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Jun 2010

Volume 127, Issue 6, pp. EL235-3881

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Ultrasonic wave propagation in stereo-lithographical bone replicas

Haydar Aygün, Keith Attenborough, Walter Lauriks, and Christian M. Langton

J. Acoust. Soc. Am. Volume 127, Issue 6, pp. 3781-3789 (2010); (9 pages) | Cited 1 time

Online Publication Date: 09 Jun 2010

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Predictions of a modified anisotropic Biot–Allard theory are compared with measurements of pulses centered on 100 kHz and 1 MHz transmitted through water-saturated stereo-lithographical bone replicas. The replicas are 13 times larger than the original bone samples. Despite the expected effects of scattering, which is neglected in the theory, at 100 kHz the predicted and measured transmitted waveforms are similar. However, the magnitude of the leading negative edge of the waveform is overpredicted, and the trailing parts of the waveforms are not predicted well. At 1 MHz, although there are differences in amplitudes, the theory predicts that the transmitted waveform is almost a scaled version of that incident in conformity with the data.
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43.80.Cs Acoustical characteristics of biological media: molecular species, cellular level tissues
43.80.Qf Medical diagnosis with acoustics
43.80.Vj Acoustical medical instrumentation and measurement techniques

Echolocation signals of a beaked whale at Palmyra Atoll

Simone Baumann-Pickering, Sean M. Wiggins, Ethan H. Roth, Marie A. Roch, Hans-Ulrich Schnitzler, and John A. Hildebrand

J. Acoust. Soc. Am. Volume 127, Issue 6, pp. 3790-3799 (2010); (10 pages) | Cited 6 times

Online Publication Date: 09 Jun 2010

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Acoustic recordings from Palmyra Atoll, northern Line Islands, central Pacific, showed upsweep frequency modulated pulses reminiscent of those produced by beaked whales. These signals had higher frequencies, broader bandwidths, longer pulse durations and shorter inter-pulse intervals than previously described pulses of Blainville’s, Cuvier’s and Gervais’ beaked whales [ Zimmer et al. (2005). J. Acoust. Soc. Am. 117, 3919–3927 ; Johnson et al. (2006). J. Exp. Biol. 209, 5038–5050 ; Gillespie et al. (2009). J. Acoust. Soc. Am. 125, 3428–3433 ]. They were distinctly different temporally and spectrally from the unknown beaked whale at Cross Seamount, HI [ McDonald et al. (2009). J. Acoust. Soc. Am. 125, 624–627 ]. Genetics on beaked whale specimens found at Palmyra Atoll suggest the presence of a poorly known beaked whale species. Mesoplodon sp. might be the source of the FM pulses described in this paper. The Palmyra Atoll FM pulse peak frequency was at 44 kHz with a −10 dB bandwidth of 26 kHz. Mean pulse duration was 355 μs and inter-pulse interval was 225 ms, with a bimodal distribution. Buzz sequences were detected with inter-pulse intervals below 20 ms and unmodulated spectra, with about 20 dB lower amplitude than prior FM pulses. These clicks had a 39 kHz bandwidth (−10 dB), peak frequency at 37 kHz, click duration 155 μs, and inter-click interval between 4 and 10 ms.
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43.80.Ka Sound production by animals: mechanisms, characteristics, populations, biosonar

Source level estimation of two blue whale subspecies in southwestern Indian Ocean

Flore Samaran, Christophe Guinet, Olivier Adam, Jean-François Motsch, and Yves Cansi

