bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of uncertainty in the estimation of velocity and direction-of-arrival for atmospheric infrasound signals
Authors: Szuberla Curt A. L. , Olson John V.
Published: October 2013

Upon the detection of an atmospheric infrasound signal, the problem of precisely estimating the signal’s velocity (v) and direction-of-arrival (θ) arises. Multiple sources, multipath, medium anisotropies, and other propagation effects can all degrade precision; however, uncertainty in the estimates of v and θ is fundamentally governed by array geometry and the estimation of time delays across the array. Typically, as in the Comprehensive Test Ban Treaty Organzation Provisional Technical Secretariat (CTBTO/PTS) specification for data from infrasound stations, the Cramér–Rao lower bound is invoked to ascertain the uncertainties associated with v and θ. As this theoretical lower limit is often overly conservative, a more general, and useful, approach to calculate these uncertainties is developed. Examples of this uncertainty determination are presented for typical impulsive and continuous atmospheric infrasound signals received at arrays in Windless Bight, Antarctica and Fairbanks, Alaska. Since the determination of v and θ serves as primary input to any propogation model, it is critical that uncertainties in these estimates be addressed. As an extension of this work, an interactive graphical tool is constructed to assist in the analysis of performance bounds for arbitrary array geometries and signal characteristics.
Autocorrelation of vibration data for flaw detection
Authors: Pardue Sally J. , Vasantharao Brahmaji
Published: October 2013

The autocorrelation of a structural FRF (frequency response function) can be used to extract structural parameters, such as length from a transversely vibrating beam. Further work has shown that the technique can also detect flaws in the structure. The frequency spacing between resonant peaks is extracted from the autocorrelation process and relates to the length of the object. Indicators of flaws in the structure were observed in the autocorrelation values plotted against a length axis. The first test structure was a free–free nine feet long, one inch diameter aluminum rod. The flaws examined were machined slots of various widths cut into the rod. The concept was further explored numerically in ANSYS models of the same aluminum bar using much smaller flaw sizes. Now, the concept of autocorrelation of the FRF is being applied to composite beams, 8 ply, 10 in. long, 0.052 in. thick, 1 in. wide. Indicators in the vibration data are sought to relate to porosity levels of the manufactured composite beams.
Effects of circumferential air gaps on the measurement of the absorption coefficient of poroelastic materials
Authors: Pilon Dominic , Panneton Raymond
Published: October 2013

The influence of mounting conditions on the measurement of the absorption coefficient is investigated. More specifically, the effects of circumferential air gaps on poroelastic materials inside the standing wave tube are studied. The objective is to identify the materials, in terms of a ratio based on their physical properties, for which it is possible to measure the theoretical absorption coefficient using the tube. The difference, or error, between the measured and theoretical absorption coefficient is evaluated for a wide range of materials with various sample sizes. These errors are then sorted in terms of the chosen ratio. It is shown that for certain values of the ratio, the theoretical absorption coefficient can be efficiently measured using the standing wave tube. Through the use of this acousto-visco-inertial criteria, an experimenter can determine which absorption is going to be measured: the theoretical absorption coefficient or one that will be influenced by either the circumferential air gaps or the size of the sample.
Within- and across-language acoustic variability of vowels spoken in different phonetic and prosodic contexts: American English, North German, and Parisian French
Authors: Strange Winifred , Weber Andrea , Levy Erika , Shafiro Valeriy , Nishi Kanae
Published: October 2013

This project investigates the acoustic variability of vowels produced in multisyllabic nonsense words /cvC1VC2(v)/ in carrier sentences by speakers of American English (AE), Parisian French (PF), and North German (NG). Variables under examination are (1) immediate phonetic context (C1=b,d; C2=b,d,p,t), (2) sentence prominence (narrow focus versus postfocus), and speaking rate (normal vs rapid). Preliminary results show that for AE vowels, phonetic context produces large differences (2–3 bark) in midpoint F2 values for mid-to-high back vowels, reflecting allophonic fronting of these vowels in alveolar context. Much smaller increases in F2 (∼1 bark) were found for both PF and NG mid/high back vowels in alveolar contexts. Most AE speakers showed little or no effect of sentence focus or speaking rate on the degree of fronting of back vowels in alveolar context. PF speakers produced more fronted mid/high back vowels in postfocused context than did NG and AE speakers. NG and PF speakers showed relatively greater F1 undershoot in low vowels in postfocus context than for AE speakers. These within- and across-language differences in the effect of prosodic and phonetic context on vowel acoustics reflect both language-universal constraints and language-specific rules for contextual warping of vowel spaces.
Neural activation during the discrimination of native and non-native speech contrasts by American and Japanese adults
Authors: Tsao Feng-Ming , Kuhl Patricia K. , Liu Huei-Mei
Published: October 2013

