bluuebunny/crossref_metadata_2025 huggingface dataset:
1998–99 blue whale call abundance off the central California coast using a bottom-mounted hydrophone
Authors: Kumar Anurag , Miller Christopher W. , Chiu Ching-Sang
Published: October 2013

Blue whale vocalizations were monitored off the central California coast during 1998–99 using the Naval Postgraduate Schools (NPS) Ocean Acoustic Observatory (OAO), a former US SOSUS array. The density of B calls were estimated using a matched filter detector based on a deverberated blue whale B call recorded from a towed array [T. C. Moore, Naval Postgraduate School, thesis (1999)]. The detectors’ performance characteristic was factored into the estimation to come up with the associated errors. Diurnal, seasonal, and inter-annular trends in call density were investigated. Also, the inter-call interval of the B call was measured. An unexpected large call density was observed during the first week of January in 1999. Historically, blue whales are sighted in Monterey Bay from approximately late July to October. Results of the blue whale call density estimation are discussed.
Automatic detection of sperm whale sounds from the Gulf of Alaska
Authors: Mellinger David K. , Stafford Kate , Fox Christopher G. , Moore Sue E.
Published: October 2013

Records from whaling ships in the Gulf of Alaska indicate that sperm whales were present in summer but were much less common in winter. These records could have been biased, perhaps strongly, by seasonal conditions: ships were less likely to be present in winter than summer, and sighting conditions may have been worse in winter. To obtain an independent and newer estimate of sperm whale seasonality, six autonomous hydrophone recorders were deployed for one year. After retrieval, recordings were analyzed automatically to detect sperm whale sounds. The detection technique comprised several successive stages: spectral transform, noise cancellation, band-limited energy summation, periodic autocorrelation, and thresholding. The autocorrelation step was highly effective for distinguishing between sounds of sperm whales and noise sources. The detection threshold was set so that, in test data, no noise sources were detected and approximately 2/3 of known sperm whale sounds were detected. Use of such a high threshold allows for an accurate index of sperm whale seasonal and geographic occurrence. Results indicate that sperm whales are indeed present in winter in the Gulf of Alaska. Use of automatic acoustic detection allows results to be replicated in the future.
Geographic variations in the whistles of spinner dolphins (Stenella longirostris)
Authors: Bazua-Duran Carmen , Au Whitlow W. L. , Oswald Julie N.
Published: October 2013

In order to better understand the reasons for geographic variations in the whistles of spinner dolphins (Stenella longirostris), recordings made in the Eastern Tropical Pacific will be compared to those recorded off Midway Atoll, Northwestern Hawai’ian Islands, the island of O’ahu, main Hawai’ian Islands, and Mo’orea, French Polynesia using discriminant function analysis. The values of 10 variables were extracted from the fundamental frequency (contour) of each whistle selected for analysis (begin, end, maximum, minimum and peak frequencies, center and peak times, duration, and number of turns and steps). Geographic variations in the whistles of spinner dolphins were found when comparing animals recorded in waters of Midway Atoll, off the main Hawai’ian Islands, and off Mo’orea. Greater differences were found between the Midway and Hawai’i and Mo’orea groups. The distinctiveness of Midway whistles could be due to geographic isolation and/or differences in population structure (habitat adaptation). The results indicate that geographic differences may not occur solely due to geographic isolation. Other factors, such as population structure and group size may be important when looking at differences in the whistles of spinner groups.
Use of high frequency acoustics to study the spatial distributions of bubbles
Authors: Terrill Eric , Melville Ken
Published: October 2013

It is well understood that the presence of bubbles in the ocean can dramatically change the sound speed, attenuation, and scattering of underwater sound over a range of frequencies. Over the last few decades, rational theories have been developed and tested that describe the complex dispersion of sound through spatially homogeneous bubbly mixtures as a function of the sizes and densities of bubbles. However, it is clear that in the ocean, the size distribution of the bubbles will evolve with a number of different temporal and spatial scales as a result of both the physics which govern their formation (breaking wind waves, breaking waves in the surf, rain generated bubbles, or ship wakes) and the physical processes which control their lifetimes: turbulent mixing, bubble rise speed, and gas dissolution. One approach to measuring their distribution in space is the application of O(1) MHz range-gated sonars which can resolve scales of O(1) cm. These high frequencies are also advantageous to work with since the scattering cross section of the bubbles is approximately proportional to the second moment of the size distribution. Results of field measurement efforts to characterize the spatial scales of bubbles from O(1) m to O(1) cm will be presented and discussed. [Work supported by the ONR Underwater Acoustics and Marine Optics programs.]
Managing uncertainty in ocean-acoustic tomography
Authors: Rudzinsky Jason , Rajan Subramaniam , Lewis James , Stein Peter
Published: October 2013