J. Acoust. Soc. Am. Volume 127, Issue 6, pp. 3800-3808 (2010); (9 pages) | Cited 3 times

Online Publication Date: 09 Jun 2010

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Blue whales produce intense, stereotypic low frequency calls that are particularly well suited for transmission over long distances. Because these calls vary geographically, they can be used to gain insight into subspecies distribution. In the Southwestern Indian Ocean, acoustic data from a triad of calibrated hydrophones maintained by the International Monitoring System provided data on blue whale calls from two subspecies: Antarctic and pygmy blue whales. Using time difference of arrival and least-squares hyperbolic methods, the range and location of calling whales were determined. By using received level of calls and propagation modeling, call source levels of both subspecies were estimated. The average call source level was estimated to 179±5 dB re 1 μParms at 1 m over the 17–30 Hz band for Antarctic blue whale and 174±1 dB re 1 μParms at 1 m over the 17–50 Hz band for pygmy blue whale. According to previous estimates, slight variations in the source level could be due to inter-individual differences, inter-subspecies variations and the calculation method. These are the first reported source level estimations for blue whales in the Indian Ocean. Such data are critical to estimate detection ranges of calling blue whales.
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43.80.Ka Sound production by animals: mechanisms, characteristics, populations, biosonar
43.30.Sf Acoustical detection of marine life; passive and active

Analysis and classification of broadband echoes using bio-inspired dolphin pulses

Yan Pailhas, Chris Capus, Keith Brown, and Patrick Moore

J. Acoust. Soc. Am. Volume 127, Issue 6, pp. 3809-3820 (2010); (12 pages) | Cited 2 times

Online Publication Date: 09 Jun 2010

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To date most sonars use narrow band pulses and often only the echo envelope is used for object detection and classification. This paper considers the advantages afforded by bio-inspired sonar for object identification and classification through the analysis and the understanding of the broadband echo structure. Using the biomimetic dolphin based sonar system in conjunction with bio-inspired pulses developed from observations of bottlenose dolphins performing object identification tasks, results are presented from experiments carried out in a wave tank and harbor. In these experiments responses of various targets to two different bio-inspired signals are measured and analyzed. The differences in response demonstrate the strong dependency between signal design and echo interpretation. In the simulations and empirical data, the resonance phenomena of these targets cause strong notches and peaks in the echo spectra. With precision in the localization of these peaks and dips of around 1 kHz, the locations are very stable for broadside insonification of the targets and they can be used as features for classification. This leads to the proposal of a broadband classifier which operates by extracting the notch positions in the target echo spectra.
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43.80.Ka Sound production by animals: mechanisms, characteristics, populations, biosonar
43.60.Bf Acoustic signal detection and classification, applications to control systems

Changes in consistency patterns of click frequency content over time of an echolocating Atlantic bottlenose dolphin

Stuart D. Ibsen, Whitlow W. L. Au, Paul E. Nachtigall, Caroline M. DeLong, and Marlee Breese

J. Acoust. Soc. Am. Volume 127, Issue 6, pp. 3821-3829 (2010); (9 pages) | Cited 3 times

Online Publication Date: 09 Jun 2010

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Echolocation clicks were recorded from an Atlantic bottlenose dolphin Tursiops truncatus trained to discriminate frequency filtered phantom targets in 1998 and in 2004. These clicks showed consistency within their spectra intensity profiles but only in a certain band of frequencies. In 2004 almost all the clicks were consistent within the 0–42 kHz band regardless of the presented target or the click source level. This region corresponded with previous data showing that in 2004 the dolphin perceived frequencies only from within the 29–42 kHz band during echolocation. Above 42 kHz the consistency was lost. In 1998 the consistent region was found only in the 90–100 kHz band showing a shift had occurred with time. This suggests the dolphin’s echolocation strategy for these discrimination tasks centered on the use of clicks with the same controlled standard frequency content in a certain frequency band to investigate different targets. This consistent region shifted over time to maintain maximum signal to noise ratio of the echoes given certain changing limitations to the echolocation system. The shift in consistency over time indicates these consistent regions were not simply artifacts of click production but rather an active control of frequency content.
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43.80.Ka Sound production by animals: mechanisms, characteristics, populations, biosonar
43.80.Ev Acoustical measurement methods in biological systems and media
43.80.Gx Mechanisms of action of acoustic energy on biological systems: physical processes, sites of action
43.80.Lb Sound reception by animals: anatomy, physiology, auditory capacities, processing

Target distance-dependent variation of hearing sensitivity during echolocation in a false killer whale

