bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of pulse laser induced vapor bubbles and shock waves to neurosurgery
Authors: Nakagawa Atsuhiro , Hirano Takayuki , Takayama Kazuyoshi , Saitoh Tsutomu
Published: October 2013

As a part of the basic research of tissue damages which occurred during ESWL treatments, shock/bubble interactions are found to be responsible to tissue damage. Having this background, we have been applying pulse laser induced vapor bubbles and shock waves to various neurosurgical therapies. Pulsed HO;YAG laser beams were transmitted via 0.6 mm diam optical fiber, whose edge was formed in a convex lens shape so as to enhance the laser beam focusing. Laser beams were focused inside a 2 mm diam water filled tube. Then, vapor bubbles and shock waves were generated, which successively drove a microwater jet. The mechanism of the initiation of bubbles and shock waves and consequential jet formation has been intensively investigated. It was found in in vitro experiments that microjets wonderfully pierced cerebral thrombi. Combining this system with a very small amount of fibrinolytic agents, cerebral thrombi were removed four times as efficiently as simple irradiation of pulsed laser beams.
Acoustic characteristics of a three-chamber hybrid silencer
Authors: Lee Iljae , Selamet Ahmet , Huff Norman T.
Published: October 2013

The acoustic characteristics of a hybrid silencer consisting of two identical single-pass, concentric, perforated dissipative chambers combined with a reactive Helmholtz resonator in between are investigated computationally and experimentally. Transmission loss predictions from a three-dimensional boundary element method are compared with experimental results obtained from an impedance tube setup in the absence of mean flow. In addition to the overall design, the effects of filling material density in dissipative chambers and the neck geometry of the reactive resonator are examined. The dissipative chambers are found to be effective at high frequencies, while the reactive resonator is shown, in general, to improve the acoustic attenuation at low frequencies typical of airborne noise in internal combustion engines running at low- to mid-speed range. The acoustic behavior near the resonance frequency is determined, however, to be sensitive to the duct length connecting dissipative and reactive chambers. Potential merits of the hybrid concept are assessed.
A study of microbarom wave packets
Authors: Olson John V. , Szuberla Curt A. L. , Wilson Charles R.
Published: October 2013

Microbaroms are a class of atmospheric infrasound that is characterized by narrow-band, nearly sinusoidal waveforms with periods near 5 s. These waves are generated by marine storms and are observed at infrasound sites across the globe. We report here on a study of microbarom wave packets. The data analyzed were obtained using the University of Alaska infrasound array comprised of 4 microphones located in central Alaska. Exploiting the narrow-band feature of the microbarom signals we are able to apply the Hilbert transform as a method for finding phase breaks in the signal. The phase breaks are interpreted to be the demarcations of the boundaries of individual wave packets. When applied to long sequences of microbaroms we find a broad distribution of packet lengths that diminishes monotonically with length, with a mean near 10 cycles and a variance nearly as large. Once the packets are identified, high-resolution estimators have been used to obtain the distribution of arrival directions at the array site. The ensemble of arrival directions is a reflection of the possibility of multiple sources and/or multiple propagation paths between the sources and the array.
A review optimization technique in structural acoustics
Authors: Marburg Steffen
Published: October 2013

In recent years, several activities on structural-acoustic optimization have been reported. The problem of structural-acoustic design optimiza- tion is characterized by nonlinearities. For that reason, it can only be dealt with numerically. Furthermore, the calculation of the objective function is usually very time-consuming since a multifield boundary value problem has to be solved. This paper summarizes results of a longer review paper. It will briefly discuss fast analysis techniques like FEM and BEM, objective functions, sensitivity analysis and optimization methods. Applications and parameter choices are categorized.
Identification of very closely spaced modes using an iterative algorithm
Authors: Allen Matt S. , Ginsberg Jerry H. , Ferri Aldo
Published: October 2013

The algorithm of mode isolation is a frequency domain method for processing measured response data in order to identify the modal properties of a system. It has been shown [M. V. Drexel and J. H. Ginsberg, Proceedings of the 19th IMAC, Orlando, FL, 5–8 February 2001] to accurately evaluate a pair of damped modes whose natural frequencies differ by an amount that is commensurate with the bandwidth of either mode. Here, SIMO measurement of a two-degree-of-freedom system is simulated analytically by adding white noise to the computed response. This system is selected because the natural frequency difference can be made as small as desired by adjusting a parameter that has little effect on the modal damping ratios in the range of interest. Analytically, the two normal modes are unique and mutually orthogonal if the frequency difference is nonzero, while repeated frequencies lead to two arbitrary, and not necessarily mutually orthogonal, modes. The present work explores the degree to which AMI tracks the analytical behavior, specifically, its ability to detect and characterize the modes with decreasing frequency difference.
The effect of high spatial resolution on techniques for experimental determination of loss factor
Authors: Carroll Gerard P. , Craun Matthew A. , DiPerna Daniel T.
Published: October 2013

