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Journal of the Acoustical Society of America

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Dec 2012

Volume 132, Issue 6, pp. EL443-4101

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Children weight dynamic spectral structure more than adults: Evidence from equivalent signals

Joanna H. Lowenstein, Susan Nittrouer, and Eric Tarr

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. EL443-EL449 (2012); (7 pages)

Online Publication Date: 08 Nov 2012

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Earlier work using sine-wave and noise-vocoded signals suggests that dynamic spectral structure plays a greater role in speech recognition for children than adults [Nittrouer and Lowenstein. (2010). J. Acoust. Soc. Am. 127, 1624–1635], but questions arise concerning whether outcomes can be compared because sine waves and wide noise bands are different in nature. The current study addressed that question using narrow noise bands for both signals, and applying a difference ratio to index the contribution made by dynamic spectral structure. Results replicated earlier findings, supporting the idea that dynamic spectral structure plays a critical role in speech recognition, especially for children.
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43.71.Ft Development of speech perception
43.71.An Models and theories of speech perception
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Release from masking of low-frequency complex tones by high-frequency complex tone cue bands

Angela Josupeit, Volker Hohmann, and Steven van de Par

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. EL450-EL455 (2012); (6 pages)

Online Publication Date: 08 Nov 2012

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This study investigated the influence of high-frequency cue bands on the detection and discrimination of low-frequency target bands presented in a 3000-Hz low-pass noise masker. Target and cue bands were complex tones with 80-Hz spacing. The cue band consisted of 60 components starting at 4000 Hz; targets consisted of four components starting at different frequencies (500, 700, 1000, 1200, and 1500 Hz). Targets were presented with different durations within the 500-ms masker; target and cue bands had a common on- and offset. Presentation of the high-frequency complex tone significantly enhanced both the discrimination and detection thresholds by 2–3 dB.
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43.66.Dc Masking
43.66.Hg Pitch
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Fractional lower order moment based adaptive algorithms for active noise control of impulsive noise sources

Muhammad Tahir Akhtar

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. EL456-EL462 (2012); (7 pages)

Online Publication Date: 09 Nov 2012

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This letter deals with active noise control (ANC) for impulsive noise sources being modeled using non-Gaussian stable process. The filtered-x least mean square algorithm is based on minimization of the variance of the error signal and becomes unstable for impulsive noise. The filtered-x least mean p-power algorithm—based on minimizing the fractional lower order moment—gives a robust performance for impulsive ANC; however, its convergence speed is very slow. This letter proposes modifying and employing a generalized normalized LMP algorithm for impulsive ANC. Extensive simulations are carried out which demonstrate the effectiveness of the proposed algorithm.
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43.50.Ki Active noise control
43.50.Pn Impulse noise and noise due to impact
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Influence of cortical endplate on speed of sound in bovine femoral trabecular bone in vitro

Kyo Seung Hwang and Kang Il Lee

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. EL463-EL469 (2012); (7 pages)

Online Publication Date: 26 Nov 2012

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Speed of sound (SOS) was measured in 14 bovine femoral trabecular bone samples with and without the cortical endplates with various thicknesses of 1.00, 1.31, 1.47, 1.75, and 2.00 mm. The presence of the cortical endplates resulted in an increase in the mean SOS of 16 m/s (+0.9%) to 91 m/s (+5.3%). The mean SOS measured in the samples with and without the cortical endplates exhibited similar significant correlations with apparent bone density (r = 0.86–0.91). All the SOS measurements were also found to be highly correlated with each other (r = 0.89–0.99).
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43.80.Cs Acoustical characteristics of biological media: molecular species, cellular level tissues
43.80.Qf Medical diagnosis with acoustics
43.80.Vj Acoustical medical instrumentation and measurement techniques
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Chirp resonance spectroscopy of single lipid-coated microbubbles using an “acoustical camera”

G. Renaud, J. G. Bosch, A. F. W. van der Steen, and N. de Jong

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. EL470-EL475 (2012); (6 pages) | Cited 1 time

