I am pleased to announce the publication of the following paper in
the Journal of the Acoustical Society of America:
Koblitz, J.C., M. Wahlberg, P.
Stilz, P.T. Madsen, K. Beedholm, and H.-U. Schnitzler (2012). Asymmetry and dynamics of a narrow sonar beam in an
echolocating harborporpoise.
Journal of the Acoustical Society of America. 131 (3), 2315-2324
A key component in the operation of a biosonar system is the
radiation of sound energy from the sound producing head structures
of toothed whales and microbats. The current view involves a fixed
transmission aperture by which the beam width can only change via
changes in the frequency
of radiated clicks. To test that for a porpoise, echolocation clicks
were recorded with high angular resolution using a 16 hydrophone
array. The beam is narrower than previously reported (DI = 24 dB)
and slightly dorso-ventrally compressed (horizontal −3 dB beam
width: 13°, vertical −3 dB beam width: 11°). The narrow beam
indicates that all smaller toothed whales investigated so far have
surprisingly similar beam widths across taxa and habitats. Obtaining
high directionality may thus be at least in part an evolutionary
factor that led to high centroid frequencies in a group of smaller
toothed whales emitting narrow band high frequency clicks. Despite
the production of stereotyped narrow band high frequency clicks,
changes in the directionality by a few degrees were observed,
showing that porpoises can obtain changes in sound radiation.
Please feel free to contact me for a pdf copy.
With kind regards,
Jens Koblitz
Jens.Koblitz@uni-tuebingen.de
Biosonar Lab
Animal Physiology
Insitue for Neurobiology
University of Tuebingen
Auf der Morgenstelle 28
D-72076 Tuebingen
Germany