bluuebunny/crossref_metadata_2025 huggingface dataset:
Modulation difference limen for spectral center-of-gravity signals
Authors: Stewart Amy E. , Hoglund Evelyn M. , Oh Yonghee , Feth Lawrence L.
Published: September 2012

Auditory processing of the dynamic spectral center-of-gravity (COG) of a pair of amplitude modulated (AM) tones was investigated by comparing the modulation difference limen (DL) for a COG signal to that for a sinusoidally frequency modulated (FM) tone. The center-of-gravity effect refers to the listener’s ability to track an amplitude-weighted instantaneous frequency between two tones differing in frequency. To create a dynamic COG, two tones separated in frequency by four ERB were amplitude modulated at the same modulation rate and modulation depth. AM modulators differed only in relative phase. For five normal-hearing listeners, a 2IFC discrimination task was used to determine the DL for frequency deviation across a range of center frequencies, modulation frequencies, and frequency deviations for both FM and COG signals. COG signals were matched to FM signals (same center frequency, modulation frequency, and frequency deviation). Frequency deviation was determined by equating the maximum instantaneous spectral centroid for each signal type. COG DLs were approximately three times larger than the corresponding FM DLs; however, variation with modulation frequency and frequency deviation was similar for the two types of signals. Results indicate comparable auditory processing for the two types of signals.
Novelty detection of covariance among stimulus attributes in auditory perception
Authors: Stilp Christian , Kluender Keith
Published: September 2012

Novelty detection is characterized by enhanced response to a stimulus with some property changed relative to expected input. Many reports examine sensitivity to deviations in physical acoustic dimensions, patterns, or simple rules, but fail to consider information in higher-order statistical relationships between dimensions. Here we report novelty detection that depends upon encoding of experienced covariance between complex acoustic dimensions (attack/decay, spectral shape.) Here, novelty is defined as violation of experienced covariance between otherwise independent acoustic attributes. Listeners primarily discriminated sound pairs in which attributes supported robust covariance (15 pairs, Consistent condition) and rarely discriminated sounds that violated this redundancy (1 pair, Orthogonal condition) in randomized AXB trials without feedback. Probability of occurrence for Orthogonal trials was minimized by withholding them until the final testing block. Discrimination accuracy for Orthogonal sounds exceeded that for Consistent sounds as well as that for control stimuli absent experienced redundancy between attributes. Increasing Orthogonal trial probability reduces this enhancement, as does acoustic similarity between Consistent and withheld Orthogonal sound pairs. Results parallel novelty detection as measured by stimulus-specific adaptation and mismatch negativity. Implications for high-level auditory perception and organization will be discussed. [Supported by NIDCD.]
The effect of visual information on speech perception in noise by electroacoustic hearing
Authors: Tahmina Qudsia , Bhandary Moulesh , Azimi Behnam , Hu Yi , Utianski Rene L. , Liss Julie
Published: September 2012

The addition of amplified low frequency hearing to cochlear implants has been shown to provide substantial performance benefits for cochlear implant (CI) users, particularly in noise. In the current study, we examined the extent to which the presence of visual information (facial movement during speech) augments perception for CI listeners with electroacoustic stimulation (EAS). Two experiments were conducted. In the first one, participants transcribed semantically anomalous phrases in quiet and noise. Intelligibility results showed modest improvements in intelligibility for low and high levels of noise, and dramatic gains (30+ percentage points) in midlevel noise. Error analyses conducted on the transcripts further suggest that the perceptual benefits extended beyond articulatory place information to that of facilitating lexical segmentation. In the second experiment, participants were tested on their recognition of words in sentences corrupted by noise. Results showed significant benefit of hearing aids in EAS patients. However, the benefit of acoustic hearing was not apparent when visual information was available. Our results will provide guidance for auditory rehabilitation strategies in this population.
The role of phonological alternation in speech production: Evidence from Mandarin tone Sandhi
Authors: Politzer-Ahles Stephen , Zhang Jie
Published: September 2012

An open question in psycholinguistics is the nature of the phonological representations used during speech production and the processes that are applied to them, particularly between lexical access and articulatory implementation. While phonological theory posits that speakers' grammar includes mechanisms for transforming from input to output forms, whether such mechanisms also are used by the parser during online speech production is unclear. We examined the role of phonological alternations in Mandarin Chinese real and novel compounds using the implicit priming paradigm, which can reveal forms being used prior to articulation. We compared modulations of the implicit priming effect in sets of words that are heterogeneous at the lexical level (where one word has a different lexical tone than the rest) to those in sets that are heterogeneous at the derived level (where a word has the same underlying lexical tone, but that tone surfaces as a different tone because of tone sandhi). Both lexical and derived heterogeneous sets reduced the priming effect, suggesting that phonological alternation was computed abstractly before articulation was initiated. We argue that the progression from underlying phonological representations to articulatory execution may be mediated online by a level at which abstract phonological alternations are processed.
From speech signal to phonological features—A long way (60 years and counting)
Authors: Reetz Henning
Published: September 2012

