bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced spatial resolution of dual-mode ultrasound arrays using coded excitation
Authors: Wan Yayun , Ebbini Emad
Published: October 2013

A prototype 64-element 1-MHz concave (ROC=100 mm) DMUA has been shown to produce conventional synthetic aperture (SA) images in a field of view extending by 6 cm axially and 4 cm laterally (around its geometric center). With an f♯=0.8 and a fractional bandwidth ≊40%, the lateral and axial resolutions of this prototype were 1.1 mm and 2.6 mm, respectively. We have investigated the use of coded excitation and pseudoinverse filtering for enhancing the axial resolution of the DMUA. SA images were formed from a 12 μs linear chirp transmit pulse covering the frequency band of 0.5–1.5 MHz. The beamformed data was compressed using matched and regularized pseudoinverse filtering with a colored noise model. Image data were collected from a 3 D quality assurance phantom with an egg-shaped contrast target using the DMUA. The contrast ratio (CR) was 3.35, 7.8, and 6.6 for conventional pulse-echo, matched filter compression and inverse filter compression, respectively. In addition, axial and lateral speckle cell size parameters were calculated for the three methods. The axial resolution was 2.6, 2.5, and 1.65 for conventional pulse-echo, matched filter and pseudoinverse filter, respectively. Thus one can see that approximately 33% improvement in resolution was achieved without significant loss in CR or change in lateral resolution.
Spread spectrum sequence design for the study of outdoor noise propagation
Authors: Angus Jamie A. , Waddington David C.
Published: October 2013

The design of carrier-modulated code sequence signals that can be used for the study of outdoor propagation, are presented. In particular, the construction of these signals such that they are robust to the time-variance of the outdoor acoustic path is discussed. The design of these signals so that they can also occupy known bandwidths is also described. The result is an audible frequency signal that is biphase-modulated by two pseudorandom code sequences in a way that is specially designed for simultaneous fine time resolution and large range ambiguity. A particular advantage of this signal is that an estimate of the time-varying Doppler can be derived by recovering the suppressed carrier from the received signal, and various means of extracting the Doppler are explained. Extensions of these signals to allow multiple simultaneous measurements are also described. [Work supported by EPSRC UK]
Remote acoustical reconstruction of cave and pipe geometries
Authors: Schultz Todd , Bowen David , Unger Gladys , Lyon Richard H.
Published: October 2013

Military and commercial interests desire to determine the geometry of caves, tunnels, and piping systems remotely. Advance knowledge of the geometry would allow military personnel to focus on the mission objectives rather than on cave exploration and mapping. Commercial applications of remote geometry mapping include determining locations of collapsed mines and tunnels for search and rescue missions, and determining locations of breaches or constrictions in pipelines. This research effort begins to extend acoustic pulse reflectometry to these applications and only requires simple measurements made at the waveguide entrance. This implementation first measures the acoustic reflection coefficient using a modified form of the two-microphone method and computes the waveguide impulse response. Then the system uses an inverse-scattering algorithm to solve for the cross-sectional area as a function of distance. Results are shown for a simple area expansion attached to a laboratory impedance tube with a diameter of 35 mm, and for a pedestrian tunnel with a nominal square cross-section of 5.9 m2. The impedance tube estimates match the known cross-sectional areas to within 10%. The results from the pedestrian tunnel show greater uncertainty due to frequency range limitations on the measurements, but can still capture important features of the geometry.
Acoustic and elastic radiative transfer theory in seismology
Authors: Przybilla Jens , Korn Michael , Wegler Ulrich
Published: October 2013

Inversion results that were obtained by applying the acoustic and elastic radiative transfer theory to seismological data will presented. Scattering of seismic wave fields within the earth is documented by the pulse broadening of direct wave trains and the appearance of coda waves following the direct waves. The pulse broadening is caused by forward-scattered waves and the coda by wide-angle scattering. Random media are used as models for the heterogeneities of the earth. The energy transfer equations are solved with Monte Carlo methods. The results obtained with the acoustic and elastic theory for the transport scattering coefficients and absorption coefficients are compared with each other. It shows that scattering is the main process for lower frequencies. For higher frequencies intrinsic absorption is dominant. The results for elastic and acoustic radiative transfer are the same if strong forward scattering is assumed. For lower values of anisotropy the results are different.
An investigation into the relationship between sound intensity and normal surface velocity
Authors: Boyle Mark , Cassidy Matthew , Cooper Richard , Gault Richard , Wang Jian
Published: October 2013