Online Publication Date: 26 Nov 2012

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An acoustical method was developed to study the resonance of single lipid-coated microbubbles. The response of 127 SonoVue microbubbles to a swept sine excitation between 0.5 and 5.5 MHz with a peak acoustic pressure amplitude of 70 kPa was measured by means of a 25 MHz probing wave. The relative amplitude modulation in the signal scattered in response to the probing wave is approximately equal to the radial strain induced by the swept sine excitation. An average damping coefficient of 0.33 and an average resonance frequency of 2.5 MHz were measured. Microbubbles experienced an average peak radial strain of 20%.
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43.25.Yw Nonlinear acoustics of bubbly liquids
43.25.Zx Measurement methods and instrumentation for nonlinear acoustics
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Cylindrical transducer for producing an acoustic spiral wave for underwater navigation (L)

David A. Brown, Boris Aronov, and Corey Bachand

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. 3611-3613 (2012); (3 pages) | Cited 1 time

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A cylindrical piezoceramic transducer using two orthogonal dipoles driven in phase quadrature to create an acoustic spiral wave, having constant amplitude and phase that varies linearly with azimuthal angle, is considered as a source for an underwater acoustic navigation system. Comparison of the spiral-wave signal with an omnidirectional reference signal having a constant phase originating from the same or co-located source provides a means for an underwater vehicle to determine its bearing angle relative to the signaling beacon [B. Hefner and B. Dzikowicz, J. Acoust. Soc. Am. 129(6), 3630–3639 (2011)]. An alternative proof-of-principle transducer along with experimental results including transmit frequency response, directional factors, and computed versus measured bearing angle are presented.
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43.38.Ar Transducing principles, materials, and structures: general
43.30.Yj Transducers and transducer arrays for underwater sound; transducer calibration
43.38.Fx Piezoelectric and ferroelectric transducers
43.30.Tg Navigational instruments using underwater sound

Acoustic identification of buried underwater unexploded ordnance using a numerically trained classifier (L)

Joseph A. Bucaro, Zachary J. Waters, Brian H. Houston, Harry J. Simpson, Angie Sarkissian, Saikat Dey, and Timothy J. Yoder

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. 3614-3617 (2012); (4 pages)

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Using a finite element-based structural acoustics code, simulations were carried out for the acoustic scattering from an unexploded ordnance rocket buried in the sediment under 3 m of water. The simulation treated 90 rocket burial angles in steps of 2°. The simulations were used to train a generative relevance vector machine (RVM) algorithm for identifying rockets buried at unknown angles in an actual water/sediment environment. The trained RVM algorithm was successfully tested on scattering measurements made in a sediment pool facility for six buried targets including the rocket at 90°, 120°, and 150°, a boulder, a cinderblock, and a cinderblock rolled 45° about its long axis.
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43.60.Lq Acoustic imaging, displays, pattern recognition, feature extraction
43.20.Fn Scattering of acoustic waves
43.60.Gk Space-time signal processing, other than matched field processing

Ultrasonic whistles of killer whales (Orcinus orca) recorded in the North Pacific (L)

Olga A. Filatova, John K. B. Ford, Craig O. Matkin, Lance G. Barrett-Lennard, Alexander M. Burdin, and Erich Hoyt

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. 3618-3621 (2012); (4 pages)

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Ultrasonic whistles were previously found in North Atlantic killer whales and were suggested to occur in eastern North Pacific killer whales based on the data from autonomous recorders. In this study ultrasonic whistles were found in the recordings from two encounters with the eastern North Pacific offshore ecotype killer whales and one encounter with the western North Pacific killer whales of unknown ecotype. All ultrasonic whistles were highly stereotyped and all but two had downsweep contours. These results demonstrate that specific sound categories can be shared by killer whales from different ocean basins.
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43.80.Ka Sound production by animals: mechanisms, characteristics, populations, biosonar
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Large scale modulation of high frequency acoustic waves in periodic porous media

