• Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Proceedings of Meetings on Acoustics

BROWSE VOLUMES

Year Range: 
Search Volume | RSS Feeds RSS
POMA - 156th Meeting Acoustical Society of America
Conference Location: Miami, Florida Conference Date: 10 - 14 November 2008
Page 1 of 2 Pages Next Page | Jump to Page
back to top
RSS Feeds
FREE

The physical mechanism (viscosity related) of low frequency acoustic wave attenuation in sandy/silty sediments

Allan D. Pierce and William M. Carey

POMA Volume 5, pp. 005001 (December 2008); (12 pages)

Online Publication Date: December 15, 2008

Full Text: | Download PDF

Show Abstract
Considered saturated sediments contain diverse rock pebbles (characteristic size of 0.1 mm). The weight of higher pebbles holds lower pebbles in contact sufficiently that acoustically induced solid displacements vary slowly over several adjacent pebbles. Apart from contact areas, each is nearly surrounded by water at a nearly uniform pressure. An appropriate first approximation predicts that the elastic stress tensor in the pebbles is diagonal, with components equal to the negative of the acoustic pressure in the neighboring fluid. The assumptions of Mallock and Wood apply: the mass weighted local average velocity is proportional to the negative gradient of the pressure in the water. The no-slip condition at the interfaces tends to force the water to move with the pebbles, but the finite viscosity allows the fluid at small distances from the interfaces to move at a different velocity than the pebbles. The apparent driving force for the oscillations of the interstitial water relative to the pebbles is associated with the inertia of the water and is proportional to the difference in densities. The derived approximate wave equation predicts attenuation proportional to frequency squared, proportional to the square of the difference of the densities, and inversely proportional to viscosity.
Show PACS
43.30.Ma Acoustics of sediments; ice covers, viscoelastic media; seismic underwater acoustics
FREE

On the exponential power law for low frequency attenuation in shallow water

William M. Carey

POMA Volume 5, pp. 005002 (August 2009); (14 pages)

Online Publication Date: August 28, 2009

Full Text: | Download PDF

Show Abstract
Reviews of measured shallow-water sound transmission over sandy-silty bottoms show the intrinsic attenuation for low frequencies (< fo=1 kHz) to vary with as (f/fo) to the 1.8 power. Since plausible theory suggests this dependence should be (f/fo)to the 2.0 power, then why are the observed values different? Calculations incorporating scattering, layering,and gradients were found not to explain this observation. The discrepancy can be explained when an additional attenuation mechanism where generated lower velocity shear waves carry energy downwards out of the waveguide is considered. Since the intrinsic attenuation and the apparent attenuation due to shear wave conversion are small, the observed attenuation can have a different frequency dependence. If the removal of energy from the field due to shear wave conversion is comparable to the intrinsic attenuation at the lower frequencies but less than the intrinsic attenuation at the higher frequencies; the inferred frequency dependence can be less than quadratic. Inversions with fluid sediments account for this effect by the site-specific factors that accounts for the loss of energy from the compressible field due shear wave conversion.
Show PACS
43.25.Ed Effect of nonlinearity on velocity and attenuation
43.30.Bp Normal mode propagation of sound in water
43.30.Ma Acoustics of sediments; ice covers, viscoelastic media; seismic underwater acoustics
back to top
RSS Feeds
FREE

W. C. Sabine's personal papers

Leo L. Beranek

POMA Volume 5, pp. 015001 (December 2008); (8 pages)

Online Publication Date: December 24, 2008

Full Text: | Download PDF

Show Abstract
In 1975, the notebooks of Wallace Clement Sabine were discovered and in 1979 his consulting files were found. Both findings were reported [J. Acous. Soc. Am. 61, 629-639 (1977); J. Acous. Soc. Am. 69, 1-6 (1981)]. By chance, Sabine's personal papers were discovered recently and highlights from them will be presented with emphasis on his European activies.
Show PACS
43.10.Gi Editorials, Forum
43.55.Fw Auditorium and enclosure design
FREE

