Page 52 - Spring 2019
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i-iepeuna and Biuaonar ,,,p,,,,_
in o  o o 0 '7'"""""“" -- II
1  I ‘ s
1. . . . . . ',_/_“___m ‘  I,
i  /‘H '— " ’ ' .'-—' -.
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Figure 7. The 24—element hydrophone array used to measure the  J _ ‘
aeam pattern af the azaiphin during target detection trials. Lefi .
graphic shows a planar display of the array urc shawn at right. Red '
star in the center denotes the P0 hydmphone, which is aligned with . J
the main axis afthe dulphin to the target when the target was placed 7 ~
'1"’"”)’ ""f"’"‘ "W19 '’’'’’P’“''' '1’ P0 F"’'" MW” 9"“ (20931 Figure 3. Mean amplitude azistriiiatian at Various points on Hep—
  tuna’: head. The eulurs indicate diflirent intensities (with red being
This was a behavior that led to an experiment to identify if the loudest). The numbers are the actual measurements determined
the dolphin could detect targets off the main beam axis and at dxfierent suction—cup hydmphime loeutians relative to the loudest
to quantify their capabilities. To that end, Heptuna was used sound an the head. Dashed line, area af maximum intensity on Hep—
to explore emitted-beam control. Investigators (Lois Dankie- tuna’: melon. From Au et al. (2010).
wicz, Dorian Houser, and Moore) devised an experiment to  
haw H3P‘“m‘ 01155 “gal-1" 5mti°“ °“ 3 him P13“ and delect forward-projected but movable beam with complex energy
eCh°35 from “'85” Placed 3‘ V‘“'i°“5 P°5m°“5 ‘° his fight distributions over which the animal had some control.
and left. This time, he would be echolocating through a ma-
trix of hydrophones so that the investigators could examine Heptuna and Contact
various parameters of each emitted click at each position in Hydrophonas
the matrix of hydrophones and determine the beam pattern Whit Au, pursuing his interest in dolphin echolocation
for each click in his emitted click train (Figure 7). clicks, traveled to San Diego to participate in our ongoing ex-
. ' . First he wanted to determine the location where
Heptuna was asked to detect a water-filled stainless steel penmems _ ‘ _ _
sphere and a hollow aluminum cylinder. Heptuna stationed dlzecholocaflolfi hem?‘ 3:-1ls_em:rges fro?“ the iflfiihlnl head
on a bite plate that prevented his ability to move his head  ((1) e_xaI:mfe  “fit eécousuc gel“ :3 re am to
during echolocation. He was then asked to echolocate tar- s_lgna  mt 2 ar 2 ' ‘mt’ mvemgaml_'s( nan ranslettef’
. . . lim Finneran, and Moore) helped Whit as he placed vari-
gets as theywere placed at various angles to his left and right h d h d ‘h h d f H d
(Moore et al., 2008). Horizontal and vertical -3 dB beam ous Y mp °_m “Hays afoun 6 ea_ 5 0 spun“  a
. . . second dolphin, Bugs (Figure 8). Whit collected the clicks
widths were calculated for each click as well as correlations _ _
. . . _ from the arrays and computed the position on the melon (a
between click characteristics of peak frequency, center fre _ th f h d f all t th d h 31 th ‘ t 1
. massin eore ea o oo e w es aacsasa ens
quency, peak level, and root-mean-square (rms) bandwidth. _ _ _ _ _
Differences in the angular detection thresholds for both the t(;_C}(:11Lr_na‘: emmed fi1‘:Ikv‘;)]_Where;}::1m nude
sphere and the cylinder to the left and right were relatively 0 _‘ 6 Sign  Occur“ ' it Hole at _eaC 0 P ms a_m_
equal, and Heptuna could detect the sphere when it was 21° plmsde _g:fl‘_:_‘t abo“t_"h: ‘Sign fins duiifntf‘ slilggitmi
to the right and 25° to the left. His detection threshold for the am Om” 1 erencés Ln 0 E S ape (? it ore 63 an
cylinder was not as good, being only 13° to the right and 19° dim the “fund Yelomy Profile of _the mu-n_a1s m_e1on “sad
to the left. The more interesting result became apparent when on "h_e emmefi signal‘ Hepmm typically emmed Sign 315 with
. . . . . amplitudes higher than those of Bugs by 11-15 dB (Au and
plotting his composite horizontal and vertical beam patterns. P 1981
Both were broader than previously measured (Au et al., 1978, enner’ )'
1985b) and varied during target detection. The center part Whit also interpreted his results as demonstrating that the
of the beam was also shifted to the right and left when Hep- animal’s emitted click was first shaped internally by the air
tuna was asked to detect targets to the right and left. It was sacs in its head and then refined by transmission through
clear that Heptuna’s echolocation clicks formed a dynamic the melon. Whit suggested that his results supported Norris’s
an 1 AI:|'.iuI:l:I Tbday 1 Spring 2019

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