When Jakobson, Fant and Halle proposed 1952 their feature system to describe the representation of speech, they wrote: “In decoding a message received (A), the listener operates with the perceptual data (B) which are obtained from the ear responses (C) […] The systematic exploration of the first two of these levels belongs to the future and is an urgent duty.” In the last three decades, this approach has been substituted by stochastic modeling to map the speech signal to lexical (word) entries in automatic speech recognition. Although this has lead to working ASR applications, the process of speech understanding by humans is still of ‘urgent duty’. The FUL (featural underspecified lexicon) system is one model for this process and this talk will present its methods for mapping the signal onto phonological features, which removes acoustic detail that we assume is irrelevant for (human) speech understanding. The analysis is performed with a high temporal resolution to model the ‘online’ processing of the human brain and provide redundancy for noisy signals. The ultimate goal is to match the acoustic signal to feature sets that activate possible and suppress improbable word candidates. These features sets themselves are defined by the phonological structure of a language rather than by extensive training with speech material. The presentation includes an online demonstration of the system.
The exemplar-based lexicon
Authors: Johnson Keith
Published: September 2012

Exemplar-based models of memory have been successful in accounting for a variety of recall and recognition data in general cognitive psychology, and provide an interesting counter-point to other more “standard” models of the mental lexicon. This talk will discuss the ways that the exemplar-based lexicon deals with spoken language variability in auditory word recognition: with emphasis on talker normalization, cross-dialect speech perception, and the recognition of highly variable conversational speech. I will also discuss the use of exemplar-based models in the linguistic theory of sound change, and the relationship between exemplar-based models and neurophonetics. Although the specific modeling strategy employed in exemplar-based modeling is likely over-simplified and wrong in some ways, the success of this type of model indicates that something true is being captured. I will suggest that what makes exemplar-based models useful is that they provide a way for the theorist to include a role for fine phonetic detail in the representation of phonological representations. The ultimate argument is that phonetic memory is gradient as well as categorical, and should be modeled as such.
The consequences of lexical sensitivity to fine grained detail: Solving the problems of integrating cues, and processing speech in time
Authors: McMurray Bob , Toscano Joseph C.
Published: September 2012

Work on language comprehension is classically divided into two fields. Speech perception asks how listeners cope with variability from factors like talker and coarticulation to compute some phoneme-like unit; and word recognition assumed these units to ask how listeners cope with time and match the input to the lexicon. Evidence that within-category detail affects lexical activation (Andruski, et al., 1994; McMurray, et al., 2002) challenges this view: variability in the input is not “handled” by lower-level processes and instead survives until late in processing. However, the consequences of this have not been fleshed out. This talk begins to explore them using evidence from the eye-tracking paradigms. First, I show how lexical activation/competition processes can help cope with perceptual problems, by integrating acoustic cues that are strung out over time. Next, I examine a fundamental issue in word recognition, temporal order (e.g., distinguishing cat and tack). I present evidence that listeners represent words with little inherent order information, and raise the possibility that fine-grained acoustic detail may serve as a proxy for this. Together these findings suggest that real-time lexical processes may help cope with perceptual ambiguity, and that fine-grained perceptual detail may help listeners cope with the problem of time.
The structure of the lexical network influences lexical processing
Authors: Vitevitch Michael S. , Goldstein Rutherford
Published: September 2012

Network science is an emerging field that uses computational tools from physics, mathematics, computer science, and other fields to examine the structure of complex systems, and explore how that structure might influence processing. In this approach, words in the mental lexicon can be represented as nodes in a network with links connecting words that are phonologically related to each other. Analyses using the mathematical tools of network science suggest that phonological networks from a variety of languages exhibit the characteristics of small-world networks, and share several other structural features. Studies of small-world networks in other domains have demonstrated that such networks are robust to damage, and can be searched very efficiently. Using conventional psycholinguistic tasks, we examined how certain structural characteristics influence the process of spoken word recognition. The findings from these experiments suggest that the lexicon is structured in a non-arbitrary manner, and that this structure influences lexical processing.
Lexically guided category retuning affects low-level acoustic processing
Authors: Reinisch Eva , Holt Lori L.
Published: September 2012

Listeners adapt to non-canonically produced speech by using lexical knowledge to retune phoneme categories. It is unclear, however, whether these retuned categories affect perception at the category level or the signal-to-representation mapping. This was addressed by exploring conditions of cross-speaker generalization of retuned fricatives. During a lexical-decision task, American listeners heard a female Dutch learner of English whose word-final /f/ or /s/ was replaced by an ambiguous sound. At test listeners categorized minimal pairs ending in sounds along [f]-[s] continua spoken by the same female speaker and a new male speaker. Listeners’ [f]-[s] categorization for the previously heard speaker shifted as a function of exposure. Generalization to the new speaker was not found when continua between his natural [f]-[s] endpoints were presented. However, listeners did generalize to this voice when presented with only a subset of the male’s most [f]-like continuum steps, adjusting the fricative range to match the exposure speaker’s, and eliminating a bias toward /s/-responses in the male continua. Listeners thus use short-term acquired knowledge about acoustic properties of phonemes even to interpret upcoming phonemes from previously unheard speakers. Acoustic match, not speaker identity, predicted the results supporting accounts of the effect originating in the early signal-to-representation mapping.
Lexical effects on the perception of /l/ allophones in English
Authors: Whalen D. H. , Beller-Marino Ylana , Kakadelis Stephanie , Dawson Katherine M. , Best Catherine T. , Irwin Julia R.
Published: September 2012