Leadership in Energy and Environmental Design for Schools-2009 Acoustics Prerequisite and Credit - Evolution and Future Direction

Alexis D. Kurtz, Daniel C. Bruck, Charles Salter, and David Lubman

POMA Volume 5, pp. 015002 (February 2009); (5 pages)

Online Publication Date: February 25, 2009

Full Text: | Download PDF

Show Abstract
In May 2008, the U. S. Green Building Council (USGBC) released an updated acoustics prerequisite and credit for inclusion in the LEED (Leadership in Energy and Environmental Design) for Schools 2009 Rating System. Guidance for the update was provided to the USGBC by the four acousticians in the Indoor Environmental Quality Technical Advisory Group, which focused on identification of key acoustical metrics and development of the credit for greater acceptance within the design and construction community. This paper discusses the process and challenges of balancing market factors, cost, and effective acoustical design for classrooms. The resulting prerequisite and credit are intended to be easily attainable within reasonable cost constraints for classrooms in all geographic regions of the United States. Future direction for classroom acoustics in green design, implications arising from poor classroom design, and the need for greater involvement of the acoustics community in credit development will also be discussed.
Show PACS
43.55.Br Room acoustics: theory and experiment; reverberation, normal modes, diffusion, transient and steady-state response
back to top
RSS Feeds
FREE

Biphasic models of soft tissues for ultrasound applications

Elisabetta Sassaroli, Brian E. O'Neill, and King C. Li

POMA Volume 5, pp. 020001 (November 2008); (6 pages)

Online Publication Date: November 21, 2008

Full Text: | Download PDF

Show Abstract
A theoretical model for describing ultrasound propagation in soft tissue modeled as a solid-fluid aggregate is described. The biphasic theory developed by Mow and coworkers can explain correctly the flow and deformation of soft hydrated tissues under a variety of conditions. It is shown here that the biphasic theory can be derived from Biot's theory of porous elastic materials saturated with fluid when both phases the solid phase and fluid phase are considered intrinsically incompressible. The biphasic theory is then extended to include ultrasound propagation. This extension follows very closely Biot's work. The proposed model, if confirmed experimentally, could be a powerful phenomenological tool to plan and interpret data of ultrasound propagation in soft tissues.
Show PACS
43.80.Cs Acoustical characteristics of biological media: molecular species, cellular level tissues
43.80.Ev Acoustical measurement methods in biological systems and media
43.80.Gx Mechanisms of action of acoustic energy on biological systems: physical processes, sites of action
43.80.Jz Use of acoustic energy (with or without other forms) in studies of structure and function of biological systems
FREE

Coupled two-phase model of a gas microbubble containing suspended light absorbing nonoparticles

Elisabetta Sassaroli, Brian E. O'Neill, and King C. Li

POMA Volume 5, pp. 020002 (November 2008); (5 pages)

Online Publication Date: November 21, 2008

Full Text: | Download PDF

Show Abstract
A mathematical model of a micrometer size gas bubble containing nanometer size light absorbing nanoparticles is presented. A description of such a system can be obtained in terms of a two-coupled phase model with the solid particles in suspension in a fluid phase, i.e. the gas. It is assumed that the suspension is diluted so that particle-particle interaction can be ignored. Because the heat exchange between the nanoparticles and the gas is of main interest in this calculation, it is assumed in first approximation that the gas and the particles have the same velocity and pressure. The pressure is assumed to be function of time only. In this case, only the equations of continuity and energy for both the particulate phase and the gas phase. The two-coupled model is then solved in linear approximation and a system of four differential equations with constant coefficients is obtained. The system is diagonalized and the general solution of the two coupled system is obtained. The general solution is a combination of exponential decaying oscillatory functions for the temperature of the two phases, the pressure and the microbubble radial oscillations. It was found that the oscillatory behavior takes place in the MHz range.
Show PACS
43.35.Ei Acoustic cavitation in liquids
43.35.Sx Acoustooptical effects, optoacoustics, acoustical visualization, acoustical microscopy, and acoustical holography
43.35.Ty Other physical effects of sound
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
back to top
RSS Feeds
FREE

