title: Equal latency contours for bottlenose dolphins (Tursiops truncatus) and California sea lions (Zalophus californianus).
abstract: Loudness perception by non-human animals is difficult to study directly. Previous research efforts have instead focused on estimating loudness perception using simple reaction time (RT) data. These data are used to generate equal latency contours that serve as a proxy for equal loudness contours. To aid the design of auditory weighting functions for marine mammals, equal latency contours were generated using RT data for two marine mammal species that are representative of broader functional hearing groups: the bottlenose dolphin (under water) and California sea lion (in air). In all cases, median RT decreased with increasing tone sound pressure level (SPL). The equal latency contours corresponding to near-threshold SPLs were similar to audiograms for both species. The sea lion contours showed some compression at frequencies below 1 kHz; however, a similar pattern was not apparent in the more variable data for dolphins. Equal latency contours for SPLs greater than approximately 40 dB above threshold diverged from predicted equal loudness contours, likely due to the asymptotic nature of RT at the highest tested SPLs. The results suggest that auditory threshold data, potentially augmented with compression at low frequencies, may provide a useful way forward when designing auditory weighting functions for marine mammals.
authors.affiliation: National Marine Mammal Foundation, 2240 Shelter Island Drive, #200, San Diego, California 92106, USA.
authors.forename: Jason
authors.initials: J
authors.lastname: Mulsow
authors.affiliation: Exelis, Inc., 3276 Rosecrans Street, San Diego, California 92110, USA.
authors.forename: Carolyn E
authors.initials: CE
authors.lastname: Schlundt
authors.affiliation: Department of Biological Sciences, California State University, Long Beach, 1250 Bellflower Boulevard, Long Beach, California 90840, USA.
authors.forename: Lacey
authors.initials: L
authors.lastname: Brandt
authors.affiliation: U.S. Navy Marine Mammal Program, Space and Naval Warfare Systems Center Pacific, Code 71510, 53560 Hull Street, San Diego, California 92152, USA.
authors.forename: James J
authors.initials: JJ
authors.lastname: Finneran
mesh_terms: D000161:Acoustic Stimulation; D000388:Air; D000818:Animals; D001301:Audiometry, Pure-Tone; D001309:Auditory Threshold; D050681:Bottle-Nosed Dolphin / Q000502:physiology*; D003216:Conditioning, Operant; D008144:Loudness Perception / Q000502:physiology*; D008297:Male; D011930:Reaction Time; D046070:Sea Lions / Q000502:physiology*; D013016:Sound; D013045:Species Specificity; D014867:Water
chemical_list: D014867:Water