Using a common set of mobility functions, various methods for determining loss factor are compared. A scanning laser Doppler vibrometer was used to measure these mobility functions with high spatial resolution for a plate and beam sample. The advantages of high spatial resolution are explored by estimating the loss factor using the complete set of mobility functions, and then comparing the results to those obtained using smaller subsets of the measured data. The plate and beam specimens are treated with a free layer damping. The loss factor determination methods include: synthesized time decay, classical modal analysis methods, the power input method, and complex wave number analysis. The merits/limitation of the damping measurement methods and the possible advantages of high spatial resolution are compared, along with results for both test specimens.
Solving conflicts between vowel systems
Authors: Escudero Paola
Published: October 2013

Conflicts may arise when listeners encounter a language with a different number of vowels. For instance, Spanish has 5 vowels, English at least 9 and Spanish listeners have many difficulties perceiving the /i/–/I/ contrast in some (though not all) varieties of English. Spanish learners of English solve this few-to-many problem by incorporating a new auditory dimension (vowel duration) into their categorization system. Perhaps surprisingly, the reverse scenario, namely encountering a language with fewer vowels, is also problematic. For instance, Dutch listeners of Spanish (Dutch is comparable to English in its vowel inventory size) have a boundary mismatch when listening to the Spanish /a/–/o/ contrast, and they hear the extra category /I/ when listening to Spanish /i/–/e/. Dutch learners of Spanish shift their boundaries toward what would be appropriate for the target language and they gradually stop perceiving the extra category. It turns out that both in few-to-many and many-to-few situations learners are capable of changing their perception to become like or almost like the native speakers of the target language. This can be explained within a formal model of speech perception and its development.
Spanish listeners’ use of vowel spectral properties as cues to post-vocalic consonant voicing in English
Authors: Morrison Geoffrey Stewart
Published: October 2013

Mexican Spanish listeners who had just arrived in an Anglophone region of Canada were tested on an edited-natural-speech continuum for Canadian English /bit bIt bid bId/ in which vowel duration and vowel spectral properties were varied, and in which consonant closures were silent. The Mexican Spanish listeners did not use vowel spectral properties to identify the vowel: Vowel identification was near chance level with a tendency for longer vowel stimuli to be identified as /i/. However, they did use vowel spectral properties to identify the consonant: Stimuli containing vowels with low F1 were identified as having voiceless consonants, and stimuli containing vowels with high F1 were identified as having voiced consonants. This presentation will consider possible explanations for this identification pattern for consonant voicing, and will also present the results of additional tests conducted with the same participants, namely: an identical perception test conducted 6 months after the participants’ arrival in Canada, English production tests using the same words conducted at the same time as the two perception tests, and a Spanish production test using the words /bit bid bíti bídi bití bidí/ conducted at the same time as the first set of English tests.
Could lack of experience with a second language be modeled as a hearing loss?
Authors: Padilla Monica , Shannon Robert V.
Published: October 2013

Previous studies have shown that listeners who learned a second language later in life have poorer speech recognition compared to native listeners, particularly under difficult listening conditions. We are interested in quantifying this demonstrated deficit experienced by non-native listeners as a function of the length of the exposure to the second language. In particular, we are interested in modeling it in terms of Plomp’s D factor. In Plomp’s model [J. Speech Hear. Res. 29, 146–154 (1986)], D is defined as a hearing loss due to distortion. We tested listeners whose first language is Spanish with English phonemes, words and sentences in noise, and with reduced spectral information. Preliminary results showed that D increased with an increased loss of spectral resolution. D also increased with the age of immersion in the second language. These results suggest that a lack of experience with the second language may be modeled as a type of hearing loss. Other issues of interest to us in this study are: the effect of the conflicting vowel spaces of the two languages in vowel recognition and the use of context by non-native listeners compared to native English listeners. [Work supported by NIDCD.]
Effects of native language experience in Spanish–English bilinguals’ ability to discriminate between two similar cross-language phonetic categories
Authors: Lugo-Marin Janielle , Connine Cynthia M.
Published: October 2013

Two phoneme monitoring experiments examined bilingual listeners’ (Spanish/English) ability to discriminate similar L2 (American English) phonemes (‘‘sh’’ and ‘‘ch’’) when L1 (Spanish) contains only one of the phonemes (‘‘ch’’). Experience with the ‘‘ch’’ phoneme in L1 was predicted to function as a perceptual magnet for the English phoneme ‘‘sh,’’ which is also a voiced palatal consonant. Both ‘‘sh’’ (Experiment 1) and ‘‘ch’’ (Experiment 2) targets were used. Target phonemes occurred in the initial or final position of a carrier word. Response times for the ‘‘sh’’ targets in initial position were slower than for the ‘‘ch’’ targets. In word-final position, the ‘‘ch’’ targets were detected more slowly than ‘‘sh’’ targets. Accuracy rates were comparable for the ‘‘sh’’ and the ‘‘ch’’ targets in both positions. The results are discussed in terms of categorical generalization of L2 phonemes that are similar to L1 phonemes, knowledge of phonological rules about the likelihood of a voiced palatal consonant in word-final position in L1, and experiential factors with L2.
Perceptual assimilation patterns and the perception of English /l/ and /ɹ/ by Japanese speakers
Authors: Aoyama Katsura , Flege James E.
Published: October 2013