A Helmholtz resonator experiment for the Listen Up project

Chad A. Greene, Theodore F. Argo IV, and Preston S. Wilson

POMA Volume 5, pp. 025001 (March 2009); (7 pages)

Online Publication Date: March 13, 2009

Full Text: | Download PDF

Show Abstract
The Listen Up project seeks to develop an educational booklet and apparatus that will be used to foster interest in acoustics and teach basic acoustical concepts to middle school students. The packaged kit must be low-cost, hence this experiment uses only a 16 oz. plastic water bottle as a Helmholtz resonator and an inexpensive pitch pipe as a frequency reference. Understanding the Helmholtz resonator is fundamental to many applications in acoustics. A simple algebraic model of the device, derived from a mechanical mass-spring analogy, relates the volume of air in the bottle to the resonance frequency of the system, and hence the pitch that is produced when one blows over the bottle opening. The volume of air inside the bottle can be easily quantified by labeled graduations on the bottle. The dependence of pitch on the volume of air in the bottle can be systematically demonstrated, and the validity of the model can be checked by comparing the sound produced to musical notes from the pitch pipe. This experiment yields a physical understanding of a common acoustical phenomenon, and inspires further interest and study more complex phenomena.
Show PACS
43.20.Ks Standing waves, resonance, normal modes
back to top
RSS Feeds
FREE

Development of a portable therapeutic ultrasound system for military, medical and research use

George K. Lewis Jr. and Willam L. Olbricht

POMA Volume 5, pp. 030001 (December 2008); (12 pages)

Online Publication Date: December 24, 2008

Full Text: | Download PDF

Show Abstract
In the past two decades therapeutic ultrasound has obtained attention by the medical community as a tool to relieve arthritis, improve rehabilitation, and enhance wound healing processes. In the research realm, therapeutic ultrasound and its effects on tissue properties are currently being studied to great lengths. For example, researchers are assessing the ability of ultrasound for large molecule transdermal drug delivery, in targeted chemotherapy delivery to brain cancer, and cellular gene-transfer applications. Even though many applications of therapeutic ultrasound exist, the basic instrumentation has not changed much in the past 50 years. Here, we present a novel therapeutic ultrasound system we developed in our laboratory that is capable of producing acoustic power outputs well over the therapeutic range greater than 50 W, lightweight (under 6 lb), portable (a foot print of 4x6x2 in.3), and rechargeable battery powered. The portable therapeutic ultrasound unit has the potential to replace plug-in medical systems and rf amplifiers used in research, both of which are bulky and burdensome. The portable system is capable of between-office and field service on its long lasting internal battery, making it especially useful for military, ambulatory, and house-call medical applications.
Show PACS
43.38.Lc Amplifiers, attenuators, and audio controls
43.80.Ev Acoustical measurement methods in biological systems and media
43.80.Vj Acoustical medical instrumentation and measurement techniques
back to top
RSS Feeds
FREE

Drum tuning: an experimental analysis of membrane modes under non-uniform tension

Randy Worland

POMA Volume 5, pp. 035001 (May 2009); (12 pages)

Online Publication Date: May 02, 2009

Full Text: | Download PDF

Show Abstract
Results of an experimental study of normal mode vibrations in single-headed musical drums under non-uniform tension are presented. Although uniform tension is often assumed in theoretical treatments, in practice the musical drum only approximates this condition, even after careful tuning by the drummer. This study investigates the behavior of normal mode shapes and frequencies under non-uniform tension, as they relate to the tuning process. In particular, the role of the (1,1) mode is described. Experimental results include electronic speckle pattern interferometry (ESPI) images of modal shapes along with the associated frequencies. A finite element model is used for comparison with the experimental results.
Show PACS
43.75.Hi Drums
back to top
RSS Feeds
FREE

Evaluation of Discrete Vehicle Accident Sounds for use in Accident Reconstruction

William Neale, Toby Terpstra, and William Bortles

POMA Volume 5, pp. 040001 (November 2008); (12 pages)

