bluuebunny/crossref_metadata_2025 huggingface dataset:
Loudspeakers and listening rooms, Part II: The perception of reflections
Authors: Toole Floyd E.
Published: October 2013

A review of the effects of reflections on perceptions of sound quality, direction, image size, spaciousness, speech intelligibility, etc., lending perspective to the matter of which elements might be perceptually important in multichannel sound reproduction systems. In general they appear to be less problematic than is commonly believed. This, combined with the considerable ability of listeners to adapt to certain auditory influences of small rooms, brings into question several popular practices in the design of loudspeakers and listening rooms. Anechoic measurements on loudspeakers that have been done in a manner that anticipates sound reproduction in rooms can be used to calculate a figure of merit. The correlation between the calculated ratings, and those resulting from double-blind listening tests, is high: 0.86. This has implications for the acoustical treatment of rooms, and to the necessity for controlling the sound field at low frequencies. Only then can there be any assurance that the art in recordings will be heard by consumers as it was created in control rooms.
Fault dynamics of Indian Ocean earthquakes derived from the array analysis of T-waves
Authors: Pulli Jay , Upton Zachary
Published: October 2013

The Great Sumatran earthquake of 26 December 2004 generated some of the largest and longest T-waves ever recorded, and certainly the largest T-waves recorded on modern high-dynamic range hydrophones. For example, the recordings at the Diego Garcia hydroacoustic array indicate a T-wave duration of approximately 15 min. Array processing of these signals by many investigators indicates that the T-wave generation started near the earthquake epicenter and propagated northwest along the trench for nearly 600 km. This corresponds to the faulting zone defined by the aftershock distribution. A dataset of T-wave recordings of Indian Ocean earthquakes has been examined, covering the period 2001 to the present, including events on the oceans ridges and trenches, as well as some interplate events. The recordings were made at Diego Garcia, Cape Leeuwin, and Crozet Island. Event sizes range from magnitude 4 to 8. Bearing versus time is derived via intersensor cross correlations with a time resolution of 0.010 s, corresponding to a bearing resolution of 0.4 deg. Examples of events along the Sumatran Trench are shown with extended T-wave source areas, from which estimates of fault length and rupture velocity are made. These studies further demonstrate the utility of T-phases for understanding seismic source dynamics.
Using T-phase spectra to estimate rupture depth and static offset of the seafloor
Authors: Salzberg David
Published: October 2013

Analysis of T-phases recorded from recent tsunamogenic earthquakes indicates that they contain significantly more high-frequency (>50 Hz) relative to low-frequency (>10 Hz) T-phase energy with longer durations (>30 s) than nontsunamogenic events. Modeling T-phase spectrum explains this observation, where the spectrum of the recorded T-phase is the product of the source spectrum, propagation loss in the solid earth, conversion from seismic to acoustic T-phase energy, propagation loss in the ocean, and the instrument response. The propagation loss in the ocean can be accurately modeled. Assuming the seismic-to-acoustic conversion is constant over frequency, the remaining unknown term is loss in the solid earth which is primarily due to anelastic attenuation. A refined depth estimate can be obtained by modeling the solid-earth attenuation. That, coupled with the earthquake source mechanism, allows for estimation of the static ocean floor deformation and thus tsunami height. This approach has been applied to two tsunamogenic earthquakes (26, Dec. 2004, 28, Mar. 2005), and one other event. Both tsunamogenic events had significant (>1 m) seafloor uplift. In addition, the peak static offset estimated for the 26 Dec. event is consistent with estimates both from other studies, and from observations of the seafloor deformation.
Sumatra tsunamis recorded on hydophones and seismic stations in the Indian Ocean
Authors: Hanson Jeffrey A. , Bowman J. Roger
Published: October 2013

Tsunamis generated by the great Indonesian earthquakes of 26 December 2004 (Mw 9.3) and 28 March 2005 (Mw 8.6) produced high-frequency dispersed signals (5 to 60 MHz) recorded by hydrophone and seismic stations in and around the Indian Ocean. For the first and greater earthquake, the dispersed energy is frequently observed to 30 MHz and in one case to 60 MHz. The high-frequency signals are consistent with pointlike sources. The earliest-arriving tsunami signal is located to a source at 4.3N, 93.8E using event-to-station distances estimated by measuring dispersion and azimuth estimates using an array of hydrophones. Fine structure in the tsunami signal indicates a second high-frequency source just south of Great Nicobar Island. The dispersion of later-arriving energy matches predictions for reflections of the tsunami from bathymetric features in the Indian Ocean basin. For the 28 March 2005 tsunami, the high-frequency dispersion is observed at the Diego Garcia hydrophone station and the AIS seismic station, and tsunami signals without apparent dispersion are seen at four other seismic stations. Phase velocities are estimated at hydroacoustic arrays and agree with linear dispersion theory at frequencies above 12 MHz.
Surface and body waves from hurricane Katrina observed in California
Authors: Gerstoft Peter , Fehler Michael C , Sabra Karim
Published: October 2013