The analysis of sound characteristics using boundary element methods (BEM) requires accurate sound source data of normal surface velocity or pressure as boundary conditions. However, direct measurements of normal surface velocity are not easily acquired while sound intensity measurements are relatively easy to obtain. In this study the relationship between near field sound intensity and normal surface velocity is investigated. The study first considers correlated and uncorrelated sound sources in the frequency range of 63 to 1000 Hz. A matrix of sound intensity measurements on well-distributed points in the near field of the sound source is collected. A model of the relationship between sound intensity and volume velocity is developed and used to compute the normal surface velocity of the sound source from sound intensity measurements. The normal surface velocities are then used as the boundary conditions for a BEM model of the sound source that predicts the sound intensity at the original measurement points. The measured and predicted values are compared in order to validate the model. The differences of predicted and measured sound intensities that are within ±3 dB are considered sufficiently accurate.
Design and implementation of a three-dimensional seven microphone acoustic intensity probe for measuring sound properties from various sources
Authors: Miah Khalid , Hixson Elmer
Published: October 2013

Based on existing theoretical models of multi-dimensional cross-spectral methods for calculating sound pressure and particle velocities, this report has derived and/or extended models of intensity, energy densities, and specific acoustic impedance for seven microphone configurations. Array configuration, spacing, and overall implementation procedure is also outlined in this report. Experimental data has confirmed the validity of the analytical solution for different sound sources in both anechoic and reverberation room environment. Sound sources of different frequency bands [broadband (100 Hz–7 KHz), low (100 Hz–1 KHz), and high (1–7 KHz)] was used separately to compare accuracy and performance of the acoustic probe. Signal processing techniques and software implementation with potential errors and limitations of the system are explained. These would provide a framework for further refinement of instrumentation aspects of the acoustic probe. Potential applications and users of the probe are also described in this report.
Collocated proportional-integral-derivative (PID) control of acoustic musical instruments
Authors: Berdahl Edgar , Smith Julius
Published: October 2013

The dynamic behavior of an acoustic musical instrument can be drastically modified by closing a feedback loop around a single sensor and actuator. Proportional-Integral-Derivative (PID) control provides for a simple yet effective paradigm, whose analysis is simplest for collocated systems. The analysis is further simplified when the musical instrument is modeled by a single, lightly damped mass-spring-damper system. This example is presented as a pedagogical laboratory exercise (http://ccrma.stanford.edu/realsimple/pidcontrol) within the framework of the RealSimPLE project (http://ccrma.stanford.edu/realsimple). Students learn what physical models are, why they are useful, what the basic ideas behind feedback control are, and how they may be applied to a plucked string. A plucked string model is implemented with a digital waveguide in the Pure Data environment. Given the waveguide model and the theoretical results from the simplified mass-spring-damper model, students are asked to find PID coefficients that result in particular controlled instrument behaviors (increase in damping, decrease in pitch, etc.). At the close of the talk, a few more advanced topics are covered. In particular, a proof is presented explaining why damping with collocated velocity feedback is stable no matter how large the feedback loop gain is. [Work supported by the Wallenberg Global Learning Network.]
Combining physical REALity with SIMulations in pedagogical laboratory experiments
Authors: Berdahl Edgar , Lee Nelson , Cassidy Ryan , Smith Julius
Published: October 2013

The RealSimPLE project provides teachers with a modular collection of online musical acoustics laboratory experiments, including experiments on elementary wave motion, vibrating strings, pipes, sensors, digital waveguides, psychoacoustics, PID control, sound cards, and more. Hands-on laboratory sessions are complemented by pedagogical computer-based simulations or animations of the same systems. This dichotomous approach illustrates both the behavior of the real system together with corresponding idealized theoretical simulation. Moreover, the simulations can illustrate hard-to-measure details of the real system, or highlight details which easily escape the eye or ear. In this way, the traditional lab bench is enhanced rather than replaced. Detailed instructions help teachers and/or students easily construct the minimal amount of low-cost laboratory equipment needed. The RealSimPLE website (http://ccrma.stanford.edu/realsimple) also includes rollover ‘‘pop-up’’ definitions for many technical terms. These definitions (within HTML pop-up overlays) include links to more-detailed definitions and examples, allowing website visitors to easily dig deeper down through the tree of prerequisite terms, thereby filling in any knowledge-gaps they may have. A motivated student anywhere in the world with a basic math and physics background can obtain advanced graduate-level knowledge from the website in a self-paced, demand-driven manner. [This work was supported by the Wallenberg Global Learning Network.]
Turbulence: Geometrical and statistical aspects
Authors: Friedrich R.
Published: October 2013

Turbulent flows are characterized by the transport of energy across scales. This energy transport, which frequently is denoted as energy cascade, is related to the formation of hierarchically organized spatio-temporal structures. A statistical treatment of velocity increments of turbulent ows thereby shows that the statistics are strongly intermittent exhibiting large deviations from Gaussian statistics. In this talk we shall give an overview on recent results concerning the analysis of Eulerian as well as Lagrangian velocity statistics, which allows one to characterize, understand, and model the small scale statistics of turbulent flows by means of stochastic processes. Furthermore, we review attempts to relate the statistical properties of small scale turbulent flows to the geometry of vortical structures in the flow field.
Flutelike instruments: A perfect joint between acoustics and hydrodynamics
Authors: Fabre Benoit
Published: October 2013