This study examined the relationship between the perceptual assimilation patterns and the discrimination of English /l/ and /ɹ/ by Japanese speakers. The participants were 50 Japanese adults differing in their length of residence (LOR) in the U.S. In an identification task, they usually identified both English /l/ and /ɹ/ as Japanese /ɹ/. In a rating task, English /l/ was judged to be significantly more similar to Japanese /ɹ/ than English /ɹ/ was. The participants with a longer LOR gave lower similarity ratings for both English /l/ and /ɹ/ than those with a shorter LOR, suggesting that they became more aware of phonetic differences between Japanese /ɹ/ and English /l/ and /ɹ/. An exploratory analysis on similarity ratings was conducted for a subset of participants (N=28) based on their scores on /l/–/ɹ/ discrimination. Both relatively poor and relatively good discriminators judged /l/ to be more similar to Japanese /ɹ/ than /ɹ/, but the degree of difference between /l/ and /ɹ/ in terms of similarity ratings as Japanese /ɹ/ was smaller among poor discriminators than better discriminators. This suggests that the degree of ‘‘goodness-of-fit’’ as an L1 category may affect the ability to discriminate two L2 consonants. [Work supported by NIH.]
Does one plus one equal three in early simultaneous bilingual speech perception?
Authors: Sundara Megha
Published: October 2013

Over half the world’s population is bilingual, yet we know little about organization of phonetic abilities in early simultaneous bilinguals. In this study we tested bilingual French–English adults who had learned and used both languages simultaneously since birth. They were presented dental and alveolar stop consonants excised from real-word productions of French /t/ and English /d/, selected to insure that VOT values overlap. The alveolar-dental place distinction is not phonemic in either French or English. However, bilingual individuals are systematically exposed to this place distinction across their two native languages. Recent findings [Sundara and Polka, J. Acoust. Soc. Am. 110, 2685 (2001)] indicate that simultaneous bilinguals clearly produce this place distinction. Perception was assessed using a categorical AXB task with tokens produced by multiple talkers in both French and English. Assimilation data were also obtained using a keyword identification task in both languages. Performance of bilinguals was compared and contrasted with those of respective monolingual groups and with native Malayalam listeners (dental-alveolar distinction is phonemic in Malayalam). The findings provide insights into perceptual organization in simultaneous bilingual adults by addressing whether an emergent contrast, not evident in either monolingual group is observed in both perception and production of bilinguals.
A study of the connection between tidal velocities, soliton packets and acoustic signal losses
Authors: Chin-Bing Stanley A. , Warn-Varnas Alex C. , King David B. , Lamb Kevin G. , Hawkins James A. , Teixeira Marvi
Published: October 2013

Coupled ocean model and acoustic model simulations of soliton packets in the Yellow Sea have indicated that the environmental conditions necessary for anomalous signal losses can occur several times in a 24 h period. These conditions and the subsequent signal losses were observed in simulations made over an 80 h space–time evolution of soliton packets that were generated by a 0.7 m/s tidal velocity [Chin-Bing et al., J. Acoust. Soc. Am. 111, 2459 (2002)]. This particular tidal velocity was used to initiate the Lamb soliton model because the soliton packets that were generated compared favorably with SAR measurements of soliton packets in the Yellow Sea. The tidal velocities in this region can range from 0.3 m/s to 1.2 m/s. In this work we extend our simulations and analyses to include soliton packets generated by other tidal velocities in the 0.3–1.2 m/s band. Anomalous signal losses are again observed. Examples will be shown that illustrate the connections between the tidal velocities, the soliton packets that are generated by these tidal velocities, and the signal losses that can occur when acoustic signals are propagated through these soliton packets. [Work supported by ONR/NRL and by a High Performance Computing DoD grant.]
Computing the two-point correlation function directly from the transport equation using split-step Padé solutions
Authors: Huang Chen-Fen , Roux Philippe , Kuperman W. A.
Published: October 2013

The two-point correlation function that describes the correlation between an acoustic field at two depths as a function of range obeys a transport equation. Without making a frequency or narrow angle approximation, this equation can be solved by parabolic equation methods. The solution algorithm is split into two depth-steps using the alternating direction implicit (ADI) method to advance one range-step. Then, at each depth substep, the split-step Padé solution [M. D. Collins, J. Acoust. Soc. Am. 96, 382–385 (1994)] is used. Computations are confirmed against intensities computed from the indirect method that constructs the two-point function by an outer product of pressure vectors. Examples of the propagation of the vertical correlation for deep, shallow, and stochastic environments are presented.
Asymptotic methods of evaluation of acoustic fields generated by underwater moving sources
Authors: Rabinovich Vladimir S.
Published: October 2013

