bluuebunny/crossref_metadata_2025 huggingface dataset:
On the use of tailored functional bases for space launcher noise sources localization and reconstruction
Authors: Casalino Damiano , Santini Samuele , Genito Mariano , Ferrara Valerio
Published: October 2011

A source localization and inverse reconstruction methodology is applied to analyze wall pressure signals measured on the surface of a space launcher mock-up. The methodology is based on the use of elementary acoustic solutions tailored to the space launcher geometry as functional basis. Two classes of functional bases are considered: plane waves impinging on the surface of an infinite cylinder computed analytically through a literature formula, and plane waves impinging on the real space launcher computed numerically through a FEM computational acoustic technique. In both cases, the 3D acoustic field resulting from the impingement of an arbitrarily oriented plane wave is obtained by a truncated series summation of elementary axial-symmetric solutions. These two classes of functional bases are proven to provide consistent results in the addressed frequency range. However, although the analytical basis enables a faster localization of the noise sources that take place during the rocket firing, the numerical basis is expected to enable, at an acceptable computational cost, a more reliable reconstruction of the acoustic loads on the space launcher surface in a higher frequency range. The proposed FEM-based beam-forming and source reconstruction technique is therefore a useful tool for the vibro-acoustic design of future launch vehicles.
On the use of prepolarized microphones in rocket noise measurements
Authors: Taylor R. Troy , Gee Kent L. , Giraud Jarom H. , Sommerfeldt Scott D. , Blotter Jonathan D. , Wiederhold Curtis P.
Published: October 2011

The acoustic field near large-scale solid rocket motors represents a harsh, high-amplitude noise environment rich with high-bandwidth acoustic shocks. Type-1 prepolarized microphones may be used in these environments with the benefit of reduced cost and measurement because they require only a constant-current supply available in many data acquisition systems. However, there are two potential issues related to microphone response that should be considered. The first is a well-known RC-lowpass filter effect that is associated with using insufficient current to drive long cables with relatively high capacitance. The second has to do with temporary failure of the constant-current supply due to an insufficiently fast response time in representing rapid voltage changes at shocks, which results in spurious, capacitive-like effects in the waveform data that are also manifest as a low-frequency roll-up in the spectrum noise floor. An experiment was conducted to identify under what circumstances these waveform effects arise. Data were measured from a solid rocket motor using several combinations of transducer, cable type, cable length and constant current supply. Results and mitigation methods found from the experiment are discussed. These include increasing the supply current, using low-impedance cables, and selecting microphones with low sensitivities.
On the computation of farfield cross-spectra and coherences from reduced parameter models of high speed jet noise
Authors: Vold Havard , Shah Parthiv , Yang Mike
Published: October 2011

Reduced parameter models of jet noise mechanisms serve as computational vehicles to estimate sound pressure and directivies at arbitrary locations in the farfield. The customary formulations have been successful at predicting autospectra and directivities, but the calculation of crossspectra and coherences has not been attempted. The authors will present a procedure for calculating crossspectra and coherences from the simple source model, i.e., an equivalent monopole density over a volume enclosing the jet noise sources. It will be shown that realistic coherences and crossspectra are only well defined when several mutually incoherent noise sources are being considered, and both convergence and spatial aliasing phenomena will be defined and investigated.
Waveguide sound propagation in a turbulent atmosphere above a statistically rough surface of the ground
Authors: Ostashev Vladimir E. , Wilson D. Keith , Vecherin Sergey N.
Published: October 2011

Waveguide sound propagation in a refractive, turbulent atmosphere above a statistically rough surface of the ground is considered. The waveguide is formed between the surface of the ground and turning points of sound waves in the downwind direction or in a nocturnal boundary layer of the atmosphere when the temperature increases with height. Using a modal decomposition of the sound field and the Chernov method, closed-form equations for the coherence function of the sound field are derived. The solution is expressed in terms of the effective turbulence spectrum, which is a linear combination of the 1-D spectra of temperature and wind velocity fluctuations, and a spectrum of the surface roughness. The coherence function can be calculated with equations obtained or by using the effective spectrum in the already existing code for the coherence function of the sound field propagating in a refractive, turbulent atmosphere above a flat ground [D. K. Wilson, V. E. Ostashev, and M. S. Lewis, Waves Rand. Comp. Media, V. 19, 369–391 (2009)]. The derived effective spectrum is also used to study the relative contributions of atmospheric turbulence and surface roughness to the coherence loss of propagating sound.
Sensitivity to changing characteristics of Gaussian-shaped stimulus distributions in auditory categorization
Authors: Sullivan Sarah C. , Tanji Johnna A. , Lotto Andrew J. , Diehl Randy L.
Published: October 2011