The oscillation in flutelike instruments results from the aeroacoustic coupling of an hydrodynamic mode of a jet with an acoustic mode of a resonator. Since musical instruments are empirically optimized oscillators, the modeling of flutes appears as a test bench for different approaches. Complementary descriptions have been developed in the literature from the point of view of acoustics or from the point of view of hydrodynamics. Unfortunately, the basic hypothesis in both fields are not easily compatible: for instance, as a first approximation, pipe acoustics can be studied neglecting the influence of mean flow, while the jet instability can be studied neglecting the influence of compressibility. In the presentation, we will develop an aero-acoustic approach to the oscillation in flutelike instruments, that focuses on the different approximations that need to be carried. We will emphasize on the limited range of control parameters that the current models may describe. The different elements will be discussed as well as the traditional custom to study the system as a lumped model.
Synchronization of organ pipes as a paradigm for nonlinear acoustical oscillations
Authors: Abel Markus , Bergweiler Steffen
Published: October 2013

From measurements on organ pipes, it has been known for a long time that the so-called Mitnahme Effekt can lead to a mutual influence of organ pipes by each other. The same holds for external driving of pipes by acoustical sources of well-defined frequencies. A locking of two differently tuned pipes to a single frequency, or to the frequency of the external driving, respectively, is observed. We measure the dependence on the coupling by varying the distance of the pipes. In great detail, we measure the dependence on the signal strength in the case of the external driving. As a result, we find a so-called Arnold tongue over a range of 50 dB, i.e., for extremely weak driving, one still finds synchronization to a common frequency. We apply the very general theory of synchronization from the point of view of nonlinear vibrations and apply it to the experimental data from organ-pipe measurements. Surprisingly, it is possible to capture the main features of the phenomenon by nonlinear oscillator equations, coupled to each other. A full explanation includes a good understanding of the aeroacoustics producing the sound of an organ pipe.
Grand Canyon: Restoration of natural quiet (current status)
Authors: Hingson Dickson J.
Published: October 2013

Mandated restoration efforts to reduce extensive aviation noise intrusions into the wild soundscape of Grand Canyon National Park will be reviewed, in context of underlying, protracted political controversy. This is timely, for the approaching, presidentially directed due date is 22 April 2008, under the National Parks Overflights Act of 1987, for the ‘‘substantial restoration’’ of ‘‘natural quiet,’’ pursuant to noise standards/specifications of the National Park Service, with due consideration to the FAA for ensuring safety of aircraft operations. The draft EIS and ‘‘Preferred Alternative’’ (release due spring 2007) will therefore vigorously resurface scientific review of primary and supplemental noise indicators and standards appropriate to national parks. Grand Canyon, having large wilderness/backcountry areas and renown, is a particularly iconic focus for scrutiny. The restoration will be viewed against actualities of (1) the large number/types of aircraft operations at all altitudes above the park; (2) demanding management objectives and large size of Grand Canyon; and (3) its extremely quiet natural soundscape (which characterizes most desert and Colorado Plateau national parks.) Visitor experience values, including ‘‘wilderness character’’ and sound as resource are offered as ultimate concerns, often clashing with industrial tourism and its associated values of aerial perspective, speed/convenience, and economic return for tour operators.
Anthropogenic contribution to the acoustic environment of Mexican spotted owls in the Gila National Forest, New Mexico
Authors: Bowles Ann E. , Denes Samuel L. , Hobbs Chris , Plotkin Kenneth L. , Pruitt Elizabeth
Published: October 2013

We monitored the acoustic environment of Mexican Spotted Owls using an array of Larson-Davis (LD) sound level meters (SLMs) from 2000 to 2005. Thirty-nine LD-820 and LD-824 SLMs were deployed in a distributed array across a 20 km×24 km area, collecting two-second time interval data as continuously as possible mid-April to July. Although the study was designed to monitor low-flying military jets, SLMs collected over 350,000 hr of usable environmental noise data. The data were summarized by time, average level, and on an energy basis. The most important identifiable sources differed depending on metric. On a time basis, the ambient was the greatest contributor, followed by biotic sources and thunder. Regional jets were unexpectedly important, accounting for 2% of the total, far more than military jets. However, military jets and thunder accounted for most of the exposure to high amplitude noise (proportion of 2-s samples with LAeq \? 60 dBA). In terms of cumulative sound exposure, thunder was the greatest contributor, followed by ambient noise and military jets. The sources most likely to impact owls will depend on the critical features of noise from their perspective; identifying these features is the focus of future analysis [Work supported by U.S. Air Force ACC/CEVP]
Review, comparison, and evaluation of various environmental noise regulations in the United States
Authors: Szymanski Jeff D. , Ferren W. Brent
Published: October 2013

