bluuebunny/crossref_metadata_2025 huggingface dataset:
Time-delay estimation in underwater acoustics: A global optimization approach
Authors: Michalopoulou Zoi-Heleni , Picarelli Michele
Published: October 2013

Arrival times and amplitudes of individual ray paths provide significant information for source localization and geoacoustic inversion in underwater acoustics. Considered in a statistical framework, estimates for such quantities can be obtained via maximum likelihood or maximum a posteriori methods. These approaches, however, require function maximization on a multidimensional space, demanding extensive computations depending on the number of distinct paths. Local search methods have been proposed as computationally low-cost alternatives; such techniques, however, often get trapped in local maxima. In this work, a global optimization approach is proposed for the maximization of the posterior probability distribution of arrival times and amplitudes. To avoid an exhaustive search, an estimate of the posterior distribution is obtained employing Gibbs sampling; it is, subsequently, straightforward to obtain values for time delays and amplitudes for which the distribution attains a maximum. Simulations show that the new method provides excellent estimates that are comparable to those of the analytical maximum a posteriori approach. Real data results from the Haro Strait Experiment further validate the method. [Work supported by ONR.]
Acoustic beam dynamics in deep ocean environments
Authors: Beron-Vera Francisco J. , Udovydchenkov Ilya A. , Rypina Irina , Brown Michael G.
Published: October 2013

Parabolic equation simulations of broad-band directional beams in highly structured deep ocean environments are used to illustrate the important role played by the background sound speed structure on controlling wavefield structure and stability, and to test theoretical predictions of time spreads. The predictions are based on both ray- and mode-based theoretical considerations, in which the stability parameter α and the waveguide invariant β, respectively, play important roles. [Work supported by ONR and NSF.]
An evaluation of source speakers for open-plan privacy measurements
Authors: W. Good Kenneth , P. Roy Kenneth
Published: October 2013

A variety of source speakers is used today when making field measurements of interzone attenuation in open-plan spaces for the purpose of calculating the privacy index. These speakers have a variety of performance characteristics and often do not meet ASTM E 1179. The question is, do these variations matter more or less for field or laboratory measurements? In this study we look at the speaker performance related to their impact on interzone attenuation in field measurements. An omnidirectional source speaker, a speaker meeting ASTM E 1179, and another typically used speaker are compared.
Dynamic holographic imaging of acoustic motion
Authors: Telschow Ken L. , Deason Vance A.
Published: October 2013

Optical measurement of acoustic motion at a surface is usually accomplished with a scanning point probe. A full-field view acoustic imaging microscope is described that records subnanometer displacement amplitude and phase over a surface without scanning. Images are recorded at video frame rates and heterodyne principles are used to allow operation at any frequency from Hz to GHz. Fourier transformation of the acoustic displacement image provides a mapping of excited mode wavenumbers at any frequency. This method readily measures (a) the acoustic displacement of transducers, (b) acoustic bulk wave reflection from subsurface objects in solids and liquids, (c) resonant ultrasound vibration modes of complex shapes, (d) surface acoustic waves, and (e) plate wave modes in isotropic and anisotropic materials. These and other examples are presented along with discussion and analysis for characterizing material properties, such as physical dimensions, material elastic properties, crystal orientation, electromechanical coupling, and the identification and visualization of defects.
A novel approach to high-frequency laser-based acoustic microscopy
Authors: Murray Todd W. , Balogun Oluwaseyi
Published: October 2013

A laser-based acoustic microscopy system has been developed which uses a modulated continuous wave (cw) laser source for acoustic wave generation. An amplified electro-absorption modulated diode laser source is used for narrow-band excitation of acoustic waves generation at frequencies up to 200 MHz. The resulting surface displacement is measured using a stabilized Michelson interferometer fed into an rf lock-in amplifier. The detection bandwidth reduction afforded by this technique allows for a significant improvement in signal-to-noise ratio (SNR) over systems using pulsed laser excitation, and displacement sensitivity in the femtometer range is obtained with only minimal surface heating. The source modulation frequency is scanned over the bandwidth of interest and the transient response of the specimen reconstructed from the frequency domain data. In addition, the use of cw excitation allows for resonant excitation of micro- and nanoscale structures for materials characterization or sensor applications. Experimental results demonstrate that the system is well suited for thin-film characterization, and for the nondestructive analysis of nanometer scale electromechanical devices.
The acoustics of the khaen, bawu, and gourd pipe
Authors: Cottingham James P.
Published: October 2013