This experiment examined the ability of human listeners to categorize sounds as a function of changing training distribution characteristics. Participants were presented non-speech sounds randomly sampled from two overlapping, Gaussian-like distributions. The sounds consisted of narrow-band noise bursts varying in center frequency. Participants mapped the distributions of sounds onto creatures in a video game receiving visual and auditory feedback about accuracy. The distributions were constant for half of the participants. For the other half, an unsignaled switch to distributions with a new optimal boundary occurred in the middle of the session. By examining obtained category boundaries one can distinguish between 3 possible responses to the switch: (1) adaptive switching resulting in the new optimal boundary being learned; (2) persistence of first learned boundary; and (3)averaging input across the entire session, resulting in an obtained boundary midway between the first and second optimal boundaries. The results demonstrate that most listeners could adaptively switch between distribution conditions with no external signal informing them of such a switch. The results indicate that most listeners are updating possible underlying distributions of input in a remarkably adaptive manner. [Work supported by NIH.]
Phonetic and acoustic differences in child and adult laughter
Authors: Menezes Caroline , Diaz Samantha
Published: October 2011

This is a preliminary study comparing the acoustic differences in recordings of child and adult spontaneous laughter. Altogether, 100 laughter calls where analyzed from one male and female adult and one male and female child. Results indicate that bout and call durations of children and adult laughter are similar in duration; however, segmental durations show developmental differences. Children show variation between vowel and consonant durations unlike adults. Moreover, child vowels are longer in duration when compared to the adult vowels. Surprisingly, between the adult and child vowels, no difference was observed in mean pitch and mean intensity values. The most prominent difference between child and adult laughter is observed in vowel quality where children's F1 values of laughter vowels are relatively higher than adult's. The consonantal resonance in children is similar to their vowels. However, in adults, the consonant resonant frequencies are much higher than the vowel resonances. Therefore, while children may employ more extreme placements of jaw or tongue they have relatively limited articulatory movement from consonant to vowel when compared to adult laughter. This suggests interesting insights into development of children's speech utterances which need to be explored further.
Comparison of human-supervised and fully automatic formant-trajectory measurement for forensic voice comparison
Authors: Zhang Cuiling , Ochoa Felipe , Enzinger Ewald , Morrison Geoffrey Stewart
Published: October 2011

Acoustic–phonetic approaches to forensic voice comparison often include analysis of vowel formants. Such methods depend on human-supervised formant extraction, which is often assumed to be reliable and relatively robust to transmission-channel effects, but requires substantial investment of human labor. Fully automatic formant trackers require less human labor but are usually not considered reliable. This study assesses the variability within and between four human experts and compares the results of human-supervised formant measurement with several fully automatic procedures, both on studio-quality recordings and transmission-channel degraded recordings. Measurements are made of the formant trajectories of /iau/ tokens in a database of recordings of 60 female speakers of Chinese. As well as directly comparing the formant-measurements results, the formant measurements are also used as input to likelihood-ratio forensic-voice-comparison systems, and the validity and reliability of each system is empirically assessed.
Short and long diphthongs in Hainan Cham
Authors: Thurgood Ela
Published: October 2011

This paper focuses on the acoustic features in the contrast between two pairs of phonemically distinctive diphthongs in Hainan Cham, /ai/ versus /a:i/ and /au/ versus /a:u/. The data from six native speakers of Hainan Cham show that the overall duration of long diphthongs does not statistically differ from the overall duration of short diphthongs. The differences, instead, lie in the durational differences between onsets and offsets. In Hainan Cham, the long diphthong onsets are longer than the short diphthong onsets, while their offsets are shorter. The transition duration does not differentiate short and long diphthongs. In Hainan Cham, it occupies only 25–34% of the duration of the whole diphthong, short or long. Another acoustic feature examined in diphthongs is the range and rate of F2 change. In Hainan Cham, /ai/ is well differentiated from /a:i/: The short diphthong /ai/ has a greater F2 range of change and a faster F2 rate of change than the long diphthong /a:i/. However, /au/ and /a:u/ have very similar F2 rate of change.
Timing differences in read speech and spontaneous conversation: English, Japanese, Korean, and Mandarin
Authors: Brenner Dan
Published: October 2011

Timing and rhythm in language reflect broad auditory properties of languages to which listeners acclimate very early on in acquisition (Nassi etal., 1998, 2000), and are heavily implicated in the differentiation of speech segmentation strategies cross-linguistically (Cutler and Butterfield, 1992; Otake etal., 1993; Saffran etal., 1996; Kim etal., 2008). The rhythmic properties of everyday conversational speech (as compared to read speech or motherese), however, are not well understood. The present work employs several measures developed to summarize rhythmic differences such as %V vs. δC (Ramus etal., 1999) and C-rPVI versus V-nPVI (Grabe and Low, 2002) in order to study the timing variation found in English, Japanese, Korean, and Mandarin (unrelated languages varying in purported “rhythm class”) comparing rhythmic measures during careful read speech and in spontaneous casual conversation. This reveals the effect of highly variable conversational speech on the timing behavior of rhythmically diverse languages.
The production of Spanish–English code-switching
Authors: Piccinini Page E.
Published: October 2011

