| Summary: | Across species, bats exhibit wildly disparate differences in their
noseleaf and pinnae shapes. Within Rhinolophid and Hipposiderid
families, bats actively deform their pinnae and noseleaf during
biosonar operation. Both the pinnae and noseleaf act as acoustic
baffles which interact with the outgoing and incoming sound; thus,
they form an important interface between the bat and its
environment. Beampatterns describe this interface as joint
time-frequency transfer functions which vary across spatial direction.
This dissertation considers bat biosonar shape diversity and shape
dynamics manifest as beampatterns. In the first part, the seemingly
disparate set of functional properties resulting from diverse pinnae
and noseleaf shape adaptations are considered. The question posed in
this part is as follows: (i) what are the common properties between
species beampatterns? and (ii) how are beampatterns aligned to a
common direction for meaningful analysis? Hence, a quantitative
interspecific analysis of the beampattern biodiversity was taken
wherein: (i) unit[267]{} different pinnae and noseleaf beampatterns
were rotationally aligned to a common direction and (ii) decomposed
using principal component analysis, PCA. The first three principal
components termed eigenbeams affect beamwidth around the single lobe,
symmetric mean beampattern.
Dynamic shape adaptations to the pinnae and noseleaf of the greater
horseshoe bat (textit{Rhinolophus ferrumequinum}) are also
considered. However, the underlying dynamic sensing principles in use
are not clear. Hence, this work developed a biomimetic substrate to
explore the emission and reception dynamics of the horseshoe bat as a
sonar device. The question posed in this part was as follows: how do
local features on the noseleaf and pinnae interact individually and
when combined together to generate peak dynamic change to the incoming
sonar information? Flexible noseleaf and pinnae baffles with different
combinations of local shape features were developed. These baffles
were then mounted to platforms to biomimetically actuate the noseleaf
and pinnae during pulse emission and reception. Motions of the baffle
surfaces were synchronized to the incoming and outgoing sonar
waveform, and the time-frequency properties of the emission and
reception baffles were characterized across spatial
direction. Different feature combinations of the noseleaf and pinnae
local shape features were ranked for overall dynamic effect. === Ph. D.
|
|---|
