bluuebunny/crossref_metadata_2025 huggingface dataset:
Environmental influences on acoustic communication in frogs
Authors: Narins Peter M.
Published: October 2011

Many species of animals, including man, face the formidable task of communicating in naturally noisy environments. The effects of noise on both the calling behavior of frogs and the temporal, and spectral filtering ability of the amphibian auditory pathway are discussed. Moreover, the role of spectral, temporal, and spatial separation in minimizing background noise masking will be examined. Behavioral evidence is presented suggesting that environmental noise may act as a strong selective force in sculpting the communication systems of two species of Old World frogs. One torrent frog (Odorrana tormota) calls frequently from vegetation along fast-flowing mountain streams in Central China. These streams produce high-level, broadband noise spanning the human hearing spectrum. In addition to the high-pitched audible components, the males' calls contain prominent ultrasonic harmonics. Another frog, Huia cavitympanum, lives in a very similar habitat in Borneo. Unlike O. tormota, Huia can modulate its call spectrum to produce purely ultrasonic calls. It is thought that the upward shift of the call frequencies and the upper limit of sensitivity of both O. tormota and H. cavitympanum are responses to the selection pressures from their noisy habitats. [Work supported by NIDCD DC-00222, Paul S. Veneklasen Research Foundation, UCLA Academic Senate (3501).]
Chorussing in delphinids
Authors: Janik V. M. , Simard P. , Sayigh L. S. , Mann D. , Frankel A.
Published: October 2011

The evolution of communication is strongly influenced by the social structure of animals. Here, we report how a group of offshore bottlenose dolphins in the Gulf of Mexico used chorusing of the same whistle type, while no such behavior was observed in inshore populations of the same species. We recorded 166 whistles from a group of 6 bottlenose dolphins in the Gulf of Mexico, 19 nm from the Florida coast. In an examination of the timing of whistle production, we found nine sequences in which there was considerable overlap (i.e., >50%) between whistles and another eight sequences with almost perfect overlap of the same whistle type produced by two to six animals simultaneously. Such synchrony was not expected by chance. To investigate how unique this behavior was, we also analyzed 300 h of recordings of inshore bottlenose dolphins in Florida and Scotland. In these data we found three non-significant cases of two animals showing >50% overlap. Thus, chorusing appears to be absent in inshore animals. Our data suggest that offshore bottlenose dolphins live in closed social units, which could be the result of enhanced difficulties in maintaining contact if home ranges are large.
Tracking dolphins using long-term autonomous acoustic recorders
Authors: Wiggins Sean M. , Gassmann Martin , Fraiser Kaitlin , Hildebrand John A.
Published: October 2011

Tracking marine mammals over long periods can provide information on their movement patterns including base-line behavior and responses to natural and anthropogenic stimuli. Autonomous acoustic recorders provide a cost effective and portable means of tracking these sounds over long periods, but until recently these devices have been restricted to tracking low-frequency large whales because of limited recording capabilities. In this paper, we will present long-term, passive acoustic tracking of high-frequency dolphin whistles and clicks using autonomous hydrophone recording arrays with kilometer- and meter-scale apertures.
Dale (Van) Holliday was so much more than a scientist
Authors: Houser Dorian S.
Published: October 2011

Dale (Van) Holliday is well known for his acoustic studies of ocean life over a scale from plankton to mysticete whales. Van was a globally acknowledged expert valued for his participation in national and international councils governing ocean issues. Multiple times he was awarded high honors, such as the Prix d'Excellence and the Silver Medal in Acoustical Oceanography. More importantly, Van was a man of faith and no respecter of persons; he unselfishly gave of his time and knowledge and treated both students and career scientists with the level of respect due an individual. I was professionally mentored by Van and worked alongside him as a church deacon. As a deacon, I observed Van's compassion—the numerous hospital trips to visit the sick, the visitations of the home bound, and the phone calls to just “check in.” His interest in people spilled into his professional relationships, particularly with young and emerging scientists whom Van joyfully assisted and advised. I, and numerous others, have and continue to benefit from our friendship and professional relationship with Van. He was truly unique. He will be missed, but not forgotten, as his science and investment in people will remain impactful for decades to come.
Broadband active acoustic sensing of fish and zooplankton in the kilohertz to megahertz range: Pursuing Van Holliday's vision
Authors: Stanton Timothy K. , Chu Dezhang , Lavery Andone C.
Published: October 2011