Claude Boutin, Antoine Rallu, and Stephane Hans

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. 3622-3636 (2012); (15 pages) | Cited 1 time

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This paper deals with the description of the modulation at large scale of high frequency acoustic waves in gas saturated periodic porous media. High frequencies mean local dynamics at the pore scale and therefore absence of scale separation in the usual sense of homogenization. However, although the pressure is spatially varying in the pores (according to periodic eigenmodes), the mode amplitude can present a large scale modulation, thereby introducing another type of scale separation to which the asymptotic multi-scale procedure applies. The approach is first presented on a periodic network of inter-connected Helmholtz resonators. The equations governing the modulations carried by periodic eigenmodes, at frequencies close to their eigenfrequency, are derived. The number of cells on which the carrying periodic mode is defined is therefore a parameter of the modeling. In a second part, the asymptotic approach is developed for periodic porous media saturated by a perfect gas. Using the “multicells” periodic condition, one obtains the family of equations governing the amplitude modulation at large scale of high frequency waves. The significant difference between modulations of simple and multiple mode are evidenced and discussed. The features of the modulation (anisotropy, width of frequency band) are also analyzed.
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43.20.Jr Velocity and attenuation of elastic and poroelastic waves
43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
43.20.Bi Mathematical theory of wave propagation
43.20.Fn Scattering of acoustic waves

Sound radiation from a flanged inclined duct

Alan McAlpine, Alex P. Daymond-King, and Andrew J. Kempton

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. 3637-3646 (2012); (10 pages)

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A simple method to calculate sound radiation from a flanged inclined duct is presented. An inclined annular duct is terminated by a rigid vertical plane. The duct termination is representative of a scarfed exit. The concept of a scarfed duct has been examined in turbofan aero-engines as a means to, potentially, shield a portion of the radiated sound from being transmitted directly to the ground. The sound field inside the annular duct is expressed in terms of spinning modes. Exterior to the duct, the radiated sound field owing to each mode can be expressed in terms of its directivity pattern, which is found by evaluating an appropriate form of Rayleigh's integral. The asymmetry is shown to affect the amplitude of the principal lobe of the directivity pattern, and to alter the proportion of the sound power radiated up or down. The methodology detailed in this article provides a simple engineering approach to investigate the sound radiation for a three-dimensional problem.
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43.20.Mv Waveguides, wave propagation in tubes and ducts
43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods
43.20.Bi Mathematical theory of wave propagation
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Energy-based method for near-real time modeling of sound field in complex urban environments

Stephanie M. Pasareanu, Marcel C. Remillieux, and Ricardo A. Burdisso

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. 3647-3658 (2012); (12 pages)

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Prediction of the sound field in large urban environments has been limited thus far by the heavy computational requirements of conventional numerical methods such as boundary element (BE) or finite-difference time-domain (FDTD) methods. Recently, a considerable amount of work has been devoted to developing energy-based methods for this application, and results have shown the potential to compete with conventional methods. However, these developments have been limited to two-dimensional (2-D) studies (along street axes), and no real description of the phenomena at issue has been exposed. Here the mathematical theory of diffusion is used to predict the sound field in 3-D complex urban environments. A 3-D diffusion equation is implemented by means of a simple finite-difference scheme and applied to two different types of urban configurations. This modeling approach is validated against FDTD and geometrical acoustic (GA) solutions, showing a good overall agreement. The role played by diffraction near buildings edges close to the source is discussed, and suggestions are made on the possibility to predict accurately the sound field in complex urban environments, in near real time simulations.
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43.28.Js Numerical models for outdoor propagation
43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods
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Probability distribution for energy of saturated broadband ocean acoustic transmission: Results from Gulf of Maine 2006 experiment

Duong Tran, Mark Andrews, and Purnima Ratilal

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. 3659-3672 (2012); (14 pages)