It is generally assumed that in code-switching (CS) switches between two languages are categorical, however, recent research suggests that the phonologies involved in CS are merged and bilinguals must actively suppress one language when encoding in the other. Thus, it was hypothesized that CS does not take place abruptly but that cues before the point of language change are also present. This hypothesis is tested with a corpus of Spanish-English CS examining word-initial voiceless stop VOT and the vowel in the discourse marker “like.” English VOTs at CS boundaries were shorter, or more “Spanish-like,” than in monolingual utterances. Preliminary results suggest Spanish VOTs at CS boundaries were shorter than in monolingual utterances, thus even more Spanish-like than monolingual Spanish utterances. The vowel of “like” in English utterances was more monophthongal and had a lower final F2 as compared to “like” in Spanish utterances. At CS boundaries, “like” began similarly to the language preceding the token and ended similarly to the language following it. For example, in a “English-like-Spanishnn” utterance, initial F2 measurements were more English-like but final measurements more Spanish-like. These results suggest code-switching boundaries are not categorical, but an area where phonologies of both languages affect productions.
Acoustic features of English sentences produced by native and non-native speakers
Authors: Chen Yu-Fu , Liu Chang , Jin Su-Hyun
Published: October 2011

Fundamental frequency (f0) contours and power envelopes of English sentences produced by young English-, Chinese-, and Korean-native speakers were measured. Sentences were selected from Hearing in Noise Test (HINT) and recorded from non-native speakers whose US residency within five years. Preliminary results showed that the f0 contours of non-native speakers were similar to those of native speakers, but with greater variation over the time, suggesting that non-native speakers may be able to follow native speakers' vocal pitch contour, but with higher temporal variability. Power envelopes of the sentences will be measured and the relationship between the acoustic features of speech and speech intelligibility will be discussed as well.
The acquisition of voiceless sibilant fricatives in children speaking Mandarin Chinese
Authors: Li Fangfang
Published: October 2011

The current study aims to describe Mandarin-speaking children's acquisition of voiceless sibilant fricatives, /s/, /ʂ/, and /ɕ/, as assessed by acoustics. Forty children, aged 2–5, participated in a word repetition task. The stimuli were fricative-initial words that are familiar to children. Children's speech sound productions were recorded and analyzed spectrally. Two acoustic parameters were obtained: the centroid frequency calculated over the middle 40-ms slice of the fricative noise spectrum and onset F2 frequency, the second formant frequency taken at the onset of the vowel following target fricatives. Centroid frequency indexes where the major lingual constriction is made in the oral cavity and is inversely related to the length of the front resonating cavity during the articulation of voiceless sibilant fricatives. Onset F2 frequency indexes how the major constriction is made and is sensitive to the lingual posture during constriction. These two parameters have been demonstrated to capture adults' fricative distinctions successfully. The results indicated an early separation between /ʂ/ and the other two fricatives in the centroid dimension, and an early separation between /ɕ/ and other two fricatives in the onset F2 dimension, The results suggested that children gradually implement their motor control in different articulation/acoustic dimensions.
Spectral amplitude nonlinearities for improved noise robustness of spectral features for use in automatic speech recognition
Authors: Zahorian Stephen , Wong Brian
Published: October 2011

Auditory models for outer periphery processing include a sigmoid shaped nonlinearity that is even more compressed than standard logarithmic scaling at very low and very high amplitudes. In some studies done at Carnegie Mellon University, it has been shown that this compressive nonlinearity is the most important aspect of the Seneff auditory model in terms of improving accuracy of automatic speech recognition in the presence of noise. However, in this previous work, the nonlinearity was trained for each frequency band of the Mel frequency cepstrum coefficients thus making it impractical to incorporate in automatic speech recognition systems. In the current study, a compressive nonlinearity is parametrically represented and constructed without training, to allow various degrees of steepness and “rounding” of corners for low and high amplitudes. Using this nonlinearity, experimental results for various noise conditions, and with mismatches in noise between training and test data, were obtained for phone recognition using the TIMIT and NTIMIT databases. The implications of the results are that a fixed compressive nonlinearity can be used to improve automatic speech recognition robustness with respect to mismatches between training and test data.
Restoration of intermittent speech signal relying on auditory perceptual capability
Authors: Mizumachi Mitsunori , Horiuchi Toshiharu
Published: October 2011