Environmental noise in the United States is often regulated at the city, county, and/or state level. A review of some representative urban, suburban, and rural regulations that provide objective noise limits was conducted. The sound level metrics, if specified, were reviewed for applicability to various noise sources. Ambient sound level data recorded over the last 10–15 years in urban, suburban, and rural areas of the United States were compared to the applicable limits, as well as to other criteria. Comparisons were evaluated for consistency and ambient sound levels were compared to USEPA guidelines in order to evaluate their relevance more than 30 years later. The regulations and guidelines reviewed were found to have varying degrees of applicability.
Estimating the number of uncorrelated disturbance sources in structural systems
Authors: Moon Suk-Min , Fowler Leslie , Clark Robert
Published: October 2013

The number of input signals used as reference inputs for feedforward control applications is limited due to cost, computational burden, input processing capability, and installation constraints. Identifying an optimal subset of reference sensors from a larger set capable of conveying the dynamics important in the performance path can result in greater performance with reduced complexity and order in the active control system. However, before determining an appropriate subset of sensors, the number of exogenous disturbance sources must be determined. Principal component analysis can be used to determine the number of uncorrelated disturbances acting on a structural system. Singular value decomposition of a covariance matrix of measured sensor signals is used to determine the number of independent disturbances present in the dynamic system. Limitations imposed by sample data length, path dynamics, and noise can limit the ability to resolve the number of exogenous disturbance sources. To estimate the number of secondary disturbance sources, a controller can be used to minimize the response due to the dominant signal source. It is then possible to identify the significant secondary sources. This can lead to improved estimation of the minimum number of reference sensors required for feedforward control in structural and structural acoustic systems.
Singular value decomposition of plant matrix in active noise and vibration—some examples
Authors: Berry Alain , Pasco Yann , Gauthier Philippe-Aubert
Published: October 2013

In active noise and vibration control problems that involve many secondary sources and error sensors, the active control performance is largely related to the conditioning of the plant matrix (formed by the transfer functions between individual secondary sources and error sensors). The principal component transformation (or singular value decomposition) of the plant matrix is an interesting tool to extract dominant secondary paths and limit control efforts. Furthermore, it can be used in a feedforward LMS controller to prevent slow convergence due to ill-conditioning of the plant matrix, and adjust the convergence rate of individual system modes. This approach is discussed through two different applications: (1) the multi-harmonic active structural acoustic control of a helicopter main transmission noise using piezoceramic actuators; (2) the broadband, adaptive sound field synthesis using multiple reproduction sources. It is shown that the approach allows decreasing the required signal processing and limiting the magnitude of the control inputs. Furthermore, in the case of sound field reproduction, it allows a very elegant and insightful interpretation in terms of controlling independent radiation modes.
Negative impedance and vibration control of beams and plates
Authors: Cunefare Kenneth A.
Published: October 2013

The use of piezoelectric actuators for noise and vibration control purposes is well established. Recently, however, the use of negative impedance circuits for the control of such actuators has received increasing attention. This paper considers the fundamental implications of negative impedance control when used in the context of active vibration suppression on beams and plates. It is shown that action of the negative impedance control may be related to the minimization of the reactive power delivered into the structure, thereby minimizing the standing wave field. If one takes the perspective that the vibration field on a structure is composed of direct and reverberant components, then minimization of the reactive power input leads to attenuation of the reverberant component. The reverberant response is global, such that its minimization leads to global vibration minimization.
Seismo-acoustic antivehicular landmine detection using phase data
Authors: Schneck Bill , Libbey Brad
Published: October 2013

Landmine detection is tactically important for main supply route clearance in counter-insurgency operations. Seismo-acoustic detection is one of multiple technologies being pursued by the Army in an effort to address this need. The experiments to be presented were designed to address the use of phase data for landmine detection. These experiments are, in large part, a replication of the efforts by T Wang et al. [Proc. SPIE 5415, 70–79 (2004)]. In the present work, phase and magnitude data are used to detect three targets: a V-S 1.6 anti-vehicular mine (easy target), an M-19 anti-tank mine (difficult target), and a resonant plate (very easy control). These were tested in four situations: free space, flush bury, 1 bury, and 2 bury. The soil surface velocity was measured using an array of four laser Doppler vibrometers, and the acoustic pressure used for excitation was recorded with a microphone. In certain instances, the relative phase between the surface vibration and acoustic pressure directly above the mine was different from soil alone.
Nonlinear acoustic landmine detection: Comparison of tuning curve experiments profiling on and off the target
Authors: Genis Sean A. , Korman Murray S.
Published: October 2013

