Bottle-nose dolphin acoustics

From: Peter M Scheifele (acousticp2@juno.com)
Date: Sat Dec 02 2000 - 20:29:10 EST


Can you please expand upon the dolphin's use of phonations. I know that
they are very complex
> sounds that are generated in air filled sacs connected to their
blowholes, but
> that is about it. Also, what are the differences between phonations
and
> echolocation as far as how the signal is generated and the signals use.
 

Michael

One of the primary differences between echolocation and communication
phonations is the frequency content. For Tursiops, the reange of hearing
(and acoustic range) is from about 500 Hz to 120 kHz. You can roughly
break that range up into two areas: 500 Hz to 40 kHz for communication
and 40 kHz to 120 kHz for echolocation.

Communication phonations are of varied types but in large part consist of
FM slides, whistles and buzzes. Echolocation signals are usually pulsed
signals that may be pulse modulated. The animal generally begins with a
"broadband search" and as it approaches its target, changes frequency and
pulse repetition rate (increasing) until target acquisition.

In general, sounds are produced by air eminating from the premaxillary
sac. For comunication this is cycled through nasal plugs and lips below
the blowhole whereas for echolocation the pulses are emitted via the
melon and come out in a beam pattern over the rostrum.

Communication signals are designed (as in radio) to carry information
from a sender to a receiver who uses it to determine how to respond. It
is, many times, a one-way deal. Echolocation is an "active-passive"
signal that is sent out, bounces off a target and is received back by the
sender. Changes in the outgoing in received signals are percieved and
information regarding the target is extracted from the comparison of the
signals. This is known as biosonar and autocommunication.

Let me know if this is enough information...because I could go on for a
long time about this topic, and would be most happy to if it helps.
Best
Peter

Peter M."Skip" Scheifele LCDR USN (Ret.)
Director of Bioacoustic Research, University of Connecticut NURC NA&GL
(Voice) 860-405-9103/9121; acousticp2@juno.com;
scheifel@uconnvm.uconn.edu
www.nurc.uconn.edu
http://ap.nurc.uconn.edu/cos/



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