Van Holliday had a vision for sensing marine organisms with active acoustics over a very wide range of frequencies. This inspired us at the Woods Hole Oceanographic Institution, Woods Hole, MA, to conduct a series of measurements, both in the laboratory and in the ocean, and associated modeling, over the range of 1.5 kHz to 3 MHz over the past 23 years. The organisms were as small as millimeter-size copepods and as large as 20-cm herring and squid. Broadband acoustic scattering measurements were conducted in the laboratory as a function of frequency (24 kHz 3 MHz) and angle of orientation (0–360 deg) of many species. Instruments were developed to measure broadband acoustic scattering in the ocean over the range 1.5 kHz 1.2 MHz with some gaps. Scattering models, based on the laboratory data, were also developed for several major anatomical groups of organisms and spanned a range of complexity, from low-resolution models that account only for length, width, and general shape to high resolution models that account for shape of the body and heterogeneities within the body in three dimensional at fine scale as well as including roughness. In this presentation, we review the laboratory measurements and scattering models, as well as development of the broadband ocean instruments and their use at sea.
Active acoustic examination of the diving behavior of murres foraging on patchy prey
Authors: Benoit-Bird Kelly J.
Published: October 2011

Van Holliday used sound to study nearly every type of organism living in the ocean, contributing to our understanding of acoustics as well as marine ecological processes. To honor Van, I will talk about the one animal group that I could not find in his long publication list—seabirds. We combined visual observations of murres with active acoustics, fish trawls, zooplankton net tows, and hydrographic measurements in the area surrounding breeding colonies in the southeastern Bering Sea. We detected thousands of unique acoustic targets that were strongly correlated with the number of visually detected murres, providing a new tool for quantitatively studying the foraging ecology of diving birds. Diving murre abundance was related to the combined availability and vertical accessibility of squid, krill, and pollock. Individual krill patches targeted by murres had higher krill density and were shallower than mean values but were similar in total krill abundance and overall size. Murres found outside of krill showed a depth distribution similar to that of juvenile pollock. The high proportion of diving murres in aggregations and their consistent inter-individual spacing support the hypothesis that intra-specific local enhancement may facilitate foraging in these predators.
Multifunctional composite materials and structures: A brief review
Authors: Gibson Ronald F.
Published: October 2011

Recent advances in the area of multifunctional materials and structures are reviewed. Interest in this area has been driven by the need for systems that simultaneously perform structural and nonstructural functions. Multifunctional materials are by nature composite materials and new nanoreinforcements, in particular, have made it possible to achieve simultaneous improvements in properties such as stiffness, compression strength, damping, electrical conductivity, and fracture toughness. For example, among the most important nonstructural functions that a structure may need is electrical conductivity, but many composites have poorly conducting polymer matrix materials. However, very small concentrations of carbon nanotubes or other conducting nanoreinforcements in polymers lead to disproportionately large improvements in the electrical conductivity of the nanocomposite. Recently developed composites with piezoelectric structural fiber reinforcements are capable of vibration control, damping, energy harvesting/storage, or structural health monitoring. Recent research has also demonstrated the feasibility of self-healing polymers and polymer composites based on the use of a microencapsulated healing agent and a catalyst for polymerizing the healing agent. Structurally integrated electronics such as batteries for energy storage are another recent application of multifunctional structure design. Other important nonstructural functions in multifunctional composite structures include electromagnetic interference shielding, optical transparency, and thermal conductivity.
Estimation of the conditional variance of a broadband source signal employing a repetition code through shallow water waveguides
Authors: Pfetsch Michael , Gendron Paul
Published: October 2011

A repetition code can be employed as a computationally fast suboptimal means to exploit available time-bandwidth product for improved bit error rate performance. Applications include synthetic aperture communications. Underwater acoustic response functions can vary over the duration of the transmission and thereby degrade system performance. A measure of precision of estimation of the source signal is the source posterior variance given the receiver pressure field time series. Presented here is the computation of the covariance of a source signal accounting for the covariance of the acoustic response function. A Gibbs sampling scheme is employed as a computational method to computing these variances to an acceptable precision. The resulting posterior variance as a function of SNR gives insight into the contributing phenomena that impart ambiguity in synthetic aperture communications through underwater acoustic channels. The method is tested on the very shallow water environment of Keyport WA at a center frequency of 20 kHz.
Comparison of particle filtering and extended Kalman filtering for acoustic-based tracking of low-flying aircraft
Authors: Frazier Wm. Garth , Williams Chad
Published: October 2011

This presentation summarizes a comparative study of particle filtering and extended Kalman filtering applied to acoustic-based tracking of high-speed, low-flying aircraft. A distributed network of small acoustic arrays, each reporting real-time azimuthal bearings and elevation angles to acoustic sources to a central processing unit, are synthesized into real-time three-dimensional tracks. The primary challenge of the problem is the significant propagation delay between the source and the receivers. Both tracking methods are applied to simulated and field test data and reveal nearly equivalent tracking performance in all cases as along as a sufficient number of particles are utilized. Computational requirements of the extended Kalman filter are significantly less than the particle filters.
Passive sonar tracking using sequences of received signal amplitude fluctuations: Dependence on environmental sampling
Authors: Culver R. Lee , Bissinger Brett E. , Sell Alex W.
Published: October 2011