Recent experiments [Proc. SPIE 6217, 62170Y, Detection and Remediation Technologies for Mines and Minelike Targets XI; J.T. Broach, R.S. Harmon, J.H. Holloway, Jr.; Eds. (2006)] have shown that the soil vibrating over a drum-like acrylic landmine simulant is more nonlinear on the target than well off (due to soil alone). Here, a Laser Doppler Vibrometer (LDV) is configured to scan laterally across the buried simulant. The 10 cm diameter, 5 cm high rigid simulant has a flexible clamped 0.8 mm thick top plate and is buried 4 cm deep in dry, sifted masonry sand in a rigid soil container placed inside the anechoic chamber. At each location the sand is subjected to a series of increasing amplitude acoustic pressure level sweeps (across a 50–200 Hz bandwidth) that includes the resonant behavior. The soil surface particle velocity vs. frequency tuning curves, from locations ‘‘off target’’ show relatively small nonlinear effects, while those from locations ‘‘on target’’ exhibit clearly identifiable backbone (peak amplitude vs. corresponding resonant frequency) curves that exhibit softening. Profiles of the backbone slope vs. position indicate an extremely large contrast ratio between ‘‘on’’ and ‘‘off’’ locations compared to profiles of surface vibration obtained near resonance. [Work supported by ONR.]
A long-term field soil survey by acoustic techniques: Part I. Linear acoustics
Authors: Lu Zhiqu
Published: October 2013

Soils are complicated, multiphase granular materials; their behavior is determined by the discrete nature of these media, external and interparticle forces, interconnected porosity, and multiphase conditions. In a real world, the properties of field soils change ceaselessly due to seasonal and climate effects. It is generally difficult or impossible to simulate field soil conditions in the lab. To study and monitor the evolution process of soil properties, acoustic techniques are invoked for a long-term field soil survey. In this study, an acoustic probe with five acoustic transducers is inserted into the ground with minimum disturbance of soils. At different depths, sound speed, temperature, moisture, soil suction, and rain precipitation are recorded continuously. It is found that temperature has a negligible effect on the sound speed, moisture plays a minor role, and soil suction is the predominant factor governing the sound speed of the shallow field soil. Terzaghi’s principle of effective stress is brought to explain the observations.
Nonlinear dynamics and time reversed acoustic imaging in damaged solids
Authors: Ulrich T. J. , Anderson Brian E. , Johnson Paul A. , Sutin Alexander M. , Guyer Robert A.
Published: October 2013

Our ultimate goal is locating and imaging nonlinear scatterers in solids (e.g., cracks) without a priori knowledge of their existence. Toward that goal, two methods have been devised that combine the spatial and temporal focusing abilities of TRA with nonlinear elastic wave spectroscopy’s (NEWS) sensitivity to mechanical damage. The first method uses TRA to create large amplitude signals and induce a nonlinear response in a highly localized region on a sample surface. Repeating the process in a step-scan approach provides the means to image the sample surface/near-surface with high resolution, distinguishing nonlinear features (cracks) from the linear background (undamaged material). The second method takes advantage of TRA to focus acoustic energy from two input frequencies onto an unknown, but nonlinear, scattering source, creating nonlinear wave modulation. The time reversal mirror (TRM) array records the primary and scattering source waveforms. Filtering the recorded signals for a modulation sideband, time reversing, and rebroadcasting through the TRM focuses the filtered signal onto the source of the modulation—the crack. Experimental results demonstrating each technique will be presented. [This work was supported by Institutional Support (LDRD) at Los Alamos National Laboratory.]
The object of perception in impacted sound sources: The role of perceptual accessibility and information accuracy
Authors: Giordano Bruno L. , McAdams Stephen , Rocchesso Davide
Published: October 2013

Two independent principles could potentially govern integration of information in the perception of a sound source. First, higher perceptual weights should be given to acoustical parameters that specify accurately and unambiguously a sound source property. Second, lower perceptual weights should be given to acoustical parameters related to less perceptually accessible information (e.g., impaired discrimination). The relevance of these principles to source perception was investigated. Hardness perception was investigated for the two objects whose interaction generates an impact sound: a highly damped hammer and a freely vibrating sounding object. Acoustical analyses identified unambiguous and relatively accurate acoustical specifiers of the impacted sound source. A first experiment assessed the ability of a listener to learn to discriminate hammer or sounding object hardness, providing a measure of the perceptual accessibility of the two source properties. A second experiment investigated hardness estimation in trained and untrained listeners, providing quantification of the relative perceptual relevance of the informational sources. A final experiment conducted on simulated sound sources further characterized weighting profiles in untrained listeners, decorrelating otherwise covarying source properties. Results concerning both mechanical and acoustical correlates suggest a relevance of both principles.
Fourth formant dip as a correlate of American English flaps
Authors: Dungan Mary , Morian Karen , Tucker Benjamin V. , Warner Natasha
Published: October 2013

