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May 2012

Volume 131, Issue 5, pp. EL355-4232

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Characteristics of whistles from rough-toothed dolphins (Steno bredanensis) in Rio de Janeiro coast, southeastern Brazil

Isabela Maria Seabra de Lima, Luciana Guimarães de Andrade, Rafael Ramos de Carvalho, José Lailson-Brito, and Alexandre de Freitas Azevedo

J. Acoust. Soc. Am. Volume 131, Issue 5, pp. 4173-4181 (2012); (9 pages) | Cited 1 time

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There is no information about the whistles of rough-toothed dolphins in the South Atlantic Ocean. This study characterizes the whistle structure of free-ranging rough-toothed dolphins recorded on the Rio de Janeiro coast, southeastern Brazil, and compares it to that of the same species in other regions. A total of 340 whistles were analyzed. Constant (N = 115; 33.8%) and ascending (N = 99; 29.1%) whistles were the most common contours. The whistles recorded had their fundamental frequencies between 2.24 and 13.94 kHz. Whistles without inflection points were frequently emitted (N = 255; 75%). Some signals presented breaks or steps in their contour (N = 97; 28.5%). Whistle duration was short (347 ± 236 ms and 89.7% of the whistles lasted <600 ms). Seventy-eight whistle contour types were found in the total of whistles analyzed, and 27 (7.9%) of these occurred only once. Most of the whistle types were unique to a particular recording session (N = 43). The signals emitted by the rough-toothed dolphins in southeastern Brazil were characterized by low frequency modulation, short duration, low number of inflection points, and breaks. Differences in the mean values of the whistle parameters were found between this and other studies that recorded Steno bredanensis, but as in other localities, whistles above 14 kHz are rare.
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43.80.Ka Sound production by animals: mechanisms, characteristics, populations, biosonar

Underwater psychophysical audiogram of a young male California sea lion (Zalophus californianus)

Jason Mulsow, Dorian S. Houser, and James J. Finneran

J. Acoust. Soc. Am. Volume 131, Issue 5, pp. 4182-4187 (2012); (6 pages) | Cited 1 time

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Auditory evoked potential (AEP) data are commonly obtained in air while sea lions are under gas anesthesia; a procedure that precludes the measurement of underwater hearing sensitivity. This is a substantial limitation considering the importance of underwater hearing data in designing criteria aimed at mitigating the effects of anthropogenic noise exposure. To determine if some aspects of underwater hearing sensitivity can be predicted using rapid aerial AEP methods, this study measured underwater psychophysical thresholds for a young male California sea lion (Zalophus californianus) for which previously published aerial AEP thresholds exist. Underwater thresholds were measured in an aboveground pool at frequencies between 1 and 38 kHz. The underwater audiogram was very similar to those previously published for California sea lions, suggesting that the current and previously obtained psychophysical data are representative for this species. The psychophysical and previously measured AEP audiograms were most similar in terms of high-frequency hearing limit (HFHL), although the underwater HFHL was sharper and occurred at a higher frequency. Aerial AEP methods are useful for predicting reductions in the HFHL that are potentially independent of the testing medium, such as those due to age-related sensorineural hearing loss.
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43.80.Lb Sound reception by animals: anatomy, physiology, auditory capacities, processing
43.64.Ri Evoked responses to sounds

Sound level discrimination by gray treefrogs in the presence and absence of chorus-shaped noise

Mark A. Bee, Alejandro Vélez, and James D. Forester

J. Acoust. Soc. Am. Volume 131, Issue 5, pp. 4188-4195 (2012); (8 pages) | Cited 2 times

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An important aspect of hearing and acoustic communication is the ability to discriminate differences in sound level. Little is known about level discrimination in anuran amphibians (frogs and toads), for which vocal communication in noisy social environments is often critical for reproduction. This study used two-choice phonotaxis tests to investigate the ability of females of Cope’s gray treefrog (Hyla chrysoscelis) to discriminate between two advertisement calls differing only in sound pressure level by 2, 4, or 6 dB. Tests were conducted in the presence and absence of chorus-shaped noise (73 dB) and using two different ranges of signal levels (73–79 dB and 79–85 dB). Females discriminated between two signals differing by as little as 2–4 dB. In contrast to expectations based on the “near miss to Weber’s law” in birds and mammals, level discrimination was slightly better at the lower range of signal amplitudes, a finding consistent with earlier studies of frogs and insects. Realistic levels of background noise simulating a breeding chorus had no discernable effect on discrimination at the sound level differences tested in this study. These results have important implications for studies of auditory masking and signaling behavior in the contexts of anuran hearing and sound communication.
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43.80.Lb Sound reception by animals: anatomy, physiology, auditory capacities, processing
43.80.Nd Effects of noise on animals and associated behavior, protective mechanisms

High frequency ultrasound imaging of whole blood gelation and retraction during in vitro coagulation

Camille Plag, Yassine Mofid, Tony Matéo, Rachel Callé, and Frédéric Ossant

J. Acoust. Soc. Am. Volume 131, Issue 5, pp. 4196-4202 (2012); (7 pages)

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Blood coagulation is a series of biochemical reactions resulting in the mechanical transformation of liquid blood into a gel. As a consequence, ultrasound, being mechanical waves, can provide specific details on the dynamics of coagulation. In fact, previous high-frequency ultrasound monitoring studies have shown drastic changes in ultrasound velocity and attenuation during whole blood coagulation and a model discussing the observed mechanical transformations was proposed. In this paper, a technique of visualization of the clotting mechanism is introduced, which complements and revises the previous hypotheses. This method is based on the monitoring of scatterers (red blood cells) movement through a time correlation of 20 MHZ rf signals. It allows the computing of both a displacement map revealing local details and disparities and a parameter quantifying the global structural behavior. Qualitative results for two typical samples show that the technique provides new insights on the gelation dynamics. A quantitative analysis computed from 12 healthy subjects found that the changes in the structural parameters are significantly correlated to the changes in velocity and attenuation, both dependent on the mechanical transformations in the sample. The previous model is therefore revised and a new way to measure gel and retraction times is proposed.
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43.80.Vj Acoustical medical instrumentation and measurement techniques
43.35.Yb Ultrasonic instrumentation and measurement techniques
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