We have developed a passive sonar tracking algorithm that makes use of variations in the amplitude of the signal received from a source in motion. Originally the likelihood function (probability density function (pdf) of received signal amplitude for a given source location) was calculated by Monte Carlo sampling of the environmental variables and running the acoustic propagation model to predict transmission loss (TL). For each possible source location, the pdf of TL was constructed. To calculate the posterior pdf using received signal amplitude data, Bayes' rule was used sequentially such that for each possible source location, the likelihood function evaluated at the value of the new received amplitude was multiplied by the prior probability associated with that source location. This approach depends fundamentally on how the environment is sampled and on the acoustic propagation model. More recently, the likelihood function has been expanded into the joint pdf of sequences of received signal amplitudes. The environment sampling and use of the acoustic propagation model are the same, but now the likelihood functions are multidimensional. Implications for environmental sampling and selecting the proper model order are discussed. Work supported by the Office of Naval Research Undersea Signal Processing.
Importance-based sampling for porous material physical parameter estimation
Authors: Fackler Cameron , Xiang Ning
Published: October 2011

Bayesian inference is applied to the problem of determining the physical parameters of a rigid-frame porous material. Such materials may be characterized by the parameters of flow resistivity, porosity, and tortuosity. The Biot-Allard and Attenborough models predict the propagation of sound in rigid-frame porous materials by modeling the characteristic impedance and propagation coefficient of the material in terms of these physical parameters and a shape factor. In this work, model-based Bayesian analysis is formulated to estimate the values of these parameters from experimental measurements of the characteristic acoustic impedance or propagation coefficient of a material under test. Importance sampling and related methods are used in the parameter estimation procedure as Monte Carlo approaches to characterize the posterior probability distribution which is used to represent the likelihood of parameter values. To increase the efficiency of the sampling, adaptive strategies are employed to extend the classical importance sampling. This analysis provides quantitative estimates of the parameter values as well as estimates of the uncertainty associated with each parameter and the interrelationship between parameters.
Numerical model of nonlinear acoustic wave propagation in seabed
Authors: Khan Rana Arslan A. , Ellis Grant A.
Published: October 2011

In this study, a combination of two fundamental frequencies f1=485 KHz and f2 = 515 KHz. The source transducers are placed on the surface of the sand 25 cm above the bottom and 20 cm below the water surface in the tank of dimension 74 × 47 × 43.5 cm simulating a seabed with sand of maximum particle size of 5 mm. Burger's equation is the simplest model for describing the second order nonlinear effects in the propagation of high amplitude plane waves and, in addition, the dissipative effects in media. Typically, the interactions of two acoustic waves at a discontinuity in a dispersive but homogeneous medium will generate harmonics and intermodulation terms. This is numerically modeled in Matlab using the finite difference time domain method with Neumann boundary conditions and practically verified with measurements from the tank. The measured and simulated results have shown significant agreement with the theory. For instance, second order intermod term show 2 dB decreases in amplitude for 7 mm increase in thickness at constant density of plywood. Also if the thickness is kept same, e.g., 5 mm, there is 10 dB drop in same intermod term for change in density from plywood 550 kg/m3 to copper 8930 kg/m3.
Design guidelines for rooms used for music, speech, and teaching
Authors: D'Antonio Peter , Nocke Christian
Published: October 2011

Good architectural acoustic design requires an appropriate combination of absorptive, reflective and diffusive surfaces, providing attenuation, redirection, and uniform scattering. Since the terms acoustical and absorptive have become synonymous in common parlance, education of the architectural design community is needed to understand the use of reflective and diffusive surfaces in spaces used for speech, music rehearsal and performance, and teaching. For example, in speech and teaching rooms, where the signal to noise ratio and associated intelligibility are the central issues, designs must not only lower the noise with absorption and isolation but also passively increase the signal with diffusion/reflection. In music education and rehearsal spaces, absorptive low frequency and volume control are important, but reflection/diffusion is equally important for ensemble, tone production and intonation control. In an effort to develop design guidelines, we will review the German standard DIN 18041 on “Acoustic Quality in small and medium sized rooms” (1968, 2004), which standardizes performance objectives in rooms with a volume up to 5000 cbm used for music, speech, and teaching. A frequency and volume dependent suggestion for the reverberation time will be presented as a function of the volume index and examples will be provided.
On a variable broadband absorption product and acceptable tolerances of reverberation times in halls for amplified music
Authors: Adelman-Larsen Niels Werner , Dammerud Jens Joergen , Thompson Eric R.
Published: October 2011

