bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustics at the ALOHA Cabled Observatory: On-going results and new instruments
Authors: Howe Bruce , Roth Ethan H.
Published: November 2013

Since June 2011, the ALOHA Cabled Observatory (ACO) has been collecting ocean acoustic data, continuing an earlier data set covering February 2007—October 2008. The ACO is at Station ALOHA 100 km north of Oahu, the field site of the Hawaii Ocean Time-series (HOT) program that has collected biological, physical, and chemical oceanographic data since 1988. At 4728 m water depth, it is the world’s deepest operating cabled observatory. On-going acoustics results will be presented along with results from two new instruments to be deployed: a WHOI micro-modem, and a camera/hydrophone combination. Plans for future acoustics research will be discussed. [Work supported by the National Science Foundation.]
Seasonal and diurnal pattern of baleen whales detected on the Station Aloha Cabled Observatory off Oahu, Hawaii
Authors: Au Whitlow W. , Richlen Michael , Ou Hui , Howe Bruce
Published: November 2013

The ALOHA Cabled Observatory, ACO, located 100 km north of the island of Oahu, Hawaii, includes an acoustic recording package. The hydrophone is at a depth of 4.7 km and is connected to land via an underwater fiber optic cable. Recordings are continuous and made year-round. One year of data, 17 February 2007 to 18 February 2008, were analyzed to detect calls from blue (Balaenoptera musculus), fin (Balaenoptera physalus), sei (Balaenoptera borealis), and minke whales (Balaenoptera acutorostrata). As expected, detections of all four species were highly seasonal with most occurring during the winter months. While the exact migration routes are not well understood for these species, a pattern similar to the breeding/calving migrations of humpback whales would be anticipated. Fin whales were detected most often followed by minke, blue, and sei whales. No diurnal patterns were observed for the fin, sei, and minke whales; however, a diurnal pattern was evident for blue whales (59% of calls were made in the evening and nighttime hours). All of the species are very rarely seen in Hawaiian waters, and blue whales have never been detected during any visual surveys. Acoustics detections are essential for understanding the occurrence of these species in Hawaii.
Acoustical resonators: A versatile tool for bubble detection
Authors: Czerski Helen
Published: November 2013

It can be tricky to quantify bubble size distributions accurately, especially for broad distributions of sub-millimeter bubbles. One solution to the problem is an acoustical resonator, a device which has been developed over the past two or three decades for use in the ocean. A single broadband measurement can provide a detailed bubble size distribution for bubbles from 5 microns to 500 microns in radius. Resonators are physically robust, provide data which needs little post-processing, and they have the potential for use in many other situations. In the ocean, we have used it to understand bubble coatings, follow bubble dissolution, and monitor void fraction in real time. I will describe the current state of resonator technology, show ocean data, and discuss its potential advantages and disadvantages for use in other environments.
A cavitation detector for microbubble therapy based on the Stockwell transform
Authors: Caskey Charles F. , Kruse Dustin , Ferrara Katherine W.
Published: November 2013

Quantification of the wideband signal associated with bubble collapse is desirable to measure cavitation dosage during microbubble therapy. We have developed a cavitation detection algorithm based on time-frequency analysis with the Stockwell transform. This transform is ideal since it isolates cavitation transients in time and frequency at much higher resolution than other time-frequency methods. In this study, we acquired simultaneous high-speed images and acoustic signals from bubbles undergoing oscillation during acoustic pulses commonly used for permeability enhancement (Transmit: 1.5 MHz, 10-cycle, peak negative pressure range 150–500 kPa, Receive: 15 MHz cavitation detector). Above 200 kPa, linescan vs time images showed relative bubble expansion greater than 2 and echoes contained a wideband signal that coincided with bubble collapse. The Stockwell transform of detected echoes revealed wideband spectrums localized to the time of bubble collapse. After filtering below 4 MHz to reject linear echoes, the root mean square (RMS) of the spectral amplitude was obtained from the time-frequency decomposition, yielding peaks at cavitation transients. The magnitude of the Fourier transform of the RMS signal at 1.5 MHz provided a sensitive indicator for bubble collapse and differed significantly across pressures where cavitation occurred (p < 0.05,t-test). The proposed measurement provides a sensitive metric for cavitation activity during microbubble therapy.
Acoustic angiography ultrasound imaging can distinguish vascular differences in tumor cell lines
Authors: Shelton Sarah E. , Dunleavey James M. , Dudley Andrew C. , Dayton Paul A.
Published: November 2013