Online Publication Date: November 26, 2008

Full Text: | Download PDF

Show Abstract
Vehicle accidents are complicated events and the resulting sound sequence created by that event is equally complex. Understanding how accident sounds are created is important for two main reasons. One reason is to better understand the events in an accident sequence that have not left visible physical evidence. There are often witnesses to vehicle accidents, and their observations include what they saw as well as what they heard. This information is useful when reconstructing the accident. Another reason is to be able to create more accurate simulated sound composites of an accident for use in forensic visualization, a visual/auditory tool that helps one understand a dynamic accident sequence that they were not able to see in person. While the composite accident sound is complicated when analyzed as an entire sound sequence it is still derived from discreet parts, and by analyzing the discreet parts individually one is able to better understand the contribution each individual sound makes to the entire accident sound sequence. This paper looks at some of the discreet sounds in a vehicle accident, and evaluates how changes in the parameters of the accident sequence affect the resulting sounds.
Show PACS
43.50.Lj Transportation noise sources: air, road, rail, and marine vehicles
43.50.Rq Environmental noise, measurement, analysis, statistical characteristics
FREE

Investigation and analysis of urban noise for sustainability

Martha Orozco-Medina, Arturo Figueroa, and Javier García

POMA Volume 5, pp. 040002 (December 2008); (10 pages)

Online Publication Date: December 15, 2008

Full Text: | Download PDF

Show Abstract
The concept of urban sustainability involves complex issues such as, civil services, social participation, resilience, productivity, health and development into a multi-level approach of environmental, social and productivity sectors. Viewing environmental noise as part of urban dynamics is essential. However it is almost absent, or underestimated in most of current environmental, social and health policies in the developing world. Efforts to investigate noise pollution towards analysis, regulation, fulfillment, inspection and fines, contribute in a positive way to improve acoustic quality within urban communities. Therefore the ultimate goal to decision makers is to consider noise as a key issue, when establishing or discussing management policies of urban areas, and to transfer the approach to lower levels with preventive and educational measures, rather than restrictive or prohibited, in order to attain sustainability of urban communities.
Show PACS
43.50.Qp Effects of noise on man and society
43.50.Rq Environmental noise, measurement, analysis, statistical characteristics
43.50.Sr Community noise, noise zoning, by-laws, and legislation
FREE

Outdoor to indoor A-weighted sound level reduction of typical modular classrooms and assessment of potential performance improvements based on the outdoor-indoor transmission class spectrum

Noral Stewart

POMA Volume 5, pp. 040003 (January 2009); (6 pages)

Online Publication Date: January 29, 2009

Full Text: | Download PDF

Show Abstract
Several different designs for modular classrooms from various parts of the United States were examined for their expected A-weighted outdoor to indoor sound level reduction based on the sound spectrum used for the ASTM E1332 Outdoor Indoor Transmission Class (OITC). Analysis was simplified by using an average absorption effect and the OITC rating of walls and roofs as estimated using the INSUL computer program. Results showed a significant variation among designs with the better designs providing a good foundation for further improvement.
Show PACS
43.55.Ti Sound-isolating structures, values of transmission coefficients
FREE

Understanding the acoustical implications of Underwriters Lab (UL) listings

Matthew V. Golden

POMA Volume 5, pp. 040004 (February 2009); (16 pages)

Online Publication Date: February 25, 2009

Full Text: | Download PDF

Show Abstract
With today's ever more complicated building design, acoustical consultants should be aware of how their recommendations affect other aspects of floor/ceiling design. The acoustical ratings must be balanced with the need for fire rated assemblies as well as structural requirements. As the industry leader in the listing of fire rated designs, the Underwriters Lab (UL) maintains a list of assemblies that will meet various levels of fire resistance. These listings are very detailed and even slight changes to the design can have a profound impact on the assembly's fire resistance rating. This paper will compare various listed wood-frame floor/ceilings assemblies with respect to acoustical design. These comparisons will include fiberglass thickness, number of drywall layers, resilient channel spacing, and types of resilient sound clips. The general affect of each of those variables on acoustical performance will be shown. Several insights will also be shared from the acoustical supplier's perspective on the UL listing experience.
Show PACS
43.55.Ti Sound-isolating structures, values of transmission coefficients
43.55.Vj Vibration-isolating supports in building acoustics
back to top
RSS Feeds
FREE