Previous studies have shown that what distinguishes the best from the less well liked halls for pop and rock music is a short reverberation time in the 63, 125, and 250 Hz octave bands. Since quite long reverberation times in these frequency bands are needed in order to obtain warmth and enough strength at classical music concerts, variable acoustics must address these frequencies in order to obtain desirable acoustics in multipurpose halls. Based on the results of a previous study of Danish rock venues as well as reports from three newly built halls, acceptable tolerances of T30 were investigated. The results suggest that T30 can be at least 1.8 times as long in the 63 Hz octave band as in the 125 Hz band and attain values of +/- 15% at higher frequencies compared to the previously determined values. A variable broadband absorption product is also presented. Absorption coefficients are approx. 0.8 in the 125, 250, and 500 Hz bands, 0.6 at 1 kHz and decreasing at higher frequencies, and in the 63 Hz band when in the ON position. In the OFF position the product attains absorption values between 0.0 and 0.2.
The practical effects of mixing in an environment closely resembling a home listening environment
Authors: King Richard , Leonard Brett , Sikora Grzegorz
Published: October 2011

Two traditional philosophies exist when considering recording studio control room design: the method of closely replicating the listening environment of the consumer, quite often the typical living room, as juxtaposed to the idea that the control room should be uniquely suited toward color-free critical listening. While both of these design philosophies have had their proponents and detractors, very little data have been gathered to show the merits or drawbacks of either when used for critical recording and mixing work. A novel method of task-based testing is developed to determine what, if any, affects can be attributed to particular aspects of control room designs. The method employs highly trained recording engineers and producers to provide real-world feedback on the makeup of a control room's sidewalls. By having these trained subjects to perform basic mixing tasks while altering the reflectivity and diffusiveness of the sidewalls, the effects of these isolated acoustic features are determined. Data showing the final balance levels, as well as total elapsed time per trial, are recorded from more than 20 expert subjects. Despite strong differences in lateral reflected energy, most subjects were able to perform their task with relatively little variance.
Statistics of echoes from mixed assemblages of scatterers with different scattering strengths and numerical densities
Authors: Lee Wu-Jung , Stanton Timothy K.
Published: October 2011

Mixed assemblages are defined to describe the cases in which more than one type of scatterer are present and are randomly located and spatially interspersed among one another in each sonar resolution cell. The probability density functions (pdfs) formed by the echo envelopes in such cases can be highly non-Rayleigh and possess heavy tails. The shape of the pdf curves contains information for characterizing and discriminating the composition of mixed assemblages. A general characteristic-function-based mixed assemblage pdf model is formulated in this study. The model, which takes into account beampattern effects, was validated using numerical simulations. Simulated data of two-component mixed assemblages with different relative scattering strengths, numerical densities, and spatial distributions were used to compare the performance of this new mixed pdf model and the widely used weighted multiple component mixture pdf model. It was found that use of the latter model can lead to orders of magnitude errors in estimating the composition of the mixed assemblages. This study is inspired in the context of acoustic studies of mixed biological aggregations in the ocean, but the theory is generally applicable to other types of mixed assemblages as well.
Spatial variation in the small-scale distribution of juvenile walleye pollock (Theragra chalcogramma) in the southeastern Bering Sea
Authors: McIntosh Neal E. , Benoit-Bird Kelly J. , Heppell Scott A.
Published: October 2011

Juvenile walleye pollock (Theragra chalcogramma) is one of the primary prey items for bird and mammal predators in the Bering Sea and supports a large commercial fishery. An understanding of the abundance and distribution of juvenile pollock is needed to estimate the effects that change in these parameters may have on pollock predators and adult pollock abundance and distribution. During the summers of 2008 and 2009, surveys were conducted in three topographic zones (Middle Shelf, Outer Shelf, and Slope) near the Pribilof Islands in the southeastern Bering Sea. Multi-frequency (38, 70, 120, and 200) acoustic sampling occurred during the entire cruise duration with frequent environmental data sampling (e.g., temperature, salinity, dissolved oxygen, and chlorophyll a fluorescence) and targeted fish tows. These data showed that juvenile walleye pollock were primarily found in clusters of small, dense aggregations giving them a leopard spot appearance in the acoustical output. In both years, juvenile pollock distribution was highly variable on small spatial scales and was related to biological and physical features of the water column. These differences in juvenile walleye pollock distribution are likely to affect the use of habitat by predators and may have implications for future sampling.
Forward scattering at low acoustical frequencies from schools of swim bladder fish
Authors: Raveau Maria Paz , Feuillade Christopher
Published: October 2011