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The probability distribution of ocean-acoustic broadband signal energy after saturated multipath propagation is derived using coherence theory. The frequency components obtained from Fourier decomposition of a broadband signal are each assumed to be fully saturated with energy spectral density that obey the exponential distribution with 5.6 dB standard deviation and unity scintillation index. When the signal bandwidth and measurement time are larger than the correlation bandwidth and correlation time, respectively, of its energy spectral density components, the broadband signal energy obtained by integrating the energy spectral density across the signal bandwidth then follows the Gamma distribution with a standard deviation smaller than 5.6 dB and a scintillation index less than unity. The theory is verified with broadband transmissions in the Gulf of Maine shallow water waveguide in the 300 to 1200 Hz frequency range. The standard deviations of received broadband signal energies range from 2.7 to 4.6 dB for effective bandwidths up to 42 Hz, while the standard deviations of individual energy spectral density components are roughly 5.6 dB. The energy spectral density correlation bandwidths of the received broadband signals are found to be larger for signals with higher center frequencies and are roughly 10% of each center frequency.
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43.30.Bp Normal mode propagation of sound in water
43.30.Re Signal coherence or fluctuation due to sound propagation/scattering in the ocean

Deterministic forward scatter from surface gravity waves

Grant B. Deane, James C. Preisig, Chris T. Tindle, Andone Lavery, and M. Dale Stokes

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. 3673-3686 (2012); (14 pages) | Cited 1 time

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Deterministic structures in sound reflected by gravity waves, such as focused arrivals and Doppler shifts, have implications for underwater acoustics and sonar, and the performance of underwater acoustic communications systems. A stationary phase analysis of the Helmholtz–Kirchhoff scattering integral yields the trajectory of focused arrivals and their relationship to the curvature of the surface wave field. Deterministic effects along paths up to 70 water depths long are observed in shallow water measurements of surface-scattered sound at the Martha's Vineyard Coastal Observatory. The arrival time and amplitude of surface-scattered pulses are reconciled with model calculations using measurements of surface waves made with an upward-looking sonar mounted mid-way along the propagation path. The root mean square difference between the modeled and observed pulse arrival amplitude and delay, respectively, normalized by the maximum range of amplitudes and delays, is found to be 0.2 or less for the observation periods analyzed. Cross-correlation coefficients for modeled and observed pulse arrival delays varied from 0.83 to 0.16 depending on surface conditions. Cross-correlation coefficients for normalized pulse energy for the same conditions were small and varied from 0.16 to 0.06. In contrast, the modeled and observed pulse arrival delay and amplitude statistics were in good agreement.
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43.30.Hw Rough interface scattering
43.30.Re Signal coherence or fluctuation due to sound propagation/scattering in the ocean

Quantifying the effects of roughness scattering on reflection loss measurements

Marcia J. Isakson, Nicholas P. Chotiros, R. Abraham Yarbrough, and James N. Piper

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. 3687-3697 (2012); (11 pages)

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Seafloor reflection loss and roughness measurements were taken at the Experimental Validation of Acoustic Modeling Techniques experiment in 2006. The magnitude and phase of the reflection loss was measured at frequencies from 5 to 80 kHz and grazing angles from 7° to 77°. Approximately 1500 samples were taken for each angle. The roughness was measured with a laser profiler. Geoacoustic parameters such as water and sediment sound speed and density were measured concurrently. The reflection loss data were compared with three models: A flat interface elastic model based on geoacoustic measurements; a flat interface poro-elastic model based on the Biot/Stoll model; and a rough interface model based on the measured interface roughness power spectrum. The data were most consistent with the poro-elastic model including scattering. The elastic model consistently predicted values for the reflection loss which were higher than measured. The data exhibited more variability than the model due to layering and fluctuations in the propagating medium.
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43.30.Ma Acoustics of sediments; ice covers, viscoelastic media; seismic underwater acoustics
43.30.Hw Rough interface scattering

Shear wave velocity and attenuation in the upper layer of ocean bottoms from long-range acoustic field measurements

Ji-Xun Zhou and Xue-Zhen Zhang

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. 3698-3705 (2012); (8 pages)