Previous work has shown that perception of allophones of /p/ in English utterances was influenced by lexical status. In nonwords, the aspirated allophone was preferred whether appropriate or not; in words, the appropriate allophone was preferred [Whalen, Best, & Irwin (1997), J. Phonetics, 25, 501-528]. Here, we examined dark and light [l] in English words and nonwords. Dark [l] occurs in syllable codas whereas light [l] occurs in onsets. Items were selected in pairs to balance syllable position in monosyllabic English words and pseudowords, such as “gel”/“ledge”, “teal”/“leat”, and “beel”/“leeb.” Frequency of occurrence for words was also manipulated to explore compatibility with versions of exemplar theory. A phonetician produced two versions of each item, one with a contextually appropriate allophone and one with the inappropriate. Listeners were asked to rate where each acoustically presented item fell on a Likert scale (1-7) between “ideal (native) pronunciation” or “bad (nonnative) pronunciation.” Results will be discussed in terms of the underlying representation needed to account for lexical effects in perception. The relationship to phonotactic rules will also be discussed.
Autonomous underwater vehicle localization using the acoustic tracking system
Authors: Pelavas Nicos , Heard Garry J. , Lucas Carmen E.
Published: September 2012

Operator peace-of-mind during Autonomous Underwater Vehicle (AUV) missions is dependent on the ability to localize the vehicle. During launch and recovery phases this capability is particularly important. Defence R&D Canada (DRDC) Atlantic has designed and built a long-range tracking system for the International Submarine Engineering Explorer class AUVs. The acoustic tracking system (ATS) enables an operator on a loud icebreaker platform to determine the position of the AUVs at ranges up to 30 km. An acoustic projector, mounted on the AUV, emits a hyperbolic frequency modulated (HFM) chirp at a preset time interval. A small, directional, acoustic receiving array mounted near the stern of the icebreaker, accurately synchronized with the remote projector, receives signals from the distant AUV. Matched filter processing is used to determine the time of flight of the transmitted chirp. A beamforming algorithm applied to the data provides bearing and elevation angle estimates for the received signals. A ray tracing algorithm then uses this information, along with the sound velocity profile, to determine the position of the AUV. Moreover, ATS uses different HFM chirps to provide a basic one-way AUV state messaging capability. We conclude with a brief discussion of ATS data collected during in-water trials.
Passive localization of surface vessels in shallow water using broadband, unintentionally radiated noise
Authors: Sell Alexander W. , Culver R. Lee
Published: September 2012

The waveguide invariant relates ocean waveguide propagation conditions to the spectral interference patterns (or striations) in range-frequency plots. The striations are the result of interaction between propagating modes. A method of source localization, using a horizontal line array (HLA), that exploits this relationship will be presented. Source azimuth is estimated using conventional Bartlett beamforming, after which source range is estimated from spectral interference observed along the HLA as well as knowledge of the waveguide invariant. Automation of this process makes use of a spectral characterization method for striation slope estimation, which works well in some but not all cases. The use of a physics-based, range-dependent waveguide invariant model to improve the range estimates will also be discussed. This method has been applied to acoustical data recorded in 2007 at the Acoustical Observatory off the coast of Port of the Everglades, Florida. Localization results compare favorably with radar-based Automatic Identification System (AIS) records. [Work supported by ONR Undersea Signal Processing.]
Bayesian localization of acoustic sources with information-theoretic analysis of localization performance
Authors: Hayward Thomas J.
Published: September 2012

Approaches investigated to date for localizing acoustic sources include conventional beamforming, matched field processing, and Bayesian methods [e.g., Pitre and Davis, J. Acoust. Soc. Am., 97, 1995], with recent research revisiting Bayesian methods with focalization and marginalization approaches [Dosso and Wilmut, J. Acoust. Soc. Am., 129, 2011]. Information-theoretic bounds on source localization performance were investigated by Meng and Buck [IEEE Trans. Sig. Proc., 58, 2010] extending earlier work of Buck. The present work investigates direct application of Bayes’ Rule to source localization and information-theoretic quantification and analysis of localization performance, taking as an example the localization of a time-harmonic source in a range-independent shallow-water acoustic waveguide. Signal propagation is represented by normal modes, and additive Gaussian ambient noise is represented by a Kuperman-Ingenito model. The localization performance is quantified by the entropy of the Bayesian posterior pdf of the source location, and an information-theoretic interpretation of this performance measure is presented. Comparisons with matched-field localization performance and extensions of the modeling and localization performance analysis to inhomogeneous media are discussed. [Work supported by ONR.]
Doppler-based motion compensation algorithm for focusing the signature of a rotorcraft
Authors: Goldman Geoffrey H.
Published: September 2012

