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  • 1
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    Caller sex and orientation influence spectral characteristics of “two-voice” stereotyped calls produced by free-ranging killer whales (2008)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © Acoustical Society of America, 2007. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 121 (2007): 3932-3937, doi:10.1121/1.2722056.
    Description: This study investigates how particular received spectral characteristics of stereotyped calls of sexually dimorphic adult killer whales may be influenced by caller sex, orientation, and range. Calls were ascribed to individuals during natural behavior using a towed beamforming array. The fundamental frequency of both high-frequency and low-frequency components did not differ consistently by sex. The ratio of peak energy within the fundamental of the high-frequency component relative to summed peak energy in the first two low-frequency component harmonics, and the number of modulation bands off the high-frequency component, were significantly greater when whales were oriented towards the array, while range and adult sex had little effect. In contrast, the ratio of peak energy in the first versus second harmonics of the low-frequency component was greater in calls produced by adult females than adult males, while orientation and range had little effect. The dispersion of energy across harmonics has been shown to relate to body size or sex in terrestrial species, but pressure effects during diving are thought to make such a signal unreliable in diving animals. The observed spectral differences by signaler sex and orientation suggest that these types of information may be transmitted acoustically by freely diving killer whales.
    Description: Funding was provided by WHOI’s Rinehart Coastal Research Center and Ocean Ventures Fund, and a Royal Society USA/Canada fellowship to PJOM.
    Keywords: Bioacoustics ; Underwater sound
    Repository Name: Woods Hole Open Access Server
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  • 2
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    Off-axis effects on the multipulse structure of sperm whale usual clicks with implications for sound production (2008)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © Acoustical Society of America, 2005. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 118 (2005): 3337-3345, doi:10.1121/1.2082707.
    Description: Sperm whales (Physeter macrocephalus) produce multipulsed clicks with their hypertrophied nasal complex. The currently accepted view of the sound generation process is based on the click structure measured directly in front of, or behind, the whale where regular interpulse intervals (IPIs) are found between successive pulses in the click. Most sperm whales, however, are recorded with the whale in an unknown orientation with respect to the hydrophone where the multipulse structure and the IPI do not conform to a regular pulse pattern. By combining far-field recordings of usual clicks with acoustic and orientation information measured by a tag on the clicking whale, we analyzed clicks from known aspects to the whale. We show that a geometric model based on the bent horn theory for sound production can explain the varying off-axis multipulse structure. Some of the sound energy that is reflected off the frontal sac radiates directly into the water creating an intermediate pulse p1/2 seen in off-axis recordings. The powerful p1 sonar pulse exits the front of the junk as predicted by the bent-horn model, showing that the junk of the sperm whale nasal complex is both anatomically and functionally homologous to the melon of smaller toothed whales.
    Description: This work was funded by grants to from the Office of Naval Research Grant Nos. N00014-99-1-0819 and No. N00014-01-1-0705, and the Packard Foundation.
    Keywords: Bioacoustics ; Underwater sound ; Biocommunications
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  • 3
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    Differences between sound scattering by weakly scattering spheres and finite-length cylinders with applications to sound scattering by zooplankton (2008)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 1998. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 103 (1998): 254-264, doi:10.1121/1.421135.
    Description: A modeling study was conducted to determine the conditions under which fluidlike zooplankton of the same volume but different shapes (spherical/cylindrical) have similar or dramatically different scattering properties. Models of sound scattering by weakly scattering spheres and cylinders of finite length used in this analysis were either taken from other papers or derived and herein adapted for direct comparison over a range of conditions. The models were examined in the very low- (ka ≪ 1, kL ≪ 1), moderately low- (ka ≪ 1, kL ≳ 1), and high-frequency regions (ka ≫ 1, kL ≫ 1), where k is the acoustic wave number, a is the radius (spherical or cylindrical) of the body, and L is the length of the cylinders (for an elongated body with L/a = 10, "moderately low" corresponds to the range 0.1 ≲ ka ≲ 0.5). Straight and bent cylinder models were evaluated for broadside incidence, end-on incidence, and averages over various distributions of angle of orientation. The results show that for very low frequencies and for certain distributions of orientation angles at high frequencies, the averaged scattering by cylinders will be similar, if not identical, to the scattering by spheres of the same volume. Other orientation distributions of the cylinders at high frequencies produce markedly different results. Furthermore, over a wide range of orientation distributions the scattering by spheres is dramatically different from that of the cylinders in the moderately low-frequency region and in the Rayleigh/geometric transition region: (1) the Rayleigh to geometric scattering turning point occurs at different points for the two cases when the bodies are constrained to have the same volume and (2) the functional dependence of the scattering levels upon the volume of the bodies in the moderately low-frequency region is quite often different between the spheres and cylinders because of the fact that the scattering by the cylinders is still directional in this region. The study demonstrates that there are indeed conditions under which different shaped zooplankton of the same volume will yield similar (ensemble average) scattering levels, but generally the shape and orientation distribution of the elongated bodies must be taken into account for accurate predictions.