Hurricane Katrina struck land on 29 August 2005 as one of the strongest storms in the United States. The recent availability of continuous seismic data from a large number of stations enables us to characterize features of hurricane-generated noise in detail. By beamforming noise recorded on a distributed seismic array in southern California, we observe and track both the surface and body P-waves generated by Katrina in the 4–20-s period (0.05–0.25 Hz) microseism band. As the hurricane made landfall, the longer-period surface waves weakened, indicating that air/ocean/land coupling was a major factor in their generation. We observed P-waves that have propagated deep (1100 km) inside the Earth. These P-waves can be back-propagated to the hurricane. These findings demonstrate that ocean microseisms can propagate quite far and open the possibility of further use of seismic noise, even at very low signal level.
Stimulation of collagen production with low-intensity acoustics
Authors: Greenleaf James , Argedine Heather , Bolander Mark
Published: October 2013

Low-intensity pulsed ultrasound is a commonly prescribed therapy for delayed unions and nonunions after fractures. Several prospective double-blind clinical trials have shown that a 1.5-MHz ultrasound signal at a 200-s tone burst repeating at 1 kHz shortens the time to clinically evaluated healing by 30%. We have shown in vitro that pulsed ultrasound increases aggrecan gene expression and aggrecan production in chondrocytes, a key cell in the fracture healing process. Because the square wave pulsed 1.5-MHz signal produces radiation force vibration at 1 kHz, we tested the hypothesis that dynamic radiation force, not ultrasound, is responsible for the biological effect of the signal. Experiments showed that a 1-kHz acoustic square wave, simulating the radiation force caused by the clinically used signal, induced chondrogenesis similarly to pulsed ultrasound treatment in ATDC5 cells. These results may have implications for remote ultrasound or acoustic stimulation of different types of strain-sensitive cells in addition to those responsible for fracture healing.
Noninvasive prostate surgery using high-intensity focused ultrasound
Authors: Sanghvi Narendra T.
Published: October 2013

The salient features of ultrasound are to provide both medical diagnostic and therapeutic applications due to its short wavelength in soft tissue. These combinations have motivated us to apply ultrasound for the noninvasive surgery of the prostate diseases for both benign and malignant tumors. Over a decade of engineering and clinical research a successful transrectal ultrasound device, the Sonablate, has been developed and clinically practiced for the treatment of localized prostate cancer as well as benign prostatic hyperplasia. The main advantages of using the Sonablate device are on-line imaging of the prostate in 2D and 3D, accurate therapy planning, and real-time monitoring of treatment. The long-term, over 6 years follow-up clinical results from two multicenter clinical studies indicate no severe long-lasting side effects and acceptable efficacy of the treatment. The primary benefits of this treatment are fewer complications, outpatient procedure, and very quick recovery. The presentation will include design of the device, characterization of therapy and imaging transducer, and treatment parameters for the effective clinical results.
Therapeutic applications of ultrasound in intracellular drug delivery and tissue ablation
Authors: Deng Cheri X.
Published: October 2013

Biomedical application of ultrasound has been advancing beyond diagnostic imaging. Innovative strategies of therapeutic applications of ultrasound have been exploited that utilize both thermal and mechanical effects generated by ultrasound. For ultrasound mediated intracellular drug and gene delivery, ultrasound has been used to increase cell permeability transiently. We have developed novel techniques to investigate the mechanisms of ultrasound-induced cell porosity or sonoporation in real time at the single cell level. We studied the dynamics of sonoporation and correlation with delivery outcome in mammalian cells, bacteria, and tissues. Applications of high-intensity focused ultrasound (HIFU) include tissue thermal ablation and other applications. We have developed interdisciplinary techniques using real-time fluorescent imaging, acoustic radiation elastography, and optical coherent tomography (OCT) techniques to study the changes of electrophysiology, mechanical, and optical properties of cardiac tissues during focal HIFU cardiac ablation. [Work supported by NIH, ACS, and NSF.]
Violin octet scaling revisited
Authors: Bissinger George
Published: October 2013

Schelleng employed only two major resonances to scale the violin to other pitch regions, creating the violin octet: the main air (now labeled A0) to be placed at 1.5x and the main wood (B1, actually two modes) to be placed at 2.25x, the lowest string frequency. B1 employed flat-plate scaling and an empirical relationship between plate mode frequencies and B1. Experimental modal analysis of a complete octet showed flat-plate scaling for the corpus generally worked well, but A0 scaling was unreliable, even with postassembly modifications. Failure of the rigid-cavity Rayleigh relationship for A0 originated from an obvious major omission, cavity wall compliance, and one unobvious source, A0 coupling with the next higher cavity mode A1, which emerged much later via Shaw’s network model. Incorporating wall compliance into Shaw’s model greatly improved A0 and A1 predictions to within 10% over the octet. Acoustical analysis combined with patch near-field acoustical holography showed that A1, via induced corpus motion, was the most important radiator for the largest instrument in the main wood region and that the B1 modes, via net volume changes, can radiate significantly through the f-holes, two radiation mechanisms never considered in Schelleng’s original scaling.
Scaling of brasswind instruments
Authors: Pyle Robert W. , Myers Arnold
Published: October 2013