A computationally efficient algorithm was developed and tested to compensate for the effects of motion on the acoustic signature of a rotorcraft. For target signatures with large spectral peaks that vary slowly in amplitude and have near constant frequency, the time-varying Doppler shift can be tracked and then removed from the data. The algorithm can be used to preprocess data for classification, tracking, and nulling algorithms. The algorithm was tested on rotorcraft data. The average instantaneous frequency of the first harmonic of a rotorcraft was tracked with a fixed-lag smoother. Then, state space estimates of the frequency were used to calculate a time warping that removed the effect of the Doppler shift from the data. The algorithm was evaluated by analyzing the increase in the amplitude of the harmonics in the spectrum of a rotorcraft. The results depended upon the frequency of the harmonics, processing interval duration, target dynamics, and atmospheric conditions. Under good conditions, the results for the fundamental frequency of the target (~11 Hz) almost achieved the predicted upper bound. The results for higher frequency harmonics had larger increases in the amplitude of the peaks, but significantly fewer than the predicted upper bounds.
The measured 3-D primary acoustic field of a seismic airgun array
Authors: Tashmukhambetov Arslan M. , Ioup George E. , Ioup Juliette W. , Sidorovskaia Natalia A. , Newcomb Joal J. , Stephens James M. , Rayborn Grayson H. , Summerfield Phil
Published: September 2012

The Littoral Acoustic Demonstration Center has conducted an experiment to measure the 3-D acoustic field of a seismic airgun array in the Gulf of Mexico. A seismic source vessel shot specified lines to give solid angle and range information. Hydrophone positions were measured by an ultra-short baseline (USBL) acoustic system while the source ship was turning between lines. An acoustic Doppler current profiler measured currents so the positions could be modeled between USBL measurements. The position locations were refined by using information from the acoustic arrival times on the hydrophones. Peak pressures, sound exposure levels, total shot energy spectra, one-third octave band analyses, and source directivity studies are used to characterize the field. One third octave band analysis shows received levels up to 180 dB re 1 µP for emission angles from 0 degrees (vertically down) up to 45 degrees for horizontal ranges up to 200 m at endfire, between 10 Hz and 200 Hz. The levels decrease with increasing frequency above 200 Hz, with increasing horizontal ranges, and for emission angles above 45 degrees. The levels are lower at broadside than at endfire. [Research supported by the Joint Industry Programme through the International Association of Oil and Gas Producers.]
Investigation of a tunable combustive sound source
Authors: McNeese Andrew R. , Muir Thomas G. , Wilson Preston S.
Published: September 2012

The Combustive Sound Source (CSS) is a versatile underwater sound source used in underwater acoustics experiments. The source is comprised of a submersible combustion chamber which is filled with a combustive gas mixture that is ignited via spark. Upon ignition, the combustive mixture is converted into high temperature combustion byproducts which expand and ultimately collapse back to smaller volume than before ignition. Acoustic pulses are radiated by the bubble activity. The CSS can be used as a source for calibration, TL measurements, and bottom characterizations, and when deployed on the bottom can create seismic interface waves. Current environmental regulations and varying experimental needs require a tunable source that allows users to easily alter the source level, bandwidth, and signal duration. Current efforts have focused on altering the bubble growth and collapse in attempt to tune the radiated signals to meet various needs. Scale models have been constructed and tested in in-house tank experiments. Discussion will focus on the results of the study along with future plans for development and modeling.
Mitigation of underwater radiated noise from a vibrating work barge using a stand-off curtain of large tethered encapsulated bubbles
Authors: Lee Kevin M. , Wochner Mark S. , Wilson Preston S.
Published: September 2012

A stand-off curtain of encapsulated bubbles with resonance frequencies of approximately 50 Hz was used to attenuate radiated noise from a work barge vibrated by onboard rotating machinery in a lake experiment. The purpose of this experiment was to provide a scale-model of how a noise reduction system of tethered encapsulated bubbles would be deployed to mitigate noise from a shallow water drilling ship. The work reported here is an extension of previous tests which used an array of encapsulated bubbles attached directly to the bottom of the work barge to reduce the radiated sound levels [J. Acoust. Soc. Am. 131, 3506 (2012)]. The design of the new stand-off encapsulated bubble curtain is described, including the finite-element model that was developed to aide in the design. The deployment and acoustic testing of the curtain are also described. Results from the tests demonstrate that the system is both practical to deploy and is effective in reducing the underwater noise radiated into the lake from the work barge. [Work supported by Shell Global Solutions.]
Low-frequency ambient noise characteristics and budget in the South China Sea basin
Authors: Chiu Ching-Sang , Miller Christopher W. , Joseph John E.
Published: September 2012

