Finneran James J.
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ArticleThe acoustic field on the forehead of echolocating Atlantic bottlenose dolphins (Tursiops truncatus)(Acoustical Society of America, 2010-09) Au, Whitlow W. L. ; Houser, Dorian S. ; Finneran, James J. ; Lee, Wu-Jung ; Talmadge, Lois A. ; Moore, Patrick W.Arrays of up to six broadband suction cup hydrophones were placed on the forehead of two bottlenose dolphins to determine the location where the beam axis emerges and to examine how signals in the acoustic near-field relate to signals in the far-field. Four different array geometries were used; a linear one with hydrophones arranged along the midline of the forehead, and two around the front of the melon at 1.4 and 4.2 cm above the rostrum insertion, and one across the melon in certain locations not measured by other configurations. The beam axis was found to be close to the midline of the melon, approximately 5.4 cm above the rostrum insert for both animals. The signal path coincided with the low-density, low-velocity core of the melon; however, the data suggest that the signals are focused mainly by the air sacs. Slight asymmetry in the signals were found with higher amplitudes on the right side of the forehead. Although the signal waveform measured on the melon appeared distorted, when they are mathematically summed in the far-field, taking into account the relative time of arrival of the signals, the resultant waveform matched that measured by the hydrophone located at 1 m.
ArticleAuditory oddball responses in Tursiops truncatus(Acoustical Society of America, 2021-08-27) Schalles, Matt D. ; Mulsow, Jason ; Houser, Dorian S. ; Finneran, James J. ; Tyack, Peter L. ; Shinn-Cunningham, BarbaraTwo previous studies suggest that bottlenose dolphins exhibit an “oddball” auditory evoked potential (AEP) to stimulus trains where one of two stimuli has a low probability of occurrence relative to another. However, they reported oddball AEPs at widely different latency ranges (50 vs 500 ms). The present work revisited this experiment in a single dolphin to report the AEPs in response to two tones each assigned probabilities of 0.2, 0.8, and 1 across sessions. The AEP was further isolated from background EEG using independent component analysis, and showed condition effects in the 40–60 ms latency range.
ArticleDoes rotation during echolocation increase the acoustic field of view? Comparative numerical models based on CT data of a live versus deceased dolphin(IOP Publishing, 2023-04-04) Wei, Chong ; Houser, Dorian ; Erbe, Christine ; Zhang, Chuang ; Matrai, Eszter ; Finneran, James J. ; Au, Whitlow W.Spinning is a natural and common dolphin behavior; however, its role in echolocation is unknown. We used computed tomography (CT) data of a live and a recently deceased bottlenose dolphin together with measurements of the acoustic properties of head tissues to perform acoustic property reconstrcution. The anatomical configuration and acoustic properties of the main forehead structures between the live and deceased dolphins were compared. Finite element analysis (FEA) was applied to simulate the generation and propagation of echolocation clicks, to compute their waveforms and spectra in both near- and far-fields, and to derive echolocation beam patterns. Model results from both the live and deceased dolphins were in good agreement with click recordings from live, echolocating individuals. FEA was also used to estimate the acoustic scene experienced by a dolphin rotating 180ã about its longitudinal axis to detect fish in the far-field at elevation angles of 0ã –20ã . The results suggest that the spinning behavior provides a wider insonification area and compensates for the dolphin’s relatively narrow biosonar beam and constraints on the pointing direction that are limited by head movement. The results also have implications for examining the accuracy of FEA in acoustic simulations using freshly deceased specimens.