplodon densirostris) using distributed bottom-mounted hydrophones in the tongue of the ocean, Bahamas
Authors: Moretti David , Morrissey Ronald , DiMarzio Nancy , Ward Jessica
Published: October 2013

Passive detection of beaked whales has become increasingly important as at least two species, Blainville’s beaked whales (Mesoplodon densirostris) and Cuvier’s beaked whales (Ziphius cavorostris) have stranded in events associated with sonar. Passive acoustic detection and localization algorithms develop as part of the Office of Naval Research (ONR) Marine Mammal Monitoring on Navy Range (M3R) program will be presented along with results from a series of tests that demonstrate the efficacy of passive acoustic detection of vocalizing M. densirostris. Ninety-two bottom-mounted sensors at the Atlantic Undersea Test and Evaluation Center (AUTEC) were monitored for vocalizations. M3R systems were used to detect and localize vocalizing animals. Based on these real-time data, trained observers were vectored to the animals and verified the species. Focal follows coordinated with passive acoustics were completed. Observer photos along with raw sensor, detection and localization data were collected.
Nonlinear acoustics in E. L. Carstensen’s career
Authors: Blackstock David T.
Published: October 2013

HIFU and harmonic imaging are hallmarks of present day biomedical ultrasound. But it wasn’t always this way. At one time linear theory ruled supreme. Although by the early 1970s nonlinear acoustics had made its way into many areas of acoustics, e.g., physical acoustics, underwater sound, and aeroacoustics, biomedical ultrasound remained a safe haven for small-signalists. Ed Carstensen changed all that. By the mid-1970s he realized that linear theory could not account for certain phenomena he observed. At the 1978 Allerton Conference his invited talk entitled ‘‘Nonlinear Aspects of Ultrasonic Absorption’’ may have been the first public disclosure that nonlinear effects are important in biomedical ultrasound. His first archival work appeared as two papers in 1980; Tom Muir was a coauthor for both. During the next decade Ed and a series of colleagues showed that absorption could easily be dominated by nonlinear propagation effects. In turn the increased absorption causes increased heating, an important practical application. Ed’s pioneering work paved the way for many of the well-known applications today.
Thermal dose and the probability of adverse effects from biomedical ultrasound
Authors: Church Charles C.
Published: October 2013

Absorption of biomedical ultrasound heats tissue. Moderate heating to a few degrees above normal physiological temperatures can perturb biological systems, e.g., by altering normal metabolic processes, while brief, intense heating can kill cells, tissues, or entire organisms. Of particular concern for diagnostic ultrasound is thermally induced teratogenesis, which has been demonstrated in many animal species (chicken, mouse, rat, guinea pig, monkey) and apparently also occurs in humans. The nature and interpretation of such studies will be discussed. In therapeutic ultrasound, e.g., HIFU, the interest is in assuring the destruction of diseased tissue while sparing adjacent, healthy tissue. The concept of thermal dose will be described and used to quantify the probability and extent of biological effects expected from both diagnostic and therapeutic exposures. Additional factors relevant to thermal effects will also be considered, including the nature of the acoustic field in situ, as well as the state of perfusion and the variation in thermal sensitivity of the exposed tissue. It is concluded that adverse thermal events following diagnostic exposure are usually extremely rare, although there may be some reason for concern in a few special cases, while HIFU may induce significant collateral damage to proliferating cells pre- and postfocal zone.
A ladder network impedance model for lossy wave phenomena
Authors: Warren Daniel M. , LoPresti Janice L.
Published: October 2013

The ratio of Bessel functions J1(z)/J0(z) often occurs in the calculation of impedance of lossy components in electroacoustic devices. In particular, the electric impedance of hearing aid receivers or loudspeakers has a term proportional to a Bessel function ratio of this form when losses due to eddy currents are taken into account. This so-called semi-inductance has been notoriously difficult to model in simple lumped-parameter circuit calculation tools such as SPICE. This paper presents a simple ladder network derived from the Bessel function ratio expressed as a continuous fraction. The same transformation has been used to model the acoustic impedance of small cavities with losses at the thermal boundary layer.
Development of microelectromechanical systems capacitive microphone for high-frequency applications
Authors: Pedersen Michael
Published: October 2013