Acoustic Angiography is a novel ultrasound imaging technology for visualizing intravascular microbubble contrast agents. It uses a prototype dual-frequency transducer to transmit ultrasound pulses at a low frequency near microbubble resonance, and confocally receives higher frequency signal from the broadband microbubble response. By utilizing two widely separated frequencies (transmit at 4 MHz, receive at 30 MHz), it is possible to form a high-resolution image of the vascular structure without any tissue background. Both Acoustic Angiography and standard amplitude-modulation, nonlinear contrast perfusion imaging were used to compare the vascularity of xenograft tumors composed of two tumor cell sub-types with known differences in vascularity. In both image types, tumors were manually segmented in three dimensions and the percent of pixels containing contrast signal was computed. Acoustic Angiography imaging proved to be more sensitive to the vascular differences than standard nonlinear perfusion imaging. For a population of 16 animals, the sensitivity of Acoustic Angiography was 0.73, whereas the sensitivity of non-linear perfusion imaging was 0.13, given a significance level of 0.05. Additionally, two-sided t-tests showed a statistically significant difference between tumor types for Acoustic Angiography images (p = 0.0025), but not for standard nonlinear contrast imaging (p = 0.39).
Observed cumulative time delay between second harmonic and fundamental component of pressure wave fields propagating through ultrasound contrast agents
Authors: Demi Libertario , Russo Giovanna , Wijkstra Hessel , Mischi Massimo
Published: November 2013

To our knowledge, despite several studies on the propagation velocity of pressure wave fields through ultrasound contrast agents (UCAs) have been conducted, the variation of propagation velocity between the fundamental and second harmonic component generated during the propagation of ultrasound through UCAs has not been studied yet. For this purpose, transmission and backscattering measurements of pressure wave fields propagating through gelatin phantoms containing cylindrical cavities of different diameter, filled with different concentrations [0 to 240 μL/L] of SonoVue® contrast agent, are conducted. Different frequencies [2, 2.5, and 3 MHz] and mechanical indices [0.05, 0.1, and 0.2] are investigated. Moreover, measurements obtained with Definity® contrast agent are also analyzed. Results show the occurrence of a cumulative delay between the time signals related to the second harmonic and fundamental component, suggesting a smaller propagation velocity for the second harmonic as compared to the fundamental component. Moreover, this delay increases with increasing microbubble concentration and diameter of the cavity, it depends on mechanical index and frequency, and, most importantly, it is not observed in the absence of UCAs. These results may be relevant for contrast-enhanced ultrasonography, providing new possibilities to increase contrast-to-tissue ratios and to quantify UCA concentrations.
Preliminary studies on the relation between the audio-visual cues' perception and the approaching speed of electric vehicles
Authors: Maffei Luigi , Masullo Massimiliano , Di Gabriele Maria , Sorrentino Francesco
Published: November 2013

For decades, “quiet” and “zero” emission vehicles have been considered the challenge for researchers and for the industry. Today, despite the great results obtained in the fields of air and noise pollution, the electric vehicles (EV) and hybrid vehicles (HV) have raised an important question regarding the pedestrian safety. At the speed permitted in urban areas (<50 km/h), these vehicles are considerably quieter than the traditional ones powered by gasoline or diesel. Nevertheless the amount of auditory cues associated to the approaching of these vehicles can be reduced, and this can determine an increase of the risk of accidents for the pedestrians. Even though the recent studies on this problem are focused, mainly, on the minimum sound levels and on the spectral content of the approaching vehicles, further aspects of the semantic content's change of the event should be considered. In this paper, a preliminary investigation on the relationship, and possible incoherence, among the approaching speed of the vehicles, the auditory cues, and the semantic content was performed, and results are presented. For the investigation, an immersive virtual reality environment was used.
E-mobility as a constituent of the environment—Does it force a change of habits?
Authors: Schulte-Fortkamp Brigitte
Published: November 2013

The future of car manufacturing is strongly led by the introduction of the e mobile cars considering the society’s resources and its given economy with respect to acoustic ecology. Hence, no manufacturing questions will be raised, but the development of the e mobile cars related to the needs of the society’s changes will be discussed. As sound design is always related to the status of a society, the acceptance of e mobile cars will be related to the way the society forces this new lifestyle product. Soundscape can be considered as a dynamic system characterized by the time-dependent occurrence of particular sound events embedded in specific environments. Soundscape describe ambiances and combine the daily recurrent patterns of sound multi-factorial in the process of analysis. An adequate evaluation of environmental noise will reflect the continually varying acoustical scenery and its specific perception in context. Therefore, the main message is focused on that any ambiance whether it is urban or rural will be a kind of composition where sounds play an informative role. The information is not based on the loudness level, it is based on the meaning of the sound and people’s reaction to it.
What is the biggest threat to health and safety: Quiet or noisy vehicles?
Authors: Sandberg Ulf
Published: November 2013

It is assumed by US federal authorities that vehicles, driven in electric mode, either hybrid or pure electric vehicles, are so quiet that they are a safety hazard for pedestrians and cyclists in traffic. A regulation on this topic is already proposed in the United States, and in Europe, the Parliament has voted in favor of a similar regulation. ISO has worked out a measuring method for the “quietness” of vehicles; assuming that this can be used to require quiet vehicles to have some sound added. Based on earlier publications on this subject by the author, and reviewing some recent papers and reports, the author explores the assumed problem, and puts it in the perspective of traffic safety as well as the detrimental effects of noise on humans. Special concern is given to the relation between “quiet” and “noisy” vehicles. It is argued that it is far more justified to work in toward reducing the noise emission of the noisiest vehicles in traffic than adding noise to the quiet ones, as in any traffic situation, masking by other sounds is more important than the sound level per se, and masking is largely influenced by noisy trucks, busses, and motorcycles.
The cart before the horse? National noise policy for hybrid and electric vehicles
Authors: Weidemann Dennis , Blomberg Leslie D.
Published: November 2013