The Pacific Missile Range Facility, located off the west coast of Kauai, offers a unique opportunity to perform perpetual tomographic imaging of the sound-speed structure in the region. The range covers over 1100 square miles of ocean and features 172 bottom-mounted hydrophones and 15 bottom-mounted projectors. Data collected during an August, 2001 feasibility experiment suggest that a small subset of the total number of acoustic propagation rays connecting sources and receivers can be used to image prominent oceanographic features such as internal tides. However, acoustic travel time fluctuations occurring over durations of only a few seconds are a potentially significant source of error. Uncertainty in bathymetric relief also prohibits effective utilization of ray paths with multiple surface interactions in the inversion. Results of research intended to better manage these and other uncertainties are presented. The basis of this research is the use of repeated measurements, made every few seconds over many hours, along with a sophisticated ocean circulation model of the region and error decomposition techniques to isolate errors in assumed bathymetry and travel time noise. Inversion improvements as well as approaches to assimilating tomographic measurements into the ocean model are also discussed. [Funding provided by CEROS and ONR.]
Adjoint methods for two-dimensional inversion and error analysis
Authors: Hursky Paul , Porter Michael B. , Cornuelle Bruce D. , Hodgkiss William S. , Kuperman William A.
Published: October 2013

Adjoint methods provide a rapid technique for mapping observation errors back to the environmental errors that caused them. For instance, the acoustic pressure field can be measured in a complicated, unknown two-dimensional (2D) environment, and an acoustic model can be run for a simpler, presumed environment. The discrepancy can then be back-propagated to provide a corrected ocean structure. The adjoint model is particularly attractive when the observation space is small (few hydrophones) and the environmental space is large (thousands of points characterizing the range-depth sound speed field). In earlier work, we demonstrated this process for a range-independent scenario involving tracking of internal tides. Here we extend the technique to full 2D inversion. We also illustrate how the adjoint model can be used to construct a so-called representer for the range-depth sound speed function. The representers can be used to quantify the relationship between errors in the observations and errors in the resulting inversion. They can also be used to optimize the placement of assets such as XBT’s, identifying locations where the sound speed has the most influence on the current observations. We will discuss these approaches and demonstrate them using a 2D scenario in which we image a solibore.
Acoustic remote sensing from aboard the Royal Caribbean Cruise Lines passenger ship Explorer of the Seas
Authors: Palmer David R. , Cummings Shailer R. , Stamates S. Jack , Ortner Peter B. , Wilson Douglas
Published: October 2013

The NOAA/Atlantic Oceanographic and Meteorological Laboratory, Royal Caribbean International, and the University of Miami, with support from the National Science Foundation and the Office of Naval Research, have established modern, well-equipped oceanic and atmospheric research laboratories on the cruise ship Explorer of the Seas. This novel relationship between commercial, academic, and federal maritime communities is enabling scientists to collect a number of unique data sets. The instrumentation in the oceanic laboratory includes two RD Instruments Inc. Ocean Surveyor Acoustic Doppler Current Profiler’s (ADCP’s) for monitoring ocean currents and biomass, and seawater sensors for measuring temperature, salinity, chlorophyll-a, dissolved organic material, and dissolved oxygen. Data are collected weekly along the ship’s two repetitive cruise tracks through the Bahamas and the Caribbean. We summarize the acoustic observations made with the ADCP’s during the first year of operation of the laboratories. These observations are applicable to ongoing and planned regional research projects including those focused on ocean current systems and frontal boundary dynamics.
Nonlinear magnetoacoustic wave propagation with chemical reactions
Authors: Margulies Timothy Scott
Published: October 2013

The magnetoacoustic problem with an application to sound wave propagation through electrically conducting fluids such as the ocean in the Earth’s magnetic field, liquid metals, or plasmas has been addressed taking into account several simultaneous chemical reactions. Using continuum balance equations for the total mass, linear momentum, energy; as well as Maxwell’s electrodynamic equations, a nonlinear beam equation has been developed to generalize the Khokhlov–Zabolotskaya–Kuznetsov (KZK) equation for a fluid with linear viscosity but nonlinear and diffraction effects. Thermodynamic parameters are used and not tailored to only an adiabatic fluid case. The chemical kinetic equations build on a relaxing media approach presented, for example, by K. Naugolnukh and L. Ostrovsky [Nonlinear Wave Processes in Acoustics (Cambridge Univ. Press, Cambridge, 1998)] for a linearized single reaction and thermodynamic pressure equation of state. Approximations for large and small relaxation times and for magnetohydrodynamic parameters [Korsunskii, Sov. Phys. Acoust. 36 (1990)] are examined. Additionally, Cattaneo’s equation for heat conduction and its generalization for a memory process rather than a Fourier’s law are taken into account. It was introduced for the heat flux depends on the temperature gradient at an earlier time to generate heat pulses of finite speed.
Ultrafast imaging of shear waves induced by the acoustic radiation force for elasticity imaging in soft tissues
Authors: Bercoff Jeremy , Tanter Mickael , Chaffai Sana , Fink Mathias
Published: October 2013