The influence of Hank Bass on ground effect research between 1981 and 1995

Keith Attenborough

POMA Volume 5, pp. 045001 (November 2008); (7 pages)

Online Publication Date: November 21, 2008

Full Text: | Download PDF

Show Abstract
In 1981 Bolen and Bass published a paper on ground effect which included a pioneering effort to deduce ground impedance from propagation data. This study can be regarded as a basis for current revision of the ANSI S1 1998 standard for measuring ground impedance. The author's first interaction with Henry Bass (Hank) in the same year stemmed from mutual interest in observations of buried geophone responses to airborne sound sources. Our initial experiments involved understanding such responses and the relationship of ground properties to the phenomenon of ground effect. Subsequent work by Hank and colleagues initiated modeling of the ground as a layered poroelastic medium. In this paper are highlighted the several pioneering efforts and observations in the Bolen and Bass 1981 paper. Most remarkable of these were their deductions of values of ground impedance at low frequencies. But other important observations concerned the assumption of local reaction, the spatial variability of ground properties, the adequacy of a popular one-parameter ground impedance model and the mechanisms by which sound penetrates the ground. Some of the issues raised by Bolen and Bass are the subject of continuing research and recent related developments are reviewed.
Show PACS
43.20.Hq Velocity and attenuation of acoustic waves
43.20.Jr Velocity and attenuation of elastic and poroelastic waves
43.28.En Interaction of sound with ground surfaces, ground cover and topography, acoustic impedance of outdoor surfaces
43.28.We Measurement methods and instrumentation for remote sensing and for inverse problems
FREE

Computation of three-dimensional, pulsed, nonlinear acoustic wavefields from medical phased array transducers in very large domains

Jacob Huijssen, Martin Verweij, and Nico De Jong

POMA Volume 5, pp. 045002 (April 2009); (16 pages)

Online Publication Date: April 29, 2009

Full Text: | Download PDF

Show Abstract
For the optimization and development of medical ultrasound transducers and imaging modalities, the Iterative Nonlinear Contrast Source (INCS) method has been developed. This numerical method predicts the nonlinear acoustic pressure field, generated by a pulsed, plane source with an arbitrary aperture, and propagating in a three-dimensional tissue-like medium that extends over a very large domain of interest. The INCS method obtains the acoustic pressure from the nonlinear acoustic wave equation by treating the nonlinear term as a contrast source. The full nonlinear wave field is then found by iteratively solving the linearized wave problem using a Green's function method. By employing the Filtered Convolution method discussed in a companion paper, accurate field predictions are obtained at a discretization approaching two points per wavelength or period of the highest frequency of interest. In this paper, very large-scale, nonlinear field profiles are presented for transducers with cylindrical as well as phased array geometries, excited with a pulsed waveform having a center frequency of 1-2 MHz. Comparison with results obtained from models of reduced complexity shows that in all cases the INCS method accurately predicts the nonlinear field. [Work supported by STW and NCF.]
Show PACS
43.25.Cb Macrosonic propagation, finite amplitude sound; shock waves
back to top
RSS Feeds
FREE

Directional sources and beamforming

Christian Bouchard, David Havelock, and Martin Bouchard

POMA Volume 5, pp. 055001 (December 2008); (8 pages)

Online Publication Date: December 15, 2008

Full Text: | Download PDF

Show Abstract
Beamforming is done with an array of sensors to achieve a directional or spatially-specific response. It relies upon a model of the wave front (source model) arriving at the array to calculate the time delay, or frequency domain phase shift, that must be applied to the signal of each sensor so that they may be summed coherently. Beamforming may be used to improve signal to noise ratio, reduce reverberation, cancel interference, or estimate source location. In this talk the directionality of some real world sources that deviate from an ideal point source is discussed. Performance measures used to evaluate the directivity properties of a beamformer are reviewed. The validity of assuming a point source is examined and challenges for beamforming with non-point sources are discussed.
Show PACS
43.60.Dh Signal processing for communications: telephony and telemetry, sound pickup and reproduction, multimedia
43.60.Fg Acoustic array systems and processing, beam-forming
FREE

