bluuebunny/crossref_metadata_2025 huggingface dataset:
Fifty years of progress in speech coding standards
Authors: Cox Richard
Published: October 2013

Over the past 50 years, speech coding has taken root worldwide. Early applications were for the military and transmission for telephone networks. The military gave equal priority to intelligibility and low bit rate. The telephone network gave priority to high quality and low delay. These illustrate three of the four areas in which requirements must be set for any speech coder application: bit rate, quality, delay, and complexity. While the military could afford relatively expensive terminal equipment for secure communications, the telephone network needed low cost for massive deployment in switches and transmission equipment worldwide. Today speech coders are at the heart of the wireless phones and telephone answering systems we use every day. In addition to the technology and technical invention that has occurred, standards make it possible for all these different systems to interoperate. The primary areas of standardization are the public switched telephone network, wireless telephony, and secure telephony for government and military applications. With the advent of IP telephony there are additional standardization efforts and challenges. In this talk the progress in all areas is reviewed as well as a reflection on Jim Flanagan’s impact on this field during the past half century.
Development of MEMS microphone array technology for aeroacoustic testing
Authors: Shams Qamar A. , Graves Sharon S. , Bartram Scott M. , Sealey Bradley S. , Comeaux Toby
Published: October 2013

A new approach to aeroacoustic microphone array design and implementation is described and demonstrated. Using commercially available, low-cost MEMS microphones exhibiting a suitable low-frequency response, a series of 128-channel arrays were constructed on flexible Kapton circuit boards which were bonded to rigid aluminum backplates. Cover panels with precision cutouts for the microphones were bonded on top of the Kapton circuit boards to create a smooth surface providing flush-mounting for all microphones. Connections for the microphones were created by extending strips of Kapton containing power and signal busses to the rear of the backplates. All channels were powered from a common 3 V power source, and all signals were conditioned using custom-manufactured filtering and line-driving hardware. The conditioned signals were digitized and processed in near real-time using both commercially available and customized data acquisition and analysis hardware. This new type of array construction addresses two challenges which currently limit the widespread use of large channel-count arrays for aeroacoustic applications, namely by providing a lower cost-per-channel solution and by providing a simpler method for mounting microphones in wind tunnels. The MEMS arrays have been extensively tested in anechoic and hard-walled facilities, and their performance has been found comparable to that of condenser microphone arrays.
Articulatory characteristics of speakers with apraxia of speech during sentence production at different speaking rates
Authors: Hashi Michiko , Odell Katharine H. , Hayashi Ryoko , Nakayama Takeshi
Published: October 2013

The present study developed quantitative descriptions of articulatory movements in three speakers with apraxia of speech during sentences produced at different speaking rates. Point-parameterized articulatory data were obtained using the x-ray microbeam (XRMB) technique, and were compared with similar materials from 24 normal young-adult speakers of American English drawn from an existing XRMB database. Speed histories of markers attached to the lips and jaw during production of the test sentence ‘‘The other one is too big.’’ spoken at slow, habitual and fast rates were analyzed to determine mean peak speed, the number of speed peaks, and the timing of particular speed peaks for each sentence replicate by each talker. An attempt was made to derive speed histories for the lip marker expressed relative to concurrent movements of the jaw, to evaluate the relative contribution of jaw speed to lip speed in both talker groups. A description and discussion of results from the analysis will emphasize speaking rate effects on articulator speed and inter-articulator timing.
Motherese and Chinese: Evidence of acoustic changes in speech directed at infants and foreigners
Authors: Knoll Monja , Uther Maria
Published: October 2013

Infant-directed speech (IDS) is characterized by hyperarticulation, increased pitch, and high emotional affect, which is in turn thought to reflect a linguistic and emotional role for IDS. If the linguistic role is an independent contributor of the changes in IDS, then similar hyperarticulation should also occur in foreigner-directed speech (FDS) but without positive affective changes. To test this, nine mothers were recorded talking to their infants, and British- and foreign-adult confederates. Mothers were provided with toys to elicit the target words shark, sheep, and shoe, containing the corner vowels /a/, /i/, and /u/. Speech samples were analyzed to determine mean pitch and formant 1 and 2 (F1/F2) values of target vowels. Low-pass filtered speech samples of the mother’s interactions in each condition were rated on positive and negative vocal affect by 24 independent raters. Results showed that mothers hyperarticulated their vowels (indexed by F1/F2 values) in both IDS and FDS relative to ADS. Furthermore, mean pitch was highest in IDS compared to FDS and ADS. Positive affect was highest in IDS and lowest in FDS compared to ADS. These data suggest a linguistic function for prosody modifications in FDS and IDS that is independent of affective changes.
Individual differences in auditory discrimination of spectral shape and speech-identification performance among elderly listeners
Authors: Shrivastav Mini N. , Humes Larry E. , Kewley-Port Diane
Published: October 2013

