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Journal of the Acoustical Society of America

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Oct 2009

Volume 126, Issue 4, pp. 1657-2316

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On the sign of the adaptive passive fathometer impulse response

James Traer, Peter Gerstoft, H. C. Song, and William S. Hodgkiss

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1657-1658 (2009); (2 pages) | Cited 2 times

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Harrison [J. Acoust. Soc. Am. 125, 3511–3513 (2009)] presented a mathematical explanation for a sign-inversion induced to the passive fathometer response by minimum variance distortionless response (MVDR) beamforming. Here a concise mathematical formulation is offered, which decomposes the cross-spectral density matrix into coherent and incoherent components and allows the matrix inversion to be obtained exactly by eigendecomposition. This shows that, in the region containing the bottom reflection, the MVDR fathometer response is identical to that obtained with conventional processing multiplied by a negative factor.
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43.30.Pc Ocean parameter estimation by acoustical methods; remote sensing; imaging, inversion, acoustic tomography
43.30.Re Signal coherence or fluctuation due to sound propagation/scattering in the ocean
43.30.Wi Passive sonar systems and algorithms, matched field processing in underwater acoustics
43.30.Nb Noise in water; generation mechanisms and characteristics of the field

Time domain visualization using acoustic holography implemented by temporal and spatial complex envelope

Choon-Su Park and Yang-Hann Kim

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1659-1662 (2009); (4 pages) | Cited 1 time

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Spatial envelope was proposed to show the location of acoustic sources and overall radiation pattern by the authors [ C.-S. Park and Y.-H. Kim, J. Acoust. Soc. Am. 125, 206–211 (2009) ]. The envelope can provide sufficient information on where the sources are and how the energy propagates into space. This concept is certainly useful for time domain acoustic holography since one can utilize not only spatial envelope to envisage what one needs to know but also temporal envelope to reduce the number of data. A holographic process to obtain spatial envelope is therefore introduced and verified, and how much one can reduce the processing time by implementing envelopes is compared with the conventional holography.
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43.60.Sx Acoustic holography
43.60.Ac Theory of acoustic signal processing
43.60.Jn Source localization and parameter estimation
43.60.Gk Space-time signal processing, other than matched field processing

Octave-shifted pitch matching in nonword imitations: The effects of lexical stress and speech sound disorder

Beate Peter, Tara Larkin, and Carol Stoel-Gammon

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1663-1666 (2009); (4 pages)

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Perceptual similarities of musical tones separated by octave intervals are known as octave equivalence (OE). Peter et al. [(2008). Proceedings of the Fourth Conference on Speech Prosody, edited S. Maduerira, C. Reis, and P. Barbosa, Luso-Brazilian Association of Speech Sciences, Campinas, pp. 731–734 ] found evidence of octave-shifted pitch matching (OSPM) in children during verbal imitation tasks, implying OE in speech tokens. This study evaluated the role of lexical stress and speech sound disorder (SSD) in OSPM. Eleven children with SSD and 11 controls imitated low-pitched nonwords. Stimulus/response f0 ratios were computed. OSPM was expressed preferentially in stressed vowels. SSD was associated with reduced expression of OSPM in unstressed vowels only. Results are consistent with the psycholinguistic prominence of lexical stress and prosodic deficits in SSD.
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43.66.Hg Pitch
43.70.Fq Acoustical correlates of phonetic segments and suprasegmental properties: stress, timing, and intonation
43.70.Dn Disordered speech
43.66.Lj Perceptual effects of sound

Acoustic standing wave suppression using randomized phase-shift-keying excitations

Sai Chun Tang and Gregory T. Clement

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1667-1670 (2009); (4 pages) | Cited 1 time

