Subject: distance to hear a whale song under water

Nancy Stevick (Nancy.Stevick@btinternet.com)
Wed, 2 Jun 1999 20:36:23 +0100

On 01 June 1999 19:10, Irene Arndt wrote:


>Hi there,
>If I am diving and hear a humpback whale song, how far a distance could the
whale be from me. I hear them a lot in the Turks and Caicos.
>On behalf of my sister, Jan.


Dear Irene,

Your sister is lucky to have such an incredible experience.  Close to shore
where people usually dive, sound doesn't travel as far as it does in the
open sea.  This is due to the noise of waves, currents, absorption of the
bottom, etc.  Humpbacks also sing at fairly high frequencies, which further
limit the distance their voices carry.  I searched the primary literature
for a reliable reference for the distances humpback songs carry.  The best I
found was a 1998 paper by Best, Findlay, Sekiguchi, Peddemors, Rakotonirina,
Rossouw and Gove about humpbacks in the southwest Indian Ocean.  (I can
provide a complete citation if you are really that interested.)  These
researchers, using a an omnidirectional hydrophone, periodically detected
humpback songs at 18 of 19 stations.  "The exception was a station 17
nautical miles offshore in a water depth of 500 m.  Three hours later, an
acoustic station inshore in a water depth of 46 m revealed the presence of
many singers.  Thie straight-line distance between the 2 stations was 18
nautical miles, giving some indication of the maximum distance at which
singers might be heard."  A diver, using only her ears, would have more
limited hearing, perhaps to a distance of 5 to 10 miles.

Even though I have just answered your question, I have to share this
information with you because I find it so fascinating and astounding.  Chris
Clark, one of the world's foremost acoustic specialists, has measured
humpback songs at a distance of almost 100 miles.  He was using
state-of-the-art hydrophones.  Even with this high tech equipment, he
usually only records humpback songs from a distance of 50 miles or less.
Blue whale sounds, which are much lower frequency and therefore travel
further, can be detected at ranges of up to 1,000 miles -- if you have the
right equipment!

Thanks for asking your question.  I hope your sister hears many more
humpbacks during future dives.

Best Wishes,

Nancy Stevick