Speech-understanding difficulties observed in elderly hearing-impaired listeners are clearly associated with recognition and discrimination of consonants, particularly within consonants that share the same manner of articulation. Spectral shape is an important acoustic cue that serves to distinguish such consonants. The present study examined whether individual differences in speech understanding among the elderly could be explained by individual differences in spectral-shape discrimination ability. This study included a group of 20 elderly hearing-impaired listeners, with a group of young normal-hearing adults also included for comparison purposes. All subjects were tested on speech-identification tasks, with natural and computer-synthesized speech stimuli, and on a series of spectral-shape discrimination tasks. The young normal-hearing adults performed better than the elderly listeners on many of the identification tasks and on all but two discrimination tasks. Regression analyses on data from the elderly listeners revealed moderate predictive relationships between some of the spectral-shape discrimination thresholds and speech-identification performance. The results indicated that when all stimuli were at least minimally audible, some of the individual differences in the identification of natural and synthetic speech tokens by elderly hearing-impaired listeners could be attributed to the differences in their spectral-shape discrimination abilities for similar sounds. a)Currently at Dept. of Commun. Sci. and Disord., 336 Dauer Hall, Univ. of Florida, Gainesville, FL 32611.
A scalable spherical microphone array for spatial sound capture
Authors: Elko Gary W. , Meyer Jens
Published: October 2013

With recent popular consumer acceptance of surround-sound audio, there is the need to develop new technologies that will allow for more accurate sound-field recording commensurate with or exceeding current multichannel audio playback systems. Real-world playback systems can have widely varying geometries and number of channels due to space and aesthetic requirements. Thus, there is a need to have a general recording scheme that allows for computationally simple modifications of the signals to optimize the playback for any geometry and number of playback speakers. One would also like to have a recording system that is scalable for future advances in spatial audio playback technology. A spherical microphone array has been proposed as a solution to these requirements. A spherical array has the desired property of enabling a beam pattern that is steering direction invariant with a relatively simple beamformer structure. The spherical array topology enables scalability and an elegant and mathematically straightforward beamformer design for efficient sampling and processing of the acoustic field. This talk will describe how the spherical array beamformer decomposes the sound field into compact multichannel representations that allow computationally efficient transformations to uniquely tailor the playback signals to any specific playback geometry.
Processing of reverberation data from 400–3500 Hz using line arrays with left/right discrimination
Authors: Preston John
Published: October 2013

The author recently participated in two experiments using directional towed arrays. One was the 2004 boundary characterization experiment near the Malta Plateau. That experiment was led by the NATO Undersea Research Centre (NURC). The area is rich in clutter objects like wrecks and mudvolcanoes and has some sub-bottom features that may be important. Sources were monostatic coherent pulses and SUS. The receiver was the NURC cardioid array. The other experiment was ONR’s 2003 Geoclutter effort to study shallow-water bottom reverberation and clutter in the STRATAFORM off New Jersey. That experiment was led by M.I.T. Sources were bistatic coherent pulses. The receiver was the five-octave research array (FORA). The STRATAFORM is known to have benign surface morphology but strong clutter is observed. Some highlights of the reverberant returns are discussed that include the correlation of returns with manmade targets and probable fish schools. The purpose of this work is to assess the directional characterization of the observed clutter and reverberation. The cardioid arrays should yield good directional estimates of reverberation sources above ∼1600−1800 Hz. Examples from the data analysis are presented using a cardioid beamforming algorithm developed by NURC. [Work supported by ONR Code 32, Grant N00014-03-1-0113.]
Loudspeaker array as a musical composition genre
Authors: Moulton David
Published: October 2013

A fixed array of loudspeakers can be used as a proprietary format for electronic music composition, leading to a fixed genre of work. The author will describe his experiences using a 6-channel array of full-range loudspeakers, describing the compositional principles he has employed, including issues of source localization, ambient and reverberant fields, available bandwidth, and sound-pressure levels. Spatial relationships, musical issues and problems, and related concerns will all be discussed.
Violin acoustic radiation synthesis: A source model for direct sound enhancement in musical acoustic environments
Authors: Waxman Jacob , Bocko Mark
Published: October 2013

Within the context of immersive acoustic environments (real or virtual) for purposes of musical performance, it is useful to recreate the acoustic field radiated by real musical instruments. Given the popularity of wave field synthesis for direct sound enhancement and other methods of holophonic sound imaging, source modeling is a desirable development for such musical applications. There exist careful directivity measurements of the sound radiation of the violin in the frequency range from 1 to 5 kHz, over which the far field directivity changes rapidly as a function of frequency [L. M. Wang, ‘‘Radiation Mechanisms from Bowed Violins,’’ Ph.D. thesis, Pennsylvania State University, 1999]. Source models based on these measurements using a cylindrical harmonic decomposition are presented. With this preliminary approach to violin acoustic radiation modeling, issues regarding further auralization of this synthesized field are subsequently addressed.
A potential explanation for marine mammal strandings
Authors: Crum L. , Kargl S. , Matula T.
Published: October 2013