Low frequency acoustic scattering from swim bladder fish is dominated by the bladder resonance response. At near-resonance frequencies in dense schools of these fish, acoustical interactions between the fish can cause the ensemble scattering behavior to become highly complex. A school scattering model [J. Acoust. Soc. Am. 99(1), 196 (1996)] has previously been developed to incorporate both multiple scattering effects between neighboring fish, and coherent interactions of their individual scattered fields, in order to realistically describe the collective back scattering behavior of fish schools. In this present work, the school scattering model has been extended to investigate the properties of the acoustic field scattered in the forward direction. In this region, the scattered field and the incident field must be added coherently to obtain the total field. As in the case of back scattering, the field displays marked frequency dependent affects, which are caused by different combinations of the packing density, structural configuration, and resonance frequencies of the individual fish in the school. The results give new insights into the evolution of the acoustic field as it propagates through the school, and the scattering of sound from the incident beam. [Work supported by ONR.]
Acoustic cross sections and resonance frequencies of large fish schools
Authors: Hahn Thomas R. , Diachok Orest
Published: October 2011

A prerequisite for stable inversion of bioacoustic parameters of fish schools from large-scale broadband acoustic observations is a theoretical model that permits fast and accurate calculations of acoustic cross sections and school resonance frequencies based on realistic geometrical models of fish schools. The schools of commercially important species, such as sardines, anchovies, and herring, may be characterized by dense nuclei which contain tens of thousands of individuals (N) with separations (S) on the order of one fish length, and diffuse “fuzz” regions with fish at significantly larger separations. Numerical computations of cross sections and school resonances based on the fundamental equations of multiple scattering for point scatterers for these fish school geometries will be presented. Initial results indicate that bubble cloud frequencies of large schools depend primarily on the average spacing between fish in the nuclei and are essentially independent of school size and shape. It will be shown that theoretical calculations of bubble cloud frequencies (based on previously reported values of N and S of sardine schools) are consistent with Diachok's (1999) observations of the average resonance frequency of sardine schools which were derived from broadband transmission loss measurements. [Work is supported by the Office of Naval Research.]
The evolution of the chirp sonar high resolution sub-bottom sonar
Authors: LeBlanc Lester R. , Mayer Larry A.
Published: October 2011

Professor Steven G. Schock completed his Ph.D. Graduate program of studies under our guidance in the Department of Ocean Engineering, University of RI. The Chirp Sonar research project that supported Stevens graduate studies was proposed to, and supported by ONR (Dr. Joseph Kravitz) in the early 1980s The PIs were Professors Lester Leblanc (Ocean Engineering) and Professor Larry Mayer (Ocean Engineering and Geological Oceanography). Dr. Mayer and I shared a common interest in improving the quality of sub-bottom sonars so as to provide high quality quantitative data for imaging and classification of the sea floor. It was Stevens hard work at programming the signal processing and assembling and building of components to the chirp sonar that greatly contributed to making this program a success. The initial system, housed in two large racks was tested by Steven in Narragansett Bay RI, and unprecedented high resolution images of the sub-bottom seafloor were generated with the data collected for his research program. This paper will present the theory and technological development of the chirp sonar from the early days to the present transitioned systems that are built, improved, and maintained commercially.
Now you see it, now you don't: Chirp imaging of the intermittently shelly shoreface ravinement surface on the inner shelf of Panama City, Florida
Authors: Goff John A.
Published: October 2011

Reconnaissance CHIRP data and vibracores were collected on the inner shelf off Panama City, Florida, in April, 2011, for the purpose of providing seabed characterization for an upcoming ONR acoustic reverberation experiment. The seafloor in this region is part of the MAFLA sand sheet: Holocene shelfal marine sands, 0–5 m thick, extending from Mississippi to the Florida panhandle. Coring often samples a thin shelly layer, associated with the shoreface ravinement, at the base of the sand sheet, followed by finer-grained estuarine sediments. Prior CHIRP data collected by Steve Schock off nearby Fort Walton Beach revealed a highly intermittent reflector that could be correlated to the base of the sand sheet; whether the reflector is caused by the estuarine sediments or the shells was uncertain. The new data also reveal an intermittent basal reflector. Estuarine layering can also be identified, and in parts of our survey area the basal and estuarine horizons are distinct. A core at one of these locations sampled a 0.5-m thick shell layer corresponding to the basal reflector with sand both above and beneath. Shells are therefore likely responsible for this intermittent reflector, and thus themselves likely very heterogeneous in concentration at the ravinement surface.
Contemporary composition for the traditional Lao free-reed mouth organ khaen
Authors: Adler Christopher
Published: October 2011

The khaen is a bamboo free-reed mouth organ prominent among people of Lao ethnicity in Laos and Northeast Thailand and is likely related to ancestors of other Asian free-reed instruments as well as to Western free-reed instruments. New Musical Geographies is an ongoing project by composer/performer Christopher Adler to promote the khaen as a concert instrument in the Western contemporary concert music tradition by encouraging the composition of new works for the instrument. To date, the project includes 17 solo and ensemble compositions by six composers. The diverse compositional strategies of these composers and their relationships to traditional performance techniques and musical structures will be discussed. The presentation will include the performance of selected compositions and examples of traditional-style improvisations.
Analytical vibration model for beam reinforced plate
Authors: Sarda Alexandre
Published: October 2011