Speech signals are frequently transmitted through the IP network. In such situation, a packet loss causes a temporal break in receiving speech signals. The intermittent speech signals make speech communication uncomfortable. However, the intermittent speech signal can be heard smoothly under certain conditions, because the brain reconstructs the missing speech packet unconsciously. This auditory illusory phenomenon, that is, the phonemic restoration effect, occurs under severe noisy conditions [Miller and Licklider, 1950]. In short, a speech signal with a heavy background noise, of which signal-to-noise ratio (SNR) is less than 0 dB, overcomes the intermittency in receiving speech signals, although the noisy speech signal makes us uncomfortable in speech communication. In this paper, we propose a speech signal restoration scheme with auxiliary signal processing to positively enhance our phonemic restoration capabilities under less noisy condition. First, we discuss the characteristics of the background noises. Reducing noisiness and enhancing the phonemic restoration effect should be compatible with each other for achieving comfortable speech communication. Second, we propose to predict and reconstruct the principal parts of the missing signal components from peripheral information. Finally, synergistic contribution is discussed between the above considerations. [Work partially supported by NEDO, Japan.]
Modeling noise from underwater vehicles
Authors: Fischer Raymond
Published: October 2011

To predict and control the radiated noise from underwater vehicles can be a complicated task. As opposed to a surface ship with a hull surrounding the machinery sources, these vehicles have multiple acoustic sources in direct contact with water. Any surrounding hull-type structure, excited by the source, then also radiates into the acoustic media. This paper discusses these potential sources, e.g., propulsors, motors, pumps, controllers, high-pressure air system, and electronics. The transmission path from the sources to the ocean also needs to be defined and understood. Airborne, fluidborne, and structureborne paths exist for most vehicles and they are often cross-coupled. These vehicles can also have exotic hull materials whose radiation characteristics are quite different from the standard metallic hulls. Accurate models can identify which sources and paths are important and over which frequency ranges. To reduce the signature in an optimal manner and diminish the adverse impacts on space, payload, and cost of typical treatments, one must have a good understanding of the process of modeling the radiated noise of a vehicle. This paper discusses these critical factors.
Underwater gliders as acoustic receiving platforms
Authors: Dossot Georges A. , Miller James H. , Potty Gopu R. , Moore Kristy A. , Glenn Scott , Lynch James F.
Published: October 2011

Acoustic data were collected on a single hydrophone towed by a Webb Slocum glider deployed by Rutgers University, during the shallow water experiment (SW06), on the continental shelf, of New Jersey. The geometry of the experiment provided for adequate recording of the 224 and 400 Hz tomography sources. A follow-up study of the New Jersey Tuckerton Field Station provided a rudimentary noise analysis showing the glider's capabilities as an acoustic receiving platform. The glider's saw-tooth glide profile allows for vertical sampling of the water column with periodic surfaces for GPS fixes and data transfer via satellite phone. The glider provides a low-noise and low-speed platform, potentially enabling detection of low level signals. [Work sponsored by the Office of Naval Research.]
Application of boundary layer suction for reducing hydrophone sensing noise
Authors: Dolder Craig N. , Villanueva Meagan A. , Haberman Michael R. , Tinney Charles E.
Published: October 2011

One of the leading noise sources for hydrophone arrays on moving vessels is hydrodynamic noise which results from the presence of turbulent boundary layers. This ongoing experimental study explores the impact boundary layer suction has on reducing the hydrodynamic pressure fluctuations and thereby increasing the signal to noise ratio for sensing. A custom hydrophone array is used to capture the pressure signatures with and without boundary layer suction under 2D fully developed turbulent boundary layers with momentum thickness Reynolds numbers ranging from 2000–4000. The first generation suction device shows a reduction in noise of up to 50% with moderate suction intensities. The current focus is on observing the effect suction has on the boundary layer velocity field using both single point laser Doppler anemometry and 2D particle image velocimetry. This information will provide insight into how the hydrodynamic structures are being removed and will provide a basis for the development of future optimized suction devices.
Radiated noise measurements in a harbor environment using a vertical array of omnidirectional hydrophones
Authors: Fowler Brian , Barber Christopher
Published: October 2011

Measurement of the radiated noise of a ship or submerged vessel in shallow water is complicated by the presence of multiple surface and bottom reflections, requiring that environmental effects on propagation either be minimized in the measurement or accounted for in the result, or perhaps both. In a harbor environment, there are additional sources of reflection and noise that may degrade the ability to obtain meaningful measurements. The combination of multiple reflected paths, high background noise, and a possible inability to assume far-field behavior due to a shortened range present a significant challenge to acquiring high confidence measurements of the radiated acoustic field. This work presents preliminary results from a radiated noise measurement test conducted at the U.S. Navy's Acoustic Research Detachment in Bayview, Idaho during summer 2010. A line array of 14 equi-spaced omnidirectional hydrophones was deployed from a barge tied up adjacent to a moored test vessel to obtain radiated noise measurements. A series of test signals was also transmitted through a calibrated acoustic source deployed at various depths in the harbor to evaluate the effectiveness of vertical line array measurements in minimizing reflected path contributions and improving signal-to-noise ratio. Preliminary results and conclusions are presented. [Work sponsored by the Office of Naval Research, Code 331.]
Review of methods for making radiated noise measurements of submerged vessels
Authors: Barber Christopher
Published: October 2011