Language experience influences speech perception in adults. Adult speakers have been shown to experience difficulty when discriminating non-native consonants that are not phonemic in the native phonetic repertoire. The present study examined behavioral and neural differences in the processes underlying the perception of native and non-native speech sounds. American-English and Japanese native-speaking adults participated in a functional magnetic resonance imaging (fMRI) study. The study focused on three consonants: the American English /r–l/ consonants and Japanese /r/. The investigation focused on neural correlates of both Kuhl’s perceptual magnet effect (PME) and the boundary effects typical of categorical perception (CP). Subjects performed in a behavioral task in which they identified provided goodness ratings, and discriminated stimuli varying in formants 2 and 3. Results will be discussed in relation to cortical activation patterns related to the PME and CP boundary effect for native and foreign language contrasts, and the effects of language experience on brain organization. [This work was supported by NIH grant (HD37954) and Talaris Institute.]
Brain potentials in response to native and non-native speech contrasts in 11-month-old American infants
Authors: Rivera-Gaxiola M. , Silva-Pereyra J. , Garcia-Sierra A. , Klarman L. , Kuhl P. K.
Published: October 2013

Behavioral studies show that 6- to 8-month-old infants discriminate both native and non-native phonetic differences, but that by 10–12 months of age, infants’ perceptual sensitivities decline to many non-native contrasts. Kuhl et al. (1997) and Tsao et al. (2000) have also shown an enhancement in sensitivity to native contrasts, which was also shown by Cheour et al. (1998) using electrophysiological methods. Using both behavior and ERPs, Rivera-Gaxiola et al. (2000) reported MMNs in native English speaking adults for a non-native contrast that the same adults did not overtly discriminate. We here report auditory ERPs to native and non-native VOT contrasts in 11-month-old monolingual American infants (N=16). Stimuli were presented as a double-oddball paradigm. Continuous EEG was recorded using electrocaps. ERPs were obtained off-line using standard methods. The results show that 11-month-olds display differential brain activity for native and non-native contrasts. A clear, widely distributed phonetic MMN can be observed for the native contrast, while the non-native acoustic differences pre-attentively detected are shown as differences in the first positive peak of the complex. A smaller centro-parietal negativity was also observed for the non-native contrast. [Work supported by NIH (HD 37954) and by the Talaris Research Institute.]
Short-term immersion can change the location of a phonetic category boundary
Authors: Damgren-Hojen Anders
Published: October 2013

In this study the effect of immersion in a second-language (L2) speaking environment on the perception and production of English sibilants by native (L1) speakers of Danish is examined. Three groups of subjects participated. Fourteen Danish au pairs or exchange students were tested before and after a 6–12 month immersion period. Eleven Danish control subjects were tested twice without immersion. Five native English baseline subjects were tested once. Danes tend to assimilate English /s/–/sh/ to two different Danish sound categories. However, the Danish /sh/ is palatalized and has more high frequency energy than English /sh/. If the immersed subjects changed their mental specifications for /sh/ after massive input of the more low frequency English /sh/ during immersion, one might expect a perceptual category boundary shift for /s/–sh/. This shift was indeed found, using an interpolated synthetic /s/–/sh/ continuum for the identification and discrimination in both an English and a Danish language set. Production was measured using spectral moments. However, there was no clear indication of a more authentic English pronunication of /sh/ after immersion than before. The results pertain to questions regarding the reorganization of phonetic categories after L2 experience, interactions between L1 and L2 phonetic systems, and the relation between perception and production.
Perception of American English glide consonants by Danish listeners
Authors: Best Catherine T. , Bohn Ocke-Schwen
Published: October 2013

Previous research has found both phonological and phonetic influences from the native language on perception of American English (AE) /r–l/, /w–r/, /w–j/ by Japanese and French speakers. This study examined native language effects on perception of the same stimuli by Danish listeners with minimal English experience. Danish contrasts /r–l/, but realizes them differently than AE, as pharyngeal versus nonvelarized lateral approximants. It has /j/ but lacks /w/; however, /v/ is realized as an unrounded labiodental approximant similar to /w/. Thus, on purely phonological grounds, Danes should have greater difficulty with AE /w–j/ and /w–r/ than /r–l/. On phonetic grounds, however, all three contrasts should be assimilated to Danish contrasts, and therefore categorized and discriminated quite well. Forced-choice identification was highly categorical for all three contrasts. However, A×B tests revealed a native-like discrimination peak only for /w–r/; /r–l/ showed a lower and less well-defined peak, whereas /w–j/ was discriminated at ceiling except for the /j/ end of the continuum. These results are consistent with previous evidence that both phonological and phonetic properties of the native language affect non-native speech perception. The findings will be compared to prior cross-language research, and discussed in light of phonological differences among the listeners’ languages.
Age of immersion as a predictor of foreign accent
Authors: Munro Miles , Mann Virginia
Published: October 2013