Mouth-blown instruments using a free reed coupled to a pipe resonator have a long history in China, Japan, and throughout Southeast Asia. The khaen and the gourd pipe are unusual wind instruments, employing a free reed mounted in the side of a cylindrical tube open at both ends, although in the gourd pipe the player has the option of closing the bottom of the pipe so that the reed is near the closed end. The bawu is a closed cylindrical pipe with a free reed at one end, in which the effective acoustical length is varied by the use of tone holes. The playing frequency of each pipe of the khaen or the gourd pipe is typically slightly above both the resonant frequency of the pipe and the natural frequency of the reed. In the bawu, on the other hand, the pipe resonance pulls the sounding frequency well above the natural reed frequency, resulting in a striking difference in tone quality. Acoustical measurements made on these instruments include studies of reed vibration and impedance measurements of the pipes, with particular attention to the coupling of the reed vibration with the pipe resonator.
Development and measurement of a variable acoustic test chamber
Authors: Barnhill Colin , Ng Robert , West James E. , Busch-Vishniac Ilene J.
Published: October 2013

We have designed and constructed an acoustic test facility capable of varying from largely anechoic to largely reverberant. The chamber measures 18.25×13.5×8 ft., so it has a total volume of 1971 ft3 and a total surface area of 1000.75 ft2. The walls are lined with removable fiberglass panels covered in fabric; a hard ceiling has a removable drop ceiling of tectum panels located below it; and the linoleum floor on slab is covered by removable thick carpeting. The reverberation time in the chamber can be varied by over an order of magnitude (i.e., from 150 ms to 1.5+s) for frequencies above 200 Hz as measured by traditional means and with a special directional microphone system. All measurement tools excluding sound sources and microphones are located outside of the room so as not to influence the sound characteristics.
S-shaped glass also stands for soundless. Sound insulation measurements and implication for building practice
Authors: Pinto Beatriz M. , van Luxemburg Laurentius C. J. , Carvalho Antonio P. O. , Martin Heiko J.
Published: October 2013

This paper brings to discussion the sound insulation of a special type of glazing by studying a S(inusoidal)-shaped curved glass. This is been used in a concert hall (under construction in Portugal) with a forward-thinking Rem Koolhaas’s architecture requiring nonstandard solutions: glazing with very large dimensions (22 m by 15 m) and each ‘‘S-glass panel’’ with a wavelength of about 1.0 m and amplitude of about 0.35 m will be applied as a double facade. The restrictions in ISO 104-3 laboratory measurements (standard test opening for glazing 1.25 by 1.50 m and niche depth of 0.45 m) were not appropriate and not completely fulfilled due to differences in dimensions between small test sample, and the real required use on site as well as the silicone joints that connect the glass elements. For these reasons, the standard test opening of 10 m2 was used. These aspects are described and analyzed. The tests results (showing satisfactory sound insulation) were essential to understand the effect of the shape and the efficiency of the glass. This study aspires to be helpful to building designers who can, in this way, lose dependency on production process constraints and bring into being all kinds of shapes.
Visualizing automobile squeals and their vibration modes
Authors: Moondra Manmohan , Wu Sean
Published: October 2013

Automobile brake squeals have always been a major problem for the auto industry because of the high pitch and intensity level. Currently, the vehicle brake squeal diagnostics is carried out by using a scanning laser synchronized with squeals. If squeals occur at multiple frequencies, then filtering must be used so that the scanned out-of-plane vibration corresponds to a single frequency. This process is very time consuming, especially when squeals contain multiple frequencies. Moreover, the results thus obtained are valid at measurement locations only. In this paper, we use Helmholtz equation least-squares (HELS)-based near-field acoustical holography to reconstruct squeal sounds via a custom-designed 48-microphone array conformal to the shape of a brake assembly. This microphone array allows for taking a snapshot of 3D acoustic image on the surface of the brake assembly and produces 3D mappings of all acoustic quantities. In particular, we can identify the out-of-plane vibration modes that are responsible for squeals and reveal the locations where squeals originate from. There is no need for synchronization and filtering. The whole measurement can be done in seconds, and the reconstructed results are valid not only on source surface, but also in the field. [Work supported by NSF.]
New development of two-dimensional sound index for the design of brand sound in the passenger cars
Authors: Lee Sang-Kwon , Jo Byung-Og , Kim Byung-Soo
Published: October 2013

In automotive engineering, the production sound quality becomes an important design requirement. Especially, the brand sound is one of important advantage strategy in a car company. In the paper, the subjective evaluation for booming sound and rumbling sound, which are professional words used by NVH engineers in automotive technology, are adopted as the descriptive word for a car sound. In the stage of development of a car, the trained NVH engineers evaluate the booming sound and rumbling sound subjectively in car companies. The two sound indexes, which are objective evaluation for booming sound and rumbling sound, are developed in the paper. These indexes are used for the objective evaluation of sound quality for 14 passenger cars, which are samples of famous cars in the world. The results of objective evaluation are expressed in the two-dimensional sound indexes. The brand sounds of famous cars in the world are very well represented in two-dimensional indexes. In the paper, a production car is modified using theses two-dimensional indexes and its sound quality is improved. In future, the two-dimensional sound indexes are very useful for the development of brand sound. [Work supported by BK21 projects and partly supported by Hyundai Motor in Korea.]
Validation of the cylindrical microphone array for measuring sound power levels of noise sources
Authors: Nobile Matthew A.
Published: October 2013