There are a variety of challenges associated with measuring the radiated noise of surface ships and submerged vessels in order to obtain a measurement and environment-independent parameter such as the far-field equivalent source level. While measurements of large ships and naval vessels have routinely been conducted at deep water test sites in what approximates a far field measurement in a free-field environment, open ocean, fixed range measurements are not always practical for smaller vessels and particularly for autonomous or unmanned undersea vehicles. This presentation provides a brief review of several existing methodologies and examines some of the specific challenges associated with obtaining high quality estimates of vessel radiated noise associated with various methods and measurement scenarios.
Navigation and sonar applications of an acoustical spiral wave front beacon
Authors: Dzikowicz Benjamin R. , Hefner Brian T. , Leasko Robert A.
Published: October 2011

A spiral wave front beacon consists of a transducer whose phase depends on the azimuth at which it is received and a reference transducer whose phase does not. [J. Acoust. Soc. Am. 129:(6), 2011]. A spiral wave front can be produced by using a cylindrical transducer whose radius advances by one wavelength over one revolution, or by phasing a circular array of elements out of phase such that they generate a spiral wave front. Several experiments using both of these types of beacons are carried out at the Navy's Dodge Pond facility in Connecticut. This facility provides a range of environments where the robustness of the signals in multipath and reverberation can be tested. Navigation experiments are carried out using a remotely operated USV equipped with a hydrophone and a data acquisition system which triggers upon receipt of an incoming signal. The vehicle is also equipped with a differential global positioning system (DGPS) receiver to determine its exact position. Several types of outgoing signals are employed. The beacons are also tested for use in passive and active sonar applications where the phase advance between the transducers gives an indication of direction. [Work supported by the Office of Naval Research.]
A robust phase gradient bearing estimation algorithm for a tri-axis cross-dipole acoustic array, with application to a long range autonomous underwater vehicle homing and tracking system
Authors: Lucas Carmen , Heard Garry , Pelavas Nicos , Fleming Richard
Published: October 2011

A bearing estimation algorithm was developed as part of a long range acoustic bearing (LRAB) homing system implemented on an autonomous underwater vehicle (AUV). A tri-axis cross-dipole acoustic array with seven digital hydrophones was developed and mounted in the AUV for the homing system. The Phase Gradient algorithm was implemented on the vehicle's Acoustic Homing and Localization System processor and run in real-time. The algorithm was designed to estimate the bearing and elevation angles to a continuous wave (CW) signal from a beacon source. The algorithm directly estimates the three Cartesian components of the incoming signal wave-vector from estimated cross-spectra between the hydrophone elements. The algorithm is robust against hydrophone failure, and every hydrophone in the array is used to estimate each component of the wave-vector. In this paper, the theoretical development of the Phase Gradient algorithm is presented, as well as the results from real applications of the algorithm as part of an AUV homing and tracking system.
Linear drift error for cornerstone autonomous underwater vehicle
Authors: Pelavas Nicos , Heard Garry J. , Lucas Carmen E. , Clark Derek
Published: October 2011

Autonomous underwater vehicles (AUVs) have a promising future in their use of collecting bathymetric data in remote regions of the Arctic Ocean. In accordance with the United Nations Convention on the Law of the Sea, Defence Research & Development Canada Atlantic has partnered with Natural Resources Canada (NRCan) and Department of Fisheries and Oceans to use AUVs in support of Canada's Arctic claim. In this article, we investigate the AUV linear drift error that accumulates as a result of a misalignment between the Inertial Navigation Unit and the Doppler Velocity Log. Data collected during the 2010 Cornerstone Arctic field trial is used to quantify the linear drift error associated with one of the AUVs. The linear drift error was determined to be 0.67% to stern and 0.21% to starboard, and this result was then applied to correct the track for the AUV survey mission.
Modeling a spiral wave front source in an ocean environment
Authors: Hefner Brian T. , Dzikowicz Benjamin R.
Published: October 2011

A spiral wave front source generates a pressure field which has a phase that depends on the azimuthal angle at which it is measured [J. Acoust. Soc. Am. 129(6), (2011)]. This type of source can be used in conjunction with a reference source to form a navigation beacon. A remote receiver can determine the direction to the beacon from the phase difference between the pulses transmitted from each of the sources. To determine the accuracy of this navigation technique, it is necessary to model the output of the spiral wave front source in ocean environment. To this end, the spiral wave front analogue of the acoustic point source is examined and is shown to be related to the point source through a simple transformation. This makes it possible to transform the point source solution in a particular ocean environment into the solution for a spiral source in the same environment. This transformation is applied to simple cases, such as reflection from the sea surface, as well as to the more general case of propagation in a horizontally stratified waveguide. [Work supported by the Office of Naval Research.]
Recent developments in the seismo–acoustic parabolic equation
Authors: Collins Michael D.
Published: October 2011

