Smith Adam B.

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Smith
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Adam B.
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  • Article
    Transmission beam pattern and dynamics of a spinner dolphin (Stenella longirostris)
    (Acoustical Society of America, 2019-06-19) Smith, Adam B. ; Pacini, Aude F. ; Nachtigall, Paul E. ; Laule, Gail E. ; Aragones, Lemnuel V. ; Magno, Carlo ; Suarez, Leo J. A.
    Toothed whales possess a sophisticated biosonar system by which ultrasonic clicks are projected in a highly directional transmission beam. Beam directivity is an important biosonar characteristic that reduces acoustic clutter and increases the acoustic detection range. This study measured click characteristics and the transmission beam pattern from a small odontocete, the spinner dolphin (Stenella longirostis). A formerly stranded individual was rehabilitated and trained to station underwater in front of a 16-element hydrophone array. On-axis clicks showed a mean duration of 20.1 μs, with mean peak and centroid frequencies of 58 and 64 kHz [standard deviation (s.d.) ±30 and ±12 kHz], respectively. Clicks were projected in an oval, vertically compressed beam, with mean vertical and horizontal beamwidths of 14.5° (s.d. ± 3.9) and 16.3° (s.d. ± 4.6), respectively. Directivity indices ranged from 14.9 to 27.4 dB, with a mean of 21.7 dB, although this likely represents a broader beam than what is normally produced by wild individuals. A click subset with characteristics more similar to those described for wild individuals exhibited a mean directivity index of 23.3 dB. Although one of the broadest transmission beams described for a dolphin, it is similar to other small bodied odontocetes.
  • Preprint
    Investigation on acoustic reception pathways in finless porpoise (Neophocaena asiaorientalis sunameri) with insight into an alternative pathway
    ( 2018-10) Song, Zhongchang ; Zhang, Yu ; Mooney, T. Aran ; Wang, Xianyan ; Smith, Adam B. ; Xu, Xiaohui
    Sound transmission and reception are both vital components to odontocete echolocation and daily life. Here, we combine computed tomography (CT) scanning and Finite Element Modeling to investigate the acoustic propagation of finless porpoise (Neophocaena asiaorientalis sunameri) echolocation pulses. The CT scanning and FEM wave propagation model results support the well-accepted jaw-hearing pathway hypothesis and suggest an additional alternative auditory pathway composed of structures, mandible (lower jaw) and internal mandibular fat, with different acoustic impedances, which may also conduct sounds to the ear complexes. The internal mandibular fat is attached to the ear complex and encased by the mandibles laterally and anteriorly. The simulations show signals in this pathway initially propagate along the solid mandibles and are transmitted to the acoustically coupled soft tissue of the internal mandibular fat which conducts the stimuli posteriorly as it eventually arrives at ear complexes. While supporting traditional theories, this new bone-tissue-conduction pathway might be meaningful to understand the hearing and sound reception processes in a wide variety of odontocetes species.
  • Article
    A field study of auditory sensitivity of the Atlantic puffin, Fratercula Arctica
    (The Company of Biologists, 2020-06-19) Mooney, T. Aran ; Smith, Adam B. ; Larsen, Ole Naesbye ; Hansen, Kirstin Anderson ; Rasmussen, Marianne H.
    Hearing is vital for birds as they rely on acoustic communication with parents, mates, chicks, and conspecifics. Amphibious seabirds face many ecological pressures, having to sense cues in air and underwater. Natural noise conditions have helped shape this sensory modality but anthropogenic noise is increasingly impacting seabirds. Surprisingly little is known about their hearing, despite their imperiled status. Understanding sound sensitivity is vital when we seek to manage manmade noise impacts. We measured the auditory sensitivity of nine wild Atlantic puffins, Fratercula arctica, in a capture-and-release setting in an effort to define their audiogram and compare these data to the hearing of other birds and natural rookery noise. Auditory sensitivity was tested using auditory evoked potential (AEP) methods. Responses were detected from 0.5 to 6 kHz. Mean thresholds were below 40 dB re 20 µPa from 0.75 to 3 kHz indicating that these were the most sensitive auditory frequencies, similar to other seabirds. Thresholds in the ‘middle’ frequency range 1-2.5 kHz were often down to 10-20 dB re 20 µPa. Lowest thresholds were typically at 2.5 kHz. These are the first in-air auditory sensitivity data from multiple wild-caught individuals of a deep-diving Alcid seabird. The audiogram was comparable to other birds of similar size, thereby indicating that puffins have fully functioning aerial hearing despite the constraints of their deep-diving, amphibious lifestyles. There was some variation in thresholds, yet animals generally had sensitive ears suggesting aerial hearing is an important sensory modality for this taxon.