A sound record measured by a moored hydrophone in the South China Sea basin was analyzed. Sampled at a rate of 1.6 kHz and with a duty cycle of approximately 1-min-on and 14-min-off, the measured time series captures the spectral characteristics and variability of the ambient noise in the less-than-800-Hz band over an annual cycle. Using a combination of automated and manual screening methods, the dominant regular and transient noise sources were identified and categorized, which include shipping, wind waves, seismic air-gun surveys, shots/explosives and sonar. Intermittent self noise (squeaking sounds) that prevailed at times during the passage of the very large-amplitude internal waves was also identified. In addition to the noise budget, the variability in the daily and monthly means and variances of the measured noise spectrum and band levels were examined. In order to gain insights into the predictability of the ambient noise field in this marginal sea, the interpretation of the data was facilitated with temperature records measured with moored instruments, wind and precipitation time series from the US Naval Operational Global Atmospheric Prediction System (NOGAPS), and vessel motion simulation based on historical shipping density and lane structure. [Research sponsored by the Office of Naval Research.]
Hydrophone calibration using ambient noise
Authors: Castillo Moore Kristy , Crocker Steven E.
Published: September 2012

Hydrophone calibration typically requires a good signal-to-noise (SNR) ratio in order to calculate the free-field voltage sensitivity (FFVS). However, the SNR requirements can limit the calibration of hydrophones with low sensitivity, particularly in the low frequency range. Calibration methods using ambient noise in lieu of a generated signal will be explored at the Underwater Sound Reference Division (USRD) Leesburg Facility in Okahumpka, FL. The USRD Leesburg Facility is at a natural spring in rural central Florida and is one of the Navy’s quietest open water facilities with no boating noise, limited biological noise, an isolated location, low reverberation and an isothermal water temperature profile below 5 meters. Comparison calibrations will be made with two similar hydrophones using the ambient noise in the natural spring and the results will be compared to calibrations made with the same hydrophones using a generated signal.
Transducer models for simulating detection processes for underwater mining
Authors: Been Kyounghun , Ahn Hongmin , Lee Hunki , Noh Eunghwy , Ohm Won-Suk , Moon Wonkyu
Published: September 2012

Numerical simulations on propagating and scattering processes of sound waves in water and sediment may be useful for designing a detection system for underwater mining. Here a transducer model is developed for the numerical simulation to implement radiating and receiving processes of transducers into numerical calculations. Since the Rayleigh integral approach is adopted for acoustic radiation, the accurate velocity profiles over the radiating surfaces of a transducer array should be estimated considering the mechano-acoustic interactions including the dynamics of unit drivers and the acoustic radiation loadings on the radiation surfaces. We adopted the approach that the surface velocity is calculated using the transducer model with the acoustic loading while the loading effects are estimated via calculating the radiation impedance of transducer array using Rayleigh integrals. The estimated velocity profile of the transducer surface is used for calculating the accurate sound fields generated by the transducer array. A similar approach will be adopted for estimating receiving characteristics. [The Authors gratefully acknowledge the support from UTRC(Unmanned technology Research Center) at KAIST(Korea Advanced Institute of Science and Technology), originally funded by DAPA, ADD in the Republic of Korea.]
Using musical instruments for narrow band impulse excitation of halls to aid in acoustical analysis
Authors: Woolworth David S.
Published: September 2012

This paper suggests that narrow band specific information of a room's acoustic behavior can be revealed through the use of musical instruments as impulse sources that would be otherwise buried in response to a broadband impulse excitation or other sequence. An advantage to this is discovering acoustic anomalies before data analysis, as well as subjective judgments to room response and stage acoustics to add to standardized and more advanced technical methods. A violin, snare drum, and double bass are examined in terms of directionality and frequency content with and an example hall is analyzed.
Detecting the angle of arrival of discrete echoes by measuring polar energy time curves in a contemporary church
Authors: Pyper Ted , Rayburn Ray
Published: September 2012

In order to deal with speech intelligibility concerns from the main sound system at a contemporary church, the authors executed measurements in the main assembly hall to detect late arriving reflections at various positions in the audience and on the stage. By implementing Polar Energy Time Curves (PETC) at each measurement location, discrete reflections were identified by time arrival and also, more critically, by angle of arrival. The advantage of calculating the PETCs on site during the measurement session was that the authors could physically pinpoint the sources of discrete echoes by using a laser positioned at the center of the microphone armature used to take the measurements. This gave the authors immediate feedback to diagnose reflections and help select additional measurement positions within the room. With this information, the authors were able to identify room surfaces that contributed significantly to the late arriving echoes and specify appropriate sound absorptive treatments for these surfaces.
A model for passive underwater noise suppression by bubble curtains surrounding point or line sources in shallow water
Authors: Hay Todd A. , Ilinskii Yurii A. , Zabolotskaya Evgenia A. , Hamilton Mark F.
Published: September 2012