Shear wave propagation induced by the acoustic radiation force is currently under investigation. In our experiments, an ultrafast scanner is used both to generate and detect shear waves propagation. The scanner is first used to focus, at a chosen location, a high intensity ultrasonic beam. The resulting acoustic radiation force induces in the focal zone a shear source. The system allows us then to apply very high ultrasound frame rates (up to 5000 images/s) in order to image the shear wave propagation, which velocity is linked to local elasticity properties of the medium. The elasticity map is recovered by solving the inverse problem. Actually, the generation of shear displacement requires high level insonifications at the threshold of FDA norms. Thus, the great advantage of such an ultrafast scanner is to recover the complete propagation by generating a unique palpation inside the medium. Measurements have been performed in several soft tissue mimicking phantoms with different elastic properties and in beef muscles. The 3-D finite differences simulations have been used to support our experimental results: the delivered acoustic power and the resulting heating induced by the acoustic focused beam can be estimated and compared with the FDA requirements.
Force distortion in a coil/magnet vibration exciter for shallow structures subjected to large displacements
Authors: Thomas Olivier , Chaigne Antoine
Published: October 2013

An electromagnetic noncontact vibration exciter has been designed for investigating nonlinear vibrations of shallow structures such as gongs, cymbals, and spherical shells. It is composed of two devices: a coil driven by a current and a small magnet glued on the structure. One interest of this system is that the mass of the magnet is small compared to the mass of the structure, so that its dynamic properties are only slightly modified. The magnitude of the force applied to the structure via the magnet depends on the relative position of magnet and coil. As a consequence, an harmonic distortion appears in the force wave form as the magnitude of the magnet displacement increases. A theoretical study is first carried out in order to find an optimal geometry for the coil that minimizes the force distortion. In a second step, a simple degree-of-freedom model is used to evaluate the distortion rate. It is found that this rate not only depends on the exciter properties, but also on the dynamics of the system under testing. A multiple-scale technique is used for the resolution of the nonlinear model that governs the distortion. Experimental results will be presented which confirm the theoretical predictions.
Nondestructive evaluation of conformal sonar hull array manufacture and installation
Authors: Doane John W. , Trivett David H. , Jarzynski Jacek , Batel Mehdi
Published: October 2013

The Conformal Array VElocity Sonar (CAVES) consists of an array of neutrally buoyant accelerometers mounted on a compliant layer that is adhered to the hull with an approximately one inch thick layer of Versathane. The performance of this sonar is dependent upon having uniform material properties and on having a bond to the hull free of voids and delaminations. Due to the high propagation loss in the compliant layer, conventional ultrasonic techniques cannot be utilized. There is also the need to directly measure the physical properties of the compliant layer since it has been demonstrated that QA samples do not have the same properties. Two non-destructive evaluation techniques are presented. In the first, a point drive is used to excite elastic waves in the compliant layer. The resulting motions are measured with a Laser-Doppler Vibrometer and an optimization technique is used to determine the complex (real and imaginary components) material properties. This method also lends itself to finding macrovoids within the compliant layer. In the second technique the vibration source excites the bond layer from a free edge. The array sensors are then used to determine the presence of bond failures. Both theory and experimental results are presented.
Matching of ultrasonic transducer: Interest of the glue layer
Authors: Callens Dorothee , Bruneel Christian , Assaad Jamal
Published: October 2013

Our objective in this study is to propose a new solution to the acoustic impedance mismatch between a PZT transducer and a water load. Broad bandwidth matching to water is often perforrmed theoretically by using a quarter wave layer with a characteristic acoustic impedance of 7 MRayl. Practically, it is difficult to find material with this particular impedance. Moreover, performances of this matching can be reduced by the thickness of the glue coating between the quarter wave layer and the transducer. The approach we proposed consists in using the glue coating as a controlled matching layer. Once the glue is taken as the first matching layer, the range of available material for the second layer is very large. In our configuration, the front face matching is achieved using glass. The thickness of each matching layer is then calculated as a function of the impedance of the constitutive layer of the multilayer PZT/Layer 1: Glue/Layer 2: Glass/Water. The new two-layer matching configuration is compared to the ideal quarter wave layer matching. It will be shown that this new configuration provides performances as good as those obtained with conventional quarter wavelength matching.
Time–domain simulation of a guitar
Authors: Derveaux Gregoire , Chaigne Antoine , Joly Patrick , Becache Eliane
Published: October 2013

Our purpose in this study is to present a time–domain numerical modeling of the guitar. The method consists in the modeling of the vibratory and acoustical phenomena from the initial pluck to the 3-D radiation. An idealized plucking force is acting on a 1-D damped string model. The string is coupled to the soundboard via the bridge. The soundboard is modeled as an orthotropic heterogeneous damped Kirchhoff–Love plate, with a soundhole, clamped at its boundaries. The other parts of the body (back, neck, sides,...) are assumed to be perfectly rigid. The plate radiates both inside the cavity and in the external free field. We obtain a system of partial differential equations which are solved numerically in the time–domain. The fluid–structure interaction, in particular, is solved by using a fictitious domain method, which preserves the efficiency of the finite difference method for the 3-D radiation and approximates precisely the shape of the instrument. This technique allows us to observe the evolution of the acoustic field with time inside and outside the cavity. From a musical viewpoint, the computation of important quantities such as sound intensity, directivity, sound power, or energy transfer between the cavity and free field are made possible.
Standards 101; the ASA standards program
Authors: Schomer Paul D.
Published: October 2013