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Several physics-based seabed geoacoustic models (including the Biot theory) predict that compressional wave attenuation α2 in sandy marine sediments approximately follows quadratic frequency dependence at low frequencies, i.e., α2 ≈ kfn  (dB/m), n = 2. A recent paper on broadband geoacoustic inversions from low frequency (LF) field measurements, made at 20 locations around the world, has indicated that the frequency exponent of the effective sound attenuation n ≈ 1.80 in a frequency band of 50–1000 Hz [Zhou et al., J. Acoust. Soc. Am. 125, 2847–2866 (2009)]. Carey and Pierce hypothesize that the discrepancy is due to the inversion models' neglect of shear wave effects [J. Acoust. Soc. Am. 124, EL271–EL277 (2008)]. The broadband geoacoustic inversions assume that the seabottom is an equivalent fluid and sound waves interact with the bottom at small grazing angles. The shear wave velocity and attenuation in the upper layer of ocean bottoms are estimated from the LF field-inverted effective bottom attenuations using a near-grazing bottom reflection expression for the equivalent fluid model, derived by Zhang and Tindle [J. Acoust. Soc. Am. 98, 3391–3396 (1995)]. The resultant shear wave velocity and attenuation are consistent with the SAX99 measurement at 25 Hz and 1000 Hz. The results are helpful for the analysis of shear wave effects on long-range sound propagation in shallow water.
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43.30.Ma Acoustics of sediments; ice covers, viscoelastic media; seismic underwater acoustics
43.30.Pc Ocean parameter estimation by acoustical methods; remote sensing; imaging, inversion, acoustic tomography

A vessel noise budget for Admiralty Inlet, Puget Sound, Washington (USA)

Christopher Bassett, Brian Polagye, Marla Holt, and Jim Thomson

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. 3706-3719 (2012); (14 pages) | Cited 1 time

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One calendar year of Automatic Identification System (AIS) ship-traffic data was paired with hydrophone recordings to assess ambient noise in northern Admiralty Inlet, Puget Sound, WA (USA) and to quantify the contribution of vessel traffic. The study region included inland waters of the Salish Sea within a 20 km radius of the hydrophone deployment site. Spectra and hourly, daily, and monthly ambient noise statistics for unweighted broadband (0.02–30 kHz) and marine mammal, or M-weighted, sound pressure levels showed variability driven largely by vessel traffic. Over the calendar year, 1363 unique AIS transmitting vessels were recorded, with at least one AIS transmitting vessel present in the study area 90% of the time. A vessel noise budget was calculated for all vessels equipped with AIS transponders. Cargo ships were the largest contributor to the vessel noise budget, followed by tugs and passenger vessels. A simple model to predict received levels at the site based on an incoherent summation of noise from different vessels resulted in a cumulative probability density function of broadband sound pressure levels that shows good agreement with 85% of the temporal data.
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43.30.Nb Noise in water; generation mechanisms and characteristics of the field
43.50.Lj Transportation noise sources: air, road, rail, and marine vehicles
43.50.Cb Noise spectra, determination of sound power
43.50.Rq Environmental noise, measurement, analysis, statistical characteristics

Simulations of multi-beam sonar echos from schooling individual fish in a quiet environment

Arne Johannes Holmin, Nils Olav Handegard, Rolf J. Korneliussen, and Dag Tjøstheim

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. 3720-3734 (2012); (15 pages)

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A model is developed and demonstrated for simulating echosounder and sonar observations of fish schools with specified shapes and composed of individuals having specified target strengths and behaviors. The model emulates the performances of actual multi-frequency echosounders and multi-beam echosounders and sonars and generates synthetic echograms of fish schools that can be compared with real echograms. The model enables acoustic observations of large in situ fish schools to be evaluated in terms of individual and aggregated fish behaviors. It also facilitates analyses of the sensitivity of fish biomass estimates to different target strength models and their parameterizations. To demonstrate how this tool may facilitate objective interpretations of acoustically estimated fish biomass and behavior, simulated echograms of fish with different spatial and orientation distributions are compared with real echograms of herring collected with a multi-beam sonar aboard the research vessel “G.O. Sars.” Results highlight the important effects of fish-backscatter directivity, particularly when sensing with small acoustic wavelengths relative to the fish length. Results also show that directivity is both a potential obstacle to estimating fish biomass accurately and a potential source of information about fish behavior.
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43.30.Sf Acoustical detection of marine life; passive and active
43.30.Ft Volume scattering
43.60.Cg Statistical properties of signals and noise
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Experimental assessment of four ultrasound scattering models for characterizing concentrated tissue-mimicking phantoms