Orthogonal coding sequences for multiple-source study of outdoor noise propagation

David C. Waddington and Jamie Angus

POMA Volume 5, pp. 055002 (December 2008); (23 pages)

Online Publication Date: December 15, 2008

Full Text: | Download PDF

Show Abstract
This paper describes recent developments in the design of a coded acoustic signal for the study of outdoor sound propagation. Low signal-to-noise ratio is a common limitation in outdoor propagation investigations, and time variance of the air limits the amount of averaging. Recent work by the authors presented a coded acoustic signal approach consisting of a frequency carrier biphase-modulated by a specially designed pseudo-random code sequence to overcome these limitations. The "Inner and Outer" code sequence was specially designed for environmental sound propagation investigations, combining simultaneous fine time resolution and large range ambiguity, together with an ability to average and probe the propagation path. This approach is extended to multiple acoustic sources for the study of outdoor sound propagation, with the design of signals using orthogonal correlation sequences. The results illustrate that combinations of orthogonal coding and multiple carrier frequencies can permit continuous sound speed measurements in numerous vertical and horizontal directions, and might therefore be useful for acoustic tomographic applications.
Show PACS
43.60.Ek Acoustic signal coding, morphology, and transformation
FREE

Aggressive Adaptive Beamforming for Ambient Noise Inversion with a Limited-Aperture Sonar on an Autonomous Platform

Juan Arvelo

POMA Volume 5, pp. 055003 (December 2008); (13 pages)

Online Publication Date: December 15, 2008

Full Text: | Download PDF

Show Abstract
Bottom loss inference from ambient noise inversion has been shown to yield accurate and robust predictions of undersea sound propagation and sonar detection performance using vertical line arrays and a conventional beamformer [Arvelo, J. Acoust. Soc. Am., 123, 679, 2008]. However, any array with a vertical aperture should be good candidates for ambient noise inversion. The main problem with vertical line arrays is that they are not well suited to rapidly survey a large area. Platform translation with a vertical array is expected to cause extreme array shape distortions that could seriously limit the accuracy of the results. To mitigate array shape distortion, a smaller array with vertical aperture could be mounted on the survey platform, which would allow it to survey the area at greater speeds. The platform's diameter certainly limits the vertical aperture of the array. A limited vertical aperture limits the frequency range, resolution, and accuracy of the estimated bottom loss. Since the array is rigidly fixed to the platform's body, an aggressive adaptive beamformer may be adopted to increase the resolution and accuracy of the inverted bottom loss to very low frequencies. The performance is demonstrated via comparisons against conventional beamformers with numerical simulations and measurements.
Show PACS
43.30.Nb Noise in water; generation mechanisms and characteristics of the field
43.30.Pc Ocean parameter estimation by acoustical methods; remote sensing; imaging, inversion, acoustic tomography
43.30.Wi Passive sonar systems and algorithms, matched field processing in underwater acoustics
43.30.Xm Underwater measurement and calibration instrumentation and procedures
FREE

Geoacoustic inversion of ocean surface-wave noise with a littoral glider

Billy D. Jones

POMA Volume 5, pp. 055004 (December 2008); (28 pages)

Online Publication Date: December 31, 2008

Full Text: | Download PDF

Show Abstract
Passive acoustics can be used to characterize the ocean bottom in a littoral environment. Ocean surface-wave noise acts as a natural directional source that can be measured to obtain bottom loss and subsequently inverted to obtain bottom density, sound speed, attenuation, and layering structure. A physical ocean surface noise model is introduced and its horizontal/vertical spatial cross-correlations discussed. Acoustical energy conservation and its relation to bottom loss are discussed. The measurement method is a continuation of the ambient noise inversion work of [J. I. Arvelo, Jr., J. Acoust. Soc. Am. 123, 679-686 (2008)]. Aggressive adaptive beamforming is used for high-resolution bottom loss measurements with surface-wave noise as a source. Ambient noise measurements with an eight-element wire polyvinylidene fluoride (PVDF) vertical line array (VLA) mounted in the bow of a Littoral Glider (LG) are presented. Results from summer 2008 measurements in Port Madison, Washington are presented and compared against known bottom loss curves for the area.
Show PACS
43.30.Pc Ocean parameter estimation by acoustical methods; remote sensing; imaging, inversion, acoustic tomography
FREE