Online Publication Date: 06 Oct 2009

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Recent papers have demonstrated that acoustic standing waves can be inhibited by frequency-modulated spread-spectrum excitation. An alternative method is studied here that is designed to be more practical for implementation in phased arrays. The method operates using phase-shift-keying (PSK), which introduces phase shifts into the driving signal to break wave symmetry. Sequential and random binary-PSK (BPSK) and quadrature-PSK (QPSK) excitations are studied in water, using a carrier frequency of 250 kHz and a time segment of 10 cycles. The resulting acoustic field is measured with a transducer inside a plastic-walled chamber and compared with continuous wave excitation. Results indicate that both the random BPSK and QPSK methods can reduce time-averaged spatial intensity variation caused by standing waves by approximately six times.
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43.80.Sh Medical use of ultrasonics for tissue modification (permanent and temporary)
43.20.Ks Standing waves, resonance, normal modes
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Comments on “The Science and Applications of Acoustics” [Springer-Verlag (2000, 2006)]

Kenneth A. Cunefare

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1671-1680 (2009); (10 pages)

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Raichel’s “The Science and Applications of Acoustics” (Springer-Verlag, Berlin, 2000) has extensive material that appears to have been extracted from four other texts without proper attribution. The material so used extends to figures, detailed structure of entire sections and developments, and phrasing of individual passages. While in some instances like material between the texts has been paraphrased to some extent, in others it appears almost unaltered.
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43.10.Hj Books and book reviews
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Propagation of nonlinear acoustic plane waves in an elastic gas-filled tube

Michal Bednarik and Milan Cervenka

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1681-1689 (2009); (9 pages)

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This paper deals with modeling of nonlinear plane acoustic waves propagating through an elastic tube filled with thermoviscous gas. A description of the interactions between gas and an elastic tube wall is carried out by the continuity equation of a wall velocity. Simplification on the basis of the local reaction assumption enables to model an acoustic treatment on the tube wall by using a wall impedance. Because there are considerable losses due to wall friction, the influences of the acoustic boundary layer were also considered. Using certain assumptions a special form of the Burgers equation was derived which enables to describe the propagation of nonlinear waves in the elastic tube. This model equation takes into account nonlinear, dissipative, and dispersion effects which compete each other. Characteristic lengths of the supposed effects and numerical results with respect to the source frequency were used for a qualitative analysis of the model equation. Applicability of this model equation was demonstrated by series of measurements. By application of the long-wave approximation the Korteweg–de Vries–Burgers and Kuramoto–Sivashinsky equations were derived from the modified Burgers equation.
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43.25.Cb Macrosonic propagation, finite amplitude sound; shock waves
43.20.Mv Waveguides, wave propagation in tubes and ducts

Numerical investigation of nonlinear propagation distortion effects in helicopter rotor noise

Penelope Menounou and Panagiotis A. Vitsas

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1690-1699 (2009); (10 pages) | Cited 1 time

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The effect of nonlinear propagation distortion on helicopter rotor noise is presented based on measured data for low-speed descent and numerical calculations that predict the noise level away from the helicopter with and without nonlinear effects. It is shown that for some frequency bands the difference between linear and nonlinear calculations can be as high as 7 dB. Blade vortex interaction (BVI) noise, the dominant noise contributor during descent, is mainly examined. It is shown that advancing side BVI noise is affected by nonlinear distortion, while retreating side BVI noise is not. Based on signal characteristics at source, two quantities are derived. The first quantity (termed polarity) is based on the pressure gradient of the source signal and can be used to determine whether a BVI signal will evolve as an advancing or a retreating side signal. The second quantity (termed weighted rise time) is a measure of the impulsiveness of the BVI signal and can be used to determine at which frequency nonlinear effects start to appear. Finally, polarity and weighted rise time are shown to be applicable in cases of BVI noise generated from different blade tips, as well as in cases of non-BVI noise.
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43.25.Cb Macrosonic propagation, finite amplitude sound; shock waves
43.28.Bj Mechanisms affecting sound propagation in air, sound speed in the air
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A three dimensional parabolic equation method for sound propagation in moving inhomogeneous media

Rui Cheng, Philip J. Morris, and Kenneth S. Brentner

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1700-1710 (2009); (11 pages)