ASA supports the development of standards by serving as the secretariat for standards committees of the American National Standards Institute (ANSI). The program is organized through four ANSI technical committees (S1, S2, S3, and S12) and one administrative committee (ASACOS). S1 deals with physical acoustics, S2 deals with shock and vibration, S3 deals with physiological and psychological acoustics, and S12 deals with noise. ASACOS is the ASA Committee on Standards. The program has three primary tasks: (1) the development of National Standards (ANSI Standards), (2) the national adoption of an international standard (ANSI NAIS Standards), (3) providing the USA input to the development of International Standards (ISO and IEC Standards). At every level the main work is accomplished in Working Groups (WG) that are ‘‘staffed’’ by hundreds of volunteers—mainly ASA members from its various technical committees such as Noise, Physical Acoustics, Architectural Acoustics, Psychological and Physiological Acoustics, etc. Overall, the Standards Program involves more ASA members than does any other single function of the Society except meetings and it is the biggest outreach function of ASA affecting the health, welfare, and economic well-being of large segments of the population, the business and industrial community, and government at all levels.
Not another airport noise metric
Authors: Timmerman Nancy
Published: October 2013

The assessment of airport noise in communities has been fraught with confusion by the proliferation of metrics. This paper will discuss the origins and uses of unusual acoustic metrics such as Time Above, Community Noise Index (CNI), Noise per Seat Index (NPSI), D-weighting, and exposure (EXP); and compare them with more ordinary ones such as Effective Perceived Noise Level (EPNL), Day–Night Equivalent Sound Exposure Level (DNL), A-weighting, maximum level (Lmax), and signal-to-noise ratio (S/N). The metrics will then be scrutinized from the technical, airport, and community viewpoints, and the strengths and weaknesses of each will be discussed. Nonacoustic factors, such as listener expectations, will also be discussed. It will be seen why so many different types of decibel have led to confusion.
The uncertainty of engineering grade community noise surveys and predictions relative to two particular variables
Authors: Putnam Robert A.
Published: October 2013

The uncertainty inherent in the estimation of the sound power level of any noise source, coupled with the variability of assumptions regarding the modeling of typical noise sources combine to yield an A-weighted sound level predicted uncertainty on the order of 3 dB(A). This will be related to the expected uncertainty of an Engineering Grade sound survey suggested in international standards, such as ISO 6190. However, since ISO 6190 uncertainty is intended to be the measurement uncertainty, the question arises as to how we are to evaluate such combinations of measurement and predictive uncertainties. The author will discuss and defend the view that such uncertainties are additive and will propose the method of combining these effects. The modeling variables to be considered will be confined to the nature of the distributions of the source sound power level over the surface of the actual sound source, and the effects such assumptions have when considered in conjunction with barriers.
Acoustic wave spectroscopy inside a reverberant media with moving scatterers
Authors: de Rosny Julien , Roux Philippe , Fink Mathias
Published: October 2013

In this work, we present an original method in order to measure static and dynamic parameters of moving scatterers confined inside a strong reverberant cavity. In such media, wave propagation is very complex due to multiple scattering and multiple reflections. In a previous article (de Rosny et al., J. Acoust. Soc. Am. (2001)], we have shown that the number or the elastic cross section of moving scatterers, like a school of fish in an aquarium, are deduced from the pressure field averaged over different and independent positions of the scatterers cloud. In this talk, we present an extension of this work which also takes into account the scatterer’s dynamics, e.g., mean speed. Basically, the idea is to relate the correlation of the pressure field to the scatterer’s motion. A DAWS-like (Diffusive Acoustic Wave Spectroscopy) theory based on a statistical approach of this system is presented. The theory is compared with experimental data obtained with scatterers whose motion and elastic cross section are known. Finally this method is applied in order to survey the dynamic behavior of a school of fish inside an aquarium under some environmental modifications as luminosity or temperature.
Sound field representation by virtual potential near apex and its application to boundary value problem
Authors: Ueda Mitsuhiro , Funatsu Ryohei , Tjundewo Lawu
Published: October 2013

A new scheme for representing 2D sound field diffracted by a rigid polygon is proposed where the sound field is described by a sum of two potentials, that is, one that depends on the geometrical arrangement of a point source, an observation point and the polygon and the other that depends on the contribution from the potential at the surface of the scatterer. The latter potential is calculated by assuming virtual potentials in the vicinity of every apex of the polygon and the sound field is calculated using the virtual potential even in the vicinity of the apex using virtual discontinuity principle of diffraction that has been proposed by us before. The virtual potential is fixed so that the calculated potential is continuous across the apex. Consequently two sampling points are necessary in the vicinity of every apex to assure the continuity of the potential across the apex. Thus, the total number of sampling points can be reduced remarkably in this new method. The new method is applied to a semi-infinite plane and a strip and the estimated boundary values are compared with rigorous solutions. Remarkably good agreements are obtained using few sampling points.
Phonemic errors are not always categorical: Articulatory evidence
Authors: Pouplier Marianne , Goldstein Louis
Published: October 2013

