@article {53272, title = {Directional hearing sensitivity for 2{\textendash}30 kHz sounds in the bottlenose dolphin (Tursiops truncatus)}, journal = {The Journal of the Acoustical Society of America}, volume = {144}, year = {2018}, month = {Jan-09-2018}, pages = {1741 - 1741}, abstract = {

Bottlenose dolphins (Tursiops truncatus) depend on sounds with frequencies \<30 kHz for social communication and foraging, but little information on the directional dependence of hearing thresholds for these sounds exists. This study measured behavioral hearing thresholds for 2, 10, 20, and 30-kHz tones projected from eight different angular positions around the dolphin in both the horizontal and vertical planes to determine whether the receiving beam at these frequencies was directional. Omni-directional hearing was hypothesized for sounds below 30 kHz, but this hypothesis was rejected. Results from two bottlenose dolphins demonstrated a positive relationship between directivity and the frequency of the test tone, with asymmetric beam patterns. Directional hearing sensitivity declined most dramatically between 10 kHz and 2 kHz. The results suggest that dolphins\’ directional hearing is more pronounced for lower frequencies than previously predicted.

}, issn = {0001-4966}, doi = {10.1121/1.5067720}, url = {http://asa.scitation.org/doi/10.1121/1.5067720}, author = {Accomando, Alyssa W. and Mulsow, Jason and Branstetter, Brian K. and Finneran, James J. and Jenkins, Keith} } @article {53271, title = {Acute motor and vocal response of humpback whales ( Megaptera novaeangliae ) to playback of amplitude-modulated noise: A method to test frequency range of hearing}, journal = {The Journal of the Acoustical Society of America}, volume = {144}, year = {2018}, month = {Jan-09-2018}, pages = {1953 - 1953}, abstract = {

The frequency hearing range of mysticete cetaceans remains elusive despite a growing concern about the negative impacts of anthropogenic noise. A playback study was conducted in the Maui Nui region of Hawaii during March 2018. Stationary humpback whales (i.e., single singers or silent dyads) were targeted due to their predictable behavior that allowed for observations pre, during, and post-playback. Playback consisted of amplitude-modulated noise that was broadband, high-pass filtered, or 1/3 octave bandpass filtered. The animal\’s motor behavior was recorded by video from a swimmer positioned above the animal. Acoustic playback and acquisition was performed from a small vessel approximately 41 m to 56 m from a targeted animal. A total of 16 playbacks were conducted with estimated received levels between 116 dB\–138 dB RMS (re 1 \μPa). Motor responses ranged from abruptly swimming away to subtle fluke movements with a median response latency of 1.7 sec (n = 7). Vocal responses ranged from abrupt song termination to unexpected changes in song unit pattern, with a median response latency of 2.94 sec (n = 8). This novel playback methodology was effective at producing and measuring motor and vocal responses to sound and may be useful in measuring the hearing range of mysticetes.

}, issn = {0001-4966}, doi = {10.1121/1.5068540}, url = {http://asa.scitation.org/doi/10.1121/1.5068540}, author = {Branstetter, Brian K. and Deakos, Mark H. H. and Jenkins, Keith and Balmer, Brian C. and Ness, Alan P. and Cartwright, Rachel} }