Beam reinforced plates are typical components of offshore structures, as used in oil prospecting and production. The typical problem associated with this type of structure is the noise and vibration generated by machines and transmitted through the low damped structure. This vibration can propagate to the accommodation area and generate noise, which can generate stress to the crew. This work leads to develop deterministic models and solutions to be used on vibration levels estimation to beam reinforced plates. These models are used in several configurations, as an example L or T joined plates. The obtained results are then compared with finite element model for solution validating. This model will be used for calculating the coupling loss factors to be used in an statistical energy analysis.
Code division multiple access based multiuser underwater acoustic cellular network
Authors: Yang T. C.
Published: October 2011

A multiple-access underwater acoustic cellular network is considered in this paper using direct sequence spread spectrum techniques similar to the code division multiple access cellular network in RF communications. To keep a reasonable data rate, in view of the limited bandwidth in an underwater (UW) channel, the length and, therefore, the number of orthogonal codes (the number of users) cannot be too large. At the same time, the orthogonality of the codes is severely degraded by the extended multipath arrivals in the UW channel. As a result, communication bit error rate becomes non-negligible when the interferer's signal energy (due to increasing number of users) becomes order of magnitudes higher than the desired signal [Yang et al. JASA 126, 220–228 (2009)]. In this paper, techniques used in multiple-input-multiple-output communications are applied to underwater cellular network for simultaneous communications between the users and the base station, taking advantages of the (rich) spatial degrees of freedom of the UW channel. Simulation and experimental results will be presented. [Work supported by the U.S. Office of Naval Research.]
Observation of ocean surface scattering in the deep ocean using a towed array
Authors: Lynch Stephen D. , D'Spain Gerald L. , Heaney Kevin D. , Baggeroer Arthur B. , Worcester Peter , Mercer James , Murray James
Published: October 2011

Over the course of an experiment in the northern Philippine Sea in 2009, weather and sea surface conditions varied from calm and smooth to stormy and very rough. A ship with an acoustic source deployed at 15 and 60 m held station while a second ship towed Penn State's Five Octave Research Array (FORA) at 120 m depth in an arc, maintaining constant range at the first convergence zone. With the source and receivers so near the ocean surface and with zero closing speed, these events offer an opportunity to extract information about the acoustic waves' interaction with the temporally varying ocean surface. Additionally, the FORA was towed at various depths in a star pattern about the stationary source ship, and a vertical acoustic array was deployed near the source ship. Using meteorological data and a model for ocean waves given weather conditions and fully developed seas, these events offer an opportunity to separate in the data-adaptive beamformer output the arrivals scattered and Doppler shifted by the rough ocean surface while accounting for motions of the receiver and acoustic interactions with the bottom.
Estimating seafloor roughness using synthetic aperture sonar image statistics
Authors: Lyons Anthony P. , Johnson Shawn F.
Published: October 2011

In this work, we present a model to predict the impact of intensity scaling caused by random seafloor roughness on SAS image speckle statistics and the possible use of this model to estimate roughness parameters, such as root-mean-square height and slope. The continuous variation in scattering strength produced by roughness (i.e., roughness-induced changes in seafloor slope) is treated as an intensity scaling on image speckle produced by the SAS imaging process. Changes in image statistics caused by roughness are quantified in terms of an effective K-distribution shape parameter. Comparisons between parameter estimates obtained from the scaling model and estimates obtained from high-resolution SAS data collected in experiments off of the Ligurian coast near La Spezia, Italy, are used to illustrate the efficacy of the model. [Work performed under ONR Grants N00014-10-1-0051, N00014-10-1-0047, and N00014-10-1-0151].
When an idea goes in a different direction from that expected
Authors: Plsek Thomas
Published: October 2011

Quite a few years ago when airlines were using the simple headsets with the rubber tubes, it was realized that they could be coupled to a trombone practice mute to make a system that one could use to practice without disturbing others. As it happened, the idea did not for various reasons work as expected. It was realized that a new instrument could be created by placing the headphones on someone other than the performer. By doing so, it was realized that the acoustic feedback normally received by the performer would be eliminated, the performance space and its acoustic qualities was made irrelevant, and the listener was given a unique perspective shared with no one. Over the past few years, this instrument was used to perform for numerous people. This paper explores and summarizes those adventures.
Why reverberation affects different individuals differently
Authors: Shinn-Cunningham Barbara
Published: October 2011