Consider two musically similar brasswind instruments pitched an octave apart, like trumpet and trombone. The steady-state tones of the trumpet, shifted downwards in pitch an octave by playing a recording at half speed, sound very similar to those of the trombone. The bore shape of the trumpet, however, is not a half-size dimensional replica of that of the trombone. The trumpet bell is about half the size of the trombone bell, but the narrower parts of the trumpet are considerably more than half the diameter of the corresponding parts of the trombone. Acoustic impedance measurements show the Q of air-column resonances to be similar in both trumpet and trombone. This is consistent with the dimensions of the instruments, combined with the dependence of viscous and thermal damping on tubing diameter and frequency. (Viscous and thermal damping dominate radiation damping throughout the normal playing range.) These observations suggest that a plausible scaling law for a family of brasswinds would preserve the pitch-shifted spectrum and the Q of the resonances across members of the family. How well (or poorly) brass makers follow this in practice will be shown from measurements of dimensions and acoustic input impedance on a variety of instruments.
Soundscape measurement and analysis
Authors: Genuit Klaus , Bray Wade
Published: October 2013

Soundscapes typically include a variety of sources, with individual and collective attributes (level, spectral structure, time structure, and perceived characteristics such as loudness, sharpness, fluctuation, and roughness). Relevant sound sources impinge on listeners from multiple directions and distances. Examples will be given of large differences between conventional and psychoacoustic values as a function of distance, and of multi-source summations. As an example, the subjective loudness difference for sound incidence over a small versus large solid angle for a constant sound pressure level and spectrum is known. Individual-source-relevant information, important in context, may be unrecognized unless spatial hearing is included in soundscape assessment. A demonstration of binaural versus monaural soundscape data acquisition, and subsequent analysis by both conventional and psychoacoustic measures considering human perception including time dependency, will be given. Evidence will be presented for considering human hearing not only in the analysis, but also in the acquisition.
Effect of longitudinal coherence on angle-of-arrival estimation in atmospheric turbulence
Authors: Collier Sandra , Ostashev Vladimir , Wilson Keith
Published: October 2013

A statistical model that accounts for the effects of atmospheric turbulence on a received acoustic signal has been previously developed [Collier and Wilson, J. Acoust. Soc. Am. 113, 2704–2718 (2003)]. It was used in calculations of the performance bounds, and of a maximum likelihood estimator (MLE), for the angle of arrival (AOA) of an acoustic signal received at an array operating in atmospheric turbulence with fluctuations described by a von Karman spectrum. This statistical model is based on the moments of a sound field as derived in the theory of wave propagation in a random medium (WPRM) [Ostashev, Acoustics in Moving Inhomogeneous Media (E&FN Spon 1997)]. In this model, an approximation to the second moment was used based on the transverse coherence from WPRM. Recently, the longitudinal coherence has been derived for WPRM [Ostashev et. al, 151st, Meeting of the Acoustical Society of America (2006)]. We examine limiting cases to determine the effects of the longitudinal coherence on the MLE and Cramer-Rao lower bound of the AOA.
Measurements of acoustic and seismic pulses from outdoor explosions
Authors: Albert Donald G. , Attenborough Keith , Boulanger Patrice
Published: October 2013

Measurements of the ground vibrations produced by airborne detonations of C4 were conducted at locations with a variety of ground types, including concrete, soil, forest, tropical vegetation, and snow cover. The measurements show that, although two separate seismic (ground vibrational) arrivals can be detected in all cases, the early seismic arrival from an underground path is always much smaller than the vibration induced by the air blast arrival. The acoustic-to-seismic coupling ratio for the atmospheric wave is a constant with respect to distance and peak pressure at a given location, but varies from site to site, usually between 1 and 14 μm/s/Pa. A conservative empirical equation to predict ground vibration from explosions is derived. This equation predicts that the commonly used vibrational damage criteria of 12 and 25 mm/s will be exceeded when the peak positive pressure exceeds 480 Pa (147.6 dB) or 1 kPa (154.0 dB), respectively. Either of these levels is much higher than the Army overpressure damage criterion of 159 Pa (138 dB). Thus in most situations damage from blast overpressure will occur long before damaging levels of ground vibration are reached. [This research supported by the U.S. Army Corps of Engineers and SERDP Seed Project SI-1410.]
Primary speech frequencies: Adaptation inside versus outside—Inhibition or excitation?
Authors: Weiler Ernest M. , Sandman David E. , Warm Joel S.
Published: October 2013