Real-time noise source identification using field programmable gate array (FPGA) technology

Kurt Veggeberg and Alex Zheng

POMA Volume 5, pp. 055005 (February 2009); (10 pages)

Online Publication Date: February 11, 2009

Full Text: | Download PDF

Show Abstract
Acoustic beamforming is usually used as an off-line analysis tool for noise source identification (NSI). The computational requirements of beamforming make real-time processing difficult to achieve in conventional NSI measurement systems. This limitation prevents conventional NSI measurement systems being used in applications like on-line monitoring. This paper presents the theory, design, and development of a real-time NSI measurement system based on reconfigurable I/O Field Programmable Gate Array (FPGA) technology. Some techniques used in applying beamforming analysis methods with an FPGA are outlined. Signal processing includes time filtering of input data and spatial beamforming with special treatment to obtain the best result. Pipelining methodology is used to make full use of the FPGA resources and reach high performance for real-time applications. Test examples are given to demonstrate the some applications for NSI.
Show PACS
43.60.Fg Acoustic array systems and processing, beam-forming
back to top
RSS Feeds
FREE

Recent improvements to the University of California, Los Angeles' voice synthesizer

Norma Antonanzas-Barroso, Jody Kreiman, and Bruce R. Gerratt

POMA Volume 5, pp. 060001 (December 2008); (8 pages)

Online Publication Date: December 10, 2008

Full Text: | Download PDF

Show Abstract
A number of enhancements have recently been added to the UCLA voice synthesizer. Additions have been made to add functionality, and to address several theoretical issues that arose during development and application. New functions include the ability to manipulate the source spectrum directly, by changing the slope and/or amplitude of a user-defined group of harmonics, or by manipulating individual harmonics directly. The synthesizer also allows users to add zeros to the vocal tract transfer function, improving modeling of many pathological voices. A number of other enhancements improve ability to create and systematically vary stimuli for perceptual experiments. Theoretical development has focused on the importance of pitch-synchronous Fourier analysis in modeling the voice source, particularly with respect to measuring and manipulating the amplitudes of H1 and H2. Issues surrounding spectral effects of upsampling, downsampling, and pulse stretching, which are needed for precise manipulation of F0, will also be discussed. This synthesizer is available with documentation as open source shareware at www.surgery.medsch.ucla.edu/glottalaffairs/, and copies will be available at the conference. [Work supported by NIH/NIDCD grant DC01797.]
Show PACS
43.72.Ja Speech synthesis and synthesis techniques
FREE

Effects of talker and token variability on perceptual learning of dialect categories

Cynthia G. Clopper and John K. Pate

POMA Volume 5, pp. 060002 (July 2009); (7 pages)

Online Publication Date: July 06, 2009

Full Text: | Download PDF

Show Abstract
Dialect classification is difficult for naive listeners, but perceptual learning tasks using sentence-length utterances have been shown to produce modest improvements in performance. The goal of the current study was to explore perceptual learning by naive listeners in a speeded dialect classification task with shorter, word-length utterances. In a series of experiments, participants were trained in a two-alternative forced-choice speeded dialect classification task (Cleveland vs. Cincinnati) with feedback and were then tested in the same task with novel talkers and novel words without feedback to assess learning. Variability in the stimulus materials in the training phase, including the number of talkers from each dialect and the number of different tokens produced by each talker, was manipulated across experiments to determine how variation in the input affected perceptual learning of dialect categories. The results revealed that training materials consisting of utterances produced by multiple different talkers from each dialect with multiple different tokens produced by each talker led to a significant improvement in dialect classification performance compared to a baseline condition without training. These findings suggest that dialect classification performance can improve with training on short, word-length utterances, but that robust dialect category learning requires high variability stimulus materials.
Show PACS
43.71.Bp Perception of voice and talker characteristics
FREE