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In this paper, a formulation of the Helmholtz equation for three dimensional sound propagation in a moving inhomogeneous medium in cylindrical coordinates is derived. Based on this formulation, a three dimensional parabolic equation (PE) is constructed. This PE can be used to model sound propagation in an inhomogeneous arbitrary moving medium. The method is used here to simulate three dimensional outdoor sound propagation above a rigid flat ground surface. The numerical results for two simple wind cases are presented and compared with analytical results to validate the methodology. Examples of propagation problems with more complicated wind are then included to demonstrate the importance of including the wind velocity directly in the PE method.
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43.28.Js Numerical models for outdoor propagation
43.28.Fp Outdoor sound propagation through a stationary atmosphere, meteorological factors
43.28.Gq Outdoor sound propagation and scattering in a turbulent atmosphere, and in non-uniform flow fields
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Radiative transfer theory applied to ocean bottom modeling

Jorge E. Quijano and Lisa M. Zurk

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1711-1723 (2009); (13 pages)

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Research on the propagation of acoustic waves in the ocean bottom sediment is of interest for active sonar applications such as target detection and remote sensing. The interaction of acoustic energy with the sea floor sublayers is usually modeled with techniques based on the full solution of the wave equation, which sometimes leads to mathematically intractable problems. An alternative way to model wave propagation in layered media containing random scatterers is the radiative transfer (RT) formulation, which is a well established technique in the electromagnetics community and is based on the principle of conservation of energy. In this paper, the RT equation is used to model the backscattering of acoustic energy from a layered elastic bottom sediment containing distributions of independent scatterers due to a constant single frequency excitation in the water column. It is shown that the RT formulation provides insight into the physical phenomena of scattering and conversion of energy between waves of different polarizations.
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43.30.Ft Volume scattering
43.20.Bi Mathematical theory of wave propagation
43.20.Fn Scattering of acoustic waves
43.30.Vh Active sonar systems

Riverbed sediment classification using multi-beam echo-sounder backscatter data

AliReza Amiri-Simkooei, Mirjam Snellen, and Dick G. Simons

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1724-1738 (2009); (15 pages)

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A method has recently been developed that employs multi-beam echo-sounder backscatter data to both obtain the number of sediment classes and discriminate between them by applying the Bayes decision rule to multiple hypotheses [ Simons and Snellen, Appl. Acoust. 70, 1258–1268 (2009) ]. In deep water, the number of scatter pixels within the beam footprint is large enough to ensure Gaussian distributions for the backscatter strengths and to increase the discriminative power between acoustic classes. In very shallow water (<10 m), however, this number is too small. This paper presents an extension of this high-frequency methodology for these environments, together with a demonstration of its performance using backscatter data from the river Waal, The Netherlands. The objective of this work is threefold. (i) Increasing the discriminating power of the classification method: high-resolution bathymetry data allow precise bottom slope corrections for obtaining the true incident angle, and the high-resolution backscatter data reduce the statistical fluctuations via an averaging procedure. (ii) Performing a correlation analysis: the dependence of acoustic backscatter classification on sediment physical properties is verified by observing a significant correlation of 0.75 (and a disattenuated correlation of 0.90) between the classification results and sediment mean grain size. (iii) Enhancing the statistical description of the backscatter intensities: angular evolution of the K-distribution shape parameter indicates that the riverbed is a rough surface, in agreement with the results of the core analysis.
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43.30.Hw Rough interface scattering
43.30.Xm Underwater measurement and calibration instrumentation and procedures
43.30.Ma Acoustics of sediments; ice covers, viscoelastic media; seismic underwater acoustics
43.30.Vh Active sonar systems

On the consideration of motion effects in the computation of impulse response for underwater acoustics inversion

Nicolas F. Josso, Cornel Ioana, Jérôme I. Mars, Cédric Gervaise, and Yann Stéphan

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1739-1751 (2009); (13 pages) | Cited 3 times