As the federal government proceeds to define noise policy for hybrid and electric vehicles, questions are being raised about the adequacy of information and science behind that policy. This paper identifies information required to produce effective noise policy for hybrid and electric vehicles, and examines federal policy with respect to those requirements. What do we need to know? What do we know? And most importantly, what don't we know?
Sound quality evaluation of an automotive horn
Authors: Kang Hee Soo , Lee Sang Kwon
Published: November 2013

The sound quality of horn is important in views of two points. One is that it should be loud. The other one is that it is nice for a driver to hear the sound. Therefore, the exterior sound due to horn is related to loudness. The sound radiated from horn should be loud and the sound depends on the design of horn by itself. However, the interior sound due to horn depends on two paths. One is airborne path. The other one is structure-borne path. The sound quality of horn inside a car is related to the combination of sounds transferred throughout both paths. In order to evaluate the sound quality inside a car, the objective method evaluating the sound quality due to both paths is need to be developed. The paper presents the method evaluating objectively the sound quality of a horn inside a car based on the spectrum analysis and the octave analysis.
Time reversal enabled elastic wave data communications using sensor arrays
Authors: Jin Yuanwei , Ying Yujie , Zhao Deshuang
Published: November 2013

The Data communication on pipe-like structures presents a unique opportunity for gas pipeline industry or oil drilling and exploration industry to meet the need for information transfer or data telemetry over a long distance. Typically, the operating environment under which the data telemetry is required for gas pipeline or oil drilling is not suitable for traditional communication modalities such as wireless radio communication, optical cable communication, or acoustic sound communication. Elastic waves are waves that can propagate over a long distance on solid medium such as metal pipes or strings. We have demonstrated experimentally the use of elastic wave for data communication over metal pipes in a single-input single-output configuration, which yields a data rate of 20 kb/s by time reversal pulse position modulation (TR-PPM). The result is obtained by exploring the reciprocity of elastic wave channel using time reversal without relying on additional processing techniques such as channel equalization or error control coding. In this paper, we report our experimental and theoretical investigation of TR-PPM scheme using sensor arrays to further improve the data communication throughput.
Nonlinear ultrasound simulation for heterogeneous nonlinear coefficient media
Authors: Varray François , Cachard Christian , Tortoli Piero , Basset Olvier
Published: November 2013

In medical ultrasound, the use of simulation tools is very common to develop and test new imaging strategies. The existing tools are mainly limited to the linear propagation of ultrasound waves in tissue. A specific difficulty is due to the fact that the nonlinearity of investigated media can be different at different depths and the local value of the nonlinear coefficient must be taken into account to provide realistic simulated images. CREANUIS is a new two-step tool to simulate ultrasound images of linear and nonlinear media. It is based on a generalized angular spectrum method to consider the nonlinear forward propagation with heterogeneous nonlinear map and uses a reconstruction algorithm to create the corresponding radio frequency image. The simulated linear images have been validated through the comparison with images provided by FieldII, the reference tool in linear ultrasound simulation. CREANUIS allows simulating various nonlinear imaging techniques such as amplitude modulation or pulse inversion. Examples of images obtained simulating tissues with heterogeneous coefficients of nonlinearity will be presented. The comparison with experimental images provided by the ULA-OP ultrasound system and a grayscale phantom highlight the performance of CREANUIS images. CREANUIS is freely available at http://www.creatis.insa-lyon.fr/site/fr/CREANUIS.
Transient, planar, nonlinear acoustical holography for reconstructing acoustic pressure and particle velocity fields
Authors: Niu Yaying , Zha Zheyu , Kim Yong-Joe
Published: November 2013

A steady-state, nonlinear nearfield acoustical holography procedure, based on the Westervelt Wave Equation (WWE), was developed by the authors of this article to accurately reconstruct nonlinear acoustic “pressure” fields. Here, a “transient,” nonlinear acoustic holography algorithm is introduced that can be used to reconstruct three-dimensional, nonlinear acoustic pressure as well as particle velocity fields from two-dimensional acoustic pressure data measured on a measurement plane. This procedure is based on the Kuznetsov Wave Equation (KWE) that is directly solved by applying temporal and spatial Fourier Transforms to the KWE. When compared to the WWE-based procedure, the proposed procedure can be used to reconstruct acoustic particle velocity fields in addition to acoustic pressure fields. It can also be applied to multi-frequency source cases where each frequency component can contain both linear and nonlinear components. The KWE-based procedure is validated by conducting four numerical simulations with: (1) an infinite-size panel vibrating at a single frequency, (2) a pulsating sphere with a bifrequency excitation, (3) a finite-size, vibrating panel generating bended wave rays, and (4) an ultrasound transducer with a transient excitation. The numerical results show that holographically projected acoustic fields match well with directly calculated ones.
Reversible quasi-holographic line-scan and circular aperture processing for acoustic imaging and feature isolation
Authors: Plotnick Daniel , Marston Phillip L. , Zartman David J. , Smith Anthony R.
Published: November 2013