This study examined the relationship between Age of Immersion (AOI) and the Degree of Phonological Accent (DPA) that native-English-speaking judges perceived in the speech of Mandarin speakers who learned English as a second language. AOI and speech samples of variable length and linguistic context (single words, sentences, a short paragraph, and a self-generated picture narration) were collected from the target group (n=32, AOI=3–16) and from native speaker controls (n=4, AOI=0). These were judged by a native speaker panel (n=14) using a continuous scale, along with measurements of confidence. Judging was broken over 3 separate visits. A set of similar samples and speakers was repeated at the onset and termination of the main rating task of each visit to ensure reliability. No single AOI was found for a ‘‘Critical Period’’ (CP). Instead, DPA was found to increase in a highly linear manner with AOI. In general, ratings of DPA began to increase at about AOI=5, maxing out as early as AOI=7, although near-native ratings were given to some speakers whose AOI was greater than 5, especially in the case of female speakers. Thus DPA can be linearly predicted with AOI, though individual speakers are fairly variable after AOI=5.
Modeling heavy-tailed correlated clutter via wavelet packet bases with application to seismic event estimation
Authors: Gendron Paul J. , Nandram Balgobin
Published: October 2013

A model for correlated and heavy-tailed background noise in time series data is introduced. The approach is based on a multi-resolution time adaptive wavelet packet expansion that assigns to each resolution and band a measure of spikiness associated with independent t distributed variates. The model is adaptive similarly in time, scale, and correlation structure within the dyadic structure of the wavelet packet framework. Parameter estimation is accomplished by recursions in time at each frequency band/scale. The model is applied to both ground motion data and shallow water ocean acoustic background noise. A comparison with the Gaussian model suggest its favorable advantage. Estimators for transient signals based on the new model are derived and show usefulness in extracting transients with unknown or weakly specified characteristics. The usefulness of the model and the estimator is demonstrated via a comparison with the fixed transform DWT on quarry blast seisms. The results show that the method outperforms DWT based estimation in MSE by a factor of 2 at a moderate SNR for these classes of transients. [Work supported by ONR.]
Correlation vibroacoustic imaging of subsurface objects
Authors: Ekimov Alexander , Sedunov Nikolay , Tsionskiy Michael , Donskoy Dimitri
Published: October 2013

Any subsurface object whose mechanical impedance is different from the surrounding media manifests itself on the surface by contributing to the surface mechanical impedance. Since most of the surfaces (except plates and membranes) can be characterized by the local impedance, such a manifestation can be interpreted as an object image projected on the surface. This image projection can be captured by measuring surfaces local impedance at a grid of points or pixels. One of the problems in implementing this imaging approach is that object impedance contribution can vary substantially depending on the frequency, depth, and medium properties. Therefore, multiple impedance images must be obtained at the different frequencies and, consequently, an image selection or more sophisticated image processing should be implemented at the expense of additional time and processing resources. The developed correlation technique utilizes broadband signals and performs convolution of the broadcasted signal with a measured vibration signal at each pixel. The resulted image has a high contrast and takes a fraction of time and processing power to create as compared with the image/frequency selection approach. Examples of practical implementation of the developed method are presented and discussed.
Field site evaluation for seismic mine detection
Authors: Martin James S. , Larson Gregg D. , Rogers Peter H. , Scott Waymond R. , McCall George S.
Published: October 2013

A system has been developed that uses audio-frequency surface seismic waves for the detection and imaging of buried landmines. The system is based on the measurement of seismic displacements immediately above buried mines using noncontacting vibrometers that interrogate the surface motion with either radar or ultrasonic signals. In laboratory tests and limited field tests the system has demonstrated the ability to detect a variety of inert antipersonnel and antitank mines with background contrast in excess of 20 dB. Current work on the system is focused on the transition from the laboratory into the field. To facilitate this, a series of experiments has been undertaken to measure the characteristics of several field test sites. The tradeoff between image contrast and scanning speed is of primary concern in evaluating the features of these sites. The field experiments have investigated the nature of ambient seismic noise, input impedance at the seismic source (a ground contacting shaker), modal content of the seismic interrogation signal, and the nature of the nonlinearities in the soil. Observed nonlinear phenomena have included harmonic generation, phase speed slowing, dispersion and spall. Although interesting, the differences between the field sites and the laboratory model do not appear to pose problems for seismic mine detection.
Seismo-acoustic propagation in environments that depend strongly on both range and depth
Authors: Outing Donald A. , Siegmann William L. , Dorman LeRoy M. , Collins Michael D.
Published: October 2013

