FRIDAY MORNING, 20 MAY 2005 REGENCY E, 8:30 A.M. TO 12:00 ...

separability or quasi-separability of this matrix could make it easy for
modal back-scattering matrix inversion. In this paper, the modal backscattering
matrix due to the roughness of the bottom interface in shallowwater
was obtained and its separability error was analyzed. Numerical
simulation shows that the separability error increases with modal grazing
angle and density ratio of the sediment to the water, while decreases with
sound speed ratio of the sediment to the water. It also shows that the effect
of the separability error on shallow water reverberation level prediction is
negligible. Work supported by the National Science Foundation of China
under Grant No 10474111.
FRIDAY AFTERNOON, 20 MAY 2005
PLAZA C, 1:00 TO 2:50 P.M.
Session 5pAB
Animal Bioacoustics and ASA Committee on Standards: Behavioral Audiometric Methods in Animal
Bioacoustics: The Search for Standards II
Edward J. Walsh, Cochair
Boys Town National Research Hospital, 555 N. 30th St., Omaha NE 68131
Ann E. Bowles, Cochair
Hubbs-Sea World Research Inst., 2595 Ingraham St., San Diego, CA 92109
Chair’s Introduction—1:00
Contributed Papers
1:05
5pAB1. Dependence of detection threshold estimates in rabbit on
method of constant stimulus parameters. Laurel H. Carney, Yan Gai
Inst. for Sensory Res., Dept. of Biomed. and Chemical Eng., Syracuse
Univ., Syracuse, NY 13244, Kristina S. Abrams Syracuse Univ.,
Syracuse, NY 13244, Fabio Idrobo Boston Univ., Boston, MA 02215,
and John Michael Harrison Boston Univ., Boston, MA 02215
The goal of this study was to estimate behavioral detection thresholds
in quiet and noise for subsequent physiological studies of responses to
near-threshold stimuli. The difficulty in measuring detection thresholds is
maintaining stimulus control of behavior over schedule control. Tracking
paradigms are efficient, but the large proportion of trials below threshold
weakens stimulus control. The Method of Constant Stimuli controls the
proportion of trials below, near, and above the SPL for a given percent
correct. Here, percentages of trials at different SPLs and zero intensity
catch trials were varied to determine proportions that yielded satisfactory
stimulus control by a 500-Hz tone in quiet. Trials were initiated by nosepoke
observing responses; a nose-poke reporting response within a 3-s
window after tone onset resulted in food reinforcement. Reporting responses
in the absence of tones resulted in timeouts. A metric for stimulus
control was the ratio of the number of correct detections to the number of
responses in the absence of the tone. This ratio was highest when approximately
20% of trials were near the 50%-correct SPL and 80% of trials
were 20 dB higher. The ratio was lowest when significant proportions of
catch and/or below-threshold trials were included. Work supported by
NIDCD DC-001641.
1:20
5pAB2. Manatees masked thresholds for complex sounds. Edmund
Gerstein, Laura Gerstein, Joseph Blue Leviathan Legacy Inc., 1318 SW
14th St., Boca Raton, FL 33486, and Steve Forsythe Naval Undersea
Warfare Ctr., Newport, RI
Acoustical masked thresholds of complex real world sounds were
measured with West Indian manatees. Motor boat and species-specific
calls were recorded, filtered and played back in a forced-choice twoalternative
test. A method of constant stimuli was used to estimate the 50%
detection thresholds of peak spectral components. Both white noise and
recorded wild ambient spectra were used as continuous background noise
for two sets of threshold estimates. Manatee calls were detected at and
within both white noise and wild ambient levels. Thresholds for broadband
boat noise ranged from 9 to 29 dB above ambient conditions. Thresholds
for idling boat noise were the highest. The levels were consistent with the
subjects’ auditory limits for the lower frequencies with the spectra. The
manatee is well adapted to hear the species specific vocalizations under
noisy conditions. The integration of multiple critical bands may result in
loudness summation benefits which manatees can exploit at higher frequencies,
however, at lower frequencies, near the manatees’ limits of sensitivity,
benefits of loudness summation were not apparent.
1:35
5pAB3. Testing marine mammal hearing with a vocal response
paradigm and the method of free response. James J. Finneran, Donald
A. Carder U.S. Navy Marine Mammal Program, SPAWARSYSCEN San
Diego, Code 2351, 53560 Hull St., San Diego, CA 92152,
james.finneran@navy.mil, Carolyn E. Schlundt EDO Professional
Services, San Diego, CA 92110, and Sam H. Ridgway Univ. of
California, La Jolla, CA 92093-0612
Behavioral hearing tests with marine mammals often use single interval
experiments with a go/no-go paradigm, where the subject pushes a
response paddle or similar device to indicate the presence of a hearing test
tone. This approach is widely accepted, but the time required for the
subject to physically move and/or interact with the response device and
the requirement of one trial per reinforcement interval limit the speed at
which data can be collected typically 20–30 minutes for a threshold.An
alternative to the single interval/paddle press approach is the use of a vocal
response technique and the method of free response, where multiple trials
are presented within a single reinforcement interval. An acoustic or vocal
response eliminates the need for the subjects to physically move, allowing
for faster responses and shorter inter-trial intervals. The method of free
response allows multiple tone presentations between reinforcement periods,
dramatically increasing the rate at which data may be collected, especially
from diving marine mammals. This talk describes the application
of these techniques to hearing tests of bottlenose dolphins, white whales,
and California sea lions and the advantages and disadvantages compared
to the single interval experiment. Work supported by ONR.
2613 J. Acoust. Soc. Am., Vol. 117, No. 4, Pt. 2, April 2005 149th Meeting: Acoustical Society of America 2613
5p FRI. PM