In this paper the development is described of a new high-frequency capacitive microphone based on the Knowles SiSonic MEMS microphone technology. The intended application for these microphones is aero-acoustic testing, which requires a transducer bandwidth of 80–100 kHz and the ability to measure sound pressures to 150 dB SPL without excessive distortion. The MEMS microphone structure was modified to meet these requirements and still be manufactured using the Knowles SiSonic production process. In addition, the microphone package was modified to eliminate the front port resonance, at approximately 12 kHz, associated with the standard SiSonic device. Specifically, the microphone package was modified with a lid that has lower acoustic inertance, thereby increasing the resonance frequency of the Helmholtz resonator formed by the front port and the microphone interior cavity. Details of the design process and the theoretical behavior of the microphones are presented, and it is shown that a microphone sensitivity of 0.5–1 mV/Pa can be achieved for a 100-kHz bandwidth. Preliminary results from fabricated microphones indicate a sensitivity around 0.5 mV/Pa and an A-weighted noise level of approximately 61.5-dB SPL. A more detailed analysis of the microphone noise spectrum and frequency response is presented.
Benchmarking the lattice Boltzmann method for the determination of acoustic impedances of axisymmetric waveguides
Authors: da Silva Andrey Ricardo , Depalle Philippe , Scavone Gary
Published: October 2013

A numerical technique for determining the acoustic impedance of axisymmetric waveguides based on the lattice Boltzmann method (LBM) is proposed here. This approach presents some desirable characteristics, namely, the possibility of explicitly considering the propagation of waves at low Mach number conditions with a relative low computational cost when compared to traditional continuum methods. The validation of the method is achieved by simulating the radiation of an open unflanged pipe using LBM and comparing the results with those obtained through a finite-element model and through the analytic solution derived by Levine and Schwinger. Finally, the results and the discussion of the method in terms of its computational efficiency and applicability to the simulation of wind instruments at more realistic conditions are presented. [The first author was supported by CAPES (Brazil).]
Keyboard characterization using spiral and Cartesian mappings of the harmonic series
Authors: Catravas Palmyra
Published: October 2013

Spatial transformations of functions of frequency can facilitate the analysis of frequency spectra and the identification of characteristic spectral patterns. Here, spiral and Cartesian mappings of the harmonic series are applied to frequency spectra from several keyboard instruments (modern grand piano, modern upright piano, fortepiano). Their utility in comparing properties of the instruments, including inharmonicity, coupling between strings, tuning errors, and beat frequencies, and simply identifying a fundamental frequency will be described. An update on a previous application of the transformations (identification of the B-A-C-H motif in music) will also be presented.
Analysis of brake squeal noise using the finite-element method: A parametric study
Authors: Gerges Samir N. Y. , Trichs Mrio , Balvedi Alessandro M.
Published: October 2013

Brake squeal noise has been under investigation by the automotive manufacturers for decades due to consistent customer complaints and high warranty costs. Brake squeal is a problem that has been faced by several numerical and analytical methods in the last decade. Among then, finite-element analysis is proving to be a useful tool to predict the noise occurrence of a particular brake system during the design stage. The finite-element method (FEM) has been employed to analyze the squeal propensity of the disc brake systems. The complex eigenvalue analysis conjugated with FEM has been widely used to detect unstable frequencies in numerical brake systems models. These unstable frequencies are related, in most cases, with high sound pressure levels generated during the brake system operation. This paper summarizes the application of the complex eigenvalue analysis in a finite element model. The effects of the operating parameters (friction coefficient, braking pressure, brake temperature) and wear on the dynamic stability of the brake system are examined. After identifying unstable frequencies and the behavior under different conditions, the performance of some control methods are tested. Changes in material properties and the application of brake noise insulators are presented and its effect discussed.
Saturation of burial-induced resonance frequency shift in acoustic landmine detection experiments
Authors: Alberts W. C. Kirkpatrick , Waxler Roger , Sabatier James M.
Published: October 2013