One-dimensional line scans of objects by a collocated source/receiver can be processed via a linear quasi-holographic method [Baik et al., J. Acoustic Soc. Am. 130, 3838–3851 (2011)] to produce an image in a way that is reversible for signal isolation. Distinct image features such as those due to edge diffraction, specular reflection, or elastic effects can then be extracted in the image domain. Images are then reverse processed to allow examination of the isolated features in time and spectral domains and removal of clutter [Zartman et al., Proceedings of Meetings on Acoustics (POMA) (June, 2013), Vol. 19, p. 055011]. In related research monostatic data from a circular synthetic aperture may be reversibly processed in a way favorable for feature extraction [Marston et al., Proc. IEEE Oceans 2011 (2011)]. Experimental examples comparing extracted features with physical models will be discussed. [Work supported by ONR.]
Creation of coherent complex pressure measurements through overlapping scan-based measurements
Authors: Myres Jazmin S. , Gee Kent L. , Neilsen Tracianne B. , Wall Alan T.
Published: November 2013

In scan-based array measurements, stationary reference sensors are needed to temporally correlate the different measurement scans and produce coherent complex pressure fields. Because the number of references required increases with the number of subsources contributing to the sound field, an extended, partially correlated source (e.g., a turbulent jet) comprising many ill-defined sources can result in significantly increased measurement complexity. A different approach to creating spatiotemporally coherent pressures is demonstrated here. Military jet data have been used to explore “stitching” together a complex pressure field by spatially overlapping measurement scans instead of using separate reference channels. Various methods of stitching have been explored and the most robust method identified. Unwrapping of intrascan phases is first accomplished with a two-dimensional phase unwrapping algorithm. Individual scan positions are then stitched together using median phase differences between multiple adjacent scans to create coherent planes of data. Amplitude-stitching is done by averaging across scans and preserving the integrated squared pressure across the overall aperture. This method works well for low-frequency jet data, where there is not a ground-based interference null creating a physical phase discontinuity. This technique provides direction for efficient experimental design for scan-based array measurements of extended sources. [Work sponsored by ONR.]
Evolution of the wave steepening factor for high-amplitude sound propagation
Authors: Muhlestein Michael B. , Gee Kent L. , Nielsen Tracianne B. , Thomas Derek C.
Published: November 2013

One suggested metric to quantify nonlinear noise propagation is the wave steepening factor (WSF) [J. Gallagher, AIAA-82-0416 (1982)], defined as the absolute value of the mean negative slope of an entire waveform over the mean positive slope. Qualitatively, the WSF describes a waveform's average distortion, but a quantitative analysis has not been performed previously. To aid in the interpretation of the WSF, its evolution is presented in analytical fashion for the Earnshaw and Khokhlov solutions to the Burgers equation. Furthermore, the results of an analysis of the effects of finite sampling rates on the estimation of the wave steepening factor for these ideal cases are presented. A generalized Burgers equation-based model has been used to analyze the numerical evolution of the WSF for atmospheric and boundary layer absorption and dispersion and compare with plane wave tube experiments. From the numerical simulations, it is found that the WSF is dominated by initial level and frequency and is relatively less affected by absorption, bandwidth, and initial statistics for noise signals. Furthermore, the WSF is shown to be relatively insensitive to reduced sampling rates.
Deep water acoustic propagation in the northern Philippine Sea: Comparison of observed ray travel times with a non-acoustic state estimate
Authors: Cornuelle Bruce , Gopalakrishnan Ganesh , Dzieciuch Matthew , Worcester Peter
Published: November 2013

Six transceivers and one distributed vertical line array (DVLA) receiver were moored in the northern Philippine Sea from April 2010 to May 2011 for low-frequency (325 Hz and below), deep water propagation experiments. The shortest range was about 130 km and the longest about 640 km. A 2009 equipment test yielded travel times between a moored source and a more limited DVLA at about 185 km range along one of the 2010–2011 paths. Experimental goals included understanding the impacts of fronts, eddies, and internal tides on acoustic propagation and determining the utility of acoustic measurements for ocean state estimation. This presentation will report on comparisons between ray travel times computed in a state estimate for the Northern Philippine Sea excluding the ray data, and observations from the 2009 and 2010–2011 experiments. The state estimate uses satellite sea surface height and sea surface temperature observations as well as Argo and XBT profiles. Ray arrival times calculated from the state estimate will be compared to observations as a simple estimate of the novel information present in the data.
What acoustic travel-times tell us about the ocean
Authors: Powell Brian , Cornuelle Bruce , Kerry Colette
Published: November 2013