Recent speech error research has challenged the traditional view that the temporal mislocation of a segment leaves its structural phonological integrity unaffected. Results of several studies suggest the existence of subsegmental, phonologically ill-formed errors (e.g., Mowrey and MacKay, J. Acoust. Soc. Am. 88, 1299–1312 (1990)]. While Pouplier et al. [J. Acoust. Soc. Am. 106, 2242 (1999)] could demonstrate on the basis of articulatory data that errors involve systematic movements of individual speech gestures, their data are limited to tongue-twister-like stimuli. This leaves open the possibility that the errors they observe might arise at a low execution level given the repetitive nature of the task. The present study employs the SLIP elicitation technique [Motley and Baars, Commun. Quart. 24, 28–24 (1976)] which is traditionally hypothesized to reflect errors at an abstract phonemic planning level (subjects produce target word pairs in isolation). Results show that also in presumably abstract ‘‘planning errors,’’ often two gestures are coproduced (one erroneous, one appropriate), resulting in an illicit phonological structure. These findings call into question the assumption that segments are primary units of speech production. [Work supported by NIH.]
Neutralization of word-final voicing in Russian
Authors: Shrager Miriam
Published: October 2013

This paper reexamines the well-established view in phonology that in Russian there is a voicing neutralization of obstruents in word final position. An experiment was conducted with Russian data that included coronal stops in final position. For each target word four measurements were taken: (1) the duration of the vowel that precedes the target obstruent, (2) the duration of the final obstruent, (3) duration of voicing into the consonant closure, (4) the burst duration of the final stop. The results of Anova statistics test demonstrated that the only variable that had a significant difference between the two groups was the burst duration. However discriminant analysis showed that about 74% of tokens were correctly classified. These results mean that an incomplete neutralization effect exists in Russian in word final position.
Extracting the Green’s function between receivers using underwater acoustic noise
Authors: Roux Philippe , Lynch Steve , Kuperman W. A. ,   NPAL group
Published: October 2013

Recent experimental and theoretical works in ultrasonics show that the Green’s function between transducers fastened to an aluminum sample can be measured from the correlation of thermal noise [R. L. Weaver and O. J. Lobkis, ‘‘Ultrasonics without a source. Thermal fluctuation correlations at MHz frequencies,’’ Phys. Rev. Lett. 87, 134301 (2001)]. Similar results have been obtained in geophysics using seismic noise data [A. Paul and M. Campillo, ‘‘Extracting the Green’s function between two stations from coda waves,’’ Trans. Am. Geophys. Union 82–47, F842 (2001)]. Sources of noise in underwater acoustics range from ship noise at low frequency to surface noise and even thermal noise at very high frequencies. We theoretically demonstrate that at least an approximate Green’s function can be obtained from surface noise. This result is confirmed by noise data recorded on arrays of receivers during the NPAL98 experiment. [Work supported by ONR.] a)The NPAL group is composed of J. A. Colosi, B. D. Cornuelle, B. D. Dushaw, M. A. Dzieciuch, B. M. Howe, J. A. Mercer, R. C. Spindel, and P. F. Worcester.
Temporal coherence and time spread of ocean surface scattered high frequency acoustic signals
Authors: Lutz Steven , Bradley David , Reeves Jon
Published: October 2013

The influence of the ocean environment on the temporal coherence and time spread of high frequency, surface scattered and fully refracted acoustic signals over intervals ranging from a few seconds to tens of hours have been investigated experimentally. Acoustic data were collected during the broadband coherence experiment conducted in July 2002 off the coast of San Diego in a water depth of 1000 m. Signals transmitted include short pure tone pulses and broadband (up to 22 kHz) linear frequency modulated (LFM) sweeps centered at 20, 40, and 60 kHz. The projectors were suspended at two depths from a moored buoy at two different ranges. The receiver hydrophones were suspended from a subsurface float at depths from 40 m to 300 m. Environmental measurements included a towed CTD string, water temperature at a fixed point, near surface bubble layer using a multibeam sonar, current speed and direction, directional wave height, and wind speed. [Work supported by ONR Code 321US under the ARL Program.]
Estimation of increased attenuation of turbofan inlet noise with optimized and active liners
Authors: Patrick William P. , Hardin Larry W.
Published: October 2013