Underwater noise generated by pile driving, rotating machinery, or towers supporting offshore wind turbines may disturb marine life and inhibit detection of coastal activities via passive sonar and seismic sensors. Noise abatement techniques have therefore been proposed to limit the propagation of such noise into the far field, and many of these employ a curtain of freely-rising bubbles or tethered encapsulated bubbles to surround the towers [Lee et al., J. Acoust. Soc. Am. 131, 3507(A) (2012)]. An analytic model, based on a Green's function approach, is presented for the passive noise suppression provided by a discrete number of bubbles surrounding submerged point sources or pulsating cylindrical towers above horizontally-stratified layers of sediment. The sediment layers are modeled as viscoelastic media and the Green's function is derived via angular spectrum decomposition [Hay et al., J. Acoust. Soc. Am. 129, 2477(A), (2011)]. Simulations in which the bubbles are assumed to react independently to the incident field will be compared to those in which bubble-bubble interaction is taken into account. The effects of bubble size distributions and void fractions on noise suppression will be investigated for different source configurations. [This work was supported by the Department of Energy under Grant DE-EE0005380.]
Reduction of underwater sound from continuous and impulsive noise sources using tethered encapsulated bubbles
Authors: Lee Kevin M. , McNeese Andrew R. , Wochner Mark S. , Wilson Preston S.
Published: September 2012

Arrays of encapsulated bubbles have been shown to be very effective in reducing underwater sound radiated from various sources [J. Acoust. Soc. Am. 131, 3356 (2012); J. Acoust. Soc. Am. 131, 3506 (2012) ]. These arrays have been used to treat both sources of noise and to protect a receiving area from external noise. The system provides noise reduction using the combined effects of bubble resonance attenuation and acoustic impedance mismatching. Results are reviewed from experiments where tethered encapsulated bubble arrays were used to reduce underwater sound levels from both continuous and impulsive sound sources. In one set of experiments, the encapsulated bubble array attenuated continuous wave sound from a compact electromechanical source. In the other set of experiments, the continuous source was replaced by a combustive sound source [IEEE J. Oceanic Eng. 20, 311--320 (1995)], which was intended to simulate real-world impulsive noise sources such as impact pile driving or airguns used in seismic surveys. For both the continuous and impulsive sources, the encapsulated bubbles provided as much as 45 dB of reduction in the 10 Hz to 600 Hz frequency band. [Work supported by Shell Global Solutions and ARL IR&D program.]
Peeling the onion: What alarm calls can reveal about mammalian populations
Authors: Hooper Stacie , McCowan Brenda , Morelli Toni Lyn , Kastely Christina
Published: September 2012

While individually distinctive vocalizations have been used as a tool for the conservation and management of bird populations, few studies have investigated the potential of a bioacoustic tool for use with terrestrial mammals. Even relatively simple signals, such as alarm calls, have been shown to contain different types of information, and can even be individually distinctive in their structure. Similarities in vocal structure among individuals may also reflect close kin relationships, as suggested by previous work. We explored the feasibility of a bioacoustic tool for monitoring mammalian populations by testing for the presence of individual, age-class, and sex-related information within the alarm calls of Belding’s ground squirrels from several geographically distinct populations. A neural network was used to successfully classify alarm calls to individual, age class and sex, demonstrating that this species’ alarm calls contain information regarding at least three different caller characteristics. We also found that acoustic similarity, as measured by an index of acoustic distance, was significantly correlated with genetic relatedness between individuals. This work indicates that vocalizations have the potential to provide more information to wildlife managers about terrestrial mammal populations than just species presence, and may even provide insight about the level of inbreeding.
Response of nesting northern Goshawks to logging truck noise Kaibab National Forest, Arizona
Authors: Grubb Teryl , Pater Larry , Gatto Angela , Delaney David
Published: September 2012

We recorded 94 sound/response events at northern goshawk (Accipiter gentilis) nests 167, 143, and 78 m from the nearest road in Jun 2010: 60 experimentally controlled logging trucks, plus 30 passing light aircraft, 3 cars, and 1 all-terrain vehicle (ATV). Logging truck noise levels varied among nest sites and with distance from roads (F = 36.753, P < 0.001, df = 59). Aircraft noise levels for each day of testing ranged between 45.6-67.9 dB, and varied little among test sites, 60.1-65.6 dB (F = 2.008, P = 0.154, df = 29). Our test logging truck (61.9 dB adjusted CLEQ) was no louder than passing aircraft (62.3 dB adjusted CLEQ; t-test, P = 0.191), which goshawks generally ignored. The logging truck resulted in 27% no response and 73% alert response; passing aircraft resulted in 90% no response and only 10% alert response; and 3 cars and 1 ATV, combined, resulted in 50% each for no response and alert response (χ2 = 82.365, P < 0.005). Goshawk alert response rates were inversely proportional to nest distance from the nearest road (χ2 = 29.861, P < 0.005). Logging truck noise had no detrimental effects on nesting northern goshawks on the Kaibab Plateau, Arizona.
Determinants of accuracy in a terrestrial microphone array
Authors: Krakauer Alan H. , Burt John , Willits Neil , Patricelli Gail L.
Published: September 2012

