How how blue whales hear?

From: Catherine Schaeff (schaeff@american.edu)
Date: Tue Feb 22 2005 - 18:43:45 EST

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    Hi,
     
    Great project. We are still learning about how whales hear but there is some info available.  The first thing that you'll want to do when you have a question is to search the whalenet site to see if the answer is already there (http://whale.wheelock.edu/Search.html). In this case, it is. I've pasted one of the relevant responses below -- there are a number of them on the whalenet site that you might find helpful.
     
     

    Whale Hearing

    From: Peter M Scheifele (acousticp2@juno.com)
    Date: Wed Mar 08 2000 - 01:20:50 EST


    Dear Claire & Mom

    This is a good question and one that is my specialty as a marine
    bioacoustician, namely whale hearing. There are only a handful of us who
    do research into whale hearing and the literature is as scarce on the
    subject as our number is scarce. The subject of whale hearing is complex
    but here are some generalities to get you both started and then you can
    follow with more specific questions on the subject and I'll e happy to
    walk you through it.

    Whales, as you know, are split into 2 groups; baleen whales and toothed
    whales. The toothed whales also include dolphins and porpoises whp are
    really just small whales. All whales have ears but unlike humans and
    most terrestrial mammals they have no outer ear part (called the pinna).
    Instead, they have an outer ear canal as we do.

    The outer ear canal leads to a tympanic membrane (ear drum) which
    vibrates and in turn, causes 3 small bones in the middle ear to move.
    The 3 bones are: MALLEUS, which attaches to the tympanic membrane; INCUS
    which attaches to the malleus and transfers sound vibrations to the
    STAPES, which is connected to the inner ear inside the skull. STAPES is
    connected to the inner ear, a fluid-filled sac.

    When a sound is made and stapes is moved (it rocks back and forth) it
    causes a fluid wave to travel in the sac of the inner ear. This fluid
    wave travels down the sac and where the wave is peaked it excites hair
    cells. The hair cells (which are attached to the basilar membreane) are
    arranged in order of frequency from high to low similar to the keysand
    corresponding notes on a piano. This is how the whale (and ANY mammal,
    incluing we humans) can tell differences in pitch.

    How much the hair cell is excited (and bent over) gives us (and whales
    too) the sensation of loudness. If you go to a very loud concert your
    hair cells will be sufficientlly bent over such that it will take some
    time after the concert before your hearing is restored to its former
    state. This is not good but people do it all of the time and whales are
    subject to the noise of the ocean PLUS whatever we put into the ocean!
    In other words, they are subject to occupational hearing loss just as we
    are!

    Now for some differences between the "typical mammalian ear and the
    (whale) aquatic ear. The toothed whales, we know have no use for their
    outer ears. They hear via their lower jaw which contains an acoustic fat
    that transmits the sound to the middle ear. Their middle ear is filled
    with fluid and foam unlike other mammals whose middle ear is air-filled.

    Most mammals on earth have inner ears that are physically a part of their
    skull (including humans). Its all one set of bones! Whales inner and
    middle ears are NOT part of the skull bones but are held in place by a
    series of ligaments NOT a part of the skull.

    Baleen whales also have no use of the outer ears. In fact, their outer
    ear is plugged shut with a wax plug! We don't know much about baleen
    whale ears since we have a hard time studying them in the ocean and we
    cannot keep them in captivity.

    Why all of these changes, you may ask? Well aerial ears don't perform
    well in water but the aquatic ear has apparently been designed or has
    evolved to function as well in water as our ears do in air. Remember,
    sound travels 5 times faster in water than in air! So, for instance, if
    the whale ear were to be a part of the skull they would hear the noise of
    the water on their heads as they swim (the rain on your face is harder
    than on the back of your head when you're running, eh?).

    I hope this helps you both and it has been my pleasure to answer your
    question.
    Peter

    On Tue, 7 Mar 2000 19:16:06 -0700 "lpgriffin"
    <pgriffin19@excelonline.com> writes:
    > Peter, my daughter ,Claire, and I have been looking for information
    > about how whales hear. Do they have ears? claire is seven years old
    > and loves whales and other marine mammals!
    > Thank you Claire Griffin

    Peter M. Scheifele
    129 Hunters Road, Norwich, CT 06360
    860-405-9103; acousticp2@juno.com
    www.nurc.uconn.edu

     
     
    If you want some more indepth (but more difficult to understand info) National Geographic has a nice article on the evolution of whle hearing ( http://news.nationalgeographic.com/news/2004/08/0811_040811_whale_evolution.html) You'll need to have an adult help you understand it.
    Cathy Schaeff
    Associate Professor and Chair
    Department of Biology
    American University
    101 Hurst Hall, 4400 Mass. Ave. NW,
    Washington DC 20016-8007
    p: 202.885.2194, f: 202.885.2182
    schaeff@american.edu

    -----Sharon <slazeo@northwestel.net> wrote: -----

    To: schaeff@american.edu, pita@whale.wheelock.edu
    From: Sharon <slazeo@northwestel.net>
    Date: 02/21/2005 10:43PM
    Subject: How ho blue whales hear?

    I am researching blue whales hearing systems for my grade 3 project.  Do you have any information on how blue whales hear?  Nicola  Lazeo-Fairman  My moms email address is slazeo@northwestel.net




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