A modified version of the Eversman finite element code is used to estimate the maximum attenuation benefit obtainable in a typical aircraft nacelle lined with a perfect absorber, having the optimum impedance at each frequency and for each mode. The radiated acoustic wave pattern is computed from the fan face to the far field. Calculations are presented for the first 4 radial modes of the first cut-on circumferential mode at 2 BPF (blade passing frequency) for an Advanced Ducted Propeller model. For each mode the program performed a parametric variation of the nacelle wall liner impedance to determine the optimum impedance which minimized the peak sound pressure level at the far-field boundary. Results for an inlet having a hard wall, an optimal passive liner, a uniform (single element) active liner having an optimized impedance, a liner having linearly varying impedance from fan face to the inlet, and a fully optimized (30 liner segments) active liner are presented. Attenuation of the optimized liner having uniform impedance compared to the hard-wall case is 11.2 dB, 4.9 dB, 4.2 dB, and 7.4 dB for radial modes 0, 1, 2, and 3, respectively. Linearly varying the impedance increased the attenuation slightly. The ability of the liner to significantly alter the pressure pattern within the nacelle is shown quite clearly in the visualized pressure field.
Simulation of acoustic wave behavior in ducts and a plenum using finite elements package ANSYS
Authors: Villalobos-Luna Jose de Jesus , Lopez-Cruz Pedro , Ramirez-Valencia Ricardo , Elizondo-Garza Fernando J.
Published: October 2013

This paper shows and discusses the use of the finite element software ANSYS for simulation of the behavior of sound waves in a ducts-plenum system. The modeling is intended for didactic purposes, beginning with simple three-dimensional geometries of ducts and plenum. Two conditions can be included: (1) with and without acoustical absorbent materials on the inside walls of the ducts and (2) including or not labyrinths. The analysis allows students to see the behavior of the waves inside the duct-plenum system and they can manipulate the parameters of the model to improve the attenuation characteristics of the system.
Active noise control technique for diesel train locomotor exhaust noise abatement
Authors: Cotana Franco , Rossi Federico
Published: October 2013

An original prototype for train locomotor exhaust gas pipe noise reduction (electronic muffler) is proposed: the system is based on an active noise control technique. An acoustical measurement campaign has shown that locomotor exhaust noise is characterized by very low frequency components (less than 80 Hz) and very high acoustic power (up to 110 dB). A peculiar electronic muffler characterized by high acoustical efficiency at very low frequencies has been designed and realized at Perugia University Acoustic Laboratory; it has been installed on an Italian D.245 train locomotor, equipped with a 500-kW diesel engine. The electronic muffler has been added to the traditional passive muffler. Very low transmission losses are introduced by the electronic muffler because of its particular shape; thus, engine efficiency does not further decrease. Canceling noise is generated by means of DSP-based numerical algorithm. Disturbing noise and canceling noise destructively interfere at the exhaust duct outlet section; outgoing noise is thus reduced. The control system reduces exhaust noise both in the steady and unsteady engine regime. Measurement results have shown that electronic muffler introduces up to 15 dB noise abatement in the low-frequency components.
Active control of automotive fan noise
Authors: Gerard Anthony , Berry Alain , Masson Patrice
Published: October 2013

Active control for globally reducing the noise radiated by automotive axial engine cooling fans is investigated. First, an aeroacoutic model of the fan is combined with acoustic directivity measurements to derive a distribution of equivalent dipole sources on the fan surface. The results reveal that the fan behaves like a distributed dipole at blade passage tones when the upstream flow through the fan is spatially nonuniform. Numerical simulations of active noise control in the free field have been carried out using the previous aeroacoustic model of the fan and a dipole secondary source in front of the fan. The numerical results show that a single dipole control source is effective in globally controlling the sound radiation of the fan at the blade passage frequency and its first harmonic. Last, an experimental investigation of active control is presented. It consists of a SISO feedforward configuration with either a LMS algorithm (for FIR filters) or a back-retropopagation algorithm (for neural networks) using the Simulink/Dspace environment for real-time implementation.
Developing active noise control systems for noise attenuation in ducts
Authors: Campos Rosely V. , Ivo Rodrigo C. , Medeiros Eduardo B.
Published: October 2013

The present work describes some of the research effort on Active Noise Control (ANC) being jointly developed by the Catholic University of Minas Gerais (PUC-MINAS) and the Federal University of Minas Gerais (UFMG). Considerations about the implementation of Digital Signal Processing for noise control in ducts has been presented. The objective is to establish a study on Active Noise Control in ducts combining geometry and acoustic parameters modification together with adaptive digital filtering implementation. Both algorithm and digital signal processing details are also discussed. The main results for a typical application where real attenuation has been obtained are presented and considered according to their use in developing real applications. The authors also believe that the present text should provide an interesting overview for both designers and students concerned about Active Noise Control in ducts. (To be presented in Portuguese.)
Acoustic insulation of recent flat buildings in Pamplona, Spain
Authors: Arana Miguel A. , San Martin Ricardo , Vela Antonio , San Martin Maria L.
Published: October 2013