Measurements of acoustic ray travel-times in the ocean provide synoptic integrals of the ocean state between source and receiver. It is known that the ray travel-time is sensitive to variations in the ocean at the transmission time, but the sensitivity of the travel-time to spatial variations in the ocean prior to the acoustic transmission have not been quantified. Using an advanced numerical model, we can identify both the ocean dynamics that control the ocean state along a ray path and quantify the informational content of the ray travel-time observation. This study examines the sensitivity of ray travel-time to the temporally and spatially evolving ocean state in the Philippine Sea over a one year experiment. The travel-times are found to be sensitive to the internal tide generation prior to the sample time and to advective effects that alter density along the ray path. Temporal nonlinearity of these sensitivities suggest that prior knowledge of the ocean state is necessary to exploit the travel-time observations. After assimilating the travel-time observations, the contribution of the travel-time information to our estimation of the ocean state is quantified and evaluated to further identify what the travel-time observation reveals about the ocean.
Tomography and the global predictability of mode-1 internal tides
Authors: Dushaw Brian D.
Published: November 2013

Twenty years ago, temporally coherent, mode-1 internal tides were detected in the central North Pacific using acoustic tomography. The spatial sampling of tomography is a natural filter for these internal waves. The signals were conjectured to have originated from the Hawaiian Ridge 2000 km to the south, and shortly thereafter Ray and Michum found radiation of internal tides from that undersea ridge using satellite altimetry. The two data types are complementary: tomography demonstrates astonishing temporal coherence, altimetry demonstrates astonishing spatial coherence. In the Atlantic, diurnal internal tides, resonantly trapped between Puerto Rico and their 30N turning latitude, were observed by AMODE tomography, while the semidiurnal variability consisted of a complicated interference pattern. While several conventional in situ observations indicated incoherent components to mode-1 internal-tide variability, both tomography (directly) and altimetry (indirectly) show the incoherent component is minimal. Resolution of mode-1 is challenging, but, without basis, oceanographers have been reluctant to accept the tomography measurements. A combined frequency and wavenumber tidal analysis of altimetry data has recently demonstrated that the amplitude and phase of mode-1 internal tides are predictable, except, perhaps, in more variable regions. Attenuation appears to be negligible, and waves coherent in time and space extend across ocean basins.
Passive acoustic thermometry of the deep water sound channel using ambient noise
Authors: Woolfe Katherine F. , Lani Shane , Sabra Karim G.
Published: November 2013

Cross-correlation processing of ocean ambient noise has been proposed as a totally passive alternative to existing active methods for sensing the ocean environment such as acoustic tomography or acoustic thermometry. To this end, we investigated the spatial coherence of low frequency (f < 40 Hz) ocean noise recorded in the deep sound (SOFAR) channel to demonstrate the feasibility of passive acoustic thermometry. Continuous recordings of ambient noise obtained from hydroacoustic stations of the International Monitoring System were processed between the years 2006 and 2012. Each hydroacoustic station uses two triangular horizontal arrays separated by approximately 100 km, and each array has three hydrophones. Coherent arrivals were extracted from time-averaged cross-correlations between the two spatially separated triangular arrays. A beamforming procedure, using data-derived adaptive weights, was used to track the seasonal fluctuations of the arrival time of the coherent wavefronts throughout the 6 years. These measured travel-time fluctuations were estimated to primarily result from seasonal temperature fluctuations on the order of 0.1°C in the SOFAR channel, which is consistent with independent temperature measurements made by the Argo float global array in the vicinity of the hydroacoustic stations over the same time period.
Seasonal dependence of ambient noise in the North Pacific
Authors: Farrokhrooz Mehdi , Wage Kathleen E. , Dzieciuch Matthew A. , Worcester Peter F.
Published: November 2013

One characteristic of deep ocean noise is the decrease in ambient levels below the conjugate depth (Urick, 1975). Measurements made by Gaul et al. (JOE, 2007) and Morris (JASA, 1978) in the North Pacific indicate that the slope of the noise below the conjugate depth varies with location. Gaul et al.'s measurements show a much steeper slope than those of Morris, and this difference can be attributed to bathymetric effects (Shooter, JOE, 1990). The experiments described by Gaul et al. and Morris took place in September 1975 and September 1973, respectively. Noise levels measured during SPICEX in September 2004 are comparable to those recorded by Morris 31 years earlier. While the earlier experiments took place over 2–11 day periods, the SPICEX arrays were deployed for a year. Since the conjugate depth varies seasonally, it is expected that the noise profile also varies seasonally. This talk investigates the seasonal variations of noise in the SPICEX data set, focusing on the 10–100 Hz band. The analysis includes a discussion of the effects of local wind.
Seabed loss and dispersion analysis of broadband propagation data measured in deep water basin
Authors: Knobles David P. , Sagers Jason D.
Published: November 2013