Unlike the lower formant frequencies, the fourth formant frequency (F4) is rarely an important acoustic correlate of speech. This study shows evidence of a depression in F4 for some tokens of the American English flap. F4 may be lowered during American English /r/ (Espy-Wilson et al., 2000) and during retroflex sounds of some languages (e.g., Pima, as found by Avelino and Kim, 2002), but other cues are likely to be more prominent for such sounds. The current project uses a corpus of acoustic measurements of flapped English /t, d/ (e.g., pretty, order) and shows an inconsistent but large drop in F4 at the flap consonant. This occurs predominantly near an /r/, but the F4 drop is timed to the flap, not the /r/. In some tokens, this F4 drop occurs even if the flap is reduced to an approximant, leaving few other acoustic cues to its presence. The F4 drop likely reflects a sublingual cavity resonance caused by an interaction of the tongue positions for /r/ and for a flap. This study presents results on the distribution, frequency of occurrence, and magnitude of the F4 drop. Future research will investigate the perceptual role of the F4 drop.
Incomplete neutralization of /t/ and /d/ in flapping environments: An analysis of the North Midland dialect of American English
Authors: Herd Wendy J.
Published: October 2013

This paper presents an acoustic study of alveolar flaps in American English as produced by 20 speakers of a North Midland dialect spoken in the Kansas area. Participants read three lists of 164 monosyllabic and disyllabic words and nonwords containing word-final and medial /t/ and /d/. Vowel duration differences in monosyllabic and disyllabic tokens and consonant duration differences in monosyllabic tokens duplicated previous findings in that vowels preceding /d/ were significantly longer than those preceding /t/ and in that the average duration of /t/ was significantly longer than that of /d/. However, flap duration measured significantly longer for /d/-flaps than /t/-flaps. When analyzing flap frequency, it was also discovered that females flapped significantly more often than males and that participants were more likely to flap when they were less aware of the contrast between /t/ and /d/. While previous research reported that monomorphemic and high-frequency words are more likely to be flapped than bimorphemic and low-frequency words, neither word frequency nor morphological complexity affected flap frequency in the present study. Flap frequency was based on a method of distinguishing flapped from unflapped stops on a speaker-by-speaker basis, a more accurate method than that used in previous studies.
Production of Parisian stops word-initial stops in the vicinity of a voiceless stop
Authors: Abdelli-Beruh Nassima
Published: October 2013

This study examines how French speakers produced stop voicing contrasts in the sentence répète CVC tout-de-suite. Durations (sentence, vowel before and after word-initial stops, closure voicing, VOT) and number of produced stop closures (/t/, /C/) were collected. There was a strong positive correlation between speaker’s sentence durations and number of closure produced: Rapid speakers produced mostly one closure, whereas slow speakers generally produced two closures. One-closure and two-closure productions were separately analyzed. In the two-closure productions, significant (longer voicing in the /t/ closure in anticipation of /bdg/ than /ptk/, longer closure voicing for /bdg/ than for /ptk/, longer vowel duration following /bdg/ than /ptk/) and nonsignificant voicing-related duration differences (e.g., closure) were found. Unlike in the two-closure productions, average closure duration was significantly longer before /ptk/ than before /bdg/, while there was no significant voicing-conditioned effect of the word-initial stop on the duration of the following vowel in the one-closure productions. As in the two-closure productions, average closure voicing duration remained significantly longer before /bdg/ than before /ptk/. Findings suggest that closure voicing remains the most salient cue to the voicing distinction irrespective of contextual and speaking rate variations.
Sequential Bayesian signal processing: An overview
Authors: Candy James
Published: October 2013

Bayesian signal processing is concerned with the estimation of an underlying posterior distribution to extract statistics (inference) solving a variety of problems (signal enhancement, detection, parameter estimation, etc.). The technique simply employs Bayes rule to estimate the posterior using all of the data available at the time. Bayesian methods require approaches that capture all of the a priori information available and are typically model-based employing mathematical representations of the embedded processes. An overview of Bayesian inference from batch to sequential processors is presented. Once the evolving Bayesian paradigm is established, simulation-based methods using sampling theory and Monte Carlo realizations are discussed. Here the usual limitations prevalent in classical processing algorithms (e.g., Kalman filters) are no longer a restriction to perform Bayesian inference. Next importance sampling methods are briefly discussed and shown how they can be extended to sequential solutions implemented using Markovian models as a natural evolution. With this in mind, the idea of a particle filter, which is a discrete representation of a probability distribution, is developed and shown how it can be implemented using sequential importance sampling/resampling methods. Finally, a set of applications is briefly discussed comparing the performance of the particle filter designs with classical implementations.
Bayesian inversion methods in ocean geoacoustics
Authors: Dosso Stan E.
Published: October 2013