The stranding of whales following naval exercises has been a topic of increasing interest. A recent article [P. D. Jepson et al., ‘‘Gas-bubble lesions in stranded cetaceans,’’ Nature (London) 425, 575–576 (2003)] has suggested that some version of decompression sickness may be involved. Considerable additional evidence has been presented that indicates both acute and chronic effects of these bubbles. We suggested some time ago [L. A. Crum and Y. Mao, ‘‘Acoustically enhanced bubble growth at low frequencies and its implications for human diver and marine mammal safety,’’ J. Acoust. Soc. Am. 99, 2898–2907 (1996)] that the acoustic fields produced by naval sonars could induce bubble formation under certain conditions, particularly if there were a high level of nitrogen supersaturation in these animals. Recent evidence of high supersaturation levels [D. S. Houser, R. Howard, and S. Ridgway, ‘‘Can diving-induced tissue nitrogen supersaturation increase the chance of acoustically driven bubble growth in marine mammals?,’’ J. Theor. Biol. 213, 183–195 (2001)] has stimulated us to perform a series of experiments that suggests that even modest acoustic intensities can trigger bubble formation under supersaturated conditions. Once bubbles are nucleated, these local supersaturation levels then result in bubble growth to macroscopic sizes, and their potential deleterious bioeffects. The results of these preliminary experiments will be presented. [Work supported by APL IR&D funds.]
Acoustic mode coupling effects from propagation through nonlinear internal waves
Authors: Reilly-Raska Laurel K. , Lynch James F. , Colosi John A. , Siegmann William L.
Published: October 2013

Existing literature demonstrates that costal and shelf break regions frequently contain significant nonlinear internal wave (NIW) activity and fronts. Our previous work, which incorporated stochastic modeling techniques in conjunction with azimuthally varying NIWs in an adiabatic setting, showed significant variations in intensity. However, NIWs can strongly affect energy coupling between acoustic modes. We seek to understand the evolution of coupled mode propagation through a field of randomly varying NIWs. We will examine the effects of coupling due to propagation through the intersection of two or more NIWs crossing at oblique angles. We use a fully 3D parabolic equation method and other tools to examine the ensemble of effects. [Work supported by ONR.]
Audio scene analysis for hearing aids
Authors: Roch Marie , Huang Tong , Hurtig Richard R.
Published: October 2013

It is well known that simple amplification cannot help many hearing-impaired listeners, and numerous signal enhancement algorithms have been proposed for digital hearing aids. In many cases, algorithms are most effective in specific environmental or source conditions. If one can properly detect components of the auditory scene, it is possible to dynamically apply enhancement algorithms which are appropriate for a given situation. This work illustrates this principle by describing a cohort detection scheme which serves as a control system for a frequency-domain compression algorithm. The compression algorithm preserves formant ratios and thus enhances speech understanding for individuals with severe sensorineural hearing loss in the 2–3-kHz range. By detecting speakers from broad cohorts (e.g., male, female), it is possible to adjust the compression ratio dynamically based upon characteristics of the auditory scene, resulting in a more appropriate enhancement than one based upon a static ratio. Cohort decisions are derived from the likelihood scores of a Gaussian mixture model classifier.
Acoustic shielding of engine noise by the Silent Aircraft airframe
Authors: Agarwal Anurag
Published: October 2013

The ‘‘Silent Aircraft Initiative’’ is a project funded by Cambridge-MIT Institute (CMI). Its aim is to discover ways of reducing aircraft noise to the point where it would be virtually imperceptible to people outside the airport perimeter in a typical urban environment. The present design of the Silent Aircraft is in the form of a flying wing with a large wing planform and a propulsion system that is embedded in the rear of the airframe. Thus, a large part of the forward-propagating noise from the intake duct of the engines is expected to be shielded from observers on the ground by the large upper surface of the wing. In this talk, the use of boundary element methods to predict the attenuation of sound due to shielding by the wing is discussed. The reciprocity principle is invoked to study the noise contributions from several engine-intake locations at given observer locations on the ground. This procedure yields the optimum location of the engine intake for maximum noise shielding. Finally, a technique to incorporate the effect of background mean flows on sound propagation is briefly discussed.
What are the limits of energy focusing in sonoluminescence?
Authors: Putterman Seth , Camara C. , Kappus B. , Su C. K. , Kirilov E. , Chakravarty A.
Published: October 2013