Experimental acoustic data taken in a deep-water environment are analyzed for information on the intrinsic attenuation and volume scattering in the seabed. Sound Underwater Signaling (SUS) explosive sources were deployed in the Gulf of Oman basin with a water depth of about 3300 m. Received pressure time series were recorded on three hydrophones located at about 500, 1650, and 3200 m depth. The sound speed profile is downward refracting, and the seabed is a thick mud sediment with a sound speed ratio of less than unity. A positive sound speed depth gradient is the main mechanism that returns energy to the water column. The time series arrival structure for range scales of about 80 km is composed of a well-defined sequence of ray-like arrivals corresponding to an increasing number of bottom interactions with deeper turning points in the sediment. Time-frequency dispersion analyses of modeled and measured received time series in the 5–600 Hz band are applied in identifying the frequency dependence of loss mechanisms in the seabed. [Work supported by ONR.]
Free path statistics in coupled rooms
Authors: Vorlaender Michael
Published: November 2013

Statistics of free paths in room acoustics led to the statistical reverberation theory of diffuse fields in spaces and thus to the well-known reverberation formulas. The specific distribution of free paths, however, can also give a more specific insight into the sound field and its deviations from the expected result using the mean free paths. Recently, Hanyu (JASA 128, 1140, 2010) extended the statistical reverberation theory toward a separation of absorption effects and mixing effects by scattering. This approach can predict nonlinear decay curves and the transition of energy between specular and scattered processes. In the work presented here, a concept of Vorländer (J. Sound Vib. 232, 129, 2000) is revisited. Free path distributions are logged in the room simulation program RAVEN and displayed in real time with regard to the geometric configuration of coupled spaces, and to the influence of absorption and scattering at the boundaries. This allows the observation of the decay curves in dependence on the actual free path distribution. From this data, it is tried to further develop simple prediction scheme of decay curves in non-diffuse and coupled spaces.
Inferring delays between subrooms in systems of coupled rooms
Authors: Summers Jason E. , Botts Jonathan
Published: November 2013

Delay-differential-equation models of reverberant-energy decay in systems of coupled rooms were recently introduced as a semi-empirical correction to standard statistical-acoustics models in order to better account for the delay of energy transfer between subrooms of a coupled system [Summers, J. Acoust. Soc. Am. 132, EL129―EL134, 2012]. Here, a Bayesian approach to parameter estimation for these models is developed and evaluated on simulated and measured data. Using these data, the ability to invert for delays from measured decay curves is assessed and an interpretation of the physical meaning of those inferred delays is presented. Finally, the theoretical and mathematical relationships between higher-degree-of-freedom models resulting from the introduction of delay and those resulting from the introduction of additional decay rates to the standard sum-of-decaying-exponential model are considered, and the resulting implications for parameter estimation and model selection are described.
Room acoustical conditions in coupled video conference rooms
Authors: Gundersen Erlend I. , Svensson U. Peter
Published: November 2013

A video conferencing situation combines the acoustical properties of two rooms. The resulting convolution of the two room impulse responses leads to a total impulse response with a reverberation, which is not a classical exponential decay. As a consequence, relationships between parameters such as clarity and reverberation time will be significantly different from those in single rooms, and this will furthermore affect the combination's suitability for speech communication. In this study, a measurement survey is presented from 11 rooms with video conferencing equipment. Their volumes ranged from 24 to 117 m3, and their mid-range reverberation times were between 0.29 s and 0.70 s. Median values were 82 m3 and 0.41 s, respectively. Impulse responses were measured in all rooms and in a subsequent analysis stage, impulse response pairs were convolved, simulating a connection between the corresponding rooms. Those convolved IRs were analyzed in terms of clarity and reverberation time. Recommended parameter values for single rooms were used as guidelines to understand the qualities of convolved rooms.
Binaural effects in convolved room impulse responses
Authors: Reiter Ulrich , Svensson U. Peter
Published: November 2013

In situations like video and teleconferencing, the acoustical properties of two rooms are involved via a convolution of the two room impulse responses. Reverberation in the two rooms will play quite different roles since the sender room reverberation will partially reach the listener, in the receiver room, from the source direction. Therefore, binaural suppression of reverberation will be less efficient for parts of the total impulse response. Here, the situation is analyzed in terms of a simple room impulse response model with a direct sound followed by an ideal exponential decay. Such a model permits parametric studies, even of convolved impulse responses. Listening test results will quantify the importance of these binaural effects for the perceived quality of speech signals.
Acoustic feature extraction and classification in Ishmael
Authors: Mellinger David K.
Published: November 2013

Ishmael is a user-friendly bioacoustic analysis tool for Windows. It includes displays of sound waveforms and spectrograms, recording capability for real-time input, several methods for acoustic localization, beamforming, several methods for automatic call detection, and a sound annotation facility. Ishmael is intended for users wishing to analyze large volumes of data quickly and easily. Ishmael’s capabilities for classification now include a feature-extraction module that implements noise-resistant acoustic characterizations based on Fristrup’s AcouStat system (Fristrup, Woods Hole Tech. Rept. WHOI-92-04, 1992). These features can be used as input to classifier(s) connected to Ishmael and implemented in Matlab. Examples of cetacean (odontocete and mysticete) sound feature extraction and classification will be shown.
Identification of individual beaked whales in the northern Gulf of Mexico
Authors: Ioup Juliette W. , Ioup George E. , Tiemann Christopher O. , Sidorovskaia Natalia A. , Tashmukhambetov Arslan M.
Published: November 2013

