Dorian S. Houser

Acoustical Society of America

R. Bruce Lindsay Award

2007

Dorian S. Houser

Dorian Scott Houser completed his B.A.in Biology (Summa Cum Laude) at Coker College in June1992 and his PhD at the University of California, SantaCruz (UCSC) in 1998. During his graduate tenure at UCSCDorian received a fellowship from the American Society for EngineeringEducation that allowed him to work during summers at hischoice of naval research laboratories. Dorian chose to work atthe Navy Marine Mammal Program at the Space and NavalWarfare Systems Center, San Diego (SSC-SD), where he hoped topursue his interest in marine mammal diving physiology. He soughtout Sam Ridgway, an internationally known and respected expert inmarine mammal physiology, to see if there was an opportunityto work during his first summer under the fellowship studyingdiving pinnipeds. Unfortunately, Sam had no ongoing diving physiology tasksso he pointed Dorian to the Biosonar Program that hadjust begun a few years before at the laboratory.

In thatfirst summer Dorian began looking at the emitted echolocation signalsof several dolphins. A paper had just been published thatsegregated false killer whale echolocation clicks into three categories andDorian was determined to see if the application of thisscheme to dolphin echolocation could be used to look forsystematic variations in echolocation click production. Dorian attacked this projectwith enormous energy (an approach he continues to apply tohis projects) and began an exhaustive study into the basicsof dolphin bioacoustics and signal processing. His efforts were rewardedby his first publication in the Journal of the AcousticalSociety of America (JASA) in 1999.

After obtaining his Ph.D., Dorianwas awarded a National Research Council Postdoctoral Research Fellowship tocontinue bioacoustics research at SSC-SD and since then, Dr. Houser'scontributions to the Society and to animal bioacoustics have beensteady with approximately one quarter of his published works appearingin the Journal. His research has moved to the leadingedge of our understanding of the effects of sound onmarine mammals. Dorian developed a basis for modeling hearing inwhales by using multi-threaded, evolutionary computational methods to model thehearing system of the dolphin. From that point, he ground-truthedthe model's goodness-of-fit to the dolphin and applied it tothe humpback whale, a species for which only anatomical dataexisted. For his work Dorian was acknowledged as “key personnel”in the Strategic Environmental Research and Development Program (SERDP) “Projectof the Year” in 2000.

After completing his postdoctoral fellowship, Dorianformed his own company, Biomimetica, and has continued to bean integral part of the Navy's exploration into new areasof psychoacoustic measures of the hearing of marine mammals. Dorian,along with Sam Ridgway, applied medical imaging techniques to explorethe physiology and anatomy of the dolphin signal generating andreceiving systems. These studies marked the first time structural (MRI,CT) and functional brain scans (PET, SPECT) were performed ona living cetacean. The results had far-reaching implications, ranging fromhighlighting differences between post mortem and in vivo anatomy, describingin vivo the complex nasal sacs around the ears andtheir relationship to directional hearing, to hypothesizing on the possibilityof thermoregulation of acoustic lipids in the dolphin's melon andits implications for sound transmission.

Dorian also helped develop and implementthe “Biosonar Measurement Tool,” a device that captured the completeacoustic environment (signal emissions and echo reception) of a free-swimmingdolphin in open-water target detection tasks. It also recorded thethree-dimensional motion of the animal through the water enabling avirtual recreation of the animal's search and bioacoustic behavior. Theresults, published in JASA, showed how echolocating dolphins employed theirbiosonar during open-ocean target detection and provided insight for biologicallyinspired search and detection algorithms used in newly developed biomimeticsonar.

Dorian also applied his expertise in physiology to advance electrophysiologicalmethods for hearing assessment. He is co-investigator on an effortto develop and standardize the measurement of auditory evoked potentialsfrom marine mammals. These techniques have led to the firstlarge scale, controlled study of marine mammal audition, with hearingtests to date being conducted on more than 42 dolphins.The results of this study revealed important relationships between animals'hearing abilities and age, gender, ancestry, and medical history andhave provided key inventory management data for the Navy MarineMammal Program.

Dorian is active in investigating potential physiological causes ofmarine mammal strandings. His 2001 paper in the Journal ofTheoretical Biology has served as a catalyst for hypotheses explainingbeaked whale strandings involving acoustically driven or activated bubble growth.Dorian is currently investigating the potential for this phenomenon byattempting to ultrasonically measure intravascular nitrogen bubbles that may formin a diving animal just after it surfaces from aseries of dives. The results of this project should providesome basic answers to questions regarding nitrogen accumulation and bubblegrowth in diving marine mammals and lay the groundwork forunderstanding the potential impact of sonar on beaked whales.

In additionto possessing excellent research and experimental skills, Dr. Houser alsohas the important ability to maintain focus on the largercontext of the research, apply the results to real-world problems,and publish work in publicly accessible, peer-reviewed literature. He hasbeen a key participant in the development of several NavyEnvironmental Impact Statements assessing the potential effects of acoustic activitieson marine mammals. In these technically challenging and often emotionallycharged efforts, Dorian has shown tremendous skill in explaining toa lay audience complex acoustic topics ranging from acoustic metricsto the process of rectified diffusion, all while maintaining apositive and professional relationship with Navy environmental planners, government regulators,and non-governmental environmental groups.

In summary, Dr. Houser's work in marinemammal bioacoustics has made a significant impact on the stateof knowledge regarding marine mammal audition and the physiological effectsof sound on diving marine mammals. Dorian is active inthe Society as a presenter and member of the AnimalBioacoustics Technical Committee. We believe he is an outstanding researcherwith unparalleled ability and is a worthy recipient of thisR. Bruce Lindsay Award.

PATRICK W. MOORE

JAMES J. FINNERAN