Recent papers have (i) introduced the concept of the cylindrical microphone array for the measurement of sound power levels of noise sources as an alternative to the parallelepiped and hemispherical arrays [M. A. Nobile and J. A. Shaw, Proc. Inter-Noise 99], (ii) set forth a detailed procedure for using the cylindrical array that could readily be incorporated into international standards [Nobile et al., Proc. Noise-Con 2000], and (iii) presented the results of measurements using that procedure on a 1.75-m-high noise source using a variety of microphone positions to draw conclusions regarding the number of microphones, equal versus unequal areas, and traversing versus fixed-point implementations [Nobile et al., Proc. Inter-Noise 2002]. The cylindrical array has since been incorporated into ISO 7779 and is being proposed for inclusion in the upcoming revision of ISO 3744. In an effort to gain experience with this new array and to help validate its use, a prototype rotating cylindrical array was constructed, and measurements were taken on a variety of noise sources. The results are compared to those taken with the well-established hemispherical microphone array, using 40 coaxial circular paths.
Protection against noise produced by open lines of the underground on the example of residential area Butovo in Moscow
Authors: Shubin Igor L. , Sorokina Irina L. , Kryshov Sergey I.
Published: October 2013

In Moscow (Russia) there is actively conducted construction of new lines of the underground. Nowadays we use the model of the easy underground with an open system of lining for the economy of means for construction in designs of the underground. Till now in Moscow only 7% of the length from the general extent of the underground (276 km) was open. There are plans for construction of the underground with open lining for more than 100 km. One of the most difficult problems of designing lines of the underground with easy lining is the decision on the problem of protection against noise and vibration of adjoining residential areas. In the present work there is written the accepted decisions on protection against noise and vibration of a line of the underground constructed in the microdistrict of Butovo in Moscow. The accepted technical and building-acoustic decisions are resulted.
Overriding the signal: Perception of default versus non-default interconsonantal vowels in Japanese
Authors: Hirose Yuki , Dupoux Emmanuel
Published: October 2013

Consonant clusters are illegal in Japanese and in producing foreign words with clusters, the vowel [u] is used as a default epenthetic vowel. Our previous study revealed that Japanese speakers perceive a vowel [u] between consonants in VCCV stimuli, even when the vowel originally present was removed, thereby creating illusion. Our experiment 1 further shows the illusion can override the existing acoustic information supplied by other vowels. The duration of word medial vowels in VCuCV and VCiCV nonwords were manipulated in eight stages from stimuli full to 0 (removed). The Japanese subjects identified the word medial sound by choosing from [a], [i], [u], [e], and ‘‘None.’’ For the stimuli derived from VCuCV, majority of the Japanese subjects reported [u] even when most of the vowel information was removed. Other vowels were hardly reported. In contrast, for the stimuli made from VCiCV, [u] was still reported in 60% of the cases, [i] less than 10%, and ‘‘none’’ about 30% when the original [i] was largely removed but still existed. Together with the results of experiment 2, an ABX discrimination study, our data suggest that epenthesis is a perceptual phenomenon that could sometimes override existing acoustic information.
A linear mechanical-electrical-acoustic coupled physiological model of the cochlea: Response to acoustic and electrical excitation
Authors: Ramamoorthy Sripriya , Grosh Karl
Published: October 2013

A linear physiologically based finite element model is developed for analyzing the global mechanical-electrical-acoustic (active) filtering in the mammalian cochlea. The model consists of a two-duct fluid-filled rectangular geometry, the micro-mechanical structural network interacting with the fluid; the electrical circuit equivalent of cells and fluid in every cross-section is connected by longitudinal cables representing the conductivity of the cochlear fluids and includes the mechano-electrical and electro-mechanical transduction at the OHC. The acoustic pressures, structural displacements, and electrical potentials are determined numerically and compared with experiments. Reducing the amount of activity present in the model reduces the gain and lowers the frequency of peak BM velocity response compared to a fully active model, in accordance with experimental data. This model also possesses near-invariance to click induced noise at different gain levels. Using the same model parameters, the predictions of the local BM velocity response to electrical stimulation match available experimental data, providing an independent test of the model capability. Predictions of electrically evoked otoacoustic emissions are found to match experimental results as well. Roughness introduced into BM stiffness is found to result in fine structures in a fully active model and have little effect on a model with reduced activity. [Research funded by NIH–NIDCD.]
Active linear modeling of cochlear biomechanics using Hspice
Authors: Jarng Soon-Suck , Kwon You-Jung
Published: October 2013

This paper shows one and two dimensional active linear modeling of cochlear biomechanics using Hspice. The cochlear biomechanical modeling is based on the deductive approach of others but is processed using Hspice which is the most popular analog electric circuit simulator among electrical and electronic engineers. Because Hspice is so generally used for active filter design, the shortage of the present cochlear model may be supplemented with analog active filters added to the present model. This extra filtering may be arbitrary so as to be called second filters. The advantage of the Hspice modeling is that the cochlear biomechanics may be implemented into an analog IC chip. This paper explains in detail how to transform the physical cochlear biomechanics to the electrical circuit model and how to represent the circuit in Hspice code. The comparison between one and two dimensional models is figured.
A study of the pinna anthropometry and the spectral notch frequencies
Authors: Raykar Vikas C. , Duraiswami Ramani , Yegnanarayana B.
Published: October 2013