Sonoluminescence (‘‘SL’’) is an amazing marker for the extraordinary degree of acoustic energy focusing achieved in a cavitating bubble. Local energy dissipation exceeds Kirchhoff’s law by 1015 and the ambient acoustic energy density concentrates by 12 orders of magnitude to create picosecond flashes of broadband ultraviolet light. For single bubbles driven at 30 kHz, SL is nature’s smallest blackbody. Therefore the bubble’s interior is such a dense plasma that the photon-matter mean-free path is shorter than the wavelength of light. Excitation of a vertical column of fluid (∼50 Hz), so as to create a water hammer, upscales flash energy by a factor over one million, achieving peak powers approach 1 W. At 1 MHz the spectrum resembles Bremsstrahlung from a transparant plasma with a temperature ∼1 MK. At 10 MHz the collapsed size of the SL bubble approaches 10 nm, which raises the possibility that the SL parameter space may extend to the domain of quantum mechanics. At 30 MHz experiments are under way to excite sonoluminescence with sound fields in excess of 3000 atm. The strongest cavitation collapses may be realized with Greenspan’s ultrasonic resonators that reach fields in excess of 20 atm without cavitating. When bubbles are seeded with an external laser a massive cavitation event ensues.
Multiregression analysis of autoregressive with exogenous input speech synthesis parameters and voice qualities
Authors: Kasuya Hideki , Kawamata Masayoshi , Kido Hiroshi
Published: October 2013

This study investigates the relationship between acoustic parameters utilized in the formant-based ARX (autoregressive with exogenous input) speech synthesis model (J. Acoust. Soc. Jpn., 58, 386–397) and perceived voice qualities of synthetic speech. The acoustic parameters manipulated were F0 baseline, F0 range, spectral tilt of glottal flow (TL), formant scaling parameter (FS), and speaking rate (SR). Japanese expressions associated with voice qualities were high-pitched/low-pitched, masculine/feminine, hoarse/clear, calm/excited, powerful/weak, youthful/elderly, thick/thin, and tense/lax (Proc. ICSLP-98, No. 1005). A sentence utterance of an average speaker selected from a database of 109 male speakers was analyzed using the ARX method. Each of the five acoustic parameters of the utterance was manipulated at three levels, producing 243 samples of synthetic speech (3×3×3×3×3). Ten subjects evaluated the voice qualities of each of the 243 synthetic stimuli with regard to the eight Japanese expressions. Multiregression analysis showed that F0 range, F0 baseline, and FS were primary acoustic correlates of high-pitched/low-pitched and masculine/feminine, SR and F0 range for calm/excited, and F0 range, SR and F0 baseline for thick/thin. Significant relations were not found for the remainder of the Japanese expressions, which was thought to be associated in part with irregularities of glottal flow.
Nonlinear transverse string vibration: Model comparisons and numerical methods
Authors: Bilbao Stefan
Published: October 2013

There has recently been an increase in activity in developing digital models of nonlinear string vibration, for sound synthesis purposes; in a musical setting, such behavior is of interest under large-amplitude plucked string conditions. The usual starting point for such a model is a one-dimensional time-dependent second-order partial differential equation, which is discretized to yield a recursion; finite difference schemes are perhaps the most straightforward approach. There are, however, many suitable models; a general nonlinear transverse wave equation is taken as a starting point, and several approximations, namely the Kirchhoff–Carrier equation, digital waveguide type (i.e., tension-modulated) formulations, and the linear wave equation, are examined. The various solutions are compared and contrasted, both in terms of travelling wave propagation and the evolution of frequency content. The possibilities of and problems inherent in developing well-behaved numerical methods are discussed on a case-by-case basis, calling particular attention to the use of energetic quantities in discrete time as a means of controlling stability.
Analysis of sound propagation in a fluid through a screen of scatterers
Authors: Angel Yves C. , Aristegui Christophe
Published: October 2013

A multiple scattering analysis in a nonviscous fluid is developed in detail in order to predict the coherent sound notion in the presence of disordered heterogeneities, such as particles, fibers, bubbles or contrast agents. Scatterers can be homogeneous, layered, shell-like with encapsulated liquids or gas, nonabsorbing or absorbing, and can take a wide variety of shapes. A priori imposed limitations or physical assumptions are absent in the derivation, whether they concern the expected response of the fluid-scatterer mixture, the scatterer size relative to wavelength, the scatterer concentration or the screen thickness. As in any multiple scattering formulation, a closure assumption is invoked. Closed-form results for the backscattered and forward-scattered wave motions on either side of the screen of scatterers are obtained. The scatterer–fluid mixture is shown to behave as an effective dissipative medium from the standpoint of the coherent motion. It is found that the effective medium is fully described once two parameters are determined: the effective wavenumber and the reflection coefficient for the associated half-space screen. Remarkably, both parameters depend only on the far-field scattering properties of a single scatterer. Figures illustrate the results for selected scatterers.
Acoustical characterization of scatterer motion in a reverberant media
Authors: Conti Stephan G. , Roux Philippe , de Rosny Julien , Demer David A.
Published: October 2013