    Description: This work was supported by the U.S. Office of Naval Research Grant No. N00014-95-1-0287 and the National Science Foundation Grant No. OCE-9201264.
    Keywords: Acoustic wave scattering ; Bioacoustics
    Repository Name: Woods Hole Open Access Server
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  • 4
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    Sound scattering by several zooplankton groups. II. Scattering models (2008)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 1998. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 103 (1998): 236-253, doi:10.1121/1.421110.
    Description: Mathematical scattering models are derived and compared with data from zooplankton from several gross anatomical groups—fluidlike, elastic shelled, and gas bearing. The models are based upon the acoustically inferred boundary conditions determined from laboratory backscattering data presented in part I of this series [Stanton et al., J. Acoust. Soc. Am. 103, 225–235 (1998)]. The models use a combination of ray theory, modal-series solution, and distorted wave Born approximation (DWBA). The formulations, which are inherently approximate, are designed to include only the dominant scattering mechanisms as determined from the experiments. The models for the fluidlike animals (euphausiids in this case) ranged from the simplest case involving two rays, which could qualitatively describe the structure of target strength versus frequency for single pings, to the most complex case involving a rough inhomogeneous asymmetrically tapered bent cylinder using the DWBA-based formulation which could predict echo levels over all angles of incidence (including the difficult region of end-on incidence). The model for the elastic shelled body (gastropods in this case) involved development of an analytical model which takes into account irregularities and discontinuities of the shell. The model for gas-bearing animals (siphonophores) is a hybrid model which is composed of the summation of the exact solution to the gas sphere and the approximate DWBA-based formulation for arbitrarily shaped fluidlike bodies. There is also a simplified ray-based model for the siphonophore. The models are applied to data involving single pings, ping-to-ping variability, and echoes averaged over many pings. There is reasonable qualitative agreement between the predictions and single ping data, and reasonable quantitative agreement between the predictions and variability and averages of echo data.
    Description: This work was supported by the National Science Foundation Grant No. OCE-9201264, the U.S. Office of Naval Research Grant Nos. N00014-89-J-1729, N00014-95-1-0287, and N00014-94-1-0452, and the MIT/WHOI Joint Graduate Education Program.
    Keywords: Backscatter ; Acoustic wave scattering ; Bioacoustics
    Repository Name: Woods Hole Open Access Server
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  • 5
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    Sound scattering by several zooplankton groups. I. Experimental determination of dominant scattering mechanisms (2008)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 1998. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 103 (1998): 225-235, doi:10.1121/1.421469.
    Description: The acoustic scattering properties of live individual zooplankton from several gross anatomical groups have been investigated. The groups involve (1) euphausiids (Meganyctiphanes norvegica) whose bodies behave acoustically as a fluid material, (2) gastropods (Limacina retroversa) whose bodies include a hard elastic shell, and (3) siphonophores (Agalma okeni or elegans and Nanomia cara) whose bodies contain a gas inclusion (pneumatophore). The animals were collected from ocean waters off New England (Slope Water, Georges Bank, and the Gulf of Maine). The scattering properties were measured over parts or all of the frequency range 50 kHz to 1 MHz in a laboratory-style pulse-echo setup in a large tank at sea using live fresh specimens. Individual echoes as well as averages and ping-to-ping fluctuations of repeated echoes were studied. The material type of each group is shown to strongly affect both the overall echo level and pattern of the target strength versus frequency plots. In this first article of a two-part series, the dominant scattering mechanisms of the three animal types are determined principally by examining the structure of both the frequency spectra of individual broadband echoes and the compressed pulse (time series) output. Other information is also used involving the effect on overall levels due to (1) animal orientation and (2) tissue in animals having a gas inclusion (siphonophores). The results of this first paper show that (1) the euphausiids behave as weakly scattering fluid bodies and there are major contributions from at least two parts of the body to the echo (the number of contributions depends upon angle of orientation and shape), (2) the gastropods produce echoes from the front interface and possibly from a slow-traveling circumferential (Lamb) wave, and (3) the gas inclusion of the siphonophore dominates the echoes, but the tissue plays a role in the scattering and is especially important when analyzing echoes from individual animals on a ping-by-ping basis. The results of this paper serve as the basis for the development of acoustic scattering models in the companion paper [Stanton et al., J. Acoust. Soc. Am. 103, 236–253 (1998)].
    Description: This work was supported by the National Science Foundation Grant No. OCE- 9201264, the U.S. Office of Naval Research Grant Nos. N00014-89-J-1729 and N00014-95-1-0287, and the MIT/ WHOI Joint Graduate Education Program.