The head-related transfer function (HRTF) varies significantly between individuals due to the different sizes and shapes of different anatomical parts like the pinnae, head, and torso. Applications in the creation of virtual auditory displays require individual HRTFs for perceptual fidelity. A generic HRTF would not work satisfactorily, since it has been shown that nonindividual HRTFs result in poor elevation perception. While good geometrical models exist for the effects of head, torso, and shoulders, a simple model for the pinna that connects the anthropometry to the features in the HRTF does not exist. One of the prominent cues contributed by the pinna are the sharp spectral notches, which encode the elevation of the sound source. Recently, we proposed a method to extract the frequencies of the pinna spectral notches from the HRTF. In this paper we study the relationship between the extracted notch frequency and pinna anthropometry. Based on these observations new approaches for HRTF customization can be developed. [The support of NSF Award ITR-0086075 is gratefully acknowledged.]
Directivity pattern simulation of the ears with two pairs of hearing aid microphone arrays by BEM
Authors: Jarng Soon-Suck , Kwon You-Jung
Published: October 2013

The noise reduction of the ITE (in-the-ear) hearing aid (ha) can be achieved by an array of microphones. Each of the right and the left ears is assumed to be fixed with two HA microphones. This two HA microphone array produces particular patterns of directivity by some time delay between two microphones. The directivity pattern geometrically increases the S/N ratio. The boundary element method (BEM) was used for the three dimensional simulation of the HA directivity pattern with the two pairs microphone arrays. This numerical analysis may then be applied for the calculation of the time delay parameter of the digital hearing aid DSP chip. The separation between two microphones was fixed to 10 mm. The time delay between the two microphones was changed to produce the most narrow directivity pattern in the forefront of the head. The variation of the time delay was examined in accordance with input frequencies.
Development of a near-field acoustic holography system based on pressure and velocity measurements
Authors: Harris Michael C. , Blotter Jonathan D. , Sommerfeldt Scott D.
Published: October 2013

Since its conception in 1980, NAH has become an accepted analysis tool with a number of commercial packages now available. One limitation of NAH is that the acoustic field is reconstructed through a spatial sampling. Therefore, this technique becomes less efficient at higher frequencies where microphone array spacing must be reduced. Analytical models have indicated that a pressure and velocity-based NAH method will provide the same reconstruction resolution of current NAH methods with significantly fewer measurement locations. This would lead to a considerable savings in data acquisition time for scanning array systems and reduce the inefficiency at high frequencies. The pressure and velocity-based reconstruction method will be introduced. Experimental work towards validation of the analytical models will be presented.
Acoustic inspection of friction-stir weld
Authors: Doane John W.
Published: October 2013

Friction stir welding is gaining popularity as a joining technique in many manufacturing arenas. As it makes the transition from prototype evaluation status into mainstream, large-scale usage, there is an increasing need for comprehensive, efficient, nondestructive inspection methods for qualifying friction stir welded joints. Two of the most common defects in this type of weld are cavities inside the weld, called wormholes, and weld depth excursions. Each of these defects presents a potentially serious reduction in joint strength and must be found soon after part production. Present inspection methods, including penetrant dyes and x-ray imaging, are either ineffective or not practical. In this paper a nondestructive inspection method, using high-frequency acoustic waves, is used to detect these defects by measuring scattered signals using a laser-based acoustic receiver system. The experimental configuration, methodology, and sensitivity of the technique to the defects of interest are discussed as well as its advantages and disadvantages compared to the present methods. [Work supported by Lockheed-Martin Co.]
Talker differences in clear and conversational speech: Preliminary data with monosyllabic words
Authors: Ferguson Sarah Hargus
Published: October 2013

Several studies have shown that when a talker is instructed to speak as though talking to a hearing-impaired person, the resulting clear speech is significantly more intelligible than typical conversational speech. A recent study of 41 talkers [S. H. Ferguson, J. Acoust. Soc. Am., in press] demonstrated that for normal-hearing listeners identifying vowels in noise, the amount of improvement talkers achieve by speaking clearly varies widely. The current pilot experiment begins to extend this line of research to meaningful materials using two talkers from the Ferguson database, one male and one female. While the clear speech vowel intelligibility benefit was similar for these two talkers, overall vowel intelligibility was greater for the female talker than for the male talker. Monosyllabic words produced in clear and conversational speech by these talkers were excised from the sentences in which they were recorded and presented in noise for identification by young, normal-hearing listeners and elderly listeners with hearing impairment. These data will provide important information about the relationship between vowel intelligibility and overall speech intelligibility. Results will be discussed in this light as well as in terms of expected talker variability in the clear speech effect for meaningful materials. [Database development supported by NIHDCD-02229.]
The influence of speaking rates and utterance units on segmental duration of Mandarin speech
Authors: Jing Jing-Yi
Published: October 2013