This paper describes a complete approach to the inversion of ocean acoustic data for environmental model parameters, which is also applicable to other inverse problems. Within a Bayesian formulation, the general solution is given by the posterior probability density (PPD) of the model parameters, which includes both data and prior information. Properties of the PPD, such as optimal parameter estimates, variance/covariance, inter-parameter correlations, and marginal probability distributions, are computed numerically for nonlinear inverse problems using Markov-chain Monte Carlo (MCMC) importance sampling methods. Since the data uncertainty distribution (including measurement and theory errors) is generally not known a priori, a simple, physically-reasonable form, such as a Gaussian or double-exponential distribution, is assumed, with statistical properties estimated from data residual analysis. In many cases, the full error covariance matrix (including off-diagonal terms) is required, and in some cases effects of nonstationary errors must be included. If biased data errors are suspected, additional unknown parameters representing the biases are included explicitly in the inversion. The validity/applicability of the above assumptions and estimates is examined a posteriori by applying both qualitative and quantitative statistical tests. New advances in efficient and adaptive MCMC sampling for nonlinear inversion will be presented.
The estimated ocean detector: Detection of signals with different parameter distributions
Authors: Ballard Jeffrey , Jemmott Colin , Culver R. Lee , Sibul Leon
Published: October 2013

Earlier we presented a maximum likelihood receiver for acoustic signals that have propagated through a random or uncertain ocean, the estimated ocean detector (EOD) [Ballard et al., Oceans 2006, Boston, MA]. In general, the EOD incorporates statistical knowledge of signal uncertainty in the form of signal parameters probability density functions (pdfs). Note that Monte Carlo simulation and possibly other techniques can utilize deterministic and statistical knowledge of the environmental to predict signal parameter pdfs. The EOD utilizes the a priori signal parameter pdfs to estimate signal parameters from the data (or observations), then correlates the estimate with the data; hence, the name estimator-correlator is also used. Previously we showed that, for Gaussian signals embedded in Gaussian noise, the EOD reduces to the weighted sum of an energy detector and a correlation detector. This talk presents an EOD formulated to distinguish between signals whose parameters possess different a priori distributions. Performance is seen to depend upon the difference between parameter distributions for the two different signals. [Work supported by ONR Undersea Signal Processing Code 321US.]
Introduction to workshop goals
Authors: Hoover Anthony K. , Brooks Bennett M.
Published: October 2013

Many states require that architects obtain continuing education unit (CEU) credits annually, in order to maintain their registration or licensure. The American Institute of Architects (AIA) Continuing Education System (CES) offers continuing education courses, which may be given by third party providers. The Technical Committee on Architectural Acoustics (TCAA) is an AIA/CES Registered Provider. The goal of this workshop is to prepare members of the TCAA so that they may be authorized to present a short course that can earn attendees CEU credit. In order for TCAA members to qualify to meet the AIA requirements, they must attend this workshop, which is given in two parts. The first part will be devoted to the short course presentation material, which is in a standardized format. The second part of the workshop will focus on the AIA CEU Program registration and reporting requirements. Of course, anyone is free to register with the AIA to provide their own CEU program. However, the advantages of participating in this program are that the TCAA short course is already prepared, is preapproved by the AIA, and the registration fees are paid by the Acoustical Society of America.
Modeling room impulse response by incorporating speaker polar response into image source method
Authors: Chen Zhixin , Maher Robert
Published: October 2013

Simple computer modeling of impulse responses for small rectangular rooms is typically based on the image source method, which results in an impulse response with very high time resolution. The image source method is easy to implement, but the simulated impulse responses are often a poor match to measured impulse responses because the description of the source is often too idealized to match the real measurement conditions. For example, the basic image source method has often assumed the sound source to be an omni-directional point source for ease of implementation, but a real loudspeaker may include multiple drivers and exhibit an irregular polar response in both the horizontal and vertical directions. In this paper, an improved room impulse response computer modeling technique is developed by incorporating the measured horizontal and vertical polar responses of the speaker into the basic image source method. Results show that compared with the basic image source method, the modeled room impulse response using this method is a better match to the measured room impulse response.
Head and torso simulators
Authors: Rasmussen Gunnar
Published: October 2013

The KEMAR was developed by Knowles Electronics and introduced in 1972, thoroughly described by Mahlon D. Burkhard, and standardized in ANSI S3.361ASA58-1985. The KEMAR was provided with ears typical of American and European females as well as Japanese males and females. Larger ears more typical of American and European males have been developed with well-defined hardness of 0055 and 0035 shore. The ears are readily exchanged with the ITU P57 Type 3.3 ear. The KEMAR is designed to offer lifelike reproducible test conditions and is therefore based on average anthropometric dimensions of an adult human, while other HATS are designed using simplified or average geometric convenient dimensions. The KEMAR may be provided with an artificial mouth system with well-defined characteristics. The KEMAR also offers well-defined positioning of microphones for linearization as well as positioning systems for handheld communication systems. Measurements show good agreement with early data published by M. D. Burkhard and R. M. Sachs [‘‘Anthropometric Manikin for Acoustic Research,’’ JASA 58, 214–222 (1975)]. Conclusion: Acoustical measurements carried out since 1972 can still be compared and carried out on a system, which has not changed acoustically except for increased versatility and improved acoustic documentation.
Ultrasonic resonance spectroscopy for cryogenic materials
Authors: Petculescu Petre , Zagan Remus , Petculescu Andi
Published: October 2013