Modes in landmines have become a topic of recent interest in acoustic landmine detection. Of equal importance is the effect of burial on the experimentally observed resonances of landmines. Complicated dependence of resonance frequency on depth has been observed in field measurements and has been, thus, the topic of experimental and theoretical study. As such, further burial simulation experiments have been performed on a landmine and an acoustic landmine simulant. Burial simulation in water shows a saturation of downward modal frequency shift that rapidly deviates from the shift predicted by simple mass loading theory. This saturation agrees with that predicted by Velea et al. [J. Acoust. Soc. Am. 115, 1993–2002 (2004)]. Burial simulations performed in sand reveal resonance frequency depth dependence that saturates following a rapid downward frequency shift and a small resonance frequency increase. [This work was sponsored by US Army Research, Development, and Engineering Command, Night Vision and Electronic Sensors Directorate under Contract DAAB15-02-C-0024.]
Wide-bandwidth time-reversal techniques for landmine detection
Authors: Libbey Brad , Fenneman Douglas , Sutin Alexander , Kurtenoks Victor , Sarvazyan Armen
Published: October 2013

Detection of landmines using acoustic to seismic wave propagation has shown that accurate landmine localization is possible by sensing vibrations of a soil surface above the mine. Time-reversal acoustic (TRA) focusing allows concentration of elastic energy at a location in the soil that increases landmine vibration and improves signal/noise levels. Previous experiments with TRA landmine detection utilized narrow-band signals, but in the most recent experiments wide-bandwidth signals provide clear excitation of the mine resonant frequencies. A loudspeaker array broadcasts these signals and the resulting soil vibration is measured by a laser Doppler vibrometer. The experiment utilizes linear frequency sweeps and orthogonal signals with frequency content between 50 and 500 Hz. Using the orthogonal signals, the suggested TRA procedure can be implemented simultaneously with multiple transmitters to increase the scanning speed. The spatial distribution of energy on and off mine demonstrates that the TRA system concentrates elastic wave energy in the desired area with the focal spot dimension comparable to a wavelength. The spectral density of the TRA focused signal increases in the area near the resonant frequency of the landmine.
Performance of the scanning ultrasound vibrometer for sensing displacements of a randomly rough vibrating surface
Authors: Galinde Ameya , Andrews Mark , Donabed Ninos , Rappaport Carey , Fenneman Douglas , Ratilal Purnima
Published: October 2013

An analytic model is developed for the ultrasound field reflected off a randomly rough vibrating surface for a scanning ultrasound vibrometer system in bistatic configuration. Kirchhoff’s approximation to Green’s theorem is applied to model reflection and scattering from the vibrating rough surface. The model incorporates the beampattern of both the transmitting and receiving ultrasound transducers and the statistical properties of the rough surface. Conventional approaches for estimating surface displacement and velocity based on the laser vibrometer, such as incoherent Doppler shift spectra and coherent interferometry, are applied to the ultrasound system. Simulations with the model indicate that surface displacement and velocity estimation is highly dependent upon scan velocity and operating frequency of the ultrasound vibrometer relative to the roughness height and correlation length scales of the rough surface. The model is applied to determine optimal sonar design parameters and measurement geometry for the scanning ultrasound vibrometer for measuring ground displacements from acoustic/seismic excitation in land-mine detection.
Wigner distribution of ultrasonic transducers applied to scattering in polycrystalline media
Authors: Ghoshal Goutam , Turner Joseph A. , Weaver Richard L.
Published: October 2013