The main purpose of this study is to investigate the effect of five different speaking rates and five utterance units on segmental durations of Mandarin. Thirty normal speakers participated in the speech sampling. The speakers read the speech material at five speaking rates, including the fastest, faster, median, slower, and slowest rate. There were five utterance units for each target syllable, including monosyllable, disyllable, trisyllable, four syllable phrases, and sentences. These segments measured include VOT of stops, noise duration of fricatives and affricates, nasals and vowel duration, as well as silence intervals, or pause intervals. Results showed that the consonant and vowel durations were all significantly influenced by speaking rates and utterance units. At five kinds of speaking rates, the durations of vowels changed more than those of consonants. Fricative durations expanded more than the durations of other consonants, while the duration of unaspirated stops kept constant at five speaking rates. Vowels in monosyllable had longer duration than those in other utterance units. In addition to speaking rates and utterance units, the syllable structures and tones also greatly influenced the vowel and syllable durations of Mandarin.
The status of vowels in Jordanian and Moroccan Arabic: Insights from production and perception
Authors: Al-Tamimi Jalaleddin , Marsico Egidio , Carre Rene
Published: October 2013

Due to the morphological structure of Arabic, vowels only occur in consonantal environment, never in isolation. The issue addressed here is whether static acoustic cues are sufficient to characterize Arabic vowels or dynamic ones are needed. This study is based on Jordanian and Moroccan Arabic (JA & MA), with eight and four vowels, respectively. Ten speakers per dialect were tested on both production and perception. In production, speakers produced vowels in words, syllables, and in isolation (in alveolar context). In perception, they categorized isolated vowels on an F1/F2 plan. Results from production show that, both in JA and MA, (a) vowels in isolation have greater variation than in syllables or words, (b) vowels in a word context are more centralized (than in syllables or in isolation), and that (c) MA vowels are more centralized than JAs. In perception, a high degree of variability within and between dialects is found. A new experiment of vowel perception in syllable context (CV) (i.e., dynamic trajectories) was elaborated to study the effect of contextual information on vowel perception in Arabic. Results on five JA speakers show that the variability has been lessened and that dynamic information seems to be more useful in CV categorization.
Phonetic properties of three Ayuuk (Mixe-Zoquean) dense vowel systems
Authors: Heriberto Avelino
Published: October 2013

Several theories of vowel dispersion have proposed that the vowel systems of languages tend to distribute evenly in the phonetic space to maximize the perceptual distinctness of the vowels (Liljencrants and Lindblom, 1972; Lindblom, 1986; Lindblom and Maddieson, 1988; Schwartz et al., 1997). This study investigates the acoustic properties of three Ayuuk (Mixe) languages spoken in Mexico, possessing dense vocalic systems, which in addition have a series of normal and the corresponding set of long vowels: Santa Mara Ocotepec Ayuuk (SMOA) with nine vowels /i, I, u, e, E, o, A, a, O/, Tlahuitoltepec Ayuuk (TA) with eight vowels /i, I, e, E, o, A, a, O/, and Alotepec Ayuuk (AA) with seven vowels /i, u, e, E, o, a, O/. The inventories of the Ayuuk languages are typologically interesting; the SMOA and AA systems are rather uncommon (Maddiesson, 1984), in contrast with the system of TA, which conforms to the main trends of vowel systems. Preliminary results lend support to a dispersion/focalization hypothesis in that the vowels are evenly dispersed in the available space and remain focalized without significant overlap with adjacent vowels. The phonetic properties analyzed in this paper suggest that two principles, maximal dispersion and maximal distinctness, shape the overall distribution of the vowel inventory of Ayuuk languages.
An acoustic and perceptual study of voiced geminates in Japanese
Authors: Kawahara Shigeto
Published: October 2013

In Japanese, voicing in geminates is subject to dissimilation while voicing in singletons is not. This paper advances a hypothesis that voicing in geminates is not as perceptually salient as voicing in singletons, and therefore losing voicing in geminates is accepted as an instance of ‘‘perceptually tolerated articulatory simplification’’ (Kohler, 1990), while devoicing singletons is too perceptually conspicuous. This paper reports an acoustic and perceptual experiment that supports this hypothesis. The acoustic study shows that closure voicing and closure duration are significantly weakened in geminates: Voicing ceases relatively early during the closure, and the difference between voiced and voiceless geminate closure length is smaller than the closure difference in singletons. The second experiment is a perceptual study, which is an identification task under a noisy environment. The results directly support the hypothesis that voicing in geminates is hard to hear, while voicing in singletons is reliably perceived. Taken together, the results of the two experiments provide support for the view that voicing in geminates may be prone to neutralization because it is poorly perceived. This conclusion, more generally, lends support to the view that contrasts signaled by weak phonetic cues are prone to phonological neutralization (Kohler, 1990; Steriade, 1997).
Cramer–Rao lower bounds applied to shallow water geoacoustic parameter estimation using the distribution of the interference invariant
Authors: Daly Peter M. , Mikhalevsky Peter N.
Published: October 2013