Any self-respecting architectural acoustician understands that good reflected sound enhances all sorts of important sound attributes. He or she undoubtedly also understands that reflected energy distorts the fine spectrotemporal structure of sound reaching a listener's ears. But what are the perceptual consequences of such minor acoustic distortions of sound detail, and what is the significance of this distortion when designing listening spaces? In psychophysics, recent experiments show that fine spectrotemporal structure is very important for understanding the content of complex, natural sounds, like speech, especially in the presence of background noise or competing sound. This talk will review why spectrotemporal structure is so important for verbal communication in everyday settings. Building from behavioral and physiological measures, this review will explore why even modest amounts of reverberant energy can dramatically impair the ability to communicate for some individuals, even when it causes no such ill effects in others. Understanding such effects is critical when designing listening spaces in which verbal communication is a key activity, like in a classroom.
Verb, reverb, and re-reverb
Authors: Anderson Jim
Published: October 2011

In a contemporary recording, artificial ambience, reverberation of varying length and degree, is added to compliment the various elements in a recording. This mixing condiment comes in many flavors: live chamber, plate, and digital. The application of reverberation is an art, as well as science, and its treatment can be a matter of taste, good, or bad. While it can be difficult to achieve a natural effect with one reverb in a recording, parallel reverbs can be used effectively. As a live performance takes place in a single reverberant hall, its recorded counterpart may take advantage of the application of different multiple reverbs.
A new generation of time variant electro-acoustic enhancement systems
Authors: Barbar Steve
Published: October 2011

In 1991, Dr. David Griesinger presented a paper at the 90th AES convention [preprint 3014] describing a new method for improved electronic acoustic enhancement, and hundreds of these systems have been installed throughout the world. This paper describes a new approach to both hardware and software that comprises a third generation system. The new system retains the essential features of multichannel time variance with low pitch alteration, but updates the algorithms to utilize the superior DSP power of modern computers. Multiple reverberators, equalization, and matrix distribution can be combined into a single, reliable, and easily replaceable piece of hardware. Overall system gain and equalization can be calibrated automatically anytime; parameters in the hall have changed. The new algorithm combines the efficiency of infinite impulse response filters with direct convolution to produce a time-variant structure with extremely low coloration. The algorithm also includes a novel 32 band antifeedback circuit that further reduces coloration when the system is installed in a room. Unlike much of the competition, this system architecture allows the strength of the reverberation to be adjusted independently of the reverberation time, which makes it possible to simultaneously optimize both clarity and reverberance.
Whales and poets—Two tales of techniques for adapting, enhancing, and fictionalizing acoustic traits
Authors: Giegold Carl P. , Watson Kevin T. , Norris Molly K. , Pfeiffer Scott D.
Published: October 2011

Enhancement techniques are employed in two vastly divergent venues in Chicago with the purpose of removing barriers to communication. In the first case, the marine environment scaled to house Beluga whales presents its own acoustical obstacle. In the second, the presence of a microphone can be an obstacle as seen by a poet with a message to share. The Poetry Foundation implemented a voice lift system in a sonorous environment that supports the voice or light amplification, but requires assistance to extend the reach of the unamplified talker. Natural acoustic design, design of traditional public address systems, and the introduction of enhancement techniques are all outlined for these two case studies to illustrate how the roles intersect. Both environments are live in their un-enhanced state. The unusual aspect of these projects is the use of enhancement to increase intelligibility within a naturally reverberant space.
Diffusivity of diffusers in the reverberation room
Authors: Lautenbach Margriet
Published: October 2011

The random incidence absorption coefficient is measured in a reverberation room according to the ISO354 or ASTM C423-09. According to these standards, the diffusivity of a reverberation room is usually obtained with panel diffusers. Besides the fundamental problem that a reverberation room with a highly absorptive specimen is not diffuse, these panel diffusers introduce a number of uncertainties like the acoustical effective volume and the total boundary surface of the reverberation room. This might be one of the causes that some laboratories are structurally able to measure absorption coefficients larger than 1, even if the volume of the specimen, edge absorption, and the absorption of the surface covered by the specimen are taken into account. To reduce the difference in measurement results between different laboratories, the possible use of volume diffusers instead of panel diffusers is investigated. The following criteria are investigated to substantiate the hypothesis that volume diffusers lead to better results: (1) Deviation between microphone-source positions. (2) Comparison to maximum relative standard deviation (ASTM). (3) Comparison to theoretical variance. (4) Influence of place of specimen. The investigations have been performed in a 1:10 scale model. The results are presented in this paper.
On the reproducibility of measuring random incidence sound absorption
Authors: Nash Anthony
Published: October 2011