    Keywords: Bioacoustics ; Acoustic wave scattering ; Fluctuations
    Repository Name: Woods Hole Open Access Server
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  • 6
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    Acoustic scattering by benthic and planktonic shelled animals (2008)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 2000. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 108 (2000): 535-550, doi:10.1121/1.429584.
    Description: Acoustic backscattering measurements and associated scattering modeling were recently conducted on a type of benthic shelled animal that has a spiral form of shell (Littorina littorea). Benthic and planktonic shelled animals with this shape occur on the seafloor and in the water column, respectively, and can be a significant source of acoustic scattering in the ocean. Modeling of the scattering properties allows reverberation predictions to be made for sonar performance predictions as well as for detection and classification of animals for biological and ecological applications. The studies involved measurements over the frequency range 24 kHz to 1 MHz and all angles of orientation in as small as 1° increments. This substantial data set is quite revealing of the physics of the acoustic scattering by these complex shelled bodies and served as a basis for the modeling. Specifically, the resonance structure of the scattering was strongly dependent upon angle of orientation and could be traced to various types of rays (e.g., subsonic Lamb waves and rays entering the opercular opening). The data are analyzed in both the frequency and time domain (compressed pulse processing) so that dominant scattering mechanisms could be identified. Given the complexity of the animal body (irregular elastic shell with discontinuities), approximate scattering models are used with only the dominant scattering properties retained. Two models are applied to the data, both approximating the body as a deformed sphere: (1) an averaged form of the exact modal-series-based solution for the spherical shell, which is used to estimate the backscattering by a deformed shell averaged over all angles of orientation, and produces reasonably accurate predictions over all k1aesr (k1 is the acoustic wave number of the surrounding water and aesr is the equivalent spherical radius of the body), and (2) a ray-based formula which is used to estimate the scattering at fixed angle of orientation, but only for high k1aesr. The ray-based model is an extension of a model recently developed for the shelled zooplankton Limacina retroversa that has a shape similar to that of the Littorina littorea but swims through the water [Stanton et al., J. Acoust. Soc. Am. 103, 236–253 (1998b)]. Applications of remote detection and classification of the seafloor and water column in the presence of shelled animals are discussed.
    Description: This work was supported by the U.S. Office of Naval Research Grant Nos. N00014-95-1- 0287 and N00014-96-1-0878, and the MIT/WHOI Joint Graduate Education Program.
    Keywords: Bioacoustics ; Acoustic wave scattering ; Backscatter ; Reverberation ; Underwater sound
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  • 7
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    Application of pulse compression techniques to broadband acoustic scattering by live individual zooplankton (2008)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 1998. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 104 (1998): 39-55, doi:10.1121/1.424056.
    Description: Distinct frequency dependencies of the acoustic backscattering by zooplankton of different anatomical groups have been observed in our previous studies [Chu et al., ICES J. Mar. Sci. 49, 97–106 (1992); Stanton et al., ICES J. Mar. Sci. 51, 505–512 (1994)]. Based mainly on the spectral information, scattering models have been proposed to describe the backscattering mechanisms of different zooplankton groups [Stanton et al., J. Acoust. Soc. Am. 103, 236–253 (1998b)]. In this paper, an in-depth study of pulse compression (PC) techniques is presented to characterize the temporal, spectral, and statistical signatures of the acoustic backscattering by zooplankton of different gross anatomical classes. Data collected from various sources are analyzed and the results are consistent with our acoustic models. From compressed pulse (CP) outputs for all three different zooplankton groups, two major arrivals from different parts of the animal body can be identified: a primary and a secondary arrival. (1) Shrimplike animals (Euphausiids and decapod shrimp; near broadside incidence only): the primary one is from the front interface (interface closest to the transducer) of the animal and the secondary arrival is from the back interface; (2) gas-bearing animals (Siphonophores): the primary arrival is from the gas inclusion and the secondary arrival is from the body tissue ("local acoustic center of mass"); and (3) elastic shelled animals (Gastropods): the primary one is from the front interface and the secondary arrival corresponds to the subsonic Lamb wave that circumnavigates the surface of the shell. Statistical analysis of these arrivals is used to successfully infer the size of the individual animals. In conjunction with different aspects of PC techniques explored in this paper, a concept of partial wave target strength (PWTS) is introduced to describe scattering by the different CP highlights. Furthermore, temporal gating of the CP output allows rejection of unwanted signals, improves the output signal-to-noise ratio (SNR) of the spectra of selected partial waves of interest, and provides a better understanding of the scattering mechanism of the animals. In addition, it is found that the averaged PWTS can be used to obtain a more quantitative scattering characterization for certain animals such as siphonophores.
    Description: This work was supported by the National Science Foundation under Grant No. OCE-9201264 and the U.S. Office of Naval Research under Grant Nos. N00014-89-J-1729, N00014-94-1-0452, and N00014-95-1-0287.