The development of the seismo–acoustic parabolic equation is currently proceeding in several directions. Since the stability of the parabolic equation is an issue for problems involving relatively thin elastic layers, special rational approximations are being designed for problems involving ice cover. Range dependence has previously been treated with approaches based on single scattering, energy conservation, and coordinate changes that are of limited use for certain cases. For test problems involving gradual range dependence (a convenient reference solution is available in this limit), promising results have been obtained with a single-scattering approximation that conserves quantities across a vertical interface in a mean sense. One of the advantages of this approach is that its simple physical interpretation facilitates generalizing to different cases, such as problems involving sloping fluid–solid interfaces and anisotropic and poro-elastic layers. [Work sponsored by the Office of Naval Research.]
Discrete transparent boundary conditions for parabolic equations
Authors: Pannatoni Ronald F.
Published: October 2011

There are simple algorithms for constructing transparent boundary conditions (TBCs) for a partial discretization of the basic parabolic equation that is known as a “semi-discrete” parabolic equation. This equation and some of these algorithms are reviewed. Solutions of a semi-discrete parabolic equation in a long rectangular strip subject to TBCs at the long edges of the strip are then considered. These solutions can be computed accurately and efficiently with a pseudospectral method that is based on expansions in Chebyshev polynomials. It is beneficial to combine this method with a conventional split-step FFT solution of a parabolic equation subject to Neumann boundary conditions at the long edges of the strip. This hybrid approach will be called the “decomposition method.” It is demonstrated in a computation of radiation modes from the termination of a truncated nonlinear internal gravity wave duct in a shallow water area.
Seismo-acoustic propagation near thin and low-shear speed ocean bottom sediments
Authors: Collis Jon M. , Metzler Adam M. , Reitz Paden , Rahman Rezwanur
Published: October 2011

Accurate and efficient parabolic equation solutions exist for complex propagation environments featuring elastic and porous elastic sediment types. Because of numerical stability issues, areas of concern have been with thin and low-shear wave speed sediments. In certain situations, both of these common features of the seafloor can make obtaining an accurate solution difficult. At low frequencies, layers of this type can be treated as a massive interface between the water and higher-shear speed sediment basement layers. To satisfy interface conditions across the layer, Rayleigh jump conditions are imposed [F. Gilbert, Ann. Geofisica XL, 1211 (1997)]. This approach is only valid for a single layer, but is able to handle shear wave speeds as they tend to zero. In this talk, a massive elastic interface parabolic equation implementation is benchmarked along with classical bottom treatments to quantify the effects of ocean acoustic propagation over thin sediment layers. It is demonstrated that in certain situations, it is sufficient to consider the thin layer as part of adjacent, thicker layers.
Sonar propagation modeling using hybrid Gaussian beams in spherical/time coordinates
Authors: Reilly Sean M.
Published: October 2011

This paper defines a new undersea acoustic transmission loss model that is optimized for real-time, sonar simulation/stimulation systems in littoral environments. The ray solutions to the eikonal equation are computed in latitude, longitude, and altitude coordinates to match wide-area environmental databases. Hybrid Gaussian beam techniques for transmission loss calculation are used to extend the applicability of ray theory to lower frequency regimes. Numerical integration of the wave equation is performed in the time dimension to support broadband signal modeling. This 3-D approach also supports out-of-plane reflection from the ocean bottom. This paper derives the eikonal solution from first principles to ensure a complete understanding of the coordinate system's impact.
Underwater acoustic propagation in Arctic environments
Authors: O'Hara Christie A. , Collis Jon M.
Published: October 2011

Developments in underwater acoustic modeling for the Arctic have been limited due to the complicated nature of the polar extreme. In Arctic regions, the sound speed minimum occurs at or near the ice-covered surface. The upward refracting sound speed profile causes any long-range propagation to repeatedly interact with the ice cover. This paper presents an overview of the derivation of a 2-D normal mode propagation model to the range-independent wave equation for a source and receiver in the water column. To more accurately model the Arctic ocean acoustic environment, we consider a modified Pekeris waveguide. As with the Pekeris waveguide, the bottom is considered as an infinite fluid halfspace and the top is considered to be a fluid layer of finite thickness overlying the water column. Results will be benchmarked against a fluid parabolic equation solution. An application is discussed as a means to track marine mammals using received signals.
Perth-Bermuda revisited again: Global adiabatic mode parabolic equation results
Authors: Heaney Kevin D. , Campbell Richard L.
Published: October 2011