One can exploit the broadband acoustic striation patterns produced by loud merchant ships in shallow water to obtain geoacoustic parameters. One measures these patterns as a function of range and frequency, calculates their two dimensional Fourier transform to produce intensity as a function of wavenumber and delay, then performs an inverse Radon transform to obtain the distribution of the interference invariant. With this observable, one can perform a global inversion for parameters of interest, such as sediment and bottom sound speed, density, and attenuation. If the parameter estimate is unbiased and the observable vector Gaussian has high signal-to-noise ratio, then one can obtain the theoretical minimum variance and covariance associated with the parameters by solving for the Cramer–Rao lower bound (CRLB). In this presentation, the parameters of interest are assumed to be deterministic and observed ‘‘noise’’ is a function not only of additive Gaussian noise at the hydrophone, but also due to uncertainty in other model parameters, such as hydrophone depth and range bias. This talk will present numerically calculated CRLB as a method for determining the performance of this inversion method.
Subsurface flaw localization based on the spatio-temporal gradient array processing
Authors: Teramoto Kenbu
Published: October 2013

Lamb waves are guided ultrasonic waves capable of propagating relatively long distances in plates and laminated structures, such as airframe skins, storage tanks and pressure vessels. Their propagation properties in these media depend on the vibrational frequency as well as on the thickness and material properties of the structure. Structural flaws such as dis-bonds, corrosion and fatigue cracks represent changes in effective thickness and local material properties, and therefore measurement of variations in Lamb wave propagation can be employed to assess the integrity of these structures. In this study, the localization based on the spatio-temporal gradient array processing is derived theoretically. The proposed method has an ability to characterize the phase velocity of the Lamb-wave propagation through the linearity among the 4-dimensional vector which is composed by following components: (1) a vertical (z-directional) displacement, (2) its vertical particle velocity, (3) x-directional and (4) y-directional out-of-plane strains. This paper is organized as follows: the second section presents the process of the localization and the proposed algorithm, the third section evaluates the proposed velocimetry via numerical experiments.
Design and acoustics in classrooms—a Philadelphia story
Authors: Roy Kenneth P. , Good Kenneth W.
Published: October 2013

The Lamberton School in Philadelphia was built in 1949 and may have met all of the acoustical design requirements of the day... but! An acoustic and A/V evaluation of a typical classroom was made both before and after an architectural intervention to address the ANSI S12.60 Classroom Standard. See the numbers and hear the difference, both for yourself, and through the opinions of the teacher who has experienced the change. What was done and the effects thereof will be discussed.
Characterizing short-time transient events in the information technology soundscape
Authors: Bray Wade R.
Published: October 2013

Information technology (IT) products form an increasing part of modern life in residential, recreational, and work contexts. Although average levels and sound power are generally low and have been improving for years, many IT products and components produce transient sounds which draw attention and elicit customer complaints. Standardized characterization by average sound power, with reference to tonal and impulsive characteristics, may not adequately capture subjectively important time-varying behavior. Time/frequency, time/magnitude, impulsiveness analysis methods, and an adaptive relative pattern-recognition technique will be applied to the short-time transient noises produced by a variety of information technology devices.
Explorative sound evaluation
Authors: Paul Stephan , Schulte-Fortkamp Brigitte , Genuit Klaus
Published: October 2013

Exposure group description of sound based on AISP (exploration of associated imaginations on sound perception) is a powerful tool in sound quality evaluation. Used in a public research project it was stated that AISP needs further adaptation for automotive use. The present study was intended as a first approach refining the method for industrial application regarding the evaluation of an appropriate test design. The study was carried out using a driving simulator and a car, both with changeable acoustic properties. Verbal evaluations by the driving test individuals and the sound were recorded. Later on an open interview with the driver was carried out based upon given commentaries. The verbal data were analyzed through a qualitative approach. By means of this data the car with changeable acoustic properties driven on road was identified as most appropriate for sound evaluation of car interior sounds. The verbal data analysis and the physical analysis of the sounds gave valuable hints for troubleshooting and target sound definition. As the study showed the strong dependency of sound evaluation on the test design a representative evaluation should be done in an adequate design (car on road). Furthermore, initial usable tools and guidelines for industrial application were developed.
Queuing for quiet–The natural soundscape microstructure from a visitor perspective
Authors: Horonjeff Richard D. , Anderson Grant S.
Published: October 2013