    Keywords: Matched filters ; Acoustic signal processing ; Backscatter ; Acoustic wave scattering ; Statistical analysis ; Bioacoustics
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  • 8
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    A phase-compensated distorted wave Born approximation representation of the bistatic scattering by weakly scattering objects : application to zooplankton (2008)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 1999. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 106 (1999): 1732-1743, doi:10.1121/1.428036.
    Description: The distorted wave Born approximation (DWBA) method has been successfully used in modeling the acoustic backscattering by weakly scattering zooplankton [Stanton et al., J. Acoust. Soc. Am. 94, 3463–3472 (1993), Wiebe et al., IEEE J. Ocean. Eng. 22(3), 445–464 (1997)]. However, the previously developed DWBA model ignores the imaginary part of the scattering amplitude and thus results in a zero-extinction cross section. As a consequence, the model fails to predict the scattering-induced attenuation which could be important under certain circumstances. In this paper, a phase-compensated DWBA-based approximation is presented. The improved method allows us to compute not only the scattering strength but also the acoustic attenuation. The new scattering model is validated by comparing with the existing exact solution for certain representative finite objects. The results from this study can be applied to bioacoustic applications where the attenuation due to scattering and/or multiple scattering by zooplankton is relevant, and where this information might be used to infer the acoustic properties of live animals.
    Description: This work was partially supported by the National Science Foundation under Grant No. OCE-9730680.
    Keywords: DWBA ; Backscatter ; Acoustic wave scattering ; Bioacoustics
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  • 9
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    Low-frequency components in harbor porpoise (Phocoena phocoena) clicks : communication signal, by-products, or artifacts? (2009)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 2008. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 124 (2008): 4059-4068, doi:10.1121/1.2945154.
    Description: Underwater sound signals for biosonar and communication normally have different source properties to serve the purposes of generating efficient acoustic backscatter from small objects or conveying information to conspecifics. Harbor porpoises (Phocoena phocoena) are nonwhistling toothed whales that produce directional, narrowband, high-frequency (HF) echolocation clicks. This study tests the hypothesis that their 130 kHz HF clicks also contain a low-frequency (LF) component more suited for communication. Clicks from three captive porpoises were analyzed to quantify the LF and HF source properties. The LF component is 59 (S.E.M=1.45 dB) dB lower than the HF component recorded on axis, and even at extreme off-axis angles of up to 135°, the HF component is 9 dB higher than the LF component. Consequently, the active space of the HF component will always be larger than that of the LF component. It is concluded that the LF component is a by-product of the sound generator rather than a dedicated pulse produced to serve communication purposes. It is demonstrated that distortion and clipping in analog tape recorders can explain some of the prominent LF components reported in earlier studies, emphasizing the risk of erroneous classification of sound types based on recording artifacts.
    Description: This work was supported by the Carlsberg Foundation and Oticon, and via a Steno Scholarship from the Danish Natural Science Research Council to PTM.
    Keywords: Bioacoustics ; Mechanoception ; Underwater sound ; Zoology
    Repository Name: Woods Hole Open Access Server
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  • 10
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    Propagation of narrow-band-high-frequency clicks : measured and modeled transmission loss of porpoise-like clicks in porpoise habitats (2010)
    Acoustical Society of America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Acoustical Society of America, 2010. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 127 (2010): 560-567, doi:10.1121/1.3257203.
    Description: Estimating the range at which harbor porpoises can detect prey items and environmental objects is integral to understanding their biosonar. Understanding the ranges at which they can use echolocation to detect and avoid obstacles is particularly important for strategies to reduce bycatch. Transmission loss (TL) during acoustic propagation is an important determinant of those detection ranges, and it also influences animal detection functions used in passive acoustic monitoring. However, common assumptions regarding TL have rarely been tested. Here, TL of synthetic porpoise clicks was measured in porpoise habitats in Canada and Denmark, and field data were compared with spherical spreading law and ray-trace (Bellhop) model predictions. Both models matched mean observations quite well in most cases, indicating that a spherical spreading law can usually provide an accurate first-order estimate of TL for porpoise sounds in porpoise habitat. However, TL varied significantly (±10 dB) between sites and over time in response to variability in seafloor characteristics, sound-speed profiles, and other short-timescale environmental fluctuations. Such variability should be taken into account in estimates of the ranges at which porpoises can communicate acoustically, detect echolocation targets, and be detected via passive acoustic monitoring.
    Description: Field data collection was partially supported by a Student Research Award from the WHOI Ocean Life Institute (Grant No. 25051351). P.T.M. and M.H. were funded by Steno and frame grants from the Danish Natural Science Foundation.
    Keywords: Bioacoustics ; Biocommunications ; Mechanoception ; Underwater acoustic propagation ; Zoology
    Repository Name: Woods Hole Open Access Server
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