Emilie Franceschini and Régine Guillermin

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. 3735-3747 (2012); (13 pages)

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Tissue-mimicking phantoms with high scatterer concentrations were examined using quantitative ultrasound techniques based on four scattering models: The Gaussian model (GM), the Faran model (FM), the structure factor model (SFM), and the particle model (PM). Experiments were conducted using 10- and 17.5-MHz focused transducers on tissue-mimicking phantoms with scatterer concentrations ranging from 1% to 25%. Theoretical backscatter coefficients (BSCs) were first compared with the experimentally measured BSCs in the forward problem framework. The measured BSC versus scatterer concentration relationship was predicted satisfactorily by the SFM and the PM. The FM and the PM overestimated the BSC magnitude at actual concentrations greater than 2.5% and 10%, respectively. The SFM was the model that better matched the BSC magnitude at all the scatterer concentrations tested. Second, the four scattering models were compared in the inverse problem framework to estimate the scatterer size and concentration from the experimentally measured BSCs. The FM did not predict the concentration accurately at actual concentrations greater than 12.5%. The SFM and PM need to be associated with another quantitative parameter to differentiate between low and high concentrations. In that case, the SFM predicted the concentration satisfactorily with relative errors below 38% at actual concentrations ranging from 10% to 25%.
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43.35.Bf Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions, and emulsions
43.35.Yb Ultrasonic instrumentation and measurement techniques
43.80.Vj Acoustical medical instrumentation and measurement techniques
43.80.Cs Acoustical characteristics of biological media: molecular species, cellular level tissues

A model for ultrasound absorption and dispersion in dilute suspensions of nanometric contrast agents

François Coulouvrat, Jean-Louis Thomas, Ksenia Astafyeva, Nicolas Taulier, Jean-Marc Conoir, and Wladimir Urbach

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. 3748-3759 (2012); (12 pages)

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Ultrasound dispersion and absorption are examined in dilute suspensions of contrast agents of nanometric size, with a typical radius around 100 nm. These kinds of contrast agents are designed for targeted delivery of drugs for cancer treatment. Compared to standard contrast agents used for imaging, particles are of smaller size to pass through the endothelial barrier, their shell, made up of biocompatible polymer, is stiffer to undergo a longer lifetime, and they have a liquid core instead of a gaseous one. Ultrasound propagation in dilute suspension is modeled by combining two modes for particle oscillations. The first one is a dilatational mode assuming an incompressible shell with a rheological behavior of Kelvin–Voigt or Maxwell type. The second one is a translational mode induced by visco-inertial interaction with the ambient fluid. The relative importance of these two modes of interaction on both dispersion and absorption is quantified and analyzed for a model system and for two radii (75 and 150 nm) and the two rheological models. The influence of shell parameters (Young modulus, viscosity, and relative thickness) is finally discussed.
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43.35.Bf Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in liquids, liquid crystals, suspensions, and emulsions
43.80.Qf Medical diagnosis with acoustics
43.80.Sh Medical use of ultrasonics for tissue modification (permanent and temporary)
43.20.Hq Velocity and attenuation of acoustic waves

Simulation of incoherent and coherent backscattered wave fields from cavities in a solid matrix

Valerie J. Pinfield and Richard E. Challis

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. 3760-3769 (2012); (10 pages)

