Analysis and Ranking of the Acoustic Disturbance Potential of ...

Report No. 6945
BBN Systems and Technologies Corporation
5. SOUND EXPOSURE PREDICTION PROCEDURES AND RESULTS
In this section the information on species distribution is combined with
information on source distribution, source level and transmission loss to
determine the most significant sources in terms of their effective range and
numbers of mammals potentially affected. A procedure for rating the sources
is presented which is based on the amount of sound energy contributed to the
environment in a specific reference area. The source rating is combined with
a receiver (species) rating procedure which includes the degree of matching
between source bandwidth and species hearing response, the species hearing
sensitivity, and the number of animals present in the reference area. The
output of this exposure rating procedure provides a numerical indication of
those source - species encounters which may have the highest potential for
acoustic interaction in a given area. Estimated zones of influence based on
probability of avoidance were determined for potentially high interaction
encounters where response criteria were available.
While much of noise source level and species response rating procedure
involves principles of physical acoustics, it must be emphasized that some of
the rating procedures are based on human psychoacoustic research and incorporate
hypotheses which have not been tested with marine mammals. Moreover, it
has been necessaryto infer and estimate many of the parameter values needed
to develop ratings for several species where data gaps exist. The modeling
procedure which has been developed in this study is offered as a means of
identifying those areas where more information is needed. When the information
becomes available it can be incorporated into the data base to replace
presently inferred or estimated values and help provide better rating results.
The modeling procedure itself can evolve with necessary changes and extensions
when the needed information becomes available.
5.1 Noise Source Distribution*
The distribution of noise sources in the marine and coastal regions of
Alaska was analyzed using the source classification format established in
Section 3. Information on the distribution of petroleum industry sources was
obtained from reports of the MMS OCS Office. Transportation industry source
data were obtained from ship and ferry schedules, port records, and airline
schedules. Fishing industry data bases and reports were reviewed to determine
vessel operating areas. In most cases vessel numbers on specific fishing
grounds were estimated because of a general lack of this type of information
in available reports. Additional information on fishing vessel activity and
on cultural and recreational sources was obtained from the environmental
impact studies and the economic study series of the MMS. The series of final
reports published by the NOAA Outer Continental Shelf Environment Assessment
Program (OCSEAP) was also helpful in providing information on source locations
and estimated numbers. The information obtained from review of documents was
supplemented by telephone interviews when appropriate and by personal
observations made on recent trips to Alaskan coastal areas while working on
other projects.
*D.G. Roseneau, LGL, Alaska, Fairbanks, and C.I. Malme, BBN.
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