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Sonar developments

To: Bioacoustics list <>
Subject: Sonar developments
From: Jim Cummings <>
Date: Wed, 17 Dec 2008 11:13:56 -0700
Two important new developments on the Navy sonar front:

--Final EISs have been released for SOCAL and AFAST (2 of 11 Navy EISs
governing specific offshore ranges, though AFAST covers the entire east
coast).  Both hew to the Navy stance that any spatio/temporal restrictions
would limit their need for total flexibility in training site selection,
while offering insignificant extra protection of animals.  Level A
harassment (TTS, PTS) numbers hardly change for most species when they set
some areas off limits (a couple dolphins are the exceptions); this is likely
because Level A kicks in at 500m or less.  Level B (behavioral disruption)
numbers drop more, but generally only 20-30% (rough estimates, didn¹t yet
take time to analyze in detail)

--A good study of the potential for using passive acoustic detection for
avoiding impacts on beaked whales: bottom line is that it¹s pretty easy to
hear them (via foraging echolocation clicking) when they¹re within 1km,
about 50/50 detection at 1-3km, and pretty much impossible beyond 4km.  Of
course, for the behavioral responses we¹re now mostly concerned about,
that¹s likely not far enough.  Also, the crucial piece is that you have to
listen for over 2 hours to get these levels of detection. So, the listening
platform has to be stationary or moving very slowly, meaning a sonar vessel
is clearly not an effective place to listen from (a point the authors make

These are both featured in more detail in recent posts at
(this site is used to post key news and research summaries; it's in blog
format, largely to facilitate those who want an Acoustic Ecology-oriented
RSS feed)

Jim Cummings
Executive Director, Acoustic Ecology Institute

    Needle clusters shirring in the wind?listen close, the sound gets better
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