The passage of PL100-91 The National Parks Overflights Act of 1987 and PL106-181 The National Parks Air Tour Management Act chartered the National Park Service (NPS) and Federal Aviation Administration (FAA) to restore natural quiet to park settings, especially those with lengthy occurrences of nonindigenous sounds. Dose–response studies sponsored by NPS and FAA showed that among several dependent variables tested, nonindigenous time audible was the best predictor of visitor-reported annoyance and interference with natural quiet. Other than for Grand Canyon NP, PL100-91 lacked specificity for depicting nonindigenous times audible. Since 1991, several field investigations have produced over 400 h of source identification logs maintained by audiometrically screened observers. At over 25 sites in 7 parks, the data acquisition protocol used a forced-choice, hierarchical menu structure with audible source state changes timed to the nearest second. The identical protocol across all studies provided the basis for examining the amount of time a visitor would have to wait (T) to experience a contiguous block of indigenous-only sounds of duration (D), given a random arrival time. The paper reports means and distributions in T for various values of D, observed data clusterings across site groups, and the effects of mitigating variables.
Phrase-final frication lengthening in a variety of English spoken in the Iron Range of Northern Minnesota
Authors: Bauer Matt
Published: October 2013

This study examines acoustic and perceptual correlates of final-devoicing in a variety of English spoken throughout the Iron Range of Northern Minnesota. A pilot study of one speaker indicates devoicing in the dialect is present phrase-finally but not phrase-medially x2(1)=0.89, p<0.05. Measurements of voicing and frication in words like tens and tense reveal devoicing is not due to shortening of the duration of vocal fold vibration (which is what a devoicing process predicts). Instead, frication of phrase-final fricatives are lengthened compared to frication of phrase-medial fricatives F(2,27)=17.36, p<0.05, but vocal fold vibration phrase-finally is unaffected. Thus, the percept of devoicing results from a lengthening process that does not alter voicing duration. The present study will determine the extent to which final-lengthening is present in the speech of other speakers. The project is interesting because (a) Iron Range English was previously thought to exhibit devoicing, not final-lengthening [G. Underwood. Pub. Am. Dialect Society, 67 (1982)] and (b) results address how representations of sound are transferred into speech unfolding in time. Intuitions offered by articulatory phonology indicate timing of phrase-final frication lengthening in Iron Range English is not a reflex of a phonological rule, but instead of differentiated timing of independent gestures.
Final lowering: Fact, artifact or dialectal variation?
Authors: Arvaniti Amalia
Published: October 2013

The existence of final lowering has been disputed by Grabe (1998), who suggested that Liberman and Pierrehumbert’s 1984 finding was due to declination, as there was an extra syllable, ‘‘and,’’ between the last two accents in their materials (e.g. ‘‘RASPberries, MULberries and BRAMBLEberries’’). Arvaniti and Godjevac (2003), however, replicated the results of L&P with and without the extra syllable (c.f. ‘‘LIma beans, NAvy beans and SOY beans’’ vs. ‘‘LIma beans, GREEN beans and SOY beans’’). Here, the materials used in A&G were elicited from speakers of Standard British English (SBE). The results confirmed that the disagreement between L&P and Grabe is due to dialect: the SBE speakers did not exhibit final lowering under either condition. They showed less steep F0 slopes, so all accents after the first had similar scaling, while the last accent showed a rise (rather than a fall, as in American English), enhancing the lack of final lowering. These differences show that final lowering is better seen as a phonological device that a linguistic variety may employ in a given melody. Also, the cross-varietal comparison supports the view that F0 downtrends consist of distinct components (declination, final lowering), each of which may be utilized independently of the others.
Perception of stress in Thai
Authors: Nitisaroj Rattima
Published: October 2013

This study assesses the relative contribution of four parameters—duration, amplitude, fundamental frequency and vowel quality—to the perception of stress in Thai. Previous acoustic studies [e.g., S. Potisuk et al., Phonetica 53, 200–220 (1996)] have identified these four parameters as varying with stress, but perceptual tests in which these parameters are independently controlled have been needed. For this experiment, stimuli were created by digitally manipulating the four parameters in minimal pairs (compounds versus phrases) that differ only in stress pattern. Subjects were asked to choose between two contexts signaling whether the stimuli they heard contained a compound or a phrase token. Duration was found to be the strongest perceptual cue to stress. Sometimes, stress was signaled by the combination of duration and vowel quality. Results also showed an effect of subjects bias to judge noun–verb tokens as phrases and noun–noun tokens as compounds. If the bias conflicted with decision signaled by duration and vowel quality, effects caused by amplitude variation were observed. Finally, fundamental frequency did not appear to play any role in signifying stress. The results thus support the following hierarchy of perceptual correlates to stress in Thai: duration, vowel quality/ bias, amplitude, and fundamental frequency.
Source localization in environments with deterministic and stochastic uncertainties
Authors: Baer Ralph N. , Collins Michael D.
Published: October 2013