The problem of acoustic waves propagation from sources moving in stratified and almost-stratified waveguides simulating real oceanic waveguides is considered. It is assumed that acoustic sources move under water in the ocean with a subsonic variable velocity. Our approach for the evaluation of the acoustic field is based on the combination of two asymptotic methods: (1) The asymptotic analysis of the Green’s function for almost-stratified waveguides by the operator ray method with respect to a small parameter which characterizes the variation of waveguides in the horizontal direction; (2) a subsequent asymptotic analysis of the integral representation of the field generated by a moving source by the two-dimensional stationary phase method with respect to a large parameter which characterizes the smallness of variations of the amplitude of source and the smallness of the vertical component of the source speed. Asymptotic formulas for the acoustic pressure, for the mode and time Doppler effects, are obtained. These formulas have a clear physical meaning and are convenient for the numerical simulation of the problem.
New software for room acoustics simulation: A study of its performance and validation by an international comparison
Authors: Camilo Thiago S. , Medrado Ludimila O. , Tenenbaum Roberto A.
Published: October 2013

Nowadays, with the increasing capacity of personal computers, software in room acoustics simulation is being developed all over the world by strong architectural acoustic groups, as a practical and reliable way to evaluate the sound quality of a room. However, software must be exaustively tested in order to be recognized as a trustworthy tool for modern acoustical design. In this paper, a new software tool in room acoustics simulation, RAIOS, is presented. A hybrid technique, which uses the ray-tracing method to simulate the first part of the impulse response and an energy transition algorithm to compute its reverberant tail, for a room with arbitrary geometry is described. All the parameters for room acoustics quality, following ISO 3382 standard, are also computed. The effects of filtering, reflection, and absorption on the walls and in the air are considered in the model. The software has participated in Round Robin 3, promoted by PTB, Germany. The results of phase three of RR3 (the most complex one) are presented in this paper. Comparison with other software is given. If the experimental data of the PTB studio are available before the end of this year, then comparisons will be made.
Normal incidence sound absorption measurement of individual patches in a reverberation room
Authors: Massarani Paulo , Muller Swen
Published: October 2013

This work presents results of sound absorption measurement of plain patches inside a reverberation room. An in situ method has been applied (ISO 13472-1). The main purpose is to support the installation of diffusers in a reverberation room for random incidence sound absorption measurements. The in situ method is based on impulse response evaluation, in which the incident and reflected front waves can be windowed to isolate them from the room reflections. Due to the small areas of the patches (around 1 square meter) and the high reverberation time, some special steps had to be performed. In order to establish an impulse response measurement with high SNR, a long sweep sine signal with low-frequency emphasis has been used as the excitation signal. Applying the subtraction technique permitted locating the microphone very close to the sample. The sound absorption coefficient of each patch allowed selecting the most uniform set of material to compose the area required by the ISO 354. The patches not used were tested in an impedance tube, showing a good agreement between the results from the two methods. Thus, the in situ method allows quick measurement of plain samples laid on the room floor while preserving the material integrity.
An experimental study of the variation of absorption coefficients for fiberglass with altitude
Authors: Godfrey Richard D.
Published: October 2013

ASTM C 423 specifies requirements for air temperature and relative humidity during decay rate measurements, but does not address variations in air density even though this parameter decreases with increasing altitude. At constant temperature, air density decreases by approximately 20% from sea level to 5000 feet altitude, resulting in about 20% decrease in its acoustic impedance. In a previous paper, an analysis based on Mechels design charts (normal and diffuse) showed significant changes in predicted absorption coefficients with altitude. Due to the difficulties in depressurizing a reverberation chamber, a normal incidence study was conducted to experimentally investigate this effect by placing an impedance tube in a vacuum chamber. Fiberglass materials were tested at various amounts of vacuum. The measured results followed reasonably well those predicted by the analysis for normal incidence. Based on these results, comparison of absorption coefficients measured at substantial altitude with those measured at sea level is discouraged. It is suggested that notes be added to the ASTM standards cautioning users about these limitations or limiting their use to ambient pressures within a couple inches Hg of standard sea level conditions.
Vocalization of migrating humpback whales over 14 years as an indicator of stock size
Authors: Cato Douglas H. , Paterson Robert , Paterson Patricia
Published: October 2013

Acoustic monitoring of migrating humpback whales has been carried out since 1981 in conjunction with visual surveys from Point Lookout, Stradbroke Island, on the east coast of Australia. Recordings were made from a drifting boat a few kilometers seaward of the observation point, during the peak of at least one of the migrations each year. This paper presents an analysis of song vocalization in relation to the observed movements of humpback whales in order to determine the vocalization rates and their value as an index of relative abundance. The proportion of whales singing as they passed Point Lookout was ∼5% during the northern migration (towards the breeding grounds) and ∼13% during the southern migration, the difference being statistically significant. There was no significant trend in the proportion of singers as the stock size increased by more than a factor of 3. From 1982 to 1993, the number of singers passing per 10 h during the southern migration increased at a rate of 10.6% (95 confidence interval 3%–19%), consistent with the rate of increase of 11.7% obtained from the visual survey over a similar period.
Measurements of ambient bubble populations with a multibeam sonar
Authors: Weber Thomas C. , Bradley David , Culver R. Lee , Lyons Anthony P. , Adelman Steven G.
Published: October 2013