Previously, loudness adaptation from the ipsilateral comparison paradigm (ICP) and the simple adaptation (SA) procedure were compared at primary speech- related frequencies (250 to 4000 Hz), with only the ICP showing significant loudness decline/adaptation [Tannen et al., J. Gen Psychol. 128, 385–399 (2001)]. Eighty naive undergraduates participated in any one of three subsequent studies of ICP versus SA adaptation. In agreement with Tannen et al., only the ICP showed significant loudness decline/adaptation from 250 to 6000 Hz. However, at 8000 Hz both the ICP and SA show significant adaptation, and correlate significantly. However, despite the lack of correlation between individual scores under 8000 Hz, a further analysis of group mean values from 250 to 8000 Hz showed a significant correlation (r=0.97, p<0.001). Perhaps the SA procedure shows a lack of adaptation at speech frequencies because the method is insensitive. Alternatively, it may be considered that a ‘‘stable platform’’ [i.e., no adaptation for constant stimuli] favors the perception of the constantly varying speech signals. Support for the ‘‘stable platform’’ versus the ‘‘insensitivity’’ hypothesis will be discussed.
Can otoacoustic emissions indicate susceptibility to noise-induced hearing loss in individual ears?
Authors: Marshall Lynne , Lapsley Miller Judi A. , Heller Laurie M.
Published: October 2013

Otoacoustic emissions (OAEs) can potentially be used to identify normal-hearing individuals who are susceptible to imminent noise-induced hearing loss. Until now, there has been no way to monitor an individual’s susceptibility dynamically as it varies due to physiological and environmental factors. Although it is known that groups of normal-hearing noise-exposed people have lower than average levels of OAEs, such data have never been used to predict future hearing loss in the same individuals. Here, we discuss two studies where the OAEs and hearing thresholds of individuals were measured before and after hazardous noise exposure. Individuals with normal hearing and low-level or absent OAEs at baseline were at increased risk for acquiring noise-induced hearing loss after the noise exposure. This supports the theory that OAEs can reflect incipient inner-ear damage undetected by standard behavioral hearing tests. Furthermore, OAE efferent strength measures may be predictors of NIHL in humans. The animal data are promising, but developing an efficient OAE test that reliably distinguishes a strong efferent reflex from a weaker one in humans is challenging. [Work supported by ONR & USAMRMC].
Noise-induced and age-related hearing loss interactions
Authors: Kujawa Sharon G. , Liberman M. Charles
Published: October 2013

Noise-induced hearing loss (NIHL) and age-related hearing loss (AHL, or presbycusis) are widespread health problems that will continue to increase as our society ages. NIHL and AHL often coexist in the same ear; however, the conditions under which they interact and the mechanisms by which they do so remain poorly understood. Inspired by epidemiological studies suggesting that noise-exposed ears age differently from nonexposed ears [Gates et al., ‘‘Logitudinal threshhold changes in people with audiometric notches,’’ Hear. Res. 141, 220–228 (2000)], we studied interactions between NIHL and AHL in mouse; an animal with a short life span, with intrastrain genetic homogeneity to minimize variability and with interstrain differences in vulnerability which can be exploited to probe mechanisms. Using such models, we have uncovered evidence that early noise exposure can have an ongoing influence on the nature and progression of an age-related hearing loss. The nature of this age-related hearing loss exacerbation is special; it can occur even in ears without permanent threshold shifts from the noise and leads to massive loss of spiral ganglion neurons despite intact hair cell populations. Findings have practical importance for investigations of NIHL in animal models, and may have implications for clinical practices allocating noise-induced and age-related components of hearing loss as strictly additive. [Work supported by NIH.]
Weighted multiple cues and phonological features
Authors: Beddor Patrice S.
Published: October 2013

Do speaker-listeners determine a primary phonological feature from among multiple cues for a phonological contrast? Linguistic analyses traditionally postulate a primary feature, yet experimental evidence indicates that speaker-listeners assign relative weights to multiple cues, in context-dependent ways, and that these weighted cues are part of the phonological grammar. In this paper, evidence for a noncategorical, cue-weighted perspective is drawn in part from perception of nasal consonants (Ns). English Ns are shorter before voiceless than before voiced obstruents (in VNC contexts), and anticipatory vowel nasalization is temporally more extensive before the shorter, prevoiceless Ns. Unsurprisingly, listeners’ judgments of stimuli in which N duration and temporal extent of vowel nasalization were independently manipulated in CV(N)C sequences (coda C = [t] or [d]) broadly parallel the production data. But individual listeners differed in their cue weightings. Some listeners heard vowel nasalization and the nasal murmur as perceptually equivalent information about the presence of N, other listeners were highly sensitive to vowel nasalization, and still others’ cue sensitivity depended on coda voicing. The patterns of responses are difficult to interpret in terms of a primary feature, and the phonological implications of these patterns will be discussed. [Work supported by NSF.]
Enhancement of the vowel quantity contrast in Japanese and German by F0 and vowel quality
Authors: Lehnert-LeHouillier Heike , Whalen D.H.
Published: October 2013