Acoustic sensor arrays can allow researchers to localize the position of vocalizing animals. During the course of research on a threatened bird species, the greater sage-grouse, we developed a 24-channel wired array to non-invasively monitor male courtship displays at traditional display grounds (i.e. leks). Here we describe a study in which we localized repeated playbacks of four local species while varying speaker position, the number and arrangement of microphones, and accuracy of speed of sound and sensor location estimates. As expected, localization accuracy was lowest when the speaker was outside the array and when using a linear microphone arrangements. We found no overall effect of species identity in spite of strong differences in time and frequency structure of the playbacks, although we did find significant interactions of species with other factors in our analysis. Simulated errors in speed-of-sound-in-air and estimation of sensor position revealed that while localization was most accurate when these errors were small, localization was still possible even with relatively large errors in these two factors. While we hope these results will help researchers to design effective sensor arrays, specific outcomes will depend on study-specific factors as well as the specific sound processing and localization algorithms employed.
Passive acoustic monitoring of fish in shallow water estuaries
Authors: Sprague Mark W. , Krahforst Cecilia S. , Luczkovich Joseph J.
Published: September 2012

Passive acoustic monitoring is a useful tool for studying soniferous fishes in shallow water estuaries. We have used a variety of techniques for monitoring the acoustic environment in the coastal waters of North Carolina (USA) to study fishes in the Family Sciaenidae (drums and croakers), which produce sounds with frequencies below 1000 Hz. We will present data recorded with hydrophones deployed from a small boat, a hydrophone array towed behind a boat, and remote data loggers. We have used passive acoustic recordings to study the distributions (large- and small-scale) and seasonality of acoustically active courtship and spawning behavior, acoustic interactions between predators and prey, the effects of noise from tugs and small boats on fish sound production, and relationships between fish sound production and environmental parameters such as temperature and salinity. One limitation on shallow-water acoustic monitoring is the sound propagation cutoff frequency, which depends on the water depth. All frequency components below the cutoff frequency decay exponentially with propagation distance. This limit on shallow-water sound propagation must be considered when selecting locations for acoustic monitoring and comparing recordings made in waters of different depths. We will explore the implications on acoustic monitoring due to the cutoff frequency.
Reproductive success of Mexican spotted owls (Strix occidentalis lucida) in relation to common environmental noise ― biotic, non-military aircraft, and weather-related
Authors: Bowles Ann E. , Denes Samuel L. , Hobbs Chris , Plotkin Kenneth J.
Published: September 2012

From 2000 to 2005, noise in Mexican spotted owl habitat in the Gila National Forest, NM, was monitored using an array of Larson-Davis (LD) sound level meters (SLMs). Thirty-nine SLMs were deployed across a 20 km x 24 km area, collecting 2-s time interval data mid-April to July, resulting in over 350,000 hr of data. Time-history profiles could be used to attribute many events to sources reliably when SNR exceeded the background by 5-10 dB. The events were categorized as biotic (insects and chorusing birds), thunder, regional commercial jet aircraft, and local air traffic (recreational and firefighting). Measured by the proportion of 2-s samples with LAeq > 60 dB, biotic sources and thunder were the most important. Regional commercial jet traffic was the most significant anthropogenic source, accounting for 2% of the total. Based on cumulative sound exposure, thunder was the greatest contributor. Regression techniques were used to relate owl reproductive success to noise metrics by source. Biotic noise was the only significant correlate, highly and positively related to owl reproductive success. The most reasonable interpretation was a strong relationship between biotic noise and owl prey base [Work supported by U.S. Air Force ACC/CEVP.]
Assessing the effects of sound on a forest-nesting seabird, the threatened marbled murrelet (Brachyramphus marmoratus)
Authors: Teachout Emily J.
Published: September 2012

The marbled murrelet is a forest-nesting seabird that is federally listed under the Endangered Species Act. This species is unusual in that it flies up to 70 miles inland to nest in mature trees rather than on shorelines near its foraging habitat. The first nest was not discovered until 1974, and much remains to be learned about this difficult-to-study species, including its basic hearing sensitivities and response to auditory stimuli. In evaluating the effects of federal actions on this species, we must assess the potential effects of anthropogenic sound from a variety of sources, both at-sea and in the forested environment. Over the past ten years, we have developed an approach for analyzing the effect of anthropogenic sound by conducting literature reviews, convening expert panels, and drawing from information on other species. We address both impulsive and continuous sounds from sources including impact pile driving, blasting, heavy equipment noise, and sonar. Interim thresholds for expecting injurious effects from some of these sources are in use, and refinements to our analysis of forest-management activities were recently applied to landscape-scale consultations. The bioacoustic research needs of this unique species continue to emerge as we apply these approaches in both the aquatic and terrestrial environments where murrelets occur.
The American National Standards Institute/Acoustical Society of America new (draft as 5 May 2012) standard method to define and measure the background sound in quiet areas
Authors: Schomer Paul , Fristrup Kurt
Published: September 2012