Diffuse ultrasonic backscatter measurements have been especially useful for extracting microstructural information and for detecting flaws in materials. Accurate interpretation of experimental data requires robust scattering models. Quantitative ultrasonic scattering models include components of both transducer beams as well as microstructural scattering information. Here, the Wigner distribution is used in conjunction with a radiative transfer equation (RTE) to model this scattering problem. The Wigner distribution represents a distribution in space and time of spectral energy density as a function of wave vector and frequency. An RTE is derived within the context of the Wigner distribution of various transducer beam models of common interest such that the source and receiver distributions are included in the analysis in a rigorous fashion. The resulting RTE is then simplified in the single-scattering limit typical of many diffuse backscatter experiments. Such experiments, usually done using a modified pulse-echo technique, utilize the variance of the signals in space as the primary measure of microstructure. The resulting backscatter model derived here is compared with previous derivations and experimental backscatter results for materials of common interest. These results are anticipated to impact ultrasonic nondestructive evaluation of polycrystalline media. [Work supported by U.S. DOE.]
Theoretical prediction of super-radiant modes in ideal and distorted hexagonal clusters of two-dimensional sonic crystals
Authors: Sánchez-Dehesa José , Kosevich Yuriy A. , Torrent Daniel
Published: October 2013

Resonance modes confined in hexagonal and threefold symmetry clusters consisting of two-dimensional arrays of rigid cylinders in air have been studied analytically and numerically using a multiple scattering method. It is shown that in the low-frequency (homogenization) limit the triangular modes play a fundamental role in the radiation behavior of the cluster. Analytical formulas are found to predict the frequencies of weakly confined resonance modes, whose pressure patterns have triangular symmetry. In the case of ideal hexagonal cluster, there are two degenerate triangular modes, which result in sixfold symmetry of the far-field radiation. In the case of distorted hexagonal clusters with threefold symmetry, two triangular modes with different frequencies are predicted. These modes have the property of being strongly radiating along three normals to the sides of the distorted hexagonal cluster, having their radiation properties not equivalent. Multiple scattering simulations confirm our analytical formulas and show the predicted threefold symmetry of the far-field radiation from the distorted hexagonal cluster. [Work supported by MEC of Spain.]
Adaptive mechanical model of human footsteps
Authors: Ekimov Alexander , Sabatier James M.
Published: October 2013

The vibration signature from footsteps can be exploited for human characterization and recognition. Footsteps are repeatable cycles of supported surface loading by a dynamic force. This force produces the vibration response of the ground/floor in a broadband frequency range. The vibration response at the distance R from the applied force is proportional to the dynamic force and results from the product of the footstep force and the ground/floor specific transfer function. The transfer function describes the propagation of vibration between the force location and the location of the detector. It was experimentally shown that walkers could vary the dynamic force of footsteps by controlling leg stiffness. An adaptive model of a walking person as a mass-spring system with controlled leg-spring stiffness was developed. This model was tested indoors and outdoors. Three distinct types of walking styles (regular, soft, and stealthy) with the same speed of motion were described and investigated. These styles result in different vibration magnitudes in the low-frequency range (below 100 Hz) due to differences in the walker’s leg stiffness. The transfer functions in the building and outdoors were measured and results are presented. [Work supported by Department of the Army, Army Research Office Contract W911NF-04-1-0190.]
Models of rattling objects for a moving base excitation
Authors: Robinson Daniel H. , Bernhard Robert J. , Mongeau Luc G.
Published: October 2013

Rattle noise is of particular concern in housing structures near airports. This secondary noise source is often related to large-amplitude low-frequency noise excitation of floors and walls and their interaction with loosely supported objects such as windows, wall hangings, and bric-a-brac. Simple theoretical models were developed to describe interactions between rigid bodies and vibrating surfaces. Rattle models were divided into two classes to describe resonant and nonresonant systems. The models allow a better understanding of the causes of rattle and help identify suitable criteria to mitigate rattle noise. In this presentation, thresholds of rattle onset are discussed and mitigation strategies to reduce and possibly eliminate rattle noise are identified. [Work supported by the Federal Aviation Administration.]