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The estimation of the impulse response (IR) of a propagation channel may be of great interest for a large number of underwater applications: underwater communications, sonar detection and localization, marine mammal monitoring, etc. It quantifies the distortions of the transmitted signal in the underwater channel and enables geoacoustic inversion. The propagating signal is usually subject to additional and undesirable distortions due to the motion of the transmitter-channel-receiver configuration. This paper shows the effects of the motion while estimating the IR by matched filtering between the transmitted and the received signals. A methodology to compare IR estimation with and without motion is presented. Based on this comparison, a method for motion effect compensation is proposed in order to reduce motion-induced distortions. The proposed methodology is applied to real data sets collected in 2007 by the Service Hydrographique et Océanographique de la Marine in a shallow water environment, proving its interest for motion effect analysis. Motion compensated estimation of IRs is computed from sources transmitting broadband linear frequency modulations moving at up to 12 knots in the shallow water environment of the Malta plateau, South of Sicilia.
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43.30.Pc Ocean parameter estimation by acoustical methods; remote sensing; imaging, inversion, acoustic tomography
43.60.Mn Adaptive processing
43.60.Pt Signal processing techniques for acoustic inverse problems
43.30.Cq Ray propagation of sound in water

Acoustic mode radiation from the termination of a truncated nonlinear internal gravity wave duct in a shallow ocean area

Ying-Tsong Lin, Timothy F. Duda, and James F. Lynch

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1752-1765 (2009); (14 pages) | Cited 2 times

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Horizontal ducting of sound between short-wavelength nonlinear internal gravity waves in coastal environments has been reported in many theoretical and experimental studies. Important consequences arising at the open end of an internal wave duct (the termination) are examined in this paper with three-dimensional normal mode theory and parabolic approximation modeling. For an acoustic source located in such a duct and sufficiently far from the termination, some of the propagating sound may exit the duct by penetrating the waves at high grazing angles, but a fair amount of the sound energy is still trapped in the duct and propagates toward the termination. Analysis here shows that the across-duct sound energy distribution at the termination is unique for each acoustic vertical mode, and as a result the sound radiating from the termination of the duct forms horizontal beams that are different for each mode. In addition to narrowband analysis, a broadband simulation is made for water depths of order 80 m and propagation distances of 24 km. Situations occur with one or more modes absent in the radiated field and with mode multipath in the impulse response. These are both consistent with field observations.
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43.30.Re Signal coherence or fluctuation due to sound propagation/scattering in the ocean
43.20.Bi Mathematical theory of wave propagation
43.20.Mv Waveguides, wave propagation in tubes and ducts
43.30.Bp Normal mode propagation of sound in water
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Wave scattering from encapsulated microbubbles subject to high-frequency ultrasound: Contribution of higher-order scattering modes

Jiusheng Chen, Kendall S. Hunter, and Robin Shandas

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1766-1775 (2009); (10 pages) | Cited 2 times

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The theoretical understanding of encapsulated microbubble response to high-frequency ultrasound (HFUS) excitation is still limited although some novel experimental HFUS contrast imaging techniques have been well developed. In this paper, the higher-order modal (HOM) contributions to the scattered field are studied for such microbubbles driven by 1–100 MHz ultrasound. An exact solution of all small-amplitude vibrational modes of a single encapsulated microbubble in water is given by the wave scattering theory (WST) method and compared to results obtained from Church’s Rayleigh–Plesset-like model for the small-amplitude radial oscillation of a microbubble in an incompressible fluid. From numerical results, we show that the HOM field contribution is significant for scattering properties from individual Nycomed microbubbles with normalized frequency ≥ 0.2. It is also shown that the multiple scattering is strengthened for monodispersed Definity® microbubbles of 3 μm radius at frequencies >40 MHz. However, comparisons between the authors' analyses and known experimental data for polydispersed Definity® microbubbles indicate that the HOM contributions are insignificant in attenuation estimation at frequencies <50 MHz. In conclusion, the WST model analysis suggests that HOM scattering is an important consideration for single bubbles but may be less critical in the modeling of polydispersed Definity® bubbles at high frequencies.
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43.35.Bf Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions, and emulsions
43.35.Ei Acoustic cavitation in liquids
43.20.Fn Scattering of acoustic waves
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Sound radiation quantities arising from a resilient circular radiator