The parabolic equation method provides an excellent combination of accuracy and efficiency for range-dependent ocean acoustics and seismology problems. This approach is highly developed for problems in which the ocean bottom can be modeled as a fluid. For the elastic case, there remain some accuracy limitations for problems involving sloping interfaces. Progress on this problem has been made by combining a new formulation of the elastic parabolic equation that handles layering more effectively [W. Jerzak, ‘‘Parabolic Equations for Layered Elastic Media,’’ doctoral dissertation, Rensselaer Polytechnic Institute, Troy, NY (2001)] and a mapping approach that handles sloping interfaces accurately [J. Acoust. Soc. Am. 107, 1937–1942 (2000)]. This approach makes it possible to handle problems involving complex layering and steep slopes, but the rate of change of the slope must be small. The method and its application to data will be described. Our immediate goal is to model propagation of seismic surface waves propagating across a transition between dry and marshy terrain. We have suitable data applicable to vehicle-tracking problems from Marine Corps Base Camp, Pendleton, CA. [Work supported by ONR.]
Internal solitary waves and coupled perturbed modes
Authors: Higham Chris J. , Tindle Chris T.
Published: October 2013

Coupled perturbed mode theory combines conventional coupled modes and perturbation theory for fast range-dependent normal mode calculations. The method is applied to sound propagation through shallow water internal solitary waves, or solitons. The solitons considered are depressions of the thermocline, separating well-mixed upper and lower layers. Shallow water solitons lead to strong mode coupling. The theory gives physical insight into soliton coupling physics through explicit mode coupling formulas.
Acoustic simulations with a ray-tracing program: Reporting an experience
Authors: Granado Milton V.
Published: October 2013

The possibility of exporting to ray-tracing type programs the geometry generated by Auto-Cad, is very appealing for the architect who wishes to simulate the acoustic behavior of a room. It was found that a good knowledge of room acoustic is necessary for the selection of the program parameters and the objective acoustical measures outputted by the program for the assessment of the required acoustical quality. There is scarce information on the absorption coefficients of lining materials, but it is on the choice of the diffusion coefficients where lie the greatest uncertainties. Because of the considerable impact that these data have on the computational results, the user may feel insecure about the results of his efforts. Therefore it is advisable that trained personnel participate in the efficient use of this computational tool. It was found however that one form of the output of the program, that in which the acoustical parameters are color mapped, have qualitatively corroborated speech intelligibility results objectively measured in the field. (To be presented in Portuguese.)
Aperture size, materiality of the secondary room, and listener location: Impact on the simulated impulse response of a coupled-volume concert hall
Authors: Ermann Michael , Johnson Marty E. , Harrison Byron W.
Published: October 2013

By adding a second room to a concert hall, and designing doors to control the sonic transparency between the two rooms, designers can create a new, coupled acoustic. Concert halls use coupling to achieve a variable, longer, and distinct reverberant quality for their musicians and listeners. For this study, a coupled-volume concert hall based on an existing performing arts center is conceived and computer modeled. It has a fixed geometric volume, form, and primary-room sound absorption. Ray-tracing software simulates impulse responses, varying both aperture size and secondary-room sound-absorption level, across a grid of receiver (listener) locations. The results are compared with statistical analysis that suggests a highly sensitive relationship between the double-sloped condition and the architecture of the space. This line of study aims to quantitatively and spatially correlate the double-sloped condition with (1) aperture size exposing the chamber, (2) sound absorptance in the coupled volume, and (3) listener location.
Automated two-dimensional passive tracking of free-ranging dolphins using two towed arrays and frequency-domain beamforming
Authors: Thode Aaron , Howarth Eric S. , Martinez Anthony , Stamates Jack
Published: October 2013

Dolphin whistles form time-frequency contours that are complex, overlapping, and unpredictable. These features make automatic detection and localization of whistles difficult and labor-intensive whenever standard cross-correlation methods are used. A technique is presented for automatically extracting ranges and bearings of multiple free-ranging dolphins by post-processing acoustic data from two towed arrays. Each array had two elements spaced 2 m apart, and the distance between towed arrays was 350 m. The data are processed in the frequency domain, a natural framework for automation that also permits individual bearings to be extracted from whistles that overlap in the time domain. The frequency contours of the whistles are also automatically obtained as a byproduct of the analysis. Data from a February 2002 survey cruise off the Atlantic seaboard are used to illustrate the process. [Work supported by SE Fisheries, National Marine Fisheries Service.]
Marine Mammal Resource
Authors: Felgate Nick
Published: October 2013

In the sonar world there is still a heavy reliance on the human ear for detection. To detect threats, the sonar operator must be familiar, not only with their acoustic signatures but also with the many and varied noises emanating from other sources in the ocean. These include noises of biological origin, particularly marine mammals. The Marine Mammal Resource is a hypertext document aimed at providing a reference set of sounds for training purposes. It contains textual descriptions on 18 different aspects of ecology for each of the species, summarizing the information available from the open literature. Subjects include vocalizations, habitat, distribution, hearing, and physical characteristics. The resource also contains images, diagrams, and movies for identification purposes. Data has been collated for over 40 species primarily found in the Atlantic Ocean. Information has been collated through a number of research organizations in America and Europe. The resource has application to the reduction of cetacean by-catch in trials, both in providing information in the derivation of environmental impact assessments pretrial and in the acoustic monitoring of the area during the course of a trial.
Shear wave velocity measurements in high porosity marine sediment models using radiation impedance method
Authors: Kimura Masao
Published: October 2013