Recent Littoral Acoustic Demonstration Center (LADC) multi-mooring Environmental Acoustic Recording System (EARS) data from the northern Gulf of Mexico are analyzed to deduce identifications of individual beaked whales. Procedures are built on previously applied self-organizing map techniques for clustering sperm whale clicks and beaked whale clicks from workshop data. Associating the clicks from beaked whales is difficult because, compared to sperm whales, beaked whales have lower source level, a narrower beam, and a faster rate of turning. Recordings of individual clicks can be clustered according to their time domain signal, frequency spectrum, or wavelet spectrum. For example, clicks clustered according to the magnitude of their frequency components show similarities for all the clicks in a class (representing an individual), but significant differences from class to class, suggesting that this approach has promise for identifying individuals. Recent work by Baggenstoss (J. Acoust. Soc. Am. 130, 102–112 (2011); J. Acoust. Soc. Am. 133, 4065–4076 (2013)), who has used cross correlations of clicks to assist in associating beaked whale clicks into trains, reinforces the idea that single click properties can be associated with individuals. [Research supported by SPAWAR and ONR.]
Dolphin biosonar target detection in noise, auditory filter shape, and temporal integration
Authors: Au Whitlow W.
Published: November 2013

The biosonar target detection in noise capability of the Atlantic bottlenose dolphin (Tursiops truncatus) has been studied as early as 1981 by Au and Penner. At that time, they presented results of the performance of two dolphins as a function of the signal energy to the density of the noise intensity (as in human psycho-acoustics) and not the signal energy to the noise energy ratio. Subsequently, two important pieces of information were determined, that is the auditory filter shape of the bottlenose dolphin in 2012 along with the temporal integration time for the reception of broadband biosonar echoes in 1988. In all but one experiment, it has been shown that the auditory system of odontocetes has a constant-Q characteristic. The biosonar detection capability of the bottlenose dolphin is revisited, and the target detection performance is now determined as a function of the received energy in the echo to the received noise energy. This presentation is an example of how some biosonar questions can only be answered after many years of related research and how sequences of research projects should be established so that current results can be applied to past results to gain a deeper understanding of the biosonar process.
Sperm whale coda repertoires in the western Pacific Ocean
Authors: Ferguson Elizabeth L. , Norris Thomas F. , Hom-Weaver Cory A. , Dunleavy Kerry J.
Published: November 2013

Sperm whales are social cetaceans that live in matrilineal family units, and inhabit all major ocean basins from the tropics to polar regions. They produce stereotyped patterns of 3 to 40 broadband clicks, termed “codas,” that typically occur within a period of less than 3 s. Coda repertoires can be assigned to a “vocal clan,” a type of social group used to define sperm whale population structure. Extensive studies of vocal clans have been conducted in the eastern tropical Pacific (ETP); however, little is known about sperm whale coda repertoires in the western Pacific. We reviewed codas recorded from independent sperm whale groups that were acoustically and visually encountered during two marine mammal surveys conducted in the Northern Mariana Islands (10 groups) and Palau region (3 groups), in 2007 and 2012, respectively. Three bioacousticians qualitatively classified codas to type, which indicated the presence of the “+1” and “regular” vocal clan. These data are now being analyzed using multivariate methods described by Rendell and Whitehead (2003) to quantitatively classify codas from each group. The identification of vocal clans within this region has implications for understanding the culturally linked stock distribution of sperm whales across the Pacific Ocean.
Using inter-click intervals to separate multiple odontocete click trains
Authors: Nosal Eva-Marie , Høst-Madsen Anders , Young Jeremy
Published: November 2013

We developed a method to separate click trains from multiple odontocetes that relies on click timing only. The method assumes that inter-click intervals (ICIs) are slowly varying and that their distribution is known, though possibly with unknown parameters. ICIs are modeled as a renewal process and click trains are separated by maximizing the likelihood of click assignments based on ICI distributions. We present results from application of this timing-based separation method to simulated and real datasets. [Work supported by the National Science Foundation and the Office of Naval Research.]
Whistle classification by spectrogram correlation
Authors: Lu Yang , Mellinger David
Published: November 2013

The spectral properties of whistles are investigated for sounds collected from six species of odontocetes in the North Pacific: bottlenose dolphins (Tursiops truncatus), melon-headed whales (Peponocephala electra), short- and long-beaked common dolphins (Delphinus delphis and D. capensis), and Hawaiian spinner dolphins (Stenella longirostris longirostris). The proposed method first uses the k-means algorithm to cluster whistles of each species into groups which represent their spectral contours. The features used for clustering are based on a method described by Mellinger et al. (J. Acoust. Soc. Am. 107, 3518-3529). Short spectrogram kernels of different slopes are cross-correlated with training data to obtain histograms of slopes and other acoustic properties. The features are used in a random forest classification algorithm. The classified whistles which belong to different clusters but the same species are merged together, resulting in classification to species. The performance of these methods, as evaluated via confusion matrices, is compared in terms of accuracy and complexity with other extant algorithms.
Robust recognition of whistle-like frequency contours by a bottlenose dolphin (Tursiops truncatus)
Authors: Branstetter Brian K. , Black Amy , Bakhtiari Kimberly , Trickey Jennifer
Published: November 2013