It has been demonstrated that the total scattering cross section of a moving scatterer in a reverberant media can be estimated from ensembles of reverberation time series. In order to obtain an accurate estimate of the total scattering cross section, the positions of the scatterer must be uncorrelated between consecutive time series. Here we show that as the displacement of the scatterer increases between time series, the measured total scattering cross section converges asymptotically to the absolute cross section. If the positions of the scatterer are correlated between consecutive time series, the measured cross section is lower than the absolute value. Theoretical formulas for the measured cross section versus average displacement are demonstrated using simulations and experiments for a ballistic motion or a random walk. Inversion of the scattering cross section measurements are also used to estimate the average displacement of the scatterers between consecutive acoustic pings. This inversion technique is applied to experimental measurements in tanks with a standard copper sphere following a ballistic motion and live fish in random motion.
Ultrasonic wave propagation in particulate mixtures
Authors: Mather Melissa L. , Challis Richard E. , Holmes Andrew K.
Published: October 2013

Measurements of ultrasonic compression wave attenuation as a function of frequency can provide a means to monitor suspensions of microscopic particles in liquids on-line in a process setting. Such mixtures are important in many industrial sectors including chemical, mineral, pharmaceutical, agrochemical and food. The ultrasonic data can be used to estimate the dispersed phase particle size distribution and to quantify dynamic effects such as flocculation and crystallization. The technique requires a detailed mathematical model to relate the ultrasonic wavenumber to mixture properties, and there are two distinct approaches to this—scattering and hydrodynamic. Although both have been shown to adequately describe sound propagation in dilute mixtures (up to ∼5% v/v), current models fail for concentrated suspensions of high density particles. The applicability of existing and future models of wave propagation in these suspensions will be greatly improved with more rigorous formulations for the local viscosity in the vicinity of a suspended particle, viscosity being the principal loss mechanism in such mixtures. In this paper five different theoretical formulations for local viscosity are investigated; their effects on wavenumber when included in both scattering and hydrodynamic propagation theories are compared, with reference to experimental data.
Time-reversal of waves near critical angle on a liquid–solid interface
Authors: Vignon Francois , Cassereau Didier , Fink Mathias , Aubry Jean-Francois , Marquet Fabrice , Gouedard Pierre
Published: October 2013

When sending a plane ultrasonic wave towards a liquid–solid interface, the reflected wave is affected, depending on the attack angle. In particular, when ultrapassing the critical tranverse angle, the reflection coefficient becomes complex, which in practice has the effect of dephasing the reflected wavefront. If this reflected wave is time-reversed and sent back towards the interface, the reflected wave of this time-reversed wave should not present this dephasing, as the time-reversal process restores the original phases. A theoretical and experimental study of these phenomena has been done. The dephasing of the reflected waves when passing the critical angle is observed, and as expected the signals after time-reversal are in phase. Nevertheless, a significant attenuation of the time-reversed signal is observed for attack angles around the critical transverse angle, as energy goes with the transmitted wave, which is not time-reversed. In a second part, it is shown by simulations and experiments how the fact of working at critical angle influences focusing of waves, by time-reversal or simple time-delays methods.
Effects of context and frequency shifts in vowel identification
Authors: Assmann Peter F. , Glidden Catherine M. , Nearey Terrance M.
Published: October 2013

A high-quality vocoder (Kawahara’s STRAIGHT) was used to study the effects of frequency shifts on the identification of vowels in syllables along a continuum from ‘‘bit’’ to ‘‘bet.’’ Natural speech versions of ‘‘bit’’ and ‘‘bet’’ were recorded by an adult female talker in the carrier sentence, ‘‘Please say the word —again.’’ Synthesized versions were constructed with upward and downward shifts in formant frequencies (FF; scale factors 0.9, 1.0, or 1.1) in combination with shifts in fundamental frequency (F0; scale factors 0.8, 1.0, or 1.2). When the carrier sentence and target syllable were both shifted, listeners reported more ‘‘bit’’ responses as the F0 shift increased and the FF shift decreased. Systematic shifts in the identification functions were also found when only the carrier was shifted. Overall, the results are consistent with a model that simulates the categorization responses of human listeners based on statistical distributions of acoustic measurements in natural speech.
Mechanisms of seafloor scattering: Roughness vs discrete inclusions
Authors: Ivakin Anatoily N.
Published: October 2013

A model of high-frequency scattering from the seafloor is developed taking into account discrete inclusions in the sediments. The model allows prediction of bottom reverberation, given material parameters of the sediment and inclusions and the size–depth distribution of inclusions. The frequency-angular dependencies of the seabed backscattering strength for various types of the sediment and inclusions are calculated and discussed. An environmental data set obtained at SAX99 site (near Walton Beach, Florida), including the sediment particle size–depth distribution and the water–sediment interface roughness spectra, was used to compare contributions of volume and roughness components of the seafloor scattering. It is shown, in particular, that contribution of gravel and shell inclusions and coarse sand fraction in total scattering can be dominating (over roughness) at very high frequencies (about 100 kHz and higher) and grazing angles above critical (about 30 deg), while roughness at SAX99 site is likely a dominating mechanism of bottom scattering at lower frequencies and grazing angles below critical. A combined model, taking into account both roughness and volume discrete scattering, is shown to be a good descriptor of bottom reverberation in a wide frequency-angular range. Possibilities for inversion of various sediment parameters from backscattering data are discussed. [Work supported by ONR, Ocean Acoustics.]
Bayesian inference for the propagation of measurement-based model parametrizations of bottom scattering strength to reverberation prediction uncertainty
Authors: LePage Kevin D. , Holland Charles W.
Published: October 2013