A 240 kHz multibeam sonar was deployed on the research platform FLIP off the coast of San Diego for two weeks in July, 2002. The sonar was oriented to measure backscattering from the ambient bubble field near the ocean surface. A bubble population density spectrum shape described by Novarini et al. [IEEE J. Ocean. Eng. 23, 423–438 (1998)] is assumed, and the spectrum level is shifted up or down to fit the backscatter measurements. This allows the bubble population to be inferred from the single frequency measurement. The wide field of view for the sonar (1.5° beams distributed over a 150° swath) allowed the spatial structure of the bubble field to be observed over the time period, and compared with environmental measurements including wind/wave conditions and the spatial variation of temperature and salinity. [Work supported by ONR Code 321US.]
On the multifrequency method of the range dependent transversal current monitoring
Authors: Charnotskii Mikhail , Fuks Goseph , Naugolnykh Konstantin , Di Iorio Daniela
Published: October 2013

Transverse flow of inhomogeneous current produces fluctuations of the acoustic signal passing through it. These fluctuations vary with the signal frequency due to the variation of the Fresnel zone size. Respectively, fluctuations of signals at two different frequencies are coherent in a low-frequency range of the spectrum and noncoherent in the high-frequency band when ocean inhomogeneities are smaller than the transverse size of the Fresnel zone. The frequency cutoff of the coherence function of signals at different frequencies depends on current flow characteristics. Di Iorio and Farmer [J. Acoust. Soc. Am. 100, 814–834 (1996)] describe high-frequency acoustic scintillation measurements in a tidally forced flow through a Cordova Channel specifically designed to characterize the two-dimensional angle of arrival fluctuations in terms of the mean and turbulent properties of sound speed and current. We present new results from this data set which was collected in an alternating dual frequency mode. The multifrequency technique gives results which are consistent with previous results, but eventually will allow the measurement of current profiles across the channel.
Wave number inversion in a noisy shallow-water waveguide
Authors: Cassereau Didier , Roux Philippe
Published: October 2013

The calculation of wave numbers resulting from the propagation of an acoustic wave in a noise shallow-water waveguide like the ocean is addressed. There are no particular assumptions regarding the acoustic properties of the waveguide; we just start from an experimental measurement of the acoustic field created by a source and measured on different points of a receiving transducer array. In 1999, a high-resolution wave number inversion algorithm was proposed and compared to the Cramer–Rao lower bounds. Both methods have been implemented and compared using the same set of simulated data. We propose a complete overview of the main characteristics of these two algorithms, in terms of the accuracy, computation time, dependence on noise, etc. The same comparisons will be presented with simulated and experimental data.
Study of anisotropy by transient elastography
Authors: Gennisson Jean-Luc , Catheline Stefan , Chaffa Sana , Fink Mathias
Published: October 2013

From the low-frequency (150 Hz) shear-waves’ velocity, transient elastography can precisely measure the Youngs modulus in isotropic soft tissues. Using polarized shear waves, the character of an anisotropic media like fiber muscle is clearly visible. The polarization of elastic shear waves is obtained by the use of a rod (3×80 mm) as a low-frequency source. Indeed, the displacement field induced within a medium when an acoustic pulse (150 Hz) is applied at the surface by a rod is no more axisymmetric: the component of the displacement parallel to the rod is smaller than the component perpendicular to the rod. These polarized shear waves are well predicted by a numerical simulation of theoretical Greens functions. It is shown that the shear-wave velocities in a beef muscle (biceps femoris) strongly depend on the position of the rod as regard to the fibers. These results show that the anisotropic model for this muscle is the hexagonal system. Results in vivo on man biceps also show the existence of a low and a fast shear wave. We have started on this subject a collaboration with the myology institute at the hospital La Piti Salptrire in Paris.
Use of complex source points to simplify Gaussian beam synthesis
Authors: Forsythe Stephen
Published: October 2013

It is often desirable to generate the acoustic field due to a so-called Gaussian beam. One way to do this is to use the free-space Greens function for the acoustic field and to sum small area sources over a circular plate with the appropriate shading for the desired Gaussian beam. For very high frequencies and narrow beams, the computation time to give an accurate sum can be large when calculating the sum for many points in the acoustic field. An alternate approach comes from the use of a single point source with complex coordinates R=[Xr+iXi,Yr+iYi,Zr+iZi]. When this complex source point is used in the free-space Greens function, the formal expressions for pressure and particle velocity can be used if careful attention is paid to the interpretation of the complex distance, r, that arises in the exp(ikr)/r. The singularity is no longer a single point in the case of a complex source, but a circular disk. The far field of a complex source point is a good approximation to a Gaussian beam. Several computational uses of the technique will be demonstrated. [Work supported by ONR.]
Modal analysis of an archtop guitar
Authors: Wiese Cassandra , Rossing Thomas D.
Published: October 2013