This draft standard is a joint work effort of S3/SC1, the animal bioacoustics committee, and S12, the noise committee. The draft standard includes 3 major, distinct components: (1) a method to measure the background using unattended instruments, and based on L-levels with L-90 as the default; (2) a definition for ANS-weighted sound pressure level, which is simply the A-weighted sound level after deleting all of the sound energy in the 2-kHz octave band or above; and (3), requirements for monitoring the sound in parks and wilderness area. The background measurement procedure is mainly for low-noise residential areas and relevant to the siting of such installations as wind farms and power plants. The ANS-weighting is applicable to both measurement of background and monitoring in parks. The requirements for monitoring in parks and wilderness areas ensure that measurements adequately capture the range of natural ambient conditions. The draft standard provides for two grades of measurement/monitoring: engineering or survey. In addition, this is the first standard to clearly and unambiguously define and establish the requirements for the measurement of percentile levels (exceedance values).
Effect of skull anatomy on intracranial acoustic fields for ultrasound-enhanced thrombolysis
Authors: Korfhagen Joseph J. , Raymond Jason L. , Holland Christy K. , Shaw George J.
Published: September 2012

Transcranial ultrasound improves thrombolytic drug efficacy in ischemic stroke therapy. The goal of this study was to determine the ideal ultrasound parameters for obtaining peak rarefactional pressures exceeding the stable cavitation threshold at the left anterior clinoid process (lACP) of the skull. This location is near the origin of the middle cerebral artery, a common site for ischemic stroke. For 0.5, 1.1 and 2.0-MHz ultrasound transducers, pulse repetition frequencies (PRF) ranging from 5.4-8.0 kHz were studied at a 50% duty cycle. Attenuation and ultrasound beam distortion were measured from a cadaveric human skull. Each transducer was placed near the left temporal bone such that the unaberrated maximum acoustic pressure would be located at the lACP. A hydrophone measured the acoustic field around the lACP. Free-field measurements were taken in the same locations to determine attenuation and beam focus distortion. For 5 skulls, the average pressure attenuation at the lACP was 68±19, 91±5.1, and 94±4.7% for 0.5, 1.1, and 2.0 MHz, respectively. The degree of displacement of the beam focus depended on the skull properties, but not the center frequency nor PRF. In conclusion, lower frequencies exhibited lower attenuation and improved penetration at the lACP. This work was supported by NIH-3P50-NS044283-06S1.
Analytical and numerical approximations for the lossy on-axis impulse response of a circular piston
Authors: McGough Robert
Published: September 2012

In biological tissues, the frequency dependence of attenuation and speed of sound for ultrasound propagation is described by the power law wave equation, which is a partial differential equation with fractional time derivatives. As demonstrated previously, the time domain Green's function for the power law wave equation combined with the Rayleigh-Sommerfeld integral is an effective reference for calculations of the lossy on-axis impulse response of a circular piston. Using the result obtained from this reference, two different approximations to the lossy on-axis impulse response are evaluated. The first approximation is an analytical expression that is proportional to the difference between two cumulative distribution functions for maximally skewed stable probability densities. The second approximation numerically convolves the lossless impulse response with a maximally skewed stable probability density function. The results show that both approximations achieve relatively small errors. Furthermore, the analytical approximation provides an excellent estimate for the arrival time of the lossy impulse response, whereas the departure time of the lossy impulse response is more difficult to characterize due to the heavy tail of the maximally skewed stable probability density function. Both approximations are rapidly calculated with the STABLE toolbox. [supported in part by NIH Grant R01 EB012079.]
The lossy farfield pressure impulse response for a rectangular piston
Authors: McGough Robert
Published: September 2012

The impulse response of the velocity potential is useful for computing transient pressures in lossless media, especially for calculations in the nearfield region. Closed form expressions for the lossless impulse response of the velocity potential in the nearfield are available for circular and rectangular transducers and for several other geometries. A closed form lossless farfield expression is also available for rectangular transducers. Typically, when the effects of attenuation are introduced, the numerical calculation is performed in the frequency domain, and the time response is obtained with an inverse fast Fourier transform. To derive an equivalent analytical result directly in the time domain, all path lengths that appear in the denominator scaling term of the lossy diffraction integral are treated as constants, and a binomial expansion is applied to the path length that appears in the time delay term. The resulting analytical expression, which describes the lossy farfield pressure impulse response, is directly expressed in terms of maximally skewed stable probability density functions and cumulative distribution functions. Results are compared with the Rayleigh Sommerfeld integral, and excellent agreement is achieved in the farfield region. [supported in part by NIH Grant R01 EB012079.]