Focalization is an approach for localizing an acoustic source when there are uncertainties in the sound speed or other environmental parameters [J. Acoust. Soc. Am. 90, 1410–1422 (1991)]. The original work on focalization was based on deterministic parameters, but the concept was recently applied to problems involving uncertainties associated with internal waves [J. Acoust. Soc. Am. 115, 2550 (2004)]. Due to a parameter hierarchy in which source position outranks environmental parameters, it is often possible to localize a source without determining the true environmental parameters. This is a very fortunate situation, especially when dealing with stochastic parameters that would be essentially impossible to determine. Focalization is currently being extended to problems involving uncertainties in both deterministic and stochastic parameters. [Work sponsored by ONR.]
Object classification using low frequency scattering characteristics obtained from structural acoustic target models
Authors: Tesei Alessandra , Zampolli Mario
Published: October 2013

The capability to distinguish between different objects using low frequency scattered signals is a topic of fundamental interest to the sonar research community. To address this issue, a 3-D frequency domain finite element structural acoustics tool (FESTA) is used to synthesize multistatic scattered field time series from frequency sweeps. The time-frequency plots for scattering from a variety of manmade objects, like elastic spherical shells and cylindrical shells of various types, are analyzed, and the characteristic elastic effects are exploited to obtain low frequency classification clues. Comparisons between FESTA and other models are shown, and where available, experimental data are used to validate the results. Guidelines for the optimal level of modeling accuracy required to capture the relevant scattering details using the finite element tool are established, and the tradeoffs between accuracy, computation time and memory use are addressed.
Focal depth shifting of a time reversal mirror in a range-independent waveguide
Authors: Walker Shane C. , Roux Philippe , Kuperman William A.
Published: October 2013

A time reversal mirror refocuses back at the original probe source position. A goal has been to refocus at different positions without model based calculations. A method to refocus at different ranges has been developed earlier [Song et al., J. Acoust. Soc. Am. 103, 3224–3240 (1998)] using frequency shifting. Here we present a technique to refocus at different depths than the original probe source in a shallow ocean range-independent waveguide. The requirement is to collect data from various ranges at a single depth, as from a moving broadband radiator, over a distance sufficient to construct the relevant frequency-wavenumber structure of the waveguide. With this information, it is then possible to focus at arbitrary depth at any of the ranges that the probe source data were taken. Theory and laboratory measurements are presented.
Underwater sound pressures from marine pile driving
Authors: Rodkin Richard B. , Reyff James A.
Published: October 2013

Marine pile driving of steel shell piles has resulted in high underwater sound pressures that have been lethal to fish. High sound pressures have resulted in harassment of pinnepeds under the marine mammal protection act. Most waterways in the nation include fish and marine mammals that are protected by State and/or Federal agencies. Impacts from pile driving have contributed to costly construction delays for some major bridge projects. Recent construction activities in the marine environments of Northern California have provided the opportunity to characterize these sound pressures and evaluate control measures to protect fish and marine mammals. Sound control measures evaluated include different pile-driving methods, cofferdams (with and without water), confined air bubble curtain systems, and unconfined bubble curtain systems. Some control measures have achieved over 30 dB of noise reduction. Each situation, however, presents difficulties in achieving targeted reduction goals.
Issues for improved characterization of the acoustic field due to radiated noise of ships in shallow water environments
Authors: Barber Christopher , Becker Kyle M.
Published: October 2013

Estimation of the sound pressure levels radiated from ships to underwater sensors in littoral environments is a problem of increasing importance. Current areas of interest range from underwater surveillance and homeland security of ports, to the threat posed to naval vessels by influence mines. Recent literature addressing shallow water propagation has focused primarily on object detection using active sonar systems or on environmental characterization through inverse methods. While conclusions from these studies regarding the impact of environmental variability on acoustic propagation may be generally applicable, there are several additional areas that need to be investigated in order to understand the acoustic field at short ranges in shallow water. This presentation seeks to identify areas where further investigation may be warranted. In particular, existing propagation codes are examined for their applicability and/or limitations for the modeling of near-field radiation from nonsimple distributed sources, evaluation of complex source signals containing both broadband noise and narrow-band tones over a broad frequency range, and the impact of small-scale local variability. This presentation seeks to motivate a discussion toward new approaches and methodologies for addressing gaps between modeling requirements and capabilities. [Work supported by PEO-LMW, AIMS Program.]
A swept-frequency implosive source
Authors: Dorman LeRoy M. , Sauter Allan W.
Published: October 2013

Implosive underwater sound sources, such as the 20-liter single-shot device we have constructed, generally emit a rarefaction followed by a compression when the implosion is complete. Some purposes, however, are better served by a swept-frequency, rather than an impulsive, signature, since the lower peak pressures of the swept source are less likely to cause environmental damage. Our current plan for a repeating implosive source operates by venting a bubble (initially at ambient pressure) into a low-pressure receiver through a control valve. Performing this process in steps with abrupt pauses induces oscillations characteristic of the several sizes of the evolving bubble. From modeling the bubble oscillations using the Gilmore bubble equation, it appears feasible to produce a range of a factor of 2 in frequency, with a peak pressure of a megapascal. The design of the control valve, however, is challenging, as it was for the single-shot version. The repeater, however, operates on air, whose density and viscosity are lower.