Previous studies on the perception of vowel quantity in Japanese and German have shown an influence of F0 for Japanese and of vowel quality for German. The current study investigates F0 and vowel quality enhancement of vowel length perception in both languages. Native speakers of Japanese and German were presented with three series of stimuli: (i) vowel continua for the vowels /a/, /e/, and /i/ which differed in duration only; (ii) vowel continua for the same vowels which differed in duration and the steepness of the F0 fall over the vowel; and (iii) vowel continua for the same vowels containing both durational and quality cues. While vowel quantity in the first two series was perceived categorically by Japanese listeners, vowel quantity in the stimuli testing the influence of vowel quality was perceived as gradual rather than categorical by the same listeners. German listeners perceived all series as categorical. Thus F0 cues generally enhance the distinction of the vowel length contrast whereas the presence of quality cues facilitates the distinction in German but impedes the perception of the same distinction in Japanese. This suggests that enhancement of vowel quantity is governed by perceptual cues that are in part language specific.
Effects of task complexity on perceptual organization of speech cues by older listeners
Authors: Rossi-Katz Jessica A. , Arehart Kathryn H.
Published: October 2013

Older adults with and without clinically significant hearing loss often report difficulty communicating in multitalker environments. Past work in our laboratory has shown that older listeners with hearing loss benefit less from differences in talkers’ vocal characteristics (e.g., fundamental-frequency differences) relative to younger listeners with comparable hearing losses. The present study examined the extent to which age-related changes in the perceptual organization of speech cues are due to task demand. Two experiments used the Coordinate Response Measure to examine how the benefit listeners derive from talker characteristics interacts with the complexity of the response task as a function of both age and hearing status. Stimuli were amplified to assure audibility for listeners with hearing loss. Task complexity depended on whether the distracting signal was linguistically meaningful as well as the level of auditory processing required (discrimination versus identification). Older listeners generally benefited more from talker characteristics when task complexity was reduced (e.g., nonmeaningful distracter). The results are interpreted in the context of an information-processing model in which the increased difficulty of older listeners in multitalker environments is a consequence of reallocating limited resources towards the initial stages of processing at the expense of higher-level stages. [Work supported by Centers for Disease Control.]
Multi-static target tracking using a bistatic invariance constraint
Authors: Quijano Jorge , Velankar Manish , Zurk Lisa
Published: October 2013

The ability to track moving targets in shallow water channels is critically effected by bottom reverberation which can generate false alarms and substantially increase the domain of possible tracks. Even with application of advanced tracking algorithms, false alarms degrade performance and increase computational burden. The invariance principle, which predicts structure in the frequency-time domain, has been applied to passive sonar systems but has not been considered for active systems. In this work, a mathematical expression (called the bistatic invariance principle, see companion paper) is proposed as a constraint to discriminate target detections from false alarms and thus reduce the search domain for multi-static tracking algorithms. The constraint does not require knowledge of the underwater environment and is thus robust to environmental uncertainty. The bistatic invariance principle provides a relationship between changes in the bistatic range of a moving target to changes in the source frequency, and this relationship can be used to track the target position over time in broadband active sonar systems. Simulations of the bistatic invariance principle for multi-static active systems are presented and discussed and multi-static tracking performance is characterized for several choices of target scattering matrices and different environmental conditions.
A time-frequency approximation with applications in target recognition
Authors: Loughlin Patrick
Published: October 2013

In active sonar, the received signal can often be modeled as a convolution of the transmitted signal with the channel impulse response and the target impulse response. Because the received signal may have a time-varying spectrum, due, for example, to target motion or to changes in the channel impulse response, time-frequency methods have been used to characterize propagation effects and target effects, and to extract features for classification. In this presentation, we consider the Wigner time-frequency representation of a received signal modeled as the convolution of the transmitted signal with the channel and target responses. We derive a simple but very insightful approximation that shows the effects of the magnitude and phase of the frequency response of the target and of the channel on the Wigner representation of the transmitted signal. The results suggest possible features for classification, which we discuss. We also consider time-varying effects on the Wigner representation, such as changes in reflected energy due to changes in aspect angle, which we model by amplitude modulation. [Research supported by ONR Grant No. N000140610009.]
Generating simulated reverberation using noiselets
Authors: Sullivan Edmund J. , Goddard Robert P. , Greenbaum Hyman A. , Bongiovanni Kevin P.
Published: October 2013

Of the approaches to generating stochastic realizations of reverberation time series, the simple point scatterer model (PSM) is appealing because the statistics evolve naturally as the number of scatterers increases. Unfortunately, the number of eigenrays required is often overwhelming, especially for broadband signals. The more common ‘‘variance factorization model’’ (VFM) uses far fewer eigenrays to compute a time-dependent estimate of the variance of the reverberation, and applies the spectral factorization theorem to generate a sequence of short-time spectra, which is inverse transformed and concatenated to form the desired time series. However, the variance and factorization steps scale with the square and the cube, respectively, of the number of receiver channels, so the advantage is lost for element-level simulations of complex receivers. The ‘‘noiselet model’’ is conceptually similar to the PSM, but the transmit pulse is replaced by an ensemble of precomputed ‘‘noiselets,’’ which are sums of randomly weighted and delayed copies of the original transmit pulse. The number of eigenrays is thus comparable to the VFM, but scaling is linear in the number of channels, rendering this method tractable for real-time broadband element-level simulation. Examples are shown for a linear FM pulse at 10 kHz and 400-Hz bandwidth.
Of manatees and men: A future: Thanks to you, Joe
Authors: Gerstein Edmund , Gerstein Laura , Blue Joseph , Forsythe Steve
Published: October 2013