On the relation between locus equations and subglottal resonances

Steven M. Lulich

POMA Volume 5, pp. 060003 (July 2009); (10 pages)

Online Publication Date: July 06, 2009

Full Text: | Download PDF

Show Abstract
In consonant-vowel transitions, it is well known that the frequency of the second formant at the onset of voicing (F2onset) is linearly correlated with the frequency of the second formant in the middle of the vowel (F2vowel). This correlation, which holds across vowel contexts, is an indication of the amount of coarticulation between the consonant and the vowel, and is characterized by a regression line (locus equation) with a slope and y-intercept that depend upon the consonant place of articulation. Furthermore, for a given place of articulation, slopes and y-intercepts of a collection of locus equations are inversely related. The cause of this inverse relation has not yet been explained. In this presentation it will be shown that the inverse relation implies that the coordinate system of the F2vowel vs. F2onset space is shifted away from the origin, and that the size of the shift is a function of both the place of articulation and of the second and third subglottal resonances.
Show PACS
43.70.Bk Models and theories of speech production
43.70.Fq Acoustical correlates of phonetic segments and suprasegmental properties: stress, timing, and intonation
43.72.Ar Speech analysis and analysis techniques; parametric representation of speech
back to top
RSS Feeds
FREE

Causality and mathematical models in vibration and acoustics, a realistic perspective

Allan D. Pierce

POMA Volume 5, pp. 065001 (December 2008); (17 pages)

Online Publication Date: December 31, 2008

Full Text: | Download PDF

Show Abstract
Causality principles are defined in the context of linear systems with time-independent properties. The primary concepts are those of a reponse function and of a transfer function. The existence of the latter strictly requires that the system be stable, and a causal response function can exist without the system being stable. The definition of the transfer function can be extended to the negative real axis and subsequently to the upper half plane for specific mathematical models of vibrating systems. Stability and consequently the use of causality considerations requires that there be no poles in the upper half plane. Examples are given for a one-degree-of-freedom vibrating system with various types of damping terms. Negative damping allows the existence of a causal response function but leads to an instable sytem. Fractional derivative damping is all right if the fractional power is less than 2. Consideration of arbitrary multi-degree-of-freedom systems shows that the usual causality considerations apply if the mass, damping, and stiffness matrices are all positive-definite. An extended class of Kramers-Kronig relations esists, and the general relations in this class are derived which relate the real and imaginary parts of the transfer function.
Show PACS
43.40.Sk Inverse problems in structural acoustics and vibration
FREE

The invariants of the time-reversal operator for asymmetric response matrices

Peter Simko and Jafar Saniie

POMA Volume 5, pp. 065002 (January 2009); (19 pages)

Online Publication Date: January 29, 2009

Full Text: | Download PDF

Show Abstract
The eigenmodes of the time reversal operator are studied for a single rigid cylinder with elliptical cross-section leading to an asymmetric inter-element response matrix in reflection measurement mode. The elliptical cylinder is of considerable interest in scattering problems and it encompasses within the limit both the circular cross-section case and the strip. Variable cylinder properties will include cross-sectional area, eccentricity and angle of inclination of the semi-major axis with respect to the axis of symmetry of a probing transducer array. Approximations of the exact solutions determining the far-field response using a modal expansion with scattering coefficients computed via Mathieu functions will be discussed. Analysis of simulated results will indicate that for scatterers near the Rayleigh limit it is possible to characterize the aspect ratio of the target using subarray methods.
Show PACS
43.40.Cw Vibrations of strings, rods, and beams
43.60.Fg Acoustic array systems and processing, beam-forming
Page 1 of 2 Pages Next Page | Jump to Page
Close

Home Publications Meetings Contact ASA Site Map Back to Top

Copyright © Acoustical Society of America

close