Whistle use by bottlenose dolphins serves several functions including individual identification, maintaining group cohesion, long-range communication, recruitment during feeding, and advertising emotional state. Whistles can vary considerably in amplitude, duration, and frequency. Despite this variability, dolphins must learn to associate specific whistle features (e.g., frequency contour) with meaningful events or objects, requiring plasticity in the dolphin’s recognition abilities. To test robust recognition, a bottlenose dolphin learned to associate whistle-like frequency contours with arbitrary objects. For example, whistle-A would cue the dolphin to touch object-A, and whistle-B would cue her to touch object-B. The whistles were then altered by varying amplitude, duration, and transposing frequency. Changes in amplitude and duration had little effect on recognition, however frequency transposition as small as 1/3 octave resulted in poor performance. The results are discussed from a comparative cognition perspective.
Discrimination of baleen whales frequency-modulated downsweep calls with overlapping frequencies
Authors: Ou Hui , Au Whitlow , Parijs Sofie V. , Oleson Erin M. , Rankin Shannon
Published: November 2013

Spectrograms generated with the pseudo Wigner-Ville distribution (PWVD) provide much higher simultaneous time-frequency (TF) resolution compared with the traditional method using the short time Fourier transform (STFT). The WV-type spectrogram allows bioacousticians to study the fine TF structures of the sound, such as the instantaneous frequency, instantaneous bandwidth, contour slope, etc. These features set the foundation of identifying sounds that are usually considered difficult to discriminate using the traditional method. However, the PWVD requires much higher computational effort than the STFT method. In this research, the advantage of the WV spectrogram analysis was demonstrated by a case study on frequency-modulated, downsweep sounds from fin whales, sei whales, and blue whales D-calls. These calls overlapped in frequency range and have similar time duration. Automatic detection of fin, sei or blue whales FM downsweeps using the traditional spectrogram methodology tend to be ineffective because of the large temporal ambiguities needed to achieve the necessary frequency resolution. However, their WV spectrograms showed distinguishable characteristics, for example, the TF contour of fin and sei whales exhibited concave and convex shapes respectively. A support vector machine (SVM) classifier was trained and tested based on the parameters extracted from the WV spectrograms.
The acoustic signature of the male northern elephant seal: Individual variation supports recognition during competitive interactions
Authors: Casey Caroline , Reichmuth Colleen , Fregosi Selene , Charrier Isabelle , Mathevon Nicolas
Published: November 2013

Northern elephant seals (Mirounga angustirostris) have a polygynous breeding system in which adult males establish dominance hierarchies that determine access to females. Acoustic signaling plays an important role in settling fights between males, as stereotyped displays elicit appropriate behavioral responses from individuals without contact during an energetically demanding breeding season. To determine whether reliable differences exist in the acoustic displays of individuals and whether these differences function to convey identity, we behaviorally and acoustically sampled male seals during the breeding season. Vocalizations were recorded during competitive interactions and analyzed for spectral, temporal, and amplitude characteristics. A cross-validated discriminant function analysis revealed small differences within—and significant differences between—the calls produced by 17 adult males of known dominance status. To determine whether acoustic displays serve as individual signatures that males learn to recognize during the breeding season, we conducted playback experiments to test if having prior experience with a particular caller would influence the approach or avoidance response of the listener. Our findings reveal that these unique acoustic signals serve as individual vocal signatures, and males likely remember the identity of their rivals based on call features that have been associated with the outcome of previous competitive interactions.
Detection of complex sounds in quiet and masked conditions by a California sea lion (Zalophus californianus) and a harbor seal (Phoca vitulina)
Authors: Cunningham Kane A. , Southall Brandon , Reichmuth Colleen
Published: November 2013

Standard audiometric data, such as absolute detection thresholds and critical ratios, are often used to inform noise-exposure limits for marine mammals. However, these data are traditionally generated using simple stimuli, such as pure-tones and flat-spectrum noise, while natural sounds tend to have more complex structure. In this experiment, detection thresholds for complex stimuli were obtained in (a) quiet and (b) masked conditions for one California sea lion and one harbor seal. For part (a), three stimuli types were synthesized, each isolating a common feature of marine mammal vocalizations: amplitude modulation (AM), frequency modulation (FM), and harmonic structure. Detection thresholds in quiet conditions were then obtained for these stimuli at frequencies spanning the functional hearing range. For part (b), the same complex signals were combined with flat-spectrum noise or shipping noise. To test how well standard hearing data predict detection of complex sounds, the results of parts (a) and (b) were compared to a priori predictions based on previously obtained audiogram and critical ratio data. Preliminary results indicate that absolute detection thresholds for AM and FM stimuli are reliably predicted by audiogram data, but that thresholds for harmonic stimuli are lower than predicted, in some cases by more than 10 dB.