In 1960, a set of explosives were detonated off the coast of Perth Australia, and multi-pulse receptions were recorded from moored hydrophones off of Bermuda. The Perth-Bermuda experiment demonstrated the capability of trans oceanic acoustic propagation. The two-pulse arrival, separated by approximately 25 s, was explained by Heaney, etal. (JASA, 90(5), 2586–2594) in terms of two disparate paths: a northern path refracting off islands in the southern Indian Ocean and the other refracting off the shelf-break on the coast of Brazil. In this paper a global adiabatic mode-parabolic equation hybrid model is used to compute the multi mode, broadband full-field pressure response from Perth to Bermuda. The PE field demonstrates that Bermuda is in the acoustic shadow of the refracted geodesics, yet observations of arrivals were made. PE results demonstrate that two significant scattered paths, one to the north passing by the Cape of Good Hope and one to the south, passing by the coast of Brazil yield strong strong arrivals, confirming the results of Heaney etal.
Detection performance modeling and measurements for convergence zone (CZ) propagation in deep water
Authors: Heaney Kevin D. , Campbell Richard L. , Murray James J. , D'Spain Gerald L. , Baggeroer Arthur B.
Published: October 2011

A novel parabolic equation algorithm in the C programming language has been developed based upon the RAM model. This model (CRAM) permits modeling of the full-field sonar equation to estimate towed array performance of the detection of quiet targets in a dynamic environment with both environmental range dependence and source/receiver kinematics. During an experiment in the northern Philippine Sea in 2009, a ship towing Penn State's Five-Octave Research Array (FORA) was towed at various depths in a star pattern about the station-keeping source ship, thereby sampling the first CZ in range, depth, and azimuth. Measurements and modeling of the CZ arrivals will be compared. A simple detection processor is applied to the CZ receptions. Comparison of passive ASW performance modeling results with measurements will be made. One of the primary science issues in the statistics associated with probabilistic detection is the time between independent samples, or the sample-to-sample correlation. This will be evaluated from the data for a portion of the test where the receiver was towed in an arch-fixing the source–receiver range for several hours. [Work supported by ONR.]
A livingscape approach to characterize urban historical places
Authors: La Malva F. , Astolfi A. , Bottalico P. , Lo Verso V.R.M.
Published: October 2011

The quality of life concerned with open spaces has more and more become an essential part of urban culture. The evaluation of environmental effects as perceived by people is primarily a subjective issue, rather than being simply based on objective parameters. This paper presents an approach called livingscape, used to assess the quality of urban spaces. It consists of analyzing and correlating psychometric tools to measure the perception of environmental quality with different aspects related to the urban blight (both in architectural and environmental terms) and objective investigation of environmental quality through the measurement of acoustic, visual, thermal, and IAQ physical parameters. Livingscape data were collected in 13 key-spaces of St. Salvario, an historical district in Turin (Italy), during summer 2010 and winter 2011, selected based on an historical analysis to characterize the past and present district soundscape and subdivided in nodes, paths, and edges. The subjective environmental perceptions are delineated through the analysis of the questionnaires submitted to the users of the area, outdoor. Objective measures (acoustical, lighting, and thermal parameters) were combined to subjective responses, thus providing a more complete key-spaces characterization. The investigation aims to describe the changes in the key-spaces characterization from 19th century to nowadays.
How the soundscape approach enlightens the knowledge about the feeling of safety in urban spaces: A matter of networking and interdisciplinarity
Authors: Voigt Kay Sebastian , Schulte-Fortkamp Brigitte
Published: October 2011

In a current project on dynamics of urban safety and its arrangements funded by the Federal Ministry of Education and Research, Germany http://www.dynass-projekt.de/projekt-dynass/ Dynamische Arrangements städtischer Sicherheitskultur/, the Soundscape approach is one of diverse approaches to investigate areas of different cities with respect to the perception and production of safety in such environments. As to the perception of safety, areas as well as its production special attention will be given to the reconstruction of decisive factors. The current status of the international standardization process of the ISO/TC 43/SC 1/WG 54 and the contribution of the COST network are used here as the basis to improve procedures and measures in the applied Soundscape approach. Moreover, this paper will discuss the Soundscape research as an interdisciplinary approach and in an interdisciplinary approach with regard to investigations upon safety management in urban areas. First results give hints to the importance of the acoustic, visual, and social structures of an area in the face of the Soundscape procedure.
Water features and acoustic diversity of urban parks
Authors: Axelsson Osten , Nilsson Mats E.
Published: October 2011