The Municipal Government of Pamplona and the Housing Department of the Government of Navarra (Spain) decided to evaluate acoustic insulation of new flat buildings in Pamplona. Such study was ordered to the Acoustic Laboratory of the Public University of Navarra. During the last year, measurements relating to acoustic insulation were carried out in most of the new blocks of flats made in Pamplona. The results obtained show that acoustic insulation is insufficient in most buildings both for airborne sound reduction and for impact sound. The figures required by Spanish legislation do not fulfil in more than 80 percent of the cases. On the other hand, a great correlation between sound reduction figures obtained from index of ISO 140-4 and from R (in dBA) of the Spanish norm for in situ measurements was carried out. A new Spanish legislation will be approved shortly.
The need for standards and codes to ensure an acoustically comfortable environment in multifamily housing buildings in Mexico City
Authors: Kotasek Gonzalez Eduardo , Rodriguez Manzo Fausto
Published: October 2013

It is clear that almost all kinds of buildings require protection against noise and undesirable sounds, however, there are some countries where this is not yet regulated, such is the case of Mexico. Mexico City, the biggest city in the world could also be the noisiest. This is a problem which is today being debated; in fact there is no doubt that this has an important influence on the acoustic comfort conditions of dwellings, besides the habits and culture of the inhabitants, which are very different from those in the Anglo-Saxon countries. These are all details that must be taken into account in the design of an acoustic comfort standard for buildings in cities like Mexico. In this paper we deal with this problem and it suggests some recommendations to consider in a proposed acoustic comfort standard or code to be applied in the design of multifamily housing buildings in Mexico City.
The architecture of shopping centers: An acoustical perspective
Authors: Kusakawa Marisa S. , Viveiros Elvira B.
Published: October 2013

This paper analyzes the current state-of-the-art of the architecture of shopping centers from an acoustical point of view. There has been a worldwide spread of such buildings, whose characteristics do not differ much across cultural or climatic conditions. Despite the success achieved as a commercial product for big and medium cities, the acoustical comfort of employees and consumers has not been of concern. The food court and recreational areas tend to be reverberant spaces and usually very noisy. The research aims to correlate modern architectural solutions and typical sound fields generated in these buildings, taking a Brazilian case study. Also intended is to establish guidelines for architects and planners in order to provide acoustical comfort.
Classroom acoustics in Omaha, Nebraska: Measurements and outreach
Authors: Bowden Erica E. , Wang Lily M. , Bradley David T.
Published: October 2013

This project collected data detailing the current status of classroom acoustics while simultaneously increasing awareness of educational acoustics and exposure to acoustical engineering research in local schools. In 8 Omaha-area schools, 2 acoustical aspects which directly influence speech intelligibility were measured and studied: (1) background noise levels resulting from a building’s mechanical systems; and (2) reverberation times within the classroom. Prior to each measurement session, a presentation on good classroom acoustic principles was presented to the teacher and students in that classroom. Subsequently, the teacher and students assisted the principal investigator and research assistants in the measurement of the acoustic data from their classroom. In total, 13 classrooms were studied, with the assistance of 425 middle and high school students in 14 different classes. The background noise results have been associated with commonly used noise criterion curves. Results are compared to recommended background noise levels and reverberation times suggested by ANSI standard S12.60-2002. The resulting database provides knowledge on the current status of classrooms in Omaha, and may be indicative of classroom situations across the midwestern United States.
Semantic differential analysis on the soundscape of urban open public spaces
Authors: Kang Jian , Zhang Mei
Published: October 2013

Physical comfort in urban open public spaces, including acoustic comfort, has been paid increasing attention. The objective of this research is to identify factors that affect acoustic comfort and soundscape in urban open public spaces. In January 2002 a soundscape walk was organized with 50 university students and evaluation on acoustic comfort and sound quality was carried out in four typical urban open public spaces in Sheffield, UK. Both overall acoustic comfort and individual sounds were evaluated, using 28 indices. Objective measurements were made simultaneously. In March–April 2002, 500 interviews were carried out with various users in two selected open public spaces. Semantic differential analysis of the results shows that the description and evaluation of acoustic comfort and soundscape in urban open public spaces is more complicated than that for product sound quality, but it is still possible to identify several major factors including pleasant, timber, content, and evaluation. Based on the analysis, methods for evaluating acoustic comfort and soundscape in urban open public spaces are proposed. [Work supported by Key Action 4 ‘‘City of Tomorrow and Cultural Heritage’’ from the programme ‘‘Energy, Environment and Sustainable Development’’ within the Fifth Framework Programme of the European Commission.]
Investigation of clamping force in resonant ultrasound spectroscopy
Authors: Guo Hang , Lal Amit
Published: October 2013