Ronald M. Aarts and Augustus J. E. M. Janssen

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1776-1787 (2009); (12 pages) | Cited 3 times

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Power series expansions in ka are derived for the pressure at the edge of a radiator, the reaction force on the radiator, and the total radiated power arising from a harmonically excited, resilient, flat, circular radiator of radius a in an infinite baffle. The velocity profiles on the radiator are either Stenzel functions (1−(σ/a)2)n, with σ the radial coordinate on the radiator, or linear combinations of Zernike functions Pn(2(σ/a)2−1), with Pn the Legendre polynomial of degree n. Both sets of functions give rise, via King’s integral for the pressure, to integrals for the quantities of interest involving the product of two Bessel functions. These integrals have a power series expansion and allow an expression in terms of Bessel functions of the first kind and Struve functions. Consequently, many of the results in [ M. Greenspan, J. Acoust. Soc. Am. 65, 608–621 (1979) ] are generalized and treated in a unified manner. A foreseen application is for loudspeakers. The relation between the radiated power in the near-field on one hand and in the far field on the other is highlighted.
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43.38.Ar Transducing principles, materials, and structures: general
43.20.Bi Mathematical theory of wave propagation
43.20.Px Transient radiation and scattering
43.40.At Experimental and theoretical studies of vibrating systems

Hybrid method for determining the parameters of condenser microphones from measured membrane velocities and numerical calculations

Salvador Barrera-Figueroa, Knud Rasmussen, and Finn Jacobsen

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1788-1795 (2009); (8 pages) | Cited 1 time

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Typically, numerical calculations of the pressure, free-field, and random-incidence response of a condenser microphone are carried out on the basis of an assumed displacement distribution of the diaphragm of the microphone; the conventional assumption is that the displacement follows a Bessel function. This assumption is probably valid at frequencies below the resonance frequency. However, at higher frequencies the movement of the membrane is heavily coupled with the damping of the air film between membrane and backplate and with resonances in the back chamber of the microphone. A solution to this problem is to measure the velocity distribution of the membrane by means of a non-contact method, such as laser vibrometry. The measured velocity distribution can be used together with a numerical formulation such as the boundary element method for estimating the microphone response and other parameters, e.g., the acoustic center. In this work, such a hybrid method is presented and examined. The velocity distributions of a number of condenser microphones have been determined using a laser vibrometer, and these measured velocity distributions have been used for estimating microphone responses and other parameters. The agreement with experimental data is generally good. The method can be used as an alternative for validating the parameters of the microphones determined by classical calibration techniques.
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43.38.Kb Microphones and their calibration
43.38.Bs Electrostatic transducers

Channel separation of crosstalk cancellation systems with mismatched and misaligned sound sources

Xiaojun Qiu, Bruno Masiero, and Michael Vorländer

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1796-1806 (2009); (11 pages)

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Loudspeakers in virtual sound imaging systems are usually modeled as omnidirectional monopole sources. These models are, however, only an approximation for the low frequency range. This paper presents an analytical model of crosstalk cancellation systems in a free field which takes into account the scattering and spatial characteristics of the sound sources. Based on the proposed model, the effects caused by the spatial characteristics of the sound source and its misalignments on the performance of the crosstalk cancellation system are studied numerically. It is found that although the factors such as the directivity of the sound sources and the distance between the sound sources and receiver affect the performance of the system to a certain extent, the channel separation of the crosstalk cancellation system, however, is most sensitive to the misalignment of the subtended angle of the sound sources. Therefore, if highly accurate binaural cues are required in practical applications, the type and characteristics of the playback sound sources, their locations, and orientations all should be considered carefully.
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43.38.Md Sound recording and reproducing systems, general concepts
43.38.Vk Stereophonic reproduction
43.66.Pn Binaural hearing
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Steady state and time-dependent energy equilibration in two-dimensional random elastic slabs