Measurements conducted on the Malta Plateau south of Sicily and at a site north of Elba in the Tyrannian Sea are used as the basis for the construction of bottom-scattering parameter probability density functions using Bayesian inference. The volume scattering and rough surface scattering prediction capability of the OASES model [Schmidt and Kuperman, J. Acoust. Soc. Am. (1995), and LePage and Schmidt, J. Acoust. Soc. (2003)] are used to model the bottom-scattering measurments in order to facilitate the extraction of these paremeter density functions. Issues regarding the resolution and resolvability of the bottom-scattering parameters are discussed, and comparisons between Bayesian probability density functions for reverberation predictions based on the scattering measurements and measured reverberation data are made. [Work supported by the ONR Capturing Uncertainty DRI.]
Influence of small-scale turbulent fluctuations on direct-path coherence from 4 to 20 kHz
Authors: Smith Kevin B. , Eroglu Ozer
Published: October 2013

A numerical study is presented with results from a sensitivity study of wave front spatial coherence. Specifically, the influence of small-scale (order of tens of meters to tens of centimeters) water-column turbulence on vertical coherence of a direct path, LFM chirp at a source–receiver separation of 500 m is examined. Parameters chosen as variable included turbulence strength, spectral cut-off scale (and combined rms value), source depth, receiver sub-array depths, and background sound speed structure. Preliminary analysis suggests that the background profile may play a more significant role than originally anticipated. The generality of this is considered in the context of measures of profile ‘‘smoothness’’ and ‘‘curvature,’’ as previously quantified by others. Potential implications include the use of background profile knowledge to arrange source–receiver geometry for optimal signal reception when coherent processing is advantageous (e.g., comms, active detection, etc.). The model results also show that the Fresnel scale of the turbulent pertubations may dominate the coherence structure, as predicted by theory. The impact of turbulence strength and frequency appear to behave as expected. [Work supported by ONR.]
Hot topics in structural acoustics: New directions and challenges
Authors: Burroughs Courtney B. , Capone Dean E. , Grosh Karl
Published: October 2013

Although structural acoustics is an integral part of many areas of research of interest to ASA members, it is the control of noise and vibration in marine vehicles that has underpinned much of the activities in structural acoustics. With shifts in emphasis, and therefore research funding, we face new challenges to maintain a healthy and vibrant level of activity in structural acoustics. Because of the complexities of most structural systems of interest, characterization and visualization of the acoustic responses present challenges. Multi-channel measurement systems are becoming more widely used in structural acoustics research. Numerical methods in structural acoustics continue to improve, moving up in frequency to close the mid-frequency gap. With new numerical and measurement methods, tailoring of physical and geometric properties for the control of acoustic performance are becoming more viable. The control and harvesting of energy in vibrating structural systems is also a subject of continuing research. Minimization of electronic components, e.g., microelectromechanical systems (MEMS), is presenting new challenges in structural acoustics. Biomechanics provides another domain of interest for the structural acoustician. In this paper, we will present an overview of the many challenges we feel are hot topics facing the structural acoustics community in the Society.
Hot topics in animal bioacoustics
Authors: Simmons Andrea M.
Published: October 2013

Recent technical achievements and conceptual advances in the study of communication and orientation by sound will be the focus of this presentation. In several different species (parrots, bullfrogs, big brown bats, dolphins), the use of multiple acoustic sensors to track the movements of animals and to map complex acoustic scenes under realistic field conditions has emphasized the plasticity of vocal behaviors. Behaviors such as the feeding buzzes of echolocating bats, once categorized as stereotyped by species, have now been shown to be variable and modifiable on the individual level. Similarly, interactions between senders and receivers in natural choruses are highly dynamic, yet seem to follow specific rules. Field studies have identified the production and use of new types of acoustic signals, such as the ultrasonic sounds produced by a species of Asian frog, and the use of seismic signals by mole rats and elephants. The vestibular system also plays an important role in acoustic orientation, such as flight and foraging behaviors of echolocating bats. Understanding the interactions between auditory and vestibular systems on both behavioral and physiological levels will lead to a richer understanding of animal bioacoustics.
Application of dynamic synapse neural networks on identification and localization of nonspeech sounds
Authors: Dibazar Alireza A. , Berger Theodore W.
Published: October 2013