Cryogenic steels are needed in the construction of industrial installations able to withstand low temperatures. This poster presents results on the use of an ultrasonic resonant technique to determine the composition of the cryogenic stainless steel 10TiNiCr180 with an austenitic structure. The investigations were done both in the base material and in the weld, with and without thermal treatment. Upon exposing the sample to two thermal treatments (welding-hardening and welding-hardening-annealing), metallographic analysis showed the presence of chromium carbide in the base material and the weld. The ultrasonic power spectrum shows a prevalent austenitic structure in the base material and a compound austenite-ferrite-chromium carbide structure in the weld. The grain size determined from the spectral peak ratio is compared with the one obtained by metallographic analysis. The measurements presented here were obtained in direct contact with the pulse-echo technique, with excitation centered at 5 MHz.
Myth-busting brass instrument design
Authors: Smith Richard A.
Published: October 2013

Richard Smith has designed and made instruments for professional brass players for over 35 years. With a background as scientist and musician, he has a unique view of the subject in which his myth-busting has been a dominant feature. The challenge now is to transfer this knowledge to music educators and players. It can be shown that any instrument is a compromise of musical qualities, making the quest for the perfect instrument pointless and a distraction from the real business of making music. Resistance is probably the most difficult of these musical qualities to interpret from player responses. It will be demonstrated how the language of fluid dynamics has been wrongly adopted by players, educators, and manufacturers to give pseudo-scientific authority to their teaching and product promotion. The development of a blindfold testing technique by Smith was crucial to (a) the study of materials used in instrument construction and (b) a breakthrough in efficient instrument design. Current work with Thomas Moore (Rollins College, USA) and David Howard (University of York, UK) investigates the mystery of hi-note playing on the trumpet where the most skilled players find distinct slots above 2 kHz in, according to acoustical textbooks, a resonance free zone.
On the need for musical instrument strings to dynamically stretch
Authors: Davis Evan B.
Published: October 2013

Given clamped or fixed boundary conditions a string must stretch or elongate to vibrate. Many have analyzed the effect of string stretch under the fixed boundary condition assumption and the related nonlinear motion of the string. However, if the boundary of the string at the soundboard was fixed the soundboard would not move. A rigid soundboard is not a very useful design for the production of music. It will be shown that there are geometries which allow soundboard motion without string stretch well as geometries that require string stretch for soundboard motion.
Advanced digitally adjustable analog feedback control system and its usage in active noise insulation
Authors: Antila Marko , Nykanen Hannu , Kataja Jari , Mellin Velipekka
Published: October 2013

Feedback control for the active noise cancellation can be done with analog or digital circuitry. Although digital approach is steadily gaining ground, analog control still has its uses. Short control latency is the feature of an analog controller—it has the shortest possible delay. Its drawback is the limited flexibility for adjustable or adaptive solutions. To overcome this, digitally adjustable analog controllers can be used. A potential implementation for such controller uses field programmable analog array (FPAA) technology. With FPAAs both the filter parameters and structure are digitally adjustable, even during the operation. A development environment around the FPAA controller has been devised. It consists of the measurement system, an optimizer that calculates the optimum controller response, programming software, and actual FPAA hardware with its embedded software. The complete system is packaged tightly to a compact form. It can be used for evaluation purposes in acoustics laboratory conditions. Such a system has been evaluated in active noise insulation application. It has proven to operate as simulated and optimized also in real-world tests. The future development of the system includes further miniaturization, controller networking, and possible integration inside the sound insulation system.
Optimization of control source locations in an active noise control application of axial cooling fans using genetic algorithms
Authors: Duke Connor R. , Sommerfeldt Scott D. , Gee Kent L.
Published: October 2013

By placing control sources in the near field, global attenuation of an axial cooling fan’s blade passage frequency and harmonics can be achieved using active noise control. The optimal position of control sources when modeling a fan, whose characteristics differ significantly from a single monopole source or when modeling more than one fan, will be discussed. The number of control sources, as well as position of control sources, are optimized for specific primary source configurations using genetic algorithms. Source strength of control sources are calculated analytically to minimize radiated sound power. The results of optimization using different forms of genetic algorithms will be presented and compared. The results obtained from the genetic algorithms will be compared to experimental results using multiple sources.