Although archtop guitars are very popular with jazz musicians, their acoustical properties have not been studied nearly as much as their flattop cousins. Their plates are carved, like those of violins or cellos, so internal bracing is minimal. Bridges are usually not fixed to the top plate. We describe the modes of vibration of an archtop guitar, determined with the help of holographic interferometry, with those of a flattop guitar. Some modes show a close relationship, while others are quite different.
Noise labeling in Brazil
Authors: de Araujo Marco A. N. , Massarani Paulo M. , de Azevedo Jose A. J. , Gerges Samir N. Y.
Published: October 2013

The Brazilian Silence Program, created in 1990 by the Brazilian Ministry of Environment, advocates the production and use of equipment with lower noise level. The subcommittee of Noise Labeling of the Brazilian Committee of Certification is composed of INMETRO acoustic specialists to organize and implement the Brazilian Labeling Program. This subcommittee elaborated the label form and test procedure. The noise-labeling program will first concentrate on the following household devices, both manufactured in Brazil or imported from abroad; mixers, blenders, hairdryers, refrigerators, and vacuum cleaners. The label should contain the sound-power level in dBA. INMETRO or other credited laboratories are responsible for the measurements. The ISO 4871, 3740 (1 to 5), ISO 8960, and IEC 704 (1 to 4) and also the equivalent Brazilian standards are used for the measurements, such as ABNT NBR 13910-1. The main objective of the label is to inform the consumer about the emitted noise level. The label offers the noise parameter to be used by the consumer when comparing devices, considering price, performance, and now also noise. No restriction for noise level was established.
Diffraction by polyhedral angle: Field in vicinity of singular ray
Authors: Borovikov Vladimir A.
Published: October 2013

If the plane acoustic wave hits a polyhedral angle, the scattered field consists of an incident wave, of its reflections from the angle’s facets, of primary edge waves excited at angle’s edges, and of a spherical wave excited at the angle’s vertex. It is supposed for simplicity that the geometry of the problem is such that there is no secondary and subsequent edge waves. There are two types of light–shadow boundaries: first for incident and reflected waves and second for edge waves. As is well known, the field in penumbras is expressed via a Fresnel integral. The incident wave’s ray passing through the vertex and its reflections from facets are singular rays belonging to the light–shadow boundaries of both types. It will be shown that the field in the vicinity of a singular ray is expressed via a Fresnel intergal and via a generalized Fresnel integral G(p,q) which was introduced in [P. S. Clemmov and T. B. A. Senior, Proc. Cambridge Philos. Soc. 9, 570–572 (1953); see also V. A. Borovikov, Uniform Stationary Phase Method, IEE Electromagnetic Series 40, London, 1994]. This result is valid for an elastic incident wave as well.
Exercises in ‘‘absurdity:’’ Interactions between flapping and tongue position in American English with implications for speech motor planning
Authors: Gick Bryan
Published: October 2013

Articulatory conflicts can prevent the achievement of production targets, forcing decisions regarding the resolution of these conflicts. Observing which strategies are chosen can help us to understand relative priorities in speech planning and phonology [Wood, J. Phonetics (1996)]. One particularly felicitous case of such a conflict is the interaction between tongue tip position for English /r/ and vowels and the flapping of /t/ and /d/. This study presents data from ultrasound imaging of tongue kinematics and acoustic output during productions of words containing sequences of vowels, flaps and /r/’s. Results show that for at least some speakers of North American English, a flap may be produced either up (from tip-down to retroflex, as in ‘‘Jupiter’’) or down (from retroflex to tip-down, as in ‘‘puberty’’). For the one speaker analyzed to date, r-flap-r (‘‘frankfurter’’) and V-flap-V (‘‘taffeta’’) begin in the correct position for the leftmost segment in each sequence (retroflex and tip-down, respectively). However, ‘‘double flaps’’ start in tongue down position (‘‘Saturday,’’ ‘‘editor’’), even when it forces compromise of multiple vowel/liquid tongue positions (‘‘absurdity’’). Flap kinematics thus take precedence over tongue position (and therefore acoustic realization) for vowels/liquids. Additional results will be presented. [Research supported by NSERC and NIH.]
A parametric area function model of three female vocal tracts based on orthogonal modes
Authors: Story Brad
Published: October 2013