Acoustic measurements of surficial high porosity marine sediment are important to investigate the coastal environments. To do this, the measurement of shear wave velocity rather than longitudinal wave velocity is useful for determining the physical properties of surficial high porosity marine sediment. However, the direct measurement of shear wave velocity in high porosity marine sediment is very difficult, because the attenuation of the shear wave in high porosity marine sediment is quite large. In this study, shear wave velocities in four kinds of high porosity marine sediment models are measured using the radiation impedance method which has been proposed. From the measured results, it is seen that the shear wave velocity of below 1 m/s can be measured, and the shear wave velocity increases, as the porosity decreases. The relationship between the shear wave velocity and the porosity are different depending on the kind of marine sediment model.
Study of elastic nonlinearity of soft solids with transient elastography: Landau coefficients and finite amplitude shear wave
Authors: Catheline Stefan , Gennisson Jean-Luc , Chaffa Sana , Fink Mathias
Published: October 2013

Transient elastography allows one to accurately achieve the Youngs modulus of soft tissues from the measurement of the shear-wave velocity. The Youngs modulus is a second-order elastic moduli and describes the linear behavior of a medium. In order to achieve the third-order elastic moduli in soft tissues (which characterize the nonlinearity), we have used transient elastography in an acoustoelasticity-like experiment. It consists in measuring shear-wave velocities in a uniaxial pre-stressed medium. This technique uses an ultrafast scanner and allows one to measure thenonlinear third-order elastic Landau coefficients A, B, C in an Agar-gelatin based phantom. The several orders of magnitude found between these three constants appear to be a characteristic of soft tissues. In a second part, we present the first experimental displacements of a finite amplitude transverse wave. The results are compared to a simulation based on the modified Burgers equation. In both approaches, it appears that contrary to longitudinal wave for which even harmonics are created during the propagation, only odd harmonics are present on the displacement spectra of a finite amplitude transverse wave.
Coherent nonlinear scattering mechanisms for ultrasound-stimulated vibro-acoustic spectrography
Authors: Makris Nicholas C. , Ratilal Purnima , Thierman Jonathan
Published: October 2013

Physical mechanisms by which responses at the difference frequency can arise from targets insonified by sources radiating at two distinct primary frequencies, as found in ultrasound-stimulated vibro-acoustic spectrography, Fatemi and Greenleaf [Science 280 (1998)], are described from first principles using coherent field theory. Three specific mechanisms are investigated. These are (1) nonlinear interactions at the difference frequency in the primary fields co-linearly scattered from the object, (2) linear scattering by the object of nonlinear evanescent waves incident on the object at the difference frequency due to interference of noncolinear primary incident waves, (3) the linear scattering of propagating nonlinear waves incident on the object from co-linear primary waves. The relative amplitude of waves from these various mechanisms will be investigated and shown to vary with the target’s size, shape, acoustic properties as well as the measurement geometry.
Methods of experimental investigation of acoustic interaction between electroacoustical transducers in array
Authors: Aronov Boris , Oishi Tetsuro , Brown David A.
Published: October 2013

Determination of acoustic loading conditions on projectors in underwater arrays is needed to predict the performance of the array. Nonuniform distribution of the acoustic loading over the radiating surface of the array is generated due to acoustic interactions between the projectors, and often causes performance degradation of the directivity patterns and the transmit frequency response. In the electromechanical equivalent circuit model of such an array, the influence of the neighboring transducers can be considered as the mutual radiation impedance that is inserted in series with the self-radiation impedance. The mutual radiation impedance depends on the configuration of the transducer, the mode of vibration, velocity distribution, and the geometry of the array. We present experimental techniques to determine the mutual radiation impedance as an intrinsic property of a given transducer and array configuration. Two experimental methods are presented: the Z method and the V method. The methods are based on the measurements of the input impedances and on the output voltages of the interacting transducers. For the two methods, analytical investigations based on the electromechanical equivalent circuit analysis will be presented along with supporting experimental results on cylindrical transducers. [Work supported in part by ONR 321SS Lindberg and BTECH Acoustics.]
Development of a dynamic Young’s modulus measurement system for compliant polymers
Authors: Guillot Francois M. , Trivett David H.
Published: October 2013