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This paper reports a study of the backscattered ultrasonic signal from a solid layer containing spherical cavities, to determine the conditions in which an effective medium model is a valid description of the response. The work is motivated by the need to model the response of porous composite materials for ultrasonic non-destructive evaluation (NDE) techniques. The numerical simulation predicts the response of a layer containing cavities at a single set of random locations, and compares it to the predicted response from a homogeneous layer with ensemble-averaged material properties (effective medium model). The study investigates the conditions in which the coherent (ensemble-averaged) response is obtained even from a single configuration of scatterers. Simulations are carried out for a range of cavity sizes and volume fractions. The deviation of the response from effective medium behavior is modeled, along with the trends as a function of cavity radius, volume fraction, and frequency, in order to establish an acceptability criterion for application of an effective medium model.
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43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
43.35.Zc Use of ultrasonics in nondestructive testing, industrial processes, and industrial products

Theoretical microbubble dynamics in a viscoelastic medium at capillary breaching thresholds

Brandon Patterson, Douglas L. Miller, and Eric Johnsen

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. 3770-3777 (2012); (8 pages)

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In order to predict bioeffects in contrast-enhanced diagnostic and therapeutic ultrasound procedures, the dynamics of cavitation microbubbles in viscoelastic media must be determined. For this theoretical study, measured 1.5 to 7.5 MHz pulse pressure waveforms, which were used in experimental determinations of capillary breaching thresholds for contrast-enhanced diagnostic ultrasound in a rat kidney, were used to calculate cavitation nucleated from contrast agent microbubbles. A numerical model for cavitation in tissue was developed based on the Keller-Miksis equation (a compressible extension of the Rayleigh-Plesset equation for spherical bubble dynamics), with a Kelvin-Voigt constitutive relation. From this model, the bubble dynamics corresponding to the experimentally obtained capillary breaching thresholds were determined. Values of the maximum radius and temperature corresponding to previously determined bioeffect thresholds were computed for a range of ultrasound pulses and bubble sizes for comparison to inertial cavitation threshold criteria. The results were dependent on frequency, the gas contents, and the tissue elastic properties. The bioeffects thresholds were above previously determined inertial cavitation thresholds, even for the tissue models, suggesting the possibility of a more complex dosimetry for capillary injury in tissue.
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43.35.Ei Acoustic cavitation in liquids
43.35.Wa Biological effects of ultrasound, ultrasonic tomography
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Hybrid noise control in a duct using a light micro-perforated plate

X. N. Wang, Y. S. Choy, and L. Cheng

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. 3778-3787 (2012); (10 pages)

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A plate silencer consists of an expansion chamber with two side-branch cavities covered by light but extremely stiff plates. It works effectively with a wide stopband from low-to-medium frequencies only if the plate is extremely stiff, to ensure a strong reflection of acoustic wave to the upstream in the duct. However, a plate with a slightly weak bending stiffness will result in non-uniform transmission loss (TL) spectra with narrowed stopband. In this study, a hybrid silencer is proposed by introducing micro-perforations into the plate to elicit the sound absorption in order to compensate for the deficiency in the passband caused by the insufficient sound reflection in a certain frequency range due to weaker plate stiffness. A theoretical model, capable of dealing with the strong coupling between the vibrating micro-perforated plate and sound fields inside the cavity and the duct, is developed. Through proper balancing between the sound absorption and reflection, the proposed hybrid silencer provides a more flattened and uniform TL and a widened stopband by more than 20% while relaxing the harsh requirement on the bending stiffness of the plate. Theoretical predictions are validated by experimental data, with phenomenon explained through numerical analyses.
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43.50.Gf Noise control at source: redesign, application of absorptive materials and reactive elements, mufflers, noise silencers, noise barriers, and attenuators, etc.
43.55.Ev Sound absorption properties of materials: theory and measurement of sound absorption coefficients; acoustic impedance and admittance

Exposure modifiers of the relationships of transportation noise with high blood pressure and noise annoyance

Wolfgang Babisch, Wim Swart, Danny Houthuijs, Jenny Selander, Gösta Bluhm, Göran Pershagen, Konstantina Dimakopoulou, Alexandros S. Haralabidis, Klea Katsouyanni, Elli Davou, Panayota Sourtzi, Ennio Cadum, Federica Vigna-Taglianti, Sarah Floud, and Anna L. Hansell