A comprehensive series of underwater psychoacoustic tests was conducted to measure the hearing abilities of the West Indian manatee under varying acoustic conditions. Pure tones, complex noise and real sounds, boat noise and species-specific calls, were presented to captive manatees under various acoustical conditions. The results from more than 30000 threshold trials define the first behavioral audiograms, directional hearing, and critical masking ratios for any sirenian species. Psychoacoustic tests demonstrate the noise produced by slow-moving boats is more difficult for manatees to hear and locate than the high-energy cavitation noise from faster moving vessels. The dominant frequency spectra of slow-moving boats fall near the fringe of their low-frequency hearing limits and below critical masking ratios. Complementing underwater ambient noise and vessel noise measurements revealed physical propagation factors that further render manatees vulnerable to watercraft collisions in their shallow-water habitats. Ironically, slow speed zones implemented to protect manatees may exacerbate the problem, making vessels difficult to hear, while increasing transect times and opportunities for collisions. By exploiting the manatee’s best hearing capabilities, it may be possible to mitigate collision risks with a low-intensity, environmentally friendly acoustic warning device that alerts manatees of approaching vessels. [Research supported by DOD Navy Legacy Program, Inland Navigation District, FFWCC]
The real reasons you should invest in a surround-sound system
Authors: Shinn-Cunningham Barbara G.
Published: October 2013

Most consumers of surround-sound systems understand that increasing the number and locations of speakers provides better control of perceived source location. The first goal of this talk is to explore why surround-sound systems generally work well in a variety of common settings, even though the acoustic effects of the rooms in which they are used can differ dramatically. What acoustic and psychoacoustic principles come into play? A second goal is to discuss the different perceptual benefits provided by a typical surround-sound system. Specifically, a good system not only allows listeners to hear sources at different directions, but also improves a listener’s ability to understand simultaneous sources and monitor a complex auditory scene. Finally, we will discuss why it is important to realize that surround-sound systems are entertainment systems, not simulators. If asked, most consumers would probably argue that surround sound is good because it makes it possible to recreate a realistic auditory experience. In fact, the aim of many recordings and games that use surround-sound technology is not realism, but vicarious thrill and vivid experience. In entertainment, bigger (and louder and more extreme) is better than everyday, ordinary sensations. [Work supported by NIDCD.]
A hybrid approach to rendering multichannel audio, using wave-field synthesis and stereophonic techniques, with virtual microphone control
Authors: Valente Daniel , Braasch Jonas
Published: October 2013

In the evolution of multichannel audio presentation, a number of formats have emerged including 5.1 surround and wave-field synthesis (WFS). Due to the complexity and number of components required to realize an immersive WFS system, the use in a home theater environment is currently impractical. This study aims to investigate the perceptual advantages of integrating both systems into a hybrid array capable of providing immersive sound for a number of listeners, at a scale that is attainable for the consumer in terms of budget and complexity. In this approach the three front speakers (left, center, and right) are replaced with a linear line array allowing for a better lateral and depth imaging, while increasing the sweet spot. The rendering will be created using Virtual Microphone Control (ViMiC) for both WFS, simulating a line of omnidirectional microphones with ViMiC, and surround sound, which will allows dynamic source movement, speaker positioning, and scalability. The advantage of using this hybrid approach is the application of WFS to home theater systems without facing the complexity of a complete two-dimensional WFS array, while still allowing for an immersive sound presentation. A psychoacoustic evaluation will be presented, as well as measurements of the composed sound field.
Effects of riverine seismic air-gun exposure on fish hearing
Authors: Mann David A. , Cott Peter , Hanna Bruce , MacGillivray Alex , Austin Melanie , Smith Michael , Popper Arthur N.
Published: October 2013

Seismic airguns produce considerable amounts of acoustic energy that have the potential to affect marine life. This study investigated the effects of exposure to an airgun array in the Mackenzie River Delta on the hearing of three fish species: northern pike (Esox lucius), broad whitefish (Coregonus nasus), and lake chub (Couesius plumbeus). Fish were placed in cages in 1.9 m of water and exposed to 5 or 20 airgun shots, while controls were placed in the same cage but without airgun exposure. Hearing in both exposed and control fish were then tested using auditory evoked potentials (AEPs). Threshold shifts were found for exposed fish as compared to controls in the northern pike and lake chub, with recovery within 24 h of exposure, while there was no threshold shift in the broad whitefish. It is concluded that these three species are not likely to be substantially impacted by exposure to a 2D airgun array used in a river seismic survey. Care must be taken in extrapolation to other species in other environments and to fishes exposed to airguns in 3D tests or where the animals are exposed to a larger number of airgun shots over a longer period of time.
Fabry Perot polymer film sensors for ultrasound field characterization and biomedical photoacoustic imaging
Authors: Beard P. C.
Published: October 2013