A new system to experimentally determine the complex Young’s modulus of elastomers at elevated hydrostatic pressures and as a function of temperature is presented. A sample cut in the shape of a rod is glued to a piezoelectric ceramic shaker and mounted vertically inside a pressure vessel equipped with glass windows. Two independent measurement methods are then used: a resonant technique, to obtain low frequency data, and a wave propagation technique, to obtain higher frequency data. Both techniques are implemented utilizing laser Doppler vibrometers; one vibrometer detects sample resonances through a window located at the bottom of the pressure vessel, and a set of two separate vibrometers monitors the speed of longitudinal waves propagating in the sample (by measuring symmetric lateral displacements), through windows located on the sides of the vessel. The apparatus is contained inside an environmental chamber for temperature control. Using this approach, Young’s modulus data can be obtained at frequencies ranging typically from 100 Hz to 5 kHz, under hydrostatic pressures ranging from 0 to 2.07 MPa (300 psi), and at temperatures comprised between −2 °C and 50 °C. Experimental results obtained on commercial elastomers will be presented. [Work supported by ONR.]
Elements for a conformity assessment system in acoustics, vibrations and ultrasound in Mexico
Authors: Echeverria-Villagomez Salvador , Elias-Juarez Alfredo
Published: October 2013

Conformity assessment in acoustics, vibrations, and ultrasound have great relevance for human health, safety, and environmental protection. Due to this fact, it is usually the government and public agencies that promote, together with the National Standards Institute (NSI) and representatives from the whole society, the development and continuous updating of standards and regulations. Besides appropriate regulations, conformity evaluation requires the existence and fitness of, at least, two other elements: adequate measuring capabilities and a proper system of consequences. The measuring capabilities are embodied in the infrastructure that goes from the National Metrology Institute (NMI) to the calibration and testing laboratories and verification units. The system of consequences, the means by which compliance with regulations can be verified and required, can be established by the same government and public agencies (GPA) of the field of work in which the regulation has been developed. In Mexico, a conformity assessment system of this kind has been evolving rapidly during the past 10 years, since the establishment of CENAM. The paper will present a proposed conformity assessment system, arising from a comparison of the Mexican system with those of other countries.
For purposes of environmental noise assessment, A-weighting needs to be retired
Authors: Schomer Paul D.
Published: October 2013

Currently, most countries use some form of A-weighted equivalent level (ALEQ) to assess the annoyance of most noises. But A-weighting fail to properly assess multiple noise sources such as planes, trains, and automobiles relative to one another, and it fails to properly assess sound with strong low-frequency content. It performs better outdoors than indoors even though the receivers are indoors. It certainly cannot be used for room noise criteria. A-weighted LEQ cannot assess the audibility of sound, and, in fact, LEQ in fractional octave bands cannot be used to assess the audibility of sounds at low frequencies. A-weighting needs to be retired. There are better measures for all of these functions such as loudness-level weighting using ISO 226. At low frequencies, data show some people (about one-third) are ‘‘C-weighted’’ listeners. For all noise, it may be that one model just does not fit all. Experiments show that a majority of listeners make categorical judgments and merely count events based on level with the minority of subjects fitting three other models. There are many ways to clearly move forward but we must give up our A-weighting, it has now reached old age.
Acoustical sensory profiles: The bridge between measurements and preference
Authors: Lyon Richard H.
Published: October 2013

Our judgments about all kinds of sounds depend on the sound itself and also on our experience, situational context, and expectation. The response is multimodal in that vibration, colors, temperature, and other environmental factors have an influence on our reactions. In the limited area of product sounds there has been an effort to relate consumer judgments to measurements through the use of descriptive words to create an ‘‘Acoustical Sensory Profile’’ or ASP, particularly for products that have sound as a primary feature. Examples include musical instruments, audio products, and concert halls. More recently, other products for which sound is an ancillary feature have been evaluated using ASPs. This presentation discusses this background and projects the use of ASPs, and their relationship to physical measurements and consumer judgments in particular.
Refractive acoustic devices for airborne sound
Authors: Sánchez-Dehesa J. , Caballero D. , Cervera F. , Sanchis L. , Sánchez-Perez J. V. , Martinez-Sala R. , Rubio C. C. , Meseguer F. , Lopez C.
Published: October 2013

It is shown that a system made of periodic distributions of rigid cylinders in air acts as a new material which allows the construction of refractive acoustic devices for airborne sound. This kind of crystal, named sonic crystal, has low impedance and transmits the sound at subsonic velocities. Here, the fabrication and characterization of a convergent lens is presented. Also, the acoustic analog of the Fabry–Perot interferometer based on this crystal is analyzed. It has been concluded that refractive devices based on sonic crystals behave in a manner similar to that of optical systems. [Work supported by CICyT of Spain.]
Influence of a focusing lens on the electroacoustic response of ultrasonic transducers
Authors: Pierre Marechal , Franck Levassort , Louis-Pascal Tran-Huu-Hue , Marc Lethiecq
Published: October 2013