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. 3788-3808 (2012); (21 pages)

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In the cross-sectional hypertension and exposure to noise near airports study the relationship between road traffic noise, aircraft noise and hypertension and annoyance was investigated. The data collection comprised a variety of potentially exposure modifying factors, including type of housing, location of rooms, window opening habits, use of noise-reducing remedies, shielding due to obstacles, lengths of exposure. In the present paper the quantitative role of these factors on the relationship between road and aircraft noise exposure and outcomes was analyzed. Multiple logistic and linear regression models were calculated including these co-factors and related interaction terms with noise indicators, as well as stratified analyses. Type of housing, length of residence, location of rooms and the use of noise reducing remedies modified the relationship between noise and hypertension. However, the effects were not always in the direction of a stronger association in higher exposed subjects. Regarding annoyance, type of housing, location of rooms, noise barriers, window opening habits, noise insulation, the use of noise reducing remedies, hours spent at home during daytime were significant effect modifiers. The use of noise-reducing remedies turned out to be indicators of perceived noise disturbance rather than modifiers reducing the annoyance.
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43.50.Qp Effects of noise on man and society
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Single-carrier frequency-domain turbo equalization without cyclic prefix or zero padding for underwater acoustic communications

Longbao Wang, Jun Tao, and Yahong Rosa Zheng

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. 3809-3817 (2012); (9 pages)

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A frequency-domain turbo equalization (FDTE) scheme without cyclic prefix (CP) or zero padding is proposed for single-carrier, multiple-input-multiple-output underwater acoustic communication. In the first iteration of the FDTE, the received continuous data stream is divided into consecutive blocks and a combined inter-block-interference (IBI) cancellation and overlapped windowing scheme is used to diagonalize each data block for low-complexity detection in the frequency domain. Since the second iteration, IBI cancellation and CP reconstruction are applied on each block to enable effective symbol detection. This work extends the authors' previous work on frequency-domain hard-decision equalization to soft-decision turbo equalization so that it not only retains high data transmission efficiency, but also improves the bit error rate performance with slightly increased complexity due to multiple iterations. Its feasibility and effectiveness have been tested by field trial data from the ACOMM09 underwater communication experiment.
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43.60.Ac Theory of acoustic signal processing
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
43.60.Gk Space-time signal processing, other than matched field processing

Sound field separation with sound pressure and particle velocity measurements

Efren Fernandez-Grande, Finn Jacobsen, and Quentin Leclère

J. Acoust. Soc. Am. Volume 132, Issue 6, pp. 3818-3825 (2012); (8 pages)

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In conventional near-field acoustic holography (NAH) it is not possible to distinguish between sound from the two sides of the array, thus, it is a requirement that all the sources are confined to only one side and radiate into a free field. When this requirement cannot be fulfilled, sound field separation techniques make it possible to distinguish between outgoing and incoming waves from the two sides, and thus NAH can be applied. In this paper, a separation method based on the measurement of the particle velocity in two layers and another method based on the measurement of the pressure and the velocity in a single layer are proposed. The two methods use an equivalent source formulation with separate transfer matrices for the outgoing and incoming waves, so that the sound from the two sides of the array can be modeled independently. A weighting scheme is proposed to account for the distance between the equivalent sources and measurement surfaces and for the difference in magnitude between pressure and velocity. Experimental and numerical studies have been conducted to examine the methods. The double layer velocity method seems to be more robust to noise and flanking sound than the combined pressure-velocity method, although it requires an additional measurement surface. On the whole, the separation methods can be useful when the disturbance of the incoming field is significant. Otherwise the direct reconstruction is more accurate and straightforward.
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43.60.Sx Acoustic holography
43.60.Pt Signal processing techniques for acoustic inverse problems
43.20.Rz Steady-state radiation from sources, impedance, radiation patterns, boundary element methods
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