A contact ultrasound sensing technique based upon the detection of acoustically induced changes in the optical thickness of a Fabry Perot polymer film sensing interferometer has been developed for ultrasound measurement and imaging applications in medical and industrial fields. The technique provides a broadband (>50 MHz) response and excellent detection sensitivities (<1 kPa), comparable to those of piezoelectric PVDF transducers. A key feature is that the sensing geometry is defined by the area of the polymer sensing film that is optically addressed. As a consequence, very small element sizes (in principle down to the optical diffraction limit of a few μm) can be obtained without compromising detection sensitivity—a useful advantage over piezoelectric transducers. Additionally, by spatially sampling over a relatively large aperture, a high-density ultrasound receive array can readily be configured. These attributes lend the technique to a variety of applications such as mapping the output of broadband ultrasound sources, transmission ultrasound imaging, and biomedical photoacoustic imaging. The latter is particularly promising, offering the prospect of high-resolution imaging of optically absorbing soft tissue structures such as blood vessels for the study of tumors and other tissue abnormalities characterized by changes in the structure and oxygen status of the microvasculature.
Wave vector resonance in a nonlinear diffuse elastodynamic field
Authors: Akolzin Alexei , Weaver Richard L.
Published: October 2013

Nonlinear coupling within an elastic body leads to spectral energy redistribution. The coupling strength can exhibit sharp discontinuities as a function of frequencies, due to wave vector coincidences between constituent waves of different wave speeds. The phenomenon is investigated for an ensemble of weakly nonlinear elastic bodies of a generic ray-chaotic shape, with the elastodynamic field inside being treated as diffuse and described in a statistical fashion. Comparison is made between theoretical estimates of the average mode coupling strength and results of direct numerical simulations performed for an ensemble of 2D plane-strain elastic squares with rough boundaries and a model quadratic nonlinearity representative of elastodynamic waves. Existence of the wave vector resonance and its dependence upon frequency ratios is verified.
Dynamic characteristics of nonlinear interaction in elastic medium
Authors: Zagrai Nikolai
Published: October 2013

Traditionally, an acoustic wave process is analyzed in terms of sound pressure and/or sound velocity. The dynamic distortion of the wave profile, however, is complicated by contribution of both quadratic and cubic nonlinearities of the elastic medium. This condition necessitates expanding a range of variables to include particle and wave accelerations. As dynamic characteristics, particle and wave accelerations fully complement analysis of dynamic and inert properties of the elastic medium. The Riemanns solution, in which the quadratic and cubic nonlinearities are accounted for through respective derivatives of the sound velocity, allows for a new and different perspective on the aforementioned properties. For a simple wave with contribution of the quadratic nonlinearity only, the acceleration profile describing dynamics of wave deformation varies symmetrically relative to the discontinuity region. The cubic nonlinearity leads to more complex acceleration profile with asymmetric properties, which can be discerned and assessed using a combination of numerical and graphical methods. Such an approach is quite effective and vivid in separating contributions of quadratic and cubic nonlinearities. An integral nonlinear parameter N, introduced on the basis of this analysis, is proposed for estimating ability of the fluidlike medium to support effective propagation and nonlinear interaction of acoustic waves.
Diffraction pattern of an axisymmetric aperture from axial measurements
Authors: Pees Edward H.
Published: October 2013

An axisymmetric aperture can be represented by a circular hole in an infinite rigid screen, a circular piston undergoing harmonic motion, or a more complicated source composed of annular ring transducers. Ordinarily, the radiation pattern for this type of aperture is measured by moving a sensor along a circular arc about the center of the aperture, measuring the intensity of the radiated field as a function of angle. In the present case, the angular spectrum of plane wave representation of the diffracted field is used to demonstrate that the diffraction effect leads to the presence of a wave number distribution, observable along the normal axis of the aperture, that can be used to reconstruct the far-field radiation pattern from measurements taken only along this angular view. Because this diffraction pattern has a direct relationship to the boundary condition on the aperture, it follows that measurements of the axial field can potentially provide useful information regarding the size and shape of the aperture.
Application of a hybrid finite-element formulation for structure-borne vibration in an automotive vehicle structure
Authors: Homg Sang-Bum , Vlahopoulos Nickolas
Published: October 2013

The hybrid FEA method combines the conventional FEA method with energy FEA (EFEA) for analyzing systems that contain both flexible and stiff members. Conventional FEA models are employed for modeling the behavior of the stiff members in a system. Appropriate damping elements are introduced in the connections between stiff and flexible members in order to capture the presence of the flexible members during the analyses of the stiff ones. The component mode synthesis method is combined with analytical solutions for determining the driving point conductance at joints between stiff and flexible members and for defining the properties of the damping elements which represent the flexible members when analyzing the stiff components. Once the vibration of the stiff members and the amount of power dissipated at the damping elements has been identified, an EFEA analysis is performed in order to determine the amount of vibrational energy in the flexible members. The new developments are validated by comparing results of the hybrid FEA with results from very dense conventional finite-element analyses for a typical body-in-white vehicle structure. [Work sponsored by the Automotive Research Center, supported by the U.S. Army NAC.]
Structural monitoring from noise cross correlation
Authors: Sabra Karim G. , Kuperman William A. , Winkel Eric S. , Bourgoyne Dwayne A. , Dowling David R. , Ceccio Steve L. , Perlin Marc
Published: October 2013