Focusing lenses are currently used in most ultrasonic transducers for medical and immersion NDT applications. In particular, high frequency medical single element transducers for applications such as skin and eye imaging require focusing lenses to obtain high resolutions. The effect of a lens on the radiation pattern has been widely studied through impulse diffraction theory, but its influence on the electrical impedance and electroacoustical response is not possible using classical models which are based on single-mode and plane wave hypothesis. Here, the effect of a lens is investigated as a function of its radius of curvature, minimum thickness, wave velocity, and acoustic impedance. The method combines a finite element code (ATILA software), which allows us to calculate the displacements near the lens surface, with a radially symmetrical impulse diffraction calculation based on the Hankel tranform to obtain the transducer response at all locations in the propagation media. This allows to observe simultaneously electrical, electroacoustical and radiation properties of the device. Finally, a multidimensional unconstrained nonlinear minimization method is used to identify the geometrical and acoustical properties of the elements which will provide the highest overall transducer performance. [Work supported by the EU PIRAMID project.]
Real time focusing using an ultrasonic ‘‘one channel time-reversal mirror’’ coupled to a solid structure
Authors: Quieffin Nicolas , Ing Ros Kiri , Catheline Stephan , Fink Mathias
Published: October 2013

Focusing and beam steering is achieved using a time-reversal process and a unique transducer coupled to a solid structure. This low cost technique allows one to focus acoustic energy anywhere on a 3-D domain with a spatiotemporal resolution comparable to multiple transducer’s array. We first record the signal emitted by the transducer and detected by a hydrophone needle at a reference point. The signal received is then time-reversed and remitted using the same transducer. At the reference point one can observes a spatiotemporal recompression. Moreover, it is shown how the experimental Green’s functions at the surface of the cavity can be used to control the emitting ultrasonic field. A careful study of this phenomena leads us to better understand the resolution and the signal to noise ratio of the focusing system. Indeed the side-lobe level as well as the focal width are no more dependent on the transducer aperture but on the dimensions of the solid structure and the multiple paths covered by the acoustic waves in the solid. Those results are supported both by experiments and numerical modeling.
Harmonic generation of Lamb waves
Authors: Ing Ros Kiri
Published: October 2013

Lamb waves are dispersive waves that propagate following a number of distinct modes that depend on the values of the central frequency and frequency band. According to such properties and using the time-reversal process, it is shown that the hyperfocusing effect may be experienced [R. K. Ing and M. Fink, IEEE Trans. Ultrason. Ferroelectr. Freq. Control 45, 1032–1043 (1998)]. Such a focusing effect both relates the time recompression of the dispersive Lamb waves and constructive interference on the focus point of the modes involved. The hyperfocusing effect is interesting because it allows the amplitude of the Lamb waves to reach huge values on the focus point. In our experiments, Lamb waves with normal amplitudes of micrometer values have been achieved on the free surface of a Duralumin plate of 3 mm thickness. By analyzing the Lamb waves in the neighborhood of the focus point using the 2-D Fourier transform technique, a nonlinear process of harmonic generation is then observed—the fundamental frequency component is centered at 1.5 MHz. This nonlinear process is under study and quantified.
Bistatic scattering from the edge of a wedge with an impedance coating
Authors: Hughes R. , Niemiec J. , Stoyanov Y. J. , Überall Herbert
Published: October 2013

We calculate the amplitude of acoustic monostatic and bistatic scattering from a solid wedge, thereby extending some previous work of ours that assumes a line source parallel to the edge of the wedge. The surface of the wedge is treated as an impedance surface, and the expression for the impedance corresponding to an absorbing, multilayered coating which had also been obtained by us previously is utilized here for calculating the scattering amplitude from the wedge coated with such an impedance material. Results are obtained as a function of frequency for various incident and bistatic angles. Calculations show in general a highly detailed interference structure except for the case of monostatic backscattering from an impenetrable wedge.
Measures of variability in child and adult speech: Test–retest results
Authors: Koenig Laura L. , Lucero Jorge C.
Published: October 2013

Elevated measures of speech production variability are commonly observed in children and in clinical populations. Methods of assessing variability thus have utility in understanding processes of speech development and breakdown. Valid interpretation of variability measures for a given speaker requires understanding the stability of such measures over time. Here, we present test–retest data on aerodynamic measures of consonants in two 5-year-old children and two women, each recorded two times approximately 3.5 months apart. Two methods of assessing variability, the spatio-temporal index (STI) and Functional Data Analysis (FDA), were applied to the data. STI yields a single value over repeated productions, incorporating both spatial and temporal aspects of the data. FDA yields separate measures of warping (phasing) and amplitude. Both FDA and STI analyses yielded higher values in children than adults at both times, as expected. The test–retest analysis indicated that both STI and FDA values were significantly correlated over time, suggesting that either method provides a reliable measure of speech production variability. The r values for STI were higher than for FDA, whereas FDA values showed more differentiation across consonants. Our discussion focuses on the relative merits of these two approaches for assessing speech variability.
Investigation of labio–lingual coordination in the production of formant frequencies for /u/: Normal speakers and speakers with dysarthria
Authors: Weismer Gary , Yunusova Yana , Berry Jeff
Published: October 2013