For over 50 years, the American Society for Testing and Materials (ASTM International) has promulgated a method for the laboratory testing of random-incidence sound absorption coefficients (Test Method C423). This test method falls under the purview of ASTM Committee E33 (Environmental Acoustics). In 1999, the protocols in this test method became significantly more stringent with the goal of improving inter-laboratory “reproducibility” (i.e., quantitative differences among laboratories when testing the same specimen). ASTM calls such an inter-laboratory test a “round robin”; its outcome is an array of computed precision (i.e., uncertainty) values. This paper presents results from several “round robin” evaluations and discusses some possible causes for the range of values. If time permits, the fine points of the test protocols in C423 will be described and compared to those in ISO 354.
Error factors in the measurement of the scattering coefficient in full and small scales
Authors: Sakuma Tetsuya , Lee Hyojin
Published: October 2011

The reverberation room method for measuring the random-incidence scattering coefficient was standardized by ISO 17497-1 in 2004, and now the amendment is being discussed on the specimen mounting and the turntable speed. Regarding the former point, destructive diffraction from an uneven perimeter of a specimen is an error factor to overestimate the scattering coefficient; however, it can be suppressed by setting a border around the turntable. Regarding the latter point, special attention is needed to the combination of the turntable speed and the signal period of MLS in the impulse response measurement. Basically, the turntable speed should be limited by an angular step of 3° to 6° for one signal, thus 60 to 120 signals are required for one revolution. In practice, in order to suppress the time variance, a shorter signal period is preferred as far as the measured reverberation time is guaranteed. However, a best choice of the signal period depends on reverberation rooms in full and small scales, additionally depending on frequency bands. Some data measured in full and small scales demonstrate the effect of the combination on measurement accuracy.
Noise reduction for better detection of beaked whale clicks
Authors: Lu Yang , Klinck Holger , Mellinger David M.
Published: October 2011

We seek to improve the signal-to-noise (SNR) ratio of clicks recorded from Blainville's beaked whales (Mesoplodon densirostris). The proposed filter is based on subspace principles and projects the noisy speech vector onto signal and noise subspaces. An estimate of the clean signal is made by retaining only the components in the signal subspace. To test the filter, a detector using the filter output has been designed for the detection of beaked whale calls. Through simulations, the proposed detector is shown to be capable of detecting most of the desired clicks but is not able to differentiate other co-existing species such as Risso's dolphins and pilot whales' that is, it efficiently detects all clicks. By combining the proposed detector with the energy ratio mapping algorithm (ERMA; Klinck and Mellinger (in press), which measures energy differences between different species, higher detection accuracy for beaked whale clicks can be achieved. The filter can also be used to improve the SNR of other marine mammal acoustic signals.
Spatial orientation of different frequencies within the echolocation beam of a Tursiops truncatus and Pseudorca crassidens
Authors: Ibsen Stuart , Nachtigall Paul , Krause-Nehring Jacqueline , Kloepper Laura , Breese Marlee
Published: October 2011

A 2D array of hydrophones was created to determine the spatial distribution of frequencies within the echolocation beam of a Tursiops truncatus. This Tursiops was shown previously to only pay attention to frequencies between 29 and 42 kHz while echolocating. It was found that the 30 kHz frequency was tightly focused, and the spatial location of the focus was consistently pointed toward the target. At 50 kHz, there was less focusing and less precision in being pointed at the target. At 100 kHz, the focus was often completely lost and was not pointed at the target. This indicates that this dolphin was actively focusing the frequencies it paid attention to toward the target, while the frequencies not paid attention to were left unfocused and undirected. This focusing was probably achieved through morphological manipulations of the melon and nasal air sacs. This explains earlier observations of how the dolphin achieved consistent frequency content only in the 0–42 kHz range with simultaneous variability outside this range in echolocation clicks recorded with a single on-axis hydrophone. Similar results were observed for a Pseudorca crassidens, while performing similar target discrimination tasks. [Office of Naval Research Grant No 0014-08-1-1160 to P.E. Nachtigall supported this work.]
Acoustic behavior of magnetorheological fluids in magnetic fields
Authors: Howarth Thomas R. , Fratantonio Frank , Boisvert Jeffrey E. , Bruno Anthony , Scandrett Clyde L. , Wynn William M. , Davis Philip S.
Published: October 2011

Acoustic metamaterials are being considered for periodic structures where specific microscopic material properties can be tailored to alter macroscopic acoustic fields. One type of acoustic metamaterial being considered is an active fluid known as magnetorheological (MR) fluids. MR fluids contain magnetic particles dispersed within a host fluid where its viscoelastic behavior is controllable by varying the magnetic field intensity. A series of acoustic experiments has recently been conducted at the National High Magnetic Field Laboratory in Tallahassee, Florida. The acoustic sound speed of MR fluids was measured as functions of applied magnetic field strength, normal and orthogonal field orientations, and acoustic frequency. This presentation will discuss MR fluids, measurement methodology, and preliminary results. [Work supported by NAVSEA Division Newport ILIR.]