It has been demonstrated theoretically and experimentally that an estimate of the Green’s function between two receivers can be obtained from the long-time average of the cross correlation of ambient noise at these two receivers in various environments and frequency ranges of interest: ultrasonics, underwater acoustics, and seismology. This result provides a means for structural monitoring using the ambient structure-borne noise only, 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 path passes through both receivers. We present experimental results using random vibration data collected on eight accelerometers mounted on a hydrofoil or plate at the Navy’s William B. Morgan Large Cavitation Channel. The tests were conducted at high Reynolds number, with the primary excitation source being turbulent boundary-layer pressure fluctuations on the upper and lower surfaces of the plate or foil. Identical deterministic time signatures emerge from the noise cross-correlation function based on robust and simple signal processing between passive sensors. These time signatures can be used to estimate and monitor the structural response of the test models.
Factors affecting phonetic variation of American English /k/
Authors: Shattuck-Hufnagel Stefanie , Veilleux Nanette
Published: October 2013

Word-final consonant reduction is commonly observed in American English, but variation in word-initial consonants is less thoroughly studied. Several considerations suggest that initial consonants might resist reduction; a more nuanced hypothesis is that initial consonants resist reduction in prosodically strong positions (i.e., at phrase edges and pitch accents) but may be reduced in weaker positions (e.g., phrase medially, in nonaccented syllables), particularly in un-self-conscious speech. A corpus of 16 spontaneous dialogues (8 speakers), prosodically labeled using the ToBI transcription system, provides a testbed for this view: the speakers were pairs of close friends engaged in an absorbing task which distracted them from paying close attention to their speech. Preliminary inspection of initial /k/’s from 3 speakers revealed a range of pronunciations (as described in earlier work), from normal prevocalic /k/ (with a silent closure period followed by release noise), to ‘‘leaky’’ /k/’s with some noise during the closure period and higher-amplitude release noise, to fricated /k/’s with constant-amplitude noise throughout, and offered some support for reduction in weak prosodic contexts. Further analysis will compare prosodic context with other factors governing phonetic variation (e.g., word frequency); implications for speech recognition and production will be discussed. [Work supported by NIH DC00075 and DC02978.]
Acoustic and articulatory correlates of contrastive focus
Authors: Thibeault Melanie , Menard Lucie , Leclerc Annie , Calabrino Anthony , Brasseur Annie
Published: October 2013

This paper aims at examining production of French speakers in marking focus-induced prominence at the articulatory and acoustic levels. The corpus consisted of CVC syllables, where C corresponds to one of the stops /p t k/ and V is one of the vowels /i a u/. Target words were embedded in carrier sentences elicited in two prosodic conditions: neutral (unfocused) and under contrastive focus. Four adult speakers (all native speakers of French) pronounced ten repetitions of each sequence. The audio signal and tongue shapes were recorded using a digital camera and a SONOSITE 180 ultrasound. Formant frequencies, rms values, duration, and tongue contours corresponding to each vowel were extracted. Analyses show that prosodic context has a significant effect on acoustic and articulatory data for all vowels, increasing F1 and F2 under contrastive focus, compared to the neutral context. However, this stable acoustic pattern is achieved by various articulatory strategies across subjects. For example, 2 subjects produced /u/ under focus with a lower tongue body than in the neutral context, whereas the remaining 2 subjects had a higher tongue body in focused syllables. Results are compared to previous studies on articulatory and acoustic correlates of prosodic structure in French and English.
Anisotropic seismic waves in systems with fluid-saturated fractures
Authors: Berryman James
Published: October 2013

The seismic wave speeds observed in exploration reflection surveys of oil and/or gas reservoirs may be dominated by the elastic properties in the dry state of very flat cracks or fractures, containing relatively little porosity. In contrast, the majority of work on effective medium theories (both estimates and bounds) has concentrated on systems whose elastic behavior depends on the volume fractions of the fluid constituents. Although a considerable amount of work has already been done in this area, there remain controversies regarding the use of the differential and self-consistent schemes for property estimation in these systems, and these controversies are known and well documented. When the reservoirs contain vertical fractures, these systems exhibit anisotropic seismic wave speeds. Methods are known that permit relatively simple calculation of these anisotropic properties from theoretical estimates made on randomly isotropic systems of fractures. When these methods are appropriately combined with weak anisotropy approximations associated with the Thomsen seismic-wave parameters, it is possible (at least in principle) to estimate fracture orientations and densities. The relationships between these forward and inverse problems will be treated and discussed with special emphasis on the question of uniqueness of the resulting interpretations.