Articulatory behavior for the vowel /u/ is interesting because motions of the lips and tongue dorsum can both produce the effect of a relatively low second formant frequency (F2). Previous studies have suggested that speakers may trade off labial and lingual contributions to this low F2, using less labial contribution when the tongue is making a strong contribution, and vice versa. Moreover, if the lips are experimentally con- strained, the tongue will make up the difference and produce an acoustic output relatively close to the desired value. What is not clear is how the motions of the lips and tongue are coordinated across the vocalic nucleus to produce the F-pattern typically associated with /u/. Are the two gestures synchronized? Is there a predictable articulatory organization, one that is fairly consistent across a large group of speakers? We present x-ray microbeam and acoustic data for four groups of speakers (two groups of neurologically normal speakers, and two groups with dysarthria associated with Parkinson’s disease and amyotrophic lateral sclerosis) suggesting that the answer to both questions is a qualified yes. Somewhat surprisingly, articulatory coordination in dysarthric speakers does not appear to be qualitatively different from that in normal speakers. [Work supported by NIH.]
Efficacy of proprioception in achieving vowel targets when acoustic feedback is blocked: An EMMA study of production under contrasting noise conditions
Authors: Tiede Mark K. , Matthies Melanie , Perkell Joseph , Zandipour Majid , Stockmann Ellen
Published: October 2013

In a magnetometer study of six normal hearing native English speakers producing vowels in an /hVd/ context, masking noise was used to interfere with acoustic self-monitoring of speech production. Data were obtained under two conditions. In the first, subjects received unmodified audio through earphones. In the second condition audio feedback was replaced by white noise at 95 dB SPL. Under both conditions subjects were instructed to use a real time SPL display for regulating loudness to avoid Lombard effects. Midsagittal transducer data, corrected for head movement, were obtained for the lower incisors, lips, and three points on the tongue. A consistent measurement point was obtained by first delimiting each vowel using RMS thresholding of the acoustics, then selecting the 1/3 offset between those limits. Results showed, contrary to expectation, that neither formants nor the measured articulator locations under the noise condition were more dispersed than when acoustic feedback was available; for some subjects they were in fact less variable. The observed tighter grouping under the noise condition will be discussed in the context of increased stiffness of the production system in response to loss of normal acoustic monitoring. [Work supported by NIH.]
Geometrical analysis of the tongue muscles based on MRI and functional modeling of the tongue
Authors: Takano Sayoko , Honda Kiyoshi , Jianwu Dang
Published: October 2013

The geometry of the tongue muscles during production of Japanese five vowels was analyzed using MRI toward a realistic design of our physiological articulatory model [Dang et al., Acoust. Sci. Technol. 22, 415–425 (2001)]. Articulatory changes in shape of the muscle bundles and of the lingual arteries indicated two findings. (1) The styloglossus (SG) was previously thought to cause high-back tongue position by pulling its insertion point in the tongue. However, the MRI-based geometry of the extra-lingual part of SG was found to be almost constant across vowels. This implies that SG may contribute to tongue deformation mainly by the contraction of its intra-lingual part. (2) The right and left arterial landmarks within the tongue tissue indicated tissue deformation across vowels in the lateral direction. The distance between the landmarks was larger in front vowels, and smaller in back vowels. That is, front vowels are associated with lateral expansion, and back vowels are accompanied by medial compression. With the above results, the physiological model of the tongue was revised to have more layers so that the natural geometry of the muscles could be implemented.
Improvements of a physiological articulatory model in construction and control strategy
Authors: Dang Jianwu , Honda Kiyoshi
Published: October 2013

A physiological articulatory model that represents midsagittal regions of the speech organs has been used to simulate articulatory movements during speech. A fast simulation method was realized by modeling both soft tissues and rigid organs by mass-points and springs. It is, however, difficult to exactly represent characteristics of a continuous body using the network consisting of mass-points and volume-less springs. To model soft tissues accurately, the springs are replaced by viscoelastic pillars with both length and thickness, and the masses are distributed over the pillars. Each eight-vertex mesh of the soft tissue is filled with 28 pillars that connect the vertices one to another on the edges and surfaces, and inside diagonally. The initial thickness of the pillars for each mesh is calculated by making the total volume of the pillars equal to the mesh volume. During tongue deformation, pillars change in the length and thickness according to the physical laws in continuous bodies. The articulator model is driven by muscle contraction parameters. Muscle activation signals are generated based on a target-reaching task, and fed to drive the model to approach the targets. This study further accounts for the agonist–antagonist mechanism of the muscles in the control strategy according to EMG analysis. [Work supported in part by TAO, Japan.]