Alexander Ya. Supin, Paul E. Nachtigall, and Marlee Breese

J. Acoust. Soc. Am. Volume 127, Issue 6, pp. 3830-3836 (2010); (7 pages) | Cited 2 times

Online Publication Date: 09 Jun 2010

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Evidence of varying hearing sensitivity according to the target distance was obtained in a false killer whale Pseudorca crassidens during echolocation. Auditory evoked potentials (AEPs) triggered by echolocation clicks were recorded. The target distance varied from 1 to 6 m. The records contained AEPs to the self-heard emitted click and AEPs to the echoes. Mean level of echolocation clicks depended on distance (the longer the distance, the higher the click level), however, the effect of click level on AEP amplitude was eliminated by extracting AEPs to clicks of certain particular levels. The amplitude of the echo-provoked AEP was almost independent of distance, however, the amplitude of the AEP to the emitted click, did depend on distance within a range from 1 to 4 m: the longer the distance, the higher the amplitude. The latter result is interpreted as confirmational evidence that the animal is capable of varying hearing sensitivity according to target distance. The variation of hearing sensitivity may help to compensate for the echo attenuation with distance; as a secondary effect, this variation manifested itself in a variation of the amplitude of the AEP to emitted clicks.
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43.80.Lb Sound reception by animals: anatomy, physiology, auditory capacities, processing

Use of binaural cues for sound localization in large and small non-echolocating bats: Eidolon helvum and Cynopterus brachyotis

Rickye S. Heffner, Gimseong Koay, and Henry E. Heffner

J. Acoust. Soc. Am. Volume 127, Issue 6, pp. 3837-3845 (2010); (9 pages)

Online Publication Date: 09 Jun 2010

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The authors determined the ability of two old-world non-echolocating bats, Eidolon helvum and Cynopterus brachyotis, to use binaural time and intensity difference cues for localization. The bats were trained to localize pure tones throughout most of their hearing range from loudspeakers located 30° to the left and right of midline. Both species easily localized high frequency tones, indicating they could use the interaural intensity difference cue. However, neither was able to localize low frequency tones even when the tones were amplitude modulated thereby indicating that they could not use ongoing phase difference cues. The authors now know of eight mammals that do not use binaural phase cues for localization, and some possible reasons for this inability are explored.
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43.80.Lb Sound reception by animals: anatomy, physiology, auditory capacities, processing
43.80.Jz Use of acoustic energy (with or without other forms) in studies of structure and function of biological systems

Material characterization of the encapsulation of an ultrasound contrast microbubble and its subharmonic response: Strain-softening interfacial elasticity model

Shirshendu Paul, Amit Katiyar, Kausik Sarkar, Dhiman Chatterjee, William T. Shi, and Flemming Forsberg

J. Acoust. Soc. Am. Volume 127, Issue 6, pp. 3846-3857 (2010); (12 pages) | Cited 7 times

Online Publication Date: 09 Jun 2010

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Two nonlinear interfacial elasticity models—interfacial elasticity decreasing linearly and exponentially with area fraction—are developed for the encapsulation of contrast microbubbles. The strain softening (decreasing elasticity) results from the decreasing association between the constitutive molecules of the encapsulation. The models are used to find the characteristic properties (surface tension, interfacial elasticity, interfacial viscosity and nonlinear elasticity parameters) for a commercial contrast agent. Properties are found using the ultrasound attenuation measured through a suspension of contrast agent. Dynamics of the resulting models are simulated, compared with other existing models and discussed. Imposing non-negativity on the effective surface tension (the encapsulation experiences no net compressive stress) shows “compression-only” behavior. The exponential and the quadratic (linearly varying elasticity) models result in similar behaviors. The validity of the models is investigated by comparing their predictions of the scattered nonlinear response for the contrast agent at higher excitations against experimental measurement. All models predict well the scattered fundamental response. The nonlinear strain softening included in the proposed elastic models of the encapsulation improves their ability to predict subharmonic response. They predict the threshold excitation for the initiation of subharmonic response and its subsequent saturation.
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43.80.Qf Medical diagnosis with acoustics
43.25.Yw Nonlinear acoustics of bubbly liquids
43.40.Ga Nonlinear vibration
43.35.Mr Acoustics of viscoelastic materials
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