This paper focuses on the dynamic synapses neural network (DSNN) for identification of nonspeech sounds, including the chambering of a gun, as well as localization of identified sounds. The algorithm employed consisted of extracting DSNN features from sounds and classification of features based on Gaussian mixture models (GMMs). To extract DSNN features, a single neuron with a presynapse including a 14th order differential equation, first order post-synapse, and first order inhibitory feedback was used. After training, network parameters were used as features. The classification task was then formulated as an estimation of conditional joint probability. Classification results were collected from both chambering identification and localization. Successful localization was defined as correct identification of speaker of origin. The number of training and testing samples were 120 and 160, respectively. The system performed 96.88% and 90.00% correct identification and localization of test samples.
Forging improvements in classroom acoustical quality
Authors: Bellomo Angelo
Published: October 2013

Major investments are currently being made in school infrastructure. In Los Angeles alone, 90 new schools are to be constructed in the next 10 to 15 years, and hundreds of existing schools will undergo major renovation. Similar efforts are underway in large urban school districts throughout the country. This presents a unique opportunity to improve acoustical quality in classrooms for future generations of teachers and students. While some school districts are embracing this opportunity, there are substantial challenges to be faced before improvements in classroom acoustical quality are widely realized. Despite recent adoption of the ANSI standard, there are inconsistent views among school administrators and designers on the extent of the problem and the urgency to act. Additionally, there is insufficient data on the incremental costs of achieving improved acoustical quality in new construction or modernization projects. Meanwhile critical design and purchasing decisions are underway. There are promising examples of how school districts can successfully meet these challenges and forge improved acoustical quality in the learning environment. The focus of this discussion is on the use of policy reforms to drive better design and purchasing decisions, and how these decisions can be further influenced by community involvement and interagency collaboration.
Source attenuating HVAC equipment—Just the facts
Authors: Hallstrom Arthur
Published: October 2013

Current classroom designs range from NC 63 to NC 25. The ASA/ANSI 12.60 Classroom Standard sets a relatively low background sound requirement for classrooms. Achieving 12.60 levels economically requires the maximum in source sound attenuation. This paper will provide a manufacturer’s perspective on current and low noise HVAC products and the resulting classroom sound levels. Predictive acoustics software will be used to predict the space sound power level and some indication of equipment cost will be provided in order to assist designers in what is the best approach to low noise classroom design.
Using computer modeling and auralization to provide classroom listening experiences
Authors: Coffeen Robert C.
Published: October 2013

Computer modeling and computer auralization will produce comparative listening experiences for architects, building owners, and building users based on selected interior surface shapes, interior finish materials, and ambient noise levels. Will these techniques provide easily understood audible information that will assist classroom designers, school administrators, and teachers in making proper assessments regarding classroom acoustics? Auralizations for both good and bad classrooms, based on ANSI S12.60 2002, will be presented for comparative listening.
Estimates of the percentage of sperm whales missed on combined visual and acoustic surveys in the eastern Pacific Ocean
Authors: Barlow Jay , Rankin Shannon
Published: October 2013

Abundance estimation from line-transect surveys commonly assumes that all animals on the trackline are detected. For long-diving species, such as sperm whales, this assumption is commonly violated. Marine mammal surveys were conducted in the eastern tropical Pacific in 2000–2002, with visual observers searching by 25× binoculars and acousticians aurally monitoring two elements of a towed hydrophone array. Visual and acoustic teams were independent and did not learn of detections made by the other team until after the animals had passed abeam. Data from 186 visual and acoustic detections were used to estimate the fraction of whales missed by each method. Many of the 178 acoustic detections were at greater distances than could be seen by the visual observers. Based on Palkas’ direct-duplicate method, the percentages of missed trackline groups were 38% and 21%, respectively, for visual and acoustic methods. Assuming these two detection methods are independent, the percentage missed by both groups is 8%. Acoustic detections greatly reduce the fraction of missed animals, but by itself this method cannot reliably estimate group sizes and still misses some groups. A combination of acoustic and visual methods is recommended for sperm whale surveys.
Model-based tracking of marine mammals
Authors: Abawi Ahmad T. , Hursky Paul , Porter Michael B. , Hildebrand John , Wiggins Sean , Sauter Allan
Published: October 2013

Data from the August 2003 experiment conducted by the Scripps Institution of Oceanography in the Southern California Offshore Range (SCORE) are used to track marine mammals. SCORE is a naval training area near the island of San Clemente located in relatively shallow water. The water depth where the experiment was conducted is around 360 meters. Data were recorded on a 100-m, eight-element vertical line array (VLA) deployed from the floating instrument platform (FLIP) and four bottom-mounted hydrophones deployed in an area covering approximately 3 square kilometers. During the course of the 7-day experiment continuous recording of the ocean environment was made. The recordings contain calls from various marine mammals, particularly blue and fin whales. Data recorded on the bottom-mounted hydrophones and the VLA are used to track singing marine mammals using two entirely different model-based tracking techniques: The animals are tracked by comparing the predicted (using a propagation model) and measured time difference of arrival recorded in pairs of bottom-mounted hydrophones. Additionally, matched-field processing on the VLA data is used to estimate the range and depth of the animals.
Lamb waves in bulk acoustic wave resonators: Analysis of spurious resonances and design of resonators in the UHF-VHF frequency range
Authors: Volatier Alexandre , Carruyer Gregory , Defay Emmanuel , Dubus Bertrand
Published: October 2013