Image sets corresponding to 11 vowels were obtained from each of 3 female speakers using Magnetic Resonance Imaging. From these images, vocal tract area functions for each vowel were determined. Each speaker’s 11 area functions were then decomposed into a set of orthogonal basis functions or ‘‘modes’’ and mean vowel area functions. Similar to previous work with male vocal tract data [Story and Titze, J. Phon. (1998)], two orthogonal modes accounted for nearly 90% of the variance within each speaker’s vowel set, while the mean area functions serve as neutral, but unique, tract shapes around which the vowels are formed. For each speaker, the two most significant modes and the mean area function were used to develop a parametric model that allowed for calculation of an arbitrary area function based on coefficients of the modes. With these models a hypothetical vowel space was generated in terms of F1, F2 pairs (first and second formant frequencies). The vowel spaces for each speaker were then used to map time-varying formant frequencies extracted from natural speech to the modal coefficients of their respective parametric models. This effectively produces a time-varying area function suitable for synthesis of speech. [Work supported by NIH R01-DC04789.]
Temporal differences in Serbian palatal affricates
Authors: Miller-Ockhuizen Amanda , Zec Draga
Published: October 2013

We report on temporal cues associated with contrastive palatal affricates in Serbian in minimal pairs such as veche evening (apical) and vec’e bigger (laminal). These sounds have been difficult to distinguish using articulatory features. We investigated risetime, rate of rise (ROR), closure duration, release duration and segmental duration in four vowel contexts and two word positions. The apical affricate displays shorter risetime, ROR and closure duration, with longer release duration, while the laminal affricate displays longer risetime, ROR and closure duration, with shorter release duration. While risetime differentiates fricatives from affricates (Howell and Rosen, 1983), and ROR differentiates stops from fricatives (Weigelt et al., 1990), this is the first study to demonstrate risetime and ROR distinguishing two affricates. Rate of rise distinguishes these two affricates from the palatal fricative and alveolar stop allowing for the maintenance of contrast over the three-way distinction. Risetime correlates with closure proportional providing evidence for a universal physical relationship between closure duration and risetime. Differences in closure duration are compensated for by differences in release duration, allowing the overall segmental duration of the two classes of affricates to be similar.
Wideband link-budget analysis for undersea acoustic signaling
Authors: Rice Joseph A. , Hansen Joseph T.
Published: October 2013

Link-budget analysis is commonly applied to satellite and wireless communications for estimating the signal-to-noise ratio (SNR) at the receiver. Link-budget analysis considers transmitter power, transmitter antenna gain, channel losses, channel noise, and receiver antenna gain. For underwater signaling, the terms of the sonar equation readily translate to a formulation of the link budget. However, the strong frequency dependence of underwater acoustic propagation requires special consideration, and is represented as an intermediate result called the channel SNR. The channel SNR includes ambient-noise and transmission-loss components. Several acoustic communication and navigation problems are addressed through wideband link-budget analyses. [Work sponsored by ONR 321.]
Scale adaptive channel estimation
Authors: Gendron Paul J. , Yang T. C.
Published: October 2013

Channel (linear operator) estimation requires either a-priori knowledge or joint estimation of channel temporal coherence. This information serves to condition the estimation process reducing estimator variance. Kalman-like conditional expectation algorithms have exhibited success by modeling the channel response via time evolution either assuming coherence time a priori or jointly estimating it. With coherence time viewed as a ‘‘time resolution’’ property of the channel response rather than a ‘‘time evolution’’ property a new computational structure results. From this viewpoint we introduce a new channel estimation algorithm ‘‘in-scale’’ vice ‘‘in-time.’’ In such a framework detail is added, or synonymously coherence time is successively reduced, to meet a maximum a posteriori (MAP) criteria. The algorithm starts with a ‘‘mean’’ (time invariant) estimate and gradually adds detail evolving in scale until the MAP is attained. Computationally the algorithm exploits conjugate gradient directions recursing from low resolution to higher resolution until the requisite prior complexity (estimated via an empirical Bayes method) and data fidelity are met. Scale projections are computed efficiently and dimension reduction is aided via a wavelet decomposition. Explanations in terms of the minimum description length principle are also provided.
Robustness of null broadening against source motion
Authors: Song Heechun , Kuperman William , Hodgkiss William , Gerstoft Peter , Kim Jaesoo
Published: October 2013

Adaptive array beamforming achieves high resolution and sidelobe suppression by producing sharp nulls in the adaptive beampattern when using sample matrix inversion (SMI). Large aperture sonar arrays with many elements have small resolution cells and interferers may move through many resolution cells in the time required for accumulating a full-rank sample covariance matrix. In addition, longer duration snapshots are required due to the longer transit time across the array. This leads to ‘‘snapshot deficient’’ processing. In this paper, the null broadening technique originally developed for an ideal stationary problem is extended to the snapshot deficient problem arising from nonstationarity of the background interference. Null broadening allows the strong interferers to move through resolution cells and increases the number of degrees of freedom, thereby improving the detection of weak stationary signals. Numerical simulations demonstrate the robustness of the null broadening approach.
Detector analysis for shallow water active sonar
Authors: Pastore Thomas J. , Phillips Michael E.
Published: October 2013

