Fun_People Archive
7 Apr
Re: Whale testing

Date: Thu,  7 Apr 94 17:50:22 PDT
To: Fun_People
Subject: Re: Whale testing

[Here are some replies to the "PseudoScience Marches On" posting.  -psl]

Forwarded-by: bostic@vangogh.CS.Berkeley.EDU (Keith Bostic)
Forwarded-by: (Rick Sayre)

The LA Times published a letter today from the Scripps Institute,
refuting the "Sky Is Falling" claims of those who misunderstood
the study.  Sounds like another case of typical journalism...  A
friend typed it in:

Forwarded-by: (Keith Goldfarb)


        The Times published articles (March 22-26) on a Scripps
    experiment to develop an acoustic monitoring system for
    determining the realities of global warming possibly associated
    with a clear buildup of greenhouse gasses.

        The first article presaged a public hearing on the project
    that day in Washington.  Unfortunately, there were many incorrect
    statements which subsequently led directly to a firestorm of
    protest in the national press.  The article stated that the
    source was so loud that it could deafen wales; this is incorrect.
    The source power is 200 watts, and this level would only be
    encountered if the whale's ear was right up against the source,
    which is 3,000 feet beneath the sea surface.  Permanent damage
    occurs at about 60,000 watts.  Near the surface the power is down
    by a factor of a million, comparable to loud speech.  Only if a
    diver were to descend into the water directly above the source
    would the tone be apparent; because the transmission of sound
    from water to the atmosphere is so inefficient, someone in a boat
    wouldn't be able to hear the source.

        As sound propagates away from the source, the intensities
    continue to decrease and reach the ocean's ambient noise level at
    a distance near 150 miles; the sound cannot be "heard" in New
    Zealand as reported in The Times.  Why bother to transmit if the
    sound cannot be heard?  A 200-watt light bulb on the surface of
    the moon could not be seen by humans on the Earth at night
    either.  However, the light bulb could be observed by Southern
    California's telescope at Palomar.  The same is true of the
    acoustic signal.  Acoustic arrays search for the narrow band
    signal and computers are further exploited to extract the coded
    signal.  These sophisticated approaches were taken specifically
    to avoid the transmission of loud acoustic signals which might
    harm marine mammals.

        Your articles state that 677,000 whales, dolphins and seals
    in the Pacific will be affected by this experiment.  In fact, the
    National Marine Fisheries Service has a policy of listing the
    entire Pacific population.  It is highly unlikely that all these
    marine mammals will swim by the sources.  Even if they do, they
    will not be harmed; perhaps distracted if too close, but certainly
    not harmed.

        That The Times would think that we would act with callous
    disregard for the environment and the living creatures in the sea
    is extraordinary.  Your sensational reporting was picked up
    around the country and the fallout has done great damage.

        JOHN A. ORCUTT, Director
        Institute of Geophysics and Planetary Physics
        Scripps Institution of Oceanography, La Jolla


Forwarded-by: Cal Herrmann <arminius@nature.Berkeley.EDU>

In article <2n7bv2$> you write:
>>A team at Scripps Institution of Oceanography at UC San Diego plans to take
>>accurate readings of ocean temperatures to measure global warming.  They
>>plan to:
>>	" loudspeakers on the ocean floor off Big Sur, CA, and blast
>>	sounds so loud that they could be heard in New Zealand..."

I attended a seminar by a PI on this project last week.  Perhaps
a little background is in order.  There is a minimum in the profile
of sound speed in the ocean at ~1000m depth.  As a result, sounds are
trapped in an "acoustic waveguide" and can travel great distances
relatively unattenuated.  So the sound is not SUPER DEAFENINGLY LOUD
at the source even though it can be heard in New Zealand.  It is 
no louder near the source than a supertanker is, and will turn on 
gradually so mammals can swim away.  

However, the acoustic waveguide is the information superhighway for
marine mammals.  Sound is their ONLY long distance communication; it 
is like vision for us.  While outcry about "deafening the whales" 
is extremist, this experiment is noise pollution on a grand scale.

At the seminar, the sound in question was played for us.  It is a 
throbbing 70Hz hum, probably not interesting or complex enough to 
confuse the sophisitcated ears of marine mammals, but an irritant.

Backers claim the 3% duty cycle (20 minutes every 4 hours every fourth
day) make it a small inconvenience for marine mammals, in exchange for
humans being able to measure 1/20 degree C changes in ocean temperature.

Lastly, don't be fooled by people comparing ocean and air sounds in decibels.  
The decibel is a relative measure, and the reference level is different
in water and in air.  

In summary, this experiment is extremely impolite to our oceanic
cousins and should be stopped, but it is not going to deafen and
kill all whales by any means.  


[=] © 1994 Peter Langston []