Yanyi Wan, Ying Wu, and Zhao-Qing Zhang

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1807-1816 (2009); (10 pages)

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The static and dynamic transport properties of elastic wave propagation through two-dimensional random slabs without internal reflection were studied at two different scattering parameters: one for Rayleigh scattering and the other for Rayleigh–Gans scattering. The spatial distribution and temporal evolution of shear (s−) and compressional (p−) wave energy densities inside the slabs were calculated by solving the radiative transfer equation and the generalized diffusion equation (GDE). The comparison of their results can determine the region of validity of the GDE. The process of energy equilibration between the two wave modes was demonstrated explicitly as well as the process of diffusion. The depth inside a slab that is needed to reach energy equilibration or diffusive behavior is found to be dependent on source polarization. The results also show that the bulk equilibration ratio can be found inside a sample only when the sample is sufficiently thick. Deviations of the equilibration ratio from its bulk value are found near the output surface due to the absence of in-flow energy flux. The behavior of the deviations is sensitive to the scattering parameter but independent of source polarization.
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43.40.Fz Acoustic scattering by elastic structures
43.40.Hb Random vibration
43.20.Fn Scattering of acoustic waves

On the correlation of non-isotropically distributed ballistic scalar diffuse waves

Richard Weaver, Berenice Froment, and Michel Campillo

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1817-1826 (2009); (10 pages) | Cited 8 times

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Theorems indicating that a fully equipartitioned random wave field will have correlations equivalent to the Green’s function that would be obtained in an active measurement are now legion. Studies with seismic waves, ocean acoustics, and laboratory ultrasound have confirmed them. So motivated, seismologists have evaluated apparent seismic travel times in correlations of ambient seismic noise and tomographically constructed impressive maps of seismic wave velocity. Inasmuch as the random seismic waves used in these evaluations are usually not fully equipartitioned, it seems right to ask why it works so well, or even if the results are trustworthy. The error, in apparent travel time, due to non-isotropic specific intensity is evaluated here in a limit of large receiver-receiver separation and for the case in which the source of the noise is in the far field of both receivers. It is shown that the effect is small, even for cases in which one might have considered the anisotropy to be significant, and even for station pairs separated by as little as one or two wavelengths. A formula is derived that permits estimations of error and corrections to apparent travel time. It is successfully compared to errors seen in synthetic waveforms.
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43.40.Ph Seismology and geophysical prospecting; seismographs
43.50.Yw Instrumentation and techniques for noise measurement and analysis
43.60.Cg Statistical properties of signals and noise

Estimating sound power radiated from rectangular baffled panels using a radiation factor

Dan Palumbo

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1827-1837 (2009); (11 pages)

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A method is introduced which is shown to predict radiated sound power from rectangular baffled panels. The method employs a filtered wavenumber transform to extract the power in the supersonic wavenumbers on the panel and a radiation factor to scale the supersonic power to match the actual radiated sound power. Although empirically derived, the radiation factor is shown to be related to the radiation efficiency of an infinite panel. The radiation factor is simple, depending only on the ratio of the wavenumbers of the panel to the radiation medium, and the method is straightforward to use, requiring only the panel normal velocities. The computation is efficient, as much as two orders of magnitude faster than a Rayleigh integration, thus providing a means of combining sound power predictions with finite element optimizations. A formula is derived which predicts the lowest frequency for which the method is valid as a function of the bin width of the wavenumber transform. The radiation factor method is shown to produce radiated sound power estimates which favorably compare to estimates derived from intensity measurements of physical test specimens and to Rayleigh integral estimates computed using both simulated and measured velocities.
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43.40.Yq Instrumentation and techniques for tests and measurement relating to shock and vibration, including vibration pickups, indicators, and generators, mechanical impedance
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A comparative analysis of acoustic energy models for churches