SPAWAR Systems Center–San Diego, in concert with the Office of Naval Research (ONR) and Defense Advanced Research Projects Agency (DARPA) has designed and built a proof-of-concept broadband biomimetic sonar. This proof-of-concept sonar emulates a dolphin biosonar system; emitted broadband signals approximate the frequency and time domain characteristics of signals produced by echolocating dolphins, the receive system is spatially modeled after the binaural geometry of the dolphin, and signal processing algorithms incorporate sequential integration of aspect varying returns. As with any sonar, object detection in shallow water while maintaining an acceptable false alarm rate is an important problem. A comprehensive parametric analysis of detection algorithms is presented, focusing primarily on two detector strategies: a matched filter and a spectral detector. The spectral detector compares the ratio of in-band to out-of-band power, and thus functions something like a phase-incoherent matched filter. This computationally efficient detector is shown to perform well with high proportional bandwidth signals. The detector (either matched filter or spectral) is coupled with an alpha–beta tracker which maintains a running noise estimate and calculates signal excess above the estimated noise level which is compared to a fixed threshold.
Arrival time determined by vertical array: Experimental results in shallow water
Authors: Too Gee-Pinn J. , Wang Chih-Chung K. , Chen Chifang , Lynch Jim , Newhall Arthur
Published: October 2013

The arrival time determined by vertical array is a useful parameter to apply matched field processing (MFP) methods for source localization. In this paper, the procedure including wavelet transform for extracting the signal, adaptive filter for retrieving the signal, and wigner-vill distribution for determining the arrival time between sensors is presented. During the South China Sea ASIAEX Experiment, the 103 m deep source was towed by a ship. The data receiving system was a satellite–buoy underwater measurement system with a 16-element vertical line array. The experiment showed that the data was collected with very good quality. Results of this procedure are more efficient, and faster than earlier results based on power spectrum for MFP.
Impulse response of a two-dimensional rough surface overlying an inhomogeneous, nondispersive medium: A hybrid model
Authors: Keiffer Richard , Novarini Jorge , Norton Guy
Published: October 2013

A numerical model to calculate the impulse response of a two-dimensional, impenetrable, rough surface directly in the time domain has been recently introduced [R. S. Keiffer and J. C. Novarini, J. Acoust. Soc. Am. 107, 27–39 (2000)]. This model is based on wedge diffraction theory and assumes the half-space containing the source and receiver is homogeneous. In this work, the model is extended to handle media where the index of refraction varies with depth by merging the scattering model with a ray-based propagation model. The resulting hybrid model is tested against a finite-difference time-domain (FDTD) method for backscattering from a corrugated surface in the presence of a refractive layer. This new model can be applied, for example, to calculate acoustic reverberation from the sea surface in cases where the water mass is inhomogeneous and dispersion is negligible. [Work supported by ONR/NRL (PE 61153N-32) and by grants of computer time DoD HPC Shared Resource Center at Stennis Space Center, MS.]
Modeling the aeroacoustics of axial fans from CFD calculations
Authors: Salesky Alexandre , Hennemand Vincent , Kouidri Smaine , Berthelot Yves
Published: October 2013

The main source of aeroacoustic noise in axial fans is the distribution of the fluctuating, unsteady, aerodynamic forces on the blades. Numerical simulations were carried out with the CFD code (NUMECA), first with steady flow conditions to validate the aerolic performances (pressure drop as a function of flow rate) of the simulated six-bladed axial fans. Simulations were then made with unsteady flows to compute the fluctuating force distributions on the blades. The turbulence was modeled either with the Baldwin–Lomax model or with the K-epsilon model (extended wall function). The numerical results were satisfactory both in terms of numerical convergence and in terms of the physical characteristic of the forces acting on the blades. The numerical results were then coupled into an in-house aeroacoustics code that computes the farfield radiated noise spectrum and directivity, based on the Ffowcs-Williams Hawkings formulation, or alternatively, on the simpler Lowson model. Results compared favorably with data obtained under nonanechoic conditions, based upon ISO 5801 and ISO 5136 standards.
Acoustic confort at home: Noise emitted by house installations. Recommendations in order to avoid such noise
Authors: Jimenez Santiago
Published: October 2013

The present survey consists of the analysis and the study of the solutions used at present in the installations of water supply and elevators. It has been carried out from the acoustic point of view. In order to achieve a thorough study a pilot plant was built in the Laboratory of Acoustics of the School of Industrial Engineering of Terrassa. This pilot plant reproduced different kinds of installations of the water supply in houses. And it has allowed us to systematize the measures and also to determine the optimum solutions from the acoustic perspective. In accordance with the objectives and the process of the survey, the solutions regularly employed in the facilities of water supply and elevators in houses have been analyzed, and levels of noise associated to these facilities have been also presented. A summary of the results obtained in the plant has been included, according to diverse variables. Both the conclusions of the analysis of the data obtained in the laboratory and those of the installations of the houses have been also compared, which has allowed us to describe a series of suggestions with the purpose of reducing the acoustic emission of this type of installations, and increase the acoustic comfort at home. (To be presented in Spanish.)