In this paper we studied the effect of clamping force on using resonant ultrasound spectroscopy (RUS) to determine the elasticity of solids. The foundation of RUS is the free vibration of solids under free boundary conditions. In the practical RUS measurement, the sample of solids is required to contact piezoelectric transducers for excitation and detection of its vibrations, and an amount of clamping force is needed to obtain high signal to noise ratio for the useful measured spectrum. However, the clamping force will shift natural frequencies of the sample. Thus, the accuracy of RUS is affected. In our study, finite element method is used to analyze the effect of the clamping force on the vibration of the sample. A static structural analysis for the sample under the clamping force was first done to turn the effect of the clamping force into the pre-strain of the sample, and then the natural frequencies of the pre-strained sample were calculated. Experimentally, a model to control the clamping force was set up from the bending of an equivalent cantilever. In the end, silicon samples of different sizes had been measured under different clamping forces to verify the presented method for the study of clamping force in RUS.
Resonant ultrasound spectroscopy applied to misoriented crystals of low symmetry: Corundum
Authors: Gladden J. R. , So Jin H. , Maynard J. D.
Published: October 2013

The vibrational resonance spectrum of a single crystal depends on the mass density, geometry, and elastic tensor of the material. Resonant ultrasound spectroscopy (RUS) derives the elastic tensor from a measured set of sample resonances. Any tensor quantity must be defined relative to some coordinate system which, for single crystals, is often coordinated with the crystal lattice vectors. If the elastic tensor coordinate system does not coincide with the principal axes of the sample, the tensor must be transformed via a rotation matrix creating an effective elastic tensor for the sample. Misorientation may occur by design, sample preparation constraints, or errors. This problem becomes particularly important for crystals of low symmetry, such as corundum, a trigonal crystal with six independent elastic constants, or when highly accurate results for derived elastic constants are desired. In this talk, techniques for analyzing such misoriented samples with RUS will be presented along with experimental data for corundum and a correction for the sign of C14.
Statistical analysis and measurement of thermodynamical properties of a supersonic air jet
Authors: Perez-Guerrero Armando , Alvarado Manuel , Stern Catalina , Puente Margarita
Published: October 2013

In this work, we present a new method for measuring the pressure and the temperature of a supersonic airflow. These quantities are necessary to evaluate mathematical models applied to the study of shock waves. By means of a microphone and a thermocouple we measure these quantities through perturbations produced inside the flow by shock waves. We applied Fourier transform and several statistic methods in order to analyze and evaluate the signals obtained.
Combining and comparing time reversal processing and adaptive channel equalization for communication sequences
Authors: Edelmann Geoffrey F. , Kim Seongil , Hodgkiss W. S. , Kuperman W. A. , Song H. C. , Akal Tuncay
Published: October 2013

Time reversal (TR) backpropagates a signal to its origin despite the complexity of the propagation channel. The application of TR to acoustic communications previously has been demonstrated. Here, we discuss the advantages of an implementation of the TR process cascaded with adaptive channel equalization. This combination makes spatial diversity unnecessary in the receiver structure. In addition, comparisons will be drawn between single source and TR transmissions in combination with adaptive channel equalization. [Work supported by ONR.]
Random sampling applied to array beamforming: The aggregate beamformer
Authors: Havelock David I.
Published: October 2013

It is shown how beamforming can be accomplished by randomly sampling array elements and time-aligning the data samples. The time-aligned samples are referred to as the ‘‘aggregate’’ signal. Time-alignment is done using conventional beamforming delays but data values are not summed. Beamforming weights (array shading) can be applied by modifying the sampling probability for each sensor. Simple methods for reconstruction of the original signal from the aggregate signal are discussed. The reconstructed signal of this aggregate beamformer has the same directional response as a conventional beamformer except that off-beam signals are transformed into white noise. This noise can be reduced as required by adjusting the sampling rate of the aggregate signal. Higher beam-steering resolution than that of conventional beamforming is achieved without the need for data interpolation. The hardware and computational complexity of the aggregate beamformer does not increase as the number of array elements is increased. Aggregate beamforming offers a high degree of integration for arrays with many elements, such as 3-D arrays.
Computing rough surface Doppler effects on broadband pulse propagation using a split-step Fourier parabolic equation model
Authors: Smith Kevin B. , Ead Richard
Published: October 2013

The current interest in broadband pulse propagation in shallow water is increasing with the need for improved active sonar systems and the growth of applications utilizing underwater acoustic communications. Such shallow-water propagation is dominated by boundary interactions. If the ocean surface is rough on the scale of the acoustic wavelength, considerable scattering can occur that can significantly influence the coherent propagation. Because the rough ocean surface is also evolving dynamically, such scattering can introduce Doppler shifting and spreading of the acoustic pulse spectrum. Following the method of F. D. Tappert and L. Nghiem-Phu [J. Acoust. Soc. Am. Suppl. 1 77, S101 (1985)], an exact formulation for scattering from a rough surface is introduced into the Monterey-Miami Parabolic Equation Model [JCA 9, 243–285 (2001)]. An algorithm is then developed for computing the solution of pulse propagation as the rough surface evolves dynamically. The result can be shown to produce the proper spatial scattering as well as introduce the correct Doppler shifts from the dynamic surface. A simple sinusoidal rough surface interface will be employed to test the algorithm followed by a more complex, realistic rough ocean interface. Spatial and temporal properties of the scattered field will be examined and discussed.