Umberto Berardi, Ettore Cirillo, and Francesco Martellotta

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1838-1849 (2009); (12 pages) | Cited 1 time

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Different models to improve prediction of energy-based acoustic parameters in churches have been proposed by different researchers [ E. Cirillo and F. Martellotta, J. Acoust. Soc. Am. 118, 232–248 (2005) ; T. Zamarreño et al., J. Acoust. Soc. Am. 121, 234–250 (2006) ]. They all suggested variations to the “revised” theory proposed by Barron and Lee [ J. Acoust. Soc. Am. 84, 618–628 (1988) ], starting from experimental observations. The present paper compares these models and attempts to generalize their use taking advantage of the measurements carried out in 24 Italian churches differing in style, typology, and location. The whole sample of churches was divided into two groups. The first was used to fine-tune existing models, with particular reference to the “μ model,” which was originally tested only on Mudejar-Gothic churches. Correlations between model parameters and major typological and architectural factors were found, leading to a classification that greatly simplifies parameter choice. Finally, the reliability of each model was verified on the rest of the sample, showing that acoustic parameters can be predicted with reasonable accuracy provided that one of the specifically modified theories is used. The results show that the model requiring more input parameters performs slightly better than the other which, conversely, is simpler to apply.
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43.55.Br Room acoustics: theory and experiment; reverberation, normal modes, diffusion, transient and steady-state response
43.55.Gx Studies of existing auditoria and enclosures

Effect of boundary slip on the acoustical properties of microfibrous materials

Olga Umnova, David Tsiklauri, and Rodolfo Venegas

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1850-1861 (2009); (12 pages)

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A variety of new porous materials with unusually small pores have been manufactured in the past decades. To predict their acoustical properties, the conventional models need to be modified. When pore size becomes comparable to the molecular mean free path of a saturating fluid, the no-slip conditions on the pore surface are no longer accurate and hence the slip effects have to be taken into account. In this paper, sound propagation in microfibrous materials is modeled analytically, approximating the geometry by a regular array of rigid parallel cylinders. It has been shown that velocity and thermal slip on a cylinder surface significantly changes the model predictions leading to lower attenuation coefficient and higher sound speed values. The influence of material porosity, fiber orientation, and size on these effects is investigated. Finite element method is used to numerically solve the oscillatory flow and heat transfer problems in a square array of cylindrical fibres. Numerical results are compared with predictions of the analytical model and the range of its validity is identified.
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43.55.Ev Sound absorption properties of materials: theory and measurement of sound absorption coefficients; acoustic impedance and admittance
43.20.Hq Velocity and attenuation of acoustic waves
43.20.Bi Mathematical theory of wave propagation

Acoustic absorption calculation in irreducible porous media: A unified computational approach

Chang-Yong Lee, Michael J. Leamy, and Jason H. Nadler

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1862-1870 (2009); (9 pages) | Cited 1 time

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A critical task in predicting and tailoring the acoustic absorption properties of porous media is the calculation of the frequency-dependent effective density and compressibility tensors, which are explicitly related to the micro-scale permeability properties. Although these two quantities exhibit strong sensitivity to physics occurring at complex micro-scale geometries, most of the existing literature focuses on employing very limited in-house and oftentimes multiple numerical analysis tools. In order to predict these parameters and acoustic absorption efficiently and conveniently, this article synthesizes multiple disparate approaches into a single unified formulation suitable for incorporation into a commercial analysis package. Numerical results computed herein for four close-packed porous media are compared to similar results available in the literature. These include simple cubic, body-centered cubic, and face-centered cubic structures, and also hexagonal close-packed, which has not appeared in the literature. Together with critical comparisons of a hybrid versus direct numerical approaches, the close agreement demonstrates the capabilities of the unified formulation to analyze and control the acoustic absorption properties at the microscopic level.
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43.55.Ev Sound absorption properties of materials: theory and measurement of sound absorption coefficients; acoustic impedance and admittance
43.20.Jr Velocity and attenuation of elastic and poroelastic waves