Water features are well-acknowledged in architecture and urban planning for their visual characteristics. But, how do water features contribute to acoustic diversity and soundscape quality? Visitors in an urban park were recruited to complete a questionnaire on how they perceived the park including its soundscape. Meanwhile, the soundscape was manipulated by turning a fountain on or off at irregular hours. The fountain sounds had a positive effect on soundscape quality in an area close to the fountain, by masking background road-traffic noise. The fountain sound also masked other natural sounds, which may have a negative influence on acoustic diversity and soundscape quality. In addition, some participants may have mistaken the fountain sounds for distant road-traffic noise. Hence, when introducing a water feature in an urban park it is necessary to consider the acoustic characteristics of the water sounds, as well as the placement of the water feature.
What you call it does matter: A vocabulary for active acoustics
Authors: Graffy Kurt M.
Published: October 2011

Active acoustics (Electronic Architecture) systems have reached a maturity in terms of their acoustic performance which makes them a viable option for multi-use venues as well as renovations of existing facilities. However, the awareness on the part of owners and facilities regarding the capabilities and potential acoustic benefits of such systems is still developing. More significantly, the corresponding level of awareness for designers and architects, which active acoustics can actually represent options for how architectural, structural, and building service designs may proceed, is even less developed. At this intersection of past techniques versus current abilities, we are in need of a common vocabulary for active acoustics; a common vocabulary to interact with the design team, a common vocabulary to assist venue operators and owners understand the benefits, and a common vocabulary to interact with the musicians and artists in tuning and configuration. The presentation references some recent projects utilizing active architecture primarily focused on the interaction with the design team and subsequently with the artists, and the development of a common language as the projects moved forward.
Working with musicians to increase low-frequency performance of an active acoustic system in a music practice room
Authors: Freiheit Ron
Published: October 2011

To enhance the performance of an active acoustic system for music practice rooms, a new speaker was developed with extended low-frequency response. To better understand the performance desired from certain musicians, a small number of cellists provided observations and opinions about what environment was most pleasing to them, specifically related to the expanded low-frequency response of the active system. A system was developed that allowed the tuning of the low-frequency response to better ascertain at which point it was optimized and below or above which very little improvement was noted. Once these parameters were optimized, design criteria for the speakers were determined. Also discovered during this research were challenges musicians faced in discriminating between the direct sound and active sound field.
Indoor outdoor acoustics: Active acoustics at the New World Center, Miami Beach Soundscape
Authors: Vogler Frederick R. , Pellowe John , Ellison Steve
Published: October 2011

The Frank Gehry designed New World Center is home to the New World Symphony in Miami Beach, FL. This facility includes an intimate 756 seat concert hall and is used as a training platform both for symphonic conductors and musicians. The adjacent park uses an active acoustics system to allow a similar number of people in the park to simultaneously experience the indoor concert experience in an open air environment. The immersive sound of the reproduced concert experience is accompanied by a 7000-square-foot projection wall that carries live video of the performance. The system captures the natural acoustic of the concert hall using microphones distributed throughout, and these signals are processed and then transmitted to the park utilizing a set of 160 distributed loudspeakers. The successful design, commissioning, and tuning of the system relied on a team approach between the architect, consultants, manufacturer, installer, and venue operators. Scope within the team is explored, challenges revealed, and suggestions offered to help ensure the success of new multi disciplinary ventures such as this. Similarities and differences to a surround sound broadcast transmission of the Los Angeles Philharmonic are also reviewed.
The effect of reverberation enhancement on the diffusion of the sound field
Authors: Hopper Hugh , Thompson David , Holland Keith
Published: October 2011

Reverberation enhancement is a technology which allows the reverberation time of a room to be increased. It is important to consider the effect of this technology on the other measurable attributes of the room response. The spatial variation of steady state sound pressure level and reverberation time within the room can be used to measure the extent to which the room approximates a diffuse field. A theoretical value of these quantities can be predicted for an ideal diffuse field, and the ratio between the measured and theoretical values gives a normalized measure of the diffusion of the sound field. This work investigates the changes in these measures when reverberation enhancement is applied to a room. Experimental results have shown that the normalized measures of diffusion increase with the introduction of reverberation enhancement. This implies a reduction in the homogeneity and isotropy of the sound field which may be perceived as a reduction in subjective quality.
Variable acoustics at hauppauge high school
Authors: Riedel Richard F.
Published: October 2011

The author will discuss how variable acoustic solutions were used to solve room anomalies and provide a means to control room size. Once plagued by a significant rear wall reflection that interfered with stage musicians' timing, due to its later arrival time, the author will explain how a unique custom designed retractable acoustical diffuser reduced this problem. Another recurring issue in the space was the need to reduce the size of the seating area, normally 1100 seats, to one which provided a more intimate setting for dramatic presentations, which were normally not attended by large audiences. Using a commercially available acoustical product, the issue was solved and a means provided to alter the room's acoustical environment. This paper presents details about the methods used to provide variation to the room's acoustics and cites specific measurements of the space with and without the variable acoustical elements.