Bulk acoustic wave (BAW) resonators exhibit attractive properties in terms of power handling capacity and on-chip integration to realize filters in the GHz range [K. M. Lakin, IEEE Ultrason. Symp. pp. 895–905 (1999)]. In a BAW resonator, a thin piezoelectric layer (a few mm) deposited between two electrodes is driven in its thickness extensional mode of vibration. To get a high quality factor, this structure is decoupled from the substrate by a multilayer Bragg reflector or a back-etched membrane. A current problem in the design of BAW resonators is the existence of spurious resonances close to the thickness extensional mode which generate ripple in the filter passband. In this paper, these spurious modes are analyzed in terms of Lamb waves resonances. Physical modeling of BAW resonators using finite element ATILA code is presented. The influence of lateral dimensions and electrode geometry on spurious resonances is emphasized. With specific electrode design and electrical excitation, it is demonstrated that lateral modes of Lamb waves can be used to realize resonators in the 50–250-MHz range. Experiments on an AlN piezoelectric layer between Pt electrodes on a SiN membrane are presented. [Work supported by a ST Microelectronics grant (CIFRE).]
Ultrasonic nondestructive inspection of interface defects in anisotropic fiber-metal-laminates
Authors: Stijlen Stefan A. L. , Bakker Maarten C. M.
Published: October 2013

Ultrasonic inspection is an essential tool for the quality control of the fiber-metal-laminate Glare, which is currently applied in the production of the huge A380 Airbus aeroplane. Nowadays, the ultrasonic inspection of Glare is performed by a transmission C-scan, traditionally, or by a more advanced pulse-echo scan. In this research, a new method of data acquisition and processing is investigated. The data acquisition consists of reflection measurements for variable source-receiver offsets. The first objective is to image delaminations at or nearby interfaces. These defects can, for instance, be associated with kissing bonds due to locally imperfect coupled interfaces. The algorithm which processes and converts the data into an image is based upon the inverse scattering theory. From the acquisition level in water to the interface levels in Glare, the elastodynamic Green functions are computed including strong anisotropy, multiple reflections and conversions, refractions, and surface waves. Subsequently, interface defects are modeled as additional contrasts in compliance. Finally, an image is obtained through their optimization by minimizing a cost-functional which is the mismatch between the measured data and the synthetic data generated with the Green functions. [Work supported by STW, the Dutch technology foundation.]
Period doubling in free reeds coupled to pipe resonators
Authors: Goetzman Evan M. , Cottingham James P.
Published: October 2013

An earlier study investigated behavior of the reed–pipe combination consisting of an American organ reed installed at the closed end of a cylindrical pipe. Over a wide range of pipe lengths and playing pressures, the sounding frequency is slightly below a pipe resonance frequency and can be pulled considerably below the natural frequency of the reed. [Vines et al., J. Acoust. Soc. Am. 114, 2349 (2003)]. Additional measurements of reed vibration for these reed–pipe combinations for low frequency (48 Hz) free reeds show that as the playing pressure is increased there is typically a sudden transition to period doubling or, in some cases, tripling or quadrupling. Some pressure intervals exist in which apparently chaotic reed vibration occurs, or in which the reed will not vibrate at all. Period doubling was found to occur over varied values of pipe length, pipe diameter, and the use of two different reeds with matching resonance frequencies. General trends in the onset and steady-states of period doubling are described using measured spectra and spectrograms of both reed motion and radiated sound pressure over a continuous range of playing pressure. [Work supported by NSF REU Grant No. 0354058.]
Inexpensive apparatus for studies of the lip reed
Authors: McLaughlin Mark T. , Eliason Lowell J. , Ayers R. Dean
Published: October 2013

A circuit has been designed and built to provide real-time, precisely controlled video images of a brass player’s lips during the relatively steady part of a sustained note. This should be useful for both the scientist who wishes to model the lip reed and the beginning player who is just learning how to control that driver. The circuit uses a phase-locked loop integrated circuit to track the signal from a microphone in the mouthpiece and subdivide the period for triggering a strobe light. The signal from the video camera is used for arming the trigger, so that there will be at most one strobe flash per field. This circuit is stable enough in tracking the playing frequency that a trombone slide can be moved continuously through its full range of positions, yet the live, strobed image advances through equally spaced fractions of a cycle at a rate determined by the settings of the circuit. This is important because the playing frequency is not perfectly constant, especially for beginners. [Work supported in part by the Paul S. Veneklasen Research Foundation and the CSULB Scholarly and Creative Activities Committee.]