Predicting the sound insulation of single leaf walls: Extension of Cremer’s model

John L. Davy

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1871-1877 (2009); (7 pages) | Cited 1 time

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In his 1942 paper on the sound insulation of single leaf walls, Cremer [(1942). Akust. Z. 7, 81–104 ] made a number of approximations in order to show the general trend of sound insulation above the critical frequency. Cremer realized that these approximations limited the application of his theory to frequencies greater than twice the critical frequency. This paper removes most of Cremer’s approximations so that the revised theory can be used down to the critical frequency. The revised theory is used as a correction to the diffuse field limp panel mass law below the critical frequency by setting the nonexistent coincidence angle to 90°. The diffuse field limp panel mass law for a finite size wall is derived without recourse to a limiting angle by following the average diffuse field single sided radiation efficiency approach. The shear wave correction derived by Heckl and Donner [(1985). Rundfunktech Mitt. 29, 287–291] is applied to the revised theory in order to cover the case of thicker walls. The revised theory predicts the general trend of the experimental data, although the agreement is usually worse at low frequencies and depends on the value of damping loss factor used in the region of and above the critical frequency.
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43.55.Rg Sound transmission through walls and through ducts: theory and measurement
43.55.Ti Sound-isolating structures, values of transmission coefficients
43.40.Yq Instrumentation and techniques for tests and measurement relating to shock and vibration, including vibration pickups, indicators, and generators, mechanical impedance
43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods
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Relation between derived-band auditory brainstem response latencies and behavioral frequency selectivity

Olaf Strelcyk, Dimitrios Christoforidis, and Torsten Dau

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1878-1888 (2009); (11 pages)

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Derived-band click-evoked auditory brainstem responses (ABRs) were obtained for normal-hearing (NH) and sensorineurally hearing-impaired (HI) listeners. The latencies extracted from these responses, as a function of derived-band center frequency and click level, served as objective estimates of cochlear response times. For the same listeners, auditory-filter bandwidths at 2 kHz were estimated using a behavioral notched-noise masking paradigm. Generally, shorter derived-band latencies were observed for the HI than for the NH listeners. Only at low click sensation levels, prolonged latencies were obtained for some of the HI listeners. The behavioral auditory-filter bandwidths accounted for the across-listener variability in the ABR latencies: Cochlear response time decreased with increasing filter bandwidth, consistent with linear-system theory. The results link cochlear response time and frequency selectivity in human listeners and offer a window to better understand how hearing impairment affects the spatiotemporal cochlear response pattern.
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43.64.Ri Evoked responses to sounds
43.64.Kc Cochlear mechanics
43.66.Sr Deafness, audiometry, aging effects
43.66.Dc Masking
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Diotic and dichotic detection with reproducible chimeric stimuli

Sean A. Davidson, Robert H. Gilkey, H. Steven Colburn, and Laurel H. Carney

J. Acoust. Soc. Am. Volume 126, Issue 4, pp. 1889-1905 (2009); (17 pages) | Cited 3 times

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Subject responses were measured for individual narrow-band reproducible stimuli in a low-frequency tone-in-noise detection task. Both N0S0 and N0Sπ conditions were examined. The goal of the experiment was to determine the relative importance of envelope and fine-structure cues. Therefore, chimeric stimuli were generated by recombining envelopes and fine structures from different reproducible stimuli. Detection judgments for noise-alone or tone-plus-noise stimuli that had common envelopes but different fine structures or common fine structures but different envelopes were compared. The results showed similar patterns of responses to stimuli that shared envelopes, indicating the importance of envelope cues; however, fine-structure cues were also shown to be important. The relative weight assigned to envelope and fine-structure cues varied across subjects and across interaural conditions. The results also indicated that envelope and fine-structure information are not processed independently. Implications for monaural and binaural models of masking are discussed.
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43.66.Dc Masking
43.66.Rq Dichotic listening
43.66.Ba Models and theories of auditory processes
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