Subject: Sonar and whales

S. Jones (
Sat, 21 Nov 1998 22:11:20 -0800 (PST)

On Fri, 20 Nov 1998, Sue Shirley wrote:

> Bete, 
> The following questions are from my 5th grade science students about
> whales.  Thank you in advance for answering them. 
> From Micah, Adam, and Chris: What happens when a whale and a boat send
> a sonar signal at the same time?

Whales and ships sometimes send signals that are at the same decibel and
frequency level.  A ship's signal has the potential to cover up the signal
sent by the whale.  If the ship signal does not last for very long, the
whale is less affected.  If it lasts longer, it could interfere with
communication between individual whales. Scientists believe a whale is
able to tell the difference between a man-made signal and a signal sent by
another whale, just as we are able to recognize the human voice among a
variety of other noises. Using tracking devices, ships are also able to
tell the difference between man-made and whale sounds underwater.

> From Kayla and Ashley: What are some of the ways in which people use
> sonar?  When was it invented and who invented it?

Sonar is used in the ocean in a variety of different ways.  Ships use
sonar to find out how deep the water is in the area they are travelling.
Other sonars are used to find fish, measure currents, survey plankton, and
the ocean floor.  Military sonars can detect objects underwater.  The oil
and gas industry use sonar to find oil reserves on the bottom of the

> From Jay and Stephen: What is your favorite species of whale to study?
Out of the species I have studied the most, I enjoy working with humpback
whales.  I would like to do more work with blue, fin, and sperm whales.

> From Sarah and Kristie: How do whales use their melons during
> echolocation

Only odontocetes (toothed whales) use their melons for echolocation.  The
high-frequency sounds emitted by these animals bounce off objects and
return to the ears of the echolocating animal.  the appropriate centers of
the brain analyze these sounds and an acoustic image of the animal's
surroundings is made.  This way, the animal can know if it swimming
towards an object like a coral reef, or towards a school of fish.

> Thank you, 